Motoring Discussion > Mercedes Benz - 250 - diesel on e-bay,	Miscellaneous
Thread Author: R.P.	Replies: 79

New Thu 1 Jul 10 09:07   Mercedes Benz - 250 - diesel on e-bay, - R.P.

330416919092 Reply to this message | Report message

New Thu 1 Jul 10 10:33   Mercedes Benz - 250 - diesel on e-bay, - Badwolf

I'm sure it's a nice car. Hard to tell though - I think that the seller needs some basic photography lessons... I'd love an old Merc like this one, but it's a bit of a leap of faith for me. Reply to this message | Report message

New Thu 1 Jul 10 10:56   Mercedes Benz - 250 - diesel on e-bay, - Zero

Its a shed. Reply to this message | Report message

New Thu 1 Jul 10 11:11   Mercedes Benz - 250 - diesel on e-bay, - Fenlander

My uncle has a genuine preserved one of these (with a petrol engine).... less than 60k, unmarked, all original and no issues... pretty good for 25yrs old. I would not consider the Ebay one due to the buyers history. 100% positive I know but the items bought/sold tell a tale. Reply to this message | Report message

New Thu 1 Jul 10 16:32   Mercedes Benz - 250 - diesel on e-bay, - Iffy

...It's a shed... What do you expect for £1,000 - a Kew Gardens Orangery? My only worry would be getting good title to the goods. I've bought new goods from companies I've found via ebay, but I am very wary of any private seller of anything. Reply to this message | Report message

New Thu 1 Jul 10 16:37   Mercedes Benz - 250 - diesel on e-bay, - Zero

I expect to buy a shed for shed money. Reply to this message | Report message

New Thu 1 Jul 10 17:10   Mercedes Benz - 250 - diesel on e-bay, - Old Navy

Careful Zero, leaving yourself open to getting Lancer and shed in the same sentence. :-) Reply to this message | Report message

New Thu 1 Jul 10 17:56   Mercedes Benz - 250 - diesel on e-bay, - Mapmaker

Buy a chav car from a chav and expect good kit? A long bargepole for this one. I've bought many thousands of pounds worth of stuff on eBay, probably more from private sellers than trade, and although I've had some disappointments, in general I am well ahead. Moreover, I don't think I'd buy a car from somebody who knows about cars - like this bloke clearly does, as there's a good chance he's patched up a wreck to sell it on. Reply to this message | Report message

New Thu 1 Jul 10 18:27   Mercedes Benz - 250 - diesel on e-bay, - madf

In good condition, it's snail.. Reckon it will need £599 of brakes and steering.. Old Mercedes are not cheap when not regularly maintained.. (BIL's 300D needs a new propshaft bearing £200).. Reply to this message | Report message

New Thu 1 Jul 10 18:39   Mercedes Benz - 250 - diesel on e-bay, - Iffy

What year is this crate? Don't think it says in the ad. Reply to this message | Report message

New Thu 1 Jul 10 11:45   Mercedes Benz - 250 - diesel on e-bay, - jc2

Seen the date on the photos!!!!!!!! Reply to this message | Report message

New Thu 1 Jul 10 11:58   Mercedes Benz - 250 - diesel on e-bay, - Fenlander

Yes... and noticed on another sold item with bad photos the seller said something like *sorry about poor pics, low battery*. Bad pics are a very good cover for tatty goods... I'll never bid unless images are sharp so you can have a fair look at the item. Reply to this message | Report message

New Thu 1 Jul 10 11:13   Mercedes Benz - 250 - diesel on e-bay, - Focusless

>> 330416919092 Now relisted: cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=330443639861 Reply to this message | Report message

New Thu 1 Jul 10 11:20   Mercedes Benz - 250 - diesel on e-bay, - Fenlander

Interesting.... just fits the profile I'd deduced selling off the alloys and putting on some tatty ones. I see in their buyers history it showed 4 no-brand part-worns bought at £15 a pop... looking to be what was on the supposedly good alloys he's just sold out from under it. Reply to this message | Report message

New Thu 1 Jul 10 12:35   Mercedes Benz - 250 - diesel on e-bay, - Mike Hannon

Zero's right. My pal has had a white diesel 250 for about 15 years now - it must have about 250k miles on it and has always been abused, but still sound in wind and limb. Reply to this message | Report message

New Thu 1 Jul 10 12:42   Mercedes Benz - 250 - diesel on e-bay, - Soupytwist

I'd be twitchy about an account name of emma10_00 when the seller is clearly a bloke. As per recent feedback stating "Proper Top Guy!" Last edited by: Soupytwist on Thu 1 Jul 10 at 12:42 Reply to this message | Report message

New Thu 1 Jul 10 22:15   Mercedes Benz - 250 - diesel on e-bay, - Bagpuss

Sad to see another W124 butchered with a boot spoiler and lowered suspension. Reply to this message | Report message

New Thu 1 Jul 10 22:16   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

Why are we looking at this car - is someone thinking of buying it? Reply to this message | Report message

New Thu 1 Jul 10 22:28   Mercedes Benz - 250 - diesel on e-bay, - Bellboy

well the donkeys worth a few bob NC :-) Reply to this message | Report message

New Fri 2 Jul 10 09:30   Mercedes Benz - 250 - diesel on e-bay, - The Nut

>> Why are we looking at this car - is someone thinking of buying it? >> I think most of us on here would run a mile at the mention of lowered suspension. I think it was Number Cruncher who once said something like "why do you think you know more about suspension than the Mercedes engineers?" Reply to this message | Report message

New Fri 2 Jul 10 11:15   Mercedes Benz - 250 - diesel on e-bay, - Old Navy

>> I think it was Number Cruncher who once said something like "why do you think >> you know more about suspension than the Mercedes engineers?" >> There ar certainly a lot of chavs, amature car modifiers and tuners who think they know more than the manufacturers engineers. Last edited by: Old Navy on Fri 2 Jul 10 at 11:16 Reply to this message | Report message

New Fri 2 Jul 10 14:54   Mercedes Benz - 250 - diesel on e-bay, - Tooslow

I was once passed by a newish but tackily modded Golf. On the back windscreen it said "Made in Germany, modified in Blackburn (or some such place)". Says it all really :-) JH Reply to this message | Report message

New Fri 2 Jul 10 15:13   Mercedes Benz - 250 - diesel on e-bay, - Zero

Driven by Richard? Reply to this message | Report message

New Fri 2 Jul 10 15:42   Mercedes Benz - 250 - diesel on e-bay, - madf

"Driven by Richard?" Wayne more likely... Reply to this message | Report message

New Fri 2 Jul 10 15:55   Mercedes Benz - 250 - diesel on e-bay, - The Nut

>> Wayne more likely... >> Mr. W Kerr. Reply to this message | Report message

New Fri 2 Jul 10 20:47   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>> I think most of us on here would run a mile at the mention of >> lowered suspension. Yes, one of the quickest ways to ruin a car in my opinion! >> I think it was Number Cruncher who once said something like "why do you think >> you know more about suspension than the Mercedes engineers?" That was a bit blunt and nasty of me - sorry if I offended anyone. It surprises me how many people modifying cars do, effectively, have the attitude that they know better. Do they think that the engineers in the factory aren't petrolheads too? There are cases where the makers do get it a bit wrong, and an aftermarket can provide a really helpful solution. One case that really leaps to my attention is the weakness in VW Golf mkII lock surrounds - they were really easy to break into, and the door skin would be damaged in the attempt. An aftermarket company produced some hard metal surrounds, in the same finish as the door handle which provided much better protection. However, in my opinion, most "performance" mods are at best ill thought out, and at worst downright dangerous. Here's an example. Fitting larger front brake discs and calipers is a popular modification, but, it generally makes the car take longer to stop from a given speed than the standard set up! However, the modifiers really struggle to accept the truth of this. Reply to this message | Report message

New Fri 2 Jul 10 20:59   Mercedes Benz - 250 - diesel on e-bay, - The Nut

You might have said it better, this is just from memory. But it was someone asking for advice and being unwilling to accept the good advice. Reply to this message | Report message

New Fri 2 Jul 10 21:15   Mercedes Benz - 250 - diesel on e-bay, - Skoda

>> Fitting larger front brake discs and calipers is a popular modification, but, it generally makes the car take longer to stop from a given speed than the standard set up! NC, how does the logic go on this? Thinking aloud: If a car went from 2 single piston calipers at the front, maybe 50mm for example, then they switched to 2x 4 pot calipers with maybe 2x 35mm pistons each side, is it just the increased area of piston faces == lower force exerted on the back of the pad by each piston? If my logics ok so far, then i'm falling apart when i consider that example 1 has less surface area pressing the pad (assuming pressure behind the piston is the same) and so should generate less force? Reply to this message | Report message

New Fri 2 Jul 10 21:22   Mercedes Benz - 250 - diesel on e-bay, - Zero

I would imagine its to do with too much braking force being availble, far more than the size of tyre and rotational speed could impart to the road surface. If is fitted with ABS this must really screw up the way the abs has been set up as well. Last edited by: Zero on Fri 2 Jul 10 at 21:23 Reply to this message | Report message

New Fri 2 Jul 10 21:31   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

To get near the best deceleration the car is capable of, all 4 wheels need to be brought to the point of locking simultaneously. In order to prevent rear axle locking, standard brake bias is already towards the front. i.e., the front axle will lock before the rear - in normal circumstances, the rear axle will never lock. Fitting larger front brakes simply takes the car further away from the ideal situation of all 4 wheels locking together, and the front axle will lock (and hence produce no further effort beyond that due to tyre/road sliding) long before the rear axle is approaching locking. The net result is car that has had a lot of money spent on it, and now can't stop as quickly. A really good and well thought out front brake upgrade kit *won't* produce any extra brake torque per unit force on the pedal, and will thus preserve the vehicle's correct front / rear bias. The well thought out kit would be aimed at providing better cooling and thus less degradation of braking under hard use. Reply to this message | Report message

New Fri 2 Jul 10 21:47   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

NC, most standard brake systems are nowhere near powerful enough to lock the front wheels at speed on a dry road though standard rear brakes may lock as weight transfers to the front. Larger front brakes enable more of the adhesion between tyres and road (coefficient of friction) to be utilised in stopping the vehicle not to mention providing a larger surface area which aids cooling and thus ensures the ideal coefficient of friction between the pad and the disc. Reply to this message | Report message

New Fri 2 Jul 10 21:52   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

Cheddar - No, you've really got the wrong end of the stick. Reply to this message | Report message

New Fri 2 Jul 10 21:55   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

>> Cheddar - No, you've really got the wrong end of the stick. >> Not at all NC, care to rationalise that view then? Reply to this message | Report message

New Fri 2 Jul 10 21:57   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>care to rationalise that view then? Apart from your point about possible improved cooling, everything else in your post is, simply, wrong - sorry. Reply to this message | Report message

New Fri 2 Jul 10 22:00   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

>> Apart from your point about possible improved cooling, everything else in your post is, simply, >> wrong - sorry. >> So you dont care to rationalise that then, apology accepted. Vastly improved cooling in many cases, the rest of my point stands and doies not need repeating. Reply to this message | Report message

New Fri 2 Jul 10 22:02   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>the rest of my point stands No Reply to this message | Report message

New Fri 2 Jul 10 21:54   Mercedes Benz - 250 - diesel on e-bay, - Zero

>> >> NC, most standard brake systems are nowhere near powerful enough to lock the front wheels >> at speed on a dry road though standard rear brakes may lock as weight transfers >> to the front. What? I have been able to, and have locked the fronts up on any non abs car I have since 1979. Reply to this message | Report message

New Fri 2 Jul 10 21:58   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

>> >> What? I have been able to, and have locked the fronts up on any non >> abs car I have since 1979. >> Good tyres and road surface at 60 or 70, no way! A bike with 2 x 320mm discs and 6 piston calipers and a contact patch the size of the palm of your hand will not lock its front wheel in the dry. Reply to this message | Report message

New Fri 2 Jul 10 22:01   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>A bike.... We're talking about cars. The braking on a bike is limited by the deceleration when rear wheel lifts, and the rider goes over the bars. The braking on a car is limited by tyre / road friction. Reply to this message | Report message

New Fri 2 Jul 10 22:55   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

>> >>A bike.... >> >> We're talking about cars. >> Its the same principal. NC, what is happening when the bike’s rear wheel lifts? Weight transference. What is happening when a car brakes hard? Weight transference. In the dry a bike will achieve maximum retardation with the back wheel virtually off the ground. In the dry a car will achieve maximum retardation with very little rear wheel braking due to weight transference. If the front braking efficiency is increased the amount of rear braking is correspondingly reduced due to increased weight transference though the overall efficiency increases until the adhesion limit of the front tyres is achieved. Hence improved brakes usually go hand in hand with improved (larger) tyres. Reply to this message | Report message

New Fri 2 Jul 10 23:09   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

>> >> The braking on a bike is limited by the deceleration when rear wheel lifts, and >> the rider goes over the bars. >> By the way you could tug the front brake as hard as you like at say 100mph on any modern superbike with truly awesome brakes and you would not go over the bars, not unless you eased off the brakes at around 30 or 40 mph, it is to do with the power of the brakes relative to the job in hand (trying to think of the technical jargon*), likewise the front wheels on a car will not lock at 100mph though might do at 20. Reply to this message | Report message

New Fri 2 Jul 10 23:29   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

Yes, bikes and cars both have weight transfer - that's true, but not directly relevant. But, the difference between bike and car is still massive. A bike has a much higher ratio of height of c of g to wheelbase, and hence has much more weight transfer than a car. When did you last see a car pick its rear wheel up under braking alone? The braking of a bike is limited by the rear wheel lifting - at that point, further braking is very dangerous, and beyond the tipping point, catastrophic. You can't squeeze as hard as you like - the truth is no-one's actually daft enough to try that at 100 mph! The braking of a car is limited by tyre / road adhesion, and despite weight transfer, the front axle always locks up first - by design. There's also a misconception about road speed being important to the friction between the tyre and the road - it's not massively sensitive, but, there's actually a small *reduction* in the coefficient of friction between the tyre and the road as speed increases. [Lechner & Naunheimer - Automotive Transmissions] Reply to this message | Report message

New Fri 2 Jul 10 23:38   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

Here's why your post above was so badly wrong. >>NC, most standard brake systems are nowhere near powerful enough to lock the front wheels at speed on a dry road That bit is simply not true - there's no extra explanation for me to give there. >>though standard rear brakes may lock as weight transfers to the front. No, never. All cars are designed, by law, [there's an ECE regulation for it - I can't remember the number, but, I'm sure I posted it on another site we all know] for the front axle to lock first. Rear locking is specifically prevented by the use of devices like pressure reducing valves or G valves, or load sensing valves. Rear locking on a bike is reasonably benign, while on a car, it's very dangerous - the dynamics of the situation *are* different. On a bike, it is front locking which is more dangerous, where on a car, front locking is quite easy to deal with. >>Larger front brakes enable more of the adhesion between tyres and road (coefficient of friction) to be utilised in stopping the vehicle No, larger front brakes actually allow less of the available adhesion to be utilised, and this is my very point, it's the thing that many modifiers simply get wrong, or don't think about enough. >> not to mention providing a larger surface area which aids cooling and thus ensures the ideal coefficient of friction between the pad and the disc. Here, I agree. Reply to this message | Report message

New Sat 3 Jul 10 07:06   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

>> >>NC, most standard brake systems are nowhere near powerful enough to lock the front wheels at speed on a dry road >> >> That bit is simply not true - >> I think you would find it is true, good tyres, good road surface, high speed, no abs, slam them on, they would not immediately lock, they might once the vehicle has got down to a much lower speed if heat build up had not by then depleated the braking efficiency, something that used to be a major problem with smaller non-vented brakes. I had a Dolomite Sprint, despite being a light car I could induce brake fade very easily and to anyone who has not experienced it it can be very scary. Guess what, larger, vented front brakes were a major improvement on Sprints. >> No, never. .......... Rear locking is specifically prevented by >> the use of devices like pressure reducing valves or G valves, or load sensing valves. >> Yes and some are very crude and dont work well and some are affected by pitching supension on uneven surfaces etc, rear locking happens. >> Rear locking on a bike is reasonably benign, >> On a bike as long as the rear wheel is in contact with the road, even if massively unloaded, then it provides directional stability though if it locks then it can be very dangerous particularly if the bike is braking in anything less than a straight line. >> >> No, larger front brakes actually allow less of the available adhesion to be utilised, >> That is simply not true, and you are not explaining why you think that is the case, if standard front brakes cannot get the front tyres near to locking point at high speed then larger / more powerful front brakes can get closer to the locking point and therefore fully utilise the available adhesion. Furthermore if the tyre contact patch is also increased so there is more adhesion then more powerful brakes provide a greater benefit. >> it's the thing that many modifiers simply get wrong, or don't think about enough. >> There are right ways and wrong ways to do it though to simply say that larger brakes reduce the braking performance is wrooooooooong. The key point is why will a wheel lock at low speed and not at high speed, I cannot fully remember the technicalities though it is to do with the brake's ability to turn kinetic energy into heat and to disipate that heat. Neverthless you could, and some people have (though I would be too scared to try it) pull the front brake of a modern superbike as hard as you like at 100mph though try it at 20 or 30 and it will lock up or throw you over the top. The same principal applies to a car where like a bike the front brakes are trying to rotate the vehicle around the line of the front axle, hit the brakes as hard as you like at 100mph and the brakes will only be eble to generate and disapate a certain amount of heat so the wheels wont lock though try it at 20 or 30 and it will lock up. Reply to this message | Report message

New Sat 3 Jul 10 11:01   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

Cheddar, as ever, I would have been better off banging my head against a wall than trying to explain anything to you. Bluntly put, you're completely wrong, and you simply don't know what you're talking about. I have explained the mechanism at work in all its detail - I have even provided a reference where you can go and check the truth of what I've said. Referring back to the old place, you'll find posts by Aprilia where he and I work through the mathematics of ultimate braking decelerations by different methods, where we end up in complete agreement. If you really want to find out more, please go and read some real engineering books on the subject rather than the nonsense in most car and bike magazines. Reply to this message | Report message

New Sat 3 Jul 10 13:36   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

NC, you often (and sometimes extremely usefully) come up with all sorts of scientific based info that is of great interest to many. On other occasions you come up with complete tosh that some perhaps beleive based on you exalted reputation. As I said before to say that larger brakes reduce the braking performance is wrong, period. Reply to this message | Report message

New Sat 3 Jul 10 15:12   Mercedes Benz - 250 - diesel on e-bay, - Iffy

...to say that larger brakes reduce the braking performance is wrong, period... Maybe so, but I do know bigger wheels make the car go faster. Reply to this message | Report message

New Sat 3 Jul 10 15:17   Mercedes Benz - 250 - diesel on e-bay, - swiss tony

>> ...to say that larger brakes reduce the braking performance is wrong, period... >> >> Maybe so, but I do know bigger wheels make the car go faster. >> No no no..... your getting confused, bigger wheels equals better handling, to go faster you need tacky stripes, or even better a naff paint job! Reply to this message | Report message

New Sat 3 Jul 10 17:25   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>As I said before to say that larger brakes reduce the braking performance is wrong, period. Clearly you need to misquote me to attempt to make your point. What I have said is that oversizing the front brakes, as is frequently done in a misguided performance modification, actually reduces the deceleration the car is capable of. Your posts on this particular subject are really badly wrong, but, I suspect you'll struggle to accept that. Reply to this message | Report message

New Sun 4 Jul 10 08:58   Mercedes Benz - 250 - diesel on e-bay, - Hard Cheese

>> Your posts on this particular subject are really badly wrong, but, I suspect you'll struggle to accept that. >> To the contrary, for instance you said "Rear locking on a bike is reasonably benign" when it is in fact potentially lethal for the reasons I have explained above. Additionally your original explanation is flawed. Think about weight transference and the affect it has on front to rear balance. The example of a bike with its rear wheel off the ground is extreme though the principal is the same for a car. Last edited by: Cheddar on Sun 4 Jul 10 at 08:59 Reply to this message | Report message

New Sun 4 Jul 10 12:46   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>Additionally your original explanation is flawed. It isn't, because it already includes that effect - cars are already designed with front brakes which provide more braking than the static weight distribution would indicate. You have failed to understand the point. >>Rear locking on a bike is reasonably benign By that, I meant in comparison with front locking on a bike which is very difficult to recover from - with rear locking on a bike, there is at least more than a slim chance of recovery. I'm not suggesting that rear locking on a bike is completely safe. Next time, I shall simply stick to my line of not bothering trying to explain technical things to you, banging my head against a wall would be more productive. Reply to this message | Report message

New Sat 3 Jul 10 16:43   Mercedes Benz - 250 - diesel on e-bay, - bathtub tom

>>When did you last see a car pick its rear wheel up under braking alone? When I had one of these NC, but does it really count as a car? Moggie Minor 7" front drums and 8" wheels. microcarmuseum.com/tour/scootacar1.html Reply to this message | Report message

New Sat 3 Jul 10 17:27   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>but does it really count as a car? That's style that is BT - looks like good fun too! Reply to this message | Report message

New Fri 2 Jul 10 22:02   Mercedes Benz - 250 - diesel on e-bay, - Zero

Yes every way. Every company car I have had soince 1979, after a few hundred miles to bed in the pads, I had a routine to give it a full brake test, just so I knew how it behaved in panic situations. Thats 60mph, straight wide road and stamp on the brakes HARD. *EVERY* time the fronts locked. How did I know? 4 stripes on the road, and no steering. Couldnt do it after my first ABS car in 95. So let me see, thats 7 cars. Reply to this message | Report message

New Fri 2 Jul 10 22:10   Mercedes Benz - 250 - diesel on e-bay, - Skoda

>> Thats 60mph, straight wide road and stamp on the brakes HARD. Do it like: 0.0 secs to 0.2 secs = gentle pressure, enough to bring all the pads into contact with the discs, they all prime in slightly different amount of time 0.2 secs to whenever = apply more pressure, quickly but smoothly, in practice i've found you'll get shorter stopping distance if you apply slower but progressively harder, than if you over cook the pressure too soon. == you better brace well against the footrest, you *will* come out of your seat and you just wont be able to break traction till well under 30mph It's all good fun Reply to this message | Report message

New Fri 2 Jul 10 22:17   Mercedes Benz - 250 - diesel on e-bay, - Zero

It wasnt an atempt to brake properly, it was to recreate on the edge out of control situations. Any way its much more fun to slide down the road, sometimes ending up sideways. The best part is whent he cloud of acrid stinking tyre smoke catches up with you and glides past. Reply to this message | Report message

New Fri 2 Jul 10 22:25   Mercedes Benz - 250 - diesel on e-bay, - Skoda

>> Any way its much more fun Hmmm, depends whether she's wearing a closed or open necked top in the passenger seat... Reply to this message | Report message

New Fri 2 Jul 10 22:05   Mercedes Benz - 250 - diesel on e-bay, - Skoda

>> What? I have been able to Aye if you whack the pedal sharply :-P Reply to this message | Report message

New Fri 2 Jul 10 21:58   Mercedes Benz - 250 - diesel on e-bay, - Skoda

Ahhh i follow the idea here. Cheers for that NC. Reply to this message | Report message

New Fri 2 Jul 10 23:57   Mercedes Benz - 250 - diesel on e-bay, - Bellboy

i learnt about vehicle dynamics as a 12 year old kid i built my first trolley with small wheels and my second trolley with large wheels i learnt that the smaller wheels made the cart just as fast and i could fit a braking system that worked i never went back to the large spoked wheels and was never outrun on the large hill where i lived Reply to this message | Report message

New Sat 3 Jul 10 00:14   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>i built my first trolley ... Did you ever see or hear of anyone have their feet come off the bar and have their legs dragged under? My father said this was a real danger, and so forbad me from making one, so this was a vital bit of engineering education I missed! Reply to this message | Report message

New Sat 3 Jul 10 00:19   Mercedes Benz - 250 - diesel on e-bay, - Bellboy

my brother came of his and was a mess first time down the hill i realised feet first was dangerous so i designed mine with a steering wheel (an atki i think that i borrowed of a dumped truck) and washing line to the bar it worked really well but like any modern car if you put it on full lock it stuck there and could cause an accident we didnt even have a bib and brace so my bar hole was made with a red hot poker Reply to this message | Report message

New Sat 3 Jul 10 00:38   Mercedes Benz - 250 - diesel on e-bay, - Lygonos

**Warning - Thread Drift Imminent** For the delectation of N_C and any other engineers out there... Here's a nice 'upgrade' for your low spec MG ZR - how to fit big brakes from a 620Ti... Just a little grinding of the carriers required... forums.mg-rover.org/showthread.php?t=287336 Amazing... ...ly stupid. Reply to this message | Report message

New Sat 3 Jul 10 07:30   Mercedes Benz - 250 - diesel on e-bay, - madf

"What? I have been able to, and have locked the fronts up on any non >> abs car I have since 1979. >> Good tyres and road surface at 60 or 70, no way!" Hmm.. In emergency motorway stops from 70 I have locked front wheels in an XJ6, Granada and a Fiesta - all without ABS. Nuff said. Reply to this message | Report message

New Sat 3 Jul 10 08:32   Mercedes Benz - 250 - diesel on e-bay, - Old Navy

>> Hmm.. In emergency motorway stops from 70 I have locked front wheels in an XJ6, >> Granada and a Fiesta - all without ABS. >> Sounds like superb planning and anticipation. Reply to this message | Report message

New Sun 4 Jul 10 09:20   Mercedes Benz - 250 - diesel on e-bay, - madf

"Sounds like superb planning and anticipation." :-) Well as I had driven over 250,000 miles in that period, a few bits of brake locking pre ABS was inevitable... Reply to this message | Report message

New Sat 3 Jul 10 17:45   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>> Amazing... >> >> ...ly stupid. Yes, that's exactly the sort of ill considered, and in that case rather dangerous modification I was thinking of. I wonder if he actually told his insurance company that he took an angle grinder to the safety critical part which reacts the braking force produced by the pad? I suspect not! Yes, the pedal feel is different, the relationship between pedal force and deceleration will change, and, without actually bothering to measure the deceleration, the fellow thinks he has made his car stop better - in fact, he almost certainly has made it stop slower. Reply to this message | Report message

New Sat 3 Jul 10 20:53   Mercedes Benz - 250 - diesel on e-bay, - Lygonos

The most critical part of maximal deceleration is the tyre/tarmac interface. The benefit of 'bigger' brakes is less fade. Generally any feeling of 'faster stopping' is illusionary - possibly there will be less pedal effort required to achieve the same partial deceleration, but maximal braking is still limited by the tyres. - I assume we've all driven 1980s French cars and thought "Wow! These brakes are amazing" only to find they were over-servoed and when an emergency stop was required they were no better than anything else. Illusionary great brakes. If you want better brakes, first get better tyres. A bike won't 'endo' at 100mph because the kinetic energy of bike and rider is a function of the speed squared - thus when the brakes/tyres are at full effect (basically just as the tyre is about to skid) there is a slower absolute rate of deceleration, than at 50mph where the vehicle has only 1/4 of the kinetic energy. Whether you go over the handlebars or not depends upon how quickly you scrub off mph (ie. deceleration) - this happens faster at lower speeds. It's not rocket science... Last edited by: Lygonos on Sat 3 Jul 10 at 20:56 Reply to this message | Report message

New Sat 3 Jul 10 21:12   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

L, I agree fully with the first part of your post, but, the second part, about speed dependence, I can't agree with. From Newton's Second Law, F=ma - > a = F/m The force that the brake pads can apply to the disc, and hence the braking torque, and hence the braking effort at the tyre / road interface isn't (particularly) speed dependent, therefore, the deceleration isn't speed dependent, and endos are just as possible at 100 mph as they are at 10 mph. To decide whether an endo is or isn't possible, it's a question of taking moments about the front tyre's contact point - there's nothing in those equations with "v" in there. Have I misunderstood your point? Reply to this message | Report message

New Sat 3 Jul 10 21:46   Mercedes Benz - 250 - diesel on e-bay, - Lygonos

The maximum force that can be exerted is limited to a degree by the amount of heat/energy that can be dissipated by the brakes/tyres - there is a limit to the ability of friction material to generate heat so F=ma is limited by this. If it was as simple as F=ma then deceleration would be linear. It isn't - most vehicles don't take as long to slow from 30 to 0mph as they do from 100 to 70. Add in tyre voodoo, and wind resistance to the formula and the equations become a bit of a mish-mash. Reply to this message | Report message

New Sat 3 Jul 10 22:06   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>It isn't The plots of deceleration versus time from a fast stop with constant pedal force are quite interesting. The deceleration reaches a peak soon after brake application, then, there's a slight dip as the brakes heat up, then the brake force rises again as the brake cools, reaching another peak as dynamic friction gives way to static friction as the car lurches to a stop. The thermal effects don't really affect the brake force until some way into the stop - the depth of the mid-stop dip is rather dependent upon brake design. Tyre voodoo is an interesting point - as I mentioned above, the effective co-efficient of friction is actually lower at speed. As for which axle locks up, air resistance isn't a massive contributor - the moment arm is quite short between the height of the centre of pressure and the height of the c of g, so, there's not much moment when compared with the pitching moment caused by weight transfer. Reply to this message | Report message

New Sat 3 Jul 10 21:18   Mercedes Benz - 250 - diesel on e-bay, - Fenlander

>>>> I assume we've all driven 1980s French cars and thought "Wow! These brakes are amazing" only to find they were over-servoed and when an emergency stop was required they were no better than anything else. Illusionary great brakes. Ahh not quite that simple. When a hard stop is required on a car with average or poor brakes a great deal of the potential stopping distance can be wasted with moderate braking in the initial few seconds. With brakes such as the Citroen BX which were very effective (not over-servo'd) you would be more likely to haul off a lot of speed in the initial part of the stopping distance often enabling the pedal to be feathered in the last part as the emergency had already been avoided. They also had the benefit of the ultimate rear brake load sensing system so the distribution was excellent. Emergency brake assist takes this very effective braking one step further. Last edited by: Fenlander on Sat 3 Jul 10 at 21:20 Reply to this message | Report message

New Sat 3 Jul 10 21:51   Mercedes Benz - 250 - diesel on e-bay, - Lygonos

>> When a hard stop is required on a car with average or poor brakes a great deal of the potential stopping distance can be wasted with moderate braking in the initial few seconds. << This doesn't really have anything to do with 'bigger brakes stop you faster', it's more to do with driver ability. Reply to this message | Report message

New Sat 3 Jul 10 22:57   Mercedes Benz - 250 - diesel on e-bay, - Fenlander

>>>This doesn't really have anything to do with 'bigger brakes stop you faster', it's more to do with driver ability. Ohh quite... and very valid as the drivers foot on the pedal is *the* major factor in braking. Reply to this message | Report message

New Sat 3 Jul 10 22:06   Mercedes Benz - 250 - diesel on e-bay, - -

I'll throw a little bit in here if i may, not with any egineering expertise but a feel for the road and many miles on it, like many here. In perfect road conditions and otherwise perfectly maintained cars then increasing front braking performance especially if it as likely includes extra cooling can provide better 'feeling' brakes, lighter effort possibly required for a given braking rate. However once perfection is lost either due to wet/slippery roads or deteriorating brakes..wear and tear, scored discs drums etc then the fact the front will be overbraked in comparison to the rear (still in it's designed condition) will lead as NC says to premature front wheel locking without the rear brakes having reached anywhere near their potential stopping power. I found this out many years ago when i replaced the original very hard brake pads on the front of a Mk2 Golf Diesel...fitted with same pads as GTi model as many Diesel cars were similarly heavier braked than equivalent petrol models. The originals were chewing up the discs and required a hefty pedal pressure to stop the car, which was very low mileage at the time. I put Feroda pads on which were a lovely soft compound, providing a light pedal and considerable stopping power. In the dry great, in the wet it made them prone to prermature front lock up. So i had to replace the rear shoes with Ferodo's too to reaquire the correct brake balance. In effect i'd increased the front braking power as much as if i'd fitted larger brakes, and had to compensate. Reply to this message | Report message

New Sat 3 Jul 10 22:19   Mercedes Benz - 250 - diesel on e-bay, - Lygonos

>>> As for which axle locks up, air resistance isn't a massive contributor - the moment arm is quite short between the height of the centre of pressure and the height of the c of g<<< The exception..... www.streetracersonline.com/gallery/albums/userpics/14518/ricer.jpg 8-) Reply to this message | Report message

New Sat 3 Jul 10 22:20   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

>>www.streetracersonline.com/gallery/albums/userpics/14518/ricer.jpg Ha ha! Last edited by: Number_Cruncher on Sat 3 Jul 10 at 22:21 Reply to this message | Report message

New Sat 3 Jul 10 22:20   Mercedes Benz - 250 - diesel on e-bay, - Number_Cruncher

Interesting points GB - these days, replacement pads should, ideally, meet ECE R90, which means their co-efficient of friction must be within a given tolerance of the original parts, and sample parts must be tested for compliance in this regard before the parts can be marked up with the ECE markings. Reply to this message | Report message

New Sat 3 Jul 10 23:38   Mercedes Benz - 250 - diesel on e-bay, - Skoda

>>> these days, replacement pads should, ideally, meet ECE R90 Ahh this all explains why super effective DS2500's are not ECE R90'd then Reply to this message | Report message

New Sat 3 Jul 10 22:15   Mercedes Benz - 250 - diesel on e-bay, - Boxsterboy

>> Ahh not quite that simple. With brakes such as the Citroen BX >> which were very effective (not over-servo'd) >> The BX also had light weight on its side - not something that can be said for the vast majority of today's cars. Yes, it made the car feel a bit tinny, but I would rather have a tinny feel and excellent brakes, rather than a heavy car with average brakes any day. Reply to this message | Report message