I've removed many brake discs in my time and sometimes they fall away quite easily.
However, there are times when a bit of force is needed and I usually use a few hammer blows at the back of the disc, rotating the disc by about 90 degrees between blows.
Some say that this can damage the wheel bearings. Has anyone ever had a wheel bearing failure as a result of this? How do others persuade discs to come off? Some recommend a bit of heat but I don't have oxyacet so it isn't really practical.
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i,ve removed thousands of discs(city and guilds and time served!) like this Chris, some using considerably more force than that and never damaged a bearing.
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Likewise, never heard that it can damage bearings.
I thought the reason behind not using a hammer (a metal one, that is) was due to risk of the disk shattering and the metal fragments ending up in your eyes.
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You can damage bearings doing this, the blows can cause minute indentations in the outer race, though i too have had to resort to brute force before now.
Most discs and drums have threaded holes that you can insert two (usually 2 holes opposite) suitable bolts, tighten gradually and with a bit of gentle persuation they usually come free, or a suitable hub puller.
Here we go....when i check my cars over i usually clean up the hub and put some coppaslip at the disc inner edge where it meets the hub with a paint brush, this does seem to help prevent rust building up at that point, same with rear drums.
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GB is quite right about bearing damage being possible.
I have done it myself - which was when the penny dropped. Front discs on SWMBO's mk3 Astra.
Like many, it's a practice I had used for many years in workshops, before I knew any better.
If you're scrapping the disc anyway, a judicious cut with a hacksaw or cutting wheel is much more gentle.
I don't go along with GB's suggestions of copperslip use though!.....
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>> I don't go along with GB's suggestions of copperslip use though!.....
Why NC?
I don't go plastering it on, just enough to stop salt ingress really.
I've kept an eye on the stuff, and it's never shown signs of melting or spreading.
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I'm a bit twitchy about anything that can help slippage within the bolted joint between the hub and the wheel, although I can see the practical benefit of keeping rust out.
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OK, fair comment, bit of damned if you do or don't, no coppaslip and the alloy wheel gets corroded on, resulting in that being wellied off too.;)
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OK, fair comment, bit of damned if you do or don't,...
Yes, that's fair to say.
I did some rough calcs which showed that under emergency stop conditions, the effective clutch face you have between the wheel and the hub can begin to slip if you apply copperslip.
I suspect it's a different way to regard wheel bolts from the norm, but, from an engineering "machine elements" point of view, the bolts are acting as springs, pulling together the "clutch" faces of the wheel and hub. The wheel is centred on the spigot, and the torque transmitted from hub to wheel is effectively just like a clutch.
If the friction is no longer transmitting the torque, then the bolts are doing the job, they are being bent and subjected to shear loadings for which they were not designed.
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There's a fair old bit to this engineering lark.:-)
Food for thought there, and i for one would never have given this clutch effect a thought.
Under emergency braking conditions i imagine the loads at hub or wheel bolt level must be astronomical.
I can only comment from my experiences of driving, and most of that from trucks.
I've found in my work that the most violent stops were those at town speeds where the stop would be almost instantaneous at say 20mph, that's the stop where an unsecured load isn't stopping**, but a 60mph full brake wouldn't be anywhere near as sudden, brakes starting to fade out when down to to 25mph or so.
Is that a correct assumption or is it an illusion.
** a mate had the unusual happen to him in such a low speed panic stop, the car over the cab peak wasn't loose, but the hinged part of the deck 'flipped over' so he ended up with a Vectra dangling from the front wheels just over the cab and the whole of the under side hanging down in front of the cab, from a 50mph panic stop that wouldn't have happened imo, not enough instant shock brake effect.
Being a belt and braces bore, i had already jerry rigged my identical vehicle's peak deck to prevent that happening, tbh it should have been secured at manufacture stage and was such an easy fix at that point, a simple piece of angle iron on top of the release bolts as well as under, 20 mins and 2 x 3" pieces of angle would have done the trick.
Strange oversight really as the rest of the vehicle was versatile to the nth degree, tough and durable.
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Thank you for all your interesting comments.
The Panda 4x4 might not have threaded holes in the disc, it has holes but these are for disc retaining bolts and are not threaded.
It has just come into my head that some folk remove the wheels and any disc retaining bolts and stamp on the brakes whilst the car is in gear. I have not brought that idea up as the non-selectable Panda 4x4 system would require all four corners of the car to be jacked up for this to work and that's just not safe at home.
I shall have to give all your ideas some consideration.
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>>Is that a correct assumption or is it an illusion.
If you apply a constant pressure to a brake cylinder / actuator, and monitor the brake torque as the vehicle stops from speed, you see an initial peak in torque which then reduces as some heat gets into the linings. Then as the wheel slows, the torque rises again, peaking just before the wheel stops rotating - partly explained by static friction being higher than dynamic friction.
As a further aside, this variation of friction with speed is one of the many candidate explanations for brake squeal and clutch judder.
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>>a few hammer blows at the back of the disc, rotating the disc by about 90 degrees between blows.
Only if you've no intention of re-using the disc.
I've experienced some heavy brake pedal pulsing as a result of this.
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No intention of re-using the discs. The reason for removing them is that they are heavily corroded so that braking is impaired and they would fail the MOT.
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FIAT Panda 4x4 - 08 1.3 Removal of Discs - matt a
