Non-motoring > Push-bike pedal crank loose Miscellaneous
Thread Author: bathtub tom Replies: 17
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 Tue 28 May 13 15:06 
 Push-bike pedal crank loose - bathtub tom
My old bike has a loose pedal crank.

It's a square, tapered crankshaft(?) the crank pushes on to and is held by a machine screw with a wide shoulder. This should give you the idea: www.ebay.co.uk/itm/Left-Hand-Crank-Arm-for-Cycle-Bike-Alloy-Black-or-Silver-All-Sizes-NEW-/120809491729

I guess I've been remiss in keeping it tight, resulting in the hole in the pedal crank opening up. The crankshaft now protrudes beyond the start of the threaded section in the crank, rendering the machine screw ineffective.

I've tried shimming the gap, but the most I can get in there is some wire which has proved ineffective.

I've thought of grinding down the end of the crankshaft.

Any suggestions, before I get drastic and, heaven forbid, buy a new crank?
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 Tue 28 May 13 15:29 
 Push-bike pedal crank loose - Cliff Pope
Been there, long ago.

I tried several options, but can't remember which worked best:

1) Cut a bit of tinplate to wedge down one or two flats of the taper
2) Find washer or two with a big hole that will just fit over the protruding end of the crank, and then use a big washer with a hole the size of the screw.
3) Grind the end of the crank
4) Build up a bit of weld on the taper and grind it true again, but thicker.
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 Tue 28 May 13 15:29 
 Push-bike pedal crank loose - Armel Coussine
They weren't like that when I were a nipper. Round crank pin with a flat machined in it, pedal crank located by a round cotter with tapered flat, tightened with a nut.

You could assemble it the wrong way round so that the pedals weren't 180 degrees apart, and you could strip the thread on the cotter pin through youthful insensitivity. I imagine all those parts are still available in bike shops.
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 Tue 28 May 13 15:32 
 Push-bike pedal crank loose - Cliff Pope
I remember them AC. Different system though.
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 Tue 28 May 13 15:35 
 Push-bike pedal crank loose - Slidingpillar
I'm having a bit of difficulty visualising this despite being familiar with cotterless cranks for over 35 years.

The crankshaft is the hard bit though, so you'll have worn/eroded the softer crank. And as such, I think you need a new crank - sorry. If you shorten the shaft, the crank may hit the rear forks, they don't miss by much.

The pedal/crankshaft joint is a highly stressed one and not the kind of thing that will be amenable to bodges.
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 Tue 28 May 13 15:51 
 Push-bike pedal crank loose - Runfer D'Hills
I'd just fit a new crank. Not worth the faff.

(Or if the cost is too disturbing, you could always fashion a toe clip for the other side out of recycled cable ties and just use the one foot.)

:-)
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 Tue 28 May 13 18:13 
 Push-bike pedal crank loose - hawkeye
I agree with Humph. £2.50 upwards post paid from Ebay.
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 Tue 28 May 13 18:44 
 Push-bike pedal crank loose - Bromptonaut
Another vote for a new crank. Not worth messing with bodges that might let you down miles from home/help.

While you're at it make sure the other one is OK and if necessary overhaul the bottom bracket (crankshaft) or replace with new sealed unit if not serviceable.
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 Tue 28 May 13 19:03 
 Push-bike pedal crank loose - Robin O'Reliant
And make sure you get the correct crank length and taper size. Cranks for road bikes come in 170, 172.5 and 175mm lengths (Measured centre to centre from taper to pedal spindle), you won't want different on each side. Unless the axle is a Campagnolo brand you will need a JIS (Japanese Industry Standard) taper. Shouldn't be a worry there as most are, but check.
Last edited by: Robin Regal on Tue 28 May 13 at 19:06
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 Tue 28 May 13 21:20 
 Push-bike pedal crank loose - bathtub tom
>> Cranks for road bikes come in 170, 172.5 and 175mm lengths

How on earth am I to accurately measure that when the things got a dog-leg in it?

>>£2.50 upwards post paid from Ebay.

I found them from around a tenner, where did you see those?
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 Tue 28 May 13 21:44 
 Push-bike pedal crank loose - Runfer D'Hills
Take the crank to a decent indy bike shop Tom. They'll sort you out and while you'll maybe get what you need a bit cheaper elsewhere they'll likely not be ruinously expensive and they'll give you the correct part.
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 Wed 29 May 13 00:26 
 Push-bike pedal crank loose - bathtub tom
>>Take the crank to a decent indy bike shop

I was at one t'other day, buying another half-a-dozen spokes (must lose weight). Should've asked then.
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 Wed 29 May 13 00:38 
 Push-bike pedal crank loose - Fullchat
You may need some special tools for removing crank and pedal parts. I have this kit I got for a one off job. But now Mrs FC is getting big into biking and training for triathalons it may get some more use. I'll drive the service vehicle :)

www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_522915_langId_-1_categoryId_242558

Note the lack of a hammer.

So in the long run it may be easier/cheaper to see a specialist.
Last edited by: Fullchat on Wed 29 May 13 at 00:39
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 Wed 29 May 13 09:20 
 Push-bike pedal crank loose - Bromptonaut
Crank extractor tool on it's own looks likle this:

www.chainreactioncycles.com/Models.aspx?ModelID=10181

Use with care. It's easy to cross thread as you screw it into the crank or to fail to screw it in to its full extent. In either case you're likley to ruin the crank.
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 Wed 29 May 13 09:40 
 Push-bike pedal crank loose - sherlock47
www.chainreactioncycles.com/Models.aspx?ModelID=10181

Looking at all those specialist tools I think that I should get into cycling:)

I remember when all you needed for a bike was an adjustable spanner, hammer and 2 spoons.
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 Wed 29 May 13 10:14 
 Push-bike pedal crank loose - Runfer D'Hills
When I'm off road on't tread iron I take a multi tool ( mainly various allen keys, with an additional phillips and a flat ) a flat bike spanner, a couple of cable ties ( amazing what can be bodged with cable ties ) a fold up pump and a spare inner tube. Covers most eventualities. You don't need the spoons or posh equivalents with MTBs. The tyres just peel on and off easily when deflated. All that and a cable lock fit in a little pouch under my saddle.
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 Wed 29 May 13 18:05 
 Push-bike pedal crank loose - Biggles aka B_i_G
This kit does include a hammer but is a bit more pricey though.
www.chainreactioncycles.com/Models.aspx?ModelID=50270

Seriously, the cheap Halfords kit is about as useful as an adjustable spanner and hammer. Most of the tools look like they are for previous generations of equipment, e.g. cone spanners and headset tools.
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 Wed 29 May 13 18:27 
 Push-bike pedal crank loose - bathtub tom
>>This kit does include a hammer but is a bit more pricey though.

Good grief! That's more than three times the price I paid for the bike around a dozen years ago.
Last edited by: bathtub tom on Wed 29 May 13 at 18:27
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