Author Topic: Brompton folding pedal repair howto  (Read 14180 times)

Brompton folding pedal repair howto
« on: September 05, 2009, 06:48:18 pm »
The Brompton left-hand pedal uses a standard 62032 cartridge bearing, which is a single-row, deep groove type.  As an engineering solution this is pretty rubbish, since this type of bearing *hates* a bending load and all other pedals have two rows of bearings to support the cantilevered pedal body, but it's how the pedal folds with such little projection and we're stuck with it.  Anyway, the bearings don't last very long under hard use.

The problem comes when you have a good pedal - i.e. one that hasn't fragmented from being struck on a kerb - but a shot bearing.  You can't just knock out the old bearing and press a new one in, because the plate that carries the bearing has a retaining lip machined after the bearing (a Russian one of unknown quality) is fitted at the factory.  This stops the pedal body falling off the bearing, I suppose, but means you either have to (a) buy a new pedal for £35 or (b) buy the carrier plate for an outrageous £20, and fit it yourself - which looks rather tricky.

So, with nothing to lose, I filed off the retaining lip.  This is really easy to do because the plate is aluminium and the old bearing is steel - so you know as soon as you've gone far enough and it's virtually impossible to go too far.

Next, the old bearing can be whacked out from behind.  Use a socket as a drift to avoid marking the bore.  As long as the whole bearing comes out, it doesn't matter in what state it ends up, because it's going straight in the bin.  It will require quite astonishing force to shift it if it's been there for a few years.

Now you can clean up your filing with some fine abrasive paper, rounding off the new ridge around the bearing bore so it looks nice and there is no remaining swarf to impede the new bearing.

Finally, take your new bearing (all of £3.69 for a best quality SKF one - you can get a stainless one for £10 if you like, but they're not as robust).  Clean the bore and the outside of the bearing with meths, let it dry and then coat both with Loctite #271 bearing fit.  Then simply smack the bearing into the pedal using a block of wood to avoid damage, ensuring it starts square.  Because the bearing will finish perfectly flush with the body (assuming you didn't overdo it with the abrasive paper) there is no need to use the old bearing to seat it.  Allow the Loctite to cure before riding.

It remains to be seen whether the pedal body will work loose.  Given how hard it was to shift the old one and the use of Loctite, I very much doubt it, but if it does then a large washer held by four screws (drill and tap the plate) would retain it mechanically.  Future bearing changes are, of course, trivially easy now.
Never tell me the odds.

Re: Brompton folding pedal repair howto
« Reply #1 on: September 06, 2009, 03:08:47 pm »
Update: it has survived its first ride (about half an hour) with no movement.
Never tell me the odds.

Re: Brompton folding pedal repair howto
« Reply #2 on: September 06, 2009, 03:46:42 pm »
Interesting.  I think mine died after about 500 miles, and I just put SPDs on the bike and sod that it sticks out slightly (through not folding).

I may have the old pedal somewhere in a box, I wouldn't normally chuck something like that out, but sod's law dictates that in this case I will have. :-\
Actually, it is rocket science.
 

Re: Brompton folding pedal repair howto
« Reply #3 on: September 06, 2009, 06:09:01 pm »
It has to be worth a whirl for £3.69 (and even if you wreck it, you would have had to buy a new £20 bearing assembly anyway).

I've just been out and stamped on it for another 15 minutes with no sign of movement.  I think the job's a good 'un.  To  add weight to this, the newish example I have in the garage shows that, after a fair few miles, the bearing doesn't actually butt up against the "lip", so the lip isn't doing anything.
Never tell me the odds.

Re: Brompton folding pedal repair howto
« Reply #4 on: September 06, 2009, 07:29:22 pm »
Like you said previously, it's easy enough to make a bearing retaining plate should the need arise.
Just shows though, even with all the changes over the years that Brompton have done to the design
there's still lots of improvements that still need to/can be done.

Quote from: Marbeaux
Have given this a great deal of thought and decided not to contribute to any further Threads for the time being.
POTD. (decade) :thumbsup:

Re: Brompton folding pedal repair howto
« Reply #5 on: September 06, 2009, 07:35:21 pm »
Thanks RZ - really useful.

beachedbum

Re: Brompton folding pedal repair howto
« Reply #6 on: May 31, 2011, 02:03:22 pm »
Hi All,

Thanks again to Rogerzilla for this very useful information, which I only found AFTER ordering a replacement (upgrade Ti :) saving a measured 26g :-\) folding pedal.

Thinking more about the unsuitability of this bearing for bending moments, I wonder if it would be worth upgrading it to a roller bearing with the same dimensions like this:
   N203 SKF Roller Bearing Cylindrical Light Series N 17x40x12mm


At almost £30 it's not a cheap option, but it might be a more permanent solution than replacing the ball bearing every couple of years.

Interested in any thoughts...

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton folding pedal repair howto
« Reply #7 on: May 31, 2011, 02:19:36 pm »
A double-row bearing would be better.  Roller bearings generally don't do so well with eccentric loads.  I don't know of any double row bearings that are a straight swap though.  If there was one, it would use tiny balls, reducing durability anyway.

I must be fairly gentle on B pedals.  I got a small amount of bearing wear with my 1998 B after 3-4 years of daily use but not enough to bother replacing the bearing.  I do get some play in the pedal latch mechanism after a few months but again, not enough to bother doing something about.
Wheel meet again, don't know where, don't know when...

Re: Brompton folding pedal repair howto
« Reply #8 on: May 31, 2011, 04:20:45 pm »
... I must be fairly gentle on B pedals.  I got a small amount of bearing wear with my 1998 B after 3-4 years of daily use but not enough to bother replacing the bearing.  I do get some play in the pedal latch mechanism after a few months but again, not enough to bother doing something about.

I tend to scoot on left hand pedals, getting on and off the bike, which probably didn't help the wear on mine.

If I'd thought about it, I'd have maybe been a mite more careful.
Actually, it is rocket science.
 

Re: Brompton folding pedal repair howto
« Reply #9 on: February 20, 2013, 07:49:35 pm »
By way of an update, my father-in-law rides the bike most days and the pedal is still intact.
Never tell me the odds.

Re: Brompton folding pedal repair howto
« Reply #10 on: February 25, 2013, 08:18:48 am »
My folding pedal developed a 'click' after very few miles. I prised open the seal and cleaned and regreased. Been fine for 2 years, touch wood!

Re: Brompton folding pedal repair howto
« Reply #11 on: July 09, 2013, 06:56:59 am »
Just to be more exact with SKF bearing type code.. It's 6203-2RSH, where "6203" defines bearing dimensions, "2" says that there is shield on both sides and "RSH" defines the sealing type. So if you are looking for this bearing, then type 6203 in google.

Thanks for rogerzilla about this topic!

Mr Arch

  • Maker of things! Married to Arch!
  • Gothic Arch
Re: Brompton folding pedal repair howto
« Reply #12 on: July 13, 2013, 10:15:13 pm »
I changed the bearing in my folding pedal the other day.

Instead of filing away the retaining flange I used a drift to carefully open the flange back so the bearing could be driven out.
When the new bearing was 'glued' back in I carefully folded the flange back over the bearing so it looks original.
I figured that if the flange cracked and broke off then I could file it all off anyway.

So far so good.  The first proper ride was towing a heavy trailer and it was nice not having the clicking.
The old bearing was dry and the seal on both sides was almost completely missing.

Re: Brompton folding pedal repair howto
« Reply #13 on: July 17, 2013, 02:49:16 pm »
MFWHTBAB -would you have any pictures about the process? I have new bearing ready, now just thinking: "to file or not to file".. :)

Mr Arch

  • Maker of things! Married to Arch!
  • Gothic Arch
Re: Brompton folding pedal repair howto
« Reply #14 on: July 19, 2013, 09:04:27 pm »
MFWHTBAB -would you have any pictures about the process? I have new bearing ready, now just thinking: "to file or not to file".. :)
Unfortunately no photos of the process.

The 'special tool' was a 1/4" cold chisel that had seen better days.  The tip was ground to form a squared off blunted edge and rounded to match the curve of the bearing flange.
I used to drift the flange out by working round and round the flange until it was all turned back clear of the bearing.
The bearing was then changed as the OP's instructions.
Then the flange was carefully peened back over the bearing.

Aside from a series of hammer marks around the flange it looks as original.

I figured that there was nothing to lose except time as if the flange fractures then it could be filed off anyway.

Re: Brompton folding pedal repair howto
« Reply #15 on: July 20, 2013, 07:55:46 am »
Thank you! Sounds not too difficult at all. ;D

LittleWheelsandBig

  • Whimsy Rider
Re: Brompton folding pedal repair howto
« Reply #16 on: August 09, 2019, 04:45:45 pm »
Swapping pedals for the Brompton World Championships showed me that my folding pedal is dead, dead, dead. There is another dead folding pedal in the garage, so it is time to try swapping bearings when I get back from PBP.

I can't find a double row bearing narrower than 16mm, significantly wider than the 12mm single row original bearing. I don't think I can bodge one of those to fit in the available space and most of them are unshielded anyway.
Wheel meet again, don't know where, don't know when...