Sunday, October 17, 2010

Pedal Rebuild

The Motobecane came to me with a nice old set of MKS pedals.  I got that bike about 18 months ago, and rebuilt the pedals shortly after it arrived.  They were installed on the Motobecane last year, and on the Schwinn this year.  I know I put just over 300 miles on them this year, maybe 30 of that in rain.  And I am guessing they had 200 miles or so logged last season.  So they haven't seen a lot of use, in other words.

On Thursday, I took the Schwinn to the grocery store for a quick bit of shopping.  While parking the bike, for some reason I reached down and turned the left pedal by hand, and was surprised to find that it was in need of another rebuild -- gritty and coarse in its movement.

So Friday morning, I pulled the pedal off the bike and brought it inside to take it apart.  It's a simple job, rebuilding pedals designed for it, and it took all of 3 minutes to unscrew the dust cap, loosen the locknut and then back off the outer cone with a screwdriver (the cones are slotted, not shaped for a wrench).

What I found inside was interesting.  First, the teflon grease smelled strongly of chemicals, where it barely smelled at all when I put it in.  I don't have any idea if this matters or not, but it seemed a little runnier (still grease, though, not oil) and was definitely stinkier.  Second, the outer bearings (the ones under the dust cap) were still turning in grease that looked clean, but grease in the inner bearings was black.

The bodies of these old pedals have a black plastic insert that appears to serve as a seal against the pedal axle.  I'm guessing that the blackness in the grease is a combination of contaminants, including some measure of plastic abraded away from this insert.  There are a couple of things that could cause such abrasion.  First, physical contact with the axle, which might have happened if I adjusted the outer cone too loosely, and the pedal body was able to move around under the load of pedaling, and actually contact the axle.  And second, grime making its way into the small crack between the axle and plastic seal could have become an effective abrasive.  Pulling the second pedal off and opening it up revealed much the same thing, but not quite as far along.

There's really not much to be done about grit -- it's out there, it's on the road, and all you can really do is clean it out when it gets to be too much.  But as for the bearing tension, I recalled what my instructor at Broadway Bicycle School had said -- to snug down the locknuts to make the bearings on a freshly packed hub feel a bit too tight, with the confidence that they'd loosen up a bit with use.  My last repack was done prior to this advice, so it's entirely possible I went a bit too easy on the adjustment.  So this time, after replacing the grease and 11 bearings per side, per pedal, I tighened the outer cone a bit more than I normally would have, and snugged the locknut down on a bearing which doesn't feel as loose as it ought to.

I've got a few more rides coming this fall, and I'll try to use the Schwinn as much as I can, to exercise the pedals and get them settled in.  I took it out today with the girls, where I followed Ava around on her little Gary Fisher mountain bike, iPhone in hand, snapping photos.  That's probably not smart, but it was still fun.  The pedals felt fine underfoot, not calling attention to themselves, and so Ava's increasing confidence got all of my attention.

With any luck this rebuild will last more than 500 miles or a couple of seasons.  If not, I suppose I won't feel too badly about retiring a pair of 35 year-old pedals.

All for now,


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