Thursday, October 20, 2011

Perplexing Pedal Problems

I’m having no end of frustrations with Gilbert's left pedal.
While I love the additional visibility of the flashing Pedalite pedals with the internal generator, I’ve had three pedals fail on the left side.  Inconveniently the pedals are sold only in pairs, and I'm starting to accumulate a large collection of right threaded pedals!

Ever since Gilbert's initial build, it felt like there was a noticeable “wobble” in the left pedal- which was especially noticeable when I’d been riding another bike, and got back on Gilbert.   I looked for a long time for a replacement vintage crank, and then after deciding the ones on ebay were awfully pricy for something that also might be broken (buying other people's problems!), I bought a left reproduction crank.  Unfortunately when it arrived it was poorly made and the cotter pin hole was out of round and too small.  Unfortunately I only realized this after I’d removed the old crank!

Looking at the crank it didn’t seem bent in any way,  and I wondered if having installed it with poor quality cotter pins could have caused the wobble.  I also needed to ride to work the next day, so I reinstalled the crank  with the fancy pantsy cotter, and went ahead and threaded in the brand new pedalite pedal to see how it worked.  I followed the same procedure that I've always done, greasing the threads with Phil's waterproof grease, hand threading it and then hand tightening it with a box wrench.

Unfortunately I had put the crank too close to the bottom bracket, and the crank was hitting the kickstand a tiny bit- just enough to make a tic-tic tic noise.  I tried to remove the kickstand to reposition it, but I couldn't loosen the bolt  and it was getting late, so I hit it with some PB blaster and decided to try it again in the morning.
I couldn’t get it in the morning either, so I decided that I could live with the annoyance, and headed to work.  On the ride home, I noticed the pedal was quite wobbly, so I tried to pedal mostly with the right leg (!)  and limped home.   I tried to remove the crank, only to find that the pedal threads AND the crank threads were completely fubared.    And NO, since you asked I did not force a right pedal on a left crank- I know because I tried that for about 10 seconds, realized my error and got the left pedal.  I used the left pedal,  I didn't use any unnecessary force, and although I understand that crossthreading with steel pedal threads and aluminum cranks is a common cause of damage, this is a steel crank,  and although I can underestimate my strength, I have a hard time believing that I torqued it enough to force it on and do that kind of damage.   I am NOT certain that the crank wasn't previously damaged, but I didn't notice anything unusual when I hand threaded the new pedal on.

I was lucky to find a replacement left crank in the parts bin at Broadway bikes.  I checked it out against a Raleigh sports that was in the shop for service, and measured it and it seemed the same as the ones I have.  It was stamped L,  and didn’t have the little Sir William etching that mine had, but otherwise seemed identical to the old one.

So I replaced the crank, mangling an artisanal cotter pin in the process, making certain to put the crank outboard the same distance as the drive side pedal to duck the kickstand issue (for now).   Since the brand new pedal’s thread was destroyed, I thought I’d put an old rubber block pedal I had on for the moment.
Strangely, these pedals didn’t want to thread onto the crank (yes, I know that seems like a warning sign)  but I did have one of the old pedalite pedals on which the electronics had failed, but the threading seemed fine.  And it screwed  in easily to the crank….

Again, rode off to work, and on the way there, noticed that the pedal was unthreading itself from the crank !!!!  I’ve never had this happen,  and I had tightened it reasonably but not excessively.  I pulled over, and it seemed not only unthreaded but loose, and it looks like the threads are destroyed in the same way the new pedals were!!   

Can't tell for certain, but the threads on the crank look undamaged, or at least less damaged.

At this point I’m not sure what to do.   I understand that it's fairly standard to have the crank tapped out and use a threaded bushing for a new pedal,  but then I’d have to buy yet another set of new pedals.  Also Harris has the bushings and the tap, but are hesitant to do it to a chromed steel crank.  additionally, I don’t know if it’s possible to cut new smaller threads on the brand new pedal that’s ruined to make it fit somehow with one of those 1/2 to 9/16" adapters?

This is going to sound extreme, but if this new crank has damaged threads, and the new pedal has damaged threads, I’m seriously considering epoxying the pedal into the crank,  and using it until it fails from weather or old age, and then tossing both crank and pedal,  and solving the problem then.  My only concern would be damaging the BB.  And that that point I'd just scrap the damn cottered cranks,  buy a threadless BB bearing and new crankset!
Before I do that I’m going to take Gilbert to Harris and see what they have to say.
Until then any suggestions from the blogosphere?


  1. my only suggestion is tell me when you come. maybe we can meet for a quick cuppa!

  2. First, take a real close look to verify that the pedal and crank threads slope the same direction (manufacturing error?). Then, try threading the left-side pedalite pedal into the BACK of the left crank, it should go in easily, but not too loose and not too tight. If it doesn't work, have a shop check the threads with a thread checker to make sure the threading
    If that works, I would have the threads chased with a standard left pedal tap and then try the non-lighting pedalite pedal.
    The threaded bushing would be a method of last resort to me -I've never had to do that yet. I have started to cross thread a crankset and have had my LBS chase the threads - Ferris Wheels did it on the spot for me last June.
    Good luck,

  3. Is Gilbert a French Bike? I tried to search your blog but I get no real technical data on your bike. Just a pretty name and descriptions. If the cranks were manufactured in France, then maybe the 9/16 isn't big enough to tighten securely. (see below)

    What make is your bike and who makes the cranks? You mentioned the "little Sir William etching " that your old cranks had and that you had compared them to a Raleigh in the shop. Is Gilbert a Raleigh or other English make? If it is a Dutch bike or some other, the parts could have been made in France.

    My guess is the pedal may not have been tightened fully. The other possibility is both cranks had damaged treads where the pedal inserts into the crank. The metal in the cranks may be of a lesser grade and susceptible to failure. (And hence in the bargain bin at the shop.)

    With the winter coming on, I'd opt for a new Phil Wood BB and a new crank set. Have the work done over the slow winter months in the shop and they'll have the time to do a nice job while you really won't be needing the bike.


    From Sheldon Brown --
    (Scroll down to pedals)

    Pedal Threading


    The right pedal has a normal thread, but the left pedal has a left (reverse) thread. The reason for this is not obvious: The force from bearing friction would, in fact, tend to unscrew pedals threaded in this manner. It is not the bearing friction that makes pedals unscrew themselves, but a phenomenon called "precession".

    You can demonstrate this to yourself by performing a simple experiment. Hold a pencil loosely in one fist, and move the end of it in a circle. You will see that the pencil, as it rubs against the inside of your fist, rotates in the opposite direction.

    Note! The precession effect doesn't substitute for screwing your pedals in good and tight. It is very important to do so.


    Thread Sizes

    Most pedals have 9/16" x 20 tpi threads.

    Pedals for one-piece cranks are 1/2" x 20 tpi.

    Older French bicycles used a 14 mm x 1.25 mm thread, but these are quite rare. French-threaded pedals are commonly labeled "D" and G" (French for "droite" and"gauche" (right and left). A French pedal will start to thread into a 9/16 x 20 crank, but will soon bind. Do not force it, or it will damage the crank.

    A 9/16" pedal threaded into a French crank, might go in but will work loose and damage the threads. (Too small a diameter and a different thread pitch).


    Pedal Threading

    Standard-3-piece cranks: 9/16" (0.56") x 20 tpi --- 14.28 x 1.27 mm

    One-piece (American) Cranks: 1/2" (0.50") x 20 tpi --- 12.7 x 1.27 mm

    Old French: 0.55" 20.32 tpi --- 14 mm x 1.25 mm


    Good luck and let us know what works out.


  4. In a steel crank, pedal threads will fail before the crank threads unless the pedal thread is very high strength. Since aluminum cranks are common, it is a waste to choose something stronger than it takes to fail them. A good machine shop should be able to put in an insert quicker, cheaper, and more reliably than Harris and will also be able to advise on what is wrong with the crank threads.

  5. Before you tried epoxy or JB Weld, a threadlocker (Loctite) would be maybe more appropriate, although if you grease the threads and torque the pedals and they are square to the crank, none of those should ever be needed. But, old steel cranks, maybe slightly wonky pedal threads, it could work.

  6. I'm inclined to fault any product that a) is designed to do more than one thing, b) has failed one more than one occasion, and c) flashes -- i.e. the pedals. Possibly poor sizing of the threads (too small), or metallurgy that's not up to snuff. Where are these things made, anyway? It's not possible that they're actually cut to metric (14 x 1.25) thread rather than 9/16-20, are they? Because that would result in the threads being too small for the crank threading. I'd ditch them, and use whatever you were happy with before the promise of "floor wax and dessert topping" came along in one product.

  7. I'm going to guess that it is a combination of cheap threads on the pedalite pedals and worn threads on the two crank arms.

    Safe to assume the pedals have the correct thread on them, but there can be some variation in how deep the threads are cut, how strong a metal is used, etc. On the crank arms, not unusual on parts this old for the threads to have gotten beaten up, corroded, etc. Combine the tow and you get trouble. The fact you couldn't get that other pedal to thread in at all makes me think that the threads on the newer crank arm may be damaged.

    Solutions? You could ask the shop to try re-tapping the thread on the crank. Then test fit some other pedals to see if they seem like they'll hold well.

    BTW - are you buying replacement pedals or getting them replaced under warranty?

  8. @ Max Util, Thanks for the suggestions. I'm going into the shop tomorrow for re-threading, a new/old crank and who knows what on the pedals.
    I got the first pedal replaced under warranty as it failed faster than the right. The right failed eventually, after at least two Boston winters, which I consider reasonable attrition. After that I've had two left's fail, a replacement and a new purchase, which makes me think it's not the pedal,but another part of the drive system.
    Ideally I'd buy a NOS, or a repro crank to avoid buying someone else's problems, but so far no luck with either.

  9. I would like an update on your problem with the Pedalite pedals. Were you able to finally get them working? Or did you give up on them and use different set of pedals.

    I basically had the same issue as you. I've pulled threads out of 2 right sides, and a left side crank. The first right side was a 2 year old steel crank, the 2nd was a brand new steel crank, and the left side one was a brand new aluminum crank. Each time I got less than 10 miles out of the pedals before pulling the threads out. Pedalite replaced the pedals for me at no cost each time, and even paid to have the 3rd crank put on. I'm in the process of getting the pedals price refunded.

    I posted my full problem on that forum thread, as well as an attempted fix I did earlier today. I haven't gotten a chance to attempt installing the pedals with the modifications I did to them, but I hope to in the next couple of days.

    1. Hi Rollak,

      I've been having less of a problem with the cranks than with the internal mechanisms. Pedalite has been very generous with sending replacements, even when I just contacted them looking for spare parts. I think that the problems I was having with the threading was partly because of not tightening them enough and perhaps a problem with a french threaded crank. (why is it that people who are looking for french threaded things can never find them, but I found one by mistake, with disastrous results).

      All in all, I really like the pedalite pedals- enough to replace them every couple of years if that's what it takes. I just feel that they add an extra degree of brightness that's really nice to have. I understand that having a fairly sensitive electronic mechanism in a location that gets wet and abused isn't conducive to something lasting forever, and I think that Pedalite has been very helpful in replacing parts.
      That said, I think it wouldn't hurt to have the little gear inside be aluminum or steel instead of nylon. Can't speak to your crank problem, but in future I plan on using a torque wrench to check the tightness, because it seems pretty sensitive- too loose and the pedal pulls out, and cross threads on the way out, too tight and you can strip the crank.

      Sorry you've had such a bad experience, but I personally think that the advantages outweigh the problems that I've had.

  10. Well I'll tell you what, I currently have 3 left and 4 right pedals that are in good working order as far as the internals go. A few of the left ones even have good spindle threads. If you'd be willing to pay shipping, I'll mail them to you free of charge. I have no use for them. I tried my modified pedals today and they didn't work.

    Send me an email, rfuilrez AT gmail DOT com