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| *Vultures Knob>>>Bike Pedals |
Pedal keeps coming loose? |
Hi. I could really use the help of one of you bike gurus out there. It seems I've been doing nothing with my bike but taking it to the shop for two weeks. It all started when the original pedal came loose. At the shop, they told me the screw was stripped and that the box (the one holdig both pedals) was stripped as well and they would replace it, and give me new pedal arm, because the old one had been knocked around and was useless. One month later, same exact thing. The pedal screw unscrews, the arm gets damaged from beating. I get a stronger box, another pedal arm, and another pedal on the other side. So everything is now brand new: Both pedal arms, the box holding them in the middle, the screws, the washers. I come home from the shop and the pedal's a bit loose. I figured they probably just didn't get it all the way through at the shop and I tighten it back in. I rode for 40 minutes today. And sure enough, both pdals are slightly loose again. WTH? Sounds like a nightmare! I have no idea what would cause this, but the first guess is that something is wrong with either the pedal threads or crankarm threads. It's possible that they aren't tightening them enough, but they'd have to really undertighten them for it to come loose so quickly. Is there a slim chance that they use a thread tap to clean out the threads in the crankarm before they install the pedal, and possibly are making the female thread larger? Sheesh.....that's a longshot. If you're using the same brand of pedals or cranks each time, there's a possibility that a manufacturing defect has the threads made out of spec, in which case things will never tighten up properly. Another thought.....you mentioned washers. Most people don't use washers between the pedal and crankarm except on carbon fiber cranks. If you're using them, make sure they're the ultra-thin pedal washers and not standard thickness hardware washers. If they're thick, then it's possible that you don't have enough of the spindle threads going into the crankarm and they can't get enough friction to lock down and stay tight. One quick fix that comes to mind (not a good substitute for proper parts, but it'd work): use some Loctite thread locking compound to hold the pedal in place. Try the red compound first, and if they still come loose, move up to the green compound. Important: there are two types of "green".....one is removable and the other one is Capital-P Permanent. Use the *removable* one (it softens up with applied heat). The green compounds are stronger and more impact resistant than the red (or the minimum-strength blue). The disadvantage of this is that if you needed to remove a pedal away from home, you wouldn't be able to easily, if at all. Keep in in mind, the best solution is to get parts that fit right up front.....there shouldn't be any need for locking compounds on pedals at all! Ok, one last off-the-wall thing came to mind......if there's ANY possibility (and this would be totally weird) that the crankarms are able to be put on the wrong side of the spindle (left vs. right), then the pedals would likely come undone quickly. Never heard of that happening, but it's a thought, and I know some euro and bmx cranks look like they could interchange (in photos, anyway). The left and right pedals have opposite thread patterns.....this keeps them from unscrewing as you ride. So if that got all backwards, presto. (man that's an even longer longshot than the other idea I had). If your bottom backet (I think this is what you meant by "the box"....?) was stripped, there's something seriously wrong going on here. Anyone tinkered with the bike? Doing some jumping or urban stunts? Something's not right at all. I hope this helps a little......ya got me curious now. :o) If you have already taken it to a shop and everything has been replaced then it is not the fault of the bike. The only force a pedal is supposed to have on it is pedaling force, so if you are trying to grind on the pedals or something like that then it is your fault. There is no crank or pedal on the face of the planet that will take that kind of abuse for very long. The clue here is that you admit that the bike is being knocked around, and that the pedal gets damaged from a beating. So, I imagine your "riding" really isn't riding... right? 27 years in the industry and have seen lots of problems like this while "Just Riding Along". Very STRANGE. Pedals coming loose after the bike shop replaced everything??? It ain't your fault. Riding a bike shouldn't do this. Take it back to the shop - ask them what the heck is going on, they "fixed" it - supposedly. Better be NO CHARGE for this, else find another shop that knows what they are doing. The best reason I can come up with is the pedals were never tight in the first place. There could be many reasons for the problems & it is difficult to give an answer without seeing the bike and it also depends on what kind of system you use. First I have a couple of question and I'll attempt an answer from what you have said so far (assuming you are using "traditional" road-bike style equipment). Questions: Do the actual pedals loosen from the crank (the long piece connecting your pedals to the main bearings) or do the cranks come away from the bottom bracket axle (the big shaft running through the frame)? Did the bike make a creaking noise when you pedalled? My guess: It sounds like it's not the pedals that are the problem but your crank arms coming loose. The cranks are not attached correctly to the bottom bracket or (most likely- IMHO) there is grease between the axle and the crank. Although it does not sound logical, you should not lubricate between the cranks and the bottom bracket. A little grease or oil is enough to allow the cranks to move slightly (a few microns is enough!) relative to the main axle. This will gradually get worse as the "flats" inside the crank (normally soft aluminium) deform and become curved. Hope that makes sense...? |
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