daveprozac

So I get some fancy new $30 pedals today (note the sarcasm), slap them on, and go for a ride. Little did I know that due to some stripping of the threads on the crank I turned one of my 9/16" threaded pedals into the quick release version. After tossing myself over the handlebars in the middle of an intersection I collected my belongings and what was left of my shattered pride; oh and that damned pedal that I had some choice words for. I am now needing to purchase a crank for my bike as the threads on the right crank arm are 100% stripped (this was an ongoing problem since I bought the bike, I was just hoping to not have to fix it so soon). I have very little bicycle repair knowledge, although I did work in an auto repair garage for 7+ years and prefer to do the work myself. I am looking to purchase a decent crank for roughly $50. I am a little confused as to what cranks would be compatible with my current BB, chain rings, and chain. I am not looking for anything amazing but would prefer it not weigh 20 lbs. I am also willing to spend $10-$20 more if the performance/quality increase is worth it, but would like to stay below $50 if it is possible. I have attached some pictures of the current crank. Any input or information on what cranks would work or your personal opinions about which would be the best would be much appreciated.

Wordbiker

You can have a shop tap and helicoil your existing crank for well under $50.

Call around and find out which shop offers this service. In this case, it'll be better than new and keep all your parts original.

daveprozac

That was what I thought, but a LBS (not the most reliable one) told me I would need a whole new crank. I will be taking the bike to a more reputable tech tomorrow for a second opinion but was hoping to gleam what knowledge I could from forum members so I do not go in unprepared.

gmouchawar

Hi,


I read an article once for a solution to a stripped crank arm. I was able to find it.
https://www.cicle.org/cicle_content/p...ry.php?id=1478
I haven't tried it personally, but I have a lot of respect for the author and his mission.

Mondoman

dp - if you're otherwise happy with your current crank (i.e. gear ratio, ease of shifting etc), I like wb's idea. As you point out, since any new crankset would need to match your current BB for spindle interface (pretty easy) and BB spindle length (maybe not so easy), it might be a bit of work and money to find a matching crankset.

Stripping crankarm pedal threads is not infrequent, and a better-skilled mechanic/shop should be able handle the helicoil work.

meb

My experience is about 90% of the shops don't know what helicoiling is and think it is necessary to replace the stripped crank. But the better shops do know how to fix that crank.

There are also inserts that can be placed in the cranks similar to helicoils:
https://smartbikeparts.com/search.php...hread%20Repair

operator

Helicoil is not a sure fix, and also no gurantee of having it perpendicular to the face of the arm. $30 is a new shimano triple crank with steel rings. $50 will get you a shimano triple with removeable arms. $50 to do a helicoil on a pos crank doesn't make sense.

LWaB

I've never seen a Helicoil crank repair that hasn't worked and you'd have to be a real butcher to not get it correctly aligned.

Ex Pres 

You'll likely need a new bottom bracket if you replace the crank. Just guessing here, but I bet that old Nervar crank uses a longer spindle than most sq taper cranks you'll find from a shop.

daveprozac

Agree with you guys on the helicoil but I do have some reservations about them. I have used them in the past on stripped out automotive spark plug holes with success, most of the time. Secondly I worry about the "trueness" of the hole that is drilled seeing as it needs to be pretty close to perfect. I will eventually need to buy a new crank as the helicoil will eventually fail, whether it be 3 days from now or 30 years so I don't mind spending the money on the crank if it saves me hassle in the future. My main concern is what type of crank would be compatible, and if no cranks are what BB and crank I would need and what a reasonable cost for them would be.

midwest44

I have a SS that is using a modified tandem captains crank set mounted on the right (normal bike) side verses left as a captains crank. To make the pedal threads correct for left/right threads, both cranks were tapped and correct threading heilicoils inserted. I've been riding a year this way with no problems. You do need to remember that one side is left hand thread and the other right hand. Any sort of machine shop or good auto repair can do this, but they may not have the left hand thread part. It's not too common.

Ex Pres 

You may want to check to see if your chainrings are the older Nervar (obsolete) 128mm BCD. If they are this could influence your decision, too.

Wordbiker

While I'm sure an incompetent mechanic can screw up a ball bearing with a rubber mallet (not accusing you BTW), the crank repair kit is pretty straightforward, and I've yet to have one come out poorly or fail after the fact. All it does is tap a larger set of threads into the crankarm and the insert (usually steel) sizes it down for pedal threads. I always bond them in with red Loctite and grease the pedal threads. If threads in aluminum were a concern, then all pedals would be falling off left and right.

If he's happy with his cranks otherwise, spending $15 seems reasonable. If the shop screws it up, he can hold them to it and buy a new crankset.

daveprozac

Verdict from a reputable LBS is that the hole is pretty far gone, but that he might be able to sleeve it for $30 if he cant find a replacement crank (he recommends replacement). Unfortunately, according to the tech I spoke with, the threads on the BB are most likely French spec and that a BB that fits the bike and a modern crank are hard , if not impossible to come by. Now I am really confused, most people seem to assume that a crank is a crank and a BB is a BB, that is obviously not the case. Maybe I am jumping to conclusions as the tech did say it might be standard and will not have a chance to really look it over till tomorrow or Friday. I am thinking maybe I should get this bike fixed, sell it, and purchase another bike with easier to find parts. I prefer to have something that is easy to order parts for and I can fix myself rather than an oddball nightmare of a machine. Any suggestions?

Wanderer

Any respectable machine shop should be capable of drilling a square hole(pun intended), and tapping for the helicoil.

Then just lock it in with Locktite, and you should be good to go!

Ex Pres 

Post in C&V. We have all kinds of French nuts over there.

What year is your bike? If it's 80's it's probably not French.

That FD says Sachs Huret, I believe yours will be post-French threading

daveprozac

That tidbit of info definitely brightens my day. It is a Sachs-Huret, as is the RD and the shifters. From what I could gather the bike is an early to mid 80's bike (really not 100% sure). I was also under the impression that Peugeot went to the more standard version of the BB after the late 70s but I really don't know, that is definitely a question to put to the French bike nuts. Posting over in the Classic/Vintage section. Thanks for the input.

clink83

Go to an automotive machine shop if your worried about the quality of a helicoil.

operator

French bb's are just annoying to come by, not impossible. Ebay or buy a phil wood bb.