triumph.1

I need some expert advice. I have been trying to buy a stronglight 99 crank for an Eroica bike I have and was hoping to fit a 50/34 set of rings to make climbing easieer. I purchased three cranks now off of ebay and all three appear to be bent or warped. I have a brand new true 50t chainring and put it on a straight campy spindle to test if the thing spins true and all tree wobble very badly. Were these cranks prone to warpage or spiders being bent or have I just been screwed three times in a row? The bb on the bike is the bottom bracket original to the bike and the original campy crank spins true. Any advice how to proceed as I think I am done buying junk cranks, thanks.

bikemig 

I've had zero problems with stronglight 99 cranks; it seems weird that you have had issues with 3. They are a great choice for an eroica build exactly for the reasons you give.

Kontact 

3 cranks and one spindle. I'd be looking at that spindle.

Take the rings off and measure to the seat tube which spider arm is furthest out. Then remove the crank and try it again rotated 90° on the spindle. Is the same arm still furthest outboard?

triumph.1

I just put on the strong light bb and no difference all three spin with untrue side to side. I guess I will have to try and return three bad cranks and run the 53/42 campy crank I have which will really stink.

triumph.1

The spindle spins as true as new with the campy crank on it and I did just change the bb to the strong light bb I have and there is no difference. This would definately indicate and issue with the used cranks. Can they be fixed or would they be throw aways?

Ex Pres 

It's worth putting a big wrench on the crankarms and giving them a good tug, or getting out a hammer (with protection of course). You wouldn't be the first one to give a crank a good whack. What's the worst that could happen - you're not going to use it anyway.

fietsbob

Reads like you were just the guy they unloaded bent crank arms on... it's just the risk of online shopping for used stuff..

juvela

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For Eroica use I would suggest getting a first generation or "Mk.I" with the bare metal finish which can be polished if one so wishes. Second generation launched 1977 and has the anodised finish.

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cyclophilia 

Do you observe the same result with a different Stronglight chainring? Do the large and small chainrings both exhibit the same amount of deflection? Depending upon the amount of run-out you might be able to gently adjust the chainrings so that they run true. BITD bike shops would use a crescent-style wrench or the Bicycle Research tool to correct minor anomalies in the chainring alignment.

tinkerbike

Try the crank on all 4 spindle seats - rotate it around the flats to see if the wobble improves for different seatings. Sometimes there's one that will spin true.

CO_Hoya 

I've had bent Stronglight spiders before. I followed the instructions from Sheldon Brown and was able to resolve it to my satisfaction.

triumph.1

I will give the suggestions a try, thanks all for the direction. I have a good friend that is a true vintage guy and he is gonna try to get over to assess the issues first hand. It would be nice to salvage one of the three cranks for the darn money I threw away. Thanks again everyone it's cool to be able to get support for vintage stuff I don't know a lot about.

triumph.1

Whoa, this looks like a simple fix, thanks for that link!

due ruote 

Please report back. 3 bent cranks seems fishy. I would be curious to know the outcome.
Also look at it this way - if you can determine that they are not bent, you can resell 2 of them with a clean conscience.

ThermionicScott 

Dare I ask if you lubed the spindles at all? It's felt by some of us (but certainly not all) that cranks are more likely to go on straight if they are allowed to "glide" into position before being torqued, whereas a rough part of the mating surface could catch and cause the crank to become crooked if you don't.

dddd

At some relatively early point in my old-bike resuscitation activities, I decided that I needed to achieve better mastery of front derailer foibles, especially as the often ill-functioning "road triples" came into vogue using off-brand cranksets and who-cares-who's chain installed from the factory!
Pretty much the first requirement was to achieve true-running chainrings, for obvious reasons.
I learned right away that there is risk in applying any bending loads to an installed chainring when I broke a chainring mounting tab off of a cast Suntour GPX crankarm while applying bending load directly to it's installed big chainring.
The chainrings are made of cold-worked material, and so are very springy. So it is the crankarm spider itself that is the more-usual culprit, even with forged cranks. The relatively rare bent chainrings can be quite tricky to align in and of themselves, especially the big rings with their deeper sections that can hide stress-relieving nightmares.
I adopted the simple method of taking a 3# hammer and foot-long dowel rod (fashioned from a wooden broom handle), and using this to impact-true the crankarm spider arms, always applying the load to the bolt heads (and nut heads, depending on whether I am moving a spider arm to one side or the other).
This is a very fast method that I have used many hundreds of times now without ever having broken another spider arm mounting tab, since I am not generating torque through any length of a big chainring's mounting tabs. The slender dowel even sneaks in to where the non-driveside crankarm may be directly in the way when impacting a "shielded" spider arm from the non-driveside.
On one occasion I even did this to good effect while out test-riding, using a rock and a piece of wood to perfect the trueness of the Stronglight 93 crankset I had mounted to a Raleigh 753 team.
A good idea (posted already) is to rotate the driveside crank to each of it's four possible positions upon installation, before installing the left-side arm, to check for which of the four positions has the chainring running straightest before proceeding with installing the left arm. I do that with probably most of the used-bike builds that I throw together, it's easier than bending things or at least minimizes the amount of any needed bending, and it's not necessary to heavily torque the arm onto the spindle with each test-fitting. So the process goes quickly.
I thus regard a bent chainring as a more-tricky problem than a bent spider arm or arms, though in one instance I encountered a defective Shimano Octalink 5503 crankarm that apparently was manufactured with a wild amount of off-axis wobble between it's bb interface and chainring mounting points that could not be remedied.
Again though, after hundreds of repetitions, I have yet to damage a crank of any type by using the dowel and 3# hammer, and it's pretty fast work that takes but a minute or three.
Now if I was buying a crank and found say 1/4" or more of chainring runout, I would not feel that I was being unfair in requesting refund or compensation for what I would term a bent crankset, because it should have been obvious to the seller, and might involve the chainrings as well as the crankarm spider.

triumph.1

I talked to a friend who mentioned over the years he had gotten a hold of several cranks that had the same symptom as my stronglight crank issues. He said he finally figured it out that the cranks had been poorly maintained/used or possible were run semi loose on the spindle causing the spindle hole to wear oddly. I still have not had a chance to get the other friend over to look these cranks over, but am hoping soon. I contacted the ebay seller from the last sale and he is willing to take the crank back, but did say he rode the crank on a bike w/o an issue? Is it possible the hole is worn to a specific spindle? I still find it hard to believe three cranks have the same problem, but anything is possible. If it is a case of wear can that be fixed with a shim or another method?

triumph.1

Dry, I am afraid. grease completely slipped my mind as I generally don't ride vintage bikes a lot anymore.

Hudson308 

Despite a fair bit of controversy regarding this, my LBS owner buddy swears by it.

due ruote 

Dry vs. greased square spindles is one of the great C&V debates.

Salamandrine 

If the inner tapers of the cranks are distorted because they were ridden when loose, there's really nothing you can do. Unfortunately, that makes them toast. However, that may or may not be the case. Usually the indicator for this is that they simply won't stay on. No way to know for sure but to try.

I agree with suggestion to try the crankarm for fit four ways, and go with the one that gives the most true fit to start.

In this case I would use grease on the tapers, primarily because you may be force fitting over a slightly mangled surface. Tighten them on to at least 25 ft lbs. I'll sometimes go to 30 for the left. Be sure to grease the crank bolt and washer well. (i'm not going to get into the grease or no grease debate - some other time) At that point you can get to work truing the spider, and then the chainrings, if necessary.

dddd

The right crankarm will handle more torque before any over-stress of the aluminum ever takes place as from repeatedly re-torqueing (which is a no-no).

Either the square taper is hogged out or it isn't, a visual inspection will show if it's all chewed up inside.
Even really chewed crankarms can be used if the bolt is secured with Loctite, I finished one CX race where my left crankarm was intentionally ridden till it fell off on the last lap since I was trying to hold my position on the course. I finished the second half of the last lap riding one-legged and finished the season using that same arm.

The chainring wobble has nothing to do with whether the tapers were lubricated, and wear in this area just isn't a real concern in the real world.

Truing the chainring spider is a valuable skill that is actually fun to learn using the correct foot-long dowel and 3# hammer, just practice building up to the needed force level until the needed correction is achieved. Patience is your friend, just be sure to use the front derailer cage as your reference sighting guide above the rotating chainring, and situate the bike to not roll as you apply the corrections (rubber band around the rear brake lever to handlebar).

To the OP, how far out of plane was the chainring wobbling? A quarter inch is not too uncommon on neglected used-bike finds, but bigger bends are reason for concern imo.

nesposito

you can pick these up cheap and throw them on for L'Eroica. They have 48/34 gearing OR they offer them as a triple as well. cheap and easy fix


https://www.ribblecycles.co.uk/stron...oad/#pid=21949

Salamandrine 

While that is probably true, it's rare to actually fracture a crank this way, and the left crank arms are much more prone to loosening up. That's why there's a plethora of single right crankarms on ebay...

Also true that loctite will hold them on if mangled, but this is less than optimal, for obvious reasons.

dddd

Pretty much everything with vintage bikes is less than optimal in some way or another, but if the square hole is mildly damaged I would argue that re-attaching with full recommended torque and Loctite may be an optimal approach to the repair.


I've seen enough split crankarms to consider that failure to be other than rare, though certain cranks including many made by Shimano seem particularly resistant to splitting as there is more metal surrounding the left arm's square hole. I worked at a place where one mechanic routinely re-tightened the crankarms on their rental fleet, and like clockwork a lot of them started splitting.