[Closed] Who does my non driveside arm keep dropping off

All Shimano?

Hollowtech 2?

I've had the non drive side fall off two square taper chainsets and one external BB/Hollowtect chainset.

Its not happened for a number of years now but annoying none of the less and resulted in having to buy new chainsets as the old threads/axles would be shot. I went through a period of checking the bolts weekly to ensure they were tight but the problem still persisted.

If it's square taper then it's because you didn't tighten it up enough.

Once it's fallen off once, it tends to keep falling off because you've slightly damaged the crank.

It's probably the rest of the bike, gave you considered changing it for a new one?

Keeping the crank arm obvs!

H2 all Shimano.

Change the bike? Nah 😀

hora - Member

Change the bike? Nah

Faints

Re-reads what Hora typed

Faints again 😉

Bought the frame in March 2015. I've ruined one crank arm since then with this the second coming off.

User error

I have had this in the past with second hand cranks, the pinch bolts have usually been overtightened ovalising the axle 🙁
I had to replace them both times

Used to happen. Fitted this http://www.ebay.co.uk/itm/Shimano-Hollowtech2-Anodised-alloy-crank-bolt-M20-MTB-Road-XC-XTR-XT-SLX-Deore-/272410856645?var=&hash=item3f6cf3ccc5:m:mLfx7rB9uZmR4xFmWxQukgw never happened again

What nigew said.

I find the alloy pretension bolt that comes with saint cranks is superior to the plastic one too.

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Poor design that relies on precision fitting?

Those eBay things have a torque of 15nm stamped on them which seems way over the top!

those ebay things are also purely for setting bearing preload - too tight and you'll be on here moaning about short bearing life.

(unless you threadlock it in after setting preload correctly, in which case it might stop slippage (and might be a bastard to ever remove if, y'know, hora ever changes frames or something 😀 )

MWS is right, the design is a little bit shit but to lose multiple cranks suggests you're not doing it right, hora

mikewsmith - Member
Poor design that relies on precision fitting?

Having a larf? H2 = finger tight on the bearing preload then clamp down the pinch bolts. Haven't used anything else since Hollow Tech II came out and never had a single issue (Road through to DH)

Once the plastic tensioner has done it's job and the pinch bolts tightened correctly you could remove it and the crank arm would stay on!

I think the issue is the plastic tensioner between the pinch bolts. The cranks were used but as new condition. Who knows how they'd been tightened before. It seems shimano stuff has a very finite lifespan now though. Brakes, cranks (a few times). I MO

What do you mean spaced correctly? You mean by spacers for your shell? Ht2 is an almost bombproof system, user error more likely on install. Rock used? 😉

There is no tensioner between the pinch bolts. The only thing in that slot is the installation indicator

CP my Saint cranks lasted 5yrs+ in many many many frames 😀

One frame, three chaimswts; SLXx2 and a XT- two with spindle wear. This one just took itself off in the car when I got home. Threads cleaned and retensioned.

The only other thing is my lbs. It reinstalled my warranty replacement reverb and rerouted the brake rear hose internally. No need to remove cranks though.

Are you tightening the 2 crank bolts and going back to re tighten the first bolt after you have done the second one and then re tightening the second then going back to the first and checking that's ok etc ? Sorry if stating the obvious .

Yes, I know this trick when you've got a hard to remove bolt when it's partly rounded too.

Most likely the cranks were fitted incorrectly before they got to the "as new" state.

hora - Member

I think the issue is the plastic tensioner between the pinch bolts.

It's not a tensioner- it's just a wee lawyer tab and locator, cranks work fine without it.

Did you buy them from us? 😉

Hora,

What Ramsey Neil is on about is if you are tightening the pinch bolts with a torque meter as they pinch down on the axle you will need to torque each one up a couple of times as the tightening of one will impact the other one.

Had this problem with Kevins XTs in the Alps last year. Managed to get one of those alloy pretension bolts with a view to replacing the cranks when we got home. Didnt bother as it held fast for the rest of the holiday. A winter of Peak grime and four weeks in the Alps this year. It was still working well when we saw it on CCTV when the scrotes that nicked the bikes were legging it up our lane

Did I buy them from you?

£28, £70, £20, £120 'and now reduced to £120'.

Sppaced correctly and torqued.

I doubt it. THE only reason they ever 'fall off' is incorrect fitting*. I've done it myself. If you don't do it right, they fall off, but you DO get a warning - They come loose first. Ignore that, then they fall off.
This is the same for any crank, tapered, octalink, GXP etc.

*as opposed to mashed from a big landing.

Had this problem with Kevins XTs in the Alps last year. Managed to get one of those alloy pretension bolts with a view to replacing the cranks when we got home. Didnt bother as it held fast for the rest of the holiday

That's what Shimano should supply from new. The alloy bolts have two important benefits over the plastic Shimano jobby, They are solid, so tightening the two pinch bolts, tightens the crank arm onto the (narrow wall) splined tube with the support of the alloy nut, keeping it more rigid. If for some reason the arm does come loose, it won't just slide off as it does with the plastic nut, who's thread just rips off.

Hope that lot makes sense 8)

The only way these can come off is if bolts are not torqued evenly as per recommendation, or insufficient overlap on splines due to non-standard BB.

If alloy preload caps are helping you then you're not fitting them right. It's only a preload cap - once the pinch bolts are tightened, it shouldn't be load bearing.

The preload cap shouldn't need to support the axle from crushing if you're not overtightening the pinch bolts.

User error. Either the current one for not fitting correctly or the previous one for fitting incorrectly and damaging it.

Never had HT2 cranks fall off but I have snapped the drive side arm on a set of SLX cranks, googling brings up lots of identical looking breakages. I've upgraded to Saints on the Aeris and will upgrade the hardtail soon.

I'm pretty hard on cranks and it always used to be the non drive side with square taper and octolink that failed, to the point that I started using steel BMX style Cranks until HT2 came along.

How sure are you it's spaced right. I'd be getting a set of verniers on the BB long before id trashed three sets of cranks....

Maybe the crank is fine and it's the rest of the bike falling off.

I've had a couple of sets of ht2 now and not had any issues with them falling off, however even tightening up to the upper limit of specified torque I've found they needed re-torquing once or twice whilst bedding in. Mine have been brand new in 2/3 cases.

I would normally agree that this sounds like operator error, but to give the benefit of the doubt- a riding buddy had a set of slx cranks that constantly had problems like this. One of the fancy tension bolts seemed to help. I put it down to user error until I did them myself, with a torque wrench and a not large number of rides later they were already walking off. I've never had it happen on any other set of cranks, before or since.

In the end they worked loose and damaged the splines. He replaced them with the new XTs and has since had no problems. Personally I think they were cursed.

You could do what we did when they came loose on a ride and the tension bolt fell out- loop of zip ties through the middle and then zip tie each end to the crank arm?

First I've heard of crank arms falling off since square taper! I may have had it with an FSA crank a while ago iirc, but Shimano, never.

Swanny853 that's what I happened to one set of slx's, it smoothed/ruined the axle spline.

The zipties doesn't work, snaps on first revolution. Tried this as a ride bodge.

Looks like I'll get the ALU cap and keep a lookout for new decent cranks this time.

Decent like Shimano?

+another for user error. Yours, or someone else's.

I had this on a couple of sets of Deores. They were well used, and I think the splines were just failing. I was really careful to make sure the bolts were done up equally but they just kept working loose.

Eventually I bought a new set of cranks and they've been fine ever since. 2 years or so. I've also fitted a set of XT's to a different bike that has been used in the alps and pyrenees and they are also fine. So not always user error.

I did change the tension bolt to an alu one for the deores and regularly check they are done up properly now.

The zipties doesn't work, snaps on first revolution. Tried this as a ride bodge.

Bigger zipties? It got him home, and then lasted another ride as replacement parts hadn't turned up...

Cheapest place for new XT's currently? Think I'll leave the world of SLX and used market alone. The last descent yesterday was ass on rear tyre stuff so wouldnt have been fun if it fell off there

I would get on Ebay and try one of the ali bolts, £3 on ebay and located in Huddersfield. A lot cheaper and may save you pounds. Still got a nearly new set of XT cranks in the garage that we got just in case. Even took them out to the Alps this year just in case. They will be kept just in case we need any in the future.

In the end they worked loose and damaged the splines. He replaced them with the new XTs and has since had no problems. Personally I think they were cursed.

You'll probably find that the splines, in either the crank or on the axle, were damaged after the first incident and it was a losing battle thereafter

I got shown how to fit HTII cranks about 10yrs ago and the advice has worked every single time. I wrecked a set of LX cranks when they first came out within a few rides and was gutted.

The plastic tension cap is basically doing the bearing pre tension. So you do this up by hand etc to set them without any noticeable wobble....... Then you go through the process of tightening the little bolts and tighten them down being carefull to alternate so you get spread load on the bolts etc.

Trouble is you haven't then got a hope in hell of removing that plastic tension cap because it has been crimped by the closing of the bolts. Imagine a headset design and after tightening everything down you can pretty much remove the stem cap and it wouldn't effect anything. Well your cranks are now being held on by the tension bolts on the arm but also slightly by the cap being squashed. Once the plastic gives up after a while the fit becomes loose and they come off.

I tension, nip the bolts up so they wont slip/move off, then I REMOVE THE PLASTIC CAP. Then I nip the bolts up fully and refit the cap at the end. No difference in the use but has been 100% on a set of original XT HTII cranks fitted and removed probably 20 times.

If you cant easily remove that cap at the end, its under pressure from the nip bolts. This also answers why the alu one is more reliable than the plastic ones. They withstand this pressure better.

There is also the possibility that there isn't enough spline interface, ie BB shell width is quite wide, and maybe a couple of BB spacers fitted too, all of a sudden you're only looking at half of the splines engaging.

I had a similar issue on an old bike, fitted Saint cranks with their alloy cap, sorted.

Oh god... Bodgemagedon

I think I've lost the tension bolts on all my cranks. They are all ten years old, never come loose. I just tap them on with a rubber mallet to get tension.

[quote=Nobeerinthefridge ]There is also the possibility that there isn't enough spline interface, ie BB shell width is quite wide, and maybe a couple of BB spacers fitted too, all of a sudden you're only looking at half of the splines engaging.But then the pin in the plate wouldn't fit in the hole in the crank axle.

got some new FSA on the FS if you interested in something different?

NHS arm refit? Go private - better stitches....

🙂

Maybe the crank is fine and it's the rest of the bike falling off.

Made me laugh anyway.

Hora,

I noticed [url= https://www.canyon.com/en-gb/factory-outlet/#category=parts-transmission&id=19078 ]THIS[/url] the other day. May be of interest if you are looking to replace your current cranks.

But then the pin in the plate wouldn't fit in the hole in the crank axle

Granted, but he doesn't mention this, unless I missed it.

Leprosy. Buhdum Tish.

As with life, the answers and clear voices sit in a mire of poo 😆

Cheers all.

This had happened once to me and I realised I'd got one spacer on too many so the non drive side crank didn't have enough spline to grip on to. User error 😳 Otherwise all Shimano cranks, mountain, road and CX have been bombproof.

They only come off if

A. They've not been tightened correctly.
b. The spline is damaged.
C. The crank arm spline is damaged.
D. Not enough preload.
E. Too many spacers.
F. Out of width BB shell.

I always preload them, tighten the inside bolt, remove the preload tool, fit a metal cap-tight !, then do up the other bolt, then repeat the bolts until done. I've probably fitted a hundred various road and MTB shimano chainsets, never had one back.

The plastic cap is crap.

Never had one back..

Ok but if you did you could just get it warrantied with Shimano UK your supplier I guess.

As for badly fitted-my XTR rear mech lasted 10yrs on various bikes, my only bike. Saint chainset 5yrs+.

Yet a Zee rear mech's casting failed at the known Zee failure point, my SLX fails and my SLX brakes (twice) seals don't to be the best/100% serviceable. I think lower end Shimano kit IMO nowadays is lower quality.

They only come off if

A. They've not been tightened correctly.
b. The spline is damaged.
C. The crank arm spline is damaged.
D. Not enough preload.
E. Too many spacers.
F. Out of width BB shell.

There is also the possibility that there isn't enough spline interface, ie BB shell width is quite wide, and maybe a couple of BB spacers fitted too, all of a sudden you're only looking at half of the splines engaging.

And all the others talking about wrong spacers/width - the plastic spacer that can only be put into place when the arm is in the correct position is to stop this sort of thing being possible. Or do people just ignore the instructions?

Or do people just ignore the instructions?

the plastic spacer that can only be put into place when the arm is in the correct position is to stop this sort of thing being possible.

A [b]lot[/b] of people think it's just an annoying pointless thing that needs to be removed if it won't go into its hole properly...

🙂

But it is an annoying pointless thing that needs to be removed, if you know how to fit a crank/bottom bracket.

NEW XTs ordered. I'll also fit a ALU bolt anyway.

Things like crank arms- I don't want to muck about. The last descent to the car at the bottom was one of Peaks cheekiest and it'd been a bust ankle

well good luck but I would suggest calibrating your torque wrench, and following the instructions to the letter (and video it) so you can claim warranty. Just whipped my cranks off to fit the warranty replacement chainring this afternoon in the office, 10 mins with an 8mm and I'm away again.

Use 2 allen keys for ht2 ,tighten both bolts at the same time after finger tight preload , had 5 sets 1xdeore, 2xslx and 2x xt. No crank boo boo's so far