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Please can anybody offer some advice on what to look for with this annoying problem.
Fitted a full 1x12 X01 Eagle DUB groupset to my bike when it was new 14 months ago. It has only been ridden about 10 rides and 200 miles or so at most as I have generally lost interest in it for now.
The mojo will return I'm sure, and one thing I remember from the last couple of rides was a slight knock / clunk feel as the driveside crank went over the top middle. Happens no matter what force is applied to the pedals and whilst it isn't exactly loose like old worn square btm bracket days, there is something not happy as I wouldn't expect it to move / clunk at all.
Took it apart, including the Hope bottom bracket the last time I rode it and re greased/torqued everything up yet it still does the same.
Direct drive chainring feels tight and doesn't move - really don't fancy putting any more torque into the bolts holding it on. Btm bracket appears ok and all tightens up well.
Only thing I haven't checked is the cassette as I didn't think that would have any relevance to it, but will have a look next weekend.
Have swapped the pedals and made sure it isn't them.
Any ideas before I go nuts and waste some money on a Shimano crankset and btm bkt instead?
Did you really tighten up the crank arms?? Those SRAM cranks need some serious torque with a wrecking bar in my experience. Wind out the preload and then apply 50Nm. It’s some force! Then adjust the preload. Shimano is so much easier!
If the BB bearings are smooth and the crank is done up to the correct torque (**** loads) then you might need to find another culprit. You have done the preload on the NDS properly, I take it?
I speak as the victim of a similar issue - a knock at the same point in the crank rotation - DS top, NDS bottom of stroke (shimano crank), particularly under load when climbing. I worked through all the possible causes - new bb, swap pedals, different crankset. I thought at one point it was the clutch on the mech sticking and not playing nicely with an oval ring, but that was stripped and regreased with no effect). Also suspected a dodgy bolt on the chainring, but a different chainring and bolts didn't fix it.
I'm now convinced it is a rough bearing on the lower pivot. I'd discounted this earlier because it happened with everything locked out. But new bearings are in and tomorrow's ride will reveal all!
Possibly a stupid question, but the BB is fitted with the DUB 29mm adaptors, isn't it?
Thanks all. I believe it is all torqued up and right - so much so that I couldn’t get the damn thing off today to have another look.
I’ve ordered a cordless impact wrench and will have another look next weekend.
The Hope 29mm adapter is in there. Might try a sram btm bkt as well as they are relatively cheap.
I went through the same process earlier this spring, I went completely bonkers and even threatened to give up mountain biking. Your symptoms sound the same and what cured it for me was cleaning the self-extracting bolt assembly out of the drive side crank. I had to buy a pair of pin-nosed pliers to get at it, but once I got the cover off I cleaned and greased the the bolt/washer assembly and when I put it together I haven't had the problem since!
I really hope it works for you. I spent ages swapping out BB, pedals, wheels, cranks etc before I nailed it down. Good luck!
Thread bumpage but as it's my thread hopefully it's ok.
Finally decided to have a look at my bike yesterday as I wanted to ride it today.
Used the battery 250Nm impact gun to loosen the crank bolt. Made a huge racket and didn't appear to move it but, when I then put the 8mm hex impact socket on my bar it came out relatively easily.
Stripped the whole thing down including the bottom bracket and removal crank bolt and noticed two things.
The BB, Hope 30mm with dub adaptor, isn't completely snug on the crank axle. All others I've had (mainly shimano) have required a mallet to lightly tap out the cranks and have not had any play in the bearing (as in the bearing inner being slightly too big for the axle). This one does and the axle just slips in and out of the btm bracket very easily.
Also the DUB ring has about the same level of movement I'm feeling in the pedals when it is placed on the crank. It moves perhaps half a mm left to right when dropped on. Doesn't feel to move at all when the 3 bolts are tightened but legs exert a fair bit more power than I can by hand.
Anyways, put it all back together and even serviced my SPDs as they had a slight play in the spindle as well.
Straight away I noticed the knock yet again. Drive side crank comes over the 12 o'clock position and 'dunk', it wobbles (or feels to) every so slightly in the direction of pedalling. Does it when not under any real load as well. Haven't tried it freewheeling without the chain on to see if it does it with absolutely no load but it is becoming very annoying for such an expensive bit of kit.
The preload adjuster is set and I can't feel any side to side wobble in it when pulling by hand.
Tempted to spend £30 on another BB to see if that helps.
Also going to check the chain mesh with the teeth on the chain ring and also the cassette and back wheel next week.
Any more thoughts and ideas would be welcome.
Damn things.
is the chain link on the correct way round?
People seem to love hating SRAM cranks. Your title makes it sound like the cranks but the actual cause is your unnecessary aftermarket boutique BB?
Chain link correct yep.
Could well be bottom bracket related but after such little use why didn't it do it from day one (same could be said about whatever is causing the problem though).
Not sure I'd class a Hope bottom bracket as boutique. It was chosen as I have a Hope regular bottom bracket in another bike that has been in a number of frames and is over 12 years old. Never been touched and never gone wrong - so I went with one for this build.
Still, you're welcome to your opinion and may well be correct with it now being the problem, and might even have a Sram DUB one somewhere to try without spending any money.
Undersize axle?
Have you measured it?
SRAM = poor tolerances.
Check your seat post.
It's more likely to be the issue than the bb
I had loads of problems after i removed my cranks for the first time to re grease. I re installed the cranks but over did the 54 nm (very fine gauge on the torque wrench , I had a click that i couldnt sort I ended up stripping the bike checking every bearing mount clamp , only when i changed the bb then it went away ,i still have the bb and it spins like the day it left the factory just a very fine tolerance on the spacer