- Over tightening external bb cups……
Could over tightening external bb cups be the reason my new bb has got a rythmatic clickety click in sync with the cranks revolving? It was only a cheap shimano bb and half way round first ride the clicking started and got gradually worse.
I realise a torque wrench is best for job but without one, on a a scale of 1 to 10 where 1 is feather light and 10 is blood vessel bursting tightening, how tight do you tighten yours?Posted 4 years ago
The preload adjuster is the plastic cap on the NDS. Once you’ve replaced the crank arm you only need to tighten it enough to eliminate play in the crank arm which you can feel by tugging or trying to waggle it. As soon as you have eliminated play don’t turn it any more. Tighten the pinch bolts on the crank half a turn at a time until they’re tight, then push the plastic safety latch down flat.
Over tightening the preload cap puts too much load on the bearings and will kil them pretty quickly.
Tightening the bearing cups does not affect the bearing load. I’ll see if I’ve got some pics that will help explain it.Posted 4 years ago
Here you are. This is a 105 roadbike crank, but the principle is the same.
Tighten the BB cups making sure you have all the spacers in right. Push the crank through and use teh heel of your hand to get it all teh way through.
As soon as you have eliminated all play, and no more, stop tightening!
Then use a 5mm hex to tighten the pinch bolts half a turn at a time so you don’t overstress one side of the pinch
Once you’ve tightened the pinchbolts the preload cap cannot affect the preload any more.
Finally, push the security tab flat.Posted 4 years ago
Scapegoat, thanks alot for comprehensive instructions, the ‘screwy-in-thing’ i described above is the preload cap which I tightened with an 8mm hex to within an inch of its life…….wrong!! Well, I thought that its got to hold the cranks together so best do it up tightly!!
Still going to get new pedals though!
As for front derailleur cable end catching on chainring…….c’mon, get with it, its 1 x 10 NW thesed days!
Thanks allPosted 4 years agobigyinnMember
dantsw13 – Member
No, Deore & SLX have the black tab too. It looks really flimsy, but it does stop cranks coming loose.Posted 4 years ago
No it doesnt, its merely an indicator that the crank is located correctly on the axle.
Theres a small pin in the tab which locates in a small hole in the axle.
I’ve binned both of mine as I usually forget to flick it out first.downthemiddleMember
Is it possible to really crank down on the preload adjuster ? Isnt it a plastic piece with a plastic threads ? and a small plastic tool to adjust it ? I only adjust it up just enough to close the gap between l/h crank arm and BB bearing and I find that enough, but I’d have though that if you attacked it with a lot of force that the threads would give up pretty sharpish. Just a thought but never tested the theory as I generally tread very carefully with plastic threads.Posted 4 years ago
And no I would have thought you could over tighten the outboard BB shells either. They should be in pretty darn tight. Theres a lot of surface area on BB shell threads due to the diameter, so the odds of damaging the threads provided they are aligned and clean would be remote. Probably round out the notches on the outside cup first and that would take some doing too. As with anything that needs a good torque. No point being daft and swinging off a long bar until going purple in the face. Just be sensible, but do it up firmly. Generally tools are designed with the correct lengths handles for the application it was designed for. Which is why 5 mm Allen keys arent a foot long ! IIRC hollowtech BB tool is about 9 inches long ? Just apply a sensible force to that and you should be ok
Thanks for replies, just had a long weekend in Amsterdam so onlty now mustering up the energy to log on to STW!! 😉
Preload cap on slx cranks on other bike has a plastic cap – hard to overtighten as threads will strip as said by downthemiddle. The preload cap for this post is metal and if iirc they are a set of raceface deus(?) XC cranks. Cranks go on and the preload cap goes on the driveside with 8mm hex…..this is a preload cap, isn’t it???
Was only a cheap ‘keep me going’ bb so not bothered if damaged.Posted 4 years ago
wwaswas……thanks for that, 8mm cap done up *really* tight as didn’t want to lose cranks!
So these shims on race face to manage the preload….?? All I do is put cranks on and tighten up 8mm cap, am I missing something?
So, the clicking noise……..?? I’ll try new pedals, chainring bolts tight.Posted 4 years ago
as long as you followed the instructions then you should be ok. It’s the elastomer shim on the crank arm that does the preload.Posted 4 years ago
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