Creaking square taper bottom brackets + cranks

[barq]

I've installed a new square taper bottom bracket and cranks on my steel MTB. I've got an annoying creaking which, through a process of elimination, I think is coming from the BB. I used a torque wrench when installing the cranks so I know they are nice and tight. However the tightness of the BB was limited by the tool (Park BBT2) slipping off the splines. I've tried it with the bike on one side and pressing down on the tool - it still slips. With ISIS I'd put a skewer through to hold it in place, but obviously that's not possible with square taper. Given the tool is open backed would you feed an M8 bolt through and try to hold it on that way? Or am I being dim and missing something?

 

[RedBike]

You normally don't need them super tight.

Perhaps all you need to do is clean and re-grease the frame/bottom bracket.

 

[NickM]

It shouldn't be impossibly hard to get the b/b cartridge fully home - are the frame's b/b threads in good condition? If not, having a well-equipped bike shop run a tap through them will improve matters.

 

[barq]

I don't think it is that tight. But I'll back it out, clean and inspect the threads.

The old (ISIS) BB was seized in the frame but once I got it in a vice it wasn't hard to remove - I hope that didn't damage the threads.

 

[NickM]

Screwing in a set of steel cups from an old cup-and-cone b/b, if you have any, might improve matters. Finding a shop with b/b taps is not all that easy...

 

[dubhghall]

Could it be a crank squeak, instead of the BB??

 

[barq]

Removed BB, cleaned and chased threads. That all looks good... Went for a ride and the creaking came back.

Could it be a crank squeak, instead of the BB??

That would be my next guess.

I just went to remove the cranks (which were torqued to 370 inch-lbs as specified by Truvativ). I undid the crank bolt and the drive-side crank fell off.

Now if I didn't know better I'd say they'd been installed far too loose and the square taper fitting is now mashed. Although I had them on and off a couple of times fiddling with the BB and I used a torque wrench each time.

Any thoughts on how to proceed?

 

[dubhghall]

I would seriously question the torque wrench. 370"-lbs is quite a torque (sounds correct though) and there is no way the crank should have just fallen off.
Are the threads on the crank bolt clean / not cross-threaded? I was taught never to put anti-seize on the spindle but to put it on the threads of the crank bolt. The threads may well then screw further into the spindle and the cranks consequently tighter on the taper at the same torque.
Sorry not meaning to patronise, I appreciate you are no novice - just suggestions.

 

[fossyant]

Crank them on by hand..should need a puller to come off.

 

[RedBike]

Even with the bolt removed there is no way you should of been able to just pull the crank arms off by hand so easily. At least you've found whats creaking!
Sadly it sounds like either the cranks are knackered or you've got the wrong type of square taper.

 

[peanut]

if the crank has had it you will lose nothing by trying to true up the internal surfaces that mate with the axle.
Clean the axle and crank hole really clean and you should be able to see from the shiny bits inside the crank hole where the high spots are which are causing the creaking.

if you can get hold of a nice long square or triangular file and carefully file the high spots you can reuse the crank arm.
You need to be really good with files .Take it nice and slow and draw the file the full length each way 2-3 times and check the fit..

 

[rickangus]

If you can't do it yourself (and I doubt it 'cos I've had the exact same problem) you might find that Highpath Engineering can reface the cranks for you.

370" lbs sounds like about 30ft lbs which seems a bit light to me. I was told 40ft lbs which I've done - seems frighteningly tight - but no further problems.

 

[barq]

Thanks everyone. It is weird so I appreciate ideas (even very back to basics ones ).

Shimano and Truvativ both use JIS (rather than ISO) square tapers so the combo should be ok (surely?).

Was the torque wrench wrong? I doubt it because I have two (click and beam) which I use interchangeably so a significant difference would probably be apparent.

I checked the bolt threading again and dubhghall's approach to anti-seize is exactly what I did. Still worth a try.

I'm starting to wonder if the cranks were substandard from the start. They were an intentionally cheap OEM set as this is a spare MTB. They also had a small amount of cosmetic damage - could that mean they were once installed (badly)? It may be academic because I doubt the shop will replace them. However I'll leave peanut's filing plan to last!

 

[peanut]

If you can't do it yourself (and I doubt it 'cos I've had the exact same problem) you might find that Highpath Engineering can reface the cranks for you.

well you do need some good tools and a little commensense but I've salvaged two old crank arms in the past. What do you think an engineer is going to do ? use some miracle cnc tool ?
I'd just sling it in the bin and buy a new crank arm for £10-£15 if you don't feel competant to file a flat on a small piece of alu

 

[barq]

370" lbs sounds like about 30ft lbs which seems a bit light to me. I was told 40ft lbs which I've done - seems frighteningly tight - but no further problems.

Yeah, I've had some cranks which also required frightening torques. In this case Truvativ specify 28-31 ft-lbs, so I was at the upper end of that range. Park suggest about 350 inch-lbs as a general minimum. It ought to have been ok.

In hindsight I wish I'd installed them tighter from the start, but then again manufacturer specs should be right (if a little conservative).