Torque wrenches can be misleading with these, especially if using the original plastic preload thingy and the cranks are old. As you tighten each bolt, gradually and sequentially, I think you can easily go over the recommended torque setting as tightening one will apparently make the other a tiny bit looser again, so more turns can be wound on before the wrench clicks.I don't think you know how to use a torque wrench.
The plastic preloaders can also deform to help this bad process along - eventually being spat out of their threads.😯 Nope, that would take a *shed* load of torque, unless you've destroyed the preloader when installing it. I've fitted (and refitted) hundreds (possibly thousands?) of HTII cranks and never had one pop out, or fail for that matter.
Then I tightening it to about the maximum I can manage using one hand, in no discomfort, and one of those triangular 3/4/5 mm allen key tools.Ah, yes. They are meant to be finger tight, snugged up. 0,7 to 1,5Nm. You're looking at probably 3 or 4 times that with what you've described.
Agree with what Mert says re the 'preload'. Well actually it's supposed to be just taking up the clearance of the bearings, as the type of bearings used, deep groove rollers, are not designed for axial loading.
The plastic tools with a knurled edge are designed so nipping it up with your fingers is all you need.
You can't go over torque of you're using the torque wrench properly, that's the exact point of the tool! And yes, the sequential tightening of the opposite bolt does exactly what you said and release the tension on the other one.
Ah, yes. They are meant to be finger tight, snugged up. 0,7 to 1,5Nm. You're looking at probably 3 or 4 times that with what you've described.
What you're quoting there is the torque for the plastic preloader, though, not the pinch bolts to which I was referring with the hand-tight triangle Allen key thing.
Shimano have the recommended tightening torque for the pinch bolts as 12-14 nM which is into FT territory.
As for the plastic preload being spat out due to damaged threads - yes, to be honest, I can believe that. Perhaps this is where I went wrong as the knackered threads allowed the thing to be pushed out as the pinch bolts were overtightened.
In any case, the metal preloaders guard against this to some extent.
I do think that the torque values for the pinch bolts is high @ 12-14Nm, especially for such small bolts (compare with bigger calliper bolts @6-8Nm).
I think that this might be part of the issue I had although I have since noticed that the collar on my torque wrench was loosening and could slip in use upping the torque setting.
I am wondering whether I ought to stock up on pinch bolts & replace them each time I remove the cranks
How often do you do that??
Just make sure you never get a SRAM GXP crank as that is around 46nm from memory. I just have to guess at it when tightening as my torque wrench doesn't go that high.
Caliper bolts are M6 as are the pinch bolts on HT2 cranks
How often do you do that??
Quite often if you use lower end Shimano BBs and ride in the UK in anything other than high summer.
What you're quoting there is the torque for the plastic preloader, though, not the pinch bolts to which I was referring with the hand-tight triangle Allen key thing.
Ah right, I misinterpreted that. Although I still maintain that plastic thing is not a pre-loader. If you've got the crank installed properly you would be fine taking that out after, same as a headset top cap. Shimano wouldn't have persevered with the same basic design all this time If it was fundamentally flawed.
How often do you do that??
Quite often if you use lower end Shimano BBs and ride in the UK in anything other than high summer.
Well, there's a very simple answer to that, don't put even the cheap Shimano BB's in, XT level as a minimum, it's not like they're massively expensive compared to the low end ones or even push the boat out and fit an XTR one for £40, they literally last forever / 2 or 3 years.
Caliper bolts are M6 as are the pinch bolts on HT2 cranks
Thanks, I'm clearly misremembering, still lower torque though.
It's only the second pinch bolt I've rounded & the first that's needed drilling, but I"d rather not have to do it again.
Well, that's why I use Hope 24mm BBs.
Although I still maintain that plastic thing is not a pre-loader.
Probably splitting hairs now, but...
It acts to pull the non-driveside crank onto the spindle which does preload the bearings. Otherwise there is play across the BB. In this sense, I would say it is very much a preloader. Just because it could be safely removed once another locking clamp has been applied (pinch bolts in the case of both stem and HT2 crank) doesn't make it not a preloader.
But I'm happy to believe one thing and let you believe another.
FWIW, the plastic end cap should really just be used to take the float/clearances out of the bearing. Actual preload on the bearings should be as near to zero as is possible.
And there is an even simpler way to make your bottom brackets last longer, fit them properly.
Faced and chased bottom shells, proper adjustment, the usual. Think my oldest one in regular use is well over a decade and a half old, and used year round. That was pretty much the cheapest one i could get and i'm amazed it's lasted that long.
I still have an original XTR (M960) on one of my old race bikes. But that hasn't really got the mileage, despite being nearly 25 years old!
FWIW, the plastic end cap should really just be used to take the float/clearances out of the bearing. Actual preload on the bearings should be as near to zero as is possible.
Exactly! As I said before, the standard plastic tool about 40mm diameter for finger tightening is all the torque you need.
