Hollowtech II Question
11-20-19, 09:30 AM
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Hollowtech II Question
The bolts that hold the non- drive crank on are they anything special? One of mine is starting to get a bit rounded and I want to replace it.
Thanks!
Thanks!
11-20-19, 09:57 AM
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I know Shimano sells replacement pinch bolts for the NDS Crank. When I replaced mine for the same reason, I looked at the bolt head and noted that it was neither a socket nor a button head. The bolt heads are sloped from the base to the socket. I'd find an official replacement at a well stocked LBS, though they're more expensive than I'd like.
11-20-19, 10:00 AM
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If I had to guess why they're designed this way, it's likely because they're recessed, and the head shape prevents them from binding in the recess or from rounding out the smaller socket used on button head bolts. IIRC, they specify ~80 inlb. torque for those bolts, which is way above what a button head is expected to tolerate at that size.
11-20-19, 07:42 PM
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Almost any standard bolt you get to replace one of these will have a head that's too large. IMO it'd be a good move to go torx, to prevent a recurrence.
To make the bolt fit, stick it in a drill and come at it with a grinder.
To make the bolt fit, stick it in a drill and come at it with a grinder.
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11-20-19, 07:45 PM
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Only caveat being...Torx are more common than Allen-head in having out-of-spec/tolerance drivers/fasteners. As always. Use good drivers with good purchase, or risk rounding out heads, no matter what.
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11-20-19, 08:47 PM
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Spoke with QBP today and found out which one. They are ordered!
11-20-19, 09:12 PM
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I think the idea with those tapered heads on the standard bolts is for them to round out before the thread gets stripped; they're pretty weak.
In the case of stripped splines on the spindle clamp, when you want to over-torque by a fair whack, you really have to baby those bolts.
In the case of stripped splines on the spindle clamp, when you want to over-torque by a fair whack, you really have to baby those bolts.
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Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
Sheldon Brown's bike info ~~~ Park Tools repair help
Half-step triple, using double gear ~~~ 6400 STI rebuild walkthrough ~~~ Want 8/9/10s @126mm OLD? OCR. ~~~ Shimano cassette body overhaul ~~~ Ergopower Escape wear repair ~~~ PSA: drivetrain wear
List of US/Canada bike co-ops ~~~ Global list
11-21-19, 08:56 AM
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Sugino cranks with 24mm spindles, which are of a similar design to Shimano, use standard DIN 912 M5 or M6 (newer models) pinch bolts, so for Sugino you can simply buy a bag of 50 pieces of bolts for $3 to replace them. You've already ordered replacement bolts for Shimano, but you could also measure the diameter of the head of the original bolts on your Shimano cranks, and compare them with the DIN 912 specifications. It's usually the Dk measurement. For M5 this is 8.5mm diameter. For M6 this is 10mm diameter. This is usually the nominal size with some small variation in tolerance.
https://www.schrauben-lexikon.de/norm/DIN_912.asp
Sugino wants 16Nm on those M6 bolts, but the socket head wears out on my cranks, so I replace the bolts if the sockets get loose.
https://www.schrauben-lexikon.de/norm/DIN_912.asp
Sugino wants 16Nm on those M6 bolts, but the socket head wears out on my cranks, so I replace the bolts if the sockets get loose.
11-21-19, 09:11 PM
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I think that they may differ depending upon road or mtb crank. My DA and Ultegra Hollowtech cranks use tapered socket head screws (left). The XT M780 crank replacement bolt I found uses a standard socket head cap screw. (right)
