Have questions or want to discuss cycling? Join Now or Sign In to participate in the BikeRide community.

New: Take part in the July Giveaway for VTUVIA SN100 Camouflage Fat Tire E-Bike $1679


Crank Bolt Torque?
#1
I just need a little clarification on the torque specs in the Parks repair manual. In the torque specifications for Shimano crank bolts they give a broad range of torque values(305 inch pds - 390 inch pds).
-How do you know what to tighten the bolt to??
-Should you go to the lowest, middle or the highest torque value??
-If the cranks don't get tight enough, you can end up with a wallered out crank that will never stay tight, right??
-If you go too tight you might split the crank, right??

Sorry for all the ??'s
  Reply
#2
Thanks painkiller.
The reason I ask is I torqued a new crankset to the middle value and the cranks kept loosening up after every ride. After the first ride and discovering the loosening, I cleaned up the bolt and threads and then applied blue locktite, then torqued to middle value again. I let the locktite cure for the recommended time and then went for an average ride(15-25 miles). They loosened again. I then repeated the same procedure, but with a little tighter torque and a 2x recommended threadlock cure time(2 days). They loosened again after an average ride again !!
After this, I tried again with the max torque and let the locktite dry for 4 days. I did another average ride and they loosened again !!!
What is the deal ???
This was a brand new crankset on a roadbike with low to medium crank power being used. I have'nt even stood up on the pedals to really crank down on them yet !!
Not sure if it matters, but this set uses a 8mm hex head bolt instead of the normal 14mm bolt. Does this matter??
Thanks
  Reply
#3
If you replaced the cranks but not the spindle you may have mixed two incompatible tapers - JIS and ISO. the BB. http://sheldonbrown.com/bbtaper.html. If that is the case and you are lucky you may be able to keep them tight once you have replaced. If not you unfortunately are possibly out of luck.

Otherwise I would have no easy explanation, as the middle range of torque should be sufficient - we went decades wrenching on square taper BB's and no torque wrenches without a problem.
The crank bolt type does not matter.
  Reply


Possibly Related Threads...

Forum Jump:

[-]
10 Latest Posts
New Stator For My Ride1up Core 5
Yesterday 08:49 PM
Jumps a Gear
08-09-2022 07:14 PM
Rode my First Double Century in June
08-08-2022 11:42 PM
2022 road cycling season
08-08-2022 04:03 PM
Cycling photos while on holiday
08-08-2022 01:17 PM
Vairas vintage bicycle brand
08-08-2022 11:45 AM
New user
08-08-2022 11:38 AM
Harvest Rush Gravel Grinder! $1,000 cash...
08-08-2022 09:15 AM
Lock ring clearance
08-07-2022 09:42 PM
Why should I buy an e-bike?
08-07-2022 02:07 PM

[-]
Join BikeRide on Strava
Feel free to join if you are on Strava: www.strava.com/clubs/bikeridecom

[-]
Top 5 Posters This Month
no avatar 1. Jesper
22 posts
no avatar 2. ichitan
21 posts
no avatar 3. ReapThaWhirlwind
18 posts
no avatar 4. JamesKim
11 posts
no avatar 5. dinh thaihoang
8 posts