Overtorqued Flywheel Bolts--what to do
10-20-2006, 05:04 PM
#1
Teching In
Thread Starter
Overtorqued Flywheel Bolts--what to do Guys,
Installing a new flywheel (for new Textralia clutch), I tightened the bolts to 100ft-lbs.
Then, reading the torque for the pressure plate bolts, I saw that it was given in N-m.
I immediately checked the re-checked the torque for the flywheel and it was actually 100N-m not 100ft-lbs.
..And 100ft-lbs is significantly more than 100N-m.
These are Grade-8 bolts that I bought the last time I swapped flywheels a few years ago.
What is the best thing to do at this point?
Installing a new flywheel (for new Textralia clutch), I tightened the bolts to 100ft-lbs.
Then, reading the torque for the pressure plate bolts, I saw that it was given in N-m.
I immediately checked the re-checked the torque for the flywheel and it was actually 100N-m not 100ft-lbs.
..And 100ft-lbs is significantly more than 100N-m.
These are Grade-8 bolts that I bought the last time I swapped flywheels a few years ago.
What is the best thing to do at this point?
- Leave the bolts as they are and finish the installation;
- Loosen the bolts and re-torque them correctly;
- Remove the bolts and discard them--order some new ones;
10-21-2006, 01:02 AM
#5
Replace the bolts, they're cheap and there's a good chance that you've stretched them beyond limits. If they fail, the results would be way too severe to warrant not spending the money on new bolts. Torque specs are a ball park way of measuring bolt stretch. It's the bolts natural tendency to contract from this stretch that makes it stay in place, and provide fastening force. When you over stretch bolts, they get weaker, and don't want to spring back to their original size, and thus don't hold as well.
10-21-2006, 09:54 AM
#7
Torque specs are set by the physical bolt size, and is based on a percentage of their yield strength IIRC (undergrad was a long time ago at this point). If it was me, I'd replace them as they are cheap, and easier to replace while you have it all apart.
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10-21-2006, 11:17 AM
#9
Teching In
Thread Starter
Okay, thanks guys. Gonna replace those bolts.
And while we are at it, I'd like to suggest that we eliminate the use of the ft-lb in all documentation and instrumentation.
And while we are at it, I'd like to suggest that we eliminate the use of the ft-lb in all documentation and instrumentation.
10-23-2006, 10:55 AM
#14
6600 rpm clutch dump of death Administrator
Your feet and the back of your motor are too valuable not to make sure you have a good fastener. When a clutch comes through the floor it isn't good.
