High tensile bolts for flywheel?

**TTV8RA23** · 18-07-2010, 04:28 PM

I was going to suggest cap screws and i dont think washers are a bad idea after all look at the surface area on the underside of standard FW bolt versus the surface area on the underside of cap screws. Then again i guess your running steel flywheel which is alot better at taking said load than standard cast flywheel.
Never before have i seen a fly wheel that locates on the bolts alone that is just ridiculous

. And yep agree with justen. There should be no shear loading on FW bolts, the friction between the flywheel and crank face should be enough that it doesnt twist to give any shear action.
Cheers
Simon

**checksix** · 19-07-2010, 03:50 AM

I agree with JustenGT8. The main load on the bolts is in shear. The washer will help distribute load in tension but does nothing for the shear load so I see no advantage and an actual disadvantage. The bolt will be able to take the highest stress levels when the shank (unthreaded postion) interfaces with the lead thread champher of the crank. The washer moves this interface outward, and if it moves out enough the stress concentration is shifted to the thread root which is the weakest part. Stay with the OEM design, the engineer did his homework correctly. I use loctite as well.

**JustenGT8** · 25-07-2010, 09:34 AM

So i capitulated and used washers

http://www.toymods.org.au/forums/sho...=20585&page=73

Not 12.9, i hadn't heard of the spec he gave them but he's the expert and assured me they were up to the job? They were thinner than any 12.9 washer eg head bolt washers; i'd seen but survived the 72 ftlb torque up fine. I still got a good +15mm thread engagement too.

BTW the M8 clutch cover bolts were also high tensile (just 8.8) and torqued up to 35 ftlbs. No specs to go off so just done to a tightness that felt right? The toyota spec for a clutch cover is usually around 12 ftlbs but pissweak bolts and dowelled, which the Tilton is not. 35 ftlabs not too excessive?