Cannondaleriders

Just a thought. How many people having problems spinning flywheels are using impact guns? If using an impact gun you can and more than likely will overtorque. This will cause the metal taper to spread out and expand in the aluminum causing to seperate. Best way to install is make sure both tapers are clean torque to 35 ft/lbs and use blue loctite.

I've always used an impact gun to remove/install flywheels. I've never spun a flywheel on my bikes (both pinned flywheels), but have started to lose a pinned flywheel on one of my quads (did not actually spin, but the pins were working out).

I mostly ride my X440s, but it's fair to say I ride the quads with equal zealous (read: "Beat the piss out of...)

Interesting theory but the tapered part is not in near the aluminum area . The threads for the removal tool are. I have some hubs I could torque down and check the expansion on.

Update. I just setup a hub on the bench . going in steps from 20 ,30,40 50 ft pounds and then as hard as my 3/8 impact could torque the nut there was no change in the hub OD where the aluminum is surrounding it. The shank end did hower did expand .002" when really cranked down on.
Of course the teeth are what keep the hub from spinning not the center part.

I think that lapping them in with valve lapping compound just like you would a valve is well worth the few minutes it takes. Just a little off on the taper of one or the other and the thing will wobble which would stress it at the joint. Maybe they wobble themselves a little loose at the teeth first and that multiplies to cracking which leads to spinning.
Just my theory tho... Have not had one spin yet but I am still not quite in the 50 hp club just yet!
Ray

Agreed. Lapping lightly with fine paste and cleaning spotless will help the taper to engage cleanly. Fitting a warm flywheel to a cold crank will help too. Torque before the heat dissipates though or you won't benefit any.

For me the separation is due to torsional vibration. Those forces are massive at high rpm. I think the more recent increase in flywheel failures is due in part to the alloy part getting a bit age-hardened. Even the 'new' flywheels have 01 manufacture dates on them.

The impact of a torque gun causing torsional acceleration might not be helping though for sure.

It's not going to be an issue with the one piece flywheels though.....

It's not going to be an issue with the one piece flywheels though.....

Agreed, biggest problem is the 2 piece design.

......better get my finger out the eh?

Guilty, I use air gun,and spin them also..

Would this .002" be equal all the way around? Just wondering if what you mean by "shank end" would be the tapered part with the keyway slot. If so, wouldn't the keyway slot cause the expand rate opposite the slot to be more? It may cause a wobble.

A few years back I would still remember which was which, but I do know you can Static or dynamic balance. Both would take out radial vibration. on something as narrow as a flywheel it probably doesn't matter as much, but if you tweak it out enough it might be a factor.

Also it seems to me the quads have a bigger problem with spinning flywheels than the bikes, if this is true the key to the problem might be found by looking into how they differ

We quad riders are more committed......