Reusing stretch bolts

[kamloopsmtbguy]

Hi Greg!

I just replaced the sprag clutches on my Brose Mag S from a Turbo Levo. I know that technically I should be using new stretch bolts, but I don’t have any, and I I’ve heard that reusing the original ones with some blue loctite should be okay once.

My question is, what torque should I use for this? When using new bolts, I think it’s 3NM plus a full turn for the long bolts and 2.5NM plus a half turn for the short ones.

Thanks!

 

[Greg Watts]

Hi Greg! I just replaced the sprag clutches on my Brose Mag S from a Turbo Levo. I know that technically I should be using new stretch bolts, but I don’t have any, and I I’ve heard that reusing the original ones with some blue loctite should be okay once. My question is, what torque should I use for...

@kamloopsmtbguy, you're becoming quite the Brose whisperer at this point. Sprag clutches, bearing depths, and now stretch bolts. I'm genuinely impressed.

I'll be straight with you: I cannot find the specific Brose Mag S sprag clutch stretch bolt torque specs anywhere in my data or online. The figures you've quoted (3Nm + full turn for the long bolts, 2.5Nm + half turn for the short ones) are more detailed than anything I can verify, so I'm not in a position to confirm or correct them. If those came from a Brose service document or from Performance Line Bearings, they're likely correct.

What I can say with confidence is this: if you reuse stretch bolts, do NOT torque them to the original specification. That torque + angle method is designed to take the bolt into its yield zone, and

once a bolt reaches its yield point, it has been stretched to a point it cannot come back from. Doing the full angle again on an already-yielded bolt is basically doubling the stretch, which risks snapping or insufficient clamping.

Reused TTY bolts can work if you torque them to the same value you would use for a normal bolt of the same size, pitch, and strength rating, but they will not hold as well as new bolts. Loctite is generally a good idea in this scenario.