Which bike? I think the axles are different depending on the bike.

@@CyclespeedTours hello, its a tarmac sl8.

@@OscarFacuseh Mine were a gift, so not sure if specifically for the SL8, or possibly an early version. There is now a new version with a Ti insert in the hex head. But whatever, the SL8 requires a conical washer for sure.

Not sure I would agree with all of that. This component certainly does meet the engineering definition of an axle. "An axle is a central shaft that supports rotating wheels. On vehicles, the axle can be fixed to the wheels and rotate with them, or fixed to the vehicle with the wheels rotating around it." The wheel bearings are in direct contact with the axle. Yes it is also a bolt that squeezes the whole assembly tightly together and this should be tight enough to ensure no movement whatsoever. Remember the old days of QR skewers, where you just felt how tight you pushed the lever? Torque was therefore highly variable, depending on who did them up. But I agree that the clamping force should be high - higher than most would think. Although the 15Nm that Specialized mention seems very high - my Spesh LBS barely put 6 or 7 on mine.

​@@CyclespeedToursyeah I am sorry, but you should do more research on that. Peak Torque also has a very good video on this topic. As an engineer, I can tell you that your understanding is not correct. 99% of hubs have a hub axle on which the bearings sit. This axle is larger in diameter. Your thru axle is literally just a bolt that runs thru the hub axle that should provide clamping force. No radial load, no contact with bearings. A quick release is usually M5×0.8 which will generate roughly between 4000 and 6000 N when you do the bolt calc with the shimano specified torque. With a good lever you will be also in the region of 4000N. To get this with a M12 bolt you need at least around 10 Nm. The 15 from Specialized seem very reasonable if you wanne benefit from higher stiffness with through axles and are complete inline with a DT thru axle calculation

@@MS-bw7yt OK, point taken re. the thru axle, I had overlooked the fact that the wheel has it's own hollow axle through which the thru axle bolts. However, I'm not sure that most riders are aware of a torque recommendation for their thru axle, assuming that they even have a torque wrench and one that goes over 10Nm. (Most smaller bike ones don't). Factor specifies 12Nm for the Ostro. Anything over 10 is pretty tight and I know 2 LBS's that for sure don't do it that tight, and most riders I know don't either. So I guess the question would be, what are the consequences of a too loose thru axle? I rode my Ostro for almost 3 years, with no issues, tightened 'hard' but probably less than 12. If you puncture and have to remove the wheel, you would need a pretty decent allen key (not multitool) to actually release the thru axle if torqued to 15. The Overfast have a recommended torque of 9Nm and they seem to be working well in a variety of bikes.

This is true, and is a surprisingly high figure. My Spesh LBS torqued to around 7, no issues, and I was doing 8 or 9, again fine, before I read that 15 spec. These Overfast are rated at 9 max although tested to 19. I don't forsee any issues.

If you do the bolt calculation 9Nm with an M12 bolt will only get you in the region of a mediocre quick release. Lets say 3500-4000N of clamping force. QR are usually M5 thread. 5-7Nm on a M5 bolt are not comparable with 5-7Nm on a M12 bolt. I wouldn't use a thru axle with anything less than 10Nm. 15 Nm makes much more sense.

just a question here, 15nm torque will not compromize the hub bearings?

@@iamtotie short answer: no

Maybe read about their testing protocols? You think Formula 1 doesn’t depend on carbon parts?

It has a titanium insert. It's so light, but I think it's durable.

@@czts4778 Why not just make the whole thing Titanium then. It's not like anyone can see the carbon once it's inserted. What's the difference in weight going to be, one gram? And by the way, it's not doing a damn thing to make the bike faster. Why buy it?

Composites are around 30% lighter than titanium. If you want to reduce the weight of a bike you have to look at every component. That said I wouldn’t run these. The shear forces are too high for a composite. If they did fail the result could be life changing.

@@gweflj I would agree that an axle failure is something that you definiteyl don't want, but then neither would I want a handlebar, stem, frame, seatpost, saddle rail or spoke failure either, all of which are carbon.