Technical FAQ: SRAM AXS Flattop chain compatibility, hub bearing adjustments, and hydraulic brakes

VeloNews technical expert examines brand cross-compatibility of brakes and drivetrain components.

Photo: Ben Delaney

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Have a question for Lennard? Please email him at to be included in Technical FAQ.

Dear Lennard,
Do you know if a new Shimano 12-speed cassette is compatible with SRAM AXS road with the Flattop chain? I ask because I upgraded to AXS this summer and was initially told by one of my wheelsets manufacturers that I could swap the freehub body from Shimano 11 to XDR. Turns out, I cannot on this particular wheel. Now with Shimano also moving to 12-speed and the ability to run the 12-speed cassette on the 11-speed freehub, I’m wondering now about the possibility of continuing to use this wheelset with my AXS.
— Kevin

Dear Kevin,
No, that won’t work. The AXS Flattop chain has bigger rollers than standard chains, and they won’t drop down into the tooth valleys in a Shimano or other, non-AXS cassettes.
― Lennard

Dear Lennard,
I have a pair of 27.5-inch DT Swiss wheels with DT Swiss 350 hubs. The rear wheel works great and spins freely, but the front is giving me headaches.

I would like to use the wheelset as my gravel bike wheels on my road bike. The front wheel has a 15x100mm axle and so I have DT swiss 15 to 12mm conversion endcaps for my 12×100 mm road/gravel fork.

Here is the issue: Even without the conversion end caps and on my mountain bike with a 15×100 fork, this wheel when tightened to normal forces will not rotate more than two rotations. When I back off the axle tension it will spin more but nothing compared to my other wheels on the same bike.

I have tried other wheels on the MTB and on the road/gravel fork I mentioned above, and I have the same results. The DT Swiss wheel, when tightened to the same tension as the other wheels, will not spin more than a few revolutions.

I have replaced the bearings, but that did not help on either the MTB or road/gravel bike set-up.
— SR

Dear SR,
It sounds like the inner sleeve is too short or the end cap(s) is (are) too short.

Inserting a thin washer exactly the size of the end cap between the end cap and the inner sleeve would fix it.
― Lennard

Dear Lennard,
That worked. I did not realize that I needed the sleeve with the conversion end caps.
— SR

Dear SR,
Yes, there always has to be a way to support the inner race of a cartridge bearing from the inboard side when pressure is applied to the inner race from the outboard side. Otherwise, it will bind up, as you experienced, and it will wear out rapidly.
― Lennard

Dear Lennard,
Although I enjoyed your Q & A posted today about Campy/Magura/Shimano hydraulic brake mash-ups (I’m building one myself at the moment), your response posted only addresses the compatibility of the seals and brake fluid (mineral oil) and the fitment of the components. Although having your seals drying up/tearing/failing is critical, it is only a small part of compatibility between the brands.

No mention was made of the different caliper and master cylinder piston diameters and strokes, the master cylinder leverage ratios, the pad area, and the coefficient of friction of the pad material. The only constants when swapping these components between brands will be using the same size and brand of rotor and using the same pad compound from an aftermarket pad company like Galfer, EBC, DP, Alligator, etc.

Unfortunately, since there are no bicycle brake dynamometers for use by magazine editors like yourself to come up with objective data, any performance improvements (or performance decreases) are completely subjective and come from perception. Feel free to post this as a response on the VN page if you like; this kind of mixing and matching of components in the motorcycle world is precisely what I do for a living.
— Andy Schwartz (formerly bicycle division director of Galfer)

Lennard Zinn, our longtime technical writer, joined VeloNews in 1987. He is also a custom frame builder ( and purveyor of non-custom huge bikes (, a former U.S. national team rider, co-author of The Haywire Heart,” and author of many bicycle books including Zinn and the Art of Road Bike Maintenance,”DVD, as well as Zinn and the Art of Triathlon Bikesand Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.” He holds a bachelor’s in physics from Colorado College.

Follow @lennardzinn on Twitter.

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