Hub Compatibility & Standards Guide

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Most questions we receive are about compatibility. Fair share of these questions is about standards that Trailmech hubs support. But there are many, which are about general understanding of certain technicalities. It is not because there is lack of information. Indeed, there are many sources of information around. But for certain relevant for hubs details, it may take extra steps to condense what is essential. In this guide we uncover specifics of various standards and related compatibility questions.

We regularly review this page, so you are welcome to check-in for updates and additions.

Table of Contents

1. non-Boost to Boost

2. What is Boost QR

3. Torque Caps inside-out

4. 110×20 vs 110×20 Boost

1. How to convert non-Boost to Boost

Boost 148, Boost 110 or simply Boost has been around for quite some time. Quick recap on why did come on existence: the 29” wheels. Wider flange spacing for stiffer and stronger 29” builds. There are plus 10 mm of spacing for front hub – 110 mm. Hence Boost 110. And plus 6 mm for the rear – Boost 148 (141).

Alternative is to take the new measures from the centerline to any of the sides. That is plus 5 mm for the front and 3 mm for the rear. Sounds simple. But how exactly to convert to Boost from classic, non-Boost hubs? At first it seems simple. Why not to compensate for that added space by special end caps? Even that this approach defeats the purpose of Boost at first place, let us dig deeper here.

Boost is not only about the Over Locknut Dimensions (OLD). The rotor mount placement is different. The variation is: 5 mm for the front and 3 mm for the rear. Mounting appropriate shims can work, at least technically. But something else changed as well: the chainline. From 49 mm for OLD 142 mm, to 52 mm for Boost 148 (141). Special end caps will not help here. They do not alter the position of a freehub. And this is the case with new 52 mm chainline.

Note the use of another reference to Boost 148 in the parentheses above – 141. This is also Boost, but the different type – Boost QR.

There is neither a conversion kit for classic 142 (135) mm to Boost 148 (141) mm – rear, nor for classic 100 mm to Boost 110 – front. These are different hubs. Although, they have common parts within their model group: freehubs and end caps.

2. What is Boost 141 or Boost QR?

Trailmech XC Front End Caps QR, legacy
Trailmech XC Front End Caps QR, legacy

Boost 148 for the rear hub requires a 12 mm thru axle. Several bike manufacturers established that there must be a different option out there. We would not call it a better one, because it is not. And so, we got Boost 141, or Boost QR. Sometimes also referred to as Boost 141×9, which is not precise definition.

Instead of using the 12 mm axle, it uses 5 mm legacy rod and same legacy end caps. The forgotten 135xQR is “resurrected” with a new name. Just add the 6 mm difference in the over dropout length and here you go – 141xQR. By omitting the support of genuine 12 mm thru axle, designers brought back the open dropouts. And by doing so, created a backdoor to yet another legacy tech – 10 thru axle option. Someone may recall the “thick” QR – 135×10 thru axle. Indeed, it is exactly the same concept, just 6 mm wider – 141×10 thru axle.

Trailmech Rear End Caps QR
Rear end caps, left to right: Enduro 141×10 thru axle, XCR 141xQR

The 141×10 is an aftermarket solution, aiming to address the weakness of the 141xQR. The 5 mm QR’s rod fits into the end caps. But hub’s own axle has an internal diameter of 12 mm. There is no attachment between the two. The 141×10 mm thru axle fits the end caps in the similar manner. At the same time, double the diameter cross section offers way better stiffness. Besides, any open dropouts frame accepts it – no modifications required.

Yet only the 12 mm thru axle fits inside the hub’s own axle and not the end caps. It provides 17 mm “effective axle” that supports the bearings of the hub.

Trailmech XCR rear hubs supports 141xQR. Enduro rear – 141×10 thru axle.

The only good thing about Boost 141 that it is convertible to Boost 148. It is only end caps that differ between the two. That is from hub’s perspective not the frame.

3. Do Torque Caps make a difference?

Trailmech Enduro Front End Caps
Front end caps, left to right: 110×20 DH, 110×20 Boost, 110×15 Boost, 110×15 Torque Caps

There are many riders who considers the SRAM Torque Caps as a superior interface option for the front wheel. It is SRAM’s proprietary tech and it has been available since 2016 for Rock Shox forks only. The message is that it makes the interface between the fork and wheel stronger and stiffer. That is because of the larger contact area between hub’s the end caps and fork’s lowers. Torque Caps visually eclipse the standard end caps. Indeed, the solid, beefy design, creates an impression of delivering on its promise.

If only the wheel’s attachment to the fork was about the end caps. Yet, it is not. It is the axle that joins the hub and thus the wheel, and the fork. The axle requires precision manufacturing to ensure correct fit of the bearings. Same goal of the proper fit with hub’s axle and fork’s axle drives end cap manufacturing tolerances. These measures are both internal, though. You won’t notice them, unlike Torque Caps contact area. Why should you? As long as fork’s axle slides in, as it should. And the end caps remain solidly attached to the hub.

What about stiffness? By the definition it is measure of deflection caused by the applied load. The contact area plane that Torque Caps is all about, is right angled to the axle. If this contact area to start carry the load – it means that both hubs and forks axles went “busted”. And both have deflected to such extent that the load has propagated to the next element end cap’s contact area. Considering the fork’s 15 mm thru axle alone, it is difficult to suggest what sort of riding conditions would have caused it. And that is without throwing in hub’s own axle into the equation.

In our view Torque Caps is nothing but visually appealing option. A heavier one than it is necessary. With restricted compatibility to the single manufacturer’s suspension forks.

4. DH Spacing: 110×20 vs 110×20 Boost

Topic where confusion still exists when discussing front hubs for Gravity. And that is because the way we refer to identification of hubs type and application. There are two components: a) width and b) axle diameter.

Historically there was only 110×20, or just 20 mm front. Classic Downhill rigs for 26” wheels. Then the Boost arrived and it came with the same width of 110 mm. The flange spacing is different, though, as the Boost is for larger, 650b and 29” wheels. You do not get to see flange spacing stated in hub’s description. The Boost designation is always there for compatible hubs.

Flange spacing impacts the stiffness and strength of the wheel. The width did not change – 110 mm, so it should be possible to use “older” 110×20 hub with newer 110×20 Boost fork, right? No, and for the same reason why it is not possible to convert from non-Boost to Boost. The rotor mount position is not the same. It is 5 mm farther from the center of the hub. Thus, 110×20 Boost hub shell is different: wider with altered rotor mount placement.

End caps are incompatible as well. Check the Enduro end caps photo above: leftmost – 110×20 DH, next to the right from it – 110×20 Boost.