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How do I know if I have a BOOST rear hub?

So you want to get some new cranks on your bike but you’re unsure if you need BOOST compatible spacing on your cranks. Getting the correct crank spacing is especially important now-a-days with two piece systems that you have almost no way to adjust the chain ring distance in or out. The front chain ring must align with the median chain position of the rear cog-set to keep the chain-line within optimal angle so not to affect the Q-factor… it just makes for a better ride if the chain-line matches up.

The first clue that you have a BOOST compatible bike and rear hub is if your bike has some kind of marking or sticker saying it is “148 BOOST” – usually on the chain stay. The second clue would be if it came with a 148mm x 12mm thru-axle. To make sure, follow the flowchart below to find out.

 

BOOST FLOWCHART

 

O.L.D. = Over Lock-nut Distance

FTF = Flange To Flange

DONT just assume you have a boost compatible bike and hub because you have a 148 x 12 thru-axle, the axle insertion depth into the frame may be fudged to fit a narrower hub into the frame.

There are EXCEPTIONS. You will encounter bikes with GNOT-BOOST from Surly or future-proofed thread attachments from Raleigh. These bikes have a non-standard 145mm frame width in the rear and accommodates a ±3mm margin by simply having some flex in the frame.

Raleigh even provides a thru-axel that is technically too long for the old 142mm standard and can actually support a 148mm hub (although it’s labeled 142 O.L.D. x 12mm). A thread attachment that is independent from the frame sits on the outside of the frame loosely to compensate for the change in torque angle when the frame flexes.

 

Posted in English, Sidetracked.


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