Can I Add A Spacer To The Chainring Bolts To Adjust Chainline

When installing a new or replacement threaded external lesser bracket onto your wheel, it'south important to get the correct number of spacers on either side . Whether you're running a SRAM GXP, SRAM DUB, Shimano Hollowtech Ii or any similar design, read on to find out how many spacers you should run.

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[Updated 13th January 2020 with SRAM DUB]

The kickoff thing y'all'll need to do is to measure your bottom bracket shell of your frame. As in the picture show below, the best way to practice this is with a gear up of vernier callipers, but you lot can also use a steel ruler or record mensurate. Manifestly, the erstwhile lesser bracket will demand to exist removed to practise this and you lot should measure from the edge to edge, so if you're not using callipers, stick your ruler inside the vanquish and so that any chain guide mounts or similar don't skew the measurement.

You should now know how wide your bottom subclass shell is. For a threaded bottom bracket, there are only 3 common sizes; 68mm, 73mm and 83mm. If your bottom subclass shell measurement isn't very close to one of those, you've probably measured it incorrectly - or something very odd is going on with your frame.

The beat out width determines how many spacers you lot need on each side, but it also depends on which brand you lot're using.

For 68mm and 83mm Shimano HTII bottom brackets

A 68mm or 83mm bottom bracket shell needs two of the 2.5mm spacers on the drive (chainring) side and one two.5mm spacer on the non-drive side.

For 73mm Shimano HTII bottom brackets

If your bottom bracket shell is 73mm wide, you just need one 2.5mm spacer fitted to the bulldoze side.

If you need to use a bottom bracket mounted chain guide or derailleur, so y'all'll also need to remove the innermost 2.5mm spacer on the drive side - so a 68mm or 83mm shell will have ane bulldoze side spacer and ane not-drive side spacer, while a 73mm beat will need no spacers at all.

For SRAM GXP 73mm bottom brackets

You don't demand to install any spacers onto the lesser bracket if you take a 73mm shell.

For SRAM GXP 68mm lesser brackets

You'll demand to use both the provided ii.5mm spacers for a 68mm shell, placing one on either side of the bottom bracket.

For SRAM DUB 73mm bottom brackets

Much similar GXP, you don't need to add any spacers to the bottom bracket if you accept a 73mm shell, but you lot will need to add a four.5mm spacer to the right-hand side of the creepo axle, unless yous're using a chain guide, in which case a 2mm spacer is required instead, along with a two.5mm spacer on the correct-manus side of the lesser bracket.

If your bike has Super Boost hub spacing (157x12mm) and a 73mm vanquish then yous'll need a four.5mm spacer on the left-hand side of the creepo beam, a 9mm spacer on the right-hand side of the crank axle and no spacers on the bottom bracket.

If you're running a chain device with your Super Boost setup then you'll demand a two.5mm spacer on the right-hand side of the lesser subclass and a 4.5mm spacer on left-hand side of the crank beam and a 6.5mm spacer on the right.

For SRAM DUB 68mm bottom brackets

Again, DUB 68mm is only like GXP, with a 2.5mm spacer needed on either side of the bottom bracket crush. You'll too need a 4.5mm spacer on the right-paw side of the crank axle.

Easy eh?

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