Mountain Bike Thru Axle Sizes

Boost being newer isn t as much as a clusterfuck.

Mountain bike thru axle sizes. Old quick release hubs and 142 x 12mm thru axle hubs have the same widths between the hub flanges so there is no change in terms of hub flange positioning and wheel strength and stiffness. Determine if your frame fork uses a thru axle ta or skewer qr. Thru axles are commonly 12mm 15mm and 20mm in diameter. Using a tape measure measure inside width of frame fork where hub contacts frame fork.

In this example 15mm is the diameter 100mm is the o l d 127mm is the overall length and 1 5mm is the thread pitch. Skewers are almost always 5mm in diameter. They essentially operate the same as front thru axles on the rear of the bike. Early cyclocross bikes borrowed the 15mm front thru axle diameter but as disc brakes became more common on drop bar bikes they all standardized to 12mm.

Thru axles are also inserted through a hollow hub axle but they re bigger rear ones are 12mm in. Traditionally frames and forks had slotted dropouts. The diameter of the thru axle there are two common sizes. The hub axle which was 9mm in diameter.

Spacing on these is 142mm wide with an axle diameter of 12mm. Thru axle hub ta skewer hub qr step 2. Boost gives a 148 x 12mm spacing which allows for the hub flanges to be further apart which gives a potentially stronger and stiffer rear wheel. Front mtb thru axles currently use three standards.

15 x 100mm 127 length 1 5. The standard mtb rear axle dimensions are 135x5mm for a qr rear hub but jump and gravity bikes may use wider and thick axles for extra strength and stiffness with the available sizes being 135 10 142 12 150 12 157 12 and 165 12. 180mm length 20mm thread length. Most thru axles are described by four measurements and you might see them described something like this.

This is done via visual reference. 15x100mm 15x110mm boost and 20x110mm the first number refers to the axle diameter while the second refers to the dropout width of the bike. Thru axles make the bike stiffer which reduces lateral flex and results in better tracking especially through corners and at speed. Rear thru axle from my evil following uses a 12 x 142mm m12 x 1 5mm thread pitch shimano e thru standard.

Ensure your rear hub is the correct size to fit your frame. When mountain bikes first went to thru axles the standard was 12 142 which was the same effective width as the quick release hubs they replaced. A guide to mountain bike axle standards 1. Plus there are additional lengths for split pivot bikes and trek boost abp.