I’ve seen this question asked a few times, and never with a definitive answer. Hopefully this will help anyone who encounters the same problem with fitting a 15mm axle into a Hope Bulb front hub.

The Bulb was released prior to the 15mm standard coming out and was designed for QR or 20mm. By the time 15mm axles came along the Pro 2 hub had superseded it.
However, lots of people have the Bulb, and it’s a solid hub, so why replace it if you don’t need to!

The Hope 15mm adaptors for the Pro 2 hub fit, but make the Bulb too wide and offset to one side. So you need to machine down one side to make them fit the 100mm spacing in the 15mm forks.
There is also a small collar on the inside of the adaptors that makes it stand out from the hub body on the non-brake side.

Pic 1 – adaptor fitted to the non-braking side, showing that it doesn’t sit flush.

Pic 2 – Machining the collar down by about 2mm.

Pic 3 – Shows the collar on the adaptor and one with the collar machined down.

Pic 4 – Adaptor sitting flush in the hub body

Pic 5 – Machining down the outer part of the adaptor. The spacing need to be 100mm on the hub. So check internally with vernier calipers and machine down to this size.

Pics 6 & 7 – the adaptor machined down to size, and with chamfers added as per the unmachined adaptor.

Great how to guide.

Cheers 😉 I finally bit the bullet and bought some new forks. A bit annoying that the 20mm standard has been replaced with something inferior IMHO. Again it’s a good example of the bike industry selling things that need multiple upgrades.
But, it gave me a chance to do some machining, so it’s all good!