Hi all,
I’m new to bicycles; and just got an ebike for commuting. I recently also got a free SRAM flight attendant fork. The only problem is that the fork has a width of 115mm and my front tire has a width of 100mm.
Now, I might be new to bikes, but I am an engineer and a hobby machinist with a lathe. So my first thought was just to machine some 7.5mm spacers to go on either side of the wheel; noting that i’ll probably have to make a new bracket for the front brake as well.
My mental model of the forces would say that all the weight would be transmitted through the axel. Now the new fork does have a little but of a lip to it; which normally would probably transfer the force directly into the bearings on the wheel itself, but then they too would transmit it to the axel; just at a different point.
Anyway before I brake something expensive or miss something obvious I thought I would ask here.
Thanks!
115 is an odd fork width. I think you mean the fork is spec'd to fit a 15x110mm "Boost" hub? And the hub on your front wheel is 15x100mm.
If that's the case, you can definitely adapt the hub to fit the fork. You need two axle spacers, a 15x110mm axle, and a spacer to shift the brake disc into the correct position. Problem Solvers actually sells the spacers in a kit...
For 6-bolt brake discs: https://problemsolversbike.com/products/booster-front-hub-spacing-kit-6-bolt
For center lock brake discs: https://problemsolversbike.com/products/booster-hub-spacing-kit-center-lock-front
The real question is: where tf did you get a free Flight Attendant fork?!
Edit: if you really want to go down the rabbit hole and design your own spacers, SRAM publishes everything you need in their frame fit specifications:
https://www.sram.com/globalassets/document-hierarchy/frame-fit-specifications/road/2024-road-frame-fit-specifications.pdf
Aha! the 100 and 115 numbers were jot kine, measured the new fork and is 108.64 so you’re probably right that its the boost vs not thing. Was thinking i would have to make a new bracket myself for the brake so that would be cool.
As for how I got it; was gift from husbands sibling who had gotten one hadn’t gotten around to installing, but is moving to non-bike conducive area. Just mentioned it to try and head off comments that I should return it for something that fits haha.
Thanks for the great info! I’ll give one of those kits a try!