How to fit my 650b conversion + fenders in a 700c road bike?

[sirskialot22]

Hey there,

Looking for the least painful solution to my current non-issue issue: I built up a set of 650b wheels with 38mm tires to put on my commuter bike so I can put longer reach brakes on and fit fenders in as well. These are already a few mm less in diameter than the stock 700x23s, but even still, when I attempt to put the fender on, the tire still rubs the hardware on the bottom of the fender (tire is Panaracer col de la vie, fender is a SKS 45mm commuter). I'm contemplating going down to a 34mm tire, but there's only one real choice with gumwalls (the nifty swifty) in this size range, and I'm concerned about the BB being too low/geometry being off.

700x23 diameter is 668mm
650bx38 is 660m
650bx34 is around 652mm


This is for an early 90s bianchi forza with a unicrown fork. Thoughts?

[bicycletricycle]

make some fender splits?

[JAGI410]

Pictures could be helpful here

[Ed-B]

Originally Posted by sirskialot22

This is for an early 90s bianchi forza with a unicrown fork. Thoughts?

Unicrown forks are not ideal for 650B conversions.That could be the problem. If you can find a fork with a real crown and approximately the same axle-to-crown dimensions it's more likely to work. I've swapped out the unicrowns for one or two of my 650B conversions when they were the limiting factor.

Alternatively, if there's a lot of material under the brake hole on that unicrown fork you may be able to remove a bit to gain some extra clearance. Just don't grind out anything that's in the welded areas.

And yes, pictures would help...

Ed.

[FlashUNC]

[oldpotatoe]

Originally Posted by sirskialot22

Hey there,

Looking for the least painful solution to my current non-issue issue: I built up a set of 650b wheels with 38mm tires to put on my commuter bike so I can put longer reach brakes on and fit fenders in as well. These are already a few mm less in diameter than the stock 700x23s, but even still, when I attempt to put the fender on, the tire still rubs the hardware on the bottom of the fender (tire is Panaracer col de la vie, fender is a SKS 45mm commuter). I'm contemplating going down to a 34mm tire, but there's only one real choice with gumwalls (the nifty swifty) in this size range, and I'm concerned about the BB being too low/geometry being off.

700x23 diameter is 668mm
650bx38 is 660m
650bx34 is around 652mm


This is for an early 90s bianchi forza with a unicrown fork. Thoughts?

You mean under the fork crown? That's where it rubs?
Pics please.

[sirskialot22]

Will post some pics later when I can take a better photo. Thanks for the suggestions though, I was thinking a new fork might be ideal, and that dropping 8mm or so for smaller tires could be an issue.

[sirskialot22]

OK here we go. There's generous brake clearance (thanks tektro). And seemingly some room up top. But when I try to install the fender on the brake mounting location as high as it can be, the tire seems to rub the bottom of the fender. I can try to remount it again to show even more detail if that's needed. Perhaps I just needed a thinner fender (though these already seem a bit flimsy).

[rcnute]

https://store.rivercitybicycles.com/...ckets-4486.htm

Ryan

[Kontact]

Originally Posted by sirskialot22

OK here we go. There's generous brake clearance (thanks tektro). And seemingly some room up top. But when I try to install the fender on the brake mounting location as high as it can be, the tire seems to rub the bottom of the fender. I can try to remount it again to show even more detail if that's needed. Perhaps I just needed a thinner fender (though these already seem a bit flimsy).

Instead of trying to fit that hardware under the fork, put the bracket behind the crown instead of in front, which will allow you to get the plastic higher up under the crown.

If you test it out and it gives you enough clearance, you'll probably have to open up the bracket slot and get a longer brake mounting nut.

Alternately, drill the two rivets out of the bracket and remount it reversed so the bracket is under the caliper instead of under the crown.


Third possibility - move the bracket out of the way and drill holes in the fender that allows you to tie it to brake post up through the open bottom of the fork crown. Nylon cord or a zip tie.

[Billybob62]

Originally Posted by Kontact

Instead of trying to fit that hardware under the fork, put the bracket behind the crown instead of in front, which will allow you to get the plastic higher up under the crown.

You may also gain a little more room by using sheldon fender nuts:

https://www.rivbike.com/products/she...ender-nut-pair

[ergott]

You might need to cut the width of the fender just a little to allow it to sit higher under the crown of fork. It won't reduce its effectiveness. If the slotted tab is interfering with something preventing the fender from going higher than it can you can always chop the top of it off too. I had to do that with one build when it hit the headset.

[weisan]

I drill and cut up my fenders to fit tight corners and secure in odd places.

You will figure it out...just have to be brave and do it!

[sirskialot22]

Thanks for the feedback everyone. I will try some combination of these techniques this weekend.

[staggerwing]

Daruma bolt:

https://velo-orange.com/products/vo-...k-crown-daruma

This little doohickey fits inside the bottom of the fork steerer tube.

For extra room, replace that nut, which would be on the inside of the fender, with a sleeve nut.

https://www.amazon.com/Phillip-Alumi...words=aluminum