Mountain Bike Reviews Forum banner

Toe rub on my BMC 69er

1030 Views 3 Replies 3 Participants Last post by  red bank rider
So I built my own 69er early this year with a 2007 BMC Trailfox 01 frame and all the parts from Jenson and Price Point. My calculations for this build was based on the Trailfox frame normally takes a 130mm fork with a 26" wheel.
So The 29er Reba SL fork set at 100mm(max) + 29" wheel(1.5" increase = 36mm) = 136mm. So my 29er fork and 29" wheel setup would work fine since it wouldn't slacken the steep 71 degree HA.
Well all has been fine until I recently upgraded to 175mm SLX crank from a 170mm cheapo. (175mm is def the crank I need) Now that extra 5mm is causing just the slightest toe rub for me when i turn the wheel and my foot/pedal is cranking.

So what to do?
1) Don't want to go lower on the crank. perhaps a smaller tire? It's currently maxis ignitor 29 X 2.1. and a 26 X 2.1 in the rear.
2) my spd cleats are already set as far forward as possible in my shoe....Perhaps something I can add to the headset to slacked the Head tube angle just a wee bit?
3) Finally was considering buying a new 29er fork at 130mm or greater. I wouldn't mind the slacken Head angle at this point. Would the extra 30mm raise the bike high enough to offset this toe rub? I'm considering this because in case the wheel rub is still happening, I can just buy a 26" or 650B wheel, and I'll be back to the original fork/spec recommendations. And then I can use the original 29" wheel and 100mm 29er fork for my next 29er full build in the future. But if I'm told this extra 30mm won't even help, then I'll just scrap this idea too

Please help!

Note to others - be weary of 71 degree head angles, when adding a 29 to a 26 frame - you'll prob have the same issues as me
1 - 4 of 4 Posts
it sounds like your wheelbase is just too short for a 29er up front. jacking it up with a longer fork may not solve the issue, and will certainly make the geometry screwy. and as you said, changing your crank length is not a good way to solve the issue, the sacrifice is too great.

i would just go with a 650b up front and call it a day :)
yeap, what he said^^^ sounds like you need a frame with a longer top-tube/wheelbase, and if that's about the largest size bike you can ride, then a smaller front wheel....
Damn - so it seems like I'll have to be going with option 3. Start off with a 650B wheel in the 100mm 29er fork, see how the 15mm decrease feels - then most likely buy a longer fork in the future.
1 - 4 of 4 Posts