Frame width question

So I’m looking at building up a 650b muni with one of the new fat tires and I’m looking for a frame that would fit it. So far looking through the forums I’ve found where nurse ben said his oracle 29 was 85 mm at the widest. I was wondering if anyone could tell me the spacing for other 29 inch frames. Obviously I can go the oregon route if nothing else, but I’m curious. I attached tire specifications from the tires I’ve had an eye on. The panaracer fat-b-nimble 27.5 x 3.0 is another choice but its not out yet. For those curious I am hoping to use a 55 mm rim from fatlab components, they said they can do 36 hole drilling if needed, still a pretty new company so we’ll see.


I am pretty sure I remember having mesured a KH frame at 88mm wide where the tire is (on a 26’’). I think the only wider frame will be the Oregon or Triton. You should ask Josh at UDC about the 29’’ Oracle. I know they fit the 29x3’’ Surly Knard tires but I dont know if it’s much wider than the 26’’ oracle.

I’d make you one, but I have to stop making frames for a few months :frowning: :stuck_out_tongue:

KH minimum as i know is 84mm almost some more cause it is minimum.

the new triton 26" 29" arrived yesterday and they have a minimum of 86mm, pretty close because we try to do as little tolerance as possible.

if you are a strong rider and you want to climb steep hills with short cranks you need ca. 5mm clearance each side otherwise the tire will rub the frame at 29"
thats because not only frame flexes but also the wheel and big wheel more than small. at 24" 3-4mm are enough.

short cranks cause much more flexing than long cranks.

note: even if the wheel is trued very good (<= 0.5mm ), specially wide tires may have an untrue of 2-3mm.
to avoid rubbing tire at frame mount the tire with max. untrue 90° rotated to cranks

cheers jogi

I figured they would all be about the same. Thanks for the info about tire rub, I figure I would need a frame around 96mm for the trax fatty… Which seems unlikely since bearing spacing would be 100mm. Does anyone have a Qu-ax 29 they can measure? If nothing else works I might try my hand at building a frame, I’ve been wanting to ever since I modified one for my 32".

One think I would mock up and check before brazing a frame together is how the width feels. You might need to go with a flat bar design to reduce the outside thickness of the frame, as you increase the inside width.

Sitting with some cardboard around a existing uni would make it easy to mock up the limits where it becomes an issue. It might not be a factor at all.

I have a Qu-Ax 29" here, the cr-mo version. It’s roughly 82mm wide. It fits a 26x3" Gazzaloddi tire. I’ve seen a 29x3" Knard also in it, but it did rub sometimes because it’s to narrow.

There’s always the possibility of modifying a frame, but it might make it weaker.

Well I guess I’ll be modifying something then, I think my best bet is going to be getting a drak frame and making dimples for tire clearance.

Seems like you won’t be the only one going down the modification road as somebody else modified a Koxx-One Track Monster frame.

If you can get your self an KoxxTrackMonster (think that was the name…) it does alright for 3.8 Tires without any altering.

That’s definitely an option. I did a quick search and it seems like it might be a little hard for me to find that frame in stock somewhere though. When I mentioned modifying a drak frame, I was just going to try dimpling it like shown in the picture below, I could probably get almost 10 mm clearance in each direction going this route. If I modify it that’s why I would want a steel frame. Does anybody have a drak frame to measure?


The oracle 29 frame is noticeably larger than the drak, both internally and externally. The max width of a drak is approximately 75mm to the oracles 85mm.

Due to the diameter of the steel tubing (or lack thereof), I don’t believe you would even be able to increase the frame width up to what the oracle provides without more drastic bending to re-curve the frame to your specifications.

Apologies for potato photo…


Well darn. I was hoping it would be about the same. Jakob, was the steel qu-ax frame you mentioned this one? If so I might try to work with that, after all it’s cheap. That or get more creative with my modification…