CrowSeph

Hello. Has anyone ever modified a steel roadbike frame to fit 29x2-20/2.30 tyres?
I have an old frame, not valuable so i can modify it. The idea of a custom gravel seems cool...
Has anyone have done it? (or know who has done it? or maybe a video or a link?)

unterhausen

I could if I wanted. I have thought about this a lot because I want to change a '80s Italian racing bike to a randonneur. Of course, the tire problem isn't quite as bad. The problem with 29x2.2 tires is that you have to fit the wheel and chainring in. So either needs longer stays or some fiddling. The other problem is you don't get the geometry you want, unless by some miracle you find a frame that is very unusual. Fitting a tire in a fork is going to mean a longer fork, so you'll have a very high bottom bracket or a very slack headtube or both.

I don't mind relatively long stays, so the big problem for me is the fork/bb issue.

I suggest considering 650b. Also, 700x50mm tires don't require a lot of changes other than the chainstays.

CrowSeph

Very interesting!

elqsigue

Hello, I have a frame from a mtb from the 90s and I also tried putting 29-inch wheels on it, but it is not highly recommended because the wheel needs tolerance in the frame, I went back to the 26-inch ones

tangerineowl

Been looking into getting something new fabricated in steel like this for a while.
More of a horizontal top tube, old school racing frame look, that would normally run a 29x2.2 slick, up to a 2.6, but most likely as a disc frame so I could drop the wheel+tyre weight by using light and wide enough carbon rims.

Have been reading on a frame building site that it seems a 3d printed chainstay yoke is the best idea to keep the chainstay around 420-430mm and still be able to run a tyre that size, along with a road 2x q-factor crank [possibly using a T47 shell that takes a 68mm -internal- bb and spindle].

I do realize the front end needs to be pushed out when considering toe overlap, but I'd be ok with some when running the 2.6.

This is the kind of frame look I'd be chasing, just with the monster tyres
https://theradavist.com/how-to-burn-...s-brest-paris/

https://www.flickr.com/photos/795686...n/photostream/
Somewhere in the flickr site, there's a Cirque owner who also has a pic of a european? Dancelli cx/road? frame that has 29er? tyres fitted.

Steve B.

Couple of issues. Can you squeeze an inflated tire past the brakes, if you have side pull, big issue. V’s or canti’s, a bit easier. Then what’s the clearance like at the top of the fork ? And at the chainstays. Then sometimes an issue where the front derailer will hit the tire when the chain is on the small ring.

Usually your limit might be somewhere in the 32 to 36 mm tire size. On my road bike with side pull brakes, I can only fit a 25mm tire due to lack of clearance at the chainstay. With more modern bikes with disc brakes, they often have much more clearance. My disc equipped gravel bike will take a 45mm. Possibly if I used 650B wheels I could squeeze in 2” tires.

unterhausen

My gravel bike is going to run 650b x monster tires, or 700c x 44mm. Seemed to me to be the best compromise. I hate the idea of yokes, admittedly for no good reason. Okay, the reason is I'm cheap. I also don't care about short chainstays.

duanedr 

I'm with Unterhausen that I don't really like yokes - especially the bent metal ones. They just don't seem right. I don't think a couple extra CM of chainstay length is noticeable enough to justify them. My opinion on this doesn't really matter, other than you won't find them on my bikes -yet. Printed parts can be pretty expensive still ($1/gram and a yoke I have a couple samples and they are about 160gm each) and it seems they are often stainless which is trickier to work with. I'm certainly not an expert on it and it changes fast so, wait 5 minutes and I might not have a point!

I think you can probably get past the chainring clearance by going to 1x, the yoke idea will work (with the expense mentioned) you can find parts to make a fork work (1" steerer would be a deal breaker for me; others might not care about their teeth). The BB problem can prob be dealt with. Suitable wheels will likely be thru-axle so you need to replace the dropouts in the rear and probably need to add disc brakes.

It would seem fairly easy to go down this path and end up with a bike that is either un-rideable or not fun to live with. At this point, you might as well start with new tubes and parts and make a bike you really want that will be up to the task.

unterhausen

I think we talked OP out of it. The thread got resurrected by someone who wants a new bike.

Andrew R Stewart 

I have a yoke I will never use, I tried making my own and didn't like that either. There are some out there I do find myself attracted to for various reasons, but I don't push the tire width spec too much so haven't sought out other premade yokes after my experience with the clamshell Paragon I still have collecting dust. Andy

duanedr 

I just wanted to make sure the OP was REALLY convinced... I didn't check the first post. My bad.

I got a couple samples of printed yokes that are really nice and solve these problems but they are expensive still and require other work that make them a challenge in other ways. I do think there is promise for printed parts. I don't have CAD skills so they will remain beyond my reach for now.

unterhausen

Someone in C&V found a site where you can get things 3d printed fairly cheaply as long as you don't ask for too much. I had a lug design in the works, but never finished it. I haven't really been tempted to use a yoke, but it would be interesting to design one.

duanedr 

Another builder sent me a few samples of the 3d printed yoke they use and it's certainly interesting. These were designed for TIG and are stainless so they'd need some re-work for brazing. They quoted $1/gm and the ones he sent are like 160gms so, that's still pretty steep.