billydscout

I know it may take some time with the frame alignment tools, but can one cold set a steel frame to increase the maximum allowable tire width? (I would love to build a 29 inch mtb on a vintage road frame)

Blue Order

Yes, you can cold set, although someone else will have to fill in the details.

However, keep in mind that mt. bike geometry is radically different from road bike geometry. 29ers are usually built for that purpose, as far as I know.

billydscout

I rarely ride a mtb, but would like to have the option of joining friends on trails that are beyond a cyclocross bike on occaison, just a thought.

Blue Order

I don't know whether or not this can be done, but I would check to see if a mt. bike frame can be converted to a 29er. That's all a 29er is, really-- a mountain bike frame with 700c wheels. Well, that's not exactly true, because the purpose-built 29ers have slightly different geometries, but it's true enough. So I would look into either buying a purpose-built 29er, or modifying a mt. bike frame. I suspect that "all you have to do" is adjust the brakes location. Somebody else will know more about it than I do... Maybe on the Mt. bike forum?

well biked

Nope, won't work. Even if you went to disc brakes, the stays are too short, along with the fork legs, on mtb's designed for 26" wheels to accept 29ers............And you wouldn't have anywhere near the clearance between the stays, fork legs, etc. on a road bike to accept a true 29" mountain bike tire. Sorry-

Grand Bois

I've seen it done. There was pleanty of room for 700c's on a mountain bike frame designed to accept huge knobbies. This bike had road side pulls installed. The only thing I didn't like was that the studs for the cantilevers were still there.

The frame has to be cold set to accept a narrower road hub. but that's no big deal. The special tools required are a 2X4, a piece of string and a ruler.

well biked

The OP said he wanted to convert an old road bike to a 29" mountain bike, and the next poster said it might be possible to convert a frame originally intended for 26" wheels to 29." I'll say again: can't be done, and I only listed a few of the reasons, there are more, particularly in regard to the road bike to mountain bike conversion.

edit: Dirtdrop, if you mean converting a 26" wheel mountain bike frame to use with 700c ROAD tires and hubs, then that's a different thing. But that's not what was being discussed.

Grand Bois

I was responding to Blue Order's post.

You responded that it won't work, even though you say that's not what's being discussed.

well biked

A 29" mountain bike uses 700c rims with knobbies just as fat as 26" knobbies. The name 29" comes from the fact that the outside diameter, with the fat tire installed, is appox. 29." A frame designed for 26" knobbies won't accept a 29" mountain bike tire. 29ers are becoming popular, the Gary Fisher brand is currently producing these, and they can be seen at any Fisher dealer. It's a stark difference when you put a 26" mountain bike tire/wheel next to a 29" mountain bike tire/wheel. The 29" bikes are very versatile, too, because you can install 700c road tires on the rims.

phoebeisis

The tires on this bike are 28.25" tall-700c 42-622-nominally they are 40mm 700c-ISO 42mm.They are very big for 40mm in that the carcass is roughly 41 wide and 42 tall-.
It took a bit of doing to fit this tire.I have-had-a french frame that would accept these tires by just shaving the tire lugs a bit.
It took a lot more to fit them to this frame.
1)Remove the screw adj from the rear dropouts
2)Grind a lot of metal off-about 5mm- 0.200" the the dropout so the tire will go rearward more.
3)Shave off the side lugs-then smooth them with sander.
4)It would now fit-at 35psi-with maybe 1mm clearance on both sides-wheels had to be perfectly true.
5)massaged the "dented" part of the chain stays about .020" .5mm on both side with a small maul-concrete block-steel barbell bar.It sounds worse that it was.I had to prop the barbell in place so it was touching the chainstay just where I wanted to dent it.I then hit it with the maul in a rat tat tat sort of way working it back and forth.
The fork didn't have enough top clearance-I will put a spacer in the dropout.
The brake bridge has maybe 2-3mm more clearance.The french frame had lots of clearance-it must have been designed to take long reach centerpull brakes.
If a 29" tire is actually 29" and over 2" wide it would be very difficult to fit it on a road frame.A vintage road frame-one that took long reach brakes-would be your best bet-but I don't know that you will find one that will actually fit a 29' tall 2" wide tire.
I checked my MTBs-the Y50 has about 1" more clearance with a 2.1 Nanoraptor(about 26" tall and 2' wide) so it could fit a 28" tall tire.Same story on NRS-28" max.
Your best bet might be to put a 26" rim on your road frame and use long reach brakes-90+mm reach.
I might do just this on this bike.The mods I did don't make it safer,and they might drop me in the street.
I think it would be a rare road frame that would take a 29" tall tire.There are a fair number of much shorter semi knobby tires that will ork-35-38mm range.Luck,Charlie

Little Darwin

It sounds like you are looking to tweak a road bike to become a Surly Long Haul Trucker or Cross Check... If so, I would suggest saving your pennies and buying one. Or are you looking to tweak a specific frame that you already have?

Cold Setting a frame is usually done to accomodate hub width. If the width of the seat stays and chain stays are too narrow near where the tire would be (on the seat tube end) I think it would take more than cold setting. it would potentially include either bending the stays or somehow moving the anchor points for the stays outwards. It would also potentially need modification of the brake bridge location and/or width. If possible this should probably be done by a frame builder.

If you are set on modifying a classic frame, definitely go for something with a touring geometry and not a tight racing geometry or you may have to deal with the seat post clearance as well.

merlinextraligh

+1. I don't think the Op was asking about hub width, but tire clearence, and trying to bend the frame to change this siginficantly sounds a little too radical.

cyclotoine

It is clear he was asking about tire width and of course the answer to the original question as stated is no. However the discussion has morphed into one about modifying road frames to fit larger tires?? In which case I would like to throw in my 2 cents, which may be less than yours because I am Canadian. haha I just dissed myself... rough.. anyway I have seen plenty 27" vintage frames (like my friends beautiful raleigh super grand prix, tange 5 tubing) that have nice long reach calipers that have just enough adjustment left that you cold throw on a 700c and some fat ol' tires. Even with the 27" there is lots of clearance and I suspect it is for older more bulky fenders. That being said your braking power would suck and you definately don't want that for mountain biking and there is the inevitable problem of mud and crap getting caught up in caliper style brakes. you can get posts put onto your road bike. The shop here will do it for 200 bucks (ouch!)... but if you are only doing occasional off road with no steep decents than maybe calipers will be okay. But then again I would just get a 29" MTB or surley if that is what you really want. These money saving build projects can end up costing more if you factor in your time etc...

well biked

The Surley Karate Monkey is another Surley the OP might want to look at, it's Surley's 29" mtb frame and fork. It has horizontal dropouts so it can be set up geared or as singlespeed. It also has a curved seat tube to keep the chainstays as short as possible with the big 29" tire-

Eatadonut

If you're willing to forgo 29" for 26"

If you find the right frame (for instance, this 1984 Trek something 531 frame I have), you can get lucky. I discovered almost by accident (I was tired, and trying to true my MTB's wheels, and put one in the trek frame), that it will take a 26"x2" in the front, and a 26x1.75" in the back, if there aren't extreme side knobbies in the back.

Brakes would be an issue, but you could fashion something that would work, I'm sure.

billydscout

The Surly KM is what I'm looking at, but don't have the $500, I do have access to multiple vintage frames I'd be willing to bend if it was easily done. At this point, however, it appears I'm better off saving my money. Besides, I just got a call from a local shop asking me to turn a crank on a part time basis, so I should be able to work out a deal. Thanks for your help.