I came across a thread in mtbr.com about some folks that put 700c on their MTBs. I thought it's an interesting idea. What are the factors to consider?

I have been looking at just that,,,I have a pair of Weinman concave, 700c rims w tires that would be real nice on my 80s' Raleigh Mountain tour steel framed beaste
The major problem that I see, is that the distance from the axle to the outer edge of the rim(no disc brakes) is an inch and a half or so more,,That will require moving the brakes up that much...There is enough room for the wheel , but moving the brakes looks like more, than is easily done....I will keep an eye on this thread to see what the experts have to say...
Bud

My fixed gear conversion started life as an entry level mountain bike. I did some quick measurements and found the front reflector mounting hole in the fork crown was exactly the right distance to fit a road caliper to a 700c wheel so that's what I did. (28 mm road tires) I don't have a rear brake but I think the seat stay bridge is about the right distance for fitting a road caliper also.

Biggest factor is clearance, and whether the brake mounts will reach.

Assuming the knobs the brakes are mounted to, were brazed on, is it possible to break out the acetelene torch, move them, and rebraze them in the right place???(Obviously a steel frame)..
Bud

The term "80's raleigh mtb" leads me to hypothesize you could have giant long reach caliper brakes made of stamped steel on what is essentially a fork designed for 27 1/4 or 700c wheels. upgrading to 700 c wheels in this case is easy, you just need some shorter reach calipers. I find old Dia compe brakes are cheap, plentiful and usually work on older low end frames....the only frames i have much experience with. you will probably want to measure the reach or something. my workshop is less than a five minute ride from the LBS with a big ol' selection of cheap used parts so if something isn't working its no big deal to find something that will, as opposed to researching everything down to the finest detail like some kind of nerd. for the record i just did this exact swap on my dump bike department store tandem, so it would, you know, STOP. Steel rims and chinese U- brakes are a scary enough combo on a bicycle built for one.

For the record: if the wheels are decent hook edge aluminum 26 ers and the bike has cantilever brakes(i.e. will not work with bigger rims), why not just get "skinny" road tires?

I'm about to slap 700c wheels and 700x35c cyclocross tires on a Scott Reflex mtb that originally came with 26" wheels. Disc brakes make the job easier. I checked frame clearance and there's no problem for tires up to size 700x37 or 700x40.

The resulting higher BB brings no adverse consequences, according to Dave Moulton's ideas, among others.

But changing the outer diameter of the tire will change fork trail. I'm waiting to try it out but I've still gotta build up the rear wheel first.

Mavic made adapter plates to move the brake studs. Look around the web and ebay and you might find a pair of them.

I commuted on a Specialized M4 Stumpjumper that had 700c wheels on it for about 8 years. Discs made the brake issues into non-issues. The 25mm road tires I used only raised the BB height by perhaps 1/4 inch over the knobbies that were on it when new. No handling issues at all.

What do you gain by the conversion? Speed? Is it significant enough?

the best you could hope for is higher quality, lighter faster wheels but by the point this would start making any truly noticeable difference you would be out of the price range of it making sense to put said wheels on a goddamn MTB. This is the kind of the kind of conversion you do when you have spare 700c's out the yin yang, multiple brakesets to play with(optional), and the modest technical know how to make it all happen. the sensible thing to do if you want a MTB that is roadworthy is swap the knobbies for slicks. mountain bikes worked fine for decades with 26 inch wheels opposed to 29's I'm sure an inch or so makes even less difference on the road.

That it would just be easier to get a 29er so you could put some mountain bike tires on? Easier to go 650b...

if the bike has brake studs. What about fitting v brakes. Then making er drop bolts. strong flat metal that has 2 holes in it. so one end in the brake pad slot. Other hole for the pad.

I wonder if the article the OP referrs to was discussing a "29-er" MTB which comes OEM with 700c rims, not converting a 26" bike to 700c.

Given that there is that Mavic brake adapter it seems like someone thought there were enough people sharing that interest for there to be money to be made out of it.

At the time I did my conversion in the later 90's there was no such thing as a high end lightweight hybrid with disc brakes. Apparently I started something though since Kona came out with their disc brake Dr Dew the very next year for about 1/2 the price I'd sunk into my own conversion.... GRRRRRR!!!!! Ain't that always the way? And yes, using the 700C wheels and tires did make the bike quicker than it was with the MTB wheels and 26 inch smooth street tires.

Altering the distance between the pivot and the pad wihout altering the distance from the pivot to the cable to maintain the ratio will totally ruin the leverage ratio of the system. What you are suggesting will make it so the brakes do not have anywhere near the same stopping power. The rider would need to greatly increase the effort at the lever to achieve the correct stopping power at the pads. Going from 26 inch rims to 700c is quite a jump. The lever effort woudl go from one finger comfortable stops to 3 or 4 fingers with white knuckles. And even that may not be enough.


Well this would be the easy one wouldn't it. No issues at all other than going for a narrower rim wheelset and then shoeing on some skinny tires. Although at least 90% of the advantage could be had with a 29'er by just shoeing on some 28mm performance tires in place of the knobbies. I'm running 29'er wheels with 28mm Conti Super Sports on my new cyclocross/touring bike. While there's no doubt that skinnier and lighter rims and tires would benefit the acceleration away from stops once rolling they don't give up much to the skinny and higher pressure stuff.

Isn't this how the "29er" trend came about? Most standard mtb frames have plenty of clearance, and the radius of a wide profile mtb tire really isn't much different from that of a typical 700C tire anyway.

well, thing is, the radius of a typical mountain bike tire is about 26 inches, hence the name. While that may be similar to the radius of your typical road tire, they are not similar to the circumference of your typical 29er tire. A 29er has a lot more volume to it than a 26er