I'm thinking of putting some old 700cc wheels on the mountain bike that i use for commuting. its all single speed so that should be ok, but should i anticipate other problems except brake reach (solved by some old caliper brakes surely) and rear hub spacing? any ideas/ experience?
neil

the hub spacing's gonna throw your chainline off, and if your mtb has a suspension fork, you might have problems with your tire hitting the arch. are you sure the mtb frame and frok are drilled for roadie brakes?

Also, your bottom bracket and standover height are gonna go up about an inch and a half, so be prepared for pretty different handling characteristics

why are you wanting to do this?

i have some 700cc wheels hanging about and too much spare time. also mtb has rigid front forks so should fit ok. should'nt bigger wheels make me faster?

Riders I know that have went with larger wheels on MTBs have had favorable reports on speed and ride quality, and I am considering doing this myself.

I have a gigantic amount of room in the suspension forks that I've used, big enough for at least 700x36 tires, but this varies from model to model.

Not sure about your hub and brake setup issues since I've only seen it done with 700C rims laced to disk MTB hubs.

Although the ride height, based on the rim, is going up 32mm, in practice I'd probably be using a much smaller tire.

Hi! I was wondering if I could get your opinions on something, particularly if you've done it yourselves.

I have a 2004 Trek 8500 mtn bike frame that I've been trying to sell. It's light and stiff and goes like stink, but nobody really wants to buy used hardtails anymore. So, I just had a thought - what if I slapped on some 700C disc wheels, a rigid disc cyclocross fork and a drop/bullhorn bar, replete with road disc brakes and made it a singlespeed? Is this just TOO nutty or what? I think the positioning on the bike would be okay [it fit great before I tore it down], and the axle-to-crown length on the fork should be the same or less than a 80 mm suspension fork, slightly increasing the head angle.

Any potential pitfalls or perils?

The wheel size difference isn't much, when you consider how tall most MTB tires are. There's a kit called the 6 to 9er somewhere that lets you do just what you're proposing. It includes a set of adapters for your canti brakes. You could also throw a 700c fork on it for the front and put a caliper on the rear.

nneeiill: I wouldn't say it'll make you any faster unless you run the same toothcount cog as you had on your 26"er, pedal the same cadence or close to it. If you don't do that, you're just giving yourself weaker wheels and brakes, and a rougher ride with skinny tires. You could get the same speed benefit by buying a smaller cog and skinny 26" tires (and pedaling the same cadence you pedal now). You'd keep your low center of gravity and stroger brakes.

I contemplated the same thing,
but it didn't work out for me (the mtb was large in the first place, and 700c wheels made it waaay too tall)
this thread should be helpful, however
the title is a misnomer, 650c isn't exactly the 26" wheel we were converting from.

Maybe, but fast riders are still fast and slow riders are still slow. I'm kind of in the middle...meaning that when I ride with slow riders they can be on their modern road bike and I'll ride my MTB with slicks and we're both happy. When I ride with my really fast racer friend, I ride my road bike and he rides a mountain bike with knobbies. He still has to wait for me to catch up...

The problem for me is not one of gearing, it's that super-skinny 26" tires give a harsh ride, mostly because the wheel diameter is so low.

Suspension partly mitigates this, but the smooth ride of the 700x32 wheelset on my cross bike is too appealing to ignore.

Don't know if this applies or not, but Mavic makes the Speed City 700C disc wheels specifically designed to mount 700c X 20 on a mountain bike. Having disc brakes makes this a lot easier mod, though.

Any idea where to find one of these "kits"? I've thought about doing the same thing with an old Schwinn Paramount MTB in the garage (switch from 26" to 700c) but the brakes are about the only thing prohibiting me from moving on the idea.

Google:
https://www.dreambike.com/69.htm

You can also probably find some info here:
https://twentynineinches.com/

My BBU and F600 are basically the same bike with 700cc and 26" wheels,respectively. The 700/MTB geometry combo works quite well.

I have a nashbar steel frame that I put 29er rims on (basically 700c mountain rims) I didn't want to worry about the reach of the brakes so I went with disk brakes and a rigid front fork. That made a difference in speed and ride, the other thing I changed was I put on a 48/38/28 trekking crank. I can usually keep up with the guys on there road bikes on my way to work, and the wider tires make it a really smooth ride.

I have also added a rack and bags since I took this picture.

I am trying to sell my SASS but this looks very interesting. Now to convince the wife I need 700cc wheels, hmm.

Wouldn't simply a slick tire in the same width as the ones you currently ride be easier?

BTW, we have four Neils posting to the Clydesdale forum, including myself and Neil Fein, the Neils on Wheels Bike Touring Team
https://nowbtt.blogspot.com/

You should join us.

Best wishes,
Neil

Let us know how this turns out, I'm pretty curious. I've never heard of anyone changing wheel size before now.

BTW, I commute on a mountain bike, and semi-slick tires helped tremendously.

The life as you knew it is over. Join the collective and know the freedom that comes with assimilation of... ahem, sorry about that. Welcome to the board! Where are you located?

First larger wheels will not make you noticeably faster. They may reduce your rolling resistance a small amount which will help but you can get most/all of that advantage by putting similar tires on you 26" wheels. You will increase the gear ratios off all your gears but unless you don't currently have a high enough gear you will just end up using a lower gear than before.
Second if you are using rim brakes brakes may be a major problem. Brake calipers have a limited range of adjustment so even if you can mount the caliper brakes to your bike you may not be able to adjust them to you new rims. There are at least 5 different caliper lengths from short reach racing brakes to x-long reach BMX and walmart MTB calipers. The 3 sizes in between are often very hard to find.
Third as you noted rear hub spacing and chain line might be a problem. Road bikes and MTBs have different spacing and chain lines. This can probably be adjusted for by using the middle chain ring and spacing the new wheel to line it up.

This sounds like a project with lots of problems and little gain, but it might be possible to make it work.

Craig

Lee Bridgers knows his stuff, even though a lot of 'net "experts" think otherwise. Besides that, he's one of the most big-hearted people I've ever had the opportunity to call a friend.

all seems good, i'm attempting to remove an old freewheel then put a fixed cog on, should be sweet. just wait for the picks..........

I've ordered some parts to go on my Trek 8500 frame:
Dia-Compe 287-V for linear pull brakes
Sugino Single Speed 175 Road 48t 3/32" 130mm
Avid BB7 Road Front & Rear disc
Dimension Road 46cm 26.0 flat top road bar
Winwood Carbon Cross Fork 1-1/8" w/ disc tabs

I'm going to rebuild the Bontrager wheels from the Trek with some Open Pro rims I have lying around [+ new spokes/nipples], drop a stem on there with the drop bar and long-pull levers - kaboom...

I Did this to a Marin Bear Valley frame I had. The difference was that I made mine a fixed gear, so I didn't have a brake in the back. There was plenty of tire clearance for both tires. I put a road fork on the front, and mounted a road brake. It runs just fine. In this case the high bottom bracket was not a problem. the frame is a compact frame, so the stand over was fine, and since its a fixed gear, it made pedal clearance when cornering a non issue. I admit, its not a perfect solution, and the chain line isn't perfect, but it works. I probably put too much money into it, but the learning experience was worth it.
And the weight difference between a mountain wheel/tire and a road wheel/tire will make a definite impact on speed, and more so on acceleration, due to the drop in rotating weight .

The brake setup is likely to be your biggest problem. If your frame can even fit a 700c (that's one "c", not two) wheel with tire, the existing brake pad will have to be elevated by 32 mm (622-559/2) to meet your larger diameter rim. You may need a special type of linear brake like the Paul Components Moto-BMX which has enough travel to move a brake pad that distance. Apart from that, you will have some frame geometry issues, since the bigger wheels would raise your bottom bracket. How much will depend on how tall your old 559 tires were and how short your new 622 tires are. Also, you will need to make some form of extension to your rear hub to cover and center the extra 5mm of dropout spread (more if those old road hubs are 126mm instead of modern 130mm).

This could be a more expensive project than you are planning for and even if you are successful, may result in a less than great bike for street riding. It may be better to look for a 29er frame.

Different problem, same solution: I got a early 90s C'dale M800 frame real cheap--it had been gathering dust in the LBS for years. Only problem was that it ran some non-canti style of brake. U-brake? Roller brake or something? Maybe BMX brakes would have worked? In any case, the brake studs wouldn't work with cantis or Vs. Didn't matter--I picked up a pair of Sachs (just before SRAM buyout) *drum* brakes. They work great. Didn't convert to 700cc, but I now have a pair of 26" wheels that can go on any frame, brake bosses or not.