Bicycle Mechanics - 26" wheels on a 700c frame?

Hello People. Is there any reason why 26" mtb wheels shouldn't be used on a 700c frame? Having bought a 700c hybrid frame (135mm spacing) with disc brake only mounts I'm finding it difficult to find cheap 700c disc hub wheels. I calculate that the difference in the height of the bike will only change by about 2cm. I'll be fitting reasonably chuncky tyres for city communting. Cheers, Pete.

So how far above ground level is your pedal at it's lowest point? I'm thinking that you might find yourself adding the cost of a 26" wheelset onto the price of whatever other wheels you eventually decide to buy.

Hello People. Is there any reason why 26" mtb wheels shouldn't be used on a 700c frame? Having bought a 700c hybrid frame (135mm spacing) with disc brake only mounts I'm finding it difficult to find cheap 700c disc hub wheels. I calculate that the difference in the height of the bike will only change by about 2cm. I'll be fitting reasonably chuncky tyres for city communting. Cheers, Pete.

You may want to recalculate. Neglecting tires, the rim of a 26" mountain bike wheel has a diameter 559mm while a 700C wheel has a 622 mm diameter. That's a difference of 63mm or 6.3 cm (2.4"). That means that your bottom bracket is 2.4" closer to the pavement. Pedal strike could become a problem unless you are very careful going around corners. If the bike has a low bottom bracket to begin with, it could be even more problematic. 2.4" lower could also affect handling negatively. You could try it or you could just build the proper wheels. Wheel building isn't that difficult and it gives you a sense of accomplishment.

:eek: I though that 700c referred to a 700mm diameter. Perhaps it's time to give wheelbuilding a try. Thanks for your responses. Pete

:eek: I though that 700c referred to a 700mm diameter.

It does, but it's a generality.

It does, but it's a generality.

And includes the tire. (I can't get my edit function to work.)

:eek: I though that 700c referred to a 700mm diameter. Perhaps it's time to give wheelbuilding a try. Thanks for your responses. Pete

If you really thought that, your calculation must have been even more off, that is, you must have noticed an even greater difference in wheel sizes, and therefore, an even stronger case for making a wheel instead of putting a 26" on a 700c frame.

I am a bit confused by your train of thoughts.

You may want to recalculate. Neglecting tires, the rim of a 26" mountain bike wheel has a diameter 559mm while a 700C wheel has a 622 mm diameter. That's a difference of 63mm or 6.3 cm (2.4"). That means that your bottom bracket is 2.4" closer to the pavement. Pedal strike could become a problem unless you are very careful going around corners. If the bike has a low bottom bracket to begin with, it could be even more problematic. 2.4" lower could also affect handling negatively. You could try it or you could just build the proper wheels. Wheel building isn't that difficult and it gives you a sense of accomplishment.

Your math is a bit off. The wheel difference is approximately (700 - 650)/2 = 25mm, about one inch. The axle height is a function of the difference in 1/2 of the diameter or the radius. This can also be divided by 2 a second time because the rear wheel is not changing, only the front. So a good estimate of the drop in the bottom bracket and pedals would be about 1/2 inch.

I would be more concerned with what happens with the change in steering trail.

Al

700c/disc wheelsets are becoming more popular because of the increasing popularity of 29" mountain bikes, so you might keep shopping around. But you said "cheap wheels" so that might be the catch for you.........I don't know how fat a tire you're currently running on the hybrid, or how fat you could go as to the clearances on the frame and fork, but if you're currently running, say, a 32c tire and you could go to something like a 26" x 1.75", you'd offset some of the ground clearance issue. As for that: 622mm (diameter of 700c rim) minus 559mm (diameter of 26" rim) equals 63mm. Divide difference by two for the difference in radius, which is the applicable measurement for the difference in ground clearance: 31.5mm, or 3.15 cm, which is what, about an inch and a half?

edit: I looked it up, 3.15cm equals 1.24 inches.

Shop around for some reasonably priced disc mtb hubs and 700c wheels and build them up, or have an LBS do it. A buddy/wrench at my LBS has a Karate Monkey set up w/ mechanical discs and 2 sets of disc wheels. One gets a set of 2.3" WTB 29er mtb tires while the set used for commuting to campus/work has a set of 700/25 Contis on them. Both sets are disc only and he laced them up on the cheap. Less than a machine built pre assembled pair from the catalog even after his shop discount.

Your math is a bit off. The wheel difference is approximately (700 - 650)/2 = 25mm, about one inch. The axle height is a function of the difference in 1/2 of the diameter or the radius. This can also be divided by 2 a second time because the rear wheel is not changing, only the front. So a good estimate of the drop in the bottom bracket and pedals would be about 1/2 inch.

I would be more concerned with what happens with the change in steering trail.

Al

D'oh! But I did say that I was neglecting tires because tire height is rather variable. Pe4er is looking at both wheels so the front and rear would change and the 'rim' difference would still be 1.2" which can be a lot in terms of lowering a bottom bracket...depending on the terrain being ridden and the geometry of the bike, of course.

650C wheels, by the way, have a diameter of 571mm, he says, muddying the waters even more.

2cm is OK. My MTB is nearly 2cm lower when I swap from 26x2.1 to 26x1.4 -- (2.1-1.4)*2.54 = 1.8cm. As long as the frame has enough clearance for the tires, I say go for it.

700c/disc wheelsets are becoming more popular because of the increasing popularity of 29" mountain bikes, so you might keep shopping around. But you said "cheap wheels" so that might be the catch for you.........I don't know how fat a tire you're currently running on the hybrid, or how fat you could go as to the clearances on the frame and fork, but if you're currently running, say, a 32c tire and you could go to something like a 26" x 1.75", you'd offset some of the ground clearance issue. As for that: 622mm (diameter of 700c rim) minus 559mm (diameter of 26" rim) equals 63mm. Divide difference by two for the difference in radius, which is the applicable measurement for the difference in ground clearance: 31.5mm, or 3.15 cm, which is what, about an inch and a half?

edit: I looked it up, 3.15cm equals 1.24 inches.

Ok, but the OP is lowering only the front half of the bike, so the bottom bracket and pedals will be lowered only about 1/2 of the 1.24 inches, or about 0.63 inches which is the number is asking for. A larger tire on the front would help compensate for the drop, but only a small amount.

Al

Ok, but the OP is lowering only the front half of the bike, so the bottom bracket and pedals will be lowered only about 1/2 of the 1.24 inches, or about 0.63 inches which is the number is asking for. A larger tire on the front would help compensate for the drop, but only a small amount.

Al

I had the impression he was looking for a wheelset, not just the rear wheel.

I had the impression he was looking for a wheelset, not just the rear wheel.

I had that impression too.

Which, by the way, means that there should be essentially no difference in handling. If you drastically change the height of the front relative to the rear, you'll change the handling of the bike, but otherwise handling will be basically the same (aside from changes due to different tire/wheel weights.)

Here are some inexpensive disc wheels from a German online site. I've ordered many times from this company and am quite happy with them. Their prices are excelent and they have very good Englsih speaking customer service.

http://www.bike-components.de/catalog/product_info.php?cPath=281_129&products_id=3887&osCsid=492d56d77cc793a22fda481ee0948c8e

I had the impression he was looking for a wheelset, not just the rear wheel.

Ok, sorry, I got two different threads mixed up.

Thank goodness for this thread! It (+ a little research and a lot of measuring) just answered a question I had. I'll be doing something similar to the OP, at least temporarily.I'll be using a Surly Instigator fork, which has a crown higher than most 700C forks, so I might not even have my frame lower than it was originally supposed to - or at least, it will be just a little bit lower, a few mm at most.

Excellent thread!

You could go with Fat Franks or Big Apples. Otherwise, I wouldn't bother. Half the fun of a 26" bike conversion is rolling along on balloon tires, which can be as fast as a skinny one and more comfortable.

Buy a cheap set of 29er wheels. They're just 700c's (622mm). I priced out a set of Bontrager Super Sport disc wheels (was researching a CL price) and the set was $225. (front was $99) I'm sure there are other wheels out there at that price point or lower..

-Roger

A 26x2.1 installed has almost the same o.d. as a 700x23, Mavic Speedcitys are often used like this...
A hybrid should handle at least 700x 35, but frame clearance may still be an issue with something really wide.

...If you drastically change the height of the front relative to the rear, you'll change the handling of the bike, but otherwise handling will be basically the same (aside from changes due to different tire/wheel weights.)

This is not true. Handling changes most drastically due to a change in the 'trail' of the bike. Generally speaking, more 'trail' makes a bike more stable and difficult to turn. Less 'trail' makes a bike less stable and easier to turn.

"Trail" is basically the distance from the intersection point of the ground and an imaginary line drawn down the centre of the head-tube, and the point where the front tire touches the ground. The dimansions that affect trail are head angle, fork rake, and wheel diamter. If you change the wheel diameter you change the handling.

Buy a cheap set of 29er wheels. They're just 700c's (622mm). I priced out a set of Bontrager Super Sport disc wheels (was researching a CL price) and the set was $225. (front was $99) I'm sure there are other wheels out there at that price point or lower..

-Roger

+1 I'm building up a set of 29'r wheels for my cross check (no disk brake) so as to a more mtb like experience. There is 29'r stuff for anything you could want.

The common conversion if you just want wider tires (assuming they will even fit in your frame/fork/brakes) is 650B. It provides wide tires. You will however need long reach brakes.