I've been commuting on an old Mountain Bike with 26 inches wheel o which I've put a 1.5 tyre. But i've been thinking about changing the wheels for a brand new 700cc wheel expecting my commute would get faster, will it?

How weird would my bicycle look?

It'll be so fast you won't be able to stop! Not without disc brakes at least. (because your brakes won't reach the rim, assuming it even clears the fork)

If you make it work it'll be faster, but it would probably be a lot less hassle to just get a 700c bike.

The wheel probably won't fit. If you have rim brakes, the brakes you have will not accomodate the difference in rim diameter (which would require the brake pads to be able to move by ~33mm, or 1 1/4 inch.

The narrowest, lightest 26" MTB wheels available are pretty narrow and light-- and the same goes for narrow light tires. I've seen 26x1.0" slick tires before.

You could swap out the fork for a 700c fork, but you'd still be stuck with a 26" rear. Of course, not really intended as a fast road bike, but you could build a 69er that way..

They fit my 93 specialized rockhopper perfectly, just get new brakes made for flat bar brake levers, they pull a different amount of cable. It may not work out though, I'ld fit 'em at a shop or borrow someones wheels first, and fenders will be all the more hit or miss.

All in all it could become a huge fiasco of a project.


jim

+1

I've been down this road with my mtb. NOt worth the mods and headaches; you'd be better off selling the bike and getting a 700c bike.

I even thought of putting 650 wheels on but your brakes still may not line up well and it will limit your tire choices.

Fwiw I have two bikes about the same weight - one has 26s, the other has 700s, and while I do feel the 700s have a better ride and are faster and climb better, if you are happy with your present bike it may still be worth keeping, especially for commuting.

I'd recommend Continental Grand Prix folding tires in the 26x1.0 size - about $50 each and the sidewalls age faster than cheaper tires but imo they are worth it and the best move for making your mtb fast on the road. Excellent ride and cornering too. Keep the pressure up to 110 or so, watch out for glass and you should avoid flats okay.

If that price is too steep Ritchey tom slicks are available in different widths for about $25 each. They make a 1.0 but it is wider and heavier than the Conti. I've only seen it in wire bead, they may have folding versions available. They are pretty flat proof and last longer than the contis in my experience. Not as fast as the Contis nor do they handle as well, but you'll feel a difference from the 1.5s. They are a good cheap tire in my opinion.

IRC makes a "smoothie" which is very reasonable and probably closer to a true 1.25. They are a little heavy and don't last as long as the two I listed above but they are about $20 apiece last I saw them.

Specialized also makes a slick ("fat Boy"?) not sure what they cost and have never tried them.

Your comment on the Tom Slicks is interesting, I have these in 1.4 inch and like them. I didn't realize they were Ritchey until you said, I bought them mostly on price, ($17 CA at MEC) After reading your comment I went and looked up some reviews, most people love the speed and cornering, but some people complain of flats while others have no problems. Myself, I'm 225 and run them at 80-85 PSI and have had no problems for at least 1000Km. There is a little nick in the back tire, right in the center, but it hasn't widened or anything. I ride through debris and have had to ride across some glass shards without incident, drop off kerbs, that sort of thing. YMMV I guess.

The idea of changing to 700C is possible but I wouldn't recommend it.

If he makes it work, it'll just be a higher final drive gear ratio. A bigger chainring and a longer chain would net the same effect, probably for a lot cheaper.

I really don't notice much rolling resistance delta between my 26"x1.25" mountain bike slicks at 85 PSI on my hybrid and my 700x25 tires at 100 PSI on my road bike.

The difference in speed between the road bike and hybrid comes mostly from gearing and a more aerodynamic seating position.

Paul Components makes a brake called the "Moto BMX" that is designed to be able to convert a 26" mountain bike to 700c or 27". But they are seriously pricey.

were you looking at MTBR.com? A lot of tire reviews complain of flats for some reason. I think the Tom slicks corner okay, I just think the Contis are better. Right now I've been running a Tom Slick 1.0 in front and a Conti in rear, mostly because my front rim is a bit wider. I think the wider tire in front gives me a bit more cushion to the handlebars which is nice for a commuter.

They are but the ride is harsh and uncomfortable without a suspension fork in front. Good in theory not so good in practice. I'd go with a road bike if you want to ride with skinny tires.

I have cheap V-brakes which have some adjusting space.
It's an old cheap montain bike the fork is rigid, so no problems there I think.

The reason for going with this upgrade is my wife complains about how much money I spend on bikes (I love mountain biking and upgrading the other mountain bike is nice hobby) besides I'm also building a house.

I thought biger diameter wheels would make me go faster, but according to you guys I am wrong.

I've heard roadies say this. On the other hand, mountain bikers ride niners to increase the amount of ground contact with the tire, claiming it gives them better traction. You'd almost think that more contact would also mean more rolling resistance and less speed on the road.

My own inclination is to say that 700's are faster. But I think tire width and tread, rider position for wind, and weight are more important than wheel size. There's a lot here that's simply tradition.

Jeez, you're building a house and you don't have enough projects to drive you crazy?

Someone with a greater grasp of physics than me might contradict me or might say I'm right and explain it better, but my feeling is that the 700c wheels will be easier to ride fast than the 26in. The 26ers should accelerate faster, but the larger diameter of the 700c wheels will establish greater rotational inertia (don't know if that's a real term - it just popped into my head). So once you get 'em goin fast, it's easier to keep 'em goin fast.

I think this will be workable with disk brakes, but not worth the effort otherwise.

I think it will ride better though: A 26" wheel with a 1" tire is getting pretty small in diameter.

Sounds like a pain in the butt. Further, what is the point? With narrow slicks and modified gearing on an old steel mountain bike a friend of mine used to hunt down roadies with great regularity.

see thread

yes, it's possible if you've got the clearance on your frame
yes, it'll look a little funny
yes, you'll feel faster.

yes, you'll spend a pretty penny converting the brakes, and on the wheels themselves, but it'll be an interesting project.

Try borrowing some 700c wheels from a friend and putting them in there before starting your project, the bike I was working on fit like a road bike to begin with (long and high) and the extra height made the bike too tall, so I scrapped the project - I'm now converting a hybrid to cyclocross. It'll be interesting.

good catch - I also had to put a new cassette (13-23, replacing the dirt-intended stock 13-30) for the road - I still get up the paved hills fine and the gearing is higher to get me closer to road bike speed (close enough while commuting, certainly!)

The diameter isn't THAT much bigger, really. Just big enough to make brake fitment a pain in the ass.

Also, 700c wheels tend to be made for road bikes, thus are usually even lighter and more fragile than the shorter 26" wheels, which are often either over-engineered (for really bulletproof MTBs) or made of cheap, heavy materials (on really low-end MTBs). The end result is that inertia of the 700c wheels, tires and all will generally be lower than 26" wheels.

What 700c wheels do is allow you to use narrow, high pressure tires, and they increase the gear-inch ratio of the bicycle.

You can go get narrow, high pressure mountain bike slicks that aren't nearly as narrow as road bike touring tires, but they suffice. To tackle the gear-inch problem (which is only a problem if you find yourself spinning out on your current bike, with your legs unable to keep up with your bike's maximum speed) you can swap out for a cassette that has less teeth on the further-out gears, or get a crankset or replacement large chainring that has more teeth. This will effectively give you a higher final drive gear ratio, and it will be a lot cheaper and easier than buying two new wheels, tubes, tires, and trying to piecemeal a working brake system together.

just to follow up, I'd go the cassette route first - cheaper than chainrings, and may be easier for your rear derailleur to 'adapt' than the front. Of course, if this is an old bike you may want to put a new chain and chainrings on in the interest of smooth shifting and even wear. i did this as my bike is 14 years old; I swapped the original 46/36/26 triple for new rings. I wanted a 48 up front but my derailleur wouldn't have handled it well. I stuck with 46 (plenty high for my commute in city stop & go traffic), but went down to 35 and 24 rings to compliment the higher-geared cassette.

I love my new 13-23 on the mtb for pavement use. Not only do I have good chainline when using the granny ring (24x23 is plenty low; the original was 26x30 which was just overkill on the road) but my cassette has smaller jumps which are great in traffic. Y9u appreciate a big four tooth drop when you hit a steep dirt hill with loose gravel and rocks, etc. but it just isn't necessary on pavement.

Since I was having some troubles with the gears I have already followed some of your advices. I have a seven gear hub 11-24 (well, it is really a nine gear hub but the shifters are only 7 speeds so the two bigger rings are not in use).

I have yet to see how it works.

I have also ordered o new front wheel -26 inches- since according to most of you no improvement would come from the 700c wheels.

The front wheel I' ve been using is 10 years old and it produces some loud cracking noise according to my LBS it's the axle which is gone. BUt it is so old that they aren't any longer available in that measure.

I think you'll be happy sticking with the 26". I replaced my original front wheel (pretty nice, with Shimano DX hub and 32 spokes) with a newer similar wheel with the oversized XT hub, also 32h. It works great with a nice 1" wide slick kept at 100 psi.

I don't know if your 9 spd cassette is in good shape or how well that will shift for you but you can also put a new 7 spd cassette on there and just use spacers as well. I would think a 7 spd chain would not work on a 9 spd cassette - but maybe you already have a 9 spd chain on there?

Warning: This could be expensive.

I'm doing this right now - I've bought a new wheelset, and will need new tyres. Brakes aren't an issue for me as I have disks - but I paid $$$ for that 18 months ago. The price for this upgrade will be $400AUD = $320+US. (thats ok, I save around $70/week commuting, so it will pay for itself in 5-6 weeks).

By the way - the only real way to get faster is to upgrade the engine! My man Stuart O'Grady would be faster than me if he were riding my mums old raleigh, and me on my TT bike.

Watch out if you're using indexed shifters. The spacing is considerably tighter on a 9-speed cassette. I run an 8-speed cassette on my 7-speed shifters for my hybrid and I have to get it dialed in perfectly in 4th gear on the shifter, then 1st gear (second on the cassette) makes just a little noise but stays in gear. Same with 7th gear (8th on the cassette). If you're using friction shifters it won't make any difference.

Changing 26" to 700c won't make you go faster on your commute. It will simply increase all your gears by about 10%. To get an equivalent gear in 700c you'll need to shift one gear down compared to the 26", and your top/low gears will be different.

Like was said you'll run into compatibility problem with your brake pads if you make the switch. Just get 1.25" tires, which should be great for commuting.

There is a difference in rotational inertia but this only affects accelerations, which are small in cycling. 26" wheels are stronger, have a smaller profile (only in the 650c version with narrow tires used in TTs), but have a bit more rolling resistance compared to 700c.