700c rims on a MTB

Alphabet

Need a bit of confirmation that i'm no about to waste a bit of cash.

I currently commute on my Kona Kula decked out with some slicks



The rims are insanely tight and I'm getting hacked off with swapping tyres over for knobblies at the weekend so am getting a second set of wheels to make life a bit easier.

As I'm on disc brakes, I'm thinking i may as well go for 700c rims (actually 29er MTB rims - these ones http://www.wiggle.co.uk/p/cycle/7/Fulcrum_Red_Metal_29er_SL_Mtb_Wheelset/5360046597/#more) with disc hubs. I've checked a 700c wheel in my frame and there's plenty of room for a road tyre.

Is this worth doing? I'm getting a second set of wheels anyway, so thought I may as well make them a bit more roadie for the commute. I know the gearing's going to be out of whack a bit, but I'll survive. This brings me on to my second question. from a bit of looking around, it seems a road rear 9 speed cassette will fit on a MTB hub with no issues. I've got an XT rear mech on there at the mo. If i were to swap out my 11-32 cassette on my mtb rims for a 11-23 Ultrega 9 speed road one, would i need to adjust the derailleur in any way, or could i just pop the wheel in an cycle off?

I don't want a second bike, i just want to be able to quickly change from commute to offroad in a few minutes. any advise would be gratefully received. ta.

gtvlusso

Hi,

Dodgy ground fella, Have you checked a 700c wheel in both front and back? Most forks will not fit 29er/700c, you would need 29er forks.

Any cassette will work (as long as you adjust the chain length accordingly). I.e. an MTB cassette of 11-32 will require a different chain length to an 11-27 road cassette (you will get crap changes and allot of chainslap if you try and mix both types of cassette). You also need the clearance of the wheel turning as you pedal - i.e. your foot does not hit the front wheel whilst turning.

I would seriously be very careful - MTB's are natually heavier and 700c may flex/buckle. Even though there may be clearance, if the tyre does strike the frame of fork, you are gonna have a sketchy moment.

Maybe try it with some old secondhand wheels - stick to an MTB cassette - or buy a 29er frame and transplant your stuff onto it.

Being honest with you - I think it is a bit dangerous and frought with complication. You start to enter the territory of rear mech drop and a whole host of horrible shite! There is a reason why no onw has put road wheels in MTB frames...!

chris281192

they might fit, but personally i would just advise buying another pair of 26 inch wheels

nicklouse

with road rims and slicks no probs.

the 29er rims may limit your tyre choice which may make things too tall.

Alphabet

thanks for the advice. I've checked a 700 rim in the front and back and there's more than enough clearance. there is loads of room for mud with an mtb tyre on a 26" rim, so a smaller tyre on a 29" doesn't make too much difference in actual size as far as i can see - won't need much clearance as it'll just be on the road. it's a proper mtb rim too, so *hopefully* no chance of buckling. will check out i've got room to turn the bars though - thanks for pointing that out.

think i'll stick with an mtb cassette for the time being to make life easier though.

gtvlusso

Defo use the same ratio cassette - otherwise chainlength and mech drop start to come into play - you cannot really mismatch cassettes on different wheelsets unless you wan to start changing chains.....you can get away with it with an 11-32 and an 11-34 with a long drop mech, but I would not risk a more diverse choice.

Get a high spoke count of 700c wheels as your front end weght with sus forks will be far more than a hybrid or a road bike.

Also, your foot height will change - be careful when you put your foot down, further than you think!

stickman

I converted a mtb wheel bike to 650a. Changed vees to calipers, fixed/single so all that derailleur rubbish didn't affect me. Using Delta Cruiser cream tyres. If I want to go off-road cycle speedway tyres are available (they're the same tread as cyclo cross).

Buckled_Rims

The geometry will change with 700 wheels. I'm not an expert but it might make the bike slower and less maneuverable or is it slower and very twitchy.

Simplest is buy a new 29" MTB bike.

will3

I thought the point was that a 700c rim +25mm tyre was roughly the same OD as a 26" rim with a chunky tyre on, no?

tiny_pens

You may find that changing wheels may be just as time consuming when you factor in adjusting the rear mech.
I commute on a cross bike and have 2 sets of wheels (ostensibly winter and summer but really slicks and knobblies). I have to adjust the rear mech each time I change wheels because although the rear cassette ratios are about the same, i have slightly different make wheels and cassettes. If your commute is short enough its alright but I found the slight rubbing sounds really annoying.

If you counted up the total cost could you buy a second hand commuter? Assuming you have space for another bike of course...

alfablue

I ran 2 identical sets of wheels on my mtb, one with noblies, the other set with 26x1 Spesh All Conditions slicks. Both cassettes were exactly the same. If you get different wheels for each use you run the risk of swapping the tyre changing hassle for adjusting gearing and aligning disc brake hassle. Just get another set of 26 inch rims and go for a 26x1 tyre, this will be good enough, I doubt if a 700c wheel would make much difference at all. I commuted for 2 years on this setup and my speed was good.

nicklouse

here is a 26" MTB frame and fork with 28" wheels and cross tyres.



put it together last year some time.

just squeezed a fender between the fork crown and tyre.

no hope on the rear though.

pedal brake so no probs.

jimmcdonnell

The geometry will change with 700 wheels

No it won't.

It would - slightly - if you only changed front or rear, but change both and the only thing that will happen is you'll be higher off the ground when sat in the saddle, as already mentioned.

Larger dia wheels will make them roll over bumps better, but they'll accelerate slower. I'd bet not enough for any normal user to really notice though.

Also, stick to the same make of hub and cassette and you ought to be ok with the wheel swop without mucking around adjusting the derailleur. I swop wheelsets with different casssettes depending on my needs (also chainset, which in my case gets around the chain length issue - you'd need to experiment), have never had to readjust rear mech unless I've cocked it up myself during the change.

Alphabet

the rims are 19mm so i'll be able to stick on some 28c tires and maybe 25c at a push, the overall diameter will be about the same as 26" plus big fat tyres. going to get a second set of identical brake rotors and cassette to hopefully stave off too much adjustment. i really want this to work, but i think i'm going to have to have a long chat with my lbs tomorrow - hopefully they'll let me do a bit of a fitting.

Roastie

Very good mod to make for the road - as someone already said, OD of 26" MTB tyre and 700c with a skinny tyre isn't too far off. Certainly the differences in handling, etc. are no problem.

Not sure why gtvlusso is so worried about the weight of the MTB components on the wheel - the weight of the rider makes the extra frame and fork weight quite irrelevant.

The only problem I can see apart from needing to tweak the indexing is that the disc alignment may be different for the different wheels which may require caliper alignment for each set of wheels - you can solve this if you have 6-bolt discs by shimming the disks on one of the wheels to get both discs to the same alignment (work out which hub puts the disc closer to the hub, then shim out to match the other). Can be done with Centrelock - too, but I haven't seen the neccesary spacer shims around.

I have this issue with the different wheels and hubs I've been testing - but laziness and Avid's excellent alignment system has meant I haven't bothered doing this myself.

Otherwise I can't see the issue. If it is just for road use and you don't need such a strong rim, so I'd probably opt for a lighter weight rim laced to a good MTB hub. I have one set of wheels running Mavic TN719 (29er) rims on SLX hubs and another with Halo Aerotracks running on LX hubs. Both 32 spoke. The Halos spin up significantly quicker than the TN719s, and they arguably also give a softer ride. They are pretty strong too - no problems with running them off road on cross tyres - I weigh 70kg.

That said, doing it again, for commuting on fairly good tarmac, I'd go for Mavic Open Pros on SLX hubs.

Edit: On second thought, not sure if I'd recommend Open Pro (tho' I'd certainly do it for myself) - the rim may not have the strength to take the braking forces through the spokes - a deeper section rim like the CXP33 may be better? (calling all resident wheel builders)

MyPace

700c works fine in almost all MTBs. you'd have to have incredibly tight clearance for a 700* 23mm not to fit. 700c wheels are also plenty strong enough.

Swapping wheels however, whilst possible, isn't as simple as you'd think. The casstte will wear at a different rate, so the chain will skip unless you swap the cassette over too. This will probably take around the same length of time as swapping the tyres!

If you get a very light 26" slick, like the conti grand prix, or specialized all condition pro, theres very little difference in speed too.

el_presidente

Might want to use the same hubs otherwise dsks might be in a slightly different position giving rub

nicklouse

jimmcdonnell
actually one part of the geometry does change. the steering trail.

which is a part of how the steering feels.

as said keeping to the same make of hubs can make the swaps easier but often does not as bearing wear and adjustment have greater effect.

on of the best options is to shim the discs to suit one of the hubs fitting.

Alphabet

thought about the disc being in different positions, but it's so easy to adjust the brakes (loosen the bolts, squeeze the brakes, tighten back up again), so i'm not too worried.

cassette wear is a bit of a thing though. hmm...

will3

nicklouse wrote:

jimmcdonnell
actually one part of the geometry does change. the steering trail.

which is a part of how the steering feels.
.

Surely this would onyl be the case if the tyre outside diameter of the 700c skinny was different to the 26" chubby tyre - if not then there wouldn't be a vast difference, and in any case since we're agreed that there is not a lot of difference between the two, the change in trail would be of the same order of magnitude as changing from a large chubby tyre to a smaller one wouldn't it?

Jay dubbleU

N+1 indicates that what you actually need is a new bike

Alphabet

haha. the wife would kill me.







...might be worth it though. i quite like the idea of having an adaptable bike though. it's a fairyl light hardtail as it is and I'm doing pretty well in the SCR stakes, much to the annoyance of the occasional roadie. excellent for hills too, blitzed past everyone on the slopes to dunwich last weekend.

ride_whenever

The best thing is to run a chain with each cassette, particularly if you have steel rings you'll find the wear on them in minimal and it should work fairly well. With a powerlink or similar swapping chains will add minimal inconvenience.

As others have said, either get the same hubs, or get a shimano hub so you can move it slightly wrt the dropouts then re-dish to get the cassettes to line up with the indexing and shim the disc rotors to get them in the same place.

Alphabet

i just bought a new bike instead :roll:

Anonymous

Alphabet wrote:

i just bought a new bike instead :roll:

Have you thought about a second set of wheels for it so you can ride light off road if you want?

Alphabet

no, but i was considering a couple of bolt on wheels and an engine so i can have a faux car when i need it