Road Cycling - Road gears on MTB?

I've been told a road gear cluster will fit on a my shimano MTB hub.

Will it make a difference to my riding times on a 40km triathlon ride? At the moment it takes me about 1hr 15-20mins.

Been doing a lot of road work on my mountain bike lately for the London Tri and set it up with skinny slicks, solid fork and lowered bars (all bits I had, can't afford a road bike specially for). I'm only using the top 3-4 gears and find the ratios a little too far apart to keep in the rev range 90-100. e.g. zooming along at 100rpm, change up and rpm drops to 84 and have to work too hard to get rpm up again depending on
conditions. This is hard on my poor old knees and made the assumption that using road bike gear ratios maybe better. I would guess these would have a 10rpm or less separation rather that 15rpm.

Can anyone shed some light on this for me? Wish I had looked into this a little earlier as it would be nice to know if the change is worth doing time/energy saving wise for the race.

thanks for any help you can offer.
Steve.

Road gear cluster will fit the ATB hubs and you will really appreciate the single tooth spacings. May not make much difference in your time, but the increased comfort in maintaining a constant cadence should help. I can recall the change from 5spd FW 14/15/17/19.. to 8spd 13/14/15/17.... and you shift up or down on any little change in road gradient allowing a relatively constant cadence. Your long cage R der will not be as crisp as a road der but will do ok. If the terrain is flat, and you ride in the 25mph+ range an 11-21 or 11-23 would be ideal if you are using standard ATB triple set up. Steve

What have you got up front?

Youcan use the gear calculator at www.sheldonbrown.com to get a sense of precisely what to expect from each gear combo with any range of cogs you might choose.

I would say that yes, if you're not having a problem of spinning out in your tallest gear, then you'll get some improvement with a road cassette, especially if you also switch to a short-cage rear derailleur and shorten your chain. It won't be profound, but over 40km you'll pick up a few seconds during the stretches where you now have the perfect gear, and your bike will be a smidge lighter, too.

RichC

Thanks for your replies guys. I will check out the gear calculator at Sheldons, I saw it earlier but haven't had time to try it. My bike has an 8-speed cassette 11/13/15-30 on it so it will probably make quite a difference if I can split it down to 11/12/13/?? I will check it out when I'm at the bike shop tomorrow and see what I can get. I also forgot to mention the course is basically flat with a couple of motorway overpasses on it for hills so the closer gears would be nice.

Richard D
Front forks are off a friends Canadale when he replaced them with suspension ones. Ideal for this as they are very light and no wasted energy on them, bit harsh for off road use though:).

thanks again.

Richard D
Just realised I probably misinterpreted what you meant about "What have you got up front?" I thought you meant the forks for some reason. Have three cogs 22/32/44

Wow! You do triathlons with your mountain bike??

I just bought a 11-21 (9s) cassette for my mtb road wheels as I had the same problem of searching for 'in between' ratios that the 11-32 didn't have. Definately worth it for road miles.

Thanks skdsl, going to stick with 8-speed so I don't have to reindex when puting my knobblies on. From peoples replies and what I've read on Sheldons site it will be worth doing, specially since London is so flat and this is where my road miles are.

Chi, yes, this is my first real triathlon and I can't afford a road bike at the moment so setting up the MTB (98 Rockhopper) for it. The bike is actually very nice to ride on the road, I think the closer ratios will make it even better and I'm sure I will be passing plenty of road bikes on the day. From what I've read about tri-bikes mine is fairly similar (no areo bars though) with 26inch wheels, seat angle etc. I did do a half trialthon a few years ago in the Yukon that was a mountain bike trail ride and cross country run with swimming in a lake. Was a lot of fun, that's where I decided it was time to learn to swim so I could do a proper one.

I used a 12-27 Duar ace cluster on my MTB for certain XC races. With a 44/32/32 crank in front the smaller tooth size spacing on the road cluster actually gives me a better spread of gears and I can actually use the 22 chainring.

I now use a 11-32 cassette with 44/29 crankset in front which is also really good for usable spread of gears.

Using a road cluster on your MTB can is definately a good idea for road use.
Another idea to consider is fitting discs to your MTB. That way you can fit a wheels built around disc hubs with 700c rims. Wheels for road, wheels for MTB all on one bike. Sweet hey?

'98 rockhopper eh? Mine's a '99 Rockhopper comp :D and it was already 9 sp. I did consider going back to 8 sp as the chains/cassettes are much cheaper, but I think i'll stick with 9.

Originally posted by stevecyclery
Richard D
Just realised I probably misinterpreted what you meant about "What have you got up front?" I thought you meant the forks for some reason. Have three cogs 22/32/44

I wondered whether it might be worth going up to a 48T top (with corresponding smaller rings) your front mech should be okay - you can get a reasonable Nexave chainset with hollow cranks for about £50.

Richard

Thanks for all the info and replies on roadie gears for my bike. Now have 11/12/13/14/15/17/19/21 and it's magic to ride with, fitted a new gear cable as well. Took a 12-23 cassette, removed the 23 and put my 11 in from the MTB setup, sweat. Still twidling to get supper smooth changes but it's pretty good, I guess the cable stretches a little to start with. All I need now is aero bars and I'll almost have a proper
tri bike:).