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Old 07-18-03, 09:12 AM   #1
curisu
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road gearing on a mountain bike?

Hi all, I'm hoping this is a relatively new, unaddressed topic. 3 advanced searches didn't reveal any useful information, so here goes:

I've got a pretty decent MTB that sees 90% road use. I've gotten into good enough shape to wrap the chain in the highest gear on some stretches of road/path.

are there offerings for higher gearing for 26" wheels that are closer to road gearing?

are there insurmountable difficulties in mounting a 700mm wheel on an ATB that has clearance for 26" + 2.2" tires?

i'm not at all familiar with road wheels and the related measurements, so if my ignorance is very obvious, i'd appreciate a gentle correction =p.

thanks, and i apologize if this has been address in another thread (please provide a link if possible).

-chris
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Old 07-18-03, 09:16 AM   #2
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I'll qualify this comment by saying I'm no expert. But I do believe if you're looking to roadify your MTB, changing cassettes and putting slick tires on the bike is a good start. I don't know about changin wheels, but I would bet it can be done.
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Old 07-18-03, 09:37 AM   #3
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Yes, it can be done. A road cassette will fit a 8/9-speed hub on a mountain bike no prob. My riding buddy has it set up that way (by mistake), but it works. He needs a new rear derailleur though coz his cage is all fuh up.

Road wheels, however, will not fit a MTB frame. The brake mounts are in the wrong place.
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Old 07-18-03, 09:45 AM   #4
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Along with changeing the cassette and rear derailleur, if you change the chainrings you'll need a new front derailleur and BB. Then you'll need Shinimo's Flat Bar road shifters. (Assuming you're using Shimino)
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Old 07-18-03, 10:09 AM   #5
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thanks for the responses =)

so i'll need new rear derailleur, a new cassette, and a new shifter (flat bar) to change the rear gearing to a roadie's

if i wanted to go whole hog, i'd need a new set of front chainrings? or a new crankset w/BB? + another flatbar shifter?

thanks for the input so far, this could be a really fun project =)

-chris
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Old 07-18-03, 10:18 AM   #6
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Merely swapping to a road rear cluster may not give you the gear inches you're looking for. If you're able to re-mount your front derailleur higher, I'd go with larger chainrings.......but that MAY require swapping cranks as well...
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Old 07-18-03, 10:28 AM   #7
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What size chainrings do you have now? And what model is your crankset?

The difference in speed at a 100rpm cadence between a 42/13 combo and a 46/11 combo is about 6 mph (25 to 31).

If 42/13 is what you have now, and your crankset has replaceable chainrings, you might be able to pick up 6mph without changing anything else. Any MTB FD should handle a 44.

IMO, if you have to go farther than that, it's time to start thinking about a road bike. Once you start replacing bottom brackets, shifters, brakes, etc., you have to ask yourself if it wouldn't make more sense to spend a little more and have two ridable bikes.

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Old 07-18-03, 10:58 AM   #8
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You can simply fit larger rings on your chainset. You dont need to change the BB, and may get away with your existing front mech, certainly up to 48t.
You can swap 26" wheels for 700c on disk-brake bikes, but the advantages of doing so are pretty small. Just use some 1.25-1.5 high pressure slicks.
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Old 07-18-03, 11:20 AM   #9
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thanks again fellas, i have a 44 on front, and an 11 on rear for the highest gear. the crankset is a truvativ x-forge (4 nut pattern).

i do have deore disc brakes on the bike, and it's good to know that i *could* go 700mm if i wanted to.

i'm currently running 1" ritchey tom slicks (awesome tireset) on both wheels, and they cruise nicely on downhills. it's most likely that it's due to those wheels and 100psi that allow me to wrap the chain on down grades.

i have been thinking really hard on a roadie, but this bike is my commuter, and takes a lot of abuse from NYC streets. i want a pretty bomb-proof bike for my daily ride to and from work... i just want it go a bit faster =)

so at this point the advice is:

- get a larger chainring
- replace the cassette with a roadie cassette
- replace rear derailleur with a roadie
- replace rear shifter with a straight bar roadie shifter?
- somewhere down the line, assuming i want to, get 700mm rims and rebuild my wheels

i have a 9-speed XT rear derailleur/shifter. is it possible to use that with a roadie 9-speed? or are the gaps between gears indexed differently?

thanks again guys!

-chris
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Old 07-18-03, 12:21 PM   #10
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Quote:
Originally posted by curisu


- get a larger chainring
- replace the cassette with a roadie cassette
- replace rear derailleur with a roadie
- replace rear shifter with a straight bar roadie shifter?
- somewhere down the line, assuming i want to, get 700mm rims and rebuild my wheels

i have a 9-speed XT rear derailleur/shifter. is it possible to use that with a roadie 9-speed? or are the gaps between gears indexed differently?
Changing the cassette or RD won't help you. You already have an 11-tooth cog, and that's as small as they get. (There is no difference between Shimano "road" and "mountain bike" cassettes other than typical range. As long as the derailleur has the capacity, they're interchangeable.)

Remember it's not the wheel size that matters (in terms of revolutions per pedal rotation), it's the outside diameter of the tire. And it doesn't matter very much.

So increasing the chainring size is what's left in practical terms, keeping in mind your goal. Well, that and pedaling faster.

As noted, at 100rpm cadence on the flats, you should be able to go about 31mph with a 44/11 combo. Going to a 48/11 will only increase that by less than 2mph. And keep in mind that even on a road bike with the highest commonly-available gearing (53/11) the speed would be 37.7mph -- less than 7mph faster than what you currently have. (and also note that professional racers usually use a 12, not an 11).

If you have a 22-tooth small chainring, a 48-tooth big ring might be troublesome for your FD. Anything bigger almost certainly will be.

So in sum, I would be cautious about spending a lot of money, because there may not be a lot to gain.

RichC
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Old 07-18-03, 01:12 PM   #11
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wow, rich, that's a very succinct observation. i really didn't want to spend a lot of money on the "conversion" so it sounds like your recommendation would make the most sense to my wallet.

maybe initially, i'll just switch out the large chain ring for a 46 or 48 tooth and see how that makes me feel. i do spend about 80% of my time in the large gear up front.

you say there isn't much difference between the road/atb cassettes, so why then are the roadie rear derailleurs so small? i always imagined that they were small because the gearing was tighter, and had less distance to pull for the chain to engage the next gear. am i incorrect in thinking this?

thanks!

-chris
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Old 07-18-03, 01:19 PM   #12
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Quote:
Originally posted by curisu

you say there isn't much difference between the road/atb cassettes, so why then are the roadie rear derailleurs so small? i always imagined that they were small because the gearing was tighter, and had less distance to pull for the chain to engage the next gear. am i incorrect in thinking this?
The smaller increments in cog size allow for tighter control over cadence, and also result in crisper shifting. The derailleurs can be smaller because there's less slack in the chain to be taken up because of the smaller difference in size between largest and smallest cog.

If you never need anything bigger than a 23 or 25, then sure, you could switch to a road cassette and gain those benefits. But that won't do anything for the main problem you were trying to solve, running out of gears when going fast.

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Old 07-18-03, 02:10 PM   #13
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Why bother? By the time you're through, you'll have spent about $800 on a bike that's still heavy, and is nothing more than a glorified hybrid. You can buy nearly any hybrid complete for this much money or less.

If you want a road bike, save up your money and buy a road bike.
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Old 07-18-03, 02:30 PM   #14
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Seems like you are under the impression that road bikes are weak, and can't take any abuse. In reality they are strong and can take quite a bit of abuse from road riding.. People use basicaly a road bike in Cyclocross and those take quite a bit of abuse. I agree with the others just change your chainrings will probably get you close to road gearing, the gap between the rings might casue problems.. I'm assuming the current rings are 22-32-44, replacing the 44 for a 46 might be pretty smooth but going up to a 48 might cause some problems due to the amount of difference from middle ring 32 gonig to 48.. Might consider Swapping all the chain rings to keep the difference at a minimum...
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Old 07-19-03, 12:57 AM   #15
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Quote:
Originally posted by Dave Stohler
Why bother? By the time you're through, you'll have spent about $800 on a bike that's still heavy, and is nothing more than a glorified hybrid. You can buy nearly any hybrid complete for this much money or less.

If you want a road bike, save up your money and buy a road bike.
I agree with Dave. Maybe keep your mtb intact and look at a good used road bike for the same cost as the intended upgrade. I ain't suggesting what you have in mind is bad, but I wonder if switching to a road-like spec and setup that you might uncessarily 'dilute' your mtb spec and setup. Sounds like you need a hybrid, but from my own experience of hybrids they are a compromise between one style and the other, a sort of jack-of-all-trades, master of none.
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Old 07-19-03, 05:29 AM   #16
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If you only use your MTB for urban riding, then I see now reason to keep its off-road speck. Lots of bike couriers use roadified MTBs. In London, which is quite a flat city, they are often setup with single chainrings for a 1x8 gearing. It is surprising how much easier a single chainring spins. Some other common systems include a road double (39x53) a cyclo-cross style double (36/48), or a road triple (30/40/50). That before you start to consider riding a single speed or fixed.
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Old 07-19-03, 10:42 AM   #17
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lots of food for thought here...

after looking at total conversion prices, even ebaying the pricier bits, it would make sense to find a used roadie. however, i'm pretty sure i want to keep the total below $100.

i really like my atb as a commuter, and don't want to replace it. on crazy rainy days, the disc brakes have (literally) saved my skin.

the breakdown so far:
an ultegra cassette (11-[21|23]) is $38.99 at performancebike.com... i'm banking on the fact that it will fit on a shimano ATB freewheel, am i wrong?

the reason i'm considering a new cassette is that the 3 inner (lowest) gears are totally unused. i don't think i've shifted into them at all in the last 750 miles. the tighter gearing is something that appeals to me (and will inform a future roadie purchase too ). i'll likely get much more usage out of the closer gearing.

i can get a 46T at cambriabike.com for $36. i also found 34-38T middle chainrings which has got me considering replacing those too.

is it possible to remove the inner ring completely, and move the low gear limiter into the middle ring position? or is that just a silly idea?

i think it's feasible to spend $90ish on some newer gearing.

i welcome thoughts and comments. thanks!

-chris
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Old 07-19-03, 07:14 PM   #18
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completely feasable. Actually, that sounds really cool. I would go for it.
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Old 07-19-03, 07:29 PM   #19
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just saw something really cool. campy veloce crank for 60, veloce BB for 15 and tiagra road mech for $5.

http://www.nashbar.com/profile.cfm?s...tTaSW2.yVd5rgg

http://www.excelsports.com/new.asp?p...ajor=1&minor=6

http://www.excelsports.com/new.asp?p...jor=1&minor=13

edit: rats! a flat bar front shifter is needed. that will blow your budget out...I tried!
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Old 07-19-03, 07:56 PM   #20
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that would really nice, unfortunately, my BB is 68x113 so the campy wouldn't fit/i'd hit the chain stay with that crank (i think).

i don't think i'll need a new front derailleur at this point. just a new front chainring, and i'm pretty sure i can raise the FD a few milimeters with no probs (i have never need the lowest gear on my commutes/longer rides).

thanks though!

-chris
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