Bicycle Mechanics - Re-gearing old Mtn bike
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10-18-01, 10:41 AM
I have an old mtn bike. It has 6 gears on the rear cassette (28-14) and the front crank is 46/36/26. I'm thinking of putting on an 8 or 9 gear rear cassette ranging 30/11 or 32/11, and a front crank of 44/32/22 so it will be a little easier to pump up steep trails.
How much work will this be? And since this bike is nearly 20 years old, is it just too expensive? I know I'll need new derailers and such, what other things will I need to replace or problems might I run into? Would it be cheaper to just go out and buy a new mtn bike?
I'm kinda a newbie at bike mechanics. Usually just work on my old tractor and pickup.
10-18-01, 12:04 PM
8 and 9 speed wont fit on 7 speed, much less 6. you will need a new wheel, rear deraileur, and shifter. An LX 9 speed upgrade (chain, cassette, deraileur, shifter) is about $100 at Performancebike.com. add another 70-100 clams for a wheel, and I say start looking for a new bike.
The good news is that 6- and 7-speed rears are more reliable (less misses shifts, broken chains) than 9's, and are cheaper if you can find the parts. 9's are great if you race and keep your drivetrain spotless. I still have a 7 and plan on keeping it as long as possable.
Why not just get a new freewheel with larger cogs? A megarange freewheel will probably suit your needs. You may have to replace the derailleur with a longer cage version, but it sure seems cheaper than the $250 worth of modifications that you were considering.
(BTW, you would also need to spread your dropouts to 135mm to upgrade to 9-speed stuff.)
10-18-01, 02:15 PM
With friction shifters, you can readily replace a standard (not "ultra") 6-speed freewheel with a 7-speed, since they are of approximately equal total width. You do not need a 9-speed cogset.
If you replace your 6-speed 14-28 with a 7-speed 14-32 (~$50) and your 26T grannie ring with a 24 (~$15), your bottom gear ratio will be lowered by a very noticeable 20 percent.
10-19-01, 09:11 PM
Originally posted by stumpjumper
...I still have a 7 and plan on keeping it as long as possable.
Wow, another 7 speed holdout! I have 7 speed on all 3 of my bikes and will continue to as long as possible.
Alex's idea of getting a new freewheel is the best solution. Check www.theThirdHand.com, they should be able to set you up. If you do upgrade, you should be able to run 7, 8, or 9 speed with just a new wheel and cassette in the back provided you are running friction shifters. Usually just takes a bit of adjusting of the derailluer's limit screws. Friction shifters can usually accomodate a wide range of gears.
Originally posted by bikerider
Wow, another 7 speed holdout!
I have three singlespeeds. I also have a three-speed roadster. The rest of my bikes use 5 speed freewheels, except the mountain bike which sports 6-speeder.
10-21-01, 09:24 AM
I have a similiar bike that i'm fixing up to use as a commuting bike. I thought that since it has a 6 speed rear that it was a freewheel, but now I find out that it is a casssette.
I've noticed that some people are recommending getting a new freewheel while in your original post you state it is a cassette. If it is a cassette, I think it's going to be harder to get a replacement.
By the way, my bike has a 13-30 cassette.
10-26-01, 02:55 PM
Sometimes you can change the cassette from a six or seven to an eight or nine using the same hub. It's best if you have friction mode available on your shifters.
Get a new cassette body and see if it will fit the hub
If it fits, get a longer axle and re-assemble, you may need to get a different cone and dust cap to fit the new cassette.
Check for clearances, (cogs and chain to frame), and overall width at locknuts. ie; is it 126mm? 130mm? 135mm? is you frame spacing 130,126 135?
You may need to spread your rear triangle, usually best to take it to a shop, unless you're capable, adventureous and have a STEEL frame.
Re-Align drop outs
Re-dish the wheel
Slap on that new cog set and do final derailleur adjustments
go test ride it
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