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bike build advice, MTB cassette for Road?..(12 posts)

bike build advice, MTB cassette for Road?..Bill B
Mar 22, 2001 1:07 PM
Hey, here is my question. I'm putting together a road bike for my wife, we are both new to the road thing. Anyway, I picked up an older Trek 1420 frame ($25.00) that came with a suntour superbe pro crankset that has a 42 tooth small front chain ring. We live in a hilly area and am concerned this might be a little big for her. I was considering running a MTB cassette on it like a 11-32 or 12-34. Is this a good idea, or is it better to try to find a smaller ring to fit this crank, or just replace the crank but I'm trying to keep cost to a minimum. Also, If I run a cassette with that large of ring, will I need to also run a MTB rear derailer to handle the 32 or 34 tooth sprocket? Other than being maybe a 1/4 pound heavier I can't see too much of a problem running a MTB rear end like this, anyone else have an experience with this?
Thanks in advance!
I'd be carefulSpoke Wrench
Mar 22, 2001 4:31 PM
Crank, bottom bracket, front derailleur, rear derailleur, chain, cassette, shifters, rear hub. All of these parts have to work together. You can mix and match some parts with impunity, others aren't going to work without making additional changes. What I'm trying to say is this kind of upgrade could easily turn into a real budget buster.

I've done a fair amount of this kind of upgrade, but I'd want to see the whole bike before I gave you any advice.
re: bike build advice, MTB cassette for Road?..Starliner
Mar 22, 2001 9:20 PM
Not to disagree with spoke wrench, but you need to get him to clarify things, like, what the concerns are regarding each component - such as the hub?

With a MTB cassette, you should at least figure on investing in a new chain and a long cage rear derailleur - less than $100 investment. If that'll be the difference between riding and leaving it in the garage, then go for it.
re: bike build advice, MTB cassette for Road?..Snake Bites
Mar 23, 2001 6:08 AM
Just some generalaltiies,since you didn't ention specifics. Depending on BCD of your crank, you can typically go to a 38 or 39 tooth small ring. A mountian cassette or freewheel with larger cogs is posssible as is a mtn derailer, but your present derailer may be good for a 28 to 30 tooth large cog as is.As Spoke said,it's probbably do-able, but much easier when one has a stash of parts that one can mix and match till the desired result is obtained. Otherwise one has to have more info in order to know what specifics to recommend.
Little more info and another question..Bill B
Mar 23, 2001 8:12 AM
Few things I neglected to mention. The frame came with a very old looking suntour derailer, 5spd I think, and I was planning to replace it anyway, thus the question as to whether running the MTB cassette would work so I could decide which kind of derailer to get. I was think of just a XT MTB rear d. I picked up a new wheel set for it, 105 9 spd. hubs so the 9 speed MTB cassette fits fine. The bike came with old DT suntour shifters(5 position in the index mode) and I am assuming that running them in friction mode should work if I were to run the 9spd MTB cassette and the XT rear D? Or should I pickup some new indexed 9spd DT shifters? If I do that I'm going to get the bar ends to move the shifters up a little. Thanks for all the advice!
Little more info and another question..Starliner
Mar 23, 2001 12:36 PM
First verify that the frame width between rear dropouts is wide enough for your new wheelset. Presuming it is, then sounds like you're on right track. If it's not, then back to square one.

If it's a go, for sure replace the old shifters with some new indexed 9spd DT shifters.
Little more info and another question..mr tornado head
Apr 9, 2001 7:00 PM
I second replacing the shifters if you go 9 speed. Friction shifting 9 speeds is too tricky.

Ever think of getting one or two year old 8 speed stuff? since there were plenty built, there's plenty of parts to keep you afloat for a while.

Yeah, go with a long cage rear der. Front der may be able to handle it, may require some tweaking.

So far, you've got $25 in the frame. Crank, BB and new cassette is going to get you in for another $100-200. What the heck, I'd do it. (in fact, I am - a 6 speed freewheel, old Deore rear der, and 36/52 chainrings up front on a Trek 2300 road frame - works great on the many small but steep hills around here).

If you decide not to, sell it to me!
A timorous suggestion...Cory
Mar 23, 2001 2:05 PM
I'm reluctant to disagree with Spoke Wrench, because every time I think he's wrong, I'm wrong. In this case, though, things may not be as grave as he says, depending on your standards.
Mine are low, and I've swapped cogsets between road and mountain for years, to suit my fitness and where I'm going to ride, and rarely had problems. Some of this is from 10-year-old memory, so allow for that, but:
I think the smallest ring you can use is either 38 or 39 (somebody else said that already). That's not going to make a huge difference. If you need a new rear derailleur anyway, it won't cost any more to get a long-cage one to use with a bigger cassette.
Rear spacing shouldn't be an issue (you can just spread a narrow frame and shove a 130mm hub in there), but whether the hub will accept the new cassette might be. I can't remember when the Trek 1420 was made or what came on it--if it was a five-speed, you may not be able to find a cassette that will work. And I've never been able to get a mix of Suntour/anything else to index, so you may have to live with friction shifting. But if the fates smile on you, you can get something like an LX rear der. for $25, a SRAM chain (PC-58?) for $14 and you're in business. In a primitive, low-investment way, of course, but riding...
Interesting about suntour/ anything...Snake bites
Mar 23, 2001 4:41 PM
...not indexing. I have two bikes set up with 7 sped suntour index shifters. One is a barend and the other is a mountain thumbshifter setup up with otherwise SIS shimano components and it works prefectly. Have had similar luck when using Suntour index capable rear derailers and cassettes,with shimano shifters.It all has to be index stuff,otherwise it doesn't work.
OK, here goesSpoke Wrench
Mar 23, 2001 7:36 PM
I can anticipate three problems with your proposal:

1. Will it work?
I don't know for sure exactly what kind of frame you have. From your description of the unusual Suntour derailleur, I assume it has 126mm drop outs. If it is a steel frame, I'm told you can just force your new wheelset into the frame and it will "set" itself to the new hub width in time. If the frame is aluminum, I'm not at all sure it will work. Eight and nine speed cassettes will both fit your hub. Be sure to get the right chain to match your cassette. You will need a mountain bike rear derailleur to take up the chain slack and to handle the 32 or 34 tooth big cog. Down tube or bar end shifters will solve the front shifting problem because they allow better trimming control to the rider.

2. What have you accomplished?
Assuming your bike originally had a 28 tooth big cog in the back, the lowest hill climb gear was 40 gear inches. A 42 X 32 will give you 35 gear inches. 42 X 34 will give 33 gear inches. These are better, but not huge improvements. Then there is the cost factor: We've talked about a wheelset, cassette, chain, rear derailleur and shifters. You are going to have at least two or three hundred dollars in this by the time you are done and the outcome may still be a little bit iffy. By comparison, the store where I work has Fuji roadbikes with triple chainrings and a new bike warranty starting at $600.00. Every single part is brand new and every single part is designed to work with every other part.

3. What does the wife think?
This bike is for her, right?

Like I said originally, I'd be real careful.
Thanks for the advice, here is what I'm going to doBill B
Mar 26, 2001 1:00 PM
Thanks for all the thoughtfull advice. First the new wheelset was a new 9spd 105/mavic CXP21 set for $125.00 from my LBS and fits the frame fine, just a little tight but nothing I can't overcome with my pinky so I think it's fine, it is an aluminum frame. I decided to picked up a sora triple crank for $50.00 and put a road 12-25 cassette and long cage road derailer on the back and picked up some barend 9spd shifters. Better safe and spend a extra few bucks than have her pissed at me all the way up that 5 mile grade! It is funny what seems like a bargin at $25.00 for the frame and some odd parts turns into a $350 project, but on the other hand I had fun working on it and $350 is pretty cheap for the fairly decent road bike it is now! Thanks again!
I think you are doing the right thing.Spoke Wrench
Mar 26, 2001 2:28 PM
I didn't want to start right off suggesting a triple crank due to the cost considerations, but I think you are doing the right thing. If it was me, I'd chalk part of the cost up to the entertainment value of planning and doing the job. A couple of additional comments:

I don't know if you have a new bottom bracket in your budget, but you are going to need a 68 X 110mm BB. I think I'd also upgrade to a more modern front derailleur too.

I don't know how much cycling prowess your wife has, where you live or how hilly is really is there, but a fairly common gearing change here in St. Louis is to combine a road triple crankset with a mountain cassette and rear derailleur. Cost would be about the same if you do it now.