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MTB to Cyclocross?

Old 08-13-04, 10:52 AM
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rykoala
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Picture attached of my MTB. 88 or 89 RockHopper. Love the bike. Was planning on overhauling the bike soon. I quickly realized that I may as well buy a new bike for what it would cost to overhaul it and put newer components on it, etc. So, here is my question. A stupid one that I probablly know the answer to, but my mind won't stop thinking about it so I need to put this to rest.

For a MTB, the bike is pretty light. 30lb probably, max, but nevertheless its not super heavy. I'm OK w/ that part of it. It has a biopace mountian triple in the front, and that is fine w/ me. The brakes, cantilevers front and back, but the back ones look like a horseshoe shape, with each brake crossing over to the other side, and with a yoke just like the front brakes. Chainstay mounted.

I am reasonably sure that it'll fit 700C wheels, but I have to measure. How big around is a 700C with a 38mm tire on it? Since the seatstays have no brake bosses on them, I figure I could take it to a frame builder and have them added. How much would that cost? For the front, I *think* there may be room to put standard v-brakes on it, with the mounts for the canti's being high enough that the V-brake ould reach the 700C rim. Any thoughts on that? Again, have to do some measuring for that one. Worst case I'd have to have new bosses brazed onto the fork.

For wheels I'd get mavic speedcity rims most likely, or another strong 700C. Have the rear one laced up to an appropriate hub for the 126mm spread dropouts. Or buy one already done up.

I'd keep the MTB shifters I have, or get new ones. Doesn't matter. Flat bar still in the front. Don't think I'd need new brake levers. The ones I have are very good. I also have Shimano Deore derailures front and rear. Those would get overhauled, if needed. Definitely new sprockets in the rear derailer, and a thorough cleaning for the rebuild, of course.

Someone just tell me I'm crazy and to go buy a Surly Cross Check or a Soma Double Cross please? Or, tell me why this wouldn't work so I'll stop thinking about it! I just have to justify *not* trying to re-use this perfectly good steel frame.

Thanks tons!!

PS- I know this is very similar to a thread I posted a few days ago, however I have more direct questions this time around, and I didn't feel like reviving a week old thread for everyone to read through ;-)

Last edited by rykoala; 08-13-04 at 11:02 AM.
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Old 08-13-04, 11:52 AM
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jeff williams
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I think the frame is a bit old, and heavy.
With upgrades, you may be able to get say 4 pounds off, but it is not a frame design that was used for racing or 'advanced' riding.

An idea, is to replace only>>parts that can be swapped to a new frame. Pedals, wheels, bars etc. When almost all components are replaced...get a different, more advanced steel frame (not new, unless you got BIG cash.) And swap everything over.

This is kinda how I build, it's more expensive, and takes time..but I love it. And my bikes got EXACTLY what I want on it, not factory mid level components. (which I would break or remove anyway.)

I think if you like the frame, get some used HQ parts and upgrade, but be realistic.

I put cash into my 90's frame, but it's a way advanced racing frame, worth it as to replace, I'm looking @ $1000's not $599.

I love old bikes, and they are worth rebuilding if steel and not raced out. It's really your call.

>jef.
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Old 08-13-04, 01:22 PM
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What would you gain by going to 700c wheels on the bike? It seems like a money pit idea to me. If you just want to make the bike more efficient for commuting, go w/ 26" slicks. If you're set on the idea of 700c wheels, get a new bike/frame.

BTW, I had an old Rockhopper that I turned into a nice, light singlespeed. I bought a Cross Check for commuting and road riding.

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Old 08-13-04, 01:52 PM
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rykoala
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Originally Posted by bbaker22
What would you gain by going to 700c wheels on the bike? It seems like a money pit idea to me. If you just want to make the bike more efficient for commuting, go w/ 26" slicks.
Well, I'd get taller gearing (700C vs 26") so I'd be able to go faster, and the 700C could fit 23 or 25mm tires for much less resistance than the 26" slicks (well, semi-slicks, they have grooves cut in them very sparsely) plus I could fit 38mm knobbies for off-roading, if I wanted.

Originally Posted by bbaker22
BTW, I had an old Rockhopper that I turned into a nice, light singlespeed. I bought a Cross Check for commuting and road riding.
Yeah I thought about getting a fixie/SS wheel for it, but then I'm back to wanting 700C's for that purpose. And I'd still want a rear brake
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Old 08-13-04, 03:05 PM
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Gonzo Bob
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WOW! That bike is sooooo similar to mine. Are you sure it's not an '87? I bought my Diamondback Apex in '87 and it also has a U-brake. But I thought the U-brake was used on MTBs for only one year. Okay, maybe some '88s used them too.

Your rear hub is probably 130mm 6-speed Uniglide cassette. At least that's what was on most MTBs of that time. A very limited selection of Uniglide cassette cogs is available at www.loosescrews.com You can get complete cassettes as well as loose cogs. My bike originally came with 14-32 but I changed that to 13-28 almost right away. When I put slicks on it, I change to 12-26 for more road-worthy gearing (I bought a 12-34 cassette and loose 13 cog from Loose Screws and changed the 12-15-17-21-26-34 to 12-13-15-17-21-26).

If all you're looking for is a higher gearing, you could get a smaller cassette. You could also look into getting a larger chaining. A 50T or 52T would probably run fine with that crankset and front derailer.

700x23 won't offer much less rolling resistance than a 26x1.4" slick (or whatever you've got on there now). So I'd stick with 26" wheels.
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Old 08-13-04, 03:24 PM
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Hey there Bob. It very well could be an 87. You said yours is a diamondback? Maybe Specialized used the chainstay u-brake longer? I don't now.

The rear is actually a 126mm, but I'm running a 7spd wheel in it right now. Soon it will match the front, a bombproof 26" with XTR hubs and Mavic A231 wheels. VERY strong.

I have though about getting a 50 or 52 tooth chainring, but I have been under the impression that the narrow wheels and tires (700C's) are what really bring in the speed because of less rolling resistance. Is that note the case, as you say? Maybe I have a big misconception here.

PS- went and looked and I have a 30-13 cassette now.

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Old 08-13-04, 04:02 PM
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Originally Posted by rykoala
The rear is actually a 126mm, but I'm running a 7spd wheel in it right now. Soon it will match the front, a bombproof 26" with XTR hubs and Mavic A231 wheels. VERY strong.
Puzzling. Most 7-speed MTB cassette hubs are 135mm. Is yours a cassette hub or a freewheel hub? Or is it perhaps a "road" hub?


Originally Posted by rykoala
I have though about getting a 50 or 52 tooth chainring, but I have been under the impression that the narrow wheels and tires (700C's) are what really bring in the speed because of less rolling resistance. Is that note the case, as you say? Maybe I have a big misconception here.
Yes, the rolling resistance of a 700x23C tire at 110psi is probably a bit less than a 26x1.4" slick at 80psi so it would likely be a little faster. By how much? My gut feel says not a lot. Rolling resistance is not the primary resistive force. Air is. And the main reason a road bike is faster than an MTB with slicks is because the road bike has a more aerodynamic riding position.
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Old 08-13-04, 04:06 PM
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Maybe its not a cassette, then? Maybe its a freewheel hub then? How do I tell the difference? <kind of embarassing not to know for sure>

Thank you for the explanation of what makes a road bike faster. NOW I UNDERSTAND. I feel like a dork!

I do know that the hub/cassette or whatever it is has a lockring I can take off rather easily.
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Old 08-13-04, 04:18 PM
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Sounds like a cassette. Frame spacing seems to be all over the place for 7 speeds...

http://www.sheldonbrown.com/frame-spacing.html

baker

Last edited by bbaker22; 08-13-04 at 04:26 PM.
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Old 08-13-04, 04:43 PM
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I Just looked the one I have now is a hyperglide cassette, 30-13. Can the cogs be changed easily on this one? Will it take a 12 or 11?

Scratch that, just answered my own question. I see a 12T HG cog for sale at loosescrews.com....
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Old 08-13-04, 04:46 PM
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Originally Posted by rykoala
I do know that the hub/cassette or whatever it is has a lockring I can take off rather easily.
A lockring means it's a Hyperglide cassette hub. With Uniglide cassettes, the smallest cog threads on and there is no lockring.
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Old 08-13-04, 04:53 PM
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Originally Posted by rykoala
I Just looked the one I have now is a hyperglide cassette, 30-13. Can the cogs be changed easily on this one? Will it take a 12 or 11?
Yes. You can change the cogs. If you have trouble finding new 7-speed cassettes, you can just buy an 8-speed cassette, leave out one cog, and replace all the loose spacers with the ones from your 7-speed cassette.

All Hyperglide freehub bodies can take a 12. Some (non-compact bodies) require a thin 1mm spacer to be placed on the freehub body first in order to use an 11. See http://www.sheldonbrown.com/k7.html#hyperdrivec
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Old 08-13-04, 11:41 PM
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Well after doing much research on sheldon's site (http://www.sheldonbrown.com/k7.html) I have found that I am currently running a Shimano "G" 13-30 7 speed cassette, and that another wheel I have has a Shimano "E" 12-28 which is an 8 speed cassette. The 8 speed is the Mavic A231/XTR combo which is nice and strong. I have the shifter off of the parts bike and so I'll swap to that as soon as I get the wheel trued up. Its only a tad bit out, but it hops. It DOES fit my dropouts tho

Well I have learned much in this discussion thus far. THANK YOU to all who replied!
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