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Old 08-10-08, 05:31 AM   #1
omdemarseille
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Another mountain bike for road riding...

Hi,

I currently use my Trek mountain bike on the road only and intend to try and make it as fast as possible. As much as I would like to, I don't intend to purchase a road bike as i've poured enough money into this bike which will go to waste (and i've done a lot of miles on it and will not part with it). I currently run a pair of Specialized Nimbus 26x1.5 mbr slick/road tyres which are pumped up to 75-80psi which I believe are pretty much the max. I was thinking of changing these to some Specialized All condition pro 26x1.0 road tyres which are obviously thinner and possibly lighter and they apparently inflate to over 100psi. Do you think this is worth the improvement over the 1.5s?

The front chainring is a Shimano Deore with the largest outer ring being a 44T and the rear cassette has a minimum of 11T. Is it possible to change just the top outer ring on the front chainset to a 48T? Will this mess up the front derailer configuration bearing in mind the other 2 chainrings (inner and middle) will be 22T and 32T? or am i better off changing the whole chainset (and maybe the bb to hollowtech as I can't find a square tapered 48T chainset anywhere) with proper 48T-36T-26T setup? Is this upgrade actually worth it for the extra 4 teeth gain (i know road bikes have 50+ teeth)?

I may also swap out the air forks (Tora 302s but with no lock out ) to a rigid carbon Bontrager fork but thats the last option on my list.

Many thanks for any input!
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Old 08-10-08, 06:02 AM   #2
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Keep the Trek.
Get a Used road bike.
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Old 08-10-08, 09:24 AM   #3
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Looks like you're wasting money time and effort. Get a roadie for about a grand then upgrade as parts wear. Try a roadie, you'll see a world of difference worth the money.
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Old 08-10-08, 10:29 AM   #4
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Yes, 1.0 slicks are likely to make a huge difference from the 1.5s you run now (although, every tire type is different, and I have not ridden that particular brand).

Yes, swapping out the sus fork for a properly sized rigid one will make a huge difference. Both in weight and in how much pedal energy is lost to the suspension.

Is it worthwhile though? Hard to say. In purely financial, objective terms, it usually makes more sense to find yourself the right platform from the get-go. Even an older steel roadbike is going to be substantially better than you will ever make the MTB. And far cheaper, also.

For me, I would say that converting an older rigid MTB to urban use with slicks makes a lot of sense. For the price of new tires you get something which is quick and tough enough for the job. But buying a new fork? Unless you stumble upon a great price for exactly the right used one, you will end up spending too much money. And trying to end up with something which is really a road bike? Ultimately you will run up against the raw facts of frame weight and geometry.

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Old 08-10-08, 10:32 AM   #5
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Thanks for your all your inputs, i think its time to start saving lol

Have a good day
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Old 08-10-08, 11:10 AM   #6
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Originally Posted by jgedwa View Post
Yes, 1.0 slicks are likely to make a huge difference from the 1.5s you run now (although, every tire type is different, and I have not ridden that particular brand).
I'll certainly agree on the huge difference thing.

Measure the inside width of your rims and go to Sheldon Brown's website to see if your rims are a match for 1.0 tires. If your rims are too wide you'll find yourself getting frequent pinched tube flats.
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Old 08-11-08, 01:33 AM   #7
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I have a pair of Mavic 717 Disc rims which have a sticker on them indicating the tyre range, 2.5 to 1.0 so can i assume from this that the 1.0 slicks will be OK (max PSI for rims 113psi)? or shall I also use Sheldon Brown's measuring technique as well?
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Old 08-11-08, 12:54 PM   #8
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Something to keep in mind is that 1" tires are going to drop your overall gearing. Plug in your numbers and check.
http://sheldonbrown.com/gears/

I'd also be concerned about putting tires that skinny on MTB rims. I've got 1.3" tires on a set of Sun Rhyno Lites,and they just fit. As for the sticker,1-2.5" is a huge range. I'd honestly be surprised if the rims could properly handle tires as skinny as 1" and as wide as 2.35". The bike with the Rhynos came with 2.35" knobbies,and as I said,the 1.3's are pretty much the low end of safe. If you want speed,go with a lighter tire. Conti Sport Contacts in 1.6" are only 500gr. The Nimbuses are heavier,how much I can't say cause Spec's site is down right now and Google fails me.

A rigid fork is a very good idea for street riding. Less weight and less dampening of your pedal strokes.

You might be able to swap rings. Depending on the derailleur,you might be able to tweak it to take a 48t. Most MTB derailleurs top out at 44t. 48 to 32 jump is pretty big though,and you don't really need a 22t on the street unless you're going to be hauling serious weight up hills or pulling a trailer,so you'd prolly want to go with a 48/38/28 or 48/36/26. If there's a bike co-op or similar near you,you should be able to find a crankset from a hybrid for cheap.
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Old 08-11-08, 04:33 PM   #9
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You could get a used road bike for what the crank and fork upgrade would cost you.
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Old 08-11-08, 07:29 PM   #10
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As for larger chain rings, make sure you have enough clearance to the chain stay. You don't want a ring rubbing it!

I put these cranks on my bike for the short arms, but for the price, it would be a very inexpensive experiment-
http://www.nashbar.com/profile.cfm?c...20ATB%20Cranks
The short arms WILL change your sense of gearing. You'll be able to spin faster, but with less force.
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Old 08-12-08, 01:49 AM   #11
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Cheers guys for the advice, just noticed (I don't have the bike in front of me earlier) the label actually said 1.0 > 2.1 tyre width range. About the cranks, has anyone had experience installing Shimano's Hollowtech cranks before? I've read that one has to file down, flatten the BB faces on the frame as the bearing cups sit on the outside rather than inside as older tapered models do? - just in case I do come across a good deal on a 48T chainset!
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