Bicycle Tutor

Hi everyone, i am starting a project within the next few weeks to convert an old mountain bike into a road bike. Unfortunately at the minute the bike is at my dads and i have no way of getting there to take measurements so i can buy new parts. Its a DiamondBack Topanga (approximately 1992/93 model). I want to purchase a new stem but cant get to it, to see whether it takes a 1 inch or a 1 1/8 inch stem. As you can probably tell, i'm a novice, so any help would be much appreciated! Cheers guys. Davepen

A road bike has a quite different geometry than a MTB.... just keep that in mind. The weight distribution on the wheels will be quite different than the framebuilder intended and the result might very well be unrideable.
Cannot help you with the original question, except that 1" used to be standard for the steerer outer diameter and the stem would be 7/8 then.

ok thanks. so you would suggest not bothering to convert and maybe just upgrade some of the components?

Well, you could give it a try, but I think that the end result might be... well... not quite good. You could try to get e.g. Paterek's framebuilding book or other literature and try to figure out how the handling might change and how to correct that (other fork?).

I would try to find what needs to be replaced and then probably get some last year mid range MTB components. While you can score a bargain that way, be aware that it is easy to spend some serious money... shifters, dérailleurs, hubs (or even wheelset, depending on the state of the wheels), crank set, brakes (plus chain, sprockets, and some small stuff that you'd need to replace anyway). Could be a nice project, though, and you'll learn a lot!

Oh, and concerning the original question: why do you want to replace the stem? Is it broken or too long / too short?
Oh, and is it a threaded or a threadless steerer (above I assumed that it is threaded, but I'm unsure at the moment).

Something you could do is get MTB size road tires. They will be as big as MTB tires but have better rolling distance, and you could use the same wheel set.

Well, i was just talking to a mate and he said that the likely hood is that i will need i new one. But iv since spoken to my dad and he reckons that it doesn't need changing. Yea its threaded!

I found this sight for the spec:
http://www.bikepedia.com/QuickBike/BikeSpecs.aspx?ItemID=40517

it is this model and colour:
http://cgi.ebay.co.uk/DiamondBack-Mountain-Bike-/140391548356

Thats the only info i can get until i go to may dads....which i'm hoping to do on the sat coming.
Yea i think the project will be good am looking forward to it, just being a novice, am learning as i go.

I like the idea of MTB size road tires tho!
Cheers for the help guys! This is ace!

(May 31, 2010 02:21 AM)davepen Wrote:  Hi everyone, i am starting a project within the next few weeks to convert an old mountain bike into a road bike. Unfortunately at the minute the bike is at my dads and i have no way of getting there to take measurements so i can buy new parts. Its a DiamondBack Topanga (approximately 1992/93 model). I want to purchase a new stem but cant get to it, to see whether it takes a 1 inch or a 1 1/8 inch stem. As you can probably tell, im a novice, so any help would be much appreciated! Cheers guys. Davepen

Get the bike back first. There are quite a few variations in stem sizes.
I'm referring to the clamp size for the bars.
You need to measure this before buying any new bars.
If bars are not available in the size you want then you may have to get a new matching stem.
You might want to alter the stem length after to get the right reach but that will come with experience.

(May 31, 2010 09:30 AM)cyclerUK Wrote:  

(May 31, 2010 02:21 AM)davepen Wrote:  Hi everyone, i am starting a project within the next few weeks to convert an old mountain bike into a road bike. Unfortunately at the minute the bike is at my dads and i have no way of getting there to take measurements so i can buy new parts. Its a DiamondBack Topanga (approximately 1992/93 model). I want to purchase a new stem but cant get to it, to see whether it takes a 1 inch or a 1 1/8 inch stem. As you can probably tell, im a novice, so any help would be much appreciated! Cheers guys. Davepen

Get the bike back first. There are quite a few variations in stem sizes.
I'm referring to the clamp size for the bars.
You need to measure this before buying any new bars.
If bars are not available in the size you want then you may have to get a new matching stem.
You might want to alter the stem length after to get the right reach but that will come with experience.

Ok thanks thats great. Hopefully ill be able to get bars that fit the clamp size

You should. It is not that old. Problems do arise with French bikes older than 20 years or so...

First thing you could do is try to find an older group set somewhere online, some mid-range stuff of last year (or the year before...) and look at the prices. Then, when you have the bike back, look at the wear on the components. It is likely that the chain + sprockets + chain rings are worn. The rear dérailleur might be worn, too. You'll find this out if you cannot tune the shifters correctly (the springs inside become too weak). If that is the case, either find replacement parts or look at the price difference to a complete upgrade, basically you only need new shifters then (well, you'll have to get the other stuff anyway).

Ok ace thanks, hopefully ill be getting the bike back this week and will be starting the following week! Ill keep you all posted!