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An easy "How do I" question(9 posts)

An easy "How do I" questionRode Warrior
Nov 8, 2002 2:22 PM
How do I convert my old road bike to a 'cross bike?

I know that I won't be able to run cantilever brakes, so I need to know how large of a tire I can use with RSX-100 brakes. Also what sizes are available for 'cross tires? I have 46cm handlebars on the bike now, will this be a liability, or a benefit? Are 'cross bars different from normal road bars in respect to the drop?

I would really like to race some this winter, so any advice would be appreciated.

An easy answerhycobob
Nov 8, 2002 3:14 PM
You can too use canti or v-brakes...braize on the posts and voila! If you don't trust yourself with a torch get with your local riders and there's somebody near you that will do the job. Your LBS should be able to hook you up with the posts cheap...if not the braizing too. You might need to cut out the tie between the seatstays that the rear brake caliper mounts to. If this worries you, get a cheap v-brake booster to add lateral stiffness to the rear triangle. Good luck
An easy answerRode Warrior
Nov 8, 2002 3:35 PM
Sorry, I neglected to mention it is an aluminum frame. I would be fine with a steel frame, but not aluminum.
Still the same answer...almosthycobob
Nov 9, 2002 5:31 AM
Your aluminum seat stays have a 99.999% chance of being straight gauge tubing that brake posts can be heli-arced to. This isn't uncommon. Your fork should be steel or chromoly which can be braized.
One possibly accurate answer...Silverback
Nov 8, 2002 4:36 PM
I'm not a 'crosser, but I do have an old bike with RSX-100 components that I've done a lot of fooling with, so I can help with the tire question:
At least on my Specialized, 700x32 road tires (very little tread) will fit, but 700x35 won't--they rub on the bottom of the brake arch in front and clear by only a millimeter or so in back. That's with Panaracer Paselas, which are taller than many road tires, but narrower than any cross tires I've seen.
On a singlespeed I use for a beater and mud bike, I have some 700x35 Ritchey 'cross tires, and just eyeballing them, there's no way they'd go under the RSX brakes. The frame they're on uses cantis, so I can run 'em with fenders if I want.
Let's take a measurement!Kerry
Nov 9, 2002 6:10 AM
Since every frame will be different, there's no standard answer on how big a tire will fit with a given brake set. It can even be different front to back, since the brake bridge spacing is determined by the frame builder and the fork clearance is determined by the fork manufacturer, not usually the same folks. So what you need to do is measure the clearance you have on your current bike. If you're running 23mm tires (measure them, don't believe the label) and you have only 2 mm clearance, then a true 25 is the biggest you can take (leaving 1mm clearance). If you're going to be doing muddy courses, you'd like at least 5 mm clearance, and more is better. Look at all the places where the tire clears the frame, and measure the gaps. Each 2 mm increase in tire size will chew up 1mm of those gaps. While others are blithely recommending brazing on new fittings, that is a whole 'nother step (and it still might not gain you anything on your fork clearance). A frame builder would have the jigs to get the canti mounts in the right place and properly oriented - your local welding shop could do the job but you'd have to wonder about placement and orientation. I'm not sure I'd spend money on a frame that was RSX equipped in the first place.
re: An easy "How do I" questionSnyder
Nov 9, 2002 6:32 AM
Please post how the conversion process goes, as I also have an older aluminum bike that I have been thinking about "crossing."
re: An easy "How do I" questionda cyclist
Nov 9, 2002 3:41 PM
If you just want something that's rideable, then there isn't much to do. First you need to find some knobbies that will fit your frame/brakes. Throw a wide range cassette on the back like a 12-27, keep the chain on the 39 up front and you're done.

If you're a strong rider already, you could probably get by with a 42 up front (standard for a single ring set up). The only other change would be to reverse your brakes, but that isn't neccessary.
uneventful updateRode Warrior
Nov 11, 2002 10:03 AM
I spoke to someone in a shop in Boulder, and after I get my rear wheel rebuilt, I will take the bike to them so we can check the clearance with some 700c x 30 tires. I think based on info from other posters I may be successful with this.

Updates to follow