What to consider when changing wheel size?

[krashTest]

The bike is a CCM from the 70's, entry level with steel frame.

I'm not certain on the size of the rim but it sports a 26 x 1 3/8 tire.

I would like to replace the rim, what are my options? I would like to find a rim that can accommodate a tire with more width as would like try using a snow tire.

How can I determine my size restriction?

[DaveM]

Start here:
http://sheldonbrown.com/tire-sizing.html

26 x 1 3/8 is either a 590 or 597 mm diameter wheel depending on whether it's a Schwinn or not.
The two most common sizes you could switch to is the 26 mtn bike size (559mm) or "700c" (622mm)

650B is a size that has started to regain popularity (584mm) and is the closest to what you've got. But you would have limited rim and tire choices.

What you can fit comes down to clearance on your frame & fork as well as brakes. Remember that these measurements are diameters, so you need to think in terms of radius's to figure out how much room you have to go up or down. Remember too that wider tires are generally taller as well.

My guess would be that you could go down to a 26" mtn rim. But the big worries would be clearance for the tire in the frame/fork and whether your brakes would have enough reach to still hit the rim with the pads.

[krashTest]

Thanks for sending the link. At first glance its nothing short of a nightmare, I think I'd rather attempt to split the atom! It certainly requires a reread to get this to register.

I would be pleased if I could get a 26 (559mm) mtn rim on. My concern is the clearance as my fork tapers.

I was also planning to use a mudguard and caliper brakes which would require some hard measurements. I was hoping to find a lazy route but it would seem best that I measure my options.

[DaveM]

You are right to worry about tire clearance and making sure that the caliper brake will have long enough reach to get to the rim. I also neglected to mention that if you get pre-built 26" wheels, you'll probably have some issues with the rear axle being too wide for your frame. There's ways to deal with that as well, but it's another thing to deal with...

If you want to put together a beater, winter bike, the cheaper option may actually be just to find a beat up cheaper mtn bike and put some fenders on it. Won't be as fun a project, but depends on your goal

[nfmisso]

Depending on how much you want to spend.....

You could replace the fork with one intended for ISO559 rims - I did that on my 310 (the original fork was damaged), but am using a ISO590 rims on the bike front and rear. My 310 originally had ISO630 rims. They did not provide enough clearance for fenders. ISO 622 would not have provided enough extra clearance, so next step with tire choices that suit me is ISO590.

For the back, you can either go long reach brakes, or make an adaptor plate as Sheldon shows.

Linear pull and modern dual pivot side pull brakes are much more effect than earlier brakes - it is amazing the difference.

[krashTest]

I have thought about replacing the fork. Could the slight change in the bikes geometry cause any issues?

It's been recommended to me as well to use cantilever brakes for additional stopping power though my current fork doesn't have any fittings to support them.

I don't have any experience with modern dual pivot sidepulls but I will be certain to check them out. Thanks Nigel!

[nfmisso]

(01-14-2013, 03:53 PM)krashTest Wrote:  I have thought about replacing the fork. Could the slight change in the bikes geometry cause any issues?

It's been recommended to me as well to use cantilever brakes for additional stopping power though my current fork doesn't have any fittings to support them.

It is highly unlikely that you will notice any change in geometry.

I would not go with cantilever brakes - I switched from cantis to linear pull brakes on both my commuter and tandem because of inadequate stopping power.

Our Tandem:
http://forums.bikeride.com/thread-2920.html

My commuter:
http://forums.bikeride.com/thread-3036.html

[krashTest]

My bad, I meant to say calipers instead of cantilever. I still get them mixed up.

Nice job on the commuter btw.