Wheel Size?

I cant seem to figure this out?

If a bike comes equiped with 700c wheels can you replace them with 650c? Maybe replace the brake calipers with some that have a longer reach?

I may try to modify an older road bike to a TT bike and if so would like to put the smaller wheels on it.

My suspision is that the frame is manufactured for one size wheel or another.

Thanks

Wheel sizes generally aren't interchangable for a particular frame. A 700c wheel is somewhat larger than a 650c.

The only place I've seen a wheel size used on a bike not originally designed for it, was a custom-made 650c wheelset built for a mountain bike (which normally takes 26" tyres), so it could use skinny road slicks. This bike had disc brakes, so brake caliper reach etc. was a non-issue.

Depending on how old the bike is, it may have a different sized rim (i.e. neither 700c nor 650c.) Are there any markings on the tyre that's on it right now?

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Peter
Cannondale Synapse Carbon Scalpel Cyclocross Ultra

The bike I want to equip with time trial gear is a 3 year old TREK. I kind of fugured that Ill have to stay with 700c wheels that cam on it new.

Thanks for the reply.

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