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I just bought an older road bike with 27" wheels. I am curious if I can mount 700 wheels (typical road size) on it. Has anyone ever done this?

The main reason I am interested in doing this is so that I can have more tire selection. I like the body positioning on my road bike but since I live in a rural area I do a fair bit of biking on gravel/dirt roads and pathways.

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4 Answers 4

up vote 7 down vote accepted

Yes, this has been done and is very often done for the exact reason you mentioned: far greater tire selection.

In a general sense, the important considerations you must make stem from the difference between a 700c wheel and a 27" wheel. If we look at a more precise measurement than the common nomenclature, the bead seat diameter, the difference is more obvious:

  • 700c wheel: 622mm BSD
  • 27" wheel: 630mm BSD

This means that the former is 8mm shorter in diameter than the latter, and when you mount a 700c wheel to a bicycle with brakes set for a 27" wheel, they will be mis-aligned by 4mm (a significant amount).

Depending on what type and variety brakes you have, you may or may not be able to reposition the brake pads correctly. In the case that you can't, you will be able to replace them with brakes designed to have a longer 'reach'.

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3  
Sheldon Brown also has a nice explanation of reach a bit down on this page: sheldonbrown.com/gloss_ra-e.html (look for the "Reach" heading) –  jeffesp Aug 26 '10 at 18:53
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@jeffesp Hi Jeff, I'd recommend taking a look at "Avoiding ‘Just Buy A New One’ or ‘Here’s A Link’ Answers" in the meta section: meta.bicycles.stackexchange.com/questions/28/… –  Dustin Aug 26 '10 at 19:10

I am just about to do this myself. Re-use the old hubs to save your sanity. This may involve replacing the spokes if they're not compatible with the new rim. A new set of front and rear brakes will run you about $70. You should replace the brakes if they are the Diacompe-type vintage from the 70's or 80's. They are too weak by today's standards. Tecktro makes a great dual pivot design that's a great replacement.

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Dia-Compe centerpull brakes can work very well with new or well-maintained cabling and new brake pads. The sidepulls are often weaker and hard to center, however. –  Alan Gerber Mar 7 at 16:18
    
So you're going to replace the rims? I think the OP was talking about just throwing a set of pre-built 700c wheels onto his 27" frame. –  jimirings Mar 7 at 16:51

True the brakes may be an issue. The other problem you will encounter is different spacing on the hubs. Usually you can spread the fork and frame to fit. Borrow some 700s from a friend or stop by your LBS to test fit a set of wheels. You'll know very quickly that way.

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True, but if necessary building a wheel with new rims and, if equivalent new hubs really aren't available, reusing the existing hubs would give him the increased tyre choice and same spacing. If his hubs are worn out and need replacing, he'll have the same spacing issue even if he keeps the old rim size. –  armb Jul 26 '13 at 16:33

Yes it can be done, but more than likely you will need to buy new brakes as well unless yours will adjust to the 700 wheels. You will also need to find 700 wheels that will have the correct number of rear cogs for your existing derailleur system, or get ready to upgrade that.

So, it can be an inexpensive change, or costly depending on your bike and what rims you can find.

A less expensive way out, is to ask your LBS if they can order tires, or just purchase tires off the internet stores. There is a much larger selection at places like:

http://www.sheldonbrown.com/harris/tires/630.html

Take a look at that first tire the cross tera - if you go off road quit a bit, that would be more like a XC tire. Otherwise an extremely good choice as well is the Schwalbe Marathon - they are made for 700 rims as well and are an extremely good tire.

Whatever your decision, best of luck to you.

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Awesome link! Thanks! –  sixtyfootersdude Aug 29 '10 at 20:09

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