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Old 03-27-07, 10:59 AM   #1
carail
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Replacing 27" with 700c advice

Im replacing 27" wheels on a old road frame for new 700c wheels. I know im gonna have to lower the brakes by 4mm (i dont know how yet ).
I havent bought the wheels yet an im also gona get new brakes (front and back).
Anybody got any experience on what im gonna have to do exactly. Tips and or tricks for me before i get started that are gonna make my life easier .
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Old 03-27-07, 11:15 AM   #2
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Regarding the brakes, you should measure the reach needed from the brake mount hole to the center of the rim brake surface of a 700c rim, then make sure you get brakes that will adjust for that much reach.

The other issue might be rear dropout spacing. Since most older bikes with 27" wheels have freewheel hubs that require less space between the rear dropouts than newer cassette hubs, you likely have a frame that doesn't have the correct dropout spacing for a modern hub (assuming you're going to be using a modern cassette hub).

Bikes from the 1970's and very early '80's typically are spaced for 120mm hubs, and from the early '80's thru the late '80's or very early '90's, 126mm spacing was the common standard. Modern road cassette hubs are designed for rear dropouts with 130mm spacing.

The good news is that this is not by any means an insurmountable problem, especially since most older bikes have steel frames. If, for example, your bike currently has 120mm rear dropout spacing and you want to use a modern road hub, you will need to cold set the rear triangle (assuming your frame is steel), which means you will permanently bend the stays apart to fit the wider hubs. Instructions for this can be found on Sheldon Brown's website, under "frame spacing" I believe. If your frame has 126mm dropout spacing, you should be able to spread the frame by hand and squeeze a modern hub in since it's only a 4mm difference, but again if you really want to set it up right it can be "cold set" to 130mm-

edit: here's the link to Sheldon's site regarding cold setting a frame.
http://sheldonbrown.com/frame-spacing.html

And if you have to change the dropout spacing quite a lot (like 10mm), you should probably have your dropouts re-aligned after cold setting, the process does affect the dropout alignment. If you only change from 126mm to 130mm or something similar, it's not enough to be a problem from my experience.

Last edited by well biked; 03-27-07 at 11:48 AM.
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Old 03-27-07, 11:44 AM   #3
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Thats exactly what i was thinking of doing, the spacing is 126 and im looking for a new 9 speed casette. Its a steel frame so i dont see any problem using Sheldon Brown's cold set technique. Im more woried about getting the brakes right since i dont have any 700c wheels to try on the frame.
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Old 03-27-07, 11:51 AM   #4
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Quote:
Originally Posted by carail
Thats exactly what i was thinking of doing, the spacing is 126 and im looking for a new 9 speed casette. Its a steel frame so i dont see any problem using Sheldon Brown's cold set technique. Im more woried about getting the brakes right since i dont have any 700c wheels to try on the frame.
You can measure the reach needed by measuring from the center of the brake mount to the center of the brake pads on your existing brakes (or the center of the 27" rim's brake surface), and then adding 4mm. Then when you shop for new brakes, make sure the reach adjustment falls within the range you need-

Last edited by well biked; 03-27-07 at 12:14 PM.
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Old 03-27-07, 12:03 PM   #5
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Simply loosen the stud on the brake pad and slide the pad toward the axle. If it now "misses" the 27" rim, you are good to go. If it moves less than that than???
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Old 03-27-07, 12:06 PM   #6
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Originally Posted by Bill Kapaun
Simply loosen the stud on the brake pad and slide the pad toward the axle. If it now "misses" the 27" rim, you are good to go. If it moves less than that than???
But I believe carail wants new brakes-
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Old 03-27-07, 12:10 PM   #7
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You can still find 27" rims and can build new wheels with them.
http://www.sheldonbrown.com/harris/rims/630.html
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Old 03-27-07, 12:52 PM   #8
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I did a similar change recently, and found the original brake calipers were not long enough to reach new rims. Three clicks in Sheldon's website later I was enlightened: http://sheldonbrown.com/harris/brake-calipers.html I ended up using a set of Tektro brakes and all is well.
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Old 03-27-07, 01:18 PM   #9
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I did the same on my commuter/roadie, and I was able to reuse my old brakes.
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Old 03-27-07, 02:34 PM   #10
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I did the same on my commuter/roadie, and I was able to reuse my old brakes.
I got away with using the front brake and replacing the rear on a bike I sold last year.
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Old 03-27-07, 02:35 PM   #11
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Quote:
Originally Posted by Barabaika
You can still find 27" rims and can build new wheels with them.
http://www.sheldonbrown.com/harris/rims/630.html
And here:
http://www.bikepartsusa.com/view.asp...l&f_c2=27+Inch
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Old 03-27-07, 06:34 PM   #12
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Ive thought about getting 27'' wheels, but i havent seen anything i like yet (i want something thats black and looks fast ). Thanks for the link howmanyis2many.
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Old 03-27-07, 06:47 PM   #13
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Tire selection is getting to be the hard thing w/ 27"
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