Rim size

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Ed2868

Member
Location
Chelmsford
I badly damaged the rim in rear wheel hitting a pothole, wheels are 700c 23mm on a trek madone 2.1. I have found a pair of unused 700c 25mm for sale at a very reasonable price! Is there any reason not to buy these? What adjustments will I need to make? Brakes etc? Advice please!
 
Location
Loch side.
It is highly unlikely that the new rim will be exactly the same size as the old one, even though the rims' tyre sizes are the same.
For wheelbuilding purposes, rim sizing is the diameter between opposing spoke holes from a position inside the rim where the nipple will seat. This varies with rim profile. To use an extreme example, a deep section ZIPP rim will be visibly smaller than a Mavic Open PRO, even though the two use the same tyre.
Differences as small as 1mm could render the new rims useless since your current spokes will be either too long or too short.
If you buy the new rims and the size is wrong, you will have to buy new spokes as well. Then the job becomes a wheel build rather than just a rim transplant.
 
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Ed2868

Ed2868

Member
Location
Chelmsford
Sorry I didn't make myself clear. These are an entire wheel set. I currently have 23 700c and is there a problem replacing with 25 700c? And are there advantages or disadvantages of wider rims?
 
I badly damaged the rim in rear wheel hitting a pothole, wheels are 700c 23mm on a trek madone 2.1. I have found a pair of unused 700c 25mm for sale at a very reasonable price! Is there any reason not to buy these? What adjustments will I need to make? Brakes etc? Advice please!
your tyres not your rims are 23x700c.
your new rims may or may not be the same width but if they are more or less the same width, given that rims take a range of tyre sizes you should not have an issue changing from 23c tyres to 25c tyres if you want to. You won't need to adjust the brakes if the new rims are the same width at the braking surface, tyres don't affect this choice. However, unless you replace with identical rims, you may well have to adjust the brakes.

Given that you have damaged the rear rim, you will need to ensure that your new wheelset takes your cassette. So if you are on a shimano freehub, then you will have to stick with shimano, don't buy campagnole.. (spelling?). Also if you have an 11 speed cassette you will need to make sure that your new wheelset is 11 speed compatible. If you are on a 10 speed you will have less of a problem, but if you purchase an 11 speed compatible wheelset you will need a spacer to ensure that your 10 speed cassette fits properly. You may find that this also affects your rear derailleur indexing.
 
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