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Newbie Tire help please?

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Newbie Tire help please?

Old 05-22-20, 06:18 AM
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Newbie Tire help please?

Hi everyone,

I'm new to the world of cycling but loving it so far!

I bought a city bike that came with the not-so-normal tire size of 650c x 25c. If I had known this is such an abnormal size, I may have reconsidered. But here I am.

I'd like to try changing the tires the bike came with. I came across the Continental Grand Prix 5000 and would love to give them a try.

The issue is - some retailers list the tires they have in stock as 650x25, 650x25b, and then some list as 650x25c but also list them as b's in the same description.

Q1) Continental only lists these tires as available in 'b' ...so am I correct in assuming they only made/make them in this size? Or did they make the Cs but stop at some point?

Q2) I'm otherwise looking at the Grand Prix 4000s II, which do come in at 650x23c. Am I correct in assuming the 23c will fit/work on my existing 25c?

Q3) if I'm able to go down to 23c on the GP 4000s II, will I notice any difference in comfort and/or performance?

Q4) any other recommendations on tires in this size?

thanks and looking forward to learning more!
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Old 05-22-20, 06:39 AM
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650C rims will only accept 650C tires. When in doubt, look for the ETRTO-standardized designation on the tire sidewall. It should look something like this: 25-571. The first number is the nominal tire width in millimeters, and isn't terribly important for fitting the tire to the rim, as rims can accept a range of widths. Just be careful not to go too wide if your frame/fork has tight clearance. The second number is the "bead seat diameter" (BSD) in millimeters, and must match that of the rim in order for the tire to seat on the rim.

650A = 590mm BSD
650B = 584mm BSD
650C = 571mm BSD


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Old 05-22-20, 05:17 PM
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What you have is probably either a time trial bike or a road bike built for someone small. Most of the 650C tires you will find will be 23mm. A few will come in 25mm, and a VERY few will come in 28mm. There is nothing wider in that size. Like JDT says, the rims of the various flavors of 650 are all different diameters and are not cross-compatible with anything else. You can usually change your wheels to 26" (ISO 559) because all that's required is to move your brake pads 6mm. Tires for 26" start at 1" (25mm) and go up from there. Your frame probably can't take much wider tires anyway, though - 25mm might be your limit.
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Old 05-22-20, 05:21 PM
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" I bought a city bike that came with the not-so-normal tire size of 650c x 25c"
A city bike with that tire size would be a very unusual beast. Exactly what bike is it? Knowing what you have will make it possible for people here to make useful suggestions
Make and model please
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