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New Tire Size?

Old 08-29-21, 02:44 PM
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New Tire Size?

Been I long time since I've posted here, but after several thousand more miles my trusty old Giant TCR C2 is once again in need of new tires. The old tires are Continental GS-4000 in 23mm (same size as all prior sets). Any reason to think there would be a problem with clearance if I move to 25mm? The brake calipers are Shimano 105's.

Thanks.
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Old 08-29-21, 03:15 PM
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Sure there's every reason to check out whether there's clearance for wider (and thus taller) tires, especially if you are not buying from a LBS. Because the return of "found to be too big to fit" tires is a pain and costs some more $. The best way is to test fit before buying... The usual is to measure how much clearance there is with the old tires 9and what's their measured width), then get the next larger size and see what happens. Many consider about 4mm of open clearance between the tire and the sides of the blades.stays to be a minimum. Many don't consider the added height though. Here road stuff that gets picked up on the tire will increase the effective tire height.

My current weekend club bike has only a few mms of height clearance under the calipers and I feel/hear pebbles and such raking their way through that tight gap.

Really this question is one of those that is best answered by test fitting. Andy
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Old 08-29-21, 04:54 PM
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Why should I have to look up what fits your bike? It's right there near you isn't it? Go look at how much clearance your 23 mm tires have to all parts of your bike. Find the narrowest clearance and that is how much bigger you can go.

What you have to decide on is how much clearance you want for safety. Mud sticking to the tire might slow you to a quick stop. Or a stick getting kicked up in that narrow clearance part might ruin your day.

23 to 25 mm is 2 mm more height on your tire and 2 mm more width. But you have to allow for differences between manufacturers. External tire dimensions aren't set in stone by any governing authority.
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Old 08-29-21, 09:12 PM
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Best to measure but when I had a TCR from the mid 2000s, it can fit 28mm tires.
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Old 08-29-21, 10:26 PM
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If you are referring to Continental GP4000, they have been replaced by GP5000. The only reason I mention that is that Continental has reduced the measured size of the GP5000 compared to the older GP4000 to reflect the size when mounted on modern wider rims.

Rim width does effect actual inflated tire dimensions so it isnít as cut and dry. Times have changed from the old 14mm internal width road rims.

If you go to rollingresistance.com you can get measured sizes.

John
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Old 08-30-21, 01:51 AM
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They'll fit. I personally am one of the few 23mm holdouts. 2mm difference is almost nothing and I run the same air pressure anyway so I have no need to add any rotating weight.

However, some tires run small and in that case I would go up a size.
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Old 08-30-21, 06:37 AM
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The actual width and height of tires vary dependent on rim and manufacturer. You can get some idea from https://www.bicyclerollingresistance.com if your tire of interest is listed. However, there is no substitute for actually mounting the tire.
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Old 08-30-21, 02:50 PM
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I had one of those. The gap to the seat tube was pretty tight, as I remember. I always ran 23s because I didn't know better. But 25s should fit.
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