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Tire Clearance? How to measure

Old 08-19-09, 09:02 AM
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Drwecki
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Tire Clearance? How to measure

Running 700c by 23 wheels. There is more than 1 inch clearance to the top of the fork and 1/2 + a littleeach on each side of the tire to the fork/brake (the brakes are old mafacs and extend further than the fork in the more space direction). I want to run a huge tire and throw on a oring8 space bar (just so you know the effect I'm going for...bomb proof bike zilla). It's on old Raleigh Grand prix (74 if I read the serial number correctly). How do I tell what my rough tire clearance is? I would like these but think that may be a bit of a stretch even though I think I have the clearance...

http://www.benscycle.net/index.php?m...3&currency=USD
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Old 08-19-09, 10:08 AM
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bump? Nobody? How do you measure tire clearance? I thought that you measured the distance from current tire (700c x 23) to the bottom part of the fork crown (1 inch) and the sides a little more than 1/2 inch. But from there I don't know how to figure out what size will fit 700c by 35 is likely, but what about 37 and 40? Help a maroon ON my KNEES pleading here
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Old 08-19-09, 10:12 AM
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Why not simply buy the 37 or 40 tires at your LBS, and mention your situation before swiping your card? They'll almost certainly allow an exchange if the first tire you try doesn't fit.
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Old 08-19-09, 11:19 AM
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Mainly price and selection concerns. I can get whatever I want on the internet and usually cheaper too!
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Old 08-19-09, 11:51 AM
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My first concern would be what the save tire size limit is for the width of the rim.

Tire sizes are not very accurate and vary from brand to brand. My 23 mm Michelin tires are about the same size as a Continental 25.

Here is what I think but can't confirm. The cross-section of a tire is suppose to be the maximum interior cross-section with the tire fully inflated to operating pressure, not necessarily the width. At least I've seen diagrams explaining it that way.
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Old 08-19-09, 12:36 PM
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Originally Posted by Drwecki View Post
Mainly price and selection concerns. I can get whatever I want on the internet and usually cheaper too!
Because of the claimed-vs.-actual dimensions issue, it's probably better to buy your first tire from a LBS. You can buy just one and try it on both front & rear wheels.

After you've confirmed the maximum size that will fit, you can save all of the nickels & dimes you like on future tire sets without risking the return freight, (or being stuck with an unusable tire from an online seller who doesn't allows returns/exchanges.)
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Old 08-19-09, 02:56 PM
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40 mm tires should be about 3/8" bigger in each direction. Also look how much space you have between the side of the tire and the chainstay, and to the chain in bottom bear.
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Old 08-19-09, 02:57 PM
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Originally Posted by Al1943 View Post
My first concern would be what the save tire size limit is for the width of the rim.
I've checked Sheldon's website http://www.sheldonbrown.com/tire-sizing.html and my rim is 18mm which pushes the upper limit to about 40mm.

I will probably just go down to the LBS, they are helpful, I just hope they have a good selection. I don't not like LBSs, I just really like the internet..
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Old 08-19-09, 03:01 PM
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Originally Posted by AndrewP View Post
40 mm tires should be about 3/8" bigger in each direction. Also look how much space you have between the side of the tire and the chainstay, and to the chain in bottom bear.
3/8 bigger than 23s or 3/8ths bigger than my original measurement of 1/2 (4/8). Did you do a mathematical calculation or are you working from experience (either is ok, I just want to know the equation so I can solve similar problems in the future).

In the back I have so much room it's not even funny. No brake, wide chainstays.. I'll give it a measure though...It just looks like I can fit one of those motorcycle tires back there...
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