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Mavic G40 tire width question

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Mavic G40 tire width question

Old 05-21-23, 09:18 AM
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Mavic G40 tire width question

Is it possible to put some 38ís on these old rims or are 35ís pushing the limit?
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Old 05-21-23, 09:22 AM
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I always figured--perhaps incorrectly--if you can mount the tire and it doesn't blow off the rim once you pump it to pressure, you should be good. That said, I don't think I'd run a 38c on one of these.

There are tables out there that show how large a tire you can mount based on rim width. If you scroll down, you'll find a table from Sheldon Brown website on this:

https://www.sheldonbrown.com/tire-sizing.html

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Old 05-21-23, 10:19 AM
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It's certainly possible to put 38mm tires on them. Whether it's to your satisfaction, only you will be able to answer...
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Old 05-21-23, 11:16 AM
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Another consideration is the quick release and getting the wheels on and off. I have some 35s mounted to 20mm external width rims. With Weinmann QR levers, and QR hangers, it is still a fight getting the wheels off with the Weinmann center pulls. Perhaps side pulls would be different.
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Old 05-21-23, 02:02 PM
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Originally Posted by sd5782
Another consideration is the quick release and getting the wheels on and off. I have some 35s mounted to 20mm external width rims. With Weinmann QR levers, and QR hangers, it is still a fight getting the wheels off with the Weinmann center pulls. Perhaps side pulls would be different.
Centerpulls. What kind? Can't you just pop the straddle cable out? I've been doing that since the dinosaurs ruled.
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Old 05-21-23, 02:23 PM
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I used to race NORBA XC in the mid-'80s with cut-down 700c rims, about the width of your G40. Cut 4 spoke holes worth of rim out of a 36 hole, to make a 26" rim with 32 holes. Bend it to the smaller diameter and re-pin the joint. Then race them with ~50 mm tires. No problem Robert! This was done because XC-racers were weight-weenies, and the available 26" rims back then were heavy.

So, I consider this idea of a maximum size tire for a given rim to be, let's say theoretical. A theory that doesn't hold up in practice.

Nobody who did this ever reported the tire coming off the rim, that I know of. The downside is the tire is not supported well side-to-side at low pressures. The front tire can sort of flop over to the side under tight cornering, unless you keep some minimum pressure in it to prevent that. I don't remember what pressure I ran, but higher than you can run these days with wider rims.

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Old 05-21-23, 03:14 PM
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Originally Posted by 79pmooney
Centerpulls. What kind? Can't you just pop the straddle cable out? I've been doing that since the dinosaurs ruled.
Weinmann 999s. It seems I always have ones with the head somewhat embedded so as to not want to pop out easily. Perhaps if I worked them around a bit they would cooperate more.
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Old 05-21-23, 04:43 PM
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Originally Posted by sd5782
Weinmann 999s. It seems I always have ones with the head somewhat embedded so as to not want to pop out easily. Perhaps if I worked them around a bit they would cooperate more.
I raced for years using narrow MA40 rims with Panaracer 45mm "smoke" tires that measured perhaps 42mm as mounted.

I would fully release the brake cable at the lever and would still have to "work" the tire between the Weinmann C-P caliper's pads to install an inflated tire.

The inside width of the G40 is about 12.8mm versus the MA2 being perhaps 13.2mm as I recall. I ran relatively high pressure, at least 10psi higher than I run on a wider (i22mm) tubeless rim today using the same-sized tire.

Be sure not to use too narrow of a tube in a wide tire, especially when mounted on a narrow rim. There will be extra stretching in the rim cavity as the tube starts to drop down past the sharp bend where the tire sidewall juts out from the vertical rim sidewall! Also be sure to tug on the valve stem as you inflate past 5psi, or the reinforcement surrounding the valve stem attachment to the tube won't even drop into the rim cavity and the tube may then rupture to either side of the reinforcement along the wheel periphery.

You will find the beads to be very tight when installing most tires on the older narrow Mavic rims!!! Must use only the thinnest rim tape is my recollection.

All this brings back the memories, ...the hardships and the fun!

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