Determining Maximum Tire Width
08-20-20, 08:37 AM
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Determining Maximum Tire Width
I'm working on a gravel bike build and I'm looking to determine the maximum tire width that I could use with my frame. What are the best ways to determine that using the frame for measurement? The plan is to be using 700c wheels with disc brakes. I tossed on my 700x28 off another bike on the rear and made some measurements. Might not be the most accurate using a tape measure as my calipers have gone and walked off. I feel like side to side I have a good amount of room but my concern is behind the bottom bracket area. Tire photos
08-20-20, 09:32 AM
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35's might work. Riding through mud? Ever have a small rock get stuck in your tire? Seems you have more width than height. A slightly wider rim might help? For me, I would want 5-7 mm at a min clearance.
08-20-20, 10:06 AM
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I think you are right in being concerned with the brake bridge/chainstay brace clearance.
Generally you can measure the distance of where the tire would be & subtract a minimum of 4mm or 5mm for each side & you'd be close enough it would come down to indivifual manufacturer tire sizing & the fitment of the particular tire on the rims you have.
I have one bike I tried Surly Knard 700x41 tires on. They measured 41mm exactly in both width & height with a caliper on the rims I had. The wheel had to be wedged in to the frame. Clearance was some number less than zero. So I tried Panaracer Gravelkings labeled as 700x38 & there is 5mm clearance between the tire & the frame in all directions...fitted to the same rims. That math doesn't follow & the difference is the truth (or absence of) on the manufactures label.
You might buy from a local shop so that you have a physical place to return the tires to should they not fit as hoped.
Generally you can measure the distance of where the tire would be & subtract a minimum of 4mm or 5mm for each side & you'd be close enough it would come down to indivifual manufacturer tire sizing & the fitment of the particular tire on the rims you have.
I have one bike I tried Surly Knard 700x41 tires on. They measured 41mm exactly in both width & height with a caliper on the rims I had. The wheel had to be wedged in to the frame. Clearance was some number less than zero. So I tried Panaracer Gravelkings labeled as 700x38 & there is 5mm clearance between the tire & the frame in all directions...fitted to the same rims. That math doesn't follow & the difference is the truth (or absence of) on the manufactures label.
You might buy from a local shop so that you have a physical place to return the tires to should they not fit as hoped.
08-20-20, 02:36 PM
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Yeah, I guess a 35 could work? Seems like the brake bridge will be the issue spot for clearance. If you dont want to buy from a local shop, then find a 35mm tire on Amazon that has free returns and mount it then return. Measure(with new calipers) what the tire actually expands to and you then have a closer idea to what will work.
If a 35 spins freely, but there is only 1mm or 2mm of clearance, then you know thats too big and you have to size down.
If a 35 spins freely, but there is only 1mm or 2mm of clearance, then you know thats too big and you have to size down.
08-20-20, 09:37 PM
#6
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René Herse sells a "Tire Fit Guage", with which one can test frame clearance for various specific tire widths on 26, 650b/27.5 and 700c wheels. Yes, it's an approximation, because actual tire width also depends on internal rim width.
08-21-20, 06:36 AM
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As others have suggested, it's hard to tell what will fit until you mount it to your rims and stick it on your bike.
The standard is that you want about 6mm of clearance between fork legs, chainstays, and seatstays...Though you can get by with less, if you have confidence that your rims will stay true and you won't be picking up a lot of mud.
Clearance under a brake bridge, down near the bb, and under the fork crown, may be a bit less critical, since the only problem is mud -- the wheel going out-of-true is not such an issue with those bit. But you still need some clearance for mud buildup.
The standard is that you want about 6mm of clearance between fork legs, chainstays, and seatstays...Though you can get by with less, if you have confidence that your rims will stay true and you won't be picking up a lot of mud.
Clearance under a brake bridge, down near the bb, and under the fork crown, may be a bit less critical, since the only problem is mud -- the wheel going out-of-true is not such an issue with those bit. But you still need some clearance for mud buildup.
08-21-20, 01:46 PM
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I used to do this a lot - and here is the biggest problem (making your pictures mostly irrelevant).
I took measurements, and had "plenty of room" But...
the wide point of a 28mm tire and of a 35mm tire is at a much different spot, and that is practically impossible to measure accurately. the wide point of the 35mm tire is pushed up into the narrower part of the frame, so if you have (for example) 40mm clearance at the fat part of a 28mm tire, you may only have 35mm of clearance at the wide part of a 35mm tire. Ooops.
That said, my biggest problem is usually the brake bridge, making height, not width my limiting factor.
this is what I did:
Buy tires from an LBS (or REI, or performance), mount the tires up and try them out. Return if they don't work. I've had 28mm tires measure from 27 to 31mm, so that is a big issue - even within the same brand. Wheel width makes a difference too.
Alternatively - I find there is often more clearance around the front fork than the rear - so I'll buy one tire if I'm not sure. If it doesn't fit, I'll throw it on the front and step down a size for the rear.
I took measurements, and had "plenty of room" But...
the wide point of a 28mm tire and of a 35mm tire is at a much different spot, and that is practically impossible to measure accurately. the wide point of the 35mm tire is pushed up into the narrower part of the frame, so if you have (for example) 40mm clearance at the fat part of a 28mm tire, you may only have 35mm of clearance at the wide part of a 35mm tire. Ooops.
That said, my biggest problem is usually the brake bridge, making height, not width my limiting factor.
this is what I did:
Buy tires from an LBS (or REI, or performance), mount the tires up and try them out. Return if they don't work. I've had 28mm tires measure from 27 to 31mm, so that is a big issue - even within the same brand. Wheel width makes a difference too.
Alternatively - I find there is often more clearance around the front fork than the rear - so I'll buy one tire if I'm not sure. If it doesn't fit, I'll throw it on the front and step down a size for the rear.
