28mm tire question
06-21-19, 01:56 PM
#26
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That is why I asked about tubulars. A 25 mm tubular has all the suppleness of a 28 tubeless at less weight, and generally more puncture resistant.
06-21-19, 03:49 PM
#27
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My car wins on all of those over a bike. So they are not my top criteria for component selection when riding. I don't see those as very large reasons to sacrifice ride and weight and durability. I'm not even sure they are less convenient, or take more time. They give me less trouble. For places where lots of flats are inevitable, I would use tubeless or clinchers just to swap tubes.
For places mostly fee of glass or thorns ride the tire till it wears out at higher performance and higher durability than a clincher / tubeless (still a clincher).
You can buy tubulars with heavy butyl tubes, do a pro type glue job (line down the middle, or no new glue) and slap them on and off and pump as easily as any clincher.
There are not as many brands of essentially the same tire, but you get lighter weight, more durability and better ride.
I ride 28mm on the tandem @ 130PSI - they work great. I have not found a clincher equivalent ride and durability within 400g / pair.
For places mostly fee of glass or thorns ride the tire till it wears out at higher performance and higher durability than a clincher / tubeless (still a clincher).
You can buy tubulars with heavy butyl tubes, do a pro type glue job (line down the middle, or no new glue) and slap them on and off and pump as easily as any clincher.
There are not as many brands of essentially the same tire, but you get lighter weight, more durability and better ride.
I ride 28mm on the tandem @ 130PSI - they work great. I have not found a clincher equivalent ride and durability within 400g / pair.
06-21-19, 04:36 PM
#28
don't try this at home.
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I didn't think it was confusing, my apologies.
to make it somewhat clearer, the whole point of my question is/was:
Is the increased comfort increase running 28s significant enough to justify getting a set of wheels build to run them.
To further explain the logic behind asking about a new set of wheels and the reason I think that in my application I would need them...I have not laced on up, nor do I own a set of rims that are designed for 28mm tires, I will assume that a rim designed for a 28 ever so slightly wider than a rim designed for a 25, so when the calipers are adjusted to the rim they will start ever so slightly wider, and this will result in them being opened ever so slightly wider when the cam is released and thus probably clear the inflated 28mm tire when the wheel is removed, as opposed to a caliper adjusted to a wheel designed for a 25 that would start adjusted with a narrower gap for the slightly narrower rim and would have a smaller opening when the cam was released that may not allow a 28mm tire to clear.
As noted elsewhere, my current setup barely clears 25s so I'm confident that I could not get a set of 28s on and off w/o playing with the barrel adjusters, and that's kind of annoying.
to make it somewhat clearer, the whole point of my question is/was:
Is the increased comfort increase running 28s significant enough to justify getting a set of wheels build to run them.
To further explain the logic behind asking about a new set of wheels and the reason I think that in my application I would need them...I have not laced on up, nor do I own a set of rims that are designed for 28mm tires, I will assume that a rim designed for a 28 ever so slightly wider than a rim designed for a 25, so when the calipers are adjusted to the rim they will start ever so slightly wider, and this will result in them being opened ever so slightly wider when the cam is released and thus probably clear the inflated 28mm tire when the wheel is removed, as opposed to a caliper adjusted to a wheel designed for a 25 that would start adjusted with a narrower gap for the slightly narrower rim and would have a smaller opening when the cam was released that may not allow a 28mm tire to clear.
As noted elsewhere, my current setup barely clears 25s so I'm confident that I could not get a set of 28s on and off w/o playing with the barrel adjusters, and that's kind of annoying.
My previous bike barely fit 25mm under the fork. Small bits of gravel or sand stuck to the tire gouged the paint and made a nasty sound too. I'd want at least 3mm, preferably 5mm clearance above the center line of the tire. That bike had maybe 1mm.
You can use hex wrenches to measure the gap between your current tires and the frame. A 4mm wrench is 4mm across the flats, for instance.
Measure the clearance at the sidewalls and on the center of the tread.
Wider rims
I have HED Ardennes+ rims. These measure 25.5mm external width, and 20.5 mm internal width.
Older rims might be 17mm or 15mm internal widths.
On my very wide rims, I've used:
23mm GP4000: actual width is 25mm -- yes, just 2 mm wider than the rim. It worked fine, but 25mm tires are only 15 or 20 grams more, so I don't use these anymore.
25mm GP4000: actual width is 29mm! I can just about remove the wheels without opening the brake release, but I usually flip it up anyway. Easy to remove the wheel.
25mm GP5000: actual width is 28mm.
Chipseal roads
Chipseal, a thin tar layer with gravel embedded, is smoother with larger tires that are flexible. The stiffer "gatorskins" type of tires that are puncture resistant don't flex over the bumpy surface as well.
I haven't tried 28mm. They would likely be close to 32mm actual width.
Air pressure
I inflate my 25 tires as if they are 28mm. The air volume is similar to a "real" 28 on a "normal" rim.
28mm tires have about 30% more air volume. So dropping your normal pressures by 30% is reasonable.
It's related to the area of a circle of that width. (The formula is pi * (diameter/2)^2. So the difference is proportional to the radius squared -- that's a big increase for a small radius increase.)
Last edited by rm -rf; 06-21-19 at 05:06 PM.
