Equivalent tyre widths - tubular and clincher

neeb

There's a lot of talk right now about optimal tyre width, and of course it is usually clinchers/tubeless that is assumed when figures are quoted. But a tubular doesn't have a an internal bead diameter, and also the actual width of tubulars when mounted and inflated tends to be less for the same supposed tyre width, at least when comparing with wider internal diameter clincher rims.

My 25mm Vittoria Corsa G+ tubs glued on Campagnolo Boras and inflated to 100psi actually measure about 24mm wide. My 25mm Continental 4 Seasons clinchers mounted on H Plus Son Archetypes and inflated to the same pressure measure 26.5mm..

Tyre width is supposed to affect 1) contact patch shape at a given pressure and thus rolling resistance 2) minumum pressure at which a tyre can be run without risking pinch flats and thus "comfort" as well as rolling resistance 3) grip, handling etc.

What are the equivalent tyre widths (actual and/or stated) for tubulars and clinchers for each of these factors, and are they different for each?

Sorry, complicated question...

cycleclinic

Clincher nominal width should not be stated. Then again Vittoria tubs don't run true to size either. Conti tubs do though and so do dugasts.

So the answer to your question you have to know the tyre you are fitting to what rim and then you will know how wide and tall it is. The quoted size means nothing and should be ignored.

neeb

OK, let's simplify things by only talking about actual widths - so comparing tubular and clincher tyres that both measure the same when mounted and inflated to the same pressure.

Presumably the tub can be run at a lower pressure without pinch flat risk, so in some respects does that make it equivalent to a wider clincher? But will the contact patch be the same shape for a tubular and a clincher of the same actual width, or will the bead width of the clincher affect that? And how about grip and handling for tubs and clinchers of the same width at the same pressure?

DeVlaeminck

Running low psi is not really relevant to road use though.

milemuncher1

Some people even use a small / thin tub, as a ‘super inner tube’ in a clincher, during winter.

cycleclinic

Tubs will be the proper size at the max pressure which is alot higher than a tubed clincher so the comparsion cant be made.

tub as an inner tube. Some people must like really high rolling resistance. why not just buy a schwalbe marathon plus and be done with it?

imposter2.0

neeb wrote:

OK, let's simplify things by only talking about actual widths - so comparing tubular and clincher tyres that both measure the same when mounted and inflated to the same pressure.

That doesn't really simplify it, because it's not comparable as already pointed out. A tubular is self-contained, so will retain whatever width it was made in. Clincher width can differ significantly, depending on the width of the rim it is being mounted to.

sungod

neeb wrote:

OK, let's simplify things by only talking about actual widths - so comparing tubular and clincher tyres that both measure the same when mounted and inflated to the same pressure.

Presumably the tub can be run at a lower pressure without pinch flat risk, so in some respects does that make it equivalent to a wider clincher? But will the contact patch be the same shape for a tubular and a clincher of the same actual width, or will the bead width of the clincher affect that? And how about grip and handling for tubs and clinchers of the same width at the same pressure?

i've never had a pinch flat with tubs, even when catching 'surprise' potholes, in about ten years i've had two with clinchers in similar situations (this is with veloflex tubs which have latex tubes vs. gp4000s with butyl tubes)

assuming slick road tyres of similar mounted profile/width...

at the same pressure the contact patch will be about the same - there may be some slight variation with tyre design, i.e. varying thickness - many tubs have the tread stuck onto the carcass with rubber only extending a few mm beyond the contact area, whereas most clinchers seem to have rubber pretty much bead to bead

grip depends on the tyre compound

handling isn't different at normal pressure, but it's very different at low/no pressure, with a bit of care tubs remain rideable even when flat, whereas flat clinchers go all over the place and can come off the rim

when there is a puncture, i find clinchers tend to deflate much more suddenly than tubs

on aero rims the 'correct' width tub is generally the one matching the rim width, a 'lightbulb' profile caused by too wide a tyre messes up the performance - based on routes i ride a lot, coasting downhill is consistently faster with a narrow tub matching rim width than one which bulges out 2mm each side, handling in strong crosswinds/shifting yaw angle is also better with matched width

neeb

Imposter wrote:

neeb wrote:

OK, let's simplify things by only talking about actual widths - so comparing tubular and clincher tyres that both measure the same when mounted and inflated to the same pressure.

That doesn't really simplify it, because it's not comparable as already pointed out. A tubular is self-contained, so will retain whatever width it was made in. Clincher width can differ significantly, depending on the width of the rim it is being mounted to.

Yes, I know. But a given clincher mounted on a given rim will have a measurable actual width. So let's say that you have two wheels, one a clincher and the other a tub, both fitted with tyres that are the same actual width when mounted. Will these be comparable, or would some width-related properties of the tyre vary between the two wheels?

I suppose there still remains the complication that two clincher rims with the same actual width of tyre when mounted could have different properties - a "narrower" tyre mounted on a wider rim could be the same actual width as a "wider" tyre mounted on a narrower rim. But you could compare both extremes - a 25mm (actual width) tub with a 25mm (actual width) narrow clincher rim setup as well as with a 25mm (actual width) wide clincher rim setup.

neeb

sungod wrote:

i've never had a pinch flat with tubs, even when catching 'surprise' potholes, in about ten years i've had two with clinchers in similar situations (this is with veloflex tubs which have latex tubes vs. gp4000s with butyl tubes)

I've had a couple actually, but in both cases it was with Schwalbe tubs with butyl inners. Now riding Vittoria with latex inners..

neeb

sungod wrote:

on aero rims the 'correct' width tub is generally the one matching the rim width, a 'lightbulb' profile caused by too wide a tyre messes up the performance - based on routes i ride a lot, coasting downhill is consistently faster with a narrow tub matching rim width than one which bulges out 2mm each side, handling in strong crosswinds/shifting yaw angle is also better with matched width

This was one thing I had in mind when posting initially. Let's say you buy into the current belief that running tyres of the same actual width at lower pressures decreases rolling resistance because the tyre is conforming more to the road surface rather than bouncing around. If that's your reason for runnng wder tyres (to allow lower pressures without pinch flat risk), then you could run a tubular at a lower pressure than a clincher, so effectively achieve the same rolling resistance with a narrower (actual width) tyre. This would in turn be more aero, and/or equally aero on a narrower and lighter rim.

DeVlaeminck

neeb wrote:

sungod wrote:

on aero rims the 'correct' width tub is generally the one matching the rim width, a 'lightbulb' profile caused by too wide a tyre messes up the performance - based on routes i ride a lot, coasting downhill is consistently faster with a narrow tub matching rim width than one which bulges out 2mm each side, handling in strong crosswinds/shifting yaw angle is also better with matched width

This was one thing I had in mind when posting initially. Let's say you buy into the current belief that running tyres of the same actual width at lower pressures decreases rolling resistance because the tyre is conforming more to the road surface rather than bouncing around. If that's your reason for runnng wder tyres (to allow lower pressures without pinch flat risk), then you could run a tubular at a lower pressure than a clincher, so effectively achieve the same rolling resistance with a narrower (actual width) tyre. This would in turn be more aero, and/or equally aero on a narrower and lighter rim.

But how low would you be running them. You can run a clincher at lower pressure than is usual just not as low as you can run a tub. In cyclocross it's relevant but I doubt it is on the road. Also while clinchers may be more prone to pinch flats tubulars are far more faff and expense when they do flat and while they may be less likely to pinch flat it does happen and will still happen more at low pressures.