Tubular Tires, Wheels and Aerodynamics

[hambini]

@hambini, any chance you can bring a tubular wheelset into your next batch of wheels?

It's interesting because most tubulars these days have a blunt/rounded edge where the tire meets the brake track, which would probably indicate definite detachment, right? Older tubular wheels like Mavic CCU and Lightweights had a very sharp rim edge that almost blended into the tire sidewall when paired with a 23mm tubular.

The attached image on the right shows the "rounded" rim lip that I mentioned.

I have done, it's the yellow bar. Mavic CXR80 Tub.

[RyanH]

Awesome, thanks. Do you know what tires were used? Mavic aero rim strip?

[Calnago]

RyanH: I'm sure you know this but a tubular will never interface with the rim edge the way a clincher does, as it's fully encased in a round casing and it will always want to be "round". Whereas a clincher will always want to push it's beads flat against the wall of the clincher rim. Thus, if we're talking about the aero properties at that particular junction, then the clincher wins. The only way a tubular could possibly emulate that is if the rim bed was the same radius as the tire and basically wrapped the tire from it's base almost to it's mid section (and overall diameter) then the "exposed" portion of the tubular (about half of it) would be free to just form a half moon out in front of the two walls of the rim. Of course, that would negate the handling characteristics of the tubular so the excercise would be largely pointless and you should just run a clincher. The choice is really between miniscule aero gains or large gains in ride quality and handling.
As an aside, I did set up some of those Mavic wheels with the rim strip. Sure, it closes that gap, but boy.... I'd like to see the crud and dirt that gets trapped in there after a while of riding.

[hambini]

Awesome, thanks. Do you know what tires were used? Mavic aero rim strip?

I'll have to check on tyres

Plastic rim strips were included.

[KarlC]

RyanH: I'm sure you know this but a tubular will never interface with the rim edge the way a clincher does, as it's fully encased in a round casing and it will always want to be "round". Whereas a clincher will always want to push it's beads flat against the wall of the clincher rim. Thus, if we're talking about the aero properties at that particular junction, then the clincher wins. The only way a tubular could possibly emulate that is if the rim bed was the same radius as the tire and basically wrapped the tire from it's base almost to it's mid section (and overall diameter) then the "exposed" portion of the tubular (about half of it) would be free to just form a half moon out in front of the two walls of the rim. Of course, that would negate the handling characteristics of the tubular so the excercise would be largely pointless and you should just run a clincher. The choice is really between miniscule aero gains or large gains in ride quality and handling.
As an aside, I did set up some of those Mavic wheels with the rim strip. Sure, it closes that gap, but boy.... I'd like to see the crud and dirt that gets trapped in there after a while of riding.

I have never had an issue with crud or dirt getting in there, its a tight fit that hard to remove even when you want to. As a side point I live in San Diego Ca so we dont get much crud from bad weather here.

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[KarlC]

hambini its sure nice to have your unput, if you dont mind me asking what wheels are you using now and what are you planing to buy next ?

Thx Karl

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[Calnago]

...
I have never had an issue with crud or dirt getting in there, its a tight fit that hard to remove even when you want to. As a side point I live in San Diego Ca so we dont get much crud from bad weather here.

Well that’s good. The owner doesn’t ride them in cruddy conditions either, but whenever I build or put together anything I can’t help myself from asking those types of questions, especially here in the rainy Northwest where that rim/tire crevice can get pretty caked up with road grime as it mixes with water.

[hambini]

hambini its sure nice to have your unput, if you dont mind me asking what wheels are you using now and what are you planing to buy next ?

Thx Karl

.

I use Dura Ace C60's. with Continental GP4000S2 tyres

A bit of background but I don't actually like riding my bike, I'm more of a runner. I simply use it as a means of commuting from A to B. The bike is a Cervelo S5 and I use it in all weathers and lots of people comment on youtube that it needs a clean. It really does get thrashed.

My philosophy is the watt difference is not worth it if you are sitting by the side of the road in the pouring rain so I buy durable wheels. My 220W FTP or thereabouts is not going to win any races so I don't really have the need for a watt saving.

If I wanted to buy a new set for my current use. I'd get another set of Shimano wheels. I've had 3 sets and all have been pretty much bullet proof.

If I wanted Aero wheels then I'd get the Mavic cosmic carbone. but the narrower type. It has the performance of a 60mm wheel but less deep so it's not so bad in crosswinds. You just have to make sure you get the right tyre otherwise it will mess up the aerodynamics quite dramatically.

Hope that helps

Hambini

[hambini]

It is interesting that Mavic's technology actually works but nobody considers their wheels competitive in terms of aero (at least in our forum). If Mavic were a US brand they would have already published a few 'scientific' white papers that everyone would discuss.

The Mavic system isn't perfect. You have to use their tires which are not the fastest tires in rolling resistance tests and their strips are UCI illegal. Maybe you don't care abou the UCI but the slower tire negates the aero gain so there isn't any overall benefit.

The focus of my post is elsewhere.

I think KGT meant the aero benefit is one aspect. Picking the correct tyre is another. Unless you are going at very low speeds. By my rough guess, I would say the aero benefit would outweigh the rolling resistance.

Mavic don't generally publish white papers, whereas companies like Bontrager, HED and others do.

Just looking at that list, it's predominantly American companies.

[Mep]

Has anyone seen research indicating that the aero effect from tires outweigh their rolling resistance? It's interesting that the aerodynamic profile of the tire/rim interface has come under more scrutiny lately both here and elsewhere (see road.cc), which kinda makes sense considering how much research has already gone into reducing crr. Roughly speaking I guess you could expect to see a rolling resistance of around 5W difference between a top end clincher vs. tubular tire (e.g. Conti GP4000s II vs. Competition). But it somewhat surprises me that the aerodynamic penalty from using the "wrong tire" would cost more than 5W. I'm defining "wrong" in this case to mean a tire that measures around 1/1.05 of the rim it's mated to, but has the "wrong" tread pattern and the "wrong" aerodynamic profile with the rim.

We all know about the 105% rule and that's there's an aerodynamic penalty from running too-wide tires. But dissecting the problem one level deeper, is the tire's tread pattern and how it interfaces with the rim actually important?

In the OP's original question, choosing to run 27/28mm tires then could be a real double whammy. I've been running tubular tires for a long time and have come to terms with the fact that I will run into more rolling resistance with the benefit of lighter weight and ride quality. But if there's actually an aerodynamic penalty that's greater than the rolling resistance one, we could be looking at some significant watts from a tire choice.

[sungod]

I've been running tubular tires for a long time and have come to terms with the fact that I will run into more rolling resistance with the benefit of lighter weight and ride quality.

why?

simply because it's become fashionable for people to parrot that clinchers have lower crr than tubs does not mean any given clincher has better (or worse) crr than any given tub

if you use the bicycle rolling resistance website data as a reference, the two lowest crr results are clinchers running tubeless, then it's a tub, if the clinchers were run with a normal inner tube i believe the tub would have lowest crr

data (for running tubeless) from brr site...

Vittoria Corsa Speed (open TLR) 7.7 W
Continental Grand Prix 5000 TL 8.3 W
Vittoria Corsa Speed (tubular) 9.1 W

note: these 'wattages' need understanding in the context of brr's methodology as explained on their site, safest is to regard them as relative values, not real world figures

looking deeper, the conti is 27mm wide and quoted loss is at 120psi, the tub is 23mm wise, same pressure

you might run a 23mm tub at 120psi, will you really run a 27mm clincher at that pressure? at 100psi the clincher loses 8.9w, at 80psi it's 9.9w, oh dear, and that's still without an inner tube, so which is 'faster' in the real world?

the brr methodology may or may not translate to equivalent results on the road, but taking the headline numbers to say x is 'better' than y clearly is unsafe

reality is that there are many variables and trying to test them all would be uneconomic - for instance do the results stand irrespective of rim width? road surface? temperature? pressure? rider weight? what about non-linear effects?

at road speeds, i'd think the crr losses have the potential to be dwarfed by aerodynamic impact of tyre/rim matching, especially on the front

[bm0p700f]

It a shame there is no further development of tubulars.

A tubeless tubular should be possible. Take a tubeless clincher and simply join and seal with rubber. Team up with a wheel manufacturer and creat a wheel optimised to that tyre. All the benefits of tubular rims with a modern tyre. Also it a tub than can be plugged if you get a flat.

Oh if you use a sensible amount of sealant the difference between the competition tub and the gp5000tl drops drops to 3W or so at 120 psi but you won't run them that high. Real world the rolling resistance will probably be the same or close.

The 25mm conti gp 5000tl mounted to a 20mm internal width rim at 80 psi are 26mm wide.

[Calnago]

It a shame there is no further development of tubulars.

A tubeless tubular should be possible.

What do you mean there’s no further development. The profile (round) is pretty perfect as it is, for consistent handling purposes. I do not want an egg shaped tire profile, and a square... well let’s not go there. Rubber compounds used in tubulars are the best of the best (I’m only talking good stuff here). Look at the Specialized Turbo Cottons, they’re supposed to be very very nice and I have some on the way, albeit in clinchers, to try out. What else needs improving upon? They are far safer than either a regular clincher or a tubeless clincher. And as for ride quality, there is still no comparison. Perhaps we should hope for more development in tubeless clinchers, since that’s where all the faffing about seems to be occurring. And as for whether a tubeless tubular is “possible”, not only is it possible, they’ve been around for years. It’s just that they ride like crap and have all the downsides of both a clincher and a tubular wrapped up into one. Remember the tufo “tubular clincher”. Now there’s a good example of the worst of all worlds. But for a straight up tubeless tubular, I’m about to take a spin on a set right now.

The brand was licensed by Donnelly Cycling, but they are no longer using the Clement name, so while you won’t see the Clement label you can still get it under the Donnelly label as Strada LGG.

[RyanH]

@mep

Check the link I put in my OP. In part 2 they added the aero drag to the crr penalty to come up with a total system cost.

Unless Hambini suggests otherwise, it seems there is a concensus that tread pattern matters. Conti Gp4k seem to be the optimal tread pattern.

Maybe I'm misinterpreting, but I think Hambini's test suggest that the rule of 105% might not be an actual rule. On many of the wheels in his chart, the 23mm Conti GP4K (they're possibly 25mm/26mm actual width at the tested 119 psi) measures wider than the rim yet they still perform well. In one of his comments, he suggested to not get bogged down by a millimeter here or there on tire size.

[AJS914]

One takeaway from his tests that the wider tire on a narrower rim (22.4mm wide C60 in this case) can be a large penalty. On the wider Enve rim there isn't much penalty at all.