Tubular Tires, Wheels and Aerodynamics

[RyanH]

Tires can have a significant influence on the wheel aerodynamics but I can't find a lot of data on what makes for a good combo and how much of a penalty one takes by breaking the 105% rule. The best I can do is infer from tests done on clincher wheels. What I want to know is that if I'd like to have an aero wheelset with 27/28mm tires, which tire and wheel combo should one choose and what's the guesstimated penalty on various wheelsets (e.g., do 35mm wheels take a bigger hit than 60mm deep wheels when the tire pairing isn't ideal?).

Flo has an interesting study on tires:

http://flocycling.blogspot.com/2016/04/ ... study.html

They tested tires between 22mm and 25mm stated sizes. Can anyone provide some input on how much one of these tires bulge past the rim? This would help translate a little to how some of these would interact with a tubular setup.

Questions to answer:
What is a fast tread pattern? Do we know why certain tires are better than others? Who makes a latex 27/28mm tire with a fast tread pattern?
What 28.3mm or wider tubular rims exist today? Which are the lightest?
What's the aero penalty for a 27mm tire on a 27mm rim like the Enve 4.5? What about a 27mm tire on a Bora 50 and Bora 35? (this is going to be a guess at best)
Can we infer anything from what the pros ride in the classics like Paris-Roubaix?

[svendsvin]

Try looking up some of the older zipp 303 data. Show differences with 27mm vs 23mm.

[KarlC]

I thought the below in bold was intresting, taken from the *Tour Aero Bike Test 2019* thread ......

I would agree with Robeambro.

The only things I would add are as follows

-There is a general concensus that fitting a wider wheel rim is faster. This is totally not true, people are fitting wider rims to cope with wider tyres. If you want to go fast, then a narrow rim and narrow tyre combination are always faster. The exception is if you are travelling at modest speeds when the rolling friction of the tyre is more dominant. Additionally if you are fitting shallow rims, you should aim for a narrow tyre otherwise the drag penalty is twofold.

-Ideally you want to aim for a tyre to rim combination that is almost size for size. Having one bigger or smaller than the other generally penalizes you. If permitted, Mavic wheels with the clipin sidestrips and their own tyres are the outright fastest.

Hambini

[KarlC]

Zipp SL Speed tubular is the fasest 27mm tested tire I have seen .........

https://docs.google.com/spreadsheets/d/ ... 2047093726

I put some of them on my Mavic CXR 80 27mm wide wheels that have the clipin sidestrips Hambini spoke of, they ride nice and feel fast but what do I know.

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[Imaking20]

crr != cda

[hambini]

I can't comment on Crr as I don't measure it but aerodynamically, if you take a look at the two mavic wheels in yellow you can see the difference

[kgt]

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.

[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.

I think this is a general trend. US manufacturers use white papers and hard numbers as a form of marketing. European manufacturers are more guarded and don't.

To answer Ryan's question with some drawings. Before I get flamed, I have simplified a 3D problem into 2D! so it's not a perfect analysis.

This is a cut through the centre section of a wheel



Here's a labelled cutout if it's not clear of which bit is which.



Under very slight conditions the air around the rim to bead detaches and attempts to reattach. If you have the Mavic clip in strips this bit does not occur. The critical bit is the alpha angle, if it's too high the airflow will not attach. - the drawing shows it related to the RIM



If you have a bulging tyre, you get an unwanted alpha detachment angle at the tyre. This usually exceeds alpha critical and the airflow detaches.

[wheelsONfire]

Easton Aero 55 tubular is pretty wide. But according to Easton, the still are faster (due to aero) with 22-23mm tires than larger tires.
I just changed tires for 25mm version on mine. Should have used 25mm Veloflex as i used 23mm Veloflex previously.
But i have Maxxis Campione 25mm now. Have only used these twice. Strangely they feel a bit more sluggish!
Perhaps it's just in my head?

[RyanH]

@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.

[AJS914]

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.

[RyanH]

Hambini suggested elsewhere that if you're crafty enough, you can accomplish the same with silicone caulking.

[kgt]

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.

[KarlC]

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.

You dont have to use the Mavic tires you can use any tires you like, but who knows how that will change the rolling resistance.

As I posted above by I am using the Zipp SL Speed 27mm tubular, its the fasest 27mm tubular tested tire I have seen, on my Mavic CXR 80 27mm wide wheels with the Mavic rings in place.

https://docs.google.com/spreadsheets/d/ ... 2047093726

Of course this is just for fun to see if it would work and how it felt, there is know way for me to really know how fast this set up is.

The Mavic CXR 80 are really to big now that I sold my Aero bike, so I should sell them and get some Mavic CXR 60 if I want to keep this set up.

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[KarlC]

Hambini suggested elsewhere that if you're crafty enough, you can accomplish the same with silicone caulking.

It would be ez to do but I would not use silicone as its a very strong glue, I would use a cheep Dap caulk type product that would be ezer to remove.

Eather way it would be a BIG pain to change a tire.

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