Aero data from 19 wheels by Hambini

[Hexsense]

Not sure about shaping of rim vs disc rim. Maybe brake track no longer need to be vertical or at least flat. It can now have curvature or arc, and also even wider.

But construction sure does different, it now don't need to hold clamping force from brake. See prototype Hunt wheels, 22.5mm internal pair with much wider external profile 36mm.
Normally, on rim brake this will be very heavy as there are a lot of carbon filled to get that wide externally. But Hunt now add bulk with light weight filler instead of structural carbon so it's not that heavy.
https://bikerumor.com/2018/08/16/eb18-w ... -in-color/

[mattr]

^I keep seeing this but is it actually true? If we look at MTB rims (fair do’s no aero) all that’s really happened since discs is they’ve got wider.

wider and shallower. No space at all on the latest rims for any sort of braking surface.
And they are still (roughly) the same weight.

I suspect the road disc rim trend will be the same. More aero (or at least, the advertorials will say they are more aero) and the same weight.

[mpulsiv]

Since the sidewalls will be roughly parallel, almost any tall disc brake rim will also work for rim brakes.

Sure, but when you don't have to build an effective braking surface on the rim of the wheel, it really opens up design possibilities for disc aero wheels! Why think like traditional rim brake designers when the rules are much more open with disc rim construction?

To the best of my knowledge, the only design possibility that unfolded is external rim width. It's unclear whether it's due to an actual design possibility of disc rim or aggressive shift to wider tires. After all, we are seeing 28mm tires on aero bikes.



Roval CL50 rim brake is 29.4mm external width. I don’t see why extra ~2mm is an issue with modern rim caliper. In a given day, disc wheel profile is not making strides over rim wheel profile.

[Ed72]

I think hambini started off by saying at 30 kmh the good wheels where all as good as each other. So this critism was dealt with 35 pages ago.

"I've been trying to get Hambini to post VAR or STDEV for a few posts now, all to no success. We would all indeed do well to remember that the differences between wheels within 5 watts of each other on that chart are basically not differences at all, and the ordering has a pretty high ("pretty high" sucks, but the best one can do without knowing the N and the VAR) chance of being the result of a random chance".

1W to 5W is pretty much the same in terms of wheel performance. the error on the best power meters is 1% but 2% on many and at 200W thats 2W to 4W. So there you go you can even meassure it in the real world under controlled conditions. The wheels have to be ranked and I dont think anywhere hambini has claimed the ranking proves one wheel is so much better than the other at 30 kph. He has highlighted a wheel that has peformed much worse than it should given its depth when the air flow occilates rather than steady state. Thats a bit different.

What type of error?

2% error in accuracy is not important whereas if the meter variance or precision was 2 percent, I would agree. However, most good meters' precision or variation is well under 1%. Five replicates.....don't forget that, too.

The differences are not 5 watts. My FLO60 is 35 watts or 45 watts for the Enve 3.4....the wrong direction if you ride those wheels. The difference is 10 watts between first and third place and 14 watts between first and fifth. These results cannot be sluffed off with "it all falls within the error bars" to me, anyway

https://www.ncbi.nlm.nih.gov/pubmed/28482367

[bm0p700f]

I am looking at the results at 30 kph only. The redults at 50kph are meaningless as I need 500 to 600w to move at that speed solo and I can't do that for long.

For a 32mm wide rim the tyre should sit 30to 31mm wide. That means 23mm internal width is probably too wide for a 28mm as the tyre may be too big

For a 25mm tyre the internal width is likely to be big for the tyre to sit properly.

For normal road tyres 20mm internal is as big as they need to go.

[nachetetm]

I am looking at the results at 30 kph only. The redults at 50kph are meaningless as I need 500 to 600w to move at that speed solo and I can't do that for long.

For a 32mm wide rim the tyre should sit 30to 31mm wide. That means 23mm internal width is probably too wide for a 28mm as the tyre may be too big

For a 25mm tyre the internal width is likely to be big for the tyre to sit properly.

For normal road tyres 20mm internal is as big as they need to go.

This is the main issue I think with modern carbon clinchers. In their attempt to accomplish the 105% rule, they are making very wide rims were the internal size is too wide for the tires that will fit the rule (usually 23c), and if you go for the proper size tire (28c) then they break the 105% rule, loosing some of their benefits. I am still expectant to see what is the outcome of fitting 23c tires in 21mm inner width rims. I have the feeling we will conclude is not optimal for safety and comfort reasons, and we may even see a decrease in inner width, but probably more testing is needed.
I can't stop thinking that "Aero" means TTs and tubular tires. Something not least than 50mm profile, 26.5mm width rim paired to a 25 tubular tire. My conclusion from this very informative topic is that I definitely do not need to worry about it: for my speed and riding there is very little to gain, and such big profile is not of my taste. My other conclusion is that there is a huge amount of products in the market that they don't make any sense, they are just following a fashion.

[bilwit]

I am still expectant to see what is the outcome of fitting 23c tires in 21mm inner width rims. I have the feeling we will conclude is not optimal for safety and comfort reasons, and we may even see a decrease in inner width, but probably more testing is needed.

I think some of the wheels here were 23mm tire on... 23mm internal width

[bm0p700f]

23mm internal widths are for gravel tyres or CX tyres. In fact MTB rims start at that width now.

I am thinking about a rim optimised for the IRC formula Pro 28mm tyres, 19mm internal width and 29.5mm wide. That would also work for 25mm pro ones and 25mm gp4k tyres and other big 25mm. Rim brake bikes can't take much bigger any way.

28mm pro ones on brontrager rims 21mm internal width are 32mm wide. The club mates bike they are on, a lovely madone project one barely has any clearance under the front aero brake.

Maybe I am being too conservative.

[Ed72]

removed.

[hambini]

More wheels are being tested. I will update the original post with results.

[Monkeyfudger]

Can I just come testing in your wind tunnel...I’ll bring biscuits!

[hambini]

Can I just come testing in your wind tunnel...I’ll bring biscuits!

Have you got security clearance?

[Monkeyfudger]

Biscuits, I’ve got biscuits!!

[otoman]

Lol

[ericoschmitt]

Has it been mentioned here or ST forum the bike/fork model used? Couldn't find it.

And if wheels were tested as a set or only the front was swapped? I suppose as a set, but who knows