Tire size and aero rims: how almost every clincher user defeats the purpose of aero rims

[WinterRider]

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I'm sorry, English is not my 1st language and I sometimes have a hard time followig your posts?

I do understand and my writing style adds to confusion given that barrier. Off to get some mileage in and will revisit my reply very soon.

[WinterRider]

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I'm sorry, English is not my 1st language and I sometimes have a hard time following your posts?

'Agreed ...mostly. Simple way to measure frame vibration.. goober on electronics I am. Thought something to measure shocks at seat post.. that makes most sense to me.. where most of the wt is set into the frame. Simple cost effective method?'

Ok.. what I meant was finding a simple device to mount or place in the region where the seatpost meets the frame. Seems to me that is where the most shock is transmitted into the frame per me.. as I ride a flat bar bike always.. no drops for me. I have read some phone apps have a program that can measure this (?), yet I carry a simple phone for bike rides. By cost effective I mean a device which is not pricey... and simple enough to operate.

I ride is about the same position as most everyone who is positioned with their hands on the bar where is goes lateral.. vs into the drops. I do sacrifice aero ability not running drops yet I can lean down if I desire to get lower and catch/buck less wind. I'm a fitness rider and getting all the speed and faster times down is not paramount to me. Yet I do enjoy tinkering with a bike to get down to a practical riding weight. For me that is mostly in the wheelset (always alloy) and tire weight vs performance.

[Hexsense]

So when some manufacturers are claiming you should be running wider tire with their now wider new aero rims to gain benefits in handling and comfort (which is true), they did not forsee this aero drawbacks or haven't done enough research? Brands like Campagnolo actually claims it's more aero to run wide tire with wide rim (no evidence, studies, or any figures to back up the claim).

This is actually something to think about.
Isn't Campagnolo rim profile is a bit of V shape than U shape tested in the article?
What if Campagnolo design the air flow so that the tire being wide send the wind smoothly down the V shape taper down gradually rather than what U-shape rims like Zipp imply that rim will be the widest point and any tire wider than their U-shape widest point screw their design?
Is that possible that wide U bend on the U-shape rim was replaced by natural wide U bend on the tire in Campagnolo's computed air flow?

[Kurets]

What I think is that manufacturers are answering to the trend of wide tyres by adopting their rims to a wider profile. They likely not considered the profile every 25mm (marked) tyre on their clincher rims. If the rim is 27mm wide at its widest point, then you should aim for a 25-26mm (measured) width tyre. A GP4000 will not measure of to that if the inner width is 19+ mm. Most likely a wide 23mm tyre or narrow 25mm tyre will give a better profile. Its all about keeping the surface of the rim+tyre as smooth as possible, if the tyre is wider, a low pressure zone will develop behind the tyre causing a higher Cd plus the area part of CdA increases too!

[Marin]

Exactly, people are buying tires labeled "28" for their "28 wide" rims. Tires come out to 32mm (GP4000s on 20c rim).

Even a "25" GP4000s will be too wide, you'd have to run a real 25 or a "23" Conti.

[Beaver]

You can find everything here: https://silca.cc/blogs/journal

For optimal aerodynamics, the tire should be up to 10% slimmer than the brake track. But honestly, if they are the same width it's already the biggest step forward.

So e.g. 23mm tire on 19C with 27mm wide rim at the brake track, 25mm tire on 21C on at least 28mm at brake track (more is not availiable at the moment).

If your average speed is above 35km/h stick with 23mm tires, all others are fine with 25mm.