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Carbon Wheels Optimized for 28mm tires?

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Carbon Wheels Optimized for 28mm tires?

Old 08-05-22, 11:04 AM
  #26  
Seattle Forrest
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Originally Posted by Camilo View Post
But you don't know what the tire will actually measure on the rim until you mount it, no? OK for a person who can experiment with wheels and tires to get the perfect 105, but seems that a guess, or a calculation based on the marketed tire size is the only practical way to do it.
Even a "perfect" 105% is just a guess. Unless you measure the tires on the wheels, in a wind tunnel or using the Chung method or possibly some other way, it's just a meaningless rule of thumb.

I don't know that I believe them, but Zipp claims their dimples make you faster by shedding vortices as they form such that you fight less turbulent air flow. Clearly the 105% guess is a massive oversimplification of a very complex topic.
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Old 08-05-22, 11:05 AM
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Originally Posted by Sardines View Post
It's actually the opposite from my observations. That's the design of the rim to give the optimized 28mm more aero properties. Same for my 2 different wheels. The final width measurement for mine is what I stated, which means the wider the internal width, the wider the tire casing will measure.The FFWD rim is 31mm ext width wide and 21mm internal width. The poster is not posting the tire casing width measurement.
We're saying the same thing.. I wrote: "Of course, therefore the same 28mm Tire will inflate to smaller width on the wider (external) wheel." The wider external width wheel is the FFWD wheel, but has the smaller inner width.
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Old 08-05-22, 11:11 AM
  #28  
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Originally Posted by Camilo View Post
But you don't know what the tire will actually measure on the rim until you mount it, no? OK for a person who can experiment with wheels and tires to get the perfect 105, but seems that a guess, or a calculation based on the marketed tire size is the only practical way to do it.
More tire manufacturers are adopting the WAM/RAM specs, which tell you what width and radius to expect for a given internal rim width - hopefully it'll become a standard practice.
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Old 08-05-22, 12:26 PM
  #29  
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Originally Posted by Sy Reene View Post
We're saying the same thing.. I wrote: "Of course, therefore the same 28mm Tire will inflate to smaller width on the wider (external) wheel." The wider external width wheel is the FFWD wheel, but has the smaller inner width.
Yes, I see that now but the phrasing is a little unclear because of the missing article to "the same 28mm Tire will inflate to smaller width on the wider (external) wheel".
Depending on "a" or "the", the sentence would mean different things. But I'm perhaps being pedantic! My apologies.
On the note of external widths, I actually messed up! My road wheel, the Enve 4.5 is 32mm external width, not 29mm. The 29mm is my commuter OHR wheels, which is for my Pinion. So I should really shut up about correct other people's mistakes! haha
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Old 08-05-22, 02:28 PM
  #30  
Camilo
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Originally Posted by WhyFi View Post
More tire manufacturers are adopting the WAM/RAM specs, which tell you what width and radius to expect for a given internal rim width - hopefully it'll become a standard practice.
Still a guess. I'm not pooh-poohing the 105 rule or even the concept of "ideal" aerodynamics (although neiher make any difference to me). But it's just a guess, and really, is it more practically effective or meaningful than just putting a tire on a rim and riding?
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Old 08-05-22, 02:45 PM
  #31  
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Originally Posted by Camilo View Post
Still a guess. I'm not pooh-poohing the 105 rule or even the concept of "ideal" aerodynamics (although neiher make any difference to me). But it's just a guess, and really, is it more practically effective or meaningful than just putting a tire on a rim and riding?
Not sure what you mean - you seem to have a couple things going on, here.

If a tire manufacturer has published WAM/RAM for a particular model and size, then no, it's not guess - you should know what to expect when you mount and inflate the tires. Most manufacturers aren't going to publish WAM/RAM for every rim width under the sun, but they should have enough that you can interpolate.

As far as the 105% "rule," yeah, I'm not worrying about it too much, personally. As long as I have a nice transition between tire and rim, I'm happy.
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