Xiamen Carbon Speed 10 years anniversary special promotion

[KaiDeus]

I forgot I'm in a cercle jerk. I'm just pointing out a difference in the rims from advertised measurments. I thought more information is always better. In the end you can take any learning from it that you want.

As you read in my post I'm very pleased with the overall quality. Following the 105 rule is obviously rather anal, but the original rim profile is designed to follow it, why wouldn't you want to know that it measures a bit differently.

I ride a lot in crosswinds so a good performance at yaw angles larger than 0 is a feature I want in a wheelset.

Would I be not satisfied with the wheels, I would have send them back, but I didn't.

[ancientone]

Got my D50CU-28 T1100 in the Mail. Wheels look great, packaging is very good and overall quality seems to match expectations.

One caveat are the actual rim measurments. Actual measurments are 22mm internal and 29mm external instead of 21.4mm internal, 29,2mm external.
With the wider internal and narrower external width a 28mm gp5000 s tr measures 29mm and sits flush with the rim profile, so no rule of 105% to achieve here, if your don't want to have a 25mm tyre, which most of us certainly will not want. So in some way the rim profile is neither here nor there, neither fit for narrow nor really fit for wide tyres. I will get on with it, but this difference to the advertised measurments is the worst difference you can have in a rim profile. Both rims measure the same btw, so i don't think this is a unit variation problem.

Measurements done with a digital caliper and at multiple locations.

I don't think it's going to make much of a difference but it's always good to know and feedback. :-) I think it's sort of expected if you buy parts from China although I think Peter held himself to a different standard.

I order a 52mm headset bearing once and the seller send me a 51mm, and claim that it was variance due to manufacturing... that was a WTF moment since all the bearings I had bought previously was precise to 0.1mm.

Anyway, looking forward to the rims from Peter. Still thinking about the Frameset though...

[toxin]

As you read in my post I'm very pleased with the overall quality. Following the 105 rule is obviously rather anal, but the original rim profile is designed to follow it, why wouldn't you want to know that it measures a bit differently.

Rule of 105 is horseshit, it's the closest to useful at 0 yaw and even then it's not accurate. As soon as you start adding any yaw, it breaks down completely

[wintermute]

Rule of 105 is horseshit, it's the closest to useful at 0 yaw and even then it's not accurate. As soon as you start adding any yaw, it breaks down completely

Saying it breaks down completely is even more facetious than saying if don't abide to the 0.1mil you may as well run box sections.

So you think brr drum tests are meaningless because 'nOt ReEl LiFe'. 

[Icyseanfitz]

Just measured my dc50u wheels which should have an internal width of 21.4, pretty much spot on at 21.5 and that could just be a fault in my calipers

[toxin]

Saying it breaks down completely is even more facetious than saying if don't abide to the 0.1mil you may as well run box sections.

So you think brr drum tests are meaningless because 'nOt ReEl LiFe'. 

Im saying this because I've run cfd simulations on various rim shapes with various tyre sizes. 105 just has no meaning

[Sakizashi]

I think its a good idea to verify dimensions. There seem to be a pretty wide tolerance on rims and tires that I have seen. This is on the higher side of the small sample size I have measured, but not insane. Lets also remember that your calipers are not perfect either.

Regarding 105--this "rule" was christened in an era of different wheel shapes, narrower tires, and rim brakes. It's also often misused in forums in reverse of what it was intended for. It was to help you select the best tires for a given wheel, not the other way round. Its been abused and misused and isn't relevant anymore.

Rim profiles matter. The fastest U-shaped profiles for a front wheel can be a watt or more faster, particularly at shallow yaws, but the air detaches so much sooner that they aren't used as much anymore. I think the Hunt Sub50 paper documents this pretty well when they cover all the rim shapes they tested. If I remember correctly and did the math right at 48kph the fastest profile suffered detachment a few degrees earlier, but was like 1.5w faster. Is it worth it to optimize at that level? I guess it depends on you, but following the rule of 105 on a rim that's not the right shape for that rule to apply wont get you very far.

[Lotnik]

And new combo wheelset 20/20H carbon spokes hubs built with  D50CU-33 T1100 rims UD paintless was just released, around 1180+/-20g/pair

How does lacing pattern looks like on that wheels? Front and rear?

[Nkearb]

Im saying this because I've run cfd simulations on various rim shapes with various tyre sizes. 105 just has no meaning

That great that you disproved a BS 25yo wind tunnel test with an even more BS CFD analysis.


I actually skip wind tunnel testing and CFD analysis, I acquire a rim profile in a .jpg file format and scanning with my eyes I am able to calculate the aero performance of a particular tire-rim transition with a 100% margin of error