27mm or 25mm rim width, which is better?

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dannyboybad
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by dannyboybad

Hey....

Ive been looking to get a deeper section wheel set for racing from China... and I see a few new options they are pushing this year.
U shaped section and a wider rim... I see zipp 808's are 28mm wide now.

So what is better (faster)... 25mm or 27mm. See below latest offerings.

Thank you in advance for any advice.

https://www.aliexpress.com/item/ORGE-Ud ... 4f4c651aad

https://www.aliexpress.com/item/1730g-U ... 0.0.CCJJxP

by Weenie


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F45
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by F45

Depends on the tire size you want to use. For optimal aero, the rim should be at least 5% wider than the tire.

bm0p700f
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by bm0p700f

Also how quick depends on the yaw angle. At low yaw angle the wider rim should a be a fraction less aero. 28mm wide rim exist so people can use 25mm tyres on them as they often spread out to 27mm or 28mm wide.

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mpulsiv
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by mpulsiv

bm0p700f wrote:Also how quick depends on the yaw angle. At low yaw angle the wider rim should a be a fraction less aero. 28mm wide rim exist so people can use 25mm tyres on them as they often spread out to 27mm or 28mm wide.


Yes, ~27mm rims exist but it's limited selection and all disc.

http://www.novemberbicycles.com/range

http://www.boydcycling.com/2016-44mm-cl ... ront-wheel

http://www.huntbikewheels.com/collectio ... er-nov-wk3

http://www.venn-cycling.com/index.php/w ... 5tcdwheels

http://www.yishunbike.com/2016_road_rim ... ravel-rims

http://www.specialized.com/us/en/118463

http://www.derbyrims.com/technical-specs---faq-s.html

http://www.noxcomposites.com/s36r

Enve 4.5 AR is 21mm inner and 31mm outer!
http://enve.com/products/ses-4-5-ar

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Last edited by mpulsiv on Thu Nov 10, 2016 6:31 am, edited 6 times in total.
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Nefarious86
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by Nefarious86

CLX64 is 29mm wide?
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spdntrxi
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by spdntrxi

getting so wide .. I need a new frame.

Hexsense
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by Hexsense

yep for optimal aerodynamic in the front, rim width at brake track should be atleast 105% of the measured tire width.

read:
https://silca.cc/blogs/journal/part-5-t ... rodynamics

i found that many of 28mm wide rim (like chinese carbon fiber wheels from ebay user that people were talked about in chinese wheels thread a while ago) are only about 26mm at brake track. With most 23c tire on their 16.9mm internal rim being 24.8-25.xx wide and 25c become 27-28mm wide, the wheel are still most optimized for 23c in the front.

for 25mm width rim with narrower brake track, i'm afraid it would be most aero optimized for 22c tire if used in the front. it will still be a good rear wheel with wide tire though.

pdlpsher1
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by pdlpsher1

I think 24mm exterior and 17mm interior is the sweet spot. Anything wider gives you diminishing returns in aeroness at substantially higher weight.


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F45
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by F45

Sweet spot for me is 30mm at the brake track and 18mm inner so I can use 28mm tires.

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mpulsiv
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by mpulsiv

F45 wrote:Sweet spot for me is 30mm at the brake track and 18mm inner so I can use 28mm tires.


Please list number of wheels and rims that are 28mm+ at the brake track. I would like to expand the list wheels and rims that posted earlier.


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F45
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by F45

I think just those enve disc specific wheels.

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dannyboybad
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by dannyboybad

The only 28's I found were the new zipp 808's...

I want to use 25mm tyres front and back...

I have Reynolds Strike SLG Carbon Wheelset Clincher... 60mm with 25mm external. They come with 23 tyre in the front and 25 in the back.

I know Im looming at marginal gains... going from the 60 to the 88 but it will make me feel much faster, if not look faster.

Is there a product out there like the Mavic CX01 blades for generic carbon clinchers/tubs that could help keep the air flow attached to the tyre / wheel.

Anyway
Thanks for the responses...

sawyer
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by sawyer

new shimanos are 28mm

some people are massively overthinking this

just keep the rim / tyre transition smooth and don't worry about the rest
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mpulsiv
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by mpulsiv

sawyer wrote:new shimanos are 28mm

some people are massively overthinking this

just keep the rim / tyre transition smooth and don't worry about the rest


You can't keep rim/tire transition smooth because ~24mm at brake track is the new "wide" standard. Well, this standard that rim manufacturer swear by are few years behind. If you are looking for rolling resistance, comfort and grip than you should ride 25mm tire at a bare minimum. When I mount 25mm tire on a wide rim (~24mm at brake track) it's far from smooth transition. A tire overlap at least 3mm. The moral of the story is buy wheels/rims that are at least 28mm at the brake track for smooth transition but selection is quite limited. See my list in the previous post.


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by Weenie


Marin
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by Marin

Get 25mm wide wheels, run good, high TPI tires that are labeled as 23, they will come out to nearly 25 on a wide rim, done.

Tire width is overrated, tire quality is what it's about.

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