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25mm vs. 28mm....for speed

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25mm vs. 28mm....for speed

Old 05-10-24, 10:20 AM
  #26  
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Originally Posted by SoSmellyAir
According to this road.cc review the Mavic SSC Cosmic Carbon has an internal width of 19 mm.

Review: Mavic Cosmic Carbon 40 wheels | road.cc
Yeah, they gotta have said that wrong. I see where it says the “rim bed” is 19mm, but there’s no way Mavic was making 19mm internal width rims in 2015…no way. Unless…are those tubulars? Maybe external width on a clincher is the same as rim bed width on a tubular? But yeah, no way it can be correct for a clincher…I’d bet my bike that a Cosmic Carbone 40 clincher was not 19mm internal, and most likely 13mm only.

EDIT: So, I just hit the Wayback Machine and the Mavic site in 2015 lists the Cosmic Carbone 40 clincher as 13mm internal:
https://web.archive.org/web/20150321...c-carbone-40-c

Last edited by chaadster; 05-10-24 at 10:27 AM. Reason: link
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Old 05-10-24, 04:29 PM
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Originally Posted by chaadster
I’d bet my bike that a Cosmic Carbone 40 clincher was not 19mm internal, and most likely 13mm only.

EDIT: So, I just hit the Wayback Machine and the Mavic site in 2015 lists the Cosmic Carbone 40 clincher as 13mm internal:
https://web.archive.org/web/20150321...c-carbone-40-c
Yeah, I suppose I must have misunderstood that review. 13 mm internal width is way too narrow, even for an older, narrower frame.

Originally Posted by eduskator
My SL8 came with the Roval Rapide CLII wheels and the front one has a 35mm external width (wide!) while the rear one has a 30mm external width. The wheels are said to be optimized for 26mm tires and it's said to be backed up by wind tunnel, software simulation and real life testing. This said, my rims are larger than my tires, and this, even if I swapped the 26mm tires for 28mm tires this year.
I recently bought those same wheels for my new bike and am going to install 28 mm tires too. Does the 26 mm tire look like a rubber band on the front wheel? (Like the people who go for the stretch look by installing 215 mm tires on their 8.5" wide wheels.)
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Old 05-10-24, 07:41 PM
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Originally Posted by SoSmellyAir
Yeah, I suppose I must have misunderstood that review.
No, I don’t think you did; you cited the review exactly right. It’s just that the review was either unclear about them being tubular, or it was simply incorrect. Regardless, we figured it out! 👍🏽
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Old 05-11-24, 10:25 AM
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People thought 25s were faster for decades, it wasn’t until they started trying to sell something (gravel bikes N+1ing roadies) that study after study comes out extolling the benefits of wider tires at lower pressures.
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Old 05-12-24, 11:12 AM
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My own opinion is that tire it's more complicated than just tire width... Tire construction and materials seems to have a definite effect on rolling resistance.
As well as matching tire width to the rim shape/width - as noted by test done by Both HED and ZIPP on air flow. Combine that with tire pressure used, road surface/riding conditions, overall weight on tire, and you get a result.
If one looks at both air resistance and rolling resistance tests, commonly available, there's a sizeable difference in tires and widths in all the result levels.
Tires, like bike performance has improved greatly over the years... How a 200 lb rider experiences that, compared to a 150 or 120 lb rider, will all be different.
Choosing is the 'fun' we have in deciding what works best for our own 'desires' - speed/performance and or any combination of durability and long life, cost - we get to decide.
Ride On
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Old 05-13-24, 04:45 AM
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Originally Posted by SoSmellyAir
Yeah, I suppose I must have misunderstood that review. 13 mm internal width is way too narrow, even for an older, narrower frame.



I recently bought those same wheels for my new bike and am going to install 28 mm tires too. Does the 26 mm tire look like a rubber band on the front wheel? (Like the people who go for the stretch look by installing 215 mm tires on their 8.5" wide wheels.)
No they don't! It's a very good combo IMO. I just prefer the 28mm for the extra comfort / lower pressure.
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Old 05-13-24, 06:05 AM
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Originally Posted by ArgoMan
Hey all. This topic has probably been hammered to near lifelessness, but I'd like some perspective as it relates to my intended application.
...



...on a serious note, improving your position on the bike will pay much bigger dividends than your tire selection.

Last edited by Turnin_Wrenches; 05-13-24 at 06:09 AM.
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Old 05-13-24, 06:10 AM
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Canyon equips their Aeroads with 28 rear and 25 front. At least my Aeroad CF SL came that way. Not sure what their rationale is but it may be something to consider.
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Old 05-13-24, 06:13 AM
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No matter where you are, or how fast you're going, Here You Are

Pick a tire and just Ride
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Old 05-13-24, 07:30 AM
  #35  
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Originally Posted by Russ Roth
Part of this answer will be defined by your wheels, how wide are they? Flo cycling did some testing on this using the rule of 105 (rim should be 105% of tire), they found that with their wheels 25c was aerodynamically faster (roughly 104% vs 97%) going to 28c had lower rolling resistance. The combined difference had 28c barely edge things out, with a difference of .09w on the least aero rim to .43w on their most aero rim. That would suggest that wider still would have had enough aero disadvantage to not be worth it though I wonder if it also due to the tire not being a less optimal shape when going wider which could effect the amount of reduced rolling resistance. Course their test might be old enough 30c wasn't popular yet. The result is that I'd very much base it on your wheels. If you have an older, narrower rim and you'd drop somewhere below that 95% rim width, I'd be disinclined; if you have newer, wider rims I'd go wider if the frame can handle it.
This. For time trialing you’re almost certainly going to be faster with tire size optimized for your wheels. The wheel manufacturer for deep sectioned wheels usually states the tire size for which their wheels are optimized.
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Old 05-13-24, 07:37 AM
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Originally Posted by Turnin_Wrenches
...



...on a serious note, improving your position on the bike will pay much bigger dividends than your tire selection.
which is the fallacy we always get in these threads. Optimizing your tires and your position are not mutually exclusive. You’ll be faster with the best wheel tire setup, and the best position, than just the best position.

Time trials are won and lost by small margins. Every small improvement adds up. The right shoe covers, the right gloves, the right skin suit, the right tires, etc, each may only save a few watts, but add it all up and we’re talking a minute or more over a 40k.

So, improve your position, raise your FTP, and optimize your equipment.
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