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Old 01-25-14, 11:16 AM   #1
waynesulak
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Fatter Race Tires Gaining Acceptance

Cycling News at Tour Down Under: "25mm tyres are becoming a common sight in the pro ranks - some teams didn't even bring 23c tyres with them"

Could it be that 23mm tires are going the way of 20mm tires? Interesting that racers are using 25mm tires and wide rims but carrying less than half most tandem teams' load.
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Old 01-25-14, 12:02 PM   #2
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It's really not about the tires but about the rims. About half of the pro peloton is on 25's because their wheels are wider and designed for special 25mm tires. The main goal is to be more aerodynamic. Go to Zipps web site, there is a big long read on it. Zipp was one of the first wheel manufacturers to make those kinds of rims. Teams that still use "traditional" wheels are still on 23's for the most part.

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Old 01-27-14, 12:46 PM   #3
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Originally Posted by Homeyba View Post
It's really not about the tires but about the rims. About half of the pro peloton is on 25's because their wheels are wider and designed for special 25mm tires. The main goal is to be more aerodynamic. Go to Zipps web site, there is a big long read on it. Zipp was one of the first wheel manufacturers to make those kinds of rims. Teams that still use "traditional" wheels are still on 23's for the most part.
The new wider rims certainly have taken over the market. It is my understanding however that the key to the new wider rim shape is the idea that the rim should not form a wedge behind the tire but should meet the tire and actually widen out before beginning to reduce in size.



I remember reading when the wheels first came out that they were optimized for 23mm tires but that narrower and wider tires also worked well. I can not find where I read that to post it here. Looking at the Zipp FAQ about tire width I found:

Quote:

How do I choose the correct tire width?

Tire choice depends highly on user preference and conditions. To summarize, a 21mm has superior aerodynamics with our rims; a 23mm is larger and subsequently has better ride quality and rim protection, but at a slight aero penalty. Here are some questions you can ask that will help guide your decision:


Triathlon/Time trial? In general – 21mm.
Road racing? In general – 23mm.
Training and/or daily riding? 23mm+

Dry? 21mm at normal recommended pressure.
Wet? 23mm at a slightly lower pressure.

Smooth roads? 21mm at normal recommended pressure.
Rough roads? 23mm at a slightly lower pressure.

User prefers slight aero benefit of 21's at the expense of a little ride comfort, rim protection, and rolling resistance? Use 21mm.
User prefers slightly better ride comfort, rim protection, and rolling resistance of 23's at the expense of a little aero? Use 23mm.

Rider weighs less? 21mm.
Rider weighs more? 23mm.
Here is a direct statement that that 21mm tires give better aerodynamics than a 23mm tire. There is no mention of 25mm tires but there is certainly no evidence that 25mm tires are required or even the first choice for the Firecrest rims.

It seems to me that at the time the rims were designed 21-23mm were the standard and that is what they were designed for. When wider rims were put in the hands of the pros they moved to wider 25mm tires because they were seen as getting most of the benefits of the new rim and the benefits of a wider tire. If a 25mm tire were preferred to a 23mm or 21mm tire for aerodynamics I feel Zipp would not state the opposite on its web site. This makes sense since the cross section size increase of wider tires is hard to overcome regardless of rim shape. Another factor could be that the wider tires above 21mm do not mate quite as well with design of the new rim's bead width.

The video at:

http://www.zipp.com/technologies/aer.../firecrest.php

also gives some info about the shape at 6 min 30 sec and tire widths at 9 min 50 sec.
Attached Images
File Type: jpg 404_rimshape.jpg (17.7 KB, 3 views)

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Old 01-27-14, 10:22 PM   #4
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I think that FAQ may be old as it doesn't even mention the new Firecrest rim which is designed specifically for a 25mm tire. I read an article from Zipp last year (or maybe it was a cyclenews article with a Zipp interview) some time where they said that the main reason was in fact aerodynamics. It makes no sense that they would design a slower racing wheel. Comfort does not trump speed in racing equipment. It may be an added benefit but that's it.
Here is the article from Zipp on the Firecrest (not the one I was thinking of) and they concentrate on three areas, speed/aerodynamics, stability and strength. I found this interesting "With Firecrest, the 404 Firecrest Tubular (58mm rim depth) matches the aero performance of the pre-Firecrest 808 (82mm depth)." They don't give numbers but that sounds significantly more aero than the older version of the 404.
http://www.zipp.com/technologies/aer.../firecrest.php
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Old 01-28-14, 10:10 AM   #5
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Originally Posted by Homeyba View Post
I think that FAQ may be old as it doesn't even mention the new Firecrest rim which is designed specifically for a 25mm tire. I read an article from Zipp last year (or maybe it was a cyclenews article with a Zipp interview) some time where they said that the main reason was in fact aerodynamics. It makes no sense that they would design a slower racing wheel. Comfort does not trump speed in racing equipment. It may be an added benefit but that's it.
Here is the article from Zipp on the Firecrest (not the one I was thinking of) and they concentrate on three areas, speed/aerodynamics, stability and strength. I found this interesting "With Firecrest, the 404 Firecrest Tubular (58mm rim depth) matches the aero performance of the pre-Firecrest 808 (82mm depth)." They don't give numbers but that sounds significantly more aero than the older version of the 404.
http://www.zipp.com/technologies/aer.../firecrest.php

I think you might be misunderstanding me. I agree that aero performance is the primary concern and that the Firecrest is an improvement in that area. I never mentioned comfort because in that world it is all about high speed and that means aero. I just think the evidence supports the view that the Firecrest rim shape was designed with the 23mm tire in mind and is somewhat more aero with narrower 23mm tires than 25mm tires. The FAQ is what it is but why should we assume it is outdated and misleading about the company's flagship wheel? In any case the video is all about the Firecrest design so it must be current and it clearly mentions 23mm tires and does not mention 25mm tires. If the rim was designed around the 25mm and Zipp suggests a 25mm tire be used then why not mention it in the video?

If the wheel is designed for a 23mm tire then it is more interesting that teams are using 25mm tires for some reason other than the Firecrest design requirements. My guess is rolling resistance? Only Zipp knows for sure but at this point I see no evidence the Firecrest requires or is more aero with 25mm tires. Maybe I missed Zipp's suggestion of 25mm tire use somewhere on the web site. If you find it please pass it along.

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Old 01-28-14, 08:59 PM   #6
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You are probably correct. I looked at the web site and it doesn't mention 25's anywhere. That's kind of funny because our race team was sponsored by Zipp and the wheels the team got last year came with Zipp Tangente 25mm tires on them. I just assumed that's what they did. They were an interesting tire because they had different profile than regular tires and were flush with the rim on the sides. I wish I had one here to take a picture of to share. They apparently don't exist anywhere else. I should have probably looked it up before I opened my keyboard instead of relying on my sad memory. Sorry for running you down the wrong path there.
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Old 01-29-14, 08:05 AM   #7
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Quote:
Originally Posted by Homeyba View Post
You are probably correct. I looked at the web site and it doesn't mention 25's anywhere. That's kind of funny because our race team was sponsored by Zipp and the wheels the team got last year came with Zipp Tangente 25mm tires on them. I just assumed that's what they did. They were an interesting tire because they had different profile than regular tires and were flush with the rim on the sides. I wish I had one here to take a picture of to share. They apparently don't exist anywhere else. I should have probably looked it up before I opened my keyboard instead of relying on my sad memory. Sorry for running you down the wrong path there.
No problem. The Cycling press contributes to confusion on equipment issues with sloppy reporting. In this case I recall articles that reported teams with 25mm tires and new rims and mentioned the combination as if it was one unified decision without doing what we amateurs did - look at the manufacturer's information. Better yet when Zipp is making the rounds pushing their revolutionary rim shape Cycling News or Velo News could simply ask Zipp, what actual measured tire with do you recommend for the best aero profile? Seems like a natural question to me instead of "Is it fast?"

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Old 01-29-14, 08:20 AM   #8
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.. Seems like a natural question to me instead of "Is it fast?"
Yeah but, we're all (well, some of anyway) racers at heart and "is it fast?" is all that matters.
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Old 01-29-14, 12:17 PM   #9
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The narrow tyres are fastest on a wide rim but despite this even those racing will give up a tiny bit of speed if they prefer some other advantages. eg comfort, handling, etc. They aren't all on aero frames are they? On a TT you won't see these compromises so much.
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Old 02-01-14, 11:23 AM   #10
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Update -

While browsing I ran into Enve carbon rims 26mm/24mm wide. They suggest 23mm tires.

http://www.enve.com/wheels/road/8.9clincher.aspx
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Old 02-22-14, 04:59 AM   #11
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Aero wheels/tyre

It is not about the width of the tyre, it is the interface tyre/rim that they are all working on, I too have read reports of 25mm tyres in use, but most are still at 23mm ish, as explained in the article linked to:
http://triathlon.competitor.com/2012...o-wheels_60548
One of the European manufacturers (cannot remember who) was selling an insert last year to fit around the rim that smoothed the tyre/rim joint out to a flat surface, allowing use of various makers tyres with their new aero rims.
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