Tire size and aero rims: how almost every clincher user defeats the purpose of aero rims

Back by popular demand, the general all-things Road forum!

Moderator: robbosmans

User avatar
Kayrehn
Posts: 1775
Joined: Thu Mar 24, 2011 6:06 pm

by Kayrehn

Easton aero 55 wheels recommend 23mm tires for their 28mm outer width rims, so I think that conclusion is true.

Sent from my SM-G930F using Tapatalk

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



bm0p700f
in the industry
Posts: 5777
Joined: Sat May 12, 2012 7:25 pm
Location: Glermsford, Suffolk U.K
Contact:

by bm0p700f

It really depends who you are aiming the wheels at. It is not confusing. For the highest pace you a tyre narrower than the rim. This works on smooth circuits.

If you are not competing or competing on a rough circuit then a wider tyre can help but then question whether that is the best use of your aero wheels.

Once again it is a judgement call.

tb123
Posts: 33
Joined: Mon Jan 14, 2013 9:19 am

by tb123

i get the feeling that for a smooth out-and-back TT course that perhaps a 23mm tyre would be best, but for everything else in a real world scenario, wider tyre, less pressure, less rolling resistance, comfort, grip etc etc would still win out. Anyway, I'm still gonna rock the 25mm Open Corsa's on my 404's as they provide a much nicer ride.

helldiver
Posts: 85
Joined: Sat Dec 20, 2014 5:46 pm
Location: Slovakia
Contact:

by helldiver

That's why i run nice, supple (350tpi) 22mm tubular on my 24,2mm wide front wheel. People keep asking me why and recommending that I should run 25mm tubular instead, they don't quite get it that it would kind of defeat the purpose of the 50mm deep aero wheels. The funniest thing is that those people often run their 25mm tubulars at the same pressure (7-7,5bar) as my 22mm front tyre, effectively making it even harsher and less comfortable then my setup ! Mental suggestion is very strong, and if everyone around is raving about "comfortable" 25mm tyres, you will for sure feel it, even if you run it at the same pressure as smaller tyres and science actually says you even slightly decreased your comfort: https://silca.cc/blogs/journal/118616068-part-2-tire-stiffness-wider-is-stiffer-harsher

User avatar
euan
Posts: 1571
Joined: Sat Sep 05, 2009 11:20 am

by euan

Yeah but what about when tested as a whole bike...?

cmcdonnell
Posts: 278
Joined: Sun Aug 02, 2015 7:50 pm

by cmcdonnell

I felt this when I tied a 25mm gp 4000 on my Bora's which are 17C and 24.2mm outside width. The 25 mm clincher looked huge so swapped for a 23mm which came up at 25mm. Now on Michelin Power Comp's 23 which come up at 24.4 and look "right". I did try the 25mm's at 85/90PSI and did not find any perceptible benefit so now win the wide 23mm's at 95/100PSI and the ride is good on UK roads and it feels fast. I think there is no real performance argument for 25mm clinchers at the same (high) PSI but if you feel fatigued and beaten up after a ride then they may be worth it for you. Narrower is always going to be more aero and pretty much every manufacturer that quote any data say the tyre should be narrower than the rim. I also have never experienced a lack of grip on 23mm clinchers in normal summer conditions. It's all a matter of balance. I don't feel I need any more comfort so unless they can show that 25mm clinchers can out perform 23mm at an optimum pressure they are of no interest but that's just me.

I do use the 25mm clinchers on my winter wheels these days because they do seem more comfortable at 85/90PSI but they do feel slower but I don't really care in the winter. But I also managed for 15 years in the Surrey Hills with 23mm tyres all year with no problems

My own biased opinion is that wider tyres and rims are aimed at the same market as shorter top tubes and longer head tubes!!
Bianchi Oltre XR2 + Campagnolo Super Record 11 + Campagnolo Bora 50C
Litespeed T1 + Campagnolo Chorus 11 + Campagnolo Shamal Ultra

Marin
Posts: 4035
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

There are no real reasons why wider tires should be more comfortable - they are harder at the same pressure, and they don't get different suspension properties from being larger.

There are no real reasons why wider tires should be faster if you run them at the same level of comfort as a narrower tire, i.e. you drop your pressure to make them as hard as the narrower tire.

There are no real reasons why wider tires should have more grip than narrower ones - increased road contact surface also means less pressure per area, which exactly cancels out. Plus, contact area is more dependent on pressure than on tire size anyway, so not really larger to begin with.

So comfort and grip are mostly a factor of tire quality, not tire size.

Additionally, with rims with wide internal widths, you can't go by manufacturer stated tire width, most "23 mm" tires will be over 25mm wide on an 18c rim.

Conclusion: Get a high-TPI tire in 22 or 23mm stated width, and enjoy a reasonably aerodynamic 24-26mm tire on your wide rims. Everything that comes out over 26mm wide is a mixed surface tire IMO.

nemeseri
Posts: 794
Joined: Tue Apr 07, 2015 5:40 pm

by nemeseri

ichobi wrote:So when some manufacturers are claiming you should be running wider tire with their now wider new aero rims to gain benefits in handling and comfort (which is true), they did not forsee this aero drawbacks or haven't done enough research? Brands like Campagnolo actually claims it's more aero to run wide tire with wide rim (no evidence, studies, or any figures to back up the claim).

It comes down to where your put your priorities. All out aero or better comfort and handling, which save time and power and not in a minimal amount either.


I'm just guessing, but my hunch is that most of the manufacturers' aero related focus was on tubulars and not clinchers. This clearly changed in the past 5 years for most manufacturers, like zipp / enve. Others moved slower like Mavic.

You are absolutely right about comfort and handling and I recommend the other article in the same blog focusing on road surface, tire pressure and tire rolling resistance: https://silca.cc/blogs/journal/part-4b- ... -impedance

What was the most shocking in this series for me is that how delicate the connection between these often overlooked things.

Stueys
Posts: 673
Joined: Sat Nov 22, 2014 1:12 pm

by Stueys

I asked Enve for their advice when I bought my 4.5's. They said the 23cc tyre came up fastest from an aero perspective but in a real world scenario a 25cc would have less rolling resistance. They hadn't tested rolling resistance but inferred they suspected there wouldn't be a significant difference once this was factored in.

nemeseri
Posts: 794
Joined: Tue Apr 07, 2015 5:40 pm

by nemeseri

Stueys wrote:I asked Enve for their advice when I bought my 4.5's. They said the 23cc tyre came up fastest from an aero perspective but in a real world scenario a 25cc would have less rolling resistance. They hadn't tested rolling resistance but inferred they suspected there wouldn't be a significant difference once this was factored in.


Are your wheels tubulars or clinchers? Did they recommend a tire that's labeled as 23mm or that's measured at 23mm on the rim?
I really think that usually wheel manufacturers refer to aero tests done on tubular rims and tires. In the case of clinchers, the 23mm tire becomes a 25, a 25mm tire becomes 27-28.

Also wider tires only roll faster than narrower ones if the tire pressure is the same. If you drop pressure, the crr will suffer. Reference: http://www.bicyclerollingresistance.com ... i-23-25-28

spdntrxi
Posts: 5782
Joined: Sat Jul 20, 2013 6:11 pm

by spdntrxi

Stueys wrote:I asked Enve for their advice when I bought my 4.5's. They said the 23cc tyre came up fastest from an aero perspective but in a real world scenario a 25cc would have less rolling resistance. They hadn't tested rolling resistance but inferred they suspected there wouldn't be a significant difference once this was factored in.

I use 23 on my 3.4 and 6.7 and will use 23 on my up coming 4.5 as well. (Clinchers)
I have 2.2 tubs and I'm using 25 Veloflex arenburgs with those . 23 on those rims have to much of that auto Jspec look


Sent from my iPhone using Tapatalk
2024 BMC TeamMachine R Building
2018 BMC TImeMachine Road
2002 Moots Compact-SL- getting aero look makeover
2019 Parlee Z0XD - "classified"
2023 Pivot E-Vault - completed project, full Xplr package

kulivontot
Posts: 1163
Joined: Sun May 16, 2010 7:28 pm

by kulivontot

I mean if we're going to nitpick, then doesn't running clinchers period defeat the purpose of aero rims?

spdntrxi
Posts: 5782
Joined: Sat Jul 20, 2013 6:11 pm

by spdntrxi

kulivontot wrote:I mean if we're going to nitpick, then doesn't running clinchers period defeat the purpose of aero rims?


nope... many clinchers with the way they interact with the rim edge can be more aero.
2024 BMC TeamMachine R Building
2018 BMC TImeMachine Road
2002 Moots Compact-SL- getting aero look makeover
2019 Parlee Z0XD - "classified"
2023 Pivot E-Vault - completed project, full Xplr package

savechief
Posts: 354
Joined: Wed Aug 31, 2011 2:36 am

by savechief

nemeseri wrote:Also wider tires only roll faster than narrower ones if the tire pressure is the same. If you drop pressure, the crr will suffer. Reference: http://www.bicyclerollingresistance.com ... i-23-25-28


Not necessarily true. In the page you linked, the 28c tire at 80psi rolls faster than either the 23c or 25c at 100psi.
Time VXRS Ulteam (7.16 kg)
viewtopic.php?f=10&t=120268

Stueys
Posts: 673
Joined: Sat Nov 22, 2014 1:12 pm

by Stueys

nemeseri wrote:
Stueys wrote:I asked Enve for their advice when I bought my 4.5's. They said the 23cc tyre came up fastest from an aero perspective but in a real world scenario a 25cc would have less rolling resistance. They hadn't tested rolling resistance but inferred they suspected there wouldn't be a significant difference once this was factored in.


Are your wheels tubulars or clinchers? Did they recommend a tire that's labeled as 23mm or that's measured at 23mm on the rim?
I really think that usually wheel manufacturers refer to aero tests done on tubular rims and tires. In the case of clinchers, the 23mm tire becomes a 25, a 25mm tire becomes 27-28.

Also wider tires only roll faster than narrower ones if the tire pressure is the same. If you drop pressure, the crr will suffer. Reference: http://www.bicyclerollingresistance.com ... i-23-25-28


- Clinchers. The thread is about clinchers right?
- suspect they recommended based on actual size, though I didn't actually ask them to give me a recommendation for incorrectly labelled tyres. There isn't much wheel manufacturers can do on that

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



Post Reply