It more depends on the width on the inside of the rim, as this will determine the width and hence fit of the tyre on the rim.
A 23mm conti gp 4000s will likely be a great training / race tyre.
A 25mm of the same will ride more smoothly....
You mention you are noob, so I remind you of the pressure drop from standard 23mm tyre rim combo to a wide rim 23mm tyre typically 10% lower than what you might have run previously...
Same drop again for the 25 mm.....

Eg standard would be 105/115psi FR/RR resp.
23mm wide rim 95 and 105psi
25mm wide rim 85 and 95psi etc....

Also it you set your brKe callipers cam open when you set the wide rim position then if you revert to standard width rim you can get the brake to function just with a flick of the cam .... Note the 23 tyre on wide rim will drop out from the brake callipers untouched ie no need to open the cam..... A 25 tyre may need a small tug....

Oh and standard inner tubes will run just fine in 23 and 25 tyres...
28 may be time to get a larger width tube.....

Best of luck

Here's what the rim looks like, if it helps even more.

Yeah so about 19 mm internal width...
23 will likely be fastest .... Aero wise
25s ride really nice on rougher roads....
Pick to suit your needs....
Have been know to run23 fe and 25 rear...

If I were you (and I have almost identical geometry rims) 23mm GP 4000s with ultra light butyl tubes.... I use bontrager cos they are always available in LBS.... Play with pressures to suit your mass ....

I just bought 25mm wide carbon clinchers and put 23mm Schwalbe's on them. They ride awesome!

Yeah they ride so well especially if you drop the pressures to take advantage of the increased volume...

Or are you dropping the pressure to go back to normal because of the less spring shaped casing?

=)

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

wheels of that shape/size have proven to be very very fast with the conti 4000S 23mm clincher. The aerodynamic match is very good.

In some cases you might be a wee bit faster with narrower tires, especially up front. I would not run a 25mm tire up front unless you hate winning.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

I'm about to jump on the 'wider is faster' bandwagon, but being the noob that I am, I am unsure of wether 700x25mm or 700x28mm is the best fit for my wheels?

A couple of little birds have told me 20mm is fastest. Even on wide rims. But go ahead and run fat tires on them if you like.

Unlike tubulars, a clincher tire gets wider when you put it on a wide rim. Ideally you don't want any bulge at the tire/rim transition, but rather a continuous taper.

What rim is that?

What are you using this set up for? Are you racing on theses wheels or just riding? Fun or Fast?

must have been a mocking bird

The hints are all there!
On one of the widest rims in production, the 303

23mm is more aero than 25
22 is more aero than 23

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

You mean most aero.

probably fastest too, since there just happens to be a really fast 20mm clincher tire right now.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Is the crr testing being done on a wide rim?

Jack is spot on..the narrower tires will generally be a bit faster even on wider rims. Remember, in the whole progression of things, we only started making wider and wider rims because people were using tires that were too wide for the rims we were making. My rule of thumb when I wrote that very first white paper on the 27.5mm wide 808 that launched in 2004, was that the rim should be at least 105% the width of the tire...and that is the actual, inflated width, not the printed width as it varies quite widely. Back when everybody raced on 20-21mm tires, 23mm rims worked pretty well, but as people began using wider tires, we realized that they were literally throwing away much of the aero benefit they were buying..but in the end, the slightly narrower tire will generally win out unless it's poorly shaped.

In this graph, you see that the GP4000s has a faster shape than the Attack 22, but the attack is a bit faster at low yaw just on reduced frontal area. Part of what makes the GP4000s so impressive is that it measures more like 24-24.5mm wide depending on pressure compared to 22-22.5 for the Attack and yet is so similar. Put a 20 or 21mm tire on there and you will definitely see it further improve.

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did that need to be in pink or did you miss all my comments in fastest clincher thread? :)

Is the crr testing being done on a wide rim?

Al Morrison did that few years back. No difference at same PSI. Which is what I'd expect. When you reduce pressure to improve the ride (because the more vertical sidewalls make the ride harsher) I'd expect Crr to go up.

I think it would be wise to abandon any fantasies about wide rims enhancing any properties we care about in TTs... except one... and that is the aero benefit... slightly lower drag and better crosswind performance.

Back when everybody raced on 20-21mm tires, 23mm rims worked pretty well, but as people began using wider tires, we realized that they were literally throwing away much of the aero benefit they were buying....
the rim should be at least 105% the width of the tire...and that is the actual, inflated width, not the printed width as it varies quite widely.

And the inflated width of a clincher is usually wider than the brake tracks. When I mounted a 23mm GP4000 on a 28mm wide rim (29er Stan's) it was >29mm wide.

It's probably best for aero if the clincher hook is rather pronounced and the brake track thick so the tire remains narrower than the brake track. Better for leading and trailing edge both.

Is that potentially what makes the new Reynolds wheels perform well?



It actually looks like a narrow tubular tire mounted to a wide rim.

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/kj

http://kjmcawesome.tumblr.com/

It actually makes me want to see a test with something like a 21mm Vittoria tubular on a Firecrest rim.

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/kj

http://kjmcawesome.tumblr.com/

>I think it would be wise to abandon any fantasies about wide rims enhancing any properties we care about in TTs... except one... and that is the aero benefit... slightly lower drag and better crosswind performance.

And grip (because lower pressure). My home TT course has a sharp, descending, off-camber turn that you hit 6 times for 40K. It hit it at full speed (~28MPH) in aero position on C2-width Jets with 23mm tires inflated to 90. I never had the confidence to do that on HED3's with 19mm tires inflated to 120. I'd come out of aero and scrub a bit of speed. Maybe I could have. Never actually skidded on the front-only HED3, but some sort of internal mental process told me I'd be in trouble on that turn. Could just be HED's C2 marketing working on me. But whatever, it worked.

mother of science people try so so damn hard to find a reason to go wide up front for time trials.

WHAT ABOUT QUANTUM FLUCTUATIONS?

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

>mother of science people try so so damn hard to find a reason to go wide up front for time trials.


Speaking of science, the relationship between pressure and grip is science. And you get more grip at lower pressure. On a technical TT course I don't think you can ignore this.

There is a pressure at which grip is optimal, above or below which it gets worse. That optimum pressure depends on the tire size, shape, and mass on it.

A wider tire will generally afford more grip, all else equal, at it's optimal pressure, but not always.

Even on a technical course grip difference usually make for extremely small time differences in brief moments. So you don't want to be sucking away time the rest of the

oh screw it I'm done.

run 28s, you get more grip

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter