Is the 20mm SS you tested the same as the newer 23 mm version?

If so, I will be holding on to these 23mm tires for dear life.

There is some slight disagreement between these stats and brr, yes?

Thanks

Do you ever hear from Al Morrison?

What psi are these done at? Have you noticed different tires having different rates of change of crr with respect to tire pressure?

So if one wants to have the best setup for race day, and one plans to switch out a training tire for a "faster" race tire, how long before (how many mikes/km) a race should this be done? I'm assuming there's a break-in period.

You'll find it here:


http://bikeblather.blogspot.com/...ng-caught-up-ii.html

Summary:

Continental GP TT 23C = .0028, 26W for pair @ 40kph
Continental GP Force 24C = .0030, 27W for pair @ 40kph
Continental SuperSonic 20C = .0030, 28W for pair @ 40kph
Continental GP4000SII 25C = .0031, 28W for pair @ 40kph
Spec. S-Works Turbo TL 26C = .0032, 30W for pair @ 40kph (tubeless)
Continental GP Attack 22C = .0033, 31W for pair @ 40kph
Continental GP4000SII 23C = .0034, 31W for pair @ 40kph
Schwalbe One Tubeless 25C = .0037, 34W for pair @ 40kph
Schwalbe One Tubeless 23C = .0041, 38W for pair @ 40kph
Felt TTR1 23C = .0048, 45W for pair @ 40kph
Continental Gatorskin 25C = .0048, 45W for pair @ 40kph
Continental Gatorskin 23C = .0052, 48W for pair @ 40kph

What are your thoughts on the GP TT on a Mavic CXR 60 with the blades installed?

I've just switched to Gatorskins for my road bike which coincided with a month off cycling and have really struggled. I put it down to lack of cycling fitness, but perhaps the Gatorskins are a significant contributor??

This is awesome. Thank you.

Do repeat tests suggest a margin of error (or lack thereof) for your tests?

It will be interesting to see how the 20c and 23c GP Supersonics test and measure mounted. Reports from those on ST that have had them in hand say they look like the GP TT casing and tread.

Presumably the same tire without the Vectran breaker layer.

i know he uses butyl. all things equal, swapping latex for butyl keeps the rank order the same except standard clinchers catch up or overtake tubeless and tubulars.

but on second look yours appear pretty consistent with his. enough at least for you each to validate each other pretty well.

From my roller tests, I recall that butyl tubes were a bit of an equalizer. They didn't change the rank, but they kept the really good and the really bad tires from standing out as much.

Is there a difference between brands of latex tubes? One that matches up "best" with a Conti GP TT 23c, for example?

Is there a difference between brands of latex tubes? One that matches up "best" with a Conti GP TT 23c, for example?

What Alan and I both found was that the smaller Michelin tubes (18-20c) had slightly lower CRR than the wider ones ones (22-23c). I have found Challenge and Vittoria tubes to be less reliable than the Michelins.

Also, I think Michelin stopped making latex tubes a couple of years ago...

I bought a couple when I was in France last summer.

Also, I think Michelin stopped making latex tubes a couple of years ago...

So let's say I'm outfitting a set of Knight 95s as my race wheels, are we saying that the 23C Conti TT is the dominant choice for the setup, or should the 20C Supersonic still be considered due to the much narrower profile, even though they roll ever so slightly worse? Or are the aero gains from 20 vs 23 on the super wide state of the art going to be outweighed by the extra contact patch control?

Someone yell at me if I am wrong, but aren't the Knight 95s pretty damn wide? Like on the order of 28mm or something around there? Wouldn't you be much better off, from an aero perspective, with a wider tire than a 20mm Supersonic, even if the Crr is a bit more? If I recall correctly, Ben Hoffman ran a 25mm up front and 28mm on the rear in Kona a year or two ago.

New Old Stock (NOS)?

Thanks for the new results. What is the biggest tire you can test on a 700c rim? There seem to be diminishing returns (aero hit vs improved CRR) beyond 26mm or so, but I would be really curious to see how some of the 30mm+ offerings roll.

Tom--if you do stick with 120psi with wide rims, please (a) wear protective gear; and (b) take videos.

https://www.bike24.de/...earch=Michelin+latex

I've been using the Michelin mtn bike ones for years. They are quite thick and durable - careful about ordering schrader vs. presta - I've made that mistake.

I haven't had great luck with the Michelin road versions. All mine seem to fail at the base of the stem. On my last pair I tried gluing a piece of an old latex tube around this area to kind of 'beef it up' and it did seem to work. The pink Vittorias are my go-to now though.

CCF wrote:

I've never used latex tubes. Building a couple of models on bestbikesplit for IM St. George 70.3 (chosen because it's my first race of the year) gives a time advantage of 81 seconds for the latex tubes. I understand that latex tubes are much more...finicky? than butyl tubes. Is that time savings worth the latex hassle? I'm asking because I honestly have no idea what the 'latex hassle' is.

Really great work, thanks a lot for sharing Tom.

If you don't mind asking, can you share who is sponsoring those tests, is it paid assignment? Do you buy the tires yourself or get them for free for review? Just curios if this is independent test or sponsored by tire/wheel manufacturer?

"That result for the GP TT makes it the new "top dog" for brand new tires I've roller tested. One caveat on that tire though...it measures much larger (24.6mm) than it's rated 23C on my narrow Mavic Open Pro rim, or nearly 2mm wider than a Continental SuperSonic 23C (22.8mm) on the same rim, and is only .0001 lower Crr (~1W difference at 40kph for a pair, or what I consider "tied")."

Tom, from your statement above, when Cda is taken into account what's your guess as to how these two tires compare?


Thank you for sharing your "hobby" results with all of us. I have to admit it is tremendous fun trying to find these marginal gains.


Tim

[
A lot of times, I just buy them myself because I'm curious (such as the Corsa Speed TLRs that just arrived yesterday).

Are you interested in doing a test on the newer SS 23 mm? If you are interested, I can send you a pair if you don't have some already.

Thanks. It's all sponsored by ME. I'm a hobbyist and this is just something I do in my spare time.

The tires are sourced variously. I usually mention where the source of the tires are in the posts I make on the results, but here are some examples of what's happened in the past:

• A lot of times, I just buy them myself because I'm curious (such as the Corsa Speed TLRs that just arrived yesterday). Sometimes the tires are sent to me by other cyclists. A surprisingly large number of the tires in my spreadsheet were sourced in these ways.
• There have been times that tires have been supplied by wheel manufacturers. For example, the majority of the tires in the post above where sent to me by the guys at Flo, and are the SAME tires they used in their wind tunnel tests. I've known Jon and Chris for a while now, and I did that roller testing for them both because I really liked the way the data was going to be presented (aero drag + rolling resistance) and they've been extremely kind to me in the past (such as sending me a wheel after hearing that mine was stolen). Another example is when I tested a bunch of tires for Zipp when they were developing their latest line of Tangente tires. They sent me competitor tires to test along with their own.
• A couple years back, when Greg Kopecky was with ST, he had sourced a large group of tires from various manufacturers (Vittoria, Challenge, Michelin, etc.) which he then sent to me for testing so he could include that information in his reviews hosted here on ST. I had already written a couple of technical articles for ST at that time.
• I've developed a relationship over the years with a couple of the technical guys at Specialized, and at various times they've had their tire guys send me models to test, if they think I'd be interested.

In none of those cases have I ever been paid to do the testing with cash. Sometimes I'm allowed to keep the tires that are sent to me, but many (most?) times the owner merely pays for the shipping for them to be returned. Of the ones I get to keep, if they aren't something I'd likely use myself, I'll give them to friends to use. For the Zipp testing, they wanted all of the tests to be done on their disc for consistency, so they sent me a Super9 for the clincher testing, along with a handful of tubular discs with tires already glued on (I told them I wouldn't do the gluing ;-) The tubular discs were all returned at the end, but they generously told me I could hold onto the Super9 in case they wanted some more tires tested in the future. Unfortunately, that wheel too was stolen (during the same garage break-in that the Flo wheel was taken - along with 3 road bikes...bastards!)

I've had bike industry manufacturers approach me before about how much I charge for testing...and I always say "I don't know what to charge...I'm just doing this for fun." If it's something I feel I want to spend the time on, then I'll either do it just because I'm curious, or we'll figure out some sort of exchange...I had one manufacturer give me a couple of water bottle cages as "compensation", for example ;-)

About the only time I felt I was "paid" for doing roller testing, was when I was approached by Andy Froncioni of Alphamantis. He had a customer who wanted to get some controlled information on some prototype tires they were developing. Andy contacted me to see if I was interested in providing that testing...and he insisted on paying me for the work. Since I had no idea what to "charge", he offered to send to me one of the few protoype Alphamantis Aerostick systems as compensation. I was a bit shocked by that, but wasn't going to say no ;-) Obviously, since the tires I tested at that time were prototypes for that particular manufacturer, those test results never made it into the tire listing spreadsheet. Interestingly enough, I later loaned that Aerostick system to the engineers at Felt, and didn't find out until the bikes were revealed, but apparently it was used during the development of their "left side" track bikes. The guys at Felt sent me a kit (jersey/shorts) as thanks for the loaner. But, in the end, nothing mentioned in this paragraph has to do with the Crr spreadsheet.

So...I guess that a long way of saying "not sponsored"...I just wanted to put that all out there to be totally transparent on what my motivations are. It's really just technical/sporting curiosity on my part. Yeah, it's not as "independent" as a "Consumer Reports"-type review (where all tires are bought in a shop or online), but it's fairly autonomous. I just report the data as I find it.

I hope that answers your question.

I've just switched to Gatorskins for my road bike which coincided with a month off cycling and have really struggled. I put it down to lack of cycling fitness, but perhaps the Gatorskins are a significant contributor??

I've never used latex tubes. Building a couple of models on bestbikesplit for IM St. George 70.3 (chosen because it's my first race of the year) gives a time advantage of 81 seconds for the latex tubes. I understand that latex tubes are much more...finicky? than butyl tubes. Is that time savings worth the latex hassle? I'm asking because I honestly have no idea what the 'latex hassle' is.

Yeah, in a quick search, I found them on Wiggle and Chain Reaction as well...including the MTB sizes!

Then RChung sent me a pic of the side of one of the boxes he picked up in France last year. Here's what's printed on the side:


So, I guess when Michelin said they wouldn't be selling latex tubes any longer, they meant just in the US :-/

On a podcast, the TrainerRoad and Flocycling guys noted a recent Kona contender had raced on gatorskins. They calculated how much time he lost doing that, and sure enough, it was enough that he could have won the race.

Something went seriously wrong with your testing. Not trying to be a jerk, just being objective.

I fired up the good old rollers today. Then I got out "old greenie" -- the only Michelin 18-20c latex tube ever made with a long valve stem and the one I used for all my roller tests over a decade ago!

Here are the preliminary numbers:

Conti GP TT: 0.278
Vittoria Open Corsa: .232


On my rollers with a stand, it was a 12 watt difference -- 71 vs. 59 to go ~25mph. Not even close.

Incidentally, on this rim, the width of the Conti TT measured 23.15 and the Vittoria only 22.71. I didn't adjust for the difference in wheel circumference, so that would improve the numbers for the Conti somewhat.

This is just a preliminary run -- I didn't carefully measure temperature like Tom and Alan do. But the difference is large enough that I know what I will be using.

Yeah...that's odd. What "vintage" Open Corsa is that?

Also, I forget, but what diameter and material are your rollers?

And what are you using for your wheel speed indicator? If it's possible, if you trigger wheel speed off of the roller instead of the wheel, then rollout doesn't matter :-)

This is a very new "Corsa Speed." Rollers are aluminum, ~3.4 inch.

I see that you measure the roller speed. Great idea. I'm working with a very old powertap however.

I don't think this result is that extraordinary. The BRR guy has this tire at 7.7 watts vs. 9.9 for the Conti GP TT. After adjusting for rollout, my test probably shows a somewhat larger difference. I'll run it again, a little more rigorously. But this difference is much bigger than any variation in test conditions could explain.

Without any aero data to go on, my guess would be the SS23 would be slightly faster overall, especially between 0-10deg of yaw angle. In any case, it's tough to go wrong with either as a choice.

this is the crux of it all- are these findings enough for the TT tyre to show up at all your tri's OR does the aero of the 4000s overcome the rr deficit?
its a doozy!

For some reason, I couldn't get as consistent results from my PT wheel data as from the crank PM...I think it might have to follow with the relatively low power levels of the testing and the resolution of the PT readings. I still use the PT wheel for most testing, but not its power output.

As has been suggested above, it could be that Conti tires improve disproportionately with temperature.

AAAHHHHHHHH!!!

This hurts my brain. Ok so now we also have to take temperature into account. Run the Corsa Speed for cool races and the Conti GP/SS for hot ones?

This is a very new "Corsa Speed." Rollers are aluminum, ~3.4 inch.

And is this one of the ones with the tan walls or grey walls? Also you said it measured ~22.7mm. This was a 23mm version. What is the internal width of the wheel you are running it on?

doesn't make sense compared with Tom's testing. he had GP TT at 13w per tire at 40kph. if you take 12w off that puts your corsa at 1w

There is scaling invloved due to the roller's small diameter compared to the infinite diameter of the road.

This is just a preliminary run -- I didn't carefully measure temperature like Tom and Alan do. But the difference is large enough that I know what I will be using.

When and where are they from? My two samples from early summer last year (also grey sidewall) measure more like 27mm on my HED Jet Black, which should have same internal bead width.

The Earth is flat?! ;p

Hi jens... racing again?

You may want to look at the new Conti SS tires as well. And the "open tubular" tires universally suck for aero. May not want to use one on the front.

I've certainly heard the claim about open tubulars, but I'm skeptical. The discontinuity is minuscule -- certainly much smaller than the tire/rim gap for most tires.

The more relevant question is where is my Hed Jet from. It is supposed to measure 25mm on the outside. It's closer to 24mm.

I'm still waiting on my Garmin speed sensor. In the meantime, I ran both tires again at 120 PSI and 25.2 mph.

Here's what I got:

Vittoria Corsa: 57 watts (crank); 55 watts (hub)
GP TT: 66 watts (crank); 65 watts (hub)

This is on the TT bike instead of the road bike, so the weight distr. and wattage are a little different for both.

Based on the crank power, that gives me CRRs of .030 for the GP TT and .0259


Since I ran the GP TT second this time, I figured I'd run it a bit more. I did observe that the by the 5th minute, the power had dropped from 66 watts to 63 watts at the crank and 65 to 63 at the hub. As has been suggested above, it could be that Conti tires improve disproportionately with temperature. That would certainly explain why historically they have done relatively poorly on my tests. I use the first stable reading, rather than allowing the tires to warm up.

I have to agree with rruff.
Over many years of wind tunnel testing I've been hoping for a handmade tire to do well in the tunnel.
Even though the tread edge is miniscule, nevertheless it seems to trip the flow and separate it from the tire -- and almost always from the rim as well. Leads to early stall and the accompanying increase in drag, unfortunately.

Or wS it always out there if you dug deep enough ...

Thanks Ron!

Great to hear from you! IIRC, you were the one who original gave me the spreadsheet (or formula) to convert the roller numbers to CRR. I'm 55, so I hear you on the age thing. I can still pound out decent power for 20 to 40 minutes (which is how long a lot of the TTs are), but then it takes forever to recover.

Great to hear from you! IIRC, you were the one who original gave me the spreadsheet (or formula) to convert the roller numbers to CRR.

What races are you planning?

But since enve does not recommend latex tubes, I'd be using light butyl tubes.

Say what?

Taken from their website

https://enve.zendesk.com/...ENVE-Clincher-Wheels

Of course,braking on carbon surfaces is silly in the first place, so....

True, but as we've seen, if the Crr is low enough, then despite that early stall condition, the tire/wheel combo can be faster overall, especially within the narrow (relatively speaking) yaw angle range in which I'd expect a fast guy like Jens to be operating ;-)

That said though, if one can find a smooth tire (like the SS) that has nearly the same low Crr, then yeah...it's probably better to go that route, from an overall speed standpoint.

I have to agree with rruff.
Over many years of wind tunnel testing I've been hoping for a handmade tire to do well in the tunnel.
Even though the tread edge is miniscule, nevertheless it seems to trip the flow and separate it from the tire -- and almost always from the rim as well. Leads to early stall and the accompanying increase in drag, unfortunately.

Without any aero data to go on, my guess would be the SS23 would be slightly faster overall, especially between 0-10deg of yaw angle. In any case, it's tough to go wrong with either as a choice.

Tom, what are your thoughts on tire choice for a rear wheel in a frame that fares the majority of the leading edge, for example my P3C? Should we be biasing our decision-making even further towards crr and not worrying so much about aero? On my Renn 555 in the back of my P3C I've been running the Force 24C because a) low crr, and; b) it is fairly wide which might help a bit with arse comfort (Renn disc is very stiff, obviously).

That tire probably isn't the very best match to the Renn but I'm thinking with probably the upper 80% of the leading edge being hidden from the wind anyway, maybe it doesn't matter. But then I wonder if what happens at the trailing edge is important. Overthinking, no doubt.

But in general, in a fared back wheel is crr the boss?

Cheers,
Rich.

This sounds unlikely.
A trip would normally be expected to cause early transition from laminar to turbulent flow but rather than cause flow separation and an early stall it would normally cause the exact opposite. Turbulation would energise the boundary layer, delaying flow separation (stall).
Earlier transition to turbulent boundary layer would increase drag a little. So at low angles of attack the drag would likely be higher for a "tripped" design. However at greater angles of attack (i.e. bigger "wind yaw" angles) the tripped boundary layer should be more robust to separation and delay a sharp increase in drag due to stall.
Of course if some other part of the tyre/wheel trips the flow further aft anyway, then drag may always be higher for the tripped tyre, but I don't think your comments about flow separation are correct. This is just based on the underlying aerodynamics. I don't have any direct experience with tyres/wheels.

Sorry, you're right and I've sloppily misused the word "trip." The edge of the tread doesn't trip the flow in terms of boundary layer transition, but it may disrupt the flow. And in the adverse pressure gradient on the leeward side of the tire, this may lead to the earlier separation seen on some tires than on otherwise similar tires with a smother tread edge. We can often see earlier stall and the characteristic increase in drag.

Funny how that worked out! Such a small world, eh?

Fixed it for you :-)

---

http://bikeblather.blogspot.com/

I'm curious how much of that observation about "open tubular" style constructed tires is due to the "lip" ("Don't you give me no lip!" ;-), and how much is due to the naturally rounder leading edge shape that a very flexible casing with a thin glued-on tread will take...especially as compared to some of the "tunnel queen"-type tires like the GP4000S that have a decidedly parabolic profile molded into the tread area?

Yep, that and tread pattern are the other obvious differences. To quote Chuck Zimmer, a former collegue of mine at GKN Aerospace, "As usual Damon, it's more than one thing!"

So I've not fully followed this thread, but are we saying the gpTT beats out the supersonic? Especially when new?
What size is this for? Currently I have 23 supersonics but ALL my races this year are hilly on rubbish roads, so considering the 25mm gps or this is an aero mistake?
In zipp 404 FC

I just realized I have data that might shed some light on that...


The 24C and 26C of the SWT and TC tires measured within 0.2-0.4mm (24TC 0.2mm wider than 24SWT, 26SWT 0.4mm wider than 26TC) on the same rim width wise. The center tread area and "hatching" on the edges are the same basic pattern/shape (one "inconsistency" is that the TCs both appear to use the same tread mold, whereas the SWT molds appear to be "scaled" in the tread area).

The SWTs are thin enough tread that one would expect them to take a fairly round shape...but, it does appear that the TCs start stalling earlier somewhere between 5 and 10 degrees of yaw.

So...I guess it is mostly the "lip".

It would be interesting to see the results of the Flo-style rim shape optimization that used something like the TC as the tire baseline. I wonder how much different the resulting shape would be, and would it be faster than something designed around a GP4000S with the TC mounted?

I'm not sure it's clear. If you look at Tom's test spreadsheet, you can see that different generations (or individual tires) of the same make and model perform very differently when it comes to CRR. The 20C Supersonic, for example, goes from .0034 in 2012 to .0030 in 2016.

I have a 23C Supersonic on order. If the rubber and construction is the same as for its 20C brother, my guess is it will best the TT by a watt or two in CRR. As far as the aero goes, I doubt you can conclude much without testing specific tires on the specific rims you are using.

am i missing it or is the pressure data not there or maybe unimportant? do you have the "breakeven" point for where impedence takes over? or whatever it was in the silca data.

trying to figure out best pressures for me on conti 23 TT on hed jet + rims (i'm 165 lbs).

Gotcha, thanks. I haven't measured their width, but at 90psi they were just slightly wider than the 25mm external of the jet +. (where I ran them at my first race on this setup over the weekend - on smooth concrete)

So for rougher surfaces I'll go more toward 85. How low would you think would be too low?

still contemplating switching out the gp4000s for the gpTT but just wanted to know how, if anyone, is getting along with them. Are they puncture magnets? The 4000s have been kind to me re: punctures, it makes me nervous going for something else now!

Gotcha, thanks. I haven't measured their width, but at 90psi they were just slightly wider than the 25mm external of the jet +. (where I ran them at my first race on this setup over the weekend - on smooth concrete)

So for rougher surfaces I'll go more toward 85. How low would you think would be too low?

For those who ride over cattle guards either at the critical speed, this is a real effect and exactly emulates the ramp model. However, since road roughness is random and far smaller than the compliance of the tire, this scenario is unreal and does not occur. Tire deflection does not go to zero with high inflation. I have gotten snake bites with maximum safe inflation pressure on rough dirt roads. This is evidence of how much compliance a tire has even when inflated to these theoretical retarding pressures. It doesn't happen!
...Yes, any singular feature that causes lift-off has a retarding effect if there is not a series of randomly spaced similar ones on whose backside the tire lands as often as it lifts off. This occurs on an adversely ordered surface, such as a cattle guard or a series of botts dots. However, a tire that is run at lower inflation absorbs energy all the time including the larger bumps that it cannot entirely absorb anyway. Jim Papadopoulos has argued for lower inflation at great length ins this subject here on the net. Having ridden many miles on pave' and cobbles, I am convinced that although it may not be comfortable, high tire pressure is faster on even such rough surfaces.

still contemplating switching out the gp4000s for the gpTT but just wanted to know how, if anyone, is getting along with them. Are they puncture magnets? The 4000s have been kind to me re: punctures, it makes me nervous going for something else now!

I hope to do some more testing on rough surfaces. But the testing I did a few years ago never supported the ultra-low pressures that seem to be in vogue today. In fact, I determined that I was best off running 70+ psi for my Mtb hill-climb races on rocky fire-roads! Take my word for it, I tested that a lot.

Likewise, Alan Morrison's tests showed that higher pressures decreased Crr all the way to 140 PSI, even when he simulated a rough surface on the rollers. If you look at the photos for the BRR site, you'll see his roller surface isn't exactly smooth either. And every single one of his tests show steadily decreasing Crr with higher pressures (up to 120 psi, at least).

We can go all the way back to Jobst Brandt, who found the same thing. Here's a blast from the past from a guy who's an asshole, but who tested more tires than any of us and definitely knows his stuff. He nicely refutes the absurd Zipp contention about your whole bicycle lifting up as it goes over roughness:

Josh Poertner did a great test confirming and illustrating this effect recently with Silca. You can find that here: https://silca.cc/...y-and-previous-works
https://silca.cc/...stance-and-impedance

In actuality, what I did was hold the CdA "fixed"..... and I then varied the tire pressures.

Tom, I realize challenging you on this subject is a little like you challenging me on the 9th century writings of al-Jahiz. But that's not going to stop me! ;-)

I note first that Josh's write-up begins with precisely the lift-off scenario that is so absurd. The pebbles in chipseal are 1/4 or 3/8 inch, with the protruding edge typically being a fraction of that. So we're talking PSI in the thousands for one of these. Rubber ain't that hard. Do you remember polyurethane skateboard wheels? They're completely solid and higher on the durometer scale than bike tire rubber. Yet even those can ride over pebbles and what not and absorb the roughness.

In your article you write:




Now, just a few days ago, you and others asserted that the minuscule lip on open tubular tires made a significant aerodynamic difference. I just just measured a tire at 22.5mm with 100psi, then inflated it to 130 psi and measured it at 23.35mm. So let me ask: are you sure you held CdA "fixed"?

i have placed my tire comments on the front page. i expect and, i guess, in a twisted way hope, to catch a lot of grief here. (what's wrong with me?)

there's obviously a lot more to write that i didn't write i the spirit of brevity, and because i just don't yet have the secret tire prescriber algorithm:

inputs:

- wheel of choice
- front or rear
- road texture

outputs:

- tire model
- tire width
- tire pressure

it's all fascinating! i'm eager to see how this ends up.

it was the right tire, right price, right durability, right time in history, right distributor selling it, right people noticing the value of it and describing the value in factual terms that made compelling sense in all places that mattered.

"They've got to come with data now."

you mean the other tire companies? yes. but i think you, al, and jarno are the people who do that, aren't you? conti does GREAT with its own data, certainly, but wouldn't you agree that prior to black chili the conti tires were aero, but not overwhelmingly great rollers?

now we do have some tires that outroll the 4000S II. but they have their own hurdles. price. distribution. and no aero data that i know of. but jarno has pretty compelling data that makes for a good beginning.

mind, i don't think people ought to abandon conti. i just think that in the 4 years since that tire has come out the gap seems to have closed in performance if not yet in price.

I don't think "perhaps" is the right word ;-)

Bringing up an old thread instead of starting a new one...

I've followed the discussion with interest as I've recently bought a pair of Flo 90/60 carbon clinchers and am just decided what would be the best tyre combo to fit them with for riding a Cervelo P3C.

I've used Conti GP TT 23mm in the past and plan on sticking with this tyre (with latex tubes of course).
Thinking of going with a 25mm on the rear for better rolling resistance, handling and comfort (the rear tyre is well hidden on the P3C behind the seatstay so aero loss is reduced). Is there any advantage of going with a 25mm on the front or should I stick with a 23mm which would be marginally more aero?