The foolish inconsistency of Continental tires (Plus Vittoria CS 25C)

Jun 25, 18 23:42

Post #1 of 34 (7577 views)

Some roller test fun today.

Continental Grand Prix GP4000 S II 25C: .00343 (50 miles wear)
Continental Grand Prix GP4000 RS II 25C: .00343 (new)
Continental Grand Prix GP4000 S II 23C: .00343 (new)
Continental Supersonic 20C: .00270 (new)
Continental Supersonic 20C: .00253 (200 miles wear)
Continental Supersonic 23C: .00279 (new)
Vittoria Corsa Speed Pista 23C: .00262 (100 miles wear)
Vittoria Corsa Speed 25C: .00241 (new)

The surprises are that the vaunted GP RS is no faster than the normal model. And the 23C GP rolls just as fast as the 25C GP tires.

What's more surprising is that the 23C Supersonic is actually a bit slower than the 20C version. In fact, my worn SS 20C is one of the fastest tires I've ever tested. Why is it so much faster than the new SS 20C? The wear? Continental's inconsistency? I'm not sure.

For Vittoria, wider is definitely faster. The 25C Corsa speed tire is worth around 2 watts over the 23C. I think lanierb only got a 1 watt difference. In a previous test, I got 1.6 watts.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 3:00

Post #2 of 34 (7457 views)

What pressures did you run on each tire? Did you account for casing tension?

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 3:12

Post #3 of 34 (7446 views)

Did you run them with the mold release still on them or run them enough to be clean?

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 4:16

Post #4 of 34 (7386 views)

Which digit is significant in your measurement system?

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 4:26

Post #5 of 34 (7369 views)

Jens, for those of us who don't understand the fractions, is there a chance you can convert to rough wattage for two tires for a 160 lbs rider with 20 lbs of body, helmet, shoes, clothing @ 40 kph @ 90 psi (or whatever you used)

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 4:50

Post #6 of 34 (7321 views)

Interesting data, thanks for posting!

jens wrote:

The surprises are that the vaunted GP RS is no faster than the normal model.

So that would suggest that tread depth isn't such an important factor in determining Crr, compared to say compound choice or casing construction?

Trying to sell less tyre for more money was always going to require some creative marketing from Conti!

I'm a big fan of the Continental GP TT, can I ask why you prefer the Supersonics instead?

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 6:19

Post #7 of 34 (7218 views)

thanks for sharing

I expected better from the pista

My Blog - http://leegoocrap.blogspot.com

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [stevej] [ In reply to ]

Jun 26, 18 9:07

Post #8 of 34 (7066 views)

stevej wrote:

What pressures did you run on each tire? Did you account for casing tension?

Forgot to mention that. I ran all of them at 100psi.

lyrrad wrote:

Did you run them with the mold release still on them or run them enough to be clean?

This was a 2nd run for all of them, so most of them had little or no stuff hanging off.

marklemcd wrote:

Which digit is significant in your measurement system?

Hell, I don't know. I use a Powertap, which only has 1 watt increments, for values that range 40-70 watts. My experience has been that these results are repeatable to the 4th digit, which corresponds to a 1 watt

devashish_paul wrote:

Jens, for those of us who don't understand the fractions, is there a chance you can convert to rough wattage for two tires for a 160 lbs rider with 20 lbs of body, helmet, shoes, clothing @ 40 kph @ 90 psi (or whatever you used)

My rule of thumb is that the 4th digit corresponds to 1 watt (per pair of tires) for a 150 lb rider riding at TT speeds (25-30mph). So, for example, the difference between the GP4000 25C: (.00343) and the Corsa Speed 25C (.00241) is going to be about 10 watts. (I'm so glad you're up for pondering things like Crr! ;-))

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 9:19

Post #9 of 34 (7050 views)

what wheel were you using?

Dan Empfield
aka Slowman

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 10:08

Post #10 of 34 (6984 views)

jens wrote:

For Vittoria, wider is definitely faster. The 25C Corsa speed tire is worth around 2 watts over the 23C. I think lanierb only got a 1 watt difference. In a previous test, I got 1.6 watts.

Thanks for the test info Jens. Just to recap: I got 2 watts difference when both were run at 100psi (actually slightly over 2 watts). I got 1 watt difference when the 23 was at 100psi and the 25 was at 90psi, which I kind of feel is a more realistic comparison.

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [Slowman] [ In reply to ]

Jun 26, 18 10:48

Post #11 of 34 (6931 views)

Slowman wrote:

what wheel were you using?

Velocity A23 with Powertap hub. It has inside/outside width of 23 and 18. So it's a pretty fair match to typical contemporary race wheels.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 11:01

Post #12 of 34 (6892 views)

isn't the corsa speed a tubeless? did you rerig the velocity tubeless for the test?

Dan Empfield
aka Slowman

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [Slowman] [ In reply to ]

Jun 26, 18 11:04

Post #13 of 34 (6880 views)

Slowman wrote:

isn't the corsa speed a tubeless? did you rerig the velocity tubeless for the test?

it's tubeless ready, so it can be set up either way

--------------------------------------------
TEAM F3 Undurance

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [Slowman] [ In reply to ]

Jun 26, 18 11:06

Post #14 of 34 (6878 views)

Slowman wrote:

isn't the corsa speed a tubeless? did you rerig the velocity tubeless for the test?

There's no need to run it tubeless for the test. They test the same set up tubeless or with a latex tube inside. See: http://bikeblather.blogspot.com/...corsa-speed-tlr.html

In fact, you don't need to run them tubeless at all. My Jet 6+ Blacks both have 23C Corsa Speeds and latex tubes on them right now for riding/racing...

http://bikeblather.blogspot.com/

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [Multisportsdad] [ In reply to ]

Jun 26, 18 11:07

Post #15 of 34 (6874 views)

Multisportsdad wrote:

Slowman wrote:

isn't the corsa speed a tubeless? did you rerig the velocity tubeless for the test?

it's tubeless ready, so it can be set up either way

right. that's what i'm asking. was it set up tubeless specifically for this tire? or was this tire ridden with a tube? because it does take a little work to ride the other tires tubed, and then (unless this wheel is set up with tubeless tape) to tape it and install a tubeless valve just for the vittoria. i guess i'd like to know that and i assume that the other tires were ridden with latex tubes.

Dan Empfield
aka Slowman

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 13:34

Post #16 of 34 (6732 views)

jens wrote:

What's more surprising is that the 23C Supersonic is actually a bit slower than the 20C version. In fact, my worn SS 20C is one of the fastest tires I've ever tested. Why is it so much faster than the new SS 20C? The wear? Continental's inconsistency? I'm not sure.

Thanks for the info Jens!

A few people have gotten mediocre Crr for the SS23... about the same as the GPTT or slightly worse. It also reportedly weighs about the same (~175g). I wonder if Conti got lazy and is using the GPTT casing for the 23.

It's normal for Crr to drop an appreciable amount after the tires been run a few miles (like maybe 50 or so?). I don't know the reason, but 5-10% is about right.

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 13:47

Post #17 of 34 (6699 views)

That must be a sensational title because according to you stats used tires are faster for the same model right? Makes sense since new rubber is probably less morphable initially

Is this tested with wheels loaded with rider weight or pure rolling resistance ? is it a average or a few tries, if so what was the range within repeats?

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [lacticturkey] [ In reply to ]

Jun 26, 18 14:34

Post #18 of 34 (6638 views)

lacticturkey wrote:

That must be a sensational title because according to you stats used tires are faster for the same model right? Makes sense since new rubber is probably less morphable initially

Well the Emerson quote is "foolish consistency" which Conti definitely does not have.

lacticturkey wrote:

Is this tested with wheels loaded with rider weight or pure rolling resistance ? is it a average or a few tries, if so what was the range within repeats?

This is (partial) rider weight on rear rollers (front fork fixed). I usually do a couple of tries. It is unusual for me to see more than 1 watt (out of 40-70) difference between runs of the same tire. Usually they're quite consistent. I did throw out one entire set of results because the horizontal dropout screws were not precisely aligned. But surprisingly, the follow-up showed little difference.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [Slowman] [ In reply to ]

Jun 26, 18 14:34

Post #19 of 34 (6638 views)

Slowman wrote:

right. that's what i'm asking. was it set up tubeless specifically for this tire? or was this tire ridden with a tube? because it does take a little work to ride the other tires tubed, and then (unless this wheel is set up with tubeless tape) to tape it and install a tubeless valve just for the vittoria. i guess i'd like to know that and i assume that the other tires were ridden with latex tubes.

My tests are mostly self-serving (unlike Tom's and some of the actual scientists' here). I only run tires with latex tubes, so that's the only way I test them.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 15:27

Post #20 of 34 (6590 views)

Nice. Thanks for sharing the test results.

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 26, 18 16:58

Post #21 of 34 (6540 views)

Did you measure the actual mounted width of the tires on the A23 rim?

David T-D
http://www.tilburydavis.com

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 28, 18 16:05

Post #22 of 34 (6236 views)

jens wrote:

stevej wrote:

What pressures did you run on each tire? Did you account for casing tension?

Forgot to mention that. I ran all of them at 100psi.

lyrrad wrote:

Did you run them with the mold release still on them or run them enough to be clean?

This was a 2nd run for all of them, so most of them had little or no stuff hanging off.

marklemcd wrote:

Which digit is significant in your measurement system?

Hell, I don't know. I use a Powertap, which only has 1 watt increments, for values that range 40-70 watts. My experience has been that these results are repeatable to the 4th digit, which corresponds to a 1 watt

devashish_paul wrote:

Jens, for those of us who don't understand the fractions, is there a chance you can convert to rough wattage for two tires for a 160 lbs rider with 20 lbs of body, helmet, shoes, clothing @ 40 kph @ 90 psi (or whatever you used)

My rule of thumb is that the 4th digit corresponds to 1 watt (per pair of tires) for a 150 lb rider riding at TT speeds (25-30mph). So, for example, the difference between the GP4000 25C: (.00343) and the Corsa Speed 25C (.00241) is going to be about 10 watts. (I'm so glad you're up for pondering things like Crr! ;-))

Thanks for the rule of thumb. This helps understanding. Does the Crr change at all with speed between say 20 mph and around 33 mph (headwind vs tailwind or alight downhill).

Hey if you are not riding you want to virtually rode with those who are. On a plus note I have been able to get on the CT on day 5 and day 6 and do 4x5 min and 3x5 min respectively. While I cannot YET properly look at a school bus, a climb of Galibier in 2019 is still a target... Crr calculations for 6 mph will be needed for that LoL

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [devashish_paul] [ In reply to ]

Jun 29, 18 4:35

Post #23 of 34 (6109 views)

devashish_paul wrote:

Thanks for the rule of thumb. This helps understanding. Does the Crr change at all with speed between say 20 mph and around 33 mph (headwind vs tailwind or alight downhill).

To be a little pedantic, Crr doesn't change at all -- it's a dimensionless coefficient. The rolling resistance increases in a linear fashion based on weight, Crr and speed. So if you go 50% faster, rolling resistance will be 50% greater.

So here are some rough numbers with a fast tire (.0028 Crr): rolling resistance at 20mph is ~20 watts. At 30mph it will be ~30 watts. With a slower tire (.004 Crr), it would go from 28 watts to 42.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [jens] [ In reply to ]

Jun 29, 18 5:56

Post #24 of 34 (6051 views)

jens wrote:

devashish_paul wrote:

Thanks for the rule of thumb. This helps understanding. Does the Crr change at all with speed between say 20 mph and around 33 mph (headwind vs tailwind or alight downhill).

To be a little pedantic, Crr doesn't change at all -- it's a dimensionless coefficient. The rolling resistance increases in a linear fashion based on weight, Crr and speed. So if you go 50% faster, rolling resistance will be 50% greater.

So here are some rough numbers with a fast tire (.0028 Crr): rolling resistance at 20mph is ~20 watts. At 30mph it will be ~30 watts. With a slower tire (.004 Crr), it would go from 28 watts to 42.

So that's why if the grade is steep enough and you go slow enough rolling resistance and air resistance trends towards nothing and you can almost get an approx of your FTP power by taking mgh/time, where mass is all mass of bike+rider+gear, h is vertical displacement, g is 9.8m/s^^2.

Re: The foolish inconsistency of Continental tires (Plus Vittoria CS 25C) [devashish_paul] [ In reply to ]

Jun 29, 18 10:07

Post #25 of 34 (5957 views)

devashish_paul wrote:

So that's why if the grade is steep enough and you go slow enough rolling resistance and air resistance trends towards nothing and you can almost get an approx of your FTP power by taking mgh/time, where mass is all mass of bike+rider+gear, h is vertical displacement, g is 9.8m/s^^2.

It's also why, at some very high speed, an aero, but slow-rolling tire like the Conti GP will actually outperform an un-aero, but fast rolling tire like the Corsa Speed.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

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