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Bicycle Rolling Resistance Continental GP 5000 Test Is Up
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You can read it here: https://www.bicyclerollingresistance.com/...grand-prix-5000-2018
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [GreenPlease] [ In reply to ]
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Thomas Gerlach] [ In reply to ]
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Thomas Gerlach wrote:
Stumbled upon that last night. Hopefully he will get the GP 5000 TL data up soon as well. AeroCoach also published some data here and included the 5000 (23 & 25), TL (25), 4000, and TT



Hmmm...the aerocoach data shows the 23C versions of the GP5K vs. GP4K2 to be ~13% faster...which matches what Conti said...while the 25C GP5K is 20% faster than the 23C GP4K. Since all are tested at 90 psi, that makes sense. BTW, I calculate that if the 23C is tested at 90 psi, then the 25C tires should be inflated to 80 psi for an "apples to apples" comparison. The 18% better rolling for the 25C version comparison (GP5K vs. GP4K2) as reported by BRR seems a bit "off"...

Of course, the same is true with the BRR data in regards to pressure. His ranking is all with tires inflated to 120 psi regardless of size. To be fair, that's how my own testing is reported, but I'm about ready to "freeze" that data set and start reporting only with the tires inflated to the "Berto 15% Drop" calculated pressure based on actual measured width.

I have a hard time believing the GP5K would be faster rolling than a Turbo Cotton...



http://bikeblather.blogspot.com/
Last edited by: Tom A.: Dec 5, 18 16:50
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [GreenPlease] [ In reply to ]
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On my Christmas list. I absolutely love my GP4K2 25 tires on my road bike. But they are a little long in the tooth now. Time for an upgrade.
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Tom A.] [ In reply to ]
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Tom A. wrote:
Thomas Gerlach wrote:
Stumbled upon that last night. Hopefully he will get the GP 5000 TL data up soon as well. AeroCoach also published some data here and included the 5000 (23 & 25), TL (25), 4000, and TT



Hmmm...the aerocoach data shows the 23C versions of the GP5K vs. GP4K2 to be ~13% faster...which matches what Conti said...while the 25C GP5K is 20% faster than the 23C GP4K. Since all are tested at 90 psi, that makes sense. BTW, I calculate that if the 23C is tested at 90 psi, then the 25C tires should be inflated to 80 psi for an "apples to apples" comparison. The 18% better rolling for the 25C version comparison (GP5K vs. GP4K2) as reported by BRR seems a bit "off"...

Of course, the same is true with the BRR data in regards to pressure. His ranking is all with tires inflated to 120 psi regardless of size. To be fair, that's how my own testing is reported, but I'm about ready to "freeze" that data set and start reporting only with the tires inflated to the "Berto 15% Drop" calculated pressure based on actual measured width.

I have a hard time believing the GP5K would be faster rolling than a Turbo Cotton...

This is what I love about you Tom. Hopefully BRR and Aerocoach choose the method they do for simplicity only and not just because they lack that thought. Aero testing should also be done with proper PSI and scale it appropriately.


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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [GreenPlease] [ In reply to ]
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Wow, and that test is with a butyl tube. Swap for latex and it might be in Corsa Speed territory
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Tom A.] [ In reply to ]
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Tom A. wrote:
Thomas Gerlach wrote:
Stumbled upon that last night. Hopefully he will get the GP 5000 TL data up soon as well. AeroCoach also published some data here and included the 5000 (23 & 25), TL (25), 4000, and TT



Hmmm...the aerocoach data shows the 23C versions of the GP5K vs. GP4K2 to be ~13% faster...which matches what Conti said...while the 25C GP5K is 20% faster than the 23C GP4K. Since all are tested at 90 psi, that makes sense. BTW, I calculate that if the 23C is tested at 90 psi, then the 25C tires should be inflated to 80 psi for an "apples to apples" comparison. The 18% better rolling for the 25C version comparison (GP5K vs. GP4K2) as reported by BRR seems a bit "off"...

Of course, the same is true with the BRR data in regards to pressure. His ranking is all with tires inflated to 120 psi regardless of size. To be fair, that's how my own testing is reported, but I'm about ready to "freeze" that data set and start reporting only with the tires inflated to the "Berto 15% Drop" calculated pressure based on actual measured width.

I have a hard time believing the GP5K would be faster rolling than a Turbo Cotton...

I look forward to the drop data. As an aside, I recently made a copy of your CRR spreadsheet and I've been working away at a "revised" version with estimates that normalize around size/pressure/casing tension. It's imperfect but, as you'd expect, wider tires become slower and narrower tires become faster. I'll be curious to see how my estimates correspond to your "15% drop" data.

Re TC: compound improvements are a beautiful thing :) I want to believe...
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [BigBoyND] [ In reply to ]
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BigBoyND wrote:
Wow, and that test is with a butyl tube. Swap for latex and it might be in Corsa Speed territory

Exactly :) IMO, it's a pretty safe bet that the GP5000 is a more aero tire too so on combined aero/crr it appears to be the new king of the hill.
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Thomas Gerlach] [ In reply to ]
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Thomas Gerlach wrote:
This is what I love about you Tom. Hopefully BRR and Aerocoach choose the method they do for simplicity only and not just because they lack that thought. Aero testing should also be done with proper PSI and scale it appropriately.

Alas, I strongly suspect the whole "wider is faster" marketing machine is based on an incorrect understanding of CRR. Most of the tests that have filled the pages of BikeRadar, BikeRumor, etc. have shown wider tires tested at the same air pressure as their narrower brethren. Amazingly, the reviewers then often go on to say that the wider tires felt "more supple."


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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [GreenPlease] [ In reply to ]
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GreenPlease wrote:
BigBoyND wrote:
Wow, and that test is with a butyl tube. Swap for latex and it might be in Corsa Speed territory


Exactly :) IMO, it's a pretty safe bet that the GP5000 is a more aero tire too so on combined aero/crr it appears to be the new king of the hill.

I'm not buying that result...yet...seems to be a bit of an "outlier", even as compared to Conti's claims.



http://bikeblather.blogspot.com/
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [BigBoyND] [ In reply to ]
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BigBoyND wrote:
Wow, and that test is with a butyl tube. Swap for latex and it might be in Corsa Speed territory

The corsa speed test on the BRR website is a 23mm. The TT and new GP5k is a 25mm on the site. If you adjust for casing tension, the gap between the GP5k and CS is larger than what is shown on the BRR site. A latex tube is going to help it but I wouldn't call it CS territory.

get comfortable being uncomfortable
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Tom A.] [ In reply to ]
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Tom A. wrote:
Thomas Gerlach wrote:
Stumbled upon that last night. Hopefully he will get the GP 5000 TL data up soon as well. AeroCoach also published some data here and included the 5000 (23 & 25), TL (25), 4000, and TT



Hmmm...the aerocoach data shows the 23C versions of the GP5K vs. GP4K2 to be ~13% faster...which matches what Conti said...while the 25C GP5K is 20% faster than the 23C GP4K. Since all are tested at 90 psi, that makes sense. BTW, I calculate that if the 23C is tested at 90 psi, then the 25C tires should be inflated to 80 psi for an "apples to apples" comparison. The 18% better rolling for the 25C version comparison (GP5K vs. GP4K2) as reported by BRR seems a bit "off"...

Of course, the same is true with the BRR data in regards to pressure. His ranking is all with tires inflated to 120 psi regardless of size. To be fair, that's how my own testing is reported, but I'm about ready to "freeze" that data set and start reporting only with the tires inflated to the "Berto 15% Drop" calculated pressure based on actual measured width.

I have a hard time believing the GP5K would be faster rolling than a Turbo Cotton...

I think that would be a great idea. It would make it easier for us nerds to see which tyre is fastest and make it educational for the more novice users :)

As an aside, am I the only one that would love to see sub-23mm tubeless tyres? Perhaps the biggest benefit with tubeless for me would be the increased pinch flat protection, but I'm not willing to run 27+mm tyres (especially on the front - and yes, a stated 23mm tyre measures 27+mm on my Jet 9 Black rim). A narrower tubeless tyre would help with one of the qualms of running narrower tyres, i.e. pinch flats. Not holding my breath any manufacturer is coming out with one, though.
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [stevej] [ In reply to ]
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not to mention a CS with a latex tube would be faster still... unless they tested it with a latex for some reason

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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [ericMPro] [ In reply to ]
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ericMPro wrote:
not to mention a CS with a latex tube would be faster still... unless they tested it with a latex for some reason

He (Jarno at BRR) actually tested it set up tubeless (with sealant)...so, basically the same as if it had a latex tube inside.



http://bikeblather.blogspot.com/
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Tom A.] [ In reply to ]
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Tom A. wrote:
BTW, I calculate that if the 23C is tested at 90 psi, then the 25C tires should be inflated to 80 psi for an "apples to apples" comparison.

I'm not so sure. People do generally run lower pressure with wider tires, but that isn't because they need to. It's because they value comfort. And on a real road they might be at the part of the curve where the low pressure is actually better (lower Crr)... as opposed to the roller where Crr always drops as pressure increases. I can see it either way, but I think using the same pressure for all tires is better for roller testing. The Crr improvement is a real advantage of bigger tires. The spring rate of the tire is controlled by pressure also, so you are normalizing that aspect by running them all at the same PSI.
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [GreenPlease] [ In reply to ]
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I'll probably pick up a pair to race with next year and see how it goes. I still have a pretty large stock of GP4000S2's that I'll train on given the slightly better puncture protection.

I figured it was too good to be true to claim lower weight, better CRR, and better puncture resistance. But overall looks like a good tire.
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [GreenPlease] [ In reply to ]
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GreenPlease wrote:
Alas, I strongly suspect the whole "wider is faster" marketing machine is based on an incorrect understanding of CRR.

Only because they are ignoring aero. Wide tires really do have better Crr.

I'll illustrate why I think roller testing at the same psi makes more sense. Say you have 20mm, 23mm, and 25mm models of the same tire. At the same psi they will all have the same spring rate. This is from both Damon Rinard and Josh Poertner. So the ride compliance will be about the same. If that is your normalizing factor, then the wide tire is better for Crr. The wider tire gives you additional advantages if the road is rough or you are in danger of potholes or rocks that could result in a pinch flat. In addition you *can* run the wide tire at lower PSI, if you desire more ride compliance, or the road is so rough that lower psi is a Crr benefit. With small tires you don't have that option.

Testing at different pressures on the rollers is a poor comparison IMO.
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [rruff] [ In reply to ]
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rruff wrote:
Tom A. wrote:
BTW, I calculate that if the 23C is tested at 90 psi, then the 25C tires should be inflated to 80 psi for an "apples to apples" comparison.


I'm not so sure. People do generally run lower pressure with wider tires, but that isn't because they need to. It's because they value comfort. And on a real road they might be at the part of the curve where the low pressure is actually better (lower Crr)... as opposed to the roller where Crr always drops as pressure increases. I can see it either way, but I think using the same pressure for all tires is better for roller testing. The Crr improvement is a real advantage of bigger tires. The spring rate of the tire is controlled by pressure also, so you are normalizing that aspect by running them all at the same PSI.

The spring rate of the tire is determined by BOTH the air pressure AND the casing tension. For a given pressure, increasing tire width increases the casing tension portion. Normalizing for casing tension is a better approach IMHO (in both testing and "real life")...a wider tire ridden at the same pressure as a narrower tire will have a higher "spring rate". IIRC, Damon's tire deflection data showed that.



http://bikeblather.blogspot.com/
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Tom A.] [ In reply to ]
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Tom A. wrote:
The spring rate of the tire is determined by BOTH the air pressure AND the casing tension. For a given pressure, increasing tire width increases the casing tension portion. Normalizing for casing tension is a better approach IMHO (in both testing and "real life")...a wider tire ridden at the same pressure as a narrower tire will have a higher "spring rate". IIRC, Damon's tire deflection data showed that.

I'm out the door now, but I'm pretty certain that both of those guys reported that the spring rate was a very close function of pressure only and size independent... same tire model of course.
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [rruff] [ In reply to ]
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [rruff] [ In reply to ]
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rruff wrote:
Tom A. wrote:
The spring rate of the tire is determined by BOTH the air pressure AND the casing tension. For a given pressure, increasing tire width increases the casing tension portion. Normalizing for casing tension is a better approach IMHO (in both testing and "real life")...a wider tire ridden at the same pressure as a narrower tire will have a higher "spring rate". IIRC, Damon's tire deflection data showed that.


I'm out the door now, but I'm pretty certain that both of those guys reported that the spring rate was a very close function of pressure only and size independent... same tire model of course.

Mostly determined by air pressure, but casing tension has an effect. It's tough to see in Damon's charts, but here's one from Josh's blog post on the subject (https://silca.cc/...r-is-stiffer-harsher):





Looks like increasing spring rate with tire width for the same pressure to me ;-)

Of course, it also depends on the shape of the object impacting the tire. The above charts are for a flat surface contacting the tire. If you look at the blog post linked above, when the object is reduced to an 8mm anvil (to simulate a curb edge) then the spread with tire size decreases, and the effect is nearly completely in relation to air pressure.





http://bikeblather.blogspot.com/
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [rruff] [ In reply to ]
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rruff wrote:
Tom A. wrote:
The spring rate of the tire is determined by BOTH the air pressure AND the casing tension. For a given pressure, increasing tire width increases the casing tension portion. Normalizing for casing tension is a better approach IMHO (in both testing and "real life")...a wider tire ridden at the same pressure as a narrower tire will have a higher "spring rate". IIRC, Damon's tire deflection data showed that.

I'm out the door now, but I'm pretty certain that both of those guys reported that the spring rate was a very close function of pressure only and size independent... same tire model of course.

To take things to an extreme, try putting 75psi in a 2.2” MTB tire and compare it to 75psi in a 28mm road tire ;) the ride will be far far harsher on the former and that’s because of the higher spring rate.

(Don’t actually try this, the MTB tire will probably blow off the rim.)
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Tom A.] [ In reply to ]
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Tom A. wrote:
Of course, it also depends on the shape of the object impacting the tire. The above charts are for a flat surface contacting the tire. If you look at the blog post linked above, when the object is reduced to an 8mm anvil (to simulate a curb edge) then the spread with tire size decreases, and the effect is nearly completely in relation to air pressure.


^^^^This.

That's why I was left with the impression that comfort was dominated by pressure, and size was irrelevant. This is true for the irregularities we typically encounter on the road.

I still think if you want to normalize the Crr results to something, comfort (ie pressure) is the best thing to use. At equivalent pressure, the larger tire will have lower Crr as well as greater pothole survivablity. If you use the sink % then the survivability will be about the same between large and small but the larger tire will be more comfortable. It may or may not still have lower Crr (on rollers). But then it gets murkier when you try to translate roller data to road, where the bigger tire at lower pressure will improve relative to the small tire at higher pressure.
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [rruff] [ In reply to ]
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rruff wrote:
Tom A. wrote:
Of course, it also depends on the shape of the object impacting the tire. The above charts are for a flat surface contacting the tire. If you look at the blog post linked above, when the object is reduced to an 8mm anvil (to simulate a curb edge) then the spread with tire size decreases, and the effect is nearly completely in relation to air pressure.



^^^^This.

That's why I was left with the impression that comfort was dominated by pressure, and size was irrelevant. This is true for the irregularities we typically encounter on the road.

I still think if you want to normalize the Crr results to something, comfort (ie pressure) is the best thing to use. At equivalent pressure, the larger tire will have lower Crr as well as greater pothole survivablity. If you use the sink % then the survivability will be about the same between large and small but the larger tire will be more comfortable. It may or may not still have lower Crr (on rollers). But then it gets murkier when you try to translate roller data to road, where the bigger tire at lower pressure will improve relative to the small tire at higher pressure.

Actually...it'll still have more distance before bottoming.

Also, running lower pressure makes it less likely you'll end up over the "breakpoint" for you particular load and whatever road roughness you happen to encounter.

So, if you bring in the better comfort factor...that's a plus, plus, and a plus. The only possibly downside is a slightly higher Crr, but the test data shows us that it takes a LOT of pressure drop to significantly affect that:




http://bikeblather.blogspot.com/
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Re: Bicycle Rolling Resistance Continental GP 5000 Test Is Up [Tom A.] [ In reply to ]
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The only possibly downside is a slightly higher Crr, but the test data shows us that it takes a LOT of pressure drop to significantly affect that...

I read a couple of articles that stated that rider perception when it came to tire pressure was very inaccurate (i.e. the rider always said the higher pressure tire was faster when in fact the opposite was true). That got me thinking about the feel of the tires I've been riding (G-One Speed at 48mm up front/G-One Allround at 36mm in back/both at 22-26 psi) and how the lower pressure tires feel slower but more comfortable. I tested them on a steep hill with fairly good pavement at 25 and 65 psi and I came out within a second or two of the same time. I've repeated the gist of that test on several more occasions, even comparing them to a GP4000s at 90 psi and there does not seem to be any disadvantage to riding them at 25psi, even on the road.
The biggest dilemma that this creates is what to do with my custom Mandaric road bike that can maybe handled a 28mm tire. I tend to ride my cheap Diamondback converted hybrid gravel bike all the time now and I don't like going back to 23 or 25mm tires.
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