23mm tire testing faster compared to a bunch of 25mm tires? Shocking......

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Alex Arman

Strava

I don't think that's what interesting in the article. Actually I would look at it the opposite way, there is not a big aero loss in between the GP4000S II 700x23 (which is a very BIG 23) and the new GP5000 700x25 (which is a SMALL 25). And the GP5000 is faster in RR so very likely faster overall. Anyway, I thought that article was pretty good but you don't have to read it if you have your conclusion all set already...

That's cool, looks like a good test, but they didn't test any of the tires I'd actually use on a front wheel.

Lol.... The fastest tire was 23c and everything else was 25c. Shocker.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

The question is what is the savings for better RR? I remember an older post on this and the answer was from Zipp. That tire testing from 23mm-25mm RR was a .08w difference to the good for the 25mm but up to a 6w aero disadvantage based on wind yaw.

It seems to me, and I could be wrong, that you should go with the tire that the wheel was develop for and that the latest and greatest tire may not be the fastest for your wheel? Now If I knew what tire was used to develop a Zipp 808 FC I would be set.

yes, it would be interesting to see the same test with a roval clx-64
the turbo cotton does so badly in that test but might be different on roval wheels

Various people on here have measured the 23 GP4000 at closer to 25 (24.8?) depending on the rim. IIRC the 5000 measures truer to size.

Maurice

Almost all tires measure wider than their specification on modern rims. All those 25C tires measure wider than 25 when mounted up.

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Ed O'Malley
www.VeloVetta.com
Founder of VeloVetta Cycling Shoes
Instagram • Facebook

new-old Continental Supersonic

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Eric Reid AeroFit | Instagram Portfolio
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So Gp4000 23 front and Gp5000 25 rear..? :D

Thanks,

I was referring to the GP 4000 23 and how the people who have tested it have measured it at about a 25 and the 25 close to a 28. I am assuming (hoping), without reading the article that this was intentional.

Lots of stuff within the search function about the GP 4000 and aero etc.

Cheers,
Maurice

I'm very surprised the 25mm GP5000 performed as poorly as it did (not that it was horrible). In my experience a 25mm GP5000 is only ~1mm wider than a 23mm GP4000 mounted on the same rim.

Note: Just looking at the graph, so didn't read the article.

What everyone should really be understanding is, at the yaw angles you spend the overwhelming majority of your time, there's not much difference. Factor in margin of error, and it could be a wash (then again, the differences could be greater). Agree, the GP5000 likely the overall fastest.

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Jim Manton / ERO Sports

I measured the tt 23 mm an the 5000 25 mm with 7,5 bar on the same rim:
tt 23: width 25,7 mm; height 24 mm
5000 25: width 25,3 mm; height 25 mm.

So the 25 mm 5000 is actually narrower than the 23 mm tt.

My further thoughts to this: at the higher yaw angles, on the road you’d probably be desperately trying to hang on to a steady state condition. More likely you’d be falling in and out of stall as you leaned and countersteered and dealt with gusts continuously. It in other words those high yaw numbers are probably irrelevant.

I'm not sure I agree. It could be highly dependent on the course condition. My n=1 is my local time trial course. It's a square that typically has a significant diagonal crosswind. The wind isn't strong enough to cause handling issues for most, but is certainly strong enough to notice and make it a significant course "feature." Across to Best Bike Split's estimates (the best information I have, not having used an aero stick device yet) , I typically see ~10 degrees yaw the entire way around. Almost no time at 0-9deg yaw (just the turns). And this is at about 29MPH bike speed.

Of course most courses won't be like this. But I think there's danger in looking at averages. There are big differences in drag at high yaw. So even if a course sees, say, a 2-degree "average", if you have a 10-mile leg at 12 degrees it may not be a good idea to over-optimize at 0-5 deg and eat a ton of extra drag for that 10-mile leg.

Because of this I look at the yaw out to 10 degrees, and am willing to sacrifice a little around 0 in order to be close to "best in class" all that way out to higher yaws.

Interesting to see at low yaw the 25mm ganged up and discrimination as we go out, speaks to the importance of difference of shape between all those 25's. Did they measure tire width?

Must be a wide open course. With all the outdoor testing being done, and I've tested above 20+ mph sustained winds, you just don't see any consistent yaw above 7 degrees. Puffs at 10 or more, but nothing that lasts long. Your course might be an outlier, but most people should be optimizing for 0-7 degrees.

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Jim Manton / ERO Sports

Either an outlier or BBS over-estimates angles. I know that the velocity measurements they take are from sensors way above wheel altitude, and don't know if they correct for that.

Kind of my point about BBS. In theory you’ll see 10 degrees constantly. In reality it’s probably varying around this, and moving between stall and lift, particularly as your bike isn’t locked into one place, meaning the actual behaviour won’t be like the smooth graph.

I think a more important question is whether the tires that show a large drop in drag at high yaw will be harder or easier to handle in challenging conditions, vs the tire with higher drag.... ?

.. than the GP5k 23 should be a nice boost on a Jet6 that was developed with an Attack .. oSo >>

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___/\___/\___/\___ the s u r f b o a r d of the K u r p f a l z is the r o a d b i k e .. oSo >>

The 15-17 watt swing in drag in just 2* yaw suggests to me that the 23c 4k, on that wheel, might feel quite snappy when it stalls. The 25c 5k lacks the 4k's deep, if narrow, sweet spot, but seems to stall much more gracefully.

I really wish they'd have shown a 23c 5k.

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"They're made of latex, not nitroglycerin"

Hadron ultimate with schwalbe pro one tubeless, 23 front, 25 back
...... if it‘s good enough for Lange is good enough for me

No flats, lower rolling resistance