More of in an absence of available aero data. Like say a 25mm GPTT the measures over 30mm wide on HED Jet+

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Isn't the SS and the GPTT basically the same time? I think the TT has a breaker. have you compared the two mounted up?

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Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

I ran the 25 TT on my Super 9 at Racine and it didn't look like that...much more tire meat protruding along the sides.

about 92 psi

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Surprised to see so many people with the 25 TT. How long did you have it before Racine, how many days pumped up etc? The tire will keep growing and growing.

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Actually we chatted before and after the awards cermony!

I had the 25 TT just a couple weeks and had it inflated on the disc for a few days. It is beefy but gave a good ride on the those cracked WI roads...even post rain without much tread. Usually I run a Force rear in the races with sketchier road surfaces like Racine. SS upfront on the 808 I have never had a problem with on any surface. Just did IMCdA with the SS 23 combo and felt great on the Idaho roads.

Rolling the SS on the rear... Another convert, great now SS just became even harder to track down ;)

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i would love people to put calipers over these tires and give us the width of the tire + the rim it's on.

i loved riding the turbo cottons, but i found them wide. not good, not bad, just 24mm was wider than other 24mm tires, same with 26mm. maybe i'm imagining things. i'd just like to see people with reliable calipers measure max outside diameter of inflated tire, with brand and width of tire, and the rim the tire is mounted on, to see if 25mm is really 25mm and, if not, how that varies tire by tire. (unless this has already been done.)

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Dan Empfield
aka Slowman

Josh has done a good job of giving a snapshot of how rim widths generally affect mounted widths here: https://silca.cc/...-1-how-we-got-to-now

My own spreadsheet lists mounted widths for each tire. The vast majority have been as mounted on my "standard test wheel" which has a Mavic Open Pro rim, which I believe is 15c width. On that rim, a (new) 24C Turbo Cotton measured at 24.25mm according to my digital calipers. I also show that tire as mounted on a Hed Plus rim (21c internal width) where it measured out at a whopping 26.4mm. You can see all that here:
https://docs.google.com/.../edit#gid=1224624714

In other words, the actual mounted width is not only going to depend on the particular tire, but on the rim it's mounted on (and the pressure as well)

But, in the end...what was wrong with them being "wide" for you?

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http://bikeblather.blogspot.com/

"But, in the end...what was wrong with them being "wide" for you?"

i liked that tire. but i put 26s on my supersix evo and they were within 1mm on either side of hitting the chainstay. other tires, same rims (american classic wheels, 25mm rims) were nowhere near that wide, that is, a 23mm tire had way more than 2.5mm clearance between rubber and frame. so i put the 24mm cotton turbos on, same wheels, still very close to the chainstay.

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Dan Empfield
aka Slowman

What's the internal width on those rims? (that's what matters for this). I find that going from a 15mm internal width rim to a 21mm internal width, the same tire "grows" by ~2mm, or more.

Going from the 26 to the 24 should've gained you only ~1mm on each side. That may not have been enough to notice without actually measuring.

And, what other tires? Just like some tires measure large in general (such as certain Conti models), there are others that measure out relatively narrow. The Turbo Cottons IME measured out pretty true to size when mounted on a rim closer in size to what the ETRTO standard calls for.

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http://bikeblather.blogspot.com/

Thanks everyone.

I will run a new GP TT 23mm up front (808) and my (not excessively) used TC 24mm on my Super 9 disc.

Was this a new GP TT or was this previously used? Are you going to add it to the chart, or is there something ahbout the tire/test that doesn't make it chart worthy yet? I presume, you just haven't added it yet, but thought I would check. Only reason I am curious is that I am running out of viable Supersonics and they are still not in stock anywhere.

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Yeah, a new GP TT. I haven't updated the chart yet...I have that and all the tires I did for the Flo study to add as well. I need to do that soon.

Oh yeah, one of the other tires I tested was the Force from the Flo aero tests, and it rolled in the faster group (as their analysis assumed).

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http://bikeblather.blogspot.com/

That's twice I've seen the Force roll surprisingly fast. Any theories as to why that might be? I was always under the impression that the Force actually had more tread than, say, a GP4000 and certainly more than the Attack. No?

That sounds like a whole bunch of comfort to me :)

I did some field testing this spring with a 23mm and 28mm (which measured 31mm iirc) GP 4000S II on a HED Jet+ Disc. It was just four runs (which took me nearly two hours with tire changes) and I made the dodgy assumption of identical Crr for both tires but the results in Aerolab indicated no significant aero penalty (the 28mm was faster in both runs actually but not by much and that could have been noise from position etc). As an aside, I had to pull the rear brake pads off my Speed Concept to get that 28mm to fit.

Tl;dr: for a rear wheel that's well shielded by the frame at low yaw I don't think there's a penalty for running a 28mm (measured width, so more like 25mm spec) tire on a wide disc like the Jet+.

I owe the platypus thread a data contribution when things calm down this fall.

Isn't how the air leaves an object just as important and sometimes more important than how the air "sees" it initially? Therefore, a poor trailing edge is not mitigated by hiding the leading edge with the frame.

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My YouTubes

Both are important. I can't comment with any authority as to the weighting. With that said, the airflow the far back on the bike is pretty dirty. The trailing edge of the front wheel/tire is significantly more important IMO.

Perhaps it is dirty and I agree that the front is more important, but I was replying to the idea that there is not a penalty for running a 28 width tire on a Jet Disc. Maybe not on the leading edge of the disc as it is shielded by the frame but the trailing edge would cause issues for sure or at least that is my question.

This is something I struggled with when deciding on the Zipp Speed SL in 27 for my Stinger disc. However, the 27 actually measures narrower than listed and my disc is pretty wide at the brake track (28mm). Couple that with the comfort being well above the beat-me-up ride I had with my Schwalbe Ironman (butyl tube type), I am more than comfortable with pulling the trigger and running that setup.

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My YouTubes

I think the tread is actually thinner than a GP4K, and they are fairly wide.

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http://bikeblather.blogspot.com/

Huh. I'm 90% sure I've read that it's thicker than the tread on the Attack. I wonder why the Attack is so inconsistent. Hmmm...

The Force is slightly bigger than the GP4000, and has thinner tread.

The 23mm GPTT and Force are about the same size but I'm guessing from the weights the GPTT might have even thinner tread. The Force has grooves, which tend to be good for aero.

NOBODY understands grams of drag, watts, and time savings. They just think they do. Seems to me that it would be better to use units that make sense, that actually can be understood with a little effort. If it is too much effort, then move along... nothing to see here....;)

Isn't the SS and the GPTT basically the same time? I think the TT has a breaker. have you compared the two mounted up?

I've never bought a GPTT, but reports put it wide for it's size while the SS is small. The GP4000 is in between. The thick tread on the GP4000 makes it tall for its width, while the SS and TT are pretty round.

Yes, the SS has no vectran belt and should be faster than a GPTT.