I got the Bonty Pro X Lite TT 700x23 tire onto my HED Jet 90 C2 rim today. Not impressed!

There's a definite gap, hardly discernible from the gap on my Jet 60 C2 rim with a Pro3 Race mounted on it. Pics below (First is the Bonty TT tire, second is the Pro3 race for comparative purposes)

Bottom line...the tire and this rim don't mix very well. At least, not as well as some others shown on this thread.

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My training

 
That doesn't look like the tire is mounted "completely". The "wing" portion should be up above the edge of the rim at least. Sometimes it takes a bit of "working" around the tire with your thumbs (and only a small amount of pressure in the tube) to get it to "pop" out correctly...and at other times it takes some high pressure and a little bit of water as a "lube" to get the last little bit to "pop" out on some stubborn ones (like an AW19 I was mounting on a non-C2 Jet 90 yesterday).

Of course, my only experience with mounting these tires has been with the 19C version on narrow rims. But, I still don't think it looks correctly mounted...

BTW, what's the sidewall thickness on the C2 rims? How does that compare to the "thickness" of the wings on the AW23 tire?

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http://bikeblather.blogspot.com/

Hard to tell from the photo but in the spirit of the dumb question is the one you don't ask, are you sure that the wing is popped out ?? It looks as if it might be caught under the rim. I have a 19 on a HED3 which forms a very smooth transition from rim to tire. It was recommended to me by Damon and Tom that water could be used as a lubricant to install the tire and facilitate the wings moving into place - haven't tried it myself but I did have a very tight 19 that I finally worked into place after 2 days. I see Tom had the same question.

That's what I originally thought too. However then I deflated it completely, and 'helped' the wing stay above the rim as I inflated it. The tire-side of the gap is actually the bottom-most part of the wing, and the gap is between the bottom side of the wing and the rim. I'd say there's 1.5mm of a gap there.

The sidewall is maybe a bit thicker than a regular rim, but I don't think that the matching of the wing/rim thickness is the issue.

The bottom part of the wing, which should be sitting flush up against the top most part of the sidewall, is actually pointing upwards/outwards away from the rim. This makes me think that perhaps the depth/thickness of the rim bed is leading to the tire being pushed upwards, instead of outwards towards the sidewalls as Bonty meant it to be. Does that make sense?

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My training

Normal for a 23; you definitely want the 19 (actual width closer to 20).

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Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

Wow I feel pretty special here, I have Tom A, AFM, and Damon Rinard responding.

So on the HED C2 Rim (23mm width) I should be using a 19mm tire in order for the tire to be flush against the sidewall?

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My training

Even on a C2 rim (like stal's), Damon?

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http://bikeblather.blogspot.com/

No data with the C2, but the fit pictured doesn't "look" good based on my experience.

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Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)

Better picture.... You can see the bottom of the BONTRAGER white letters sitting perfectly flush in the first picture, which is from a previous poster.

In my tire (700x23 on a C2 rim) the bottom of the white lettering is 3-4 mm above the brake track. This is why I think the tire doesn't mate well with the C2 Rim, its almost as if the tire is being pushed upwards instead of outwards and onto the rim. The wings have 'popped out', in fact they have popped out too much.

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My training

I would try the 19 tire, even on the 23. If it still doesn't work...then its likely the design doesn't mate well with the C2 rim...likely because of the thickness of the C2 rim (or bead) itself.

You're looking for something like the top pic.

Replying to the thread in general....

Does anyone know why Bontrager designed the Aero TT with a 120 TPI casing? It seems like if they would put the "wings" on a supple 290 TPI casing like they use on their Race XXX series they could have the best of both the aerodynamics and rolling resistance worlds.

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"100% of the people who confuse correlation and causation end up dying."

I'm sure Damon does ;-) ...but, he might not be able to share.

My guess would be the tradeoffs had to do with what casing material and manufacturing method best "worked" with the design of the "wings"...and, after all, even at 120 TPI it's actually a fairly fast rolling tire, much like the Michelins at 127 TPI.

Although TPI is one factor in determining Crr, it's not the only one.

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http://bikeblather.blogspot.com/

So let's say I'm running a C2 90 front and Jet disc rear (2008 non-C2 version). I currently have the standard 23mm RXL tires front and back. Would switching to the AW version on either wheel be faster? Would I go with a 19mm for the disc and 23 for the front...assuming the wings mate to the C2 rim correctly. I figured that the AW version might have a higher Crr (based on TPI) but be more aero (assuming proper fit).

For a perfect fit you also need a hooked rim! What I see on the picture is a rim with an angled edge. I have the same bad experience with the Mavic Ksyrium while the H3 fits perfect.

hm. what? By definition, I thought all clincher rims were 'hooked' rims.

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My training

What I meant was that the wheel rim should have a right angle instead of a smoothed one.

Sounds like a question for the guys at Hed. I'm still not convinced that a C2 wheel with ANY tire is faster overall than a narrow Jet rim with the AW19 ;-)

BTW, despite the relatively low TPI (basically the same as the Michelin Pro2Race/Pro3Race) the AW's tend to have fairly good rolling resistance...especially the "light" ones :-)

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http://bikeblather.blogspot.com/

So has anyone been able to see if the AW 19 fits on a C2 rim properly yet?

Just got my 19 today and put it on the C2 90 to see how it fits. I have one 6" area where the wings would not pop out until inflated to 100 psi(the min on the tire) They look much more like the H3 picture than the other C2s with 23s. There is however still rim lip, the black 45 degree bevelled part. It is, based upon eyeballing close to a tape measure, about 0.5mm. This point of the rim is wider than the xsection of the tire. I did not need to use any water to lube it to get the wing out either. Inflated to about 10 psi and pulled the tire up and worked around that way. First one side then the other.

I may try and link photos later, now I have to ride, the weather is too nice. Dang tire arrive as I was going to leave delayed me.

pics would be awesome!

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My training

My digital camera is a cheapo, so these are not very good. What I tried to get is not what I get, if you get what i mean The lip looks much larger in the photo than it does in person
The rim in the bottom pic is the 45 bevel, which is ~1mm measured along its surface

Wow...those C2 rims must have a THICK sidewall...

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http://bikeblather.blogspot.com/

I guess so.

the AWTT wing goes up to the edge of the flat portion of the top of the rim, but then there is a 45 degree bevel that about 0.5mmx0.5mm before teh braking surface. Nothing is going to cover that. My C2 rims are also not flush between th erim and the fairing either, maybe 0.25mm, but definitely noticable. Actually it varies arounf the rim from fairing flush to very not flush. QA/Qc issues. I don't know what the narrow rims were like.

The narrow Jet wheels are "dead flush" between the brake track and the carbon cap...and the wing on the AW19 tire comes up flush to the brake track as well.

Hmmm...it would be pretty interesting to see a wind tunnel "shoot out" between a narrow Jet90 with an AW19 and a C2 Jet 90 with whatever tire they think would work best. I know which combo I'd put my money on ;-)

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http://bikeblather.blogspot.com/

I'd put the 19 AWTT on the C2 as well, it looks much better to the eye than a standard tire on there, but I wouldn't take your bet, as I'd like to keep my money. enough commas?