@Paul, interesting, I have personally talked with a Zipp rep and was told the 19mm or 20mm tire is the most aero tire to put on the alloy clincher front wheels as those both have a 19mm brake track. However she still felt the zipp tangete was still the best choice for some of the other reasons you noted (and ofcourse because they sell it). For tubies they have been wider for a while and Zipp has recomended 21 for a long time and discouraged using 19 or 20 on a tubie.
My guess is Josh's quote is based on the tour teams using the tubies. I have personally rode both a 404 and 808 alloy chincher front with a bonty aerowing TT 19 last year and it surly looked very aero (noticably better fit to the rim) and I could not notice any difference in the ride from the 20 vittoria or 21 zipp that I have also used up front. In all cases I had a 23 on the rear.
FWIW, I just had the conversation again prior to oceanside, once with zipp tech support on the phone and then once with the same rep I mentioned before at the oceanside expo. For firecrest it doesn't matter if you are are clincher or tubie, the recomendation is 21mm for the fastest and 23 if you want more comfort, are bigger, etc. 21 f / 23 r is what they recomend for 70.3 and 140.6 due to the longer time in the saddle with a run after, but for a 40k TT or shorter they would go 21 f/r. The also said the going 23 f / r has very little downside as the new firecrest shape test well with those tires as well.
Matt - For packing reasons, I'm going to take my 404s w allow rims to Regensburg (and the disc cover I just got this week). I'll be buying fresh tires this month too...either the Bonty Aerowings which I've used on my HED wheels or maybe the new Bonty R4 which I don't know much about. Whether I get a 19 or 21 on the front isn't too big of an issue for me, but I don't understand why if the narrower tire is good for the front it isn't also used on the back instead of a 23.
Jordan Rapp mentioned in his article that people assume that the new Firecrest rim size means they should be using a wider tire...he says no. Since you are one of the more technically inclined members, I think you would find it a a must-read article.
Paul, my undersanding is the narrow tire does decress thet drag on the rear tire as well and is the fastest choice. However the reason I've been told by the zipp rep/tech support to run the larger rear is 2 fold. 1) they said the rear is almost always behind a seat tube or frame cut out and therefore it isn't the leading edge like the front and makes less of an overall impact as only the trailing edge comes into play. 2) they say the 23 is a more comfortable tire (which I have noticed on my own as well) and that it's a good way to gain a little comfort for long rides with very little impact to drag (but there is some). I was told for a 40k TT they would absolutely run the narrow tires (i.e. 21 on firecrest) front and rear, however my question was around 70.3 and 140.6.
The last put I was trying to make was that they said the difference in drag between a 21 and 23 on a firecrest wheel is less than the difference between a 21 and 23 on an alloy clincher. In otherwords there is still an aero penately for going with the wider tires but it is less then it was on the alloy clinchers. I don't think I explained that right in my first repsonse.
I'll definely check out the virtual compliance article and see if my understanding changes.
Thx Matt. I'm not fast enough to worry about using a 21 or less on the rear, but I'm going to make the change on the front. I've been riding 23mm tires for the past 5 years and it's time to take advantage of some more free speed!
OK...questions about the group buy Corsa tires and latex tubes we got...I'm planning on putting the latex tubes and Corsa tires on my zipps; which I will use for my race rehearsals and races.
Is the idea about the latex tubes just to lower the rolling resistance? those tubes along with the Corsas, lower significantly than standard tires/tubes? Are there any other differences between latex and standard tubes (what material are standard tubes any way?) ? Can I use standard co2 cartridges to refill latex tubes, or is any special gas cartridge needed?
Yes, latex tubes are to reduce RR...nothing else "good" about them. There is some evidence they may pumcture a little less easily, but not at a level that matters. They are much more porous than butyl, though, so you have to fill them for every ride.
Standard tubes are polybutylene (called "butyl") that is modified to make it stretchy/plastic with various crosslinking and flexibility agents.
You can use CO2, but it bleeds out of latex very quickly. Like hours. The usual wisdom is that you put latex tubes in your tires, but you use butyl tubes for the spares. If you have a flat very early into an IM, you don't have to worry about the diffusion problem of CO2 and latex. This is a better solution than trying to find a special cartridge
Also make sure to mount the tires correctly with the arrow pointing in the direction the wheel rotates. On mine, it was logo side on the drive side. First time I've noticed directional arrows on a road tire. did my last race rolling backwards. I think it slowed me down by at least 5mph!!! Or maybe it was the headwind.
Thanks all for the info. Rode my Vittorias and latexs for the first time this evening. They felt fast, even if I don't have any scientific evidence to support that.
I'll ride my RR#1 on them this weekend for the true test over distance.
Comments
My guess is Josh's quote is based on the tour teams using the tubies. I have personally rode both a 404 and 808 alloy chincher front with a bonty aerowing TT 19 last year and it surly looked very aero (noticably better fit to the rim) and I could not notice any difference in the ride from the 20 vittoria or 21 zipp that I have also used up front. In all cases I had a 23 on the rear.
FWIW, I just had the conversation again prior to oceanside, once with zipp tech support on the phone and then once with the same rep I mentioned before at the oceanside expo. For firecrest it doesn't matter if you are are clincher or tubie, the recomendation is 21mm for the fastest and 23 if you want more comfort, are bigger, etc. 21 f / 23 r is what they recomend for 70.3 and 140.6 due to the longer time in the saddle with a run after, but for a 40k TT or shorter they would go 21 f/r. The also said the going 23 f / r has very little downside as the new firecrest shape test well with those tires as well.
Jordan Rapp mentioned in his article that people assume that the new Firecrest rim size means they should be using a wider tire...he says no. Since you are one of the more technically inclined members, I think you would find it a a must-read article.
The last put I was trying to make was that they said the difference in drag between a 21 and 23 on a firecrest wheel is less than the difference between a 21 and 23 on an alloy clincher. In otherwords there is still an aero penately for going with the wider tires but it is less then it was on the alloy clinchers. I don't think I explained that right in my first repsonse.
I'll definely check out the virtual compliance article and see if my understanding changes.
Is the idea about the latex tubes just to lower the rolling resistance? those tubes along with the Corsas, lower significantly than standard tires/tubes?
Are there any other differences between latex and standard tubes (what material are standard tubes any way?) ?
Can I use standard co2 cartridges to refill latex tubes, or is any special gas cartridge needed?
Standard tubes are polybutylene (called "butyl") that is modified to make it stretchy/plastic with various crosslinking and flexibility agents.
You can use CO2, but it bleeds out of latex very quickly. Like hours. The usual wisdom is that you put latex tubes in your tires, but you use butyl tubes for the spares. If you have a flat very early into an IM, you don't have to worry about the diffusion problem of CO2 and latex. This is a better solution than trying to find a special cartridge
I'll ride my RR#1 on them this weekend for the true test over distance.