Index Categories:
Tires – Effects of tire width on wheel aerodynamics
Tires – Effects of tire tread on wheel aerodynamics
Tires – Rolling resistance
From:
marcob Sep 16, 2006, 11:27 AM
Question:
Aero advantage of the Tangente Tire?
According to Zipp the aero advantage the new Tangente will save energy by 1-3 watt compared to some of the best available tires. The tires are developed together with Vittoria and are available in tubular and clincher.
Any comments ??
Josh:
The new tires are made in conjunction with Vittoria and the quality thus far has been really superior to the previous tire (not made by Vittoria).
The history of this tire was that we tested more than 40 high end tires on 404's and 808's and found that some of them were actually faster than the old zipp tire, which had generally been the fastest tire on our wheels for the last few years, and we narrowed the reason for that down to the degree of tread roughness, as well as tread thickness profile.
There seems to be a sweet spot somewhere between smooth and file-tread that really works well, so we computer modeled an equivalent surface roughness into a dimple pattern (that's all dimples are, just a form or roughening a surface in an orderly manner…). But the real excitement came when the Vittoria guys started working their computer design magic and realized that the dimples add essentially no stress into the tread, unlike traditional tread designs which have lots of sharp interior corners which act as stress risers, so the predicted wear and crack resistance with age of the tire was dramatically decreased.
This lower propensity to crack allowed us to go with a slightly lower rolling resistance rubber compound without any penalty, while the tire still showed excellent adhesion both wet and dry in testing, so we really think we have a winner here. 1-3 Watts is for a 404 or 808, more like 1-2 watts on the 303 depending on wind angle.
Unlike the previous tire this one will also be available in clincher.
A little history on the development: the previous Zipp tire was designed in 2002 and went on sale in 2003 and was the fastest tire we'd ever seen on our disc or 404 at the time, and the 808 and revised 404 shape were subsequently designed and developed in the wind tunnel using that tire, but in the mean time about 30 new tires have hit the market (plus we had access this time to some very specific specialty tires which we did not have access to before).
While our initial work on the earlier tire design was really primarily based around smoothing the tread to casing edge, our work this time around focused more on tread patterns and roughness as it seemed that tires with a slight tread lip but with perfect roughness could match or even beat the previous zipp tire, so we had more time and more experience this time around.
In fact, it seems that at the perfect roughness a little tread lip actually helps the situation by acting as a boundary layer trip strip so you will notice this tire having a roughly 0.5mm lip compared to the 0.3mm lip in the previous tire. Remember, the previous tire was the first tire ever designed in the wind tunnel, so everything was essentially new and unknown as nobody had done it before, this time around we know quite a bit more and have a more capable manufacturing partner so this is just the natural evolution of things.
Index Categories:
Wheel Aerodynamics – Tire/rim interaction
Tires – Effects of tire width on wheel aerodynamics
From:
jnielsen Nov 10, 2005, 3:10 PM
Question:
Clincher tires for Zipp 808s - recommendations
Just picked up a new set of 808s, and I seem to recall/hear somewhere that there are certain tires that simply don't fit well on the rims. I'm talking clinchers here...Any one have some experience/recommendations??
Josh:
Any clincher tire 20-23mm wide will yield optimal aerodynamics with your wheelset. As for the tight fitting tire issue, we recommend using the thinnest rim strip you can find (not Velox, it's too thick). Using Rox, Michelin or our own Zipp rim strips will give you up to 1mm extra clearance when installing the tire.
Enjoy your wheels!
Index Categories:
Wheel Aerodynamics – Tire/rim interaction
Tires – Effects of Tire width on aerodynamics
From:
john b Apr 26, 2006, 8:07 AM
Question:
Tire (or tyre) pressure at IronMan Canada?
A ride yesterday partly on nasty roads and in strong winds made me wonder: what is a good pressure to ride at IronMan Canada in a typical year? i.e. what's the lowest pressure on that course that's likely to avoid pinch flats? I was at 110 psi, front and back, and it was just a little bumpy. The weight of me, my bike, bottles etc. will be over 200lb (or 90kg) on 19mm. I expect to be buried deep in the mid pack.
Josh:
From all the data I've seen in the last 6 or 7 years, I have never seen any reason TO run a 19mm tire. Many wheels such as the Hed3 do work better aerodynamically with a 19 as that matches the rim width, but even with that wheel the aero advantage with a 19 seems slight compared to the increased rolling resistance, increased puncture and pinch flat likelihood, and poor ride quality, at best I would think that the advantages/disadvantages are a wash on these wheels. We do all of our tubular design around 21mm tires and clinchers around 23mm tires, and as such our wheels are faster aerodynamically with these tires than with 19's, so there is absolutely no advantage to run tires this narrow on our wheels.
Also, you are looking at a likely 3-5% decrease in rolling resistance in using a 21 over 19mm tire, and possibly even more improvement as you can run lower tire pressures with a 21 for even lower RR without increasing the pinch flat likelihood on poor road surfaces. Lastly, I think that for all triathlon events comfort and ride quality should really be considered as you may be costing yourself on the bike and the run by running 150psi in very narrow tires through higher rolling resistance and increased muscle fatigue due to high frequency vibration.