This is an interesting new product for Zipp. They replace the 302s, but are tubeless and meant for wider tires. I’ve seen it suggested they are targeted at the endurance and gravel markets. Has anyone studied them and thought about them outside those segments?
As a side point, it’s a bummer to see Zipp take the manufacturing outside the US, but I suppose that’s the reason for the attractive pricing.
There are suggestions Zipp has a few other new products in the pipeline. What might those be?
For what it’s worth coming from a Zipp employee, I spent all last summer racing criteriums on these wheels and they are, hands down, my all-time favorite crit wheels. I weigh 170lbs(77kg) and setup RT28 Zipp tubeless tires at 55-58psi and I’ve been using them exclusively on the road for the past year. I know the pressure numbers sound like crazy talk, but there are several design changes made to allow you to run much lower pressures. This is the future of road cycling.
For what it’s worth coming from a Zipp employee, I spent all last summer racing criteriums on these wheels and they are, hands down, my all-time favorite crit wheels. I weigh 170lbs(77kg) and setup RT28 Zipp tubeless tires at 55-58psi and I’ve been using them exclusively on the road for the past year. I know the pressure numbers sound like crazy talk, but there are several design changes made to allow you to run much lower pressures. This is the future of road cycling.
David, any info to offer on tire limitations or recommendations for the new hookless 303S? The Enve hookless AR’s specifically mention not using Conti GP5k TLR tires while Conti’s are labeled to only used on rims with bead hooks. We’ve been running the Conti’s on the 21mm internal width 303’s and they’ve worked great, but these have bead hooks.
Definitely look good for that price point and look likely to compete with the new Enve foundation series. I’d take a pair of either.
I was actually wondering what people would choose between those two wheelsets. Enve’s price point is a bit higher but i’d probably go for a pair of foundations given how much I enjoy my 5.6s.
Definitely a good question, and I’m not sure either. I have a pair of top of the line Enve’s on my road bike and am in the market for some back up wheels since I’m trying to switch to all disc brake thru axle configurations. The price point on the Zipps definitely has me considering them as a viable option.
Definitely look good for that price point and look likely to compete with the new Enve foundation series. I’d take a pair of either.
The statement below from the article is both totally untrue and misleading in terms of relationship between rim width and ride quality (its also grammatically inaccurate):
This is important: The comparisons in contact patch and sidewall compression above are based on using the same size tire at the same tire pressure. They’re to illustrate the benefits of a wider rim when you want to run lower tire pressure. Trying to run lower pressures on a narrower rim won’t get the same results because they’re less volume to cushion the ride
The width of rim affects the shape of tire but not the volume. A tire has a set volume not matter what rim you mount it to and that is not debatable. What wider rims provide is more effective side wall support at a given volume which prevents a tire from burping or flexing at low pressure when cornering hard. This lateral flex can be a big source of efficiency loss when you run very low pressures and is why you wouldn’t run a Zipp 404 at the pressures they recommend for the 303S. But it not all roses and sunshine.
Because the total volume has stayed the same and you have reduced pressure you significantly increased your chances of bottoming out the wheel on a pot hole, cobble stone, etc. Its like letting the air out of a shock. The ride will feel more plush and supportive on the small stuff but at the expensive of big hit support. When you look at pressures, tire volume and tire tire casing height the Zipp 303S with a 28 appears more vulnerable to bottoming out than a MTB bike with a 2.4-2.6 inch tire run at standard pressure for that system. Bottoming out is an issue in the MTB context and fancy foam based systems have been developed to protect rims. So the question is do the benefits outweigh the risks? On a muddy MTB track where traction is king its worth it. I will take some convincing that on the road this is also true.
I thought the volume does change with internal width… if you run a tire on a narrow internal width rim, isn’t the effective circumference (tire plus rim bed) necessarily smaller than a rim with a wider internal width? The tire has the same material in both cases, but the wider rim has more ?
Definitely look good for that price point and look likely to compete with the new Enve foundation series. I’d take a pair of either.
The statement below from the article is both totally untrue and misleading in terms of relationship between rim width and ride quality (its also grammatically inaccurate):
This is important: The comparisons in contact patch and sidewall compression above are based on using the same size tire at the same tire pressure. They’re to illustrate the benefits of a wider rim when you want to run lower tire pressure. Trying to run lower pressures on a narrower rim won’t get the same results because they’re less volume to cushion the ride
The width of rim affects the shape of tire but not the volume. A tire has a set volume not matter what rim you mount it to and that is not debatable. What wider rims provide is more effective side wall support at a given volume which prevents a tire from burping or flexing at low pressure when cornering hard. This lateral flex can be a big source of efficiency loss when you run very low pressures and is why you wouldn’t run a Zipp 404 at the pressures they recommend for the 303S. But it not all roses and sunshine.
Because the total volume has stayed the same and you have reduced pressure you significantly increased your chances of bottoming out the wheel on a pot hole, cobble stone, etc. Its like letting the air out of a shock. The ride will feel more plush and supportive on the small stuff but at the expensive of big hit support. When you look at pressures, tire volume and tire tire casing height the Zipp 303S with a 28 appears more vulnerable to bottoming out than a MTB bike with a 2.4-2.6 inch tire run at standard pressure for that system. Bottoming out is an issue in the MTB context and fancy foam based systems have been developed to protect rims. So the question is do the benefits outweigh the risks? On a muddy MTB track where traction is king its worth it. I will take some convincing that on the road this is also true.
That’s cobblers.
The volume changes. Think of a trapezium vs a square or rectangle. The volume of the trapezium varies as the 4th side changes dimension. It’s pretty basic early years school geometry - hardly partial diff or Laplace transforms.
David, any info to offer on tire limitations or recommendations for the new hookless 303S? The Enve hookless AR’s specifically mention not using Conti GP5k TLR tires while Conti’s are labeled to only used on rims with bead hooks. We’ve been running the Conti’s on the 21mm internal width 303’s and they’ve worked great, but these have bead hooks.
They are compatible with any tubeless or TLR tire between 25mm-50mm (labelled width), unless the tire manufacturer states incompatibility with hookless tire beds. 5bar (73psi) is the pressure limit on hookless tire beds within ETRTO standards.
The volume of the system can change but the relevant tire volume doesn’t change. Any changes in volume are associated with the space below the rim bead and increasing this system volume is a bad thing not a good thing.
Part of the problem is that volume is a misleading way to thing about what matters in the system. Pressure over an area creates force. So as you increase the area of rim bed by increasing the width you increase the force on the rim at a given pressure. Too much force and you blow apart the rim which is why you can’t put a lot of pressure in the Zipps. Its a critical failure issue not a speed issue. At the same time a given 28mm tire has a very finite area irrespective of rim profile. The pressure in the system exerted over this area gives you your tire casing tension which is what actually matters
It was appreciated several years ago tire casing pressure is what really becomes important not absolute pressure when starting to compare wheel/tire systems in terms of rolling resistance. At really high case tension a tire wants to ping rather than deform. At too low a casing tension then acute forces, like hitting a pothole, can cause a ton of deformation and you will hit and crack the rim. You can get away with really low casing pressure if you run massive tires because are able to increase the available area of deformation which increase the amount of force the tire can take before you hammer the rim. Because casing tension relates to tire size as well as pressure you actually run lower pressures in wider tires to ensure the casing tensions remain the same. 72.5 psi in a 28mm tire is a reasonable casing pressure but you start running into problems with 25 or smaller.
Bikeradar puts it like this in there review: ***If you’re running tyres no smaller than 28mm, 72.5psi will likely be enough for you, but it’s very important to adhere to the stated limit as exceeding it risks provoking a blowout. ***Stated differently you are not likely to damage the rims when riding 28mm at the maximum recommended pressure but do not over inflate the wheels.
So I was impressive with my words. Air is compressible and tires are malleable so the final volume of tire depends on the tire pressure because the tire will change shape as a function of tire pressure. But in the real world on 28mm tires this is splitting hairs. The trapezium is a good example whereby the base is defined by the width at the rim beds and net length of all other sides is mostly fixed but expands a bit as pressure goes up and sidewall support goes down. What doesn’t matter in this system is the volume. What does matter is the height, the relative aero profile, and the tension on the side
The height tells you how much vertical displacement you have before you crack your rim. As you widen the base this height decreases so more risk of rim cracking if all other factors stay the same
Aero profile is self explanatory. Going wider at the base can help but so can moving to a small tires so its a relative optimization. Everything I have seen so far says an optimized 22 or 25 beats and optmized 28.
The tension on the sides equals your tire casing tension. This is what defines rolling resistance. In our discussion its entirely a function of pressure and changing the base of the trapezium will have not effect on the tension. Zipp says go much lower on casing tension than previously recommended. I am not sold as its a super convenient way to side step why you can’t go above 72 psi. As the pressure goes up the force on the base also increase and the wider the base the more total force is exerted on it. To much force and rim bed blows apart and this limit is very low according to Zipp. The added problem is that casing tension works in conjuction with point 1 above to protect your rims so you can get away with lower tension if you have more height. As a 60kg rider I would be comfortable riding a 28mm at 60psi or below but I wouldn’t recommend a heavier rider to go charging into cobbles with that setup.
Too much force and you blow apart the rim which is why you can’t put a lot of pressure in the Zipps.
5bar (73psi) is the pressure limit on Tubeless Straight Side (hookless) tire beds within ETRTO standards. Page M.16, note 3 in the 2019 manual. The 5bar limit is unrelated to the maximum inflation strength of the rim.
