PezCycling News - What's Cool In Pro Cycling : PEZ-Tech: ZIPP 303 Tubular Wheels & Hubs

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PEZ-Tech: ZIPP 303 Tubular Wheels & Hubs
You’ve seen and read plenty about Zipp’s 303 rim profile… A few major publications called it the best all round carbon tubular rim currently on the market (and “best” isn’t a frequently used term mind you). But there’s a little more to be said about the hoops and more to the hubs than most realize…


The world of bike wheels is reshaping…
With patent expiration, you’ve seen a few companies with prototype “wide” rims being shown around lately. What’s kinda funny here is that several companies are, in large part, tossing up a red herring by choosing “wide” as the the key designation.

“Width” wasn’t and isn’t the big focus of performance development and or the significant thing protected by patent.

Shape was… (and still is) the big player.

And companies can now start to try and develop the shape technology that Zipp has been developing for a decade or so…

But as others start down that road, things are changing quite a bit at Zipp and the 303 is a part of that change…



The 303 is a very good profile and was a stepping stone of sorts to Zipp’s new Firecrest shape tech that see’s the company looking to turn the proverbial corner (literally and figuratively) in design before competitors can catch site of them.

Zipp do a ton of shape changes and developmental testing (you don’t see the other 99% of product they produce but don’t bring to market) and the latest 303 was a pretty big change from the last…



The new version (above/right) is obviously larger volume. The size is part of what makes for a rim that is quite a bit stiffer than the last 303 (the thinner side walls don’t harm the stiffness but they do allow some flex that we’ll talk about below).

You can also note that the rim is wider at the tire bed and the brake tracks are no longer parallel (fig. A) and instead the simply follow the contour of the new full toroidal shape (hybrid toroidal was what Zipp called the old “flat brake track” version).

The wider tire bed will mate well with a few tire sizes from slightly more aero and narrow profiles to the fat section tires favored by the cobble monsters. The Full toroidal shape is a lot about aerodynamics and to some degree about comfort and stiffness…

Also note that there is less of a “point” where the brake track transitions in to the rim bed (fig. B). That little detail makes for better durability in general and a lot less likelyhood of pinch-flatting in places like Phoenix where we “think” the roads are bad, as well as places like [insert any city name where it snows] where roads really are bad. It also helps in places like this…


unlike Charlie Sheen, Nick Nuyens really was “Winning” at Flanders…

Here’s another result that’s partly down to the new shape and a great link to give the forum experts that spit out gems like; “there’s no such thing as rim deflection” or “rims make no difference in comfort” or “aero carbon rims are horrible for the classics”…



Shape is no small part of the deflection ability. Do that to most V shapes and they won’t (can’t) perform the same because they lack the same leaf-spring like (curved) side wall shape. With v shapes you’re driving energy up a straight section of carbon that gets a lot more confused about how to bend, and or doesn’t really give at all…

But again, it’s not just shape. Zipp also changed the carbon lay up (and a few other general molding steps) to facilitate flex. You can see the slightly stepped layers in the side wall of the rim…



The Red lines are stepped layers of the new rim. The green show the old side wall that uses more carbon and runs the carbon higher up the sidewall.

The new layup allows for deflection and that deflection aids in durability (after all, having some give means impact forces get absorbed by a far larger part of the structure rather than concentrating impact it at the rim bed edges).

And the pluses in strength (with plenty of material still at the spoke bed and rim bed) and stiffness (with increased rim volume) come at 1171 grams for the set…


The Aerodynamics?
It’s great to have invites to wind tunnel tests, but it can suck when you don’t have the rights to post what you see in detail.

I have not paid for the tunnel or been present at a Zipp test of the 303′s. But I have been to a test from another company who was looking at their wheels versus a couple of competitors including Zipp. So I can write stuff, but I can’t give up the really stinky cheese.

[That gets resolved shortly... A wind Tunnel is being built in Phoenix right now. It's called "Faster" (ride-faster.com) and more will follow]


The bottom line here is that the 303 at 1171 grams per pair and 45mm deep, performed better at all but zero yaw (which was very close for all wheels) than three very popular competitive brands at higher weight (100-300) grams and depths at least 10% and more than 30% greater. Nobody had a wheel under 50mm on par with the 303′s…

One of my favorite (stupid) arguments found in forums is that wind tunnels are “different than the real world…”. This garbage is said as if forum chatter is more “real” than the tunnels where virtually all solid development for aero testing takes place.

CFD models are getting better every day, but ask Timo Glock if he would rather see another year of CFD-only testing at Virgin F1… The wheel business has larger gaps in general than the F1 field because a lot of wheel companies total aero development research comes down to cutting someone else’s rim in to sections and trying to copy the shape (OK, maybe F1 teams do a version of that too). I would come close to guaranteeing you that’s already happen to Zipp’s toroidal rims as the patent goes away.

All that said about the rim, I’m not sure the biggest leap for Zipp in the past couple of years has to do with rim shape. There’s an argument to be made for the hubs being the most significant change…


What goes around…
The new 88 and 188 hubs are VERY good. I know a few good custom wheel builders that would never post it, but in private they’re extremely impressed with the newest twist points for Zipp and wish it were not the case.

The first time I had a look at the new hubs was in Indianapolis sitting down for a beer with J.P…



For starters, these hubs are more than twice the cost to produce than Zipp would spend to buy several of the top wheel brands OE spec’d hubs. They’re more than 5 times the cost of some of the low-name / no-name cheap-o wheel sets some people are choosing to buy direct from the far east…

And that’s not just down to US production costs. It would be the case even if Zipp outsourced to the far east (and that’s taking a shot in the dark that quality control for both production AND ESPECIALLY RAW MATERIALS could be maintained).

Zipp spec’d their own alloy blend for the hub stock and it starts life as a solid blank…



These are an American made product from North American refined materials (OK The bearings are Swiss… again versus far eastern parts). They’re machined using some of the slickest equipment available. The multi axis machining means that material can be removed with precision from many angles. That means that more detailed designs can be put into production so that parts can maximize weight reduction while maintaining strength, all while remaining at a still relatively affordable (relatively being a key term) production cost.


Lots of different bits (green) attack the solid material (Red)

Here’s the kicker. These super complex machines cost way more than the simpler one’s (multiples). Most companies use the simpler ones and just don’t do the same detail of work because loading and unloading of parts into different machines cost too much time and money… It’s just cheaper and easier to make less detailed parts.

Zipp spend the money up front (and spend the set up time) and get all of the detail into the parts. And they get it quickly enough to make the parts relatively affordable…


A couple of passes of the bits has the work started on the blank and the hub starts to take shape…



A few more passes from different tools (on the same machine) and massive amounts of material are turned away and its dang near ready for the next treatment…



The hub it’s self is really the sum of a lot of parts with a couple of main goals. A stiffer axel and a much stronger spoke holding body. Sure bearings are a part of the mix, but Zipp have always had very good bearings…



The axle is a very fat (by road standards) 17mm.



That presents a lot of added stiffness but would be worthless if the bearings were not well placed and if the spoke loading area were not able to handle the loads in a pretty limited space…

To do that in the front hub, Zipp machined the hub flange to allow the spokes to sit in with very little stress at the heads…



The ring snaps into place and as the spokes are tensioned, the retaining ring spreads the spoke loads across a larger area versus just at the spoke head…



That makes for better stress distribution and less stress on the individual spoke…

It’s pretty logical that the rear hub gets even greater machining detail.



Of course there is a lot of material removed to shed weight where the structure doesn’t need it. But there’s more impressive detail here again where the spoke heads need support on the off- drive side of the rear. There are simple slots machined in and a secondary finishing process is done in the same slot end (green arrows) so that the spoke head shape is matched perfectly so that more spoke material contacts the hub to better distribute stress…



Installed (dust cap removed for picture) the spokes sit in a nice custom fit bed…



Round the drive side, things are a little different…



The one area that peeves me about Zipp’s new hub is that a more expensive swap is required going from Campy Body to Shimano… Yes it’s still an easy process, but now, rather than just buying a free hub body, you have to purchase a more expensive, free hub body, spacer, seal and end cap… Unless you’re using a test set of wheels across different bikes with different components, this doesn’t matter to you… But it’s not as simple as before.



Speaking of the free hub body, engagement and power handling is improved on the new hub too (and that’s an improvement on a system that worked well before and could handle torque over in the 300 ft pound range…)



The pawls themselves are wider than before making for a greater contact patch but also move more freely, with a lighter action to create less drag than the old hub (which created very little drag to start with). The pawl material was 68 Rockwell last time I was at the factory, and I would guess it still is, as they’re still cutting it with an Electronic Discharge Machine at 20 millionths of an inch tolerance… I used it as a reference once before, but I have cobalt bits for cutting metal that are softer than the material Zipp use for pawls…

The finished product is a lot cleaner looking on the bike than the old set as well…



All the parts fit incredibly tight and what used to be carbon dust caps are now machined metal rings that also serve structural function…

Even the pinch rings are machined from solid stock…



And they’re made to in a shape that is at once aero and mechanically sound…


The small bolt (green arrow below) is what you’ll loosen on the non drive side of the rear in order to very easily adjust bearing preload.



On the front you’ll loosen one side and twist the other to adjust, then tighten that side again and loosen the other to rotate the pieces back to parallel with each other so they can be rotated to both face properly to the wind.

Preload can be done with the wheels still on the bike.


Are the 303′s so good that they’re potential trouble for Zipp’s other wheel sets?
Nah, Zipp are moving down the road in design for lots of products and the new 404′s are a good example.

But the 303′s are comparable speed holding to virtually all v shaped wheels at depths between 50 and 60, but they don’t suffer cross wind play much at all in comparison to deeper hoops.

They’re the exception to the rule about comfort (or the lack of) for deep V section carbon wheels as well. The shape and lay up give these wheels a bit of compliance that make for a notably smoother ride than those same 50 and 60 V section rims.

A relatively low MOI for these wheels compared to the deeper hoops is a plus as these have a lighter feel and spin up as well from lower speeds as you would expect from an 1170 gram wheel set.

One surprise with these being both light and compliant is that they’re stiffer laterally than past 303′s and, If I had to guess, I would say they’re stiffer than the previous model 404′s too (they don’t beat the latest Firecrest 404). The larger volume (fatter) rim profile brings some of the same character as larger diameter frame tube sections on a lot of bikes lately. The overall effect is very good on acceleration and a better, more direct steering feel under load in corners…

Braking on the 303′s is very good with Zipp’s Tangente and a few other softer pads.

The side wall shape not being flat has no negative effect…



I’ve not had a brake set that I couldn’t adjust to sit flat on the slightly tilted side walls. I have had some issues with some brake sets requiring different washer, pad holder and brake pad combinations to accommodate the wider rims though.

Another notable is that the brake tracks are a bit rougher surface than most all other rims. They initially wear brake pads quicker than most rims but as you bed them in, the wear becomes a bit less.



While the surface is a bit rougher finish, it’s very even though and even as pads bed in, these wheels suffer a lot less pulsing than a lot of smoother surface finished tracks. The performance is good enough that I don’t mind the brake pad wear and the surface of the 303′s seem to be handling heat better than a lot of other smooth surfaces as well.

That’s down to Zipp using different raw materials at the brake track instead just molding a thicker section of carbon and leaving it be (and or finish grinding it flat which breaks fibers). The problem with the use of standard carbon alone and without special resin at the brake track is that even though it’s thicker (which adds weight at the outside of the rim by the way), it’s still prone to heating up and deforming. That deforming is what most people feel in the heavy pulsing of their carbon wheels (and in the case of a lot of carbon clinchers, it’s felt in the form of blow outs…).


Sum it up
These wheels are great at holding speed and light enough to be called climbers wheels, so the braking has to be good, as what goes up, must haul ass back down… They’re also stiff enough and durable enough for crits. Add a smoother ride than anything this deep or deeper and you have a hell of an all rounder.

OK, they’re not deep enough to eliminate choices like the 404′s and 808′s and some folks will want clincher practicality in daily drivers… So these are not the absolute best choice in several conditions. But they don’t drop down virtually any list nearly as far as other more specialized products…

These are nearer the top of way more lists, for a huge range of conditions than most all other high performance wheel sets and virtually eliminate my desire to own any current V shaped wheel under 60mm or any other carbon tubular at all at less than 50mm DEEP…

The set will run you a suggested retail of $2300.

Take a peek at the 303′s and a few other products at ZIPP.COM


Have Fun,
Charles Manantan


Thanks for looking. If you have other experiences with gear, or something to add, drop us a line. We don’t claim to know everything (we just imply it at times). Give us a pat on the back if you like the reviews, or a slap in the head if you feel the need!

PezCycling News and the author ask that you contact the manufacturers before using any products we test here. Only the manufacturer can provide accurate and complete information on proper use and or installation of products as well as any conditional information or product limitations.

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