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On test: Zipp 303 'Cross Wheels, November 23, 2005
Tough rims for the mud-plug set
Carbon fiber wheels sound like a good way to throw money at a cross bike with little return. Not so, says Rob Karman, who is impressed with Zipp's carbon hoops.
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For the past several years, deep dish carbon wheels have been a popular choice among racers, first on smooth roads, and then in cyclo-cross. The unique demands that the conditions of cyclo-cross place on equipment has led wheel maker Zipp Composites to develop cyclo-cross specific versions of its two most popular wheels, the 303s and 404s.
First introduced at Interbike last year, Zipp's cyclo-cross specific wheels differ from their road brethren in three ways: the rims have an extra layer of carbon which Zipp claims increases their impact resistance twofold while only adding about 40g per rim; the hubs have been modified with extra seals to keep grit and grime out in the muddy conditions 'cross is famous for; and the wheels use Sapim Race butted (2.0/1.8mm) spokes for added strength. A full technical description of Zipp wheels can be seen in our recent review of the 404 road wheels.
So what does this mean in the real world? We got our hands on a pair of 303 'cross wheels and beat on them for about a month to find out.
First impressions
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Out of the box I was first impressed by how light they were. At 646g for the front and 818g for the rear, they were 6g under the claimed average weight per pair of 1470g. I like that Zipp says its nominal product weights are averages as rim weights all vary by a few grams due to manufacturing variances. It often seems that some rim manufacturers quote the weight of the lightest samples from the run! It was nice to see the real world product weight in the range of the claimed weight as well. A quick check on the truing stand found them to be straight and round with fairly even spoke tensioning. The hubs also felt exceptionally smooth out of the box, but we'll get to that in a minute.
I mounted up some new Vittoria Cross EVO XG tires and was ready to go. I didn't end up being the first to ride them though as I needed to take some photos of team mate and five-time consecutive US junior national cyclo-cross champ Alex Coelho using them. Besides looking really cool in the photos, I wanted to get his opinion on the wheels. The verdict? He wanted to keep them! But I had some serious reviewing to do so I took them back and set out on finding some of the rockiest trails I could find to test their impact resistance. Oh, and a race through sand during a rain/sleet storm just to round things out.
The rims
It took two weeks of purposely abusing, er, testing the Zipp 303 cross wheels to knock them out of true, and they were just enough out of true to rub on the brakes only when I was really going hard out of the saddle and rocking the bike back and forth. On trails that threatened to shake my teeth out, I thought for certain that I'd break one of the rims, but they held up just fine. I can't say the same for my back.
Braking performance was good, especially for carbon rims. I was using standard pads with Avid and Shimano cantilevers and had good modulation without a lot of 'grabbiness' often found with carbon rims. I'm really impressed with what Zipp has done with the braking surface of the rims with their Silca Ceramic coating.
Hubs
The hubs were silky smooth out of the box, but after only two or three rides, they were out of adjustment - (loose - and the carbon caps were flapping in the breeze. After a few more rides the freewheel would "pop" and skip when accelerating. At first I thought my chain was skipping, but after some investigation, it was determined that the pawls in the freewheel were sticking due to the grease being too thick. Both of these problems were quickly remedied by a pro mechanic and the hubs have been fine since, though not as silky smooth as when they arrived. I was a bit surprised that it had problems so quickly after coming from the factory.
Verdict
The rims truly are bombproof and with a little care, the hubs seemed to perform well. I would recommend these wheels to anyone seeking a lightweight racing wheel set that can handle a little rough handling.
Notes: The wheels tested were 2005 models which did not have dimpled rims. Zipp has since sold out of these rims and is now only offering the 2006 dimpled rim version. Zipp dealers may have 2005 models in stock which cost slightly less.
Zipp responds
After this review was published, Zipp design engineer Josh Poertner wrote to say that, "the hubs mentioned in the article have been completely redesigned for 2006 so that they are 40 grams lighter for the set as well as using a new carbon reinforced plastic clip to permanently attach the carbon dustcaps so it is impossible for them to come loose on the new design (definitely a complaint with the old design). The loosening of the hub you experienced was most likely due to a flaw in the molding of the additional hub seals which caused rubber to be in an area of the seal where the endcap tightens, and has also been fixed on the 2006 design, although you still can't put high viscosity grease in the mechanism due to the extremely tight clearances involved :-). These new hubs are the same ones that the CSC team have been using in their training wheels for the last 6 months without any issues."
Suggested retail price: US$1750/pr
Weight: 1464g/pr 646g front and 818g rear
Pro: Low weight; bombproof rims
Con: Hubs needed maintenance after brief period of use
More information: www.zipp.com
Cyclingnews rating: 
