Shimano WH-7850-C24-TL clincher tubeless wheels

By Mark Alden

I left my house, clipped into my pedals and rode down the bumpy traffic infested hill that I start nearly every ride with. At the bottom of the hill there is a 90 degree right hand turn that is strewn with potholes. Charging through that corner while dodging desperate morning commuters it became immediately apparent to me that the wheels Shimano had given to me to test ride are not your everyday run of the mill wheels. Instead of the normal jarring and sideways hops that I regularly experience in this corner, the wheels felt wonderfully planted and went through the rough pavement with a muted fluttering sensation.

I have been riding the Shimano WH-7850-C24-TL clincher tubeless wheels almost exclusively since early April putting close to 6000 miles on them. The WH-7850-C24-TL wheels are the top end Dura-Ace tubeless wheels (the wheels are compatible with standard clincher tires). They use a rim that is made up of 24 layers of uni-directional carbon fiber that is layered over a 0.55mm aluminum rim. There is also a less expensive scandium rim model that weighs 73 grams more (1458 grams vs. 1531 grams). New for 2010 is an Ultegra tubeless wheelset (1651 grams).

The name makes them sound more like the part number for television remote than a high end wheelset – which might explain why these wheels weren’t quite on my radar when it was time to buy some new wheels. When the Shimano Rep gave me the wheels to try out, I was skeptical and less than excited. Now that I have used these wheels for almost a full season, I can say that they are the best wheels that I have ever used. In fact, I can’t think of any other bike component that can have such a profound effect on how a bike feels and handles.

For those of you that are unfamiliar with tubeless road technology it utilizes a rim without spoke holes and a tire with a carbon bead that is designed to hook securely on the rim and of course no inner tube is used. A presta valve (with a gasket that seals the inside of the rim) is secured with a nut on the outside of the rim. When the tire is inflated it snaps and locks into place with several loud pops. The downside is that you will either need an air compressor or use a co2 inflator to install the tire. I have tried without success to mount the tires with a hand pump.

There are several advantages to riding wheels without inner tubes. Without tubes there is no risk of getting a pinch flat. This in turn allows for tire pressures in the 90psi range. My first thought was that the wheels would feel slow and spongy. Although I don’t have technical data to support my observations the wheels feel faster than any 130psi tire that I have used. There are a few explanations for this: the primary reason is that the low tire pressure allows the tire to conform to road irregularities and absorb shock; every time a high pressure tire bounces upwards there is a loss in forward momentum therefore making standard clinchers slower than tubeless tires (perhaps on perfectly smooth surfaces this wouldn’t be the case). The tires also have a supple feel because there is no inner tube creating friction that is present with a tire/tube combination. Additionally, the Shimano wheel's low spoke count (16 front 20 rear) slice through the wind nicely. The bladed spokes are manufactured by Shimano using high quality stainless steel sourced from Sweden. I have seen a few wind tunnel tests that show that the Shimano wheels are pretty aerodynamic – as good as some wheels with much taller rims and way better that the various Ksyriums that I have used over the years.

As far as handling is concerned it doesn’t get better than what these wheels offer. The cornering grip is insane. This was best illustrated to me when I decided to use the wheels at the Burlington Crit. at this years GMSR. With six corners that are littered with bumps, manhole covers, and raised brick edges in a1k course, this stage always kind of frightened me. However, instead of hovering in the bottom 3rd of the field I was able to stay up near the front feeling like Valantino Rossi in a moto GP race. I was watching other guys bikes skip and hop all over the place while my bike stayed planted and composed.

Another great thing about the Shimano wheels is that they can take a stiff harsh bike and transform it into a smooth comfortable bike without any energy transfer or weight compromise. I have ridden the same bike back to back with 120psi clinchers and the Shimano tubeless wheels and the difference in smoothness is significant. This smoothness also improves comfort on long rides. I like to call this TRT or Taint Relief Technology.

Flats can be virtually eliminated when a tire sealant is used. Although Shimano and Hutchinson don’t recommend it I’ve been using Stan’s latex sealant (they claim that it can damage the tire) and I only got one flat this year that the sealant wasn’t able to plug up. If you get a cut in the tire that the sealant can’t handle all you have to do is put a tire boot on the cut remove the valve stem and install a standard tube. I recently put in the Hutchinson sealant (which of course is OK with Shimano and Hutchinson) and I haven’t gotten any flats so far. I’m curious to see how it works because they claim that it won’t dry up like the Stan’s does which would be great because when replacing a tire peeling off the dried Stan’s sealant is a pain.

The wheels are proving to be very strong and durable. I have barely had to touch them all year. They have remained true and the traditional cup-and-cone bearings are well sealed and supposedly last longer and handle loads at various angles better than cartridge bearings. I recently took apart the hubs and the bearing grease was still clean even after a season of use in all kinds of weather. I also like that the freehub body is titanium. Cassette cogs don’t dig into it like they do on aluminum freehubs. The freehub is not serviceable (it is replaceable) but it is well sealed and shows no signs of contamination. Another testament to the wheels strength (and my stupidity) is when one of my water bottles was ejected while going over a railroad crossing at about 25mph. I tried to stop the bottle with my foot which clipped out and went onto the rear wheel and locked it up as I skidded for about 15 feet. When I stopped I figured that the wheel would have some serious damage to it. I was surprised to see that I had only bent one spoke and I was able to true up the wheel and continue riding. I later replaced the bent spoke (which was easy to do) and the wheel was fine.

There are a few downsides. There isn't much of a tire selection and there isn't a cheap "training tire" option. Currently there are just a few Hutchinson models to choose from but I heard that for 2010 some other tire companies are going to offer tubeless road tires. There is no Campy freehub option (there are a few aftermarket 9 and 10 speed Shimano splined Campy compatible cassettes available). And as I mentioned before to inflate the tires you will have to use CO2 or an air compressor. For me though the positives far outweigh any negatives.

Overall I couldn’t be much happier with these wheels. I like them so much that I am going to get another set for my other bike simply because I don’t want to ride on regular clinchers anymore. I’ll still use my 303’s for most hilly road races but for day to day training, crits and Battenkill the Shimano wheels will be my 1st choice.

MSRP:$1400
Weight:1458g
Spokes: front 16 - radial / rear 20 - 2 cross.
Rim: carbon/aluminum / width:20.8mm / height:24mm front, 23mm rear

WH7850 freehub body

tubeless valve

WH7850 front wheel

WH7850 rear axle assembly

WH7850 rear hub