JOIN THE REVOLUTION
We were fortunate enough to have a demo set of one of Shimano's newest wheel creations in our possession. So naturally, I had to take them out for a spin so I could write about them here for my 2.5 loyal readers! (Thanks mom, dad, and Fido...)
But, first - the model number is not enough to tell you what is going on with these very special wheels. This is truly a new and revolutionary product, using proven technology, but unlike anything I've seen applied to wheels in this industry. The 7850 C24 CL is both a carbon fiber clincher and an aluminum clincher. How's that work? Well, Shimano has engineered an extremely thin-walled aluminum double-wall clincher rim. Just how thin? Without caliper measurements; after seeing a cut-out rim section I would say that the walls of the box-section are no less than half the thickness of a similar, all-aluminum rim. On top of this super-thin rim, Shimano then bonds a carbon fiber "skin" which structually stiffens and strengthens the rim without adding great amounts of weight. The total product is a roughly 380 gram, 24mm deep rim. For comparison's sake; A Mavic Open Pro is 420 grams and a DT Swiss RR 1.1 is 410 grams.
NUTS AND BOLTS
The spoke nipples thread directly into the rim via threading machined through both layers of the rim body. Shimano's decision to move the spoke nipples back to the rim makes me very happy as they're much easier to adjust in this position rather than at the hub - as in many older Shimano wheel system designs.
The rim is also wider than many conventional rims - about 22 mm compared to 19 mm. Several makers - most notably Bontrager - are moving to this wider rim standard for several reasons: 1) a "rounder" tire cross-section should reduce the likelihood of pinch flats; 2) the rounder section should make the tire's contact patch also more round, increasing cornering traction and reducing a tire's tendency to "flop" into corners when leaned over; 3) wider rims are marginally more laterally stiff. All good things. The one drawback is that if you are frequently switching wheels between 19mm and 22mm rim sections - you may have brake adjustment nightmares; depending on the brake calipers you are using.
The hub is also new - 9 speed users rejoice! Gone is the 10-speed specific freehub body of the first-generation 7800 series wheels. This great, but limiting freehub has been retro'd back to the 8/9/10 speed compatible design made from titanium - instead of the more common steel or aluminum. Also new is a different spoking pattern which allows for broader bearing spacing; especially on the drive-side. The broader spacing improves stiffness and durability and also allows for the drive-side spokes to be set further off-center which reduces dish and builds a stronger, stiffer, more durable wheel. The spokes are new, Shimano-made, nail-head, oval profile stainless-steel. The bearings are signature "angular-contact" Shimano cup-and-cone style.
The test rig was my Waterford R-33. I installed my Ultegra 6600 12-25 cassette and my "winter" tires: Michelin Krylion Carbon 23's. Other details: 16 front spokes, 20 rear. Weight: about 1400 grams. The labels on the wheels claim 1380, but I've seen published weights of 1370 to 1390 grams (without skewers). Wheel weights do always vary from one set to the next slightly - so don't put too much faith into published weights. Actually, that's a good practice for anything for that matter! One more cool fact: Shimano tested the strength of the laminated rims by trying to pull a spoke out of the threaded rim. The gauge showed a weight of 790 kg (1738 lbs)when the rim failed and the spoke nipple pulled through. While that's impressive enough; it was the aluminum part of the rim that failed - not the carbon! This is not a rim that you need to worry about.
So; how'd they ride? I was really quite impressed. I've only once ridden clincher wheels lighter than these (the 1295 g Bontrager Race XXX Lite Carbon Clincher) and then I was only mildly impressed as I was disappointed with the lack of stiffness. The Shimano's were not like this at all - they were very impressive. I'm blessed to have a decent testing loop right out of my driveway with a mixture of road surfaces, long climbs, steep climbs, some fast flats, and a great descent to wrap up.
What I noticed first about these wheels - about 25 minutes into the ride as I hit a rougher section of road - these don't feel like aluminum wheels. They feel like full carbon in that they have a vibration-muting quality to them that almost makes you wonder if your rear tire is going flat. They're very smooth. They're stiff enough to sprint confidently on and don't feel like they're winding-up or flexing on standing climbs. Their low rotating weight accelerates very easily and seemed to translate into less time spent in my easier gears. My 23t cog saw a little more action than usual thanks to these wheels. I wasn't able to climb every incline one gear harder like I have on some wheels; but I definitely spent less time in my 25t cog when I had to go to it.
My only real gripe is actually more a matter of personal preference and riding style. I personally prefer a deeper section rim with a more aerodynamic profile and slightly more mass at the periphery. The aero rim is more efficient at speed and wheels with more mass at the rim will carry speed a little longer through the transition into an incline because of their greater inertia. These qualities play to my riding style. While the C24's were fun to ride, if I were personally spending my own money on them, I'd want something deeper. Thankfully, Shimano has those wheels planned for production as well - The 7850 C50 CL! I'll have to wait for those for sure... However, if you find you're better served by lighter, lower profile wheels - and don't want to mess with carbon-specific brake pads - these are worth a consideration. I know I'll be looking for a way to get my hands on the C50 CL's.
In all, a great set of wheels - and certainly priced fairly at $1100. Great work, Shimano!
Thanks for reading.