Thursday, February 21, 2008

Tested: Shimano WH 7850-C24-CL Wheelset

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.

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.


  1. Thanks for the great review. I think yours is the first personal review out there, and I have been looking for some time. I'm still waiting for my set to arrive, and they seem to be delayed again and again. I can only hope they come beofre the snow melts.

  2. Thanks for the feedback, Robin. The word I have from Shimano is that these wheels are not due for consumers until June. I don't know where you live, but my guess is that the snow will be melted by then. Sorry. They're worth the wait though. I'll have to wait longer for the C50 CL's that I want!

  3. Hi both, i am from the UK i have had these wheels on order now since November, and they are not due to be released by Madison (the Uk Shimano distributor) till early July!!! I've checked with Madison, and i have checked through reputable bike shops, i have also checked with a good few friends i have in the US and they cannot get their hands on them, perhaps we need to do some on wheel test Robin like Matt and then....just.....forget to give them back!! haha...worth the wait and weight i guess! I'm building a new BH Global concept G4 frame up with sram red and cinelli ram/slr teknologika flow finishing it off...and a set of the DURA ACE WHEELS WHEN THEY BLOOMIN LAND UP!!!! Till then i am borrowing a set of my mates Ksyriums to put me on! Good review Matt, even more envious and can't wait for them now!!

  4. Hi, thank you very much for this review. I am French and I will have these wheels this week-end, after long months of waiting, don't be desperate. I hope to be as impressed as you were. But it won't be difficult as my wheels are old Dura-Ace from year 2002.

  5. Still riding these wheels? How are they holding up? Any issues with galavanic corrosion at the aluminum nipple/carbon zones?

  6. Erik-

    Sorry for the slow reply...just staying busy.

    Unfortunately the wheels I reviewed here are demo wheels and I had to give them back to Shimano; but since my review, we've seen several sets in the store which have been used mostly in our nasty, dirty, wet cyclocross races we so famously host here in Portland. Holding up quite nicely in those conditions with no real signs of galvanic corrosion, de-lamination of the carbon, or excessive wear of the braking surfaces.

    If they can stand up to PDX cyclocross conditions; I think they're pretty tough!

    Hope that helps.


  7. Do you really need carbon specific brake pads? The braking surface appears to be aluminum, which would mean regular ol' brake pads. Am I seeing these wrong?

  8. TJ-

    Standard brake pads will serve you just fine. The brake track on these rims is part of the aluminum "backbone" of the rim. The carbon part is merely the shell over the rest of the rim.

    Any time the brake track is carbon though - from my experience - you'll be better off with carbon-specific pads. Standard pads are SUPER grabby on the carbon, which results in a pulsing or shuddering feel. The carbon-specific pads (in my experience with cork and Shimano's carbon-spec rubber compound) are smoother, modulate better, and don't wear as quickly (but are far from desirable on aluminum brake tracks).

  9. Hi Matt, I have recently purchased a set of these wheels and have found them the slowest wheels I have ever ridden. The main problem i find is that the hub "stick's" every time I free wheel I feel myself slowing. When the wheel is in a stand and is pedalled it even engages the cranks. I have stripped the wheel down and the wheel spins fine but when you stop the the hub from spinning it noticeably slows the wheel. I have emailed Shimano and they have not responded and have had one rear wheel replaced and still the same...slow wheel. Also the ratchet is very muffled when free wheeling not like my carbon Dura ACE which really have a loud ratchet

  10. I bought these wheels about a month ago, and have roughly 420 miles on them. While they are smooth and look great, I experience "pulsing" under braking. LBS has been great, but still unable to resolve the problem. I kind of wish I'd gone with the Easton EA90 SLX instead. Any thoughts Matt?

  11. James-

    Unfortunately, since there are a lot of factors that could contribute to the pulsing feeling you're noticing; it's hard to make a diagnosis without more info. My first few recommendations (which your LBS have hopefully tried - but if not: maybe suggest them) are in this order: Properly adjust hubs, tighten all anchor bolts and quick releases, clean rims, clean brake pads, replace brake pads (I'd recommend Shimano's new R55 c3 pads), then re-surface rim with Mavic rim stone.

    If all this fails - try new brake calipers (if you're not using Shimano calipers which are generally regarded to be the best in the industry).

    I just recently rode these wheels again while at Specialized in California and thoroughly enjoyed them. Not as lightning fast on flats or descents as a deeper section wheel, but smooth, stiff, and light for climbing. I did not notice any pulsing of any sort at any speed (up to 40 mph) on a Specialized Tarmac SL3 w/ Shimano 7900 calipers and R55 c3 pads.

    Without riding your bike or seeing it in a repair stand - that is the best I can say. Good luck and post another comment to update us on your status - especially if you get the pulsing resolved. Everyone could benefit from your experience.

    Thanks again for reading!

  12. Which begs the question - which wheels have you tested where you can use a higher gear on every hill? Thanks Jon (Litespeed Siena)

  13. bandit600:

    Well - not pertinent to this review; but: Bontrager Aeolus 5.0 Carbon clincher and Roval Rapide 45. I'm really curious to try out the 7850-c50-cl (there is a set headed to the store as I write) and see what I think...

    Again, though: a lot of this depends on riding style. I am more of a diesel engine and at 185-190 lbs I am better served by a stiffer wheel; which is usually attained by a deeper rim. Otherwise I'm just winding up the spokes.

    Smaller, lighter riders will be better served by a lighter wheel than I will.

  14. In reference to Collin's slow wheel issue, he needs to put the cassette spacer in. I had the same issue, but resolved mine before it left the stand.

  15. Hi Anon..I face the same problems like Collin's. Can you clarify more regarding this cassette spacer? IMHO this slow wheel issue more to the mechanical in the free hub..i guess.

  16. Matt, could you elaborate regarding Collins matter?

  17. Sorry for the slow reply, Collins and mohizan. Busy holiday season at home and the store.

    Collins' issue is an interesting one. We haven't encountered it on any of the customer or team wheels using this hub that we see at the store. And, I wouldn't expect it to be the absence of the 10-speed cassette spacer. It is clearly not a mal-adjusted hub. It sounds like a freehub issue - but the fact that a warranty-exchanged wheel exhibited a similar issue seemingly rules that out. I'd love to have a look at the wheel - I'll see if I can have a chat with Shimano and come up with a better idea... Keep checking back...

  18. Thanks Matt for the review... these wheels are on my short list for my Rouobaix/Expert. This past summer in the NW they did alot of chipseal on some of my Washington County routes. A wheel that feels like carbon with Alum braking surfaces and light weight sure sounds nice. Is there a difference between the non tube verson and the tube version (not to be confused with tubulars).

    One of your customers/ Nice to read the blog while doing research on the wheels

  19. Scott-

    We've already spoken on the phone; but for the sake of others who may have the same questions, I'll paraphrase our conversation here:

    There is a slight difference. The C24-TL(for tubeless) uses a different rim extrusion in order to make it tubeless compatible. The rim bed (inner wall of the rim) is sealed - lacking the access holes for the spoke nipples - the CL (clincher) has the holes and needs a rim strip. Additionally, there is a threaded adapter and greater reinforcement on the outer wall of the TL rim to allow for a spoke interface. This does add up to slightly greater weight on the TL (about 65 grams) but the ability to run tubeless tires. If I were buying wheels today - I'd buy the TL so that I'd be ready to run tubeless when I decide to make the jump.

  20. Do you happen to know if the adapter is included in the stated TL weight, or is the additional weight of the TL version due to the sealed rim bed?

  21. Bob-

    We've had our hands on our fair share of the CL and TL wheels at the store and there is no "adapter" or Stan's NoTubes type rim strip needed for the TL. It's a sealed inner wall to the rim. The sealed inner wall and slight difference in the spoke interface account for the difference in weight.

  22. Thanks Matt. One more it harder to mount standard tires/tubes on the TL version of the rim vs. the CL version?

  23. Bob-

    I've only just recently begun to hear reports of this. We have not noticed a significant difference beyond the variances we normally see - which I am more inclined to attribute to differences in tire diameters and bead/casing flexibility. I have noted this on other wheel/tire combos and so I've never thought anything of it.

    We have a new set of 7900-TL's coming to the store soon; so I'll pay extra attention this time around...

  24. Thanks Matt. I was speaking with my LBS today, and they seem to think that Shimano is no longer shipping the CL version of the wheels, despite the fact that they still show up in the catalog. In fact, they said that fairly recently they attempted to order a CL version for a customer and was shipped the TL instead. Do you happen to know if the CL version is really being phased out, or did my LBS just happen to get the wrong version?

  25. I have the same issue like Collin had when I got my wheels new.
    1. you need a specer between your 10sp cassette
    and the hub. (the one small ring that comes with the dura ace cassette or similair) My dura ace cassette will rub against the wheel with no spacer.
    2. you will need to lossen the nuts on the axial to adjust the cone/bearing tightness... it came too tight and the wheel won't free spin until you lossen it a will go a little losen left and right.

  26. I'm not sure if this thread is still alive, but I do have a question re: the cl vs. tl models. I purchased the cl before the tl was available, but would now like to run tubeless tires. Are the bead hooks identical? I know the rim bed in the tl is sealed vs the cl which has spoke holes. I can solve that difference with Stan's tape. But will a tubeless tire hook on to my cl rim the same way it will on a tl rim? I'm still a little concerned about coverting a non-tubeless rim. But if the rim profile/hook is the same between the two, then I should be good to go. Any insight would be appreciated.

  27. Rob-
    Good question - especially in light of the increasing popularity of tubeless systems.

    The bead hook is not identical - which is mostly a concern if you're wanting to use any of the "tubeless" tires designed to work with that system (i.e. Hutchinson Atom tubeless, etc...). The TL bead hook is specifically shaped to work with the more "square" bead shape of the road tubeless tires. If you're intending to use a standard tire and sealant, that's less of an issue.

    That said: I don't know what Shimano's standard answer still is on this matter; but originally they were not recommending conversion with Stan's rim strips and sealant on the CL. I'd still say that's the safe bet - especially from a warranty standpoint.

  28. Thanks, Matt. Do you or anyone still following this thread have any experience with a Stan's conversion? Have you had any issues? I'm not concerned about the warranty, and I'm not concerned about difficulties mounting the tire. I'm only concerned about the tire staying securely mounted, especially on the long, fast descents here in the Colorado Rockies.

    Since tubeless rims seem to accept non-tubeless tires, I was really hoping that Shimano used the same extrusion process to build the alloy portion of the rim, and that the only difference was in the nipple interface. But apparently not so. So I am a little leery about the CL rim's ability to hook up firmly with a tubeless tire.

    I know this is not as much of an issue with mountain bike tires since the air pressure is so much lower. And I know you can run almost any mountain tire tubeless with the addition of sealant. But I've read from numerous sources that you can't convert a non-tubeless road tire. So I would definitely use a road tubeless tire in my non-tubeless rim conversion.

    But I'm just a little apprehensive about the safety element. My other option is just buy new rims... if a dismounting tire doesn't kill me, my wife surely will.

    Any insight on conversion would be helpful. Thanks.


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