Shimano 7850 CL 24's - Slow hubs - Help

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 coast 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…help anyone??

EITHER replace the freehub body (if it is the traditional Shimano design) OR if it is the hub type with accessible pawls, then replace the grease with a lighter grease (i.e., try whatever DT Swiss recommends for their Star Ratchet hubs).

There is a Gizmo for flushing the grease out of a Shimano freehub ... I never remember the name ... someone will probably want to jump in, now, to tell you.

7850 is a titanium freehub body, not like the more 'standard' shimano freehubs of 7700 and older. This one, altho bolted onto the hub shell(unlike 7800/7810) has 2 cart bearings in it, not the open 2 row of bearings with 2 pawls in the center, like 7700 and older hubs. Those were essentially a freehwheel body bolted onto the hub body but the 7800 and later series is much different.

Sounds like to me one of the bearings in the freehub is done or in reassembly, one of the seals is out of place, upside down, whatever.

Perhaps the seal in page 2 of this.

http://techdocs.shimano.com/media/te...9830616109.pdf

The bearings are in a retainer on the LH side..upside down? See this.

http://techdocs.shimano.com/media/te...9830648615.pdf

On take apart, are the cones, cups, cart bearings in the freehub body smooth?

Thanks for advice, but the wheels are brand new. My LBS pulled the original wheel apart. Grease was not thick, seal was correct and bearings were all fine so I sent the wheel back and they sent me another. But again when the wheel is spun the spline turns and when stopped it slows the wheel. Thus slowing me down when coasting.....very frustrating problem.

It's normal.I got a friend who works in the factory of Shimano.As far as I know the hub coned bearings is made mainly for durablility not for peak performance.Myself is using a pair of 7850 C50.It's really frusfrating at the beginning.I had been using the wheels for almost 1.5k miles.What I hope is that it could get smoother as time goes on(that is what I heard from the mechanic).BUT!!!I seen my friends using similiar wheels but the spinning is totally different(very smooth).It's very weird.However we got no choice but to slowly get use to this thing.

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I've found Reynolds Wrap on my spoked wheels to get the same aerodynamic benefit of any disc wheel in my Xero.Plus,I can peel it off and bake a potato after my ride. Can't do that with Zipp's. That's value add.

Update - Shimano Aust have been very helpful and have asked for me to send the wheel direct to them and they will determine what the problem is. I have 7800 C50's and they are very fast . stay tuned will advise the outcome

Shimano Aust have actually been no help, they said that is how the wheels come and once I ride them for a while, hopefully they become faster. If I don't like it try and get a refund. They said the hubs have been made for a faster engagement.....this still does not explain why they slow when freewheeling.....THIS IS SO FRUSTRATING.

Hi Col

Have you tired to return them to the shop you brought them from?

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Steve
CyclingForums.com

But it does, at least for the rear wheel. Faster engagement means that they want the clutch mechanism to lock down faster, for a lesser number of degrees of crank movement. This in all probability requires more parts, stronger preload or something else that increases the friction in the unit when coasting.

Yes, have already had one replaced. They sent me another but that was the same, SLOW. But problem is there is nothing wrong with the front. So if I get refund on rear, I am stuck with the front wheel...another front wheel in the garage!!!. Will try and "ride them in" as suggested and see what happens.....Just was keen to have them as my fast race set of wheels...just disappointing.....will look at getting a set of Mavics instead.

Not much use when you drift off the back of bunch when you have done your turn and are freewheeling at the back of bunch

Presuming a tyre isn't rubbing on the rim OR the brake pads aren't rubbing on the rim (!?!) AND because the hub is a variation of Shimano's standard rear hub, I guess your best option is a DIY servicing ...

FIRST, I would try replacing the grease with an even lighter grease ... either, straight WHITE LITHIUM or White Lithium cut with a drop of 30W oil ... there are even lighter combinations ...

Bearings packed with lighter grease need to be repacked more frequently.

If THAT doesn't help, remove-and-replace the actual FREEHUB body with one from a 9-SPEED Tiagra hub (Why pay more? The hub will have to be laced to a rim to remove the freehub body). Yes, a standard Shimano freehub body will weigh more than the Ti freehub body, but not that much more.

Tiagra-steel axle, 7850/7900-oversized aluminum axle. Freehubs not compatible, for info.

IF the cups are a different size, then swap the cups from one freehub body to the other.

??

http://techdocs.shimano.com/media/te...9830648615.pdf


http://techdocs.shimano.com/media/te...9830608911.pdf

Hard to tell from the docs but I would be surprised if this is possible..but then, anything is 'possible'. But I'll bet the ID of the big bolt that holds the tiagra freehub onto the hub shell is not big enough for the DA hub axle and the DA bolt won't work with the Tiagra freehub...but.......