I have 2 sets of ultra ultra light Mavic R-SYS SL front road wheels.
How light? Well the Front rim, without tyre (150 grams) or tube (60 grams) or skewer (40 grams) is only 560 grams in weight. And for a non tubular wheel you cannot get lighter.
Trouble is, that when mounted on the bicycle you can wobble the wheel left and right towards the brake pads by about 1mm. So something is loose. And when you are high speed cornering down a mountain pass you really don't want a loose, wobbly front wheel, or any wheel.
With black belt Googling skills I downloaded the Mavic service manual. I was surprised to find that for my wheels there is just a parts diagram but absolutely no instructions on how to service the wheels.
One of the wheels is quite wobbly, the second is just a fraction wobbly. In fact a friend in the bike trade said that these wheels are very fragile and it could 'just' be the play in the carbon spokes combined with early bearing wear.
2 years ago I tried to take the wheels apart and failed. There seemed to be no way to remove the skate style cassette bearings. I gave up and put it back together. Since then I've used these front wheels sparingly.
Attempt#2: To the Shop
I took the wheels, and Service Manuals to a local bike shop in Pully Lausanne. In view of the following comments, and with the nice guy that I am, I will not name them.
Initially they were reluctant to repair the wheels because I did not buy them from their shop!
I explained they are a Mavic dealer and I expected to pay for the repair. I asked could they replace the inner bearings please.
They charged me over 100 GBP (150 CHF) and 2 weeks, and they really claimed to have replaced the bearings.
I tested the wheels. Both still had the same problems: 1 wheel quite loose, the other wheel just a tad loose.
In view of the following paragraph, in retrospect I believe they did absolutely nothing. I warrant that they did not replace the bearings, at most they re-greased them, and ripped me off. Thanks for nothing.
Do It Yourself
The centre spindle just pulls off. The edge components are carbon fibre. The wheel has 2 bearing races one of each side of the hub, and they just sit on the silver areas you see here.
Oh and the bearings are not as we had thought industry standard skate sized bearings but some weird size :-(
Technical note: AFAIK These wheels don't have the QRM SL Hub bearings that can be removed with a large mallet.
Amazingly the service manuals from 2010 onwards tell you how to replace the Bearings for many other types of wheel, there is even a reference to R-SYS SL replacement in the manual. But when you reference it, it is not the R-SYS bearing at all!! (Photos to prove it here:)
So we just did the trivial re-assembly. And I still have 2 sets of wobbly wheels.
I have lost faith in Mavic ultra light Road wheels. Though they are the lightest, being IMHO in practice user unserviceable renders them use and discard. That is both too rich and too wasteful to me. I never thought I hear myself say: Back to that 'plain old' Shimano Dura Ace for me in the future. But that about sums it up :-)
Fear of Carbon