Shimano Dura-Ace c24 teardown

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themidge
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by themidge

My rear 7900 c24 gave up the ghost a while ago (rim delaminated around two spoke holes) and I've now finally got round to taking it apart. I thought posting all the weights like this might be useful for someone in the future looking at replacing the rim or something. Safe to say, it's a weird combination of weights!
I forgot to weigh the whole thing, but I found a photo from a while ago (probably a bit heavier due to being less worn):
Image
Not bad, that's a good 200g lighter than something like a Mavic Aksium.
I'll do the boring stuff first.
Rim tape:
Image
Spokes and nipples:
Image
They seem pretty average to me, not CX-ray/laser and alloy nipples weight, but you wouldn't want that on a shallow 20h rear wheel!
Now for the exciting stuff!
This rim is LIGHT, certainly way below any other alloy rim that you could build 20h rear. I think it'd be quite interesting to try to build a set of these rims onto Extralite hubs (maybe still with heavier, stiffer spokes), if they were stiff enough that'd be the ultimate alloy clincher set, good braking and super-light!
Image
The hub is the bit I was really interested in because I can re-use it (it takes normal straight-pull spokes), probably with some aero chinese carbon tubular rims. Unfortunately it's quite heavy at ~80g more than my Bitex rear hub, but on the plus side it has that smooth, sturdy Dura-Ace quality 8)
Image

I haven't dismantled the front wheel yet (because it hasn't broken.. yet :wink:) but I got the front hub's approximate weight by calculation.
610g total - ( 88g spokes x16 + 12g nipples x16 + 356g rim + 16.5g rim tape ) = 137.5g front hub
Also a bit heavy, but again solid quality and beautiful.

istigatrice
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by istigatrice

Thanks for doing this, always suspected the rims were super light and I guess it's confirmed! If only they would make them *slightly* wider...
I write the weightweenies blog, hope you like it :)

Disclosure: I'm sponsored by Velocite, but I do give my honest opinion about them (I'm endorsed to race their bikes, not say nice things about them)

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alcatraz
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by alcatraz

The rim appears quite corroded. Is it?

robertbb
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by robertbb

Wow i wish someone would start a youtube channel or blog, and do teardowns of factory wheelsets.

I'd love to know the weight details of components for Campy wheels.. Bora's, zonda's...

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PSM
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by PSM

Thanx!

Will you rebuild the hubs?

kame
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by kame

I built a set of wheels like that a couple of years ago, for a friend. His 7900 wheel rims were finished but the hubs were still good. I built the wheels with Farsports 50mm carbon rims and DT Aerolite spokes (I may have used DT Aero Comp on the rear DS).
The front was easy, the DT straight pull spokes fit perfectly. The hard part about the rear was getting the spoke lengths right. Shimano doesn't publish hub dimensions. I measured the hubs as accurately as I could and hit the spoke lengths first time right :-).

I can dig up the numbers if there's interest.
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AnkitS
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by AnkitS

robertbb wrote:
Tue Apr 07, 2020 6:47 am
Wow i wish someone would start a youtube channel or blog, and do teardowns of factory wheelsets.

I'd love to know the weight details of components for Campy wheels.. Bora's, zonda's...
https://www.youtube.com/watch?v=S5Hds_3WqDU
Somebody like that?

rollinslow
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by rollinslow

Great teardown! I was just thinking about these wheels yesterday...

I noticed about a year ago that the clear layer over the carbon laminate on the rim is peeling off and have seen this mentioned in a bunch of forums. What do people here make of this common C24 issue?
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themidge
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by themidge

Glad I can be of help guys, I too would be interested in people taking apart other factory wheels, especially since a lot of them have quite good weights even with heavy-looking hubs and spokes (eg. mavic, fulcrum, campagnolo)
alcatraz wrote:
Tue Apr 07, 2020 1:44 am
The rim appears quite corroded. Is it?
It is rather. It's been through several winters and I suppose water ingress under the rim tape causes corrosion :noidea:. Since it's alloy, it's just cosmetic and the reason I think the rim failed was because it was so worn at the brake track.

I definitely want to re-build the hubs onto some chinese carbon (don't really need another pair of mid-weight alloy clinchers), and those farsports @kame built look excellent. They might look even better with silver spokes, which is what i'll go for :wink: .
The hard part about the rear was getting the spoke lengths right. Shimano doesn't publish hub dimensions. I measured the hubs as accurately as I could and hit the spoke lengths first time right :-).

I can dig up the numbers if there's interest.
That would be really useful if you could, I was worrying about this exact issue of spoke lengths. I made sure to take lots of pictures of how the wheel was laced, too, to avoid confusion.
Do you think cx-ray/lasers would be alright for this few spokes, or should I go heavier to keep the stiffness? I only weigh 60kg with rocks in my pockets, but I do ride out the saddle a lot at 60-80rpm up climbs.

bm0p700f
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by bm0p700f

Every time I seen a da hub they are never as smooth as the owner think. Unless it buttery smooth theres no pint in rebuilding.

Cx Ray's would be o.k for a deep stiff rim. Cx sprint would be better. Regardless of how light you are. Stiffer wheels are better wheels in every way.

For spoke lengths use 2.5x and measure the spoke hole centre to center line of the hub. I ha e modified spokecalc to allow a curate calculations. I did post a thread about this once.

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themidge
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by themidge

Alright I finally got round to taking the front wheel apart, again a weird combination of weights but this time I was expecting it!
Complete wheel with rim tape; rim tape
ImageImage
A fairly decent weight for an alloy clincher wheel, now for the exciting part.
Front rim:
Image
Wow this thing is crazy light, and stiff enough to have only 16 spokes too.
Spokes and nipples:
Image

This is the part I was really interested in though, the front hub is the part I can re-use.
Image
Pretty heavy unfortunately, and it isn't super smooth any more, but I'm still going to rebuild it because it's free :beerchug:. The rear is buttery smooth, although it's just as well I can't afford to upgrade to 11 speed any time soon because it will only take a 10 speed cassette.

My plan is to rebuild these hubs on to Farsports 25x38mm carbon tubular rims, that seems to be the best combination of aero, weight, stability in crosswinds, and aesthetics. I'm not sure about spokes though, will Sapim Lasers (cx-ray are £££ :cry: ) be alright for such a low spoke count - 16F 20R, or should I use Sapim Race? Maybe Lasers at the front and Race at the back?

tigradekat
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by tigradekat

I'd shoot for similar gauge spokes as the ones you're replacing, just to be on the safe side. 38mm is not that deep. For 50mm+ rims I'd say Lasers should work.

Dave76
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Joined: Fri Jul 30, 2021 3:47 am

by Dave76

I've been a big fan of my C24 9000-CL wheels and have always suspected I got a light set. Unfortunately I've just had the opportunty to tear down the front after catching it on a flying bike during a group ride crash (rim and spokes trashed).

Here are my weights:
When new - with rim strip but no QR: 594 grams
With 8000 mostly good weather miles: 591 grams (rim wear + perhaps less grease in hubs + maybe some measurement discrepancies)
-16 grams for blue rim strip
-355 grams for rim
-131 grams for hub
-89 grams for spokes and nipples

I have heard the latest 9100 model got a little heavier (anyone measure those/tear down?) and was having trouble locating a 9000-series replacement rim. Finding any gear can be hard/expensive during covid...

Fortunately found a RS-81 rim (should be same as the 9000) and new spokes online for US $223 and $58 respectively so should be back in business soon. Will weigh/post those when they arrive.

In addition - I've seen many report that C24s wear out quickly. As a result I've generally babied mine (if its raining or snowy I ride my other bike and I use soft brake pads like Swiss Stop original black and KoolStop Salmons). Using a dental gauge I'm still at 1.3MM of sidewall, even after 8000 miles. I think when shimano talks about the wall thickness being only .9MM, that must be the part bonded to the carbon rim, and the .9mm metric has scared many away from these wheels....

Of course, this is all ancient history to most, but I ride old (light!) stuff :)
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IMG_4935.jpg
IMG_4934.jpg
c24 front rim thick 1.jpg

tjvirden
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by tjvirden

themidge wrote:
Tue Apr 07, 2020 1:50 pm
Glad I can be of help guys, I too would be interested in people taking apart other factory wheels, especially since a lot of them have quite good weights even with heavy-looking hubs and spokes (eg. mavic, fulcrum, campagnolo)
alcatraz wrote:
Tue Apr 07, 2020 1:44 am
The rim appears quite corroded. Is it?
It is rather. It's been through several winters and I suppose water ingress under the rim tape causes corrosion :noidea:. Since it's alloy, it's just cosmetic and the reason I think the rim failed was because it was so worn at the brake track.

I definitely want to re-build the hubs onto some chinese carbon (don't really need another pair of mid-weight alloy clinchers), and those farsports @kame built look excellent. They might look even better with silver spokes, which is what i'll go for :wink: .
The hard part about the rear was getting the spoke lengths right. Shimano doesn't publish hub dimensions. I measured the hubs as accurately as I could and hit the spoke lengths first time right :-).

I can dig up the numbers if there's interest.
That would be really useful if you could, I was worrying about this exact issue of spoke lengths. I made sure to take lots of pictures of how the wheel was laced, too, to avoid confusion.
Do you think cx-ray/lasers would be alright for this few spokes, or should I go heavier to keep the stiffness? I only weigh 60kg with rocks in my pockets, but I do ride out the saddle a lot at 60-80rpm up climbs.
At your weight (60Kg) CX-Ray/Lasers/DT Equivalents all round will work, but my preference (at 70-85Kg) is for something heavier on the rear drive-side. The offset rear makes a huge difference to the lateral stiffness and is what allows such light spoking combined with low rim weight to be reliable. I still have and use 7900 and 9000 C24 clinchers and I find them utterly superb - as you've discovered, corrosion is their Achilles heel; use them only in the dry and they last indefinitely. Used in the wet they need a bit of maintenance, but it's not onerous. Rim wall thickness (wear from braking) is what kills them then, but even so the lifespan is normal for alloy rims as the 0.7mm thickness is everywhere but the braking surface. Also, using them in a salt (electrolyte) environment, without cleaning them carefully, is a huge no no as the carbon-alloy corrosion is spectacular and very fast.

In my experience, the R9100 C24 is heavier on average and there was quite a bit of variation for the 7900/9000s. The 7850s were consistently the lightest overall.
355g for a rear rim is extremely light - I've never measured one at that and I wonder if the corrosion is a factor.

If you know someone with a lathe, then modifying an 11 speed cassette to fit on7850/7900s is easy - there's a thread on here somewhere. I have only tried cassettes with a 30T, or 32T though. A 28T should be okay.

For me, the best thing about these wheels is the hubs - they're the only hubs I've used that have offered 99.9999% reliability. They also have exceptional bending stiffness, which means much reduced dropout wear.

I also have some Hed Belgium/ Belgium+ rims laced onto Dura Ace hubs, but that's not so straightforward; I'll try to find the time to post about them here on WW.

Best weight weenie wheels ever, for my use (all-conditions braking is a necessity for me).

5DII
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Joined: Sat Aug 09, 2014 7:52 pm

by 5DII

do you guys recommend against reusing these hubs to build to shallow rims? ie, h plus son archetype, etc?

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