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Dura Ace 7850 weep holes preventing tubeless mounting

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Dura Ace 7850 weep holes preventing tubeless mounting

Old 01-08-19, 12:39 PM
  #26  
masi61
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Update for Tuesday, January 8th 2019:

I don’t think running these without sealant is going to be advisable. The Hutchinson Fusion5 All Season 23mm tire did inflate well with my Airshot last night and it was not hissing detectably when first mounted without sealant. The initial pressure was like 77psi, later last night it was 55psi. This morning is was 25psi and then “zero” when I adjusted the valve locknut to place the little asymmetrical shim on the valve that contours to the offset rim then allows the presta knurled nut to tighten down squarely.

So I did a bit more archival bike forum research - reading some good discussions on road bike review from back in 2010.

I went ahead and used my Stan’s syringe and put 30ml of regular Stan’s sealant under the bead which I pushed away from the rim sidewall. I tried to guide the hose into the interior of the rim. It mostly worked. I rotated the wheel about 180 degrees and back then gave it another 160psi shot from the Airshot. Nice. Everything buttoned up leak free immediately again. This time there was some splatter of Stan’s. I took the wheel/tire to my utility tub and gave it a spray of warm water and the liquid Stan’s washed away nicely. The tire now is holding about 78psi again. It is odd but the wheel does seem heavier slightly as you can feel the sealant rolling around. I will recheck the pressure tonight and again tomorrow just as a learning experience.

Riding these early tubeless wheels is going to be fun. I have been riding pretty heavy 36 spoke front and rear touring clinchers on my road bike for about 10 years. Last year I started to get the bug to get faster wheels - ...
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Old 01-10-19, 07:18 AM
  #27  
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@masi61, how is the pressure holding today? Seems like quite a battle to get the reliably sealed to the rim. Have you ridden them yet? If you have, do you think the ride is worth the effort?
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Old 01-10-19, 08:07 AM
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Originally Posted by speedevil View Post
@masi61, how is the pressure holding today? Seems like quite a battle to get the reliably sealed to the rim. Have you ridden them yet? If you have, do you think the ride is worth the effort?
Thanks for the interest!

The rear is holding air well now.

The correct Shimano (front) valve will be delivered any day now. Im more confident that the front will hold air as it should & the process is now less stressful to me,

No I have not ridden them yet, but I will be soon.

This inexpensive Klein Quantum is going to fly I suspect, & I will most definitely post a road test report once I do!


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Old 01-24-19, 06:04 PM
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Update on the 7850 front wheel:

I installed the correct Shimano front valve which does seal better than the generic ones I had been trying.

But it still does not allow my Hutchinson Atom tire to mount.

I had been holding out and not taking it to the LBS thinking that I could resolve the issue.

But today I took it to the LBS & they were unable to get the tubeless tire to inflate.

So he removed the tire & looked carefully @ the rim and it turns out that the interior rim shelf has a 2” crack in it!

He suggested I photograph it and send a picture to Shimano & see if they can do anything for me.

in the meantime he said to put one layer of tubeless tape to cover the rim crack & see if this allows the tire to mount & hold air.

if anyone knows the process for contacting Shimano -i’d Like to know...


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Old 01-24-19, 06:38 PM
  #30  
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Crack on the front rim!
I would get rid of it.
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Old 01-25-19, 07:14 AM
  #31  
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Have your local Shimano dealer contact them. It takes a week or two for a Shimano rep to examine the product for a claim. However, since those wheels are way out of warranty and they have had sealant in them I wouldn't hold my breath.
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Old 01-26-19, 01:33 PM
  #32  
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Here you can see where the crack is more like 3 long (not just 2 as previously stated).



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Old 01-26-19, 01:39 PM
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Well, that sure explains the loss of pressure. I can't see how that is anything but a manufacturing defect. How it will be handled is a different question, but I hope that the problem will be resolved properly and promptly.

Depending on the response you get, I would be tempted to try some kapton tape, at least a couple of wraps around the wheel, to see if that might allow it to hold pressure. Narrow tape should not interfere with seating the beads.
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Old 01-26-19, 04:21 PM
  #34  
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Originally Posted by speedevil View Post
Well, that sure explains the loss of pressure. I can't see how that is anything but a manufacturing defect. How it will be handled is a different question, but I hope that the problem will be resolved properly and promptly.

Depending on the response you get, I would be tempted to try some kapton tape, at least a couple of wraps around the wheel, to see if that might allow it to hold pressure. Narrow tape should not interfere with seating the beads.
Yes, I sure does explain the inability to maintain pressure.

I wonder how many mm of Kapton tape that would be. I have some in 18mm which sounds like it would be too wide. I knicked my Hutchinson Atom's square bead with a (plastic) tire iron and now there is a small cut in the square bead. I may have to kiss that $50 tire goodbye. This has been a real learning experience. Is there anything I can do to still run this tire tubeless?
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Old 01-26-19, 04:45 PM
  #35  
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@masi61 - never having mounted a tubeless tire on a bike, I'm definitely not the person to ask. I would think that sealant would prevent you from tossing the tire, but I have zero experience to back up that WAG.

I think I have some 16 and 19mm kapton tape - having used it I prefer it to velox cloth tape. I would be tempted to try a small piece, maybe a foot long, and see if that works. One problem is that the tape's adhesive needs to hold in the presence of sealant and I don't know whether the two are compatible. That's why I suggested a couple of wraps. If you start past the crack and wrap towards it, after one layer you'll actually have two at the crack. Continuing on, this time past the crack, you'll wind up with three.

Since not all rims are built like yours, some rim tape must work with sealant or rims with spokes holes could never be sealed reliably. Hopefully someone with experience can chime in.

But maybe, Shimano will just replace the rim and this discussion will be moot.
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Old 01-26-19, 05:00 PM
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You didn't notice that crack when you acquired the rims?
You might have been the one to crack the rim.. over-pressurizing from your previous posts.
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Old 01-26-19, 06:09 PM
  #37  
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Originally Posted by trailangel View Post
You didn't notice that crack when you acquired the rims?
You might have been the one to crack the rim.. over-pressurizing from your previous posts.
I bought the wheels sight unseen in an eBay auction.
I inspected rim and totally did not notice the crack.
No, there is no way that this rim was overpressurized by be since I never managed to get any tubeless tire to mount on it. Any excess of air from my Airshot canister quickly blew out the the 2 weep holes. Same result with my air compressor. No way I could have overpressurized it. This was a pre-existing crack from the previous owner. Unfortunately the eBay seller was "piermont bike". They have a selling format of auctions that start at $0.99 with no reserve, so auctions from can end with fairly low selling prices.
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Old 01-27-19, 02:01 PM
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I hate to harp on this issue, but based on my experience with the later versions of the 7850s, it looks like the crack "walks" along spots of corrosion. Some will speculate that the corrosion came after the crack - who knows - they may be right. My fallback is that Shimano specifically states not to use alkaline sealants, and considering the source on these wheels, they may well have been subjected to such a sealant, which could lead to the issue you are having. I do not think this is a manufacturing defect. The crack is too irregular. Botton line - the rim is toast. And the seller probably knew about the crack. Any amount of normal pressure (even with a tube installed) is going to open up the crack, it is going to continue to walk. Considering that it is a front rim - I would not take a chance.
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Old 01-27-19, 03:40 PM
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Originally Posted by Vince Canepa View Post
I hate to harp on this issue, but based on my experience with the later versions of the 7850s, it looks like the crack "walks" along spots of corrosion. Some will speculate that the corrosion came after the crack - who knows - they may be right. My fallback is that Shimano specifically states not to use alkaline sealants, and considering the source on these wheels, they may well have been subjected to such a sealant, which could lead to the issue you are having. I do not think this is a manufacturing defect. The crack is too irregular. Botton line - the rim is toast. And the seller probably knew about the crack. Any amount of normal pressure (even with a tube installed) is going to open up the crack, it is going to continue to walk. Considering that it is a front rim - I would not take a chance.
thanks for taking the time, even though I was hoping for better news. I didn't pay much for these wheels. It is a bit of a disappointment because the rear wheel seems fine with the installed sealant and the Hutchinson tire installed.

I'm still going to forward the photos to Shimano - I'm not expecting much, but thought maybe I would get lucky and they would have a surplus of these old 7850 rims, that they could send me at a reasonably (below $80?) low price point. I mean maybe they'll replace it for free as a courtesy. Who knows?

I'll post an update when I find out. there is a single 7850 front wheel currently on ebay but they are asking as much as I paid for this wheelset.
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Old 01-28-19, 02:45 PM
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Update for Monday, January 28th - I called Shimano and they are not going to be able to help me. The item is out of warranty and replacement rims are not available. Since my rear wheel seems to be OK, I may try to acquire a used matching front wheel at a reasonable price (say under $100 with shipping?).

But in the meantime, just out of curiosity I was going to try to apply a bead of metal epoxy (AKA “JB Weld”) over the crack just for the hell of it to see if I can get this thing to hold air tubeless.
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