Glue edge separation on rear

Everything about building wheels, glueing tubs, etc.
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Alexandrumarian
Posts: 192
Joined: Mon Mar 28, 2016 6:34 pm
Location: Romania

by Alexandrumarian

My first tubs were black sides, maybe one reason I didn't notice this sort of thing. I used Conti carbon. When the rear was due for replacement it came off way too easily so I switched to Mastik. Did 2+2 layers, final 5th, using a full tube per wheel. For this second time I switched to tan sides Vittoria 23 (wheels ar 24mm Bora). After a few rides I noticed the rear started to separate at the edges but when pulling on it it was still glued and seemed rather OK. When it was time to change, i had a much harder time pulling it off. Same sections were coming off easy but others not so. Overall felt pretty well stuck. I wouldn't want to fight it more on the side of the road.

And third time I installed Vlaanderens again with Mastik and again after a few rides I see the same splitting happening over most of the rear wheel. Front wheel looks perfect. In the Vittoria 23 I had 8 bars, in Vlaanderen ~6.

Wondering if it is normal or something off with my procedure. The rims were perfectly clean and degreased, basetape lightly sanded, 12h dry time between thin layers, 5th wet. As you might see in the second photo, past the rounded edge of the rim wheere the flat section begins, there is plenty of glue and it is stuck. The thumb test is done with a softened tire, about 2-3 bars in it.

Thanks
Attachments
glue1.jpg
glue2.jpg

mattr
Posts: 3677
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Did you key the rim as well?

by Weenie


Alexandrumarian
Posts: 192
Joined: Mon Mar 28, 2016 6:34 pm
Location: Romania

by Alexandrumarian

Only first time when it was new. Following sessions I would remove all old glue with a combo of naptha and mechanically then wash with pure alcohol. I see glue leftover on both carbon and tire so i suspect the splitting happens simply becase there is a gap there as the tire is round but rim bed a flattened V. The rear wheel takes more load which might explain why the front looks good. Being a heavy rider might be another reason. Same glue job might look betweer with a 60Kg guy? Other than this they seem to be well stuck and I already used them during steep descents (same for the previous tire which did the same) But it looks bad.

sungod
Posts: 1638
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

the bond with conti glue is not as strong, but you switched so at least that problem is solved

hard to tell from the images, how far in does it go? if it is only the shoulder of the rim where it curves away from the rim bed then that would be normal, but if it's coming away from the inner part it's a problem

is it one glued surface separating from the other? i.e. not that the glue is peeling off the rim or the basetape?

if the glued surfaces are separating, with the 23mm on a 24mm wide rim i'd suspect that the tub is a bit too narrow to match the rim bed profile, so the centre will be stuck firm but the edges can life away - but that would not apply with the vlanderen

if the glue is peeling away from the rim bed, assume the rim is contaminated, try remove all glue, go over the rim bed with 0000 steel wool, then degrease with acetone one a new piece of cloth 2-3 times

Alexandrumarian
Posts: 192
Joined: Mon Mar 28, 2016 6:34 pm
Location: Romania

by Alexandrumarian

I would say it is just on the shoulder plus a bit deeper, exactly where without glue you would see a gap even with the wide tire. After install that gets nicely filled but thick glue is not as strong as thin, add some squirming from a heavy rider and it might not be too strange after all. In the second pic you might see that deeper in there is adhesion and the finger pressure lifts a sort of wall of glue strings.

I did not notice this sort of cracking on the Conti glue job but with black tire it is much harder to spot, while on tan it just jumps. When i pulled the Conti glue job, it had a dry feeling to it. I saw separation between layers with leftover on both rim and tire, or separation from the rim. Rim leftovers were super easy to clean, just hit then with a hairdryer and roll peel it with no effort.

In contrast Mastik remained rather soft. Trying to peel it off more like smears it around (same with heat) rather than letting go from the carbon. In the end I had to do a lot of naphta soaking and rubbing. When I pulled the Vittoria tire I had to use alot more force. Most glue stayed on the rim and the base tape teared in several areas. So again it seems it is a solid job deeper in.

sungod
Posts: 1638
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

sounds like it's probably ok, i'd check every so often just to see if it gets worse

to remove glue, schwalbe glue remover is very good, far easier than naptha (and a lot safer!), and though i've not tried it the carogna glue remover is also supposed to be as good or maybe a bit better

Alexandrumarian
Posts: 192
Joined: Mon Mar 28, 2016 6:34 pm
Location: Romania

by Alexandrumarian

I deflated the tire completely and pressed hard all around. Seems to hold fine. I guess I got worried too easly but hey, who wants to lose a tire when going downhill?

Next time I'll try to tape the shoulder too not just the brake track. Should result in a cleaner job with no thick bead to crack later.

Will definitly try the Schwalbe or Carogna, naphta was beyond slow and tedious. I skipped on them knowing how easily Conti went away, only to have a huge surprise with mastik.
Attachments
glue3.jpg

by Weenie


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