Bike Forums - Poor patch quality

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Quote:

Originally Posted by cyccommute (Post 14704010)

You might have that problem on cheap patches using rubber cement. Rema's don't use 'rubber cement'. They use a vulcanizing fluid that is part of the patch/fluid/tube system.

This is correct. There are certain brands of patches you should use and avoid the other brands to be safe. Rema is the best glue on patches and glue available and have been for more then 40 years since I've been riding; and Specialized and Park have the best glueless patches available. Use any other brand of glue or glueless stuff and you're asking for problems.

Quote:

Originally Posted by dddd (Post 14701045)

This was the patch from the other day, Park brand.

Note that the other 3 corners had the same creeping failure, but I pressed on the patch which appears to have re-bonded those failed areas.
Notice also that the tube was buffed fully to flat black, down to the rubber, and that the freshly-peeled patch was repeatedly pressed on with real pressure.

The failures all started at the corners and worked towards the hole, which was not as big of a hole as appears here. A complete failure with air loss did not yet occur, yet from past experience I decided to have a look.
Tugging at one of the corners that I pressed back down shows that a re-bonding has occurred, yet the adhesion doesn't hold up to being inflated in the tire for a few hours.

Note also that this tube measures 26mm wide in a flattened state, fitted into a tire that was nearly, but not quite 27mm inflated width. This is a very normal, middle-of-the-road width ratio for high-performance road bike tubes/tires.

But this is all BS, I'm from the stupid generation, I wiped my forehead with the sticky side of the patch, blah, blah, blah.

http://farm9.staticflickr.com/8038/7...36372d2b_z.jpg

I can tell by looking at the patch you did it wrong!! If you notice the darker center area, that area you pressed on hard for about 30 seconds, but you didn't do that to the corners and edges properly so you got the frosty look because you didn't press it there. This is entirely a preparation failure. When I'm done with my patching they never look like that, they look black across the entire patch.

Quote:

Originally Posted by rekmeyata (Post 14705600)

No, you use just enough to put a thin coat evenly over an area slightly larger then the patch will cover, too much glue and it interferes with with the bonding. And by spreading it on slightly larger then the patch you don't have to worry about the edges of the patch not sticking. And due to the rough surface of the inside of the tire and the material it's made of the tube will never bond to the tire.

I agree that you only need a thin coat of vulcanizing fluid, however a thick coat just requires a much longer drying time. It will still bond if it is totally dry but getting to that point may take a very long time. If you have the glue dripping down the sides of the tube, you've put on enough glue for a box of 100 TipTop patches;)

There's another reason that the TipTop patches won't bond to the inside of the tire. The Rema system is a 2 part system. The vulcanizing fluid contains one part of the bonding agent and the patch is coated with another part. Once in contact, the patch and the vulcanizing fluid start the process of grafting new rubber bonds onto the tube. The tire doesn't contain the part of the system that the patch does and, thus, won't form the same molecular bonding. The vulcanizing fluid may 'stick' to the inside of the tire but it's a weak bond.

Quote:

Originally Posted by cyccommute (Post 14705633)

Great scientific stuff explained in simple terms so we can understand it, thanks Cyccommute!!

Probably why I saw people who used too much glue for a patch have a failed patch was probably due to them not waiting long enough for the glue to dry rather then interfering with the bonding process like I said, but maybe that's the same thing, but regardless, you explained it very well so we could understand it. You have been very knowledgeable and helpful on this subject. Two thumbs up!!

Quote:

Originally Posted by cyccommute (Post 14682838)

The key to a successful patch is more involved with the quality of the patch...*COUGH* Rema...and allowing the glue to dry properly than with the tube itself.

Is there a risk of letting the glue dry too much (I am talking hours, not months)?

No problem, as long as the glue surface doesn't get contaminated by anything like dust. Remember, certain dust particles are attracted to certain materials by static charge or polar attraction.

I usually begin the drying by whirling the glued tube above my head, which shows rapid initial drying.
But, there are thicker spots where the solvent can take at least several minutes to even APPEAR dry, so a good long(er) drying has it's merits.
There is also the matter of the amount of solvent which permeates the tube rubber to the point of apparent swelling, but the visible symptoms of this appear to decrease within several minutes. The solvent is indeed quite volatile. Thinner tubes show a greater, more rapid dimensional change from the absorbed solvent, but appear to normalize within 5-10 minutes.