Patching Butyl Tubes - Problems
 

Forgive the posting in C&V, but I am afraid the activity of patching a butyl tube is most likely considered anachronistic by most modern cyclists.

I have always enjoyed patching tubes. I don't get flats terribly often, maybe 4 per year. I typically save up punctured tubes and "batch patch" them in the winter. HOWEVER I have noticed a big change in the past few years, and I wanted to know if others noticed this too or if any ideas/suggestions.

Up until about 5 years ago, I had a "success" rate of patching of about 9/10, in other words nearly every patch worked fine. Sure, 10% would not adhere right or just not work, but 9/10 is fine and that was consistent year after year. Now it's the reverse. Nearly every patch fails. It seems the patches are not sticking well at the edge/margin of the patch. It's infuriating. I am using the SAME brand patches and vulcanizing fluid (Rema Tip Top) and the SAME technique. I am even using a stupid tool I bought to try to press the patch to the tube with more force (figuring with age maybe my finger strength got weaker).

My only guess is something has changed in the butyl they use for tubes or I got a really bad batch of Rema patches (I got a box of 100 of them).

I am close to giving up on patching and just tossing tubes like most people do.

Any comments/suggestions??

I have stopped patching and setting them aside for later because I too was seeing a high failure rate. If I patch a tube it is immediately placed inside a tire and inflated, based on the idea that the constant, even pressure from the tire "seals" the patch more effectively. I've seen much more success this way. FWIW.

So the routine:
New tube gets used on the road for quick puncture repair.
Punctured tube is patched and re-inserted into tire at some point before the next ride.
Spare, unpatched tube goes back into saddle bag for next time.

I think is has to do with "toluene". The newer vulcanizing cement often does not even smell the same as it used to. Ha... Ask any Huffer. Other solvents and adhesives that use aromatic solvents for their bond are suffering too. Note that Testors styrene model cement and even plumbing PVC Cement is nothing like it was 8 years ago.

Sure, allot of these solvents and aromatics are dangerous or even now deemed carcinogenics. So what do we do? We hoard those old unopened containers of vulcanizing cement in the frig in hopes they do not evaporate in their unopened tubes... Ha

I place the patched portion of the tube on a flat surface and lay a 25lb flat weight on it for a few days.

Noticed that also. I've gone to using a little more glue and letting it dry longer.

When patching an innertube be sure you hit the area around the hole with the sandpaper that's usually provided in patch kits. This abrad3s the surface of the inner tube so there's tooth to the surface that the glue and patch can adhere to. Make sure the a raded are is slightly bigger than the patch so the edges of the patch can adhere to the innertube.
Before applying the patch glue on the inner tube, make sure you clean the innertube's surfacce very well so there's no dust, moisture or sand on it.
This is the step that most people fail to do, which results to the patch not totally adhering to the innertube.
I never had a patch fail on me all the years I've been cying, using the procedure above.

I have found a bit more glue, a little more time to dry, and I think humidity affects that. In warm, humid air, I will put a bit of weight on the patch while it dries, Not fact, but to me, it seems to help. Glue used for patching is a challenge in keeping it usable. The tubes dry out too quickly, once opened. It takes a whole lot of patching to use up one of the larger cans before it starts to thicken to where it cannot be used. Maybe someone has an idea on how to prevent that.

I thought I was being stingy with the glue. Lately I've been tryng to remember to put more glue and on a larger area. AND sometimes, I leave the slick clear cover on so as not to disturb the edges

Don't forget there is mold release agent on the tube that must be removed prior to applying adhesives.

My success rate is still pretty high, but could it be from patching the same old tubes that it always worked on? ;)

Lots of good tips so far!

Glue must be completely dry or will not give good adhesion.

I abrade pretty deeply, until a consistent flat-black appears. A lot of work.

I apply the glue with plastic bag wrap stretched over my fingertip.

And my one particular discovery came when I was studying the "failure mode" some 1990's, rather stretchy and "foam-like" glueless patches, but what I learned applies to glued patches to some degree as well:
The tube should not be in tension from inflation pressure any more than perhaps to round it out, when the (normally stretch-resistant) patch is applied!
Otherwise, as the tube is inflated and conforms to the inside of the tire, there will be continuous residual tension in the rubber surrounding the hole. This is because patches (with the exception of those first glueless patches) are stretch- and compression-resistant, meaning that a stretched tube adhered to a patch will remain stretched in tension. A proper patch prevents the local repaired area of the tube from stretching during inflation!
Having residual tension in the wall of the tube adjacent to the puncture will allow the tube to slowly start peeling away from the patch, starting at the hole where air can enter, then migrating to the outside edge of the patch (creating a complete pathway out of the tube).

Oh and one more thing, that I noticed about 22 years ago, was that at that time many tubes started showing a different material property during sanding. Instead of falling free from the tube, the sanded-off rubber seemed to stick around in little rolled-up lengths of rubber material that seemed "gummy". Adhasion on those particular tubes was extremely poor, and I began tossing those upon first puncture. This reformulated butyl may still resurface from time to time in certain batches. At the time, I thought it might be a plot to force purchasing more tubes instead of replacing, or in today's context maybe forcing us all to use more-expensive tubeless tires. Conspiracies abound.

Certainly also, the glue has become ever less toxic/polluting over the years, and so like most of today's contact cements, not so aggressive at etching into the base surface.
For this dilemma, I use a little more glue thickness upon application, so that the solvents have longer to work before becoming too dry to spread around.
This last technique especially applies to using older, thickened glue (given added work time, the solvents will still do their job effectively!).

That's all I got.

Inquiring minds want to know--do you tear off the thin plastic outer-most layer on the Rema patches?

I have both generic rubber cement and Rema fluid, and honestly I find the generic rubber cement has Better adhesion around the edges.
But I do find that success rate vary greater with different tubes

Make sure your glue is completely dry. You can’t wait too long. I’ve forgotten about patch jobs for more than 2 weeks. Still worked.

Make sure you remove the mold release compound completely before apply the vulcanizing fluid.

Use more fluid than you think you need. Don’t starve the adhesion layer. There’s a chemical reaction going on and it needs enough chemicals to make the adhesion work.

Perhaps most importantly, don’t “test” the patch by filling up the tube and stretching the patch just after application. Let the chemistry work for a good long time. Trust your patch job.

I used to remove the thin, clear plastic bit. Now I leave it on. For reasons unknown.

I have a big jar of Slime rubber cement and slather that on liberally after a light abrading. I put on the patch and then lightly clamp in my bench vise until I remember to take it out which is about 1 day or a week. Very low failure rate, also use Rema patches. I take the plastic bit off but have thought about leaving it on quite a bit but I think the Germans would disapprove.

Germans make Rema patches right? That would be a weird post if they didn’t, in which case I apologize.

Leave the film on. If the tube is in some brands/models of tires for an extended time, patches without film can stick to the tire.

Trigger clamps do the trick for me. Pressure can be applied right on the patch, and the clamp and tube can be hung out of the way the tube dries. Plus even the small clamps apply 100psi pressure.


https://cimg7.ibsrv.net/gimg/bikefor...a739c60e3.jpeg
Thanks DeWalt for photo

And most here biotch about tubulars. Haha

My next round will get a wipe down with nail
polish remover (I can’t remember the name of the chemical. Sad.) first. I’ve been having a zero percent success rate these past few years. I bought a new tube of glue today, and use Rema patches

Xtra Seal rubber buffer and they have a rubber adhesive- bigger sized bottles but cost per fl oz is reasonable.
‘for professional use only…

once the Cal OSHA becomes aware… bye bye

It is acetone or in some brands a less effective remover. I use pure acetone to finally clean the tube prior to Rema, works well.

Plain old rubber cement, Rema patches and a trigger clamp. I leave it clamped overnight, but I'm sure that's not required, I'm just asleep.
Just patched 2 last night and they're both great today.

Maybe it's just luck, but I have put literally hundreds of patches and maybe 3 or 4 failed. I even overlapped patches, used tubes with 20 patches on them, no problems. My method is simple:
Start with clean hands.
Locate the puncture and draw with a pencil a sort of of crosshairs with the hole in the center, to aid centering the patch later.
Sand very thoroughly with 60/100 grit sandpaper an area about 1 1/2 larger than the patch. This is the step that takes more time, I like to achieve a clean, fully matte area and erase any ridges or molding lines. Wipe clean with the back of your finger.
Apply a thin layer of cement (with my clean finger) and let dry 3 to 5 minutes. It should be fully dry before applying the patch. If in doubt about the tube "patchability", I apply a 2nd layer and let dry another 3 - 5 mins.
Peel the patch carefully taking care the edges doesn't curl and apply without touching the contact surface.
Press hard on the patch - preferably with a roller, but not really needed. You can use a screwdriver handle, or any similar tool, even your thumbs.
That's it. You can use the tube immediatly, in fact probably the air pressure helps in pressing the patch.

I'm so glad this post was made, I thought it was me getting worse at patching tubes. Thanks for all the great advice!