Can I RTV minor boot nicks?
 

I accidentally cut small smiles into the CV boots of my new half-shafts. {expletive deleted}:(

A friend suggested a clean up with alcohol and using some RTV.

Is this the best approach, and can anyone suggest the best RTV? I don't know if the boots are silicone rubber but I suspect it matters.

The bolts were a semi-blind insertion, and when I'd suspected what I had done, I removed the shaft and inspected it. I did the other by depressing the outer rubber and slipping the bolts into the CV.

Thanks very much,
Dan



http://forums.pelicanparts.com/uploa...1418509715.jpg

Dan, Super Glue works much better on rubber than RVT does - the glue is not flexible, but the rubber around it is, so no problem there. I've used SG to repair CV boots in the past and the repairs held up for many years with no hint of a problem.

Looks like you're in a spot that sees very little flex. Anywhere else and I would have said no way to bonding as there is too much movement and rubbing.

Thanks Ron - I never heard of that. Do you mean the original (super Glue corporation) or a Loctite version? Rubber wasn't mentioned on the (original) super glue site.

Dan, yes the original Super Glue. I have an unopened package of it here that has an application chart on the back, and it lists the liquid version (as opposed to the gel, which is labeled "good") as "best" for rubber. I've used it on all kinds of rubber, including rubber strips glued together that are under a bit of tension, and it stays stuck.

One other thing worth mentioning is you don't want to "paint" the areas of your tears with the stuff - just get it into the cracks and let it sit for a day or so before moving it.

Also, RVT is ok on rubber parts that are not going to move, but it has no real bonding strength (more of a sealer) and will come off the surface if the parts move very much.

go to a hobby store and get a bottle of CA glue. Its just really good super glue. a common brand is great-planes

Do yourself a favor and replace any boot you have damaged......

Sounds good. I'll let it wick in and test it in day.

Thanks for the info Ron

It crossed my mind but is this really a practical solution? This isn't a wear point, and the nicks don't penetrate. I am trying to save myself from tearing apart a brand new CV. If I can do something that will last 4 or 5 years, I'd rather take that path.

I used RTV to repair a CV boot on the front of my wife's van. It was cut an leaking. It was a b!tch to remove it so I figured I had nothing to loose.

I made sure the CV was VERY clean where I did the repair. It still hadn't started leaking again two years later, when I sold the van.

In another life I worked in a machine shop that built control valves for liquid processing, including nuclear power plants. Part of the QC process entailed pressurizing them to, in some cases, 7500 psi. Parts of the test rig used o-ring seals. Due to the plethora of sizes of valves it was impractical to stock the hundreds of required o-rings so we simply had long rolls of rubber string if different diameters and when a certain rig would come up, we'd cut a length and super glue the ends together. I never had one separate, even at 7500 psi.

Based on that experience I've superglued "smiles" as you call them in both bicycle and motorcycle inner tubes and had them hold pressure for hundreds, possibly thousands, of miles.

Get the boot absolutely clean. Pinch the "smile" so that both sides of the tear are side by side. Run a bead of super glue along the two sides, then relax the pinch so that the sides mate without any tension or pressure. Someone suggested sitting over night. In my experience it's not necessary. As soon as the glue sets up the bond will be as strong as it ever will be.

Good Luck.

Maybe super glue is better now. I won't use it anymore due to the fact that it has little resistance to moisture and over time fails. I got tired of things I superglued falling apart after a year or two. Perhaps it works on o-rings since they are not exposed to air. YRMV.

edit: apparently it is better now and it has additives to counteract its failure over time, at least according to Wikipedia.

I think it's lack of flexibility my be a issue on rubber though. Try it and report back.

Why not take the belt and suspenders approach: super glue the cut, wait until it dries, then cover it with black RTV silicone. Personally, I don't think the RTV will fail, but if it does, the super glue will still hold.

I agree with david's approach. Superglue the faces of the nick together, and then as jflex suggested, RTV over the surface. I think this makes sense give these small nicks won't manifest into large holes anytime soon. CV books need replacement every couple years it seems...these aren't there yet.

If you had larger holes in them already you'd want to replace the boots and remove the old grease and debris--but that is not warranted here.

Do people still repair bike tires with those old tire patch kits? Just an idea for a temporary repair, otherwise, do the prudent fix and forget it.

Can I RTV minor boot nicks?
 

Did you ever build model airplanes, cars?

Do you remember the good old fashioned glue? You ever try to use the stuff that's available now, due to the intoxicants in the old stuff?

Well, superglue works on rubber like the old glue worked on the plastic. It actually melts it and bonds it back together like welding melts steel and bonds it. You'll notice that, unlike other materials, if you get a little one your finger it will be black from the melted rubber.

So, I'm guessing flexibility won't really be an issues because the rubber is actually bonded together. Like I said, I've put thousands of miles on motorcycle tubes that were superglued back together after I'd pinched them while mounting them. AFAIK, the only thing that would compromise the joint is if it weren't perfectly clean.

I had that problem once, rubber was cut but none of it missing. I got underneath with a soldering iron - waited 'til the temperature was right - rolled the tip across the split. The "rubber" flowed and resealed itself perfectly. Never had any trouble with it after that for as long as I owned the car.

When CA adhesives first became available model airplane enthusiasts were very skeptical. One of the model magazines (I think RCM or Scale Modeler) did an article about their tests covering the new adhesives. They covered ultimate strength, durability, different materials, quantity of adhesive to use for the best bond, and how the capillary action worked spreading the adhesive so users could better understand how to use them.
One of the interesting side stories was that they had a large chunk of rubber torn out of the corner tread of a trailer tire while they were on a cross country jaunt. They were in spot so they said 'what the hell' and used the CA to glue the chunk back in. The adhesive didn't fail and after the tire had worn a bit they could no longer see the glue seam on the tread surface. Not a recommended tire repair but quite an example of what the CA adhesives are capable of.

The super glues you find at a normal store are not the good ones. Almost across the board they are only for non porous surfaces. Go to a hobby shop and get a quality glue like Zap or Kwik Bond. There are different types including thicker CAs to bridge gaps, CAs for plastic, CAs for flexible bonds, etc. You want to get the thin plain old CA. You want the capillary action to make the thinnest bond possible so use the smallest drop and some saran wrap so you can press the tear closed and hold it for about a minute.

If this doesn't work use a tire patch...

I say replace it if thats the original boot you should replace it anyway (a good excuse to repack and re lube the CV joints). The boots are not that expensive and will give you piece of mind (and a weekend project).

If you don't want to replace them I would opt for the soldering iron option as thats what I would do.

Regards
Dave

One more warning about silicone sealants (RTV) is that silicone is not very compatible with most oils, and certainly not with fuels (unless they are formulated with fluorine). Buttoning up a small knick is probably OK, but with anything significant you should replace the boot.