Bicycle Mechanics - When sanding before patching, how far do you sand down?

I'm a new rider and today was my first experience using patches. I used the Rema Tip Top patches and they seemed to work very well. My question is about the sanding procedure, though.

My understanding is that you need to sand so that the waxy coating is removed from the tubes because the manufacturers put it on to remove the tubes easily from the mold.

When looking at the tube, I can see the waxy layer. But when sanding I noticed that the shiny surface first turns a little white. Then if you sand a little further, that white layer goes away and you get a very dull surface, but can sometimes get a little bit of the rubber from the tube coming off if I go to hard.

My question is, am I supposed to stop at this first "white" layer, or am I supposed to go down to the dull looking layer? For my patches today I went all the way down to the dull layer and boy did they stick well, but I wondered if I went too far and weakened the tube in that area and possibly cause myself future potential problems?

Thanks for the help. I really appreciate it.

-Ryan

I just roughen up the surface with a few strokes. If the patch is on the mould join, I sand away the "flash" to give a smoothe surface.

If the patch is going to fit over the tube's seam, and it most often does, I try to sand the seam down until the area to be patched is even. I would avoid sanding through any layers, I don't recall ever seeing any layers. With the tubes I use if I sanded through a layer there wouldn't be any tube left.

Al

I keep an old fingernail file in my kit. I usually just take off the glossy surface unless I gotta remove the molding ridge which is more often than not. I never run with more than one patch on a tube.

I thought the point of "sanding" was really to roughen the area, to create more surface area for the glue to adhere to? Not really to make it "smooth"? Just curious.

It is to roughen it a bit and mainly to clean it. So just scuff it up a little.

I don't think you should sweat it too bad. You ruff up the tube so you get a better adhesion surface for the glue and patch. I've always just gone back and forth over the hole maybe 5 or 6 seconds, trying to get an area a little bigger than the size of the patch I'm going to use.

Like I said, if the patch sticks and is sealed properly, don't worry about it. You don't need to scuff it up that much though, IMO.

Sounds like you did it right to me.

Well, people make this mistake easily, maybe this will help.It isnt glue per se, its a solvent that for a brief time before its cured dissolves the rubber on the tube enough to bond with the patch.The waxy coating on the tube wont allow the solvent to do its job.If its been roughed up enough to be dull looking your good to go.The mold release on tubes is very thin, doesnt take much to scrub it off, but its thick enough to keep the solvent in the glue from working right.

I found the Park Tools pre-glued patches work real well and I didn't do much sanding past cleaning the surface and scoring it a bit

I don't sand very much, just go back and forth one way a few times, then back and forth perpendicular to that a few times so that the rough spot is just a bit larger than the patch.

I found the Park Tools pre-glued patches work real well and I didn't do much sanding past cleaning the surface and scoring it a bit

Seriously? I've used these twice, and neither one held for more than 10 minutes.

http://www.sheldonbrown.com/brandt/patching.html

>> "I never run with more than one patch on a tube."

Seems a bit extreme, to me. I am not bothered by several patches on a tube.

I found the Park Tools pre-glued patches work real well and I didn't do much sanding past cleaning the surface and scoring it a bit

Those glueless patches are right up there with postage stamps, in my book. The work much better for mtn bike tubes.

[It is to roughen it a bit and mainly to clean it. So just scuff it up a little.]
As an ex tire man, I agree 100% with Avalanche325. He stated the process perfectly.

Seriously? I've used these twice, and neither one held for more than 10 minutes.

The trick is to make sure the area is very clean. Very, very, clean. I use to carry alcohol wipes which I'd use to wipe the area after buffing. Now I just use a Bell tire patch kit from that great American shopping emporium, Wally-World. They're only about $1.50, cheap enough to toss after use (opened solvent usually goes bad after a period of time).

Keep it all in a little pill bottle tucked in my bag.

Rema Tip Top patches are the best in my opinion. I've never had one come loose when applied properly. I'm running one of my tubes on the mtn bike with 11 patches on it :eek: .

I patched my first tube a few weeks ago and hardly sanded the tube, just a bit, larger than the area of the tube. No problems.

Sounds good to me. I just scuff it up some until it looks kind of rough. So far, the tubes I've done like that are holding just fine.

Seconded on the glueless patches, too. I tried those when I rode BMX, and I found they had a tendency to blow out or not stick at all. Rema Tip-Top are where it's at.