What would cause a leak between tire and rim?

Credible Hulk

Active Member
I'm still in hell, trying to get my lemon ebike to work. I thought I had it all ready, both wheels back on, gears and brakes working, new rack installed, etc. Then today I found the back tire flat again. I had installed a new rim liner and a new Slime tube, even though the old tube has held a partial inflate for almost a week now. There was never any sign of damage to the tire.

I was able to figure out where the leak is coming from, it's a small 1" area where the tire meets the rim. Both tire and rim appear fine. I don't want to waste more money on tubes and tires until I know what would cause this. If it's the rim I'll have to go after the ebike vendor (again) because the whole rear wheel including motor will have to be replaced.

Could it be something simple like a twisted/wrinkled tube? Or is it a problem with the (steel) bead of the tire?
 

PDoz

Well-Known Member
Sounds like you pinched the tube between tyre and rim when installing it? Partially inflate the tube before you lever the tyre on . Apologies if you already knew this , but surely if there was a rim or tyre issue you'd be able to feel it?
 

ebikemom

Administrator
Staff member
The rims also have perforations in them (inside the rim). These can be sharp. You can get some "rim tape" (is that what it's called???) to make sure these are well covered. Some bikes come with very flimsy rim tape that doesn't do a very good job, and if it shifts, it can puncture the tube. I think it's called rim tape ....hmmm... did I get the term right????
 

indianajo

Well-Known Member
I've never used or heard of rim tape. I use electrician's tape to cover the spokes if the wheel didn't come with a rubber band cover.
Leaks in other places can leak out the rim. Check your stem that the hole has not sliced it. I find on cheapo discount store bikes, I have to smooth out the hole with a round file to get any kind of life out of a tube. Wiggling the file around as you stroke is necessary to make a nice round edge, no right angle corners. Buy a nicholson file, the ones from harbor freight look just like real tools but are only toys.
Excessively long spokes can also poke holes in tubes. I use a flat file on these. A good whack by a pothole can stretch spokes, especially if you are carrying some weight. At 170 lb I don't have much trouble with 14 ga DT swiss spokes, although one cheapo bike from the charity resale shop the spokes stretched badly.
 
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J.R.

Well-Known Member
With the rim off the bike, tire and tube off (including rim tape) the rim, inspect the entire rim for burrs that could damage the tube. Use a couple cotton balls and rub the inside of the rim. Any burrs will snag the cotton fibers. Rub in all directions, making sure to contact all spoke nipples/holes and stem hole. Smooth any rough spots with fine (400 grit) emery cloth. Do not use regular sand paper.
 

harryS

Well-Known Member
Indianajo, your ebikeling kit probably had a rubber strip that went over the holes in the double wall rim. Bike shops sell a paper adhesive tape about 3/32" thick that does the same thing and fits nice inside the rim if you get the right width. I have used electricians tape too, but rim tape is better.

The bike spoker mystics think 14G is stronger than 12G because of higher tension. I dunno. I figure bike spoking is a job for high schoolers in bike shops. I'm a cranky old retirees and do spokes because I don't want to pay 50 bucks to a shop so the high school kid gets $10.
 

ebikemom

Administrator
Staff member
On rim tape, I wasn't up on it either, but this is what my bike tech uses. It is a cloth tape. I think it has an adhesive on one side, but I don't think rim tape adhesive is super strong. I've also seen him remove and replace rim tape, and it peeled off easily:
Screen Shot 2019-05-09 at 7.57.00 AM.png
He buys it in v-e-r-y large rolls, however! Once it is there, it stays put and protects the tube from wear caused by hitting those holes in the rim. I'm not sure how often it needs replacing, but since I've seen replacing happening, I guess it is subject to wear like other bike parts. Or, he just replaced it because he wanted to use a better product. I don't know.
 

Mike's E-Bikes

Well-Known Member
I'm still in hell, trying to get my lemon ebike to work. I thought I had it all ready, both wheels back on, gears and brakes working, new rack installed, etc. Then today I found the back tire flat again. I had installed a new rim liner and a new Slime tube, even though the old tube has held a partial inflate for almost a week now. There was never any sign of damage to the tire.

I was able to figure out where the leak is coming from, it's a small 1" area where the tire meets the rim. Both tire and rim appear fine. I don't want to waste more money on tubes and tires until I know what would cause this. If it's the rim I'll have to go after the ebike vendor (again) because the whole rear wheel including motor will have to be replaced.

Could it be something simple like a twisted/wrinkled tube? Or is it a problem with the (steel) bead of the tire?
If there is nothing sharp on the rim edge in that "1 inch" area, and the inside edge of the tire itself doesn't have any abrasion, then it sounds like the tube is getting pinched between the tire and rim. Double check to make sure the tube diameter and thickness is correct for that size tire. If it's occurring at the edge/lip of the rim, then rim tape won't help any. Also, are you using a compressor or hand pump ? Some compressors can fill the tire too quickly, and if you have a narrow rim, or even a nearly imperceptibly uneven rim, the tire can get pinched, and blow. Fill slowly, or only go up a few psi at a time, making sure the tire remains centered all the way around the rim. I once saw a bike shop 'mechanic' blow 3 tubes in a matter of minutes bc he had no clue what he was doing.
 

Credible Hulk

Active Member
Thanks for all of the advice!
1. I bought rim tape at the same time as I bought the new tube. The bike didn't come with rim tape. It's made of plastic, non-adhesive, supposedly for mountain bikes, and stretches to fit the rim. It fits pretty snugly but with effort it's capable of sliding (around the circumference of the wheel, not side to side). When I installed the tube I made sure to push the rim tape hole down to the root of the valve to prevent the valve from trying to push the tape through the hole.

2. There are spoke holes in the rim but there's a space between the tops of the spokes and the holes. No spokes are protruding into the rim. However, a few days ago I did find a big, sharp burr on one of the spoke holes which I filed down, but probably not enough because I couldn't reach all the way. Once I get the wheel and tire/tube off I will use the cotton ball test to check for burrs. I think a rim burr is the most likely cause of the leaks (see below). I just came home from buying emery cloth in "assorted" fine grits to polish the inside of the rim.

3. I did some detective work and pulled the original tube out that came with the bike. I had treated it with slime. I inflated it to higher pressure and could hear the air escaping. The leak was on the surface of the tube facing the rim, there was a bit of slime coming out. I had already marked the leaking area on the rear wheel last night. I held up the old tube next to the wheel with the valves lined up, sure enough the leak on the tube was on the exact same spot as the leak on the wheel. So - I'm guessing that means the leak is being caused by something on the rim. Another interesting fact is that this tire/tube was 3/4 inflated for several days with no leaks, it was only when I topped up the pressure that it started leaking again.

I also bought a thicker "puncture resistant" tube just in case.

Another question: when working on wheels/tires is it better to lay the bike on its side (derailleur up) or flip it upside down? I do have a rack that holds the back end up, but with the fender (VERY difficult to un/reinstall) there's not enough clearance to pull the wheel out.
 

indianajo

Well-Known Member
I flip my bike but be sure to protect the display from scratching. I rotate mine down parallel to the ground before flipping. Also mirrors. With the bike upside down when "done" you can turn the pedal to make sure the derailleur takeup is aligned right and the system is shifting correctly. I have to use pliers to wind up the takeup: relatives of the hulk will not have the strength problem.
Usually I have to unclip the brake cable to open any rim brakes to let the tire out. Disk brakes you should open the pads to allow the disk to slip out. Also possibly release the adjustment bolts.
 

Credible Hulk

Active Member
Hi!
Is it a double walled rim? Typically double walled is less of a problem since the spoke nipple is recessed.
Yes, as I mentioned there's a space between the holes in the rim and the spoke nipples.

I took the wheel off, then the tube and tire as well as the rim strip. I used fine emery cloth to polish the inside of the rim because there were some rough bits and burrs (I did the cotton ball test). I gave the beads/edges on the tire a gentle rub as well, it's got steel beads and was a bit rough there.

Now I've put the new tube and tire on. I took my time and made sure I didn't do anything dumb like pinching the tube or inflating it before I checked both sides to make sure the tire was seated properly. It has "witness lines" near the rims which show whether the tire is evenly seated. I've inflated it to 20 psi for now, it appears OK so far. I'm not going to reinstall the wheel until tomorrow, just to make sure it's not leaking again first. Soon I will be a world expert at removing/reinstalling the rear wheel of an ebike with all the practice I'm getting! One thing I learned is to leave the axle nuts on and just loosen them, that way nothing gets lost and all the washers stay in place so I don't have to memorize which washer goes where.