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Fixing the donut hole

February 12, 2008

I was not looking forward to spending $39 for a new tube (including the half an hour of shop time to install it). Luckily, Doc said he could show me how to do it myself.

My first attempt to repair a puncture didn’t work out as I would have liked, and money is still too tight to mention, so I welcome Doc’s help. If he ever finds malpractice insurance too expensive, I’m sure he could hang a shingle as a scooter mechanic. He even makes house calls (for scooters, anyway), over the weekend visiting Kat(t) to try to correct Frankenstella’s idle woes.

So, we’re in the garage (after dark, so no pictures), Doc bringing his air compressor and 1½-ton press (that’s the pressure it exerts, not the weight of the tool).

First thing to do is remove any air that might still be in the tire. The easiest way to do this is to remove the valve core. Any bicycle shop will have a tool to this, and it’s quite cheap, so pick one up and put it in your tool pouch. In fact, this process will seem very familiar to anyone who’s had to fix a flat bicycle tire.

Squeeze the tire until you have as much air out of it as you can, then re-insert the valve core if it’s not damaged (if it is, the same bicycle shop where you got the valve core tool will also have small packages of valve cores).

Now we’re getting to the part I didn’t think of: separate the rim halves by first removing the nuts holding them together. There are five of them, facing the opposite way from the nuts that hold the wheel to the hub.

Next, get a pry bar (a big screwdriver, or anything that offers some leverage will do) and pry the rim halves far enough apart to insert some 1″-thick wood scraps (the scraps should be about 6″ long). Spread them evenly around the wheel. This will make it easier the separate the tire bead from the rim.

Put the wheel on the ground, the thinner rim half up. Step on the tire and semi-jump on it. You might need to put all your weight on one leg, and this might work better if you use your heel. Standing on a smooth rock might help, too. Don’t use a crowbar or screwdriver, you might damage the tire bead.

Unfortunately, we weren’t able to separate the tire and rim by the above method, which is why Doc brought the press. Off popped the tire.

Once you get the bead clear of the rim, just lift the rim half out. Clever, no? Oh, and if you’re going to be replacing the tire, remove the other rim half, and insert it into the new tire.

Remove the valve stem cap and push the valve stem through the hole, then remove the tube. There was no visible puncture on the tire, but upon pumping some air in the tube, we could both hear air coming from a small split along a mold line.

Few motorcycle shops will patch tubes, citing liability issues. Earlier in the day, I had dunked the tire in a sink filled with water, and saw air bubbles coming through the valve stem. On the chance the valve stem had de-vulcanized from the tube, I picked up a new tube at Aurora Suzuki, which, happily, is open on Mondays.

Very important: with the tube out, feel around the inside of the tire. It needs to be free of debris, which could puncture the new tube. Don’t use water! If you don’t get all the water out, it can boil, possibly causing tire failure. Not good. A clean, dry shop rag would be my choice for this task.

Time to install the new tube. Inflate it just enough to make the folds disappear. This will make it easier to work with, and most importantly prevent pinching or twisting. I once had a twisted bicycle tube fail catastrophically. It sounded like a gunshot. Luckily, I was only going about 10 mph when it happened.

The easiest way to insert it is to put the valve stem through the hole (cap off, of course) in the rim, then adjust it so it leans on the notch in the rim flange. Then, carefully stuff the rest of the tube into the tire, making sure it doesn’t twist or hang up on anything.

Once you have the tube installed, reassemble the rim. Don’t forget the lock washers! These nuts should be tightened to 15-19 ft/lbs., which I do by feel because my torque wrench starts at 20 lbs. They should feel as tight as the lug nuts. I tighten these nuts in a star pattern, i.e., first bolt, next closest bolt on the opposite side of the rim, next one opposite, etc. Dunno if you have to, but that’s the race car training again.

The rim reassembled, pump the tire up to 40-45 lbs., the let the air out by pushing on the needle in the valve stem. This will seat the tire’s beads on the rim. Then pump it up to the appropriate pressure (18.9 lbs. front, 26.1 lbs. rear (solo)/36.1 rear (two-up). In this case, the repaired tire is going to be the spare, so I pump it up to slightly over 40 lbs. That way, if I have to use it I can just let air out, negating the need for a pump.

Rather than toss the punctured tube in the trash, I’m going to repair it and save it for the next time a tire goes flat. Patch kits are available at bicycle stores, too. They can show you how to use it. Favicon

  1. February 12, 2008 12:03 pm

    Upon examination in the light, the old tube had many more small cracks near the one that opened up, which is enough of a potential safety issue to make discarding the old tube the best choice.

  2. February 12, 2008 8:36 pm

    The best thing about the P series Vespa ( and Stella) is the split rim. I used to carry a hammer and at the end of the day’s ride, when I was traveling, I’d put the flat on the picnic table, split the rim ( with the hammer if necessary) replace the tube and put the inflated (by hand pump) tire in the spare’s place ready for the next flat. Hand’s down it’s the best feature of the Vespa. If I could stand riding at barely 55mph all day the spare wheel would be the one thing that would get me traveling on a P200 again. The can of Fix-A-Flat in my Bonneville’s saddle bag inspires no confidence…But I cruise at 80 just fine.

  3. February 14, 2008 5:39 pm

    Very important: you need a tube with an L-shaped metal valve stem. There’s no room for the straight rubber kind. Sorry to leave that out… duh!

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