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This is why I got a PX

December 4, 2006

I’d just gotten back from the laundromat. The painters were working in my condo, so I just dropped the laundry bag in the bedroom and got the helmet and gloves. But when I walked out of the elevator, I noticed the front tire was much higher off the ground than usual.

And why was the front wheel up so high? Because the rear tire was flat, that’s why.


This happened once with the ET4. Luckily, that time the tire wasn’t completely flat, so I pumped it up and rode it to Big People. One hundred twenty-five dollars later, I had a new rear tire. Changing the rear tire on an ET involves removing a couple of plastic panels… and the muffler. Then you’ll need an air wrench to get the nut off. Not something you’d be able to do at home, unless you have a garage as well-equipped as your local scooter repair shop. Definitely not something you could do in the middle of a road trip.

That, in fact, was what got the ball rolling toward trading the ET for the PX. I had this harebrained idea about riding to San Francisco on the PCH, and realized I’d be in deep doo-doo if I got a flat tire.

Changing the rear tire

One of the main points of the design brief for the original Vespa was both wheels should be the same size, and should be easily removable by the owner. That made a spare tire possible.

A Vespa PX 150 has a spare tire.

Having once owned an SCCA Showroom Stock race car, I have a whole bunch of tools. One of the handiest is a floor jack. Same idea as the ones the NASCAR pit crews use, I got this one (*gulp*) about 20 years ago. I’ve used it on a number of vehicles since then, mostly swapping out winter and summer tires.

Had the flat tire been the front one, there would have been no need for a jack. Since a PX’s weight is mostly in the back, it rests on its rear wheel when the center stand is deployed. Lock the headset, undo the bolts, swap the flat tire for the spare, bolt it up and you’re good to go.

No matter which wheel you need to change, before you jack the bike up, start by removing the left cowl. Take the spare tire off the mount; this will make getting at the rear tire easier. When doing this, be very careful to avoid contact with the positive battery post. You could do something like short out the electrical system. Not good! Luckily, the spare tire is mounted to the body opposite from the way it goes onto the wheel hub. No chance of separating the rim.

A 13-millimeter deep socket is what you’ll need to get the spare tire off the bracket, and what you’ll need to remove and attach the wheel lug nuts. Remember, all the lug nuts have lock washers, the better to keep them from backing off due to the PX’s incessant vibration… don’t lose them!

Since the rear tire is the flat one, changing it is a bit trickier. You need to lift the rear, but that can cause the center stand to fold up, causing the bike to fall over.

Look at the photo to see what to do. The wheel chock is simple, just three foot-long pieces of 2×4, held together with screws and wood glue. Straighten the front wheel, jam this puppy into it, and it will stay straight and planted.

Wheel chock

The front wheel secured, you can jack up the rear of the bike. This is much easier if your floor jack has a dished thing on the end of the arm; just slip a lip under the rear bumper (you know, the plastic thing below the license plate). If you’re on the road, a floor jack might be too big to carry with you; if you’re on a rally, maybe the support vehicle will have one, but if you’re on your own, you’ll have to improvise. Something like a milk crate would be your best bet.

You don’t need to lift it too much, just enough to make sure the rear wheel is off the ground.

Leave the bike in neutral, so you can spin the rear wheel. Loosen each of the five lug nuts with the 13 mm socket attached to a ratchet drive, then spin ’em off by hand. The plastic spare tire cover makes a great tray to hold nuts & washers, but if you don’t happen to have one, those little plastic cups that Jell-O pudding comes in work great. As long as there’s no pudding in them, natch.

Once the lug nuts are off, pull the wheel toward you and down. It’s off!

Before putting the spare tire on, clean it. It’s had all kinds of time to get dirty. Check the pressure, too… it would be a drag if the spare were flat. This is a good time to clean everything under the cowl. Clean vehicles are just more pleasant to work on.

Putting on the new tire is the opposite of removing it. You might need to jack up the rear just a tiny bit to get the wheel on (reassembly is almost always more difficult); make sure you don’t get the center stand off the ground. Just remember, the wheel rim is offset, so make sure the valve stem faces to the rider’s left.

Lacking a published torque specification, get the lug nuts good and tight with your ratchet. The beveled tops of the studs are just above the tops of the lug nuts when they are tightened as far you can get them with a 3/8-inch ratchet drive, so that should be okay. It’s probably best to tighten the nuts in a star pattern, as you would with your car.

I decide to mount the flat tire on the spare tire bracket for the moment, because even though it only weighs a few pounds, its absence still might cause the bike to behave differently. I guess. Anyway, there’s no other safe place to put it.

How to jack up a PX

Orin O'Neill photos

I also decide to check the pressure in the front tire. Yikes! It’s 35 lbs. The owner’s manual sez it should be 18.9 lbs. (this is from converting from bars). Let’s just say 19. The spare was 35 lbs. as well, so I dropped that to the 26.1 (okay, 26) lbs. the owner’s manual specifies for a rear tire in solo operation.

Everything looks good, so I button everything up and head to Cafe Racer. I am so proud of myself as I arrive… nothing has fallen off, and everything looks and feels good. The bike even rides better, now that the tire pressures are what they should be.

But I am going to have to fix the punctured tire.

See the video! Favicon

  1. Orin permalink*
    January 1, 2007 3:47 pm

    In a pinch, you could also accomplish this by laying the bike on its right side… just make sure you have a blanket or tarp to prevent damage to the paint…

  2. tom permalink
    April 23, 2007 8:37 pm

    great blog. i have a 1980 p200, which is pretty much the same as a px150.
    couple of suggestions–you don’t need a jack or wheel chock to change the rear tire. i raise the rear by putting a 2×4 on top of a 4×4 under the gearbox. it’s easier to get the rear rim off if you remove the mudflap and the spare first.

    you said “don’t lose the lock washers.” no way. lose ’em–and buy new ones. i reused lock washers last week when i changed the tire. 50 miles later i felt a wobble. next morning lo and behold A NUT HAD RATTLED OFF!

    i removed both rims and replaced all 10 lock washers with new ones. and replaced all the nuts with nylock nuts.

    As for fixing your punctured tire, check out:

  3. tom permalink
    April 23, 2007 8:41 pm

    oh and i think the torque spec on the lug nuts is 14-19 lb-ft. check out the haynes manual for the p series.

  4. May 5, 2007 4:40 pm

    John Rana, of Who Rides a Vespa? fame, wrote about an alternative to a jack. Trouble is, Del Monte fruit drinks may not be available in the same size cans where you live…

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