Check ur tires
The picture on the left was sent to me by friend Jack in Spokane. It was the rear tire on his wife’s Vespa GT.
He’d filled it with air to the recommended pressure, but as she attempted to enter a freeway the tire deflated. It had worn down to the fabric in the ride from home to the freeway ramp.
As you might imagine, the consequences would’ve been disastrous had this happened at freeway speed.
Jack said he was waiting for the wear indicators to become visible. Unfortunately, Jack found out the hard way that scooter tires don’t have wear indicators.
Tires for cars and light trucks sold in the U.S. and Canada are required by law to have wear indicators in their tread. The indicator takes the form of a raised area in the tread groove that’s about 2/32″ shallower than the rest of the tread.
When the tread wears down sufficiently, the indicators form a strip across the tire tread, making it easy to spot a tire about to wear out.
There is, however, no such requirement for scooter tires.
The tire in question was a Pirelli GTS25 (right), which is fitted as original equipment on Vespa’s GTS and GTV models. The slightly smaller GTS23 is used on the front wheel, but has the same tread pattern.
You’ll notice a squiggly central groove that runs the circumference of the tire. That had worn completely away in this case.
And that’s not to say anything was wrong. Scooter and motorcycle tires have a rounded tread profile because, unlike a car or truck, the bike leans into corners. The tread must extend up the sidewall so as to continue to direct water away from the tire’s contact patch.
But unless you’re doing a lot of canyon road carving, the center of the tread is going to wear out long before the upper edges of the sidewalls. You mostly ride straight and upright. Right?
Therefore, your tire’s central tread groove (or groove crossing the center of the tread) must be your guide as to when to replace the tire.
Scooters’ and motorcycles’ rear tires wear much more quickly than the fronts. They’re carrying most of the weight, and providing traction to move the bike. So it stands to reason they’ll wear out faster. Your old-skool Vespa or Stella has the same size wheels and tires on both ends, so you can rotate them and distribute the wear somewhat more equally. No such luck on modern Vespas, which have slightly larger tires on the rear wheel and seem to go through rear tires about every 4000 miles.
I see lots of scooters of all kinds with squishy rear tires. It’s not so hard to understand—modern scooters are (usually) so reliable it’s easy to get out of the habit of performing a pre-flight check. I have been guilty of this myself.
Keeping your tires at the recommended pressure is easy: a good tire-pressure gauge and a bicycle pump can be had at your local big-box store for less than 20 bucks, total. The old “penny test” applies here, too. Put a penny upside down into the tread groove. If the top of Lincoln’s head is visible, it’s time to replace the tire. Ditto if the center of the tread is bald.
So, the central grooves in some scooter tires do serve a purpose. They’re your wear indicators.