Modern Vespa

I'm wondering what tire pressures people generally run on vintage Vespas. I've got a 1978 Super 150 (Mk II Eurospec) that has 8" tires (with tubes, obviously). The original manual says to run 15.5 PSI front, 18.5 PSI rear with one rider, or 32.7 - 35.5 PSI with two.

Those single rider figures seem way too low to me. We've recently had some quite cold temps here (below freezing at night) so naturally tire pressures have dropped; on a short test drive they felt quite squirmy so I knew a refill was a must. After pumping them up, I thought even 20 PSI front and 25 or so rear seemed somehwhat low compared to what I had run comfortably on in the summer (I've got Michelin S83s 3.5x8).

I know tire compounds have changes drastically since the 70s when the manual was produced, might innertubes have also changes and different pressures are suitable now? What do others use -- I'm particularly interested in responses by those with 8" tires as well.

On another note, it's been more than usually difficult to fill up the rear tire: the valve stem end is so close to the hub (it bends over the split rim half) that I can't even fit a pump onto it without removing the wheel entirely off the hub first. I might switch front and rear over the winter and see if it makes access easier.

Cheers.
phaetn

Funny thing you should mention!

I always was a bit perplexed with the rear tire solo pressure being so much lower than with pillion. For totally non-scientific reasons, I've used a higher solo pressure of about 25% of the difference between the two - about 24 psi.

Can't say if it is good, bad or no difference, but it made me feel good!

Al

There is a great article in this month's scootering magazine about tire ratings, and a fair amount of time is spent on tire pressure. Maintaining the proper tire pressure for the load on the tire is important, because an improperly inflated tire at high speeds creates more heat. Too much heat will begin to affect the integrity of the tire and possibly even the tube.

It's a pretty thorough article, and well worth the cost of the magazine. I found a copy at Barnes and Noble last evening.

Len-

Unfortunatlely, Scootering is not available here.

However, over the years, I have read numerous articles and tech bulletins about tires and inflation. Interestingly enough, just about any under inflation is a more serious threat to a tire than slight over inflation.

Tires are manufactured to meet max load, road speed (RPM) and inflation pressure. These are based on the structural limits of the tire. HOWEVER, the inflation pressure for a given tire on a given vehicle is determined by the vehicle manufacturer, based on a variety of factors, mostly pertaining to ride feel and handling characteristics desired.

Inflating below the vehicle manufacturer's recommended pressure will cause the tire to run "fattened and flattened" putting undue stress on the tire body, causing heat build up, reducing tire/tread life and fuel economy and causes poor handling if the pressure is low enough.

Inflating above the vehicle manufacturer's recommended tire pressure, but below the tire manufacturer's max pressure tends to effect the quality of the ride (harder and harder) and the tire's response to bumps and holes in the road. It does not, however, threaten the tire integrity. You will note in the links below that it is common for racers to "over inflate" their tires for improved handling.

Check these two sites
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=1
http://www.betiresmart.ca/inflation/proper.asp?loc1=inflation&loc2=proper

In the main, inflating to the vehicle manufacturer's specified pressure is a wise bet. A little over inflation can be done to your taste.

Al

Yup...on my race bicylce I over inflated up to a (nice value) 123 PSI in metric 8.5 Bar

As I find my Heidenau tyres a bit bumpy, I under inflate these to 29 PSÏ (2 Bar) front / 32 PSI (2.2 Bar) back.

I generally run 27 front, 32 rear for solo. And double, as the girlfriend weighs nothing.

Thanks for all the replies, gents.

Tonysmallframe, I'm at about that range myself (though in a largeframe with a 150cc engine, so it certainly weighs more). I won't make any comment about my wife so I can actually keep my Vespa.

I'll definitely see if I can get my hands on a copy of the latest Scootering magazine. Given that we use innertubes, and that we actually lean on the tires for cornering, unlike cars, I wonder what other issues might arise apart from those already listed in those two helpful links, Aviator. I used to race cars and know about the importance of pressure, and the varying grip and performance it offers, but I'm relatively new to two wheeling.

Cheers,
phaetn

I run about 20psi front, and 30 psi rear.... on all my bikes.

For those of you who don't know them, Tony and his girlfriend TOGETHER still weigh nothing.

And Happy Birthday, Eric!

Continental recommends against under-inflating tires in order to get a softer ride. Here's what they have to say:

"We do however advise that you always ride at the highest pressure level given in the manual. Some amount of comfort will be lost, but that loss will be outweighed by improved safety. In addition the rolling resistance will be lower which will help to save fuel."

22psi on the front and 37psi on the rear more air in the back because of the weight of the engine and well if the roads are good have more in the front too

if the roads suck have less this gives you much more bounce for ruff ride

22psi on the front and 37psi on the rear more air in the back because of the weight of the engine and well if the roads are good have more in the front too

if the roads suck have less this gives you much more bounce for ruff ride

Does it make a difference if they are 8" or 10"?