Tire pressure

monahan_z · Oct 18, 2004

I have been talking to a few people recently as to what tire pressure they use in their cars. I get a range of numbers! I have a 6L Diablo with 18" wheels (Front 235/35/ZR18 and back 335/35/ZR18) P-ZERO Pirellis. I pump them up to 42PSI front and back. I do this because I have had problems with rims on earlier cars getting bent when striking potholes on the road at lower pressures. Also the car seems to hold the road better on turns at these pressures. Some people however say this is too much, that a 32PSI number is better because more tread is contacting the road.

What numbers to others out there use? Does it maks sense to use a lower number in the summer when the weather is hot and higher in the winter?

ltadmin · Oct 18, 2004

John, use the Manufacturers recc. numbers only....if you want a softer ride or go to the race track you can go up or down by a few pounds only.

32psi on 18's is nuts.

sk90077 · Oct 18, 2004

Its always good to use the manufactures numbers because Viscous Coupling.

aehaas · Oct 18, 2004

These cars are very particular. Use the pressure they tell you to use.

My Murcielago manual says to use 38 PSI but I think the door sticker says to use 42 PSI. This is what I am using.

aehaas

rampante · Oct 18, 2004

Probably a mis-labeling issue but the Gallardo owner's manual states 34/36 lbs. for normal use and the sticker on the door sill only states the tire pressure as 44 lbs. ??????????????

Jake

speed2 · Oct 18, 2004

My Service Manager says that you should use at a minimum 40 to 42 PSi with the P Zeros' that are on the Diablo. 235/35VR18 and 335/30VR18 He went on to explain that using less than the recomended PSI can cause problems with the belts in the tires. I did not understand all of what he was saying but it sounded like he knew what he was talking about and he was very convincing that I should keep the pressure close to the recomended setting.

Kenny94945 · Oct 18, 2004

If I may add my 02 about tire pressures..

We have ride, grip and wear issue. The manufacturers suggestion is in the ball park for OEM tires and rims. It can also be a starting mark for aftermarket tires.

One really needs to utilize a pyrometer to complete an accurate pressure set up.

However, for street use, a rule of thumb I have always used was the tire once hot should have increased in air pressure 10% over its cold readings.

For example if the fronts are set cold to 42, once hot they should be 46.5 lbs.
36 cold would be 40 hot. Give or take a pound.

As to wear, one would want to look at the wear pattern. In my non-Lambo case, my passenger rears would wear the center because of hard acceleration, so I lowered the pressure until I got even wear across the thread. The fronts wore the inner and outer edges so I increased pressure. Always keeping the 10% rule. An aggressive alignment could make these adjustment possible irrelevant.

Lastly, I just changed front Firestone Firehawks to Yokohoma AVIS and the old Firestone pressures needed to be changed to new pressures with the Yoko's. So one tire pressure chart will not transfer among different brands.

C5 Corvette..I use rear 25 and fronts 33 cold with hot at 28 and 37. Gives me a light steering and rear hook up and feels good to my driving style. These were both runflat tires.

wildwarrior · Oct 18, 2004

I run 44psi rear and 45psi front in my stock SV tires.

wiz357 · Oct 18, 2004

Ideally, a pyrometer is the way to go, especially when you're running around the track. As for me, I just follow the door jamb recommendations.

rampante · Oct 18, 2004

Raymond-
that's what has me puzzled. the manual says one thing and the door jamb says another.
Jake

Mark M · Oct 18, 2004

This is from my 99 manual:

Rayman · Oct 19, 2004

wildwarrior said:
I run 44psi rear and 45psi front in my stock SV tires.

WOW, Glen is Pumped up!

youngwill100 · Oct 19, 2004

European Gallardos - different pressures?

rampante said:
Probably a mis-labeling issue but the Gallardo owner's manual states 34/36 lbs. for normal use and the sticker on the door sill only states the tire pressure as 44 lbs. ??????????????

Jake

Interesting... My Gallardo manual here in the UK says 2.3 bar front (33psi) and 2.2 bar rear (32psi). And no door jamb stickers anywhere. I think the tyres are the same - Pirelli P Zero Rosso - so why the difference in pressure? I wouldn't like to run mine any harder, the ride is quite harsh on bumpy roads with the current pressures. And they are fine on the track - even driven fairly hard the wear hasn't reached the edge of the tread pattern.
William

rampante · Oct 19, 2004

youngwill100 said:
Interesting... My Gallardo manual here in the UK says 2.3 bar front (33psi) and 2.2 bar rear (32psi). And no door jamb stickers anywhere. I think the tyres are the same - Pirelli P Zero Rosso - so why the difference in pressure? I wouldn't like to run mine any harder, the ride is quite harsh on bumpy roads with the current pressures. And they are fine on the track - even driven fairly hard the wear hasn't reached the edge of the tread pattern.
William

Sorry William, My error; the USA manual states 35 lbs (front) and 32 lbs (rear). However, the door jamb sticker ( a legal requirement in the USA ) reads only the 44 lbs/sq. inch amount (for high speed driving). The factory probably made a deletion error on the sticker; and if the federal authorities here catch it they will most likely require Lamborghini to replace the incorrect versions of the sticker in the US.
Regards,
Jake

monahan_z · Oct 19, 2004

I am still a little confused on this question. Most people are recomending a higher number. I (finally) looked up the car manual it says:-

Front 2.6 bar, Rear 2.5 bar.

Doing the math we have:-

Front 2.6 X 14.503 = 37.7 psi (so 38 psi)
Rear 2.2 X 14.503 = 31.9 psi (so 32 psi)

Do I understand it most peole like to run their tiers a little harder?

ltadmin · Oct 19, 2004

monahan_z said:
I am still a little confused on this question. Most people are recomending a higher number. I (finally) looked up the car manual it says:-

Front 2.6 bar, Rear 2.5 bar.

Doing the math we have:-

Front 2.6 X 14.503 = 37.7 psi (so 38 psi)
Rear 2.2 X 14.503 = 31.9 psi (so 32 psi)

Do I understand it most peole like to run their tiers a little harder?

John, that's what I orinally stated, there is a few (a few being 2-4psi) leaway in the optimal published factory numbers to improve ride quality under the many varying conditions any individual owner/car may find itself being subjected to. Full out Track Days will vary slightly from days only going to the grocery store type of use. Professionals start at a given pressure and use tire pyrometers to determine the exact correct heat range & pressure at which the tire is working best for conditions.

SI LAMBO · Aug 23, 2005

I looked in the manual for the tire pressure on my 1991 Diablo Pzero tires. Guess what I found?

Per Manual
Front 245/40 ZR 17 - 2.8 Bar (converts to 40.611)
Front 335/35 ZR 17 - 2.7 Bar (converts to 39.16)

The label on the door says:

Front 37 psi
Rear 45 psi

I think those Italians didn't proof read the early manuals...can't trust them.

Anyone else have a manul like this?

I assume the door is correct. What are others using?

morphdj · Aug 23, 2005

SI LAMBO said:
I looked in the manual for the tire pressure on my 1991 Diablo Pzero tires. Guess what I found?

Per Manual
Front 245/40 ZR 17 - 2.8 Bar (converts to 40.611)
Front 335/35 ZR 17 - 2.7 Bar (converts to 39.16)

The label on the door says:

Front 37 psi
Rear 45 psi

I think those Italians didn't proof read the early manuals...can't trust them.

Anyone else have a manul like this?

I assume the door is correct. What are others using?

Not sure, but think I will stick to 41psi front and 40 rear, tried it the other day (was nice, hot, dry and sunny) and was pushing the car quite hard on some country lanes and it felt on rails, so works for me

Tire pressure

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