IIRC the fully loaded number is even higher stillOriginally Posted by Big Gordy
Is that not for it fully loaded with 4 passengers tho
I'll need to go out and check now. Also, the figures are in bar so you need to convert to psi.
IIRC the fully loaded number is even higher stillIs that not for it fully loaded with 4 passengers tho
I'll need to go out and check now
OK I'm quoting straight out of the Haynes manual here
175/65 R15 84H, 195/55 R16 87H, 205/45 R17 84V
Normal load ...... Front 2.1bar (31psi) Rear 2.1bar (31psi)
Full load........... Front 2.4bar (35psi) Rear 2.4bar (35psi)
205/40 R18 82W, 175/60 R16 82Q,T,HM+S, 175/65 R15 84Q,T,HM+S, 195/55 R16 87Q,T,HM+S, 205/45 R17 84Q,T,HM+S
Normal load ...... Front 2.3bar (33psi) Rear 2.3bar (33psi)
Full load........... Front 2.6bar (38psi) Rear 2.6bar (38psi)
T115/70 R15 90M......4.2bar (61psi)
Lesson over for today kids
"I have not failed. I've just found 10,000 ways that won't work." - Thomas Edison
Mutley - May 2003 Chili Red 'One'
Just to back-up my previous post, I've just checked the manufacturer's sticker on my car that gives the tyre pressures (inside the drivers door or, in my case, the suicide door) and for the 205/45 R17 84V tyre with the car normally loaded it states 2.6 bar all round (37.7psi) and with the car fully loaded it states 2.8 bar front (40.6psi) and 3.0 bar rear (43.4psi).
Surely, the tyres should be inflated as per the manufacturer's guidelines, which I assume must be optimal for traction and wear?
The pump at Tesco is set up for 28psi as standard.
43.4PSI is ridiculous imo. I'd never have any tyre pressures set that high on a road car.
As a very rough rule of thumb, and at that, one that doesn't really apply to run-flats, with their stiff sidewalls, the mass of the car in pounds, divided by the average tyre pressure, in PSI, is the area of the contact patch (in sq.in). So dividing this by 4, then again by the width of your tyre should yield the length of contact patch on the ground.
So it's easy to see, the higher the pressure, the less rubber is on the ground, although like i said, this doesn't really apply very well to runflats, and only makes any sense at reasonable working pressures where the tyre stiffness doesn't have much noticeable effect.
I'd be interested to see what the reason for pressures that high is.
That will be for the cars with the space saver spare wheel option. Space savers seem to get super hard pressure to make up for the tiny profile.
Yup.
Mass is constant, area is small, therefore pressure has to go up to compensate.
Me too - I was quite surprised to see such high recommended pressures. I have been assuming that it is a run-flat thing since I've never had them before but I'm no expert.
Random fact:
Apparently run flat tyres, depending on size and make, carry a 15-27% weight penalty over non run-flat tyres.
That's a lot of unsprung weight!
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