Tire pressures

[picklehead]

Hi all,

    Just curious as to what tire pressures you are running.  When I picked up the new car, I lost my tire pressure gauge in the transfer of materials from my old car.  As I result, I only recently checked the pressures.  The dealer had 32 psi in all four tires, I adjusted per the door sill plate to 35 psi front and 38 psi rear.  So far I have not noticed a handling difference with the new pressures, I am just wondering if now I will sneak a little more mpg out of the car (not that I need better mileage  http://xc70.com/iB_html/non-cgi/emoticons/smile.gif ).  I just wish that I had checked the pressures sooner, I know that some dealers will run the tires a little low to soften the ride a bit on test drives.

Very Respectfully,
Jim Miller

[wiz]

Currently I'm running 33psi all round for some reason. I normally run 33F & 31R - higher at the front because of the extra weight of the engine. I generally check pressure twice a week with a digital gauge - the Accutire MS-4020B - an excellent product! http://xc70.com/iB_html/non-cgi/emoticons/thumbs-up.gif

[purush]

A month after I picked up my car from the dealer the tire pressure read 43psi (when cold)!!!   I didn't change it.  Perhaps I should to decrease the pressure to make the car ride better.

Comments?

purush

[Hiro's XC]

I run 38 front 36 rear. Unless loaded heavily then the rear goes to 41. I do this because A. I run Nokian tires and they wear funny at lower pressures. B. I don't want the car to understeer more than it already does (front end slide out in a corner) C. I get about .7-1.3mpg better fuel economy than if I run 29-32.

Just my observations in 18K miles of driving.

Jason

[Filibuster]

I usually add 10% to the recomended.  Higher pressure works better when cornering hard and gives lower rolling friction.

[Stu in Oregon]

purush:  You certainly do not need to run that much pressure. You will be much happier I think in the mid thirty ranges.

My Michelin 4x4 Synchrones seem happiest at 33 PSI while the old Scorpians liked a few more pounds of pressure.

[kayaking]

I experienced a "wandering" feeling on the highways while driving in Sweden...I wonder if it may have been due to incorrect tire pressures from the factory. Maybe the alignment should be checked....I'll have the dealer here check it before I accept the car. I'd be curious if anyone else runs "according to the door sill plate" pressures..I always seem to go at 32psi or 33 psi all-around unless carrying heavy loads...then 36 all-around. I never understood the lighter pressure for the front wheels with the weight of the engine.

[wiz]

Today I'm at 33F & 32.5R. http://xc70.com/iB_html/non-cgi/emoticons/smile.gif In general kayaking, the front should be a couple of psi higher than the rear because of the engine. When we got our car from the dealer it was supposed to be 29psi all round but it was in fact all over the place so now I instruct the dealer not to mess with the tire pressure.

[kayaking]

Wiz...thanks ...but why then do mfgr's typical have the pressures lower for the front?

[Hiro's XC]

Lower front pressure make the front end "push" to the outside causing understeer. It is esier and safer for most people in "at the limit" driving. That is the only reason. The wander is due to the tires needing to seat in to their pattern. The suspension does not put the tire flat on the ground and until some wears off you will experience the wanders.

Jason

[wiz]

No clue, unless its a holdover from RWD instructions. Our car isn't in the garage at the moment, but as I recall Volvo's instruction on the gas cap cover is 29psi all round. That is too low for the Scorpions and will give you some of the "wandering" behavior you experienced.

[Hiro's XC]

Wiz, we posted at the same time, see 2 up!

Jason

[wiz]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (Hiro&#39;s XC @ June 21 2003,07:17)</td></tr><tr><td id="QUOTE">Lower front pressure make the front end &quot;push&quot; to the outside causing understeer. It is esier and safer for most people in &quot;at the limit&quot; driving. That is the only reason.[/QUOTE]<span id='postcolor'>
Hey there Jason&#33; http://xc70.com/iB_html/non-cgi/emoticons/biggrin.gif I understand the argument, but why would people who need a bit of extra understeer be driving the car &quot;at the limit&quot;? http://xc70.com/iB_html/non-cgi/emoticons/hehe.gif

Also I have found that several psi over the manufacturers recommendation is needed to keep the car more-or-less stable at high speed even after the car has been driven a while. The Pirelli Scorpions are not good&#33; http://xc70.com/iB_html/non-cgi/emoticons/sad.gif

[kayaking]

Thanks guys...interesting and informative info...never knew about the &quot;break-in&quot; issue of wandering tires...I may still ask the dealer to check alignment just in case...but what you indicate, Wiz, does make sense and hopefully I&#39;ll notice an improvement as I re-check pressure and break it in more...now have 930 miles on the tires...not sure if that is suffiicient &quot;wear-in&quot; period for them.

[Hiro's XC]

When I say at the limit, for the most part I mean for the times when an emergenct situation might happen and you have to make a fast emergency lane change. This is not the car to be driving 10/10ths by any means. These cars will drive VERY quickly in braking, left, right hard transitions if you push them. I took mine to a large abondoned warehouse parking lot and set some cones up to try some emergency type driving. At all speed these cars will do almost anything you ask them to do because of the AWD. The one thing I &nbsp;did notice was the fact that at higher speeds, say 60mph if you do a hard left, right, left as in avoiding some debris in the road and lift OFF the throttle these cars in wet conditions WILL SPIN. You NEED to stay ON the the gas and OFF the brake. Braking does to drastic of a weight transition and causes to much load on the outside front tire and will spin the rear end around by the second lane change. It is like a &quot;crack the whip&quot; thing. After two shifts the rear is light and sliding. If you are on the gas the front end will PULL you out of the spin. This is also know as trailing throttle oversteer. Something that the old 911 Porsche cars were famous for.

Jason

[wiz]

I understand what you are saying Jason. I have only really pushed the car on snow and ice, so I&#39;m comfortable with what happens in those situations. Have not done any testing on dry roads but take your good advice about staying on the throttle in an avoidance maneuver. http://xc70.com/iB_html/non-cgi/emoticons/thumbs-up.gif

[pico de luuks]

I&#39;m mostly running 36 front 33 rear on the scorpions.
Recently I noticed some uneven wear on my tires, could this be as a result of the higher tire pressure (recommended 30 allround) or is a allignment problem more likely?
I&#39;ve rotated the tires once and the front ones are the worst, but also the rear ones show some uneven wear.

I&#39;m intending to have the dealer a look at it under the adjustment warranty. Still 4 weeks left....

http://xc70.com/iB_html/non-cgi/emoticons/pico.gif

[Hiro's XC]

Pico,

Nope, just crappy tires. Also the suspension geometry is hard on the softer tires. All you can do is rotate them.

Jason

[budrichard]

Jason, did you perform your testing with DSTC? If not, it would be interesting to see if DSTC would avoid the spin. When sensing &#39;yaw&#39; DSTC will cut the throttle and brake the correct wheel and should reduce the tendancy to spin. Of course nothing is perfect. -Dick