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1988 M-BENZ 300E | 1991 FORD PROBE GT TURBO | 2003 FORD EXPLORER 4x4
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684 Posts
Discussion Starter #1
29, 32, or 35 PSI?

Sticker says 29 normal all 4, 35 rear at max load.

Tire shop says 32.

I'm confused.

Personally I would like whatever pressure delivers equal pressure to the ground across the width of the tire, but no idea how to figure that without a specially designed multi-zone scale. Too much air and there will be more pressure to the ground in the middle of the tire, not enough and there will be more pressure to the ground on the outer edges.
 

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E320/E250 Bluetec Ford F350 6.7l
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36,729 Posts
Radial tires can take over-inflation pretty well with even thread wear, while lower pressure can lead to tire overheating and deterioration.
I always run my tires at the pressure recommended for heavy load and often add couple of psi
 

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1995 E320
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2,548 Posts
Open your gas tank flap, read your tire pressure.

My car says: 26F 26 R (Might be 27. Can't be bothered to go downstairs and check.)
Full load is: 26F 29R
Speed >100mph: Add 8psi.

I generally run 29F 32 R.
At 26psi my ride is plush and cosseting.
At 29 it's a little firmer, but no longer ignores all those expansion joints and broken tarmac.

I use the slightly firmer rear air pressure to give a stiffer tire and better fuel economy.
 

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1984, 201.122, OM601.921, G717.410
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504 Posts
> Deal with it and move on.
= We don't want to discuss anything on this forum. (Thus, MB world need not exist).

Before the fiasco with Firestone and Ford blowout rollovers, tire pressure was often specified on the low side for a "cushy" american ride (what I equate with a tugboat).

Your best answer is to contact the tire manufacturer and ask what prerssure produces even wear for the actual load weight on the tire. This means to get a REAL answer, you need to go to a scale and measure the front and rear weights, before contacting the tire manufacturer. They should be more than happy to give you various load pressures. If not, then threaten to go to another manufacturer.
 

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1993 300E, 2003 996 Turbo X50
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624 Posts
> Deal with it and move on.
= We don't want to discuss anything on this forum. (Thus, MB world need not exist).

Before the fiasco with Firestone and Ford blowout rollovers, tire pressure was often specified on the low side for a "cushy" american ride (what I equate with a tugboat).

Your best answer is to contact the tire manufacturer and ask what prerssure produces even wear for the actual load weight on the tire. This means to get a REAL answer, you need to go to a scale and measure the front and rear weights, before contacting the tire manufacturer. They should be more than happy to give you various load pressures. If not, then threaten to go to another manufacturer.
No,its that people tire of others asking the same questions over and over.

I have an idea, lets start a "what oil is best?" thread!
 

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Premium Member
'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,424 Posts
For UN-loaded and non-high speed driving...run 75% of the tires maximum tire pressure. That will always put you about spot-on for wear and performance.

And in defense of Jim's comment, this poster has a bad history/habit of arguing why ants crawl on the sidewalk. If you don't believe me, look up some of his threads.

Kevin
 

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E320/E250 Bluetec Ford F350 6.7l
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We could profile more members, but what would be the point?
I don't agree with 75% rule. Some tires in this size have 35, some 50 psi max pressure. I had 2 tires from the same manufacturer in the same model, but from different year showing such big difference. You should follow car manufacturer advise.
 

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american 1986 300E 3.0l
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107 Posts
always go by the car manufacturer.
your car says 29 lowest 35 max load, so that is your range. it is up to you to pick between that range for the comfort that you will like.
29 is a soft ride anything up to 35 will become a harsher ride
good luck

as per a request here is my pressure stats
30 front 34 back in the city
34 front and back if i am going to do long highway trip
and this is where a good tire manufactuer rating with higher rating comes in handy
 

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W124
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5,179 Posts
"...your car says 29 lowest 35 max load, so that is your range. it is up to you to pick between that range for the comfort that you will like..."
Make a decision! Best advice so far. FWIW, I run 32lb cold all around. The ride is more harsh but the turn in is more crisp and the car rolls more easily. I would be intested in knowing what his choice was.
 

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Timeship, see you yesterday, but you already knew that.
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4,103 Posts
The tire folks just started doing this about the time tires was invented.


They mold the pressure rating on the tire, its new but it works.
 

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99-C43, 05-G55K, 71-280SL, 94-E320 CAB
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2,282 Posts
All depends on how you drive, speed typically driven at, your suspension, power output and what feel/feedback you want in handling...

If the tires, regardless of size, meet the recommended measured rim width then you have a great deal of latitude for pressure between comfort and crisper handling.

I tend to bias with 32 front and 35 rear on all my cars which decreases oversteer...
 

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1988 M-BENZ 300E | 1991 FORD PROBE GT TURBO | 2003 FORD EXPLORER 4x4
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684 Posts
Discussion Starter #17

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W124
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If you don't feel a difference between 29 and 32, consider yourself lucky and leave it at 32. You'll get slightly better mileage.
 

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99-C43, 05-G55K, 71-280SL, 94-E320 CAB
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2,282 Posts
These are the tires I am using if it matters: Pirelli P4 Four Seasons | All Season Touring Tire | Limited tread wear warranty, Touring Tires.

I went from 32 to 29 because of the bumpy roads out here but do not feel a difference.

My struts/shocks are KYB and about 1.5 years old.
You'll only feel a great deal of the road with a low profile, short sidewall tire, which you don't have.

Adjusting air pressure will not reduce the "bumps' you feel..

Personally not a fan of KYB, but they are relatively new and should give adequate damping.

The vehicle is old, hopefully you replaced the front strut mounts when you did the KYB's...
Much rubber in the suspension and if the bushes are worn, you'll feel the "bumps"
 

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Premium Member
'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,424 Posts
We could profile more members, but what would be the point?
I don't agree with 75% rule. Some tires in this size have 35, some 50 psi max pressure. I had 2 tires from the same manufacturer in the same model, but from different year showing such big difference. You should follow car manufacturer advise.
I don't really care if you disagree. If you want the maximum life out of your car's tires and assuming normal passenger loads, 75% of maximum has been the rule of thumb in passenger cars for a very long time. If you're talking about performance and maximum cornering potential, then we would be having a very different conversation.

Kevin
 
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