Tire Pressure - Subaru Forester Owners Forum
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post #1 of 23 (permalink) Old 02-01-2008, 02:10 PM Thread Starter
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Tire Pressure

I am running Michelin HydroEdges on mine, and I wasn't feeling very comfortable with the stock tire pressures. I know folks on here run theirs at all different psi for front and rear.

The tires are stock size [215x60R16] and I was hoping to get a little bit of input about what might be a better pressure to run and how to even come to a conclusion like that.


Kurt

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post #2 of 23 (permalink) Old 02-01-2008, 02:26 PM
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I've got some new tires on order as well... Stiffer sidewall, stock size... Thread subscribed!


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post #3 of 23 (permalink) Old 02-01-2008, 04:32 PM
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I run..

35R and 32F. It makes the steering a bit slower and heavier.
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post #4 of 23 (permalink) Old 02-01-2008, 04:34 PM
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Max tire pressure -10% is a good guide.

'05 FXT 4EAT (SG9CYBT) PSM Stage 1
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post #5 of 23 (permalink) Old 02-01-2008, 05:13 PM
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35 front 34 rear on the stock size for me.

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post #6 of 23 (permalink) Old 02-01-2008, 07:52 PM
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I'm still in test phase for best pressure for my conditions, but this week I'm running 36 F/R.

.

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post #7 of 23 (permalink) Old 02-02-2008, 08:10 PM
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Quote:
Originally Posted by jrm View Post
35R and 32F. It makes the steering a bit slower and heavier.
Quote:
Originally Posted by Peaty View Post
35 front 34 rear on the stock size for me.
What is the rationale for running different tire pressures front and back? Also, jrm has higher pressure in the back, while Peaty has higher pressure up front. Do we have competing theories here, or just different preferences?

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post #8 of 23 (permalink) Old 02-02-2008, 08:27 PM
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If you go by the door sticker, it says to have more air in the rear tires for a heavier load, which makes sense. In my opinion, putting less air in the front makes the tires grip better & thus gives a firm feel on turns. On the other side, there are those that think there should be more air in the front tires, since the weight of the engine is over those tires...

After reading all the pros & cons on air pressure, I've decided to play around with the pressure on MY03. I was running 40/40 (front/rear), per the recommendation of my tire guy, but that may have been more for longer tire wear & better gas milage (harder tires equals lower rolling resistance, equals better gas milage) than performance. Today, I dropped the pressure to 36/38 to see if there was a difference, The ride is smoother the turning is firm. I'll try this for awhile...

Update...
The sweet spot is 36F/34R for our Toyo proxes 4 tires.

Bobby...

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Last edited by 2.5x_sleeper; 04-24-2012 at 05:15 PM.
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post #9 of 23 (permalink) Old 02-03-2008, 05:51 AM Thread Starter
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...dropped the pressure to 36/38 to see if there was a difference, The ride is smoother the turning is firm. I'll try this for awhile...

Bobby...
Question about running a higher pressure now: Will too much pressure cause the tires to wear too much in the middle? Or is 35 or 40 pounds not enough to make the inside bulge out like that?

On my pickup, the tag called for 85 in the rear, but if you ran 85 without a load, the inside three inches of the tire wore, and the rest didn't hit the pavement. Will running 36/38 do that to me?

Kurt

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post #10 of 23 (permalink) Old 02-03-2008, 06:05 AM
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The door stickers on all the scoobies I've owned have slightly higher pressure in the front for normal driving and increased rear when carrying a load. I've always assumed that was due to the motor being up front. Car manufactures pick a pressure that is a balance between good MPG's and good handling, ride comfort and wear. Playing with pressure lets you tune the ride to your liking as long as you don't exceed the tire manufactures MAX pressure on the sidewall. With pressure you can induce over or understeer. I think in general lower pressure gives more grip and higher less. It's really hard to say what is best for a particular vehicle because there are a lot of factors. The type of tire / brand alone makes it difficult to predict what you should use. I don't run the same pressure on my winter tires VS my summer only rubber. It all comes down to what you are looking for. For daily driving, I like to raise the pressure a few PSI-G over the door sticker to get a little better MPG's but that is at the expense of ride comfort, but I can live with that. That is usually my starting point. What amazes me is how many people think the pressure you should use is the max pressure on the side of the tire. Then they wonder why the ride is so harsh and the tire is wearing in the center.


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post #11 of 23 (permalink) Old 02-03-2008, 06:33 AM
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I usually run 36/35, sometimes I go higher in the rear if I am carrying heavy loads. Before a road trip I usually bump it up 1 or 2 psi higher if I'm going to doing all interstate driving. This is on Michelin Pilots which felt extremely mushy at 29/28 that the manual and door jam recommended.

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post #12 of 23 (permalink) Old 02-03-2008, 09:26 AM
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Quote:
Originally Posted by spaceballs View Post
Question about running a higher pressure now: Will too much pressure cause the tires to wear too much in the middle? Or is 35 or 40 pounds not enough to make the inside bulge out like that?

On my pickup, the tag called for 85 in the rear, but if you ran 85 without a load, the inside three inches of the tire wore, and the rest didn't hit the pavement. Will running 36/38 do that to me?
The pressure on the door sticker, as Peaty wrote & I agree, is what the factory figured was a good compromise between ride comfort & reasonable wear. I don't think performace & handling was considered, especially for the Forester.

If the tires are wearing in the centers, the pressure is way too high & of course if the side are wearing but not the center, the pressure is too low, or you're taking the corners way too fast! You need to select a pressure that works for the tire (brand) & your driving style.

On MY03 the door sticker says 29/28 (front/rear) for normal use & 29/36 for additional load. I want good performance & reasonable, even thread wear above a soft ride. As with guroove, the OEM pressure gave me a soft/mushy ride, so I've always run higher pressure. This being said, I'm going to set my pressure today to 36/34 (front/rear) & see how it feels.

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

'07 FSXT - COBB Surgeline dyno stock Protune - Stage 1+
'03 X +AVO turbo kit = XT (son's)
'95 Neon Sport

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post #13 of 23 (permalink) Old 02-03-2008, 12:26 PM
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Im new to AWD

And am really learning how to use what skills i developed driving FWD and RWD cars and applying them to a AWD car. one thing that has carried over from my past experiences is running lower psi up front.

I do this to use the front end weight bias to my advantage making the steering a tad slower and thus giving me more reaction time to make small steering wheel and brake adjustments. i can add more steer in or if the cars understeering then punch the brake to get the rear end to swing outward to bring the front end in. It also makes the car feel better (more stable) at speed

My thinking is that if you run higher psi up front and lower psi in back then then your promoting understeer and quickening the steering giving yourself less reaction time to make those small adjustments i talk about above.

So far ive found that my psi strategy and the addition of a a STI rear sway bar, kartboy end links and 225/55/16 Falken ziek 912s this car really handles nice. I know ive got a lot more to learn..but sure am having fun at it..
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post #14 of 23 (permalink) Old 07-04-2014, 03:33 AM
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Hi all,

I am trying to get better fuel economy out of my 98 forester, right now I'm running 32 front/36 rear. I was a little leary about changing pressures in this even though in my Pap's truck and my Civic I had always ran higher pressures. I don't want to break the AWD system. Using my four wheel drive logic, the front and rear need the same exact ratio for final drive, this includes tire diameter. On the truck it was easy because it called for 36 all the way around, so we ran around 40, but the Soobie is 29 front/26 rear, so I wasn't sure how to proportion the pressures to get the same ratios. Any insight?
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post #15 of 23 (permalink) Old 07-04-2014, 12:03 PM
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Quote:
Originally Posted by 98_forester_s View Post
I am trying to get better fuel economy out of my 98 forester, right now I'm running 32 front/36 rear. I was a little leary about changing pressures in this even though in my Pap's truck and my Civic I had always ran higher pressures. I don't want to break the AWD system. Using my four wheel drive logic, the front and rear need the same exact ratio for final drive, this includes tire diameter. On the truck it was easy because it called for 36 all the way around, so we ran around 40, but the Soobie is 29 front/26 rear, so I wasn't sure how to proportion the pressures to get the same ratios. Any insight?
Higher tire pressure, up to the limits molded into the sidewalls of the tire, will give you slightly better mileage. The ride will be more harsh and you may have slightly less braking ability, particularly on wet pavement. But experiment and you may find the harder ride acceptable. Other users have discussed the logic for different tire pressures front and rear.

As for the AWD, I wouldn't worry about that one way or another - it's pretty durable. Subaru, which is ultra-conservative in this area - permits slight differences (1/4" as I recall) in tire circumference - check your owner's manual. Changing tire pressures is not going to take you outside of this limit. In recent years, Subaru has even relaxed this a bit.

To quote Rachael Ray 'Don't make yourself crazy'.


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