Tire pressure for 225/55R17 new tires (Hankook Ventus ST) - Subaru Forester Owners Forum
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post #1 of 26 (permalink) Old 08-05-2008, 09:04 AM Thread Starter
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Question Tire pressure for 225/55R17 new tires (Hankook Ventus ST)

Hello there,

I'm replacing the nice and beautiful Geolandars with a set of 225/55R17 Hankook Ventus ST, and was wondering what pressure I should put into them...

The max. air specified for them is 51psi. Their max. load is 2094 lbs.

What should I run, then?? The Geolandars where using 36/35 front and rear... I want performance. Good driving. Why am I getting these Ventus if not....? ;)

I would appreciate your input, guys!


Cheers,

MO
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post #2 of 26 (permalink) Old 08-05-2008, 09:15 AM
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I would run the same 36/35
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post #3 of 26 (permalink) Old 08-05-2008, 09:30 AM
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post #4 of 26 (permalink) Old 08-05-2008, 09:42 AM
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I ran 36/35 with my 225/55/17 RE92s.

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post #5 of 26 (permalink) Old 08-05-2008, 09:46 AM Thread Starter
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Thanks, guys........

Just found that Hankook recommends about 90% of tire's max. air... and that would be 46psi for these Ventus..... sounds high.... but given that their maximum is 51, which is among the highest I've seen............ I thought it'd be necessary a much higher pressure than ~35...

What do you think?
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post #6 of 26 (permalink) Old 08-05-2008, 09:49 AM
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Tire pressure should be what the car's spec is, not the tire's.
Just stick to 36/35 unless you're doing crazy hard-breaking turns that could roll your tires off. (I run about 40 upfront when AutoXing)
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post #7 of 26 (permalink) Old 08-05-2008, 10:04 AM Thread Starter
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Quote:
Originally Posted by kamil212 View Post
Tire pressure should be what the car's spec is, not the tire's.
Just stick to 36/35 unless you're doing crazy hard-breaking turns that could roll your tires off. (I run about 40 upfront when AutoXing)
Completely agreed with you, and this is what I've done with every car that I've owned...... but it is simply not the case for my Forester..... the one recommended is WAY TOO low.....

Is there anything like a "rule-of-three-calculation" given that you have max. load capacity available as well?? What should be the minimum tire pressure?


Cheers,

MO
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post #8 of 26 (permalink) Old 08-05-2008, 10:42 AM
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Quote:
Originally Posted by kamil212 View Post
Tire pressure should be what the car's spec is, not the tire's.
Just stick to 36/35 unless you're doing crazy hard-breaking turns that could roll your tires off. (I run about 40 upfront when AutoXing)
As a former owner of a Ford Exploder, I would suggest running what the sticker says on your door post unless you are racing, autocrossing..etc.
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post #9 of 26 (permalink) Old 08-05-2008, 10:46 AM
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IMO the tire pressure posted on the door is a compromise between a ride comfort & reasonable rolling resistance (gas mileage), with the scale tilted towards comfort, hence the low pressure recommendation. I don't think the factory really cares about tire life or performace on the Forester...

The tire pressure will vary between tire brands. I'd suggest starting with the pressure that felt right on your previous tires. I'm running Toyo Proxes 4, 235/50-17, 36/34 (front/rear pressure). After playing around with different pressure combinations, this is what feels right on my ride. A higher tire pressure makes my ride susceptible to bump steering on rought roads & too low pressure makes my side walls roll too much...

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Last edited by 2.5x_sleeper; 08-05-2008 at 10:55 AM. Reason: Added more poop...:)
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post #10 of 26 (permalink) Old 08-05-2008, 11:11 AM Thread Starter
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Hopefully, they will be on tonight. Will report back with experiences...


Many thanks!

MO
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post #11 of 26 (permalink) Old 08-05-2008, 11:44 AM
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Originally Posted by ArcadeTom View Post
As a former owner of a Ford Exploder, I would suggest running what the sticker says on your door post unless you are racing, autocrossing..etc.
IIRC, the Exploder's recommended pressure "pre tire fiasco" was under 30 psi's. 28 or 26 seems to ring a bell.

I run 34/33 on summer 225/55/17's for everyday driving and bump it up for more spirited driving.

-Dennis

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post #12 of 26 (permalink) Old 08-05-2008, 12:51 PM Thread Starter
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Actually, it is much worse to run the tires underinflated than it is running them overinflated... I'm looking for the right pressure.

What I don't get though is why would you be in a overinflated situation using anything below the actual max. air determined by the tire.

I did run a small "rule-of-three" calculation (don't know the name in English, don't blame me... ;) ), and using 35psi as the minimum value and 46 (51x90%) as the maximum, 55/45 as the weight distribution, and the tire max. load capacity I've gotten 40/39. I will use that as the starting point.

Please don't be too sarcastic - it is just that I can't avoid being an engineer all the time... :p


Cheers,

MO
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post #13 of 26 (permalink) Old 08-05-2008, 01:20 PM
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Quote:
Originally Posted by bluesubie View Post
IIRC, the Exploder's recommended pressure "pre tire fiasco" was under 30 psi's. 28 or 26 seems to ring a bell.

I run 34/33 on summer 225/55/17's for everyday driving and bump it up for more spirited driving.

-Dennis
Sorry for the misunderstanding, but what I meant was that on the next generation Exploders (and the resulting education that came out after the designers and NHTSA people all met and cussed and discussed all the issues) they seemed to make it clear that what is posted on the door/vehicle is what is reccomended for daily use in the majority of driving situations. It was supposed to be based on the suspension, spring rates and weight of the vehicle. The first generation Exploder was listed with incorrect and low pressure stickers. Anytime that you switch tires sizes, wheel diameter, etc you will have to find something that works, but if you are running the same size tire with the same load rating, I would think you're probably going to stay in that same pressure range.
All other things considered...you could always ask the tire store owner / manager or get it in writing from them as to what pressures you shoudl run with a certain tire. If it blows out at least you have someone to sue. LOL
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post #14 of 26 (permalink) Old 08-05-2008, 04:59 PM
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PLUS, dont forget to buy more than one tire pressure gauge! I have two, and they are about 7 psi different! :P Now my concern is...which one is right? :O
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post #15 of 26 (permalink) Old 08-05-2008, 10:58 PM
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I would use 34 on the front and 31 on the rear. 34 goes easily to 40 when you are hard cornering at summer and 31 is OK to avoid oversteering when you lift your foot of the gaz pedal to enter in a turn. 31 is also OK to have some ride confort. If you have perfect condition roads where you live, you can use more, in order to also have some fuel economy IMHO...

thre are some tires like all toyos who likes high pressures, I don't know why.
Keep in mind that with normal air (not azote) the pressure at high tire temperature ie70 degrees celcius (wich is normal after hard cornering) maybe more than 20% greater than when the tire is cold. (tested a lot of times)

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