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Old 11-29-2005, 04:09 PM   #1
joek007
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05-subaru STi

Default Recommendation for Falken 451 tire pressure

What is the recommended tire pressire for Falken 451 245/40/ 17 on stock STI rims for normal driving....
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Old 11-29-2005, 04:26 PM   #2
ripvw
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I've been experimenting with tire pressures on my 225/45x17 FK451's for some time. I'm convinced that max grip for this tire on the street lies betweeen 36 and 38psi cold pressure - 40psi hot works well too and is easy to check for at the gas station.

Higher than that and steering response improves at the cost of less grip both wet and dry
lower than that and they lose some of that "connected feeling" and don't appear to grip any better dry - actually grip less well in the wet

auto-x: whole different ballgame...
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Old 11-29-2005, 04:28 PM   #3
joek007
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Thanks. Do you run 36-38 psi on front and rear? since the RE 070 stock tires recommendation is 36 front 30 rear.
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Old 11-29-2005, 05:28 PM   #4
ripvw
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Quote:
Originally Posted by joek007
...Do you run 36-38 psi on front and rear? since the RE 070 stock tires recommendation is 36 front 30 rear.
running the stock psi will reduce some of the STI's inherent understeer. You'll get more grip up front @ 36psi than in the rear @ 30psi - and this is probably a good thing for that car based on tests I've read.

However, I'm not a big fan of using tire pressure to affect understeer/oversteer characteristics since it affects grip. If you are running the stock suspension setup it is probaby good to use those settings, but if you go with a more agressive alignment, larger swaybars, and an ALK to increase front grip via suspension mods, you can then run 36/36 or 38/38 and get max grip from your tires. Here's what I did:

stock '02 wagon on 205/55x16 RE92's: ran 35F/30R to reduce built-in understeer - factory recommended pressures are 32/29
modified '02 wagon on 225/45x17 FK451's: running 40 hot F/R because I added an ALK for increased front grip, larger 20mm rear swaybar to match OEM 20mm front bar for added front grip, camber/caster plates up front and aftermarket camber bolts in rear allow -2F/-1.5R negative camber, 2 additional degrees of postive caster (which affects dynamic camber) for lots more grip front and rear. I took care of the grip and camber issues with my suspension mods so I don't need to compromise on my tire pressures and can go for max grip

then again, I don't have an STI with that wonderful front LSD so you may benefit from slightly different pressures - but for the street I don't think it will matter than much

and contrary to popular belief, 38psi or 40psi up front is not necessary to compensate for the extra front end weight of the Impreza design. 36psi cold will give you maximum load capacity for any non-XL rated Euro-metric tire design - like the FK451. XL-rated tire sizes need to increase the cold pressure by 6psi to maintain maximum load capacity. This is not an issue with the FK451 in either your size or mine, nor for any typical Impreza tire sizes for the FK451. Other tires do have this issue, however, and it is very commonly overlooked on this board...
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Old 11-30-2005, 12:14 PM   #5
NeoteriX
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I usually ran anywhere from 38/35 to like 36/33
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