seiyafan Posted December 31, 2010 Share Posted December 31, 2010 Just want to see how many people run their psi higher than the stock setting and by how many more? And to find the best psi for mileage. Link to comment Share on other sites More sharing options...
GTTuner Posted December 31, 2010 Share Posted December 31, 2010 35 all around Link to comment Share on other sites More sharing options...
Mega Users seabass07 Posted December 31, 2010 Mega Users Share Posted December 31, 2010 I run my OBXT at 38. I get a bit more noise, but I got a noticeable increase in gas mileage and control in the underdamped outback. Link to comment Share on other sites More sharing options...
proflatlander15 Posted December 31, 2010 Share Posted December 31, 2010 I run between 36 and 38. Link to comment Share on other sites More sharing options...
rtbrjason Posted December 31, 2010 Share Posted December 31, 2010 40 front, 38 rear with 215/50/17 Conti DWS. Link to comment Share on other sites More sharing options...
apexi Posted December 31, 2010 Share Posted December 31, 2010 35 all around Link to comment Share on other sites More sharing options...
seiyafan Posted January 1, 2011 Author Share Posted January 1, 2011 I wonder why the recommended psi is different for front and rear tires. Link to comment Share on other sites More sharing options...
underground000 Posted January 1, 2011 Share Posted January 1, 2011 I wonder why the recommended psi is different for front and rear tires. Weight of the engine presses down on the tires, so the front tires become a smaller circumference then the rear. The added psi will increase the circumference to match the rear. So there would not be much speed differentiation for the center diff 5eat downshift rev match:) Powder coated wheels: completed:) Link to comment Share on other sites More sharing options...
Deadleave Posted January 1, 2011 Share Posted January 1, 2011 Was 34F 32R Now 38F 36R Saw 2 MPG jump. Link to comment Share on other sites More sharing options...
Saul_Good Posted January 1, 2011 Share Posted January 1, 2011 245/40/18 Advan Neova AD08 on 18x8 wheels (SSR Type C). Hot Pressures. 45F, 43R I've had good results on the track with these pressures. Whever I lowered the pressures my laptimes dropped. Link to comment Share on other sites More sharing options...
Dutch Eagle Posted January 1, 2011 Share Posted January 1, 2011 42 front / 39 rear. GoodYear Eagle F1 assymetric ZR 225/40/18 Link to comment Share on other sites More sharing options...
seiyafan Posted January 1, 2011 Author Share Posted January 1, 2011 won't over inflation make the center of the tire wear out faster? Link to comment Share on other sites More sharing options...
Saul_Good Posted January 1, 2011 Share Posted January 1, 2011 won't over inflation make the center of the tire wear out faster? I use a pyrometer and measure the outter, middle, inner part of the tires to be sure i'm getting even temps. During my last trackday, with those pressures, I was getting close to even temps (the outer shoulder was higher than the center and inner shoulder). My point: tire temps (outter/center/inner) should be a good indicator of where you have too much or too little tire pressure. Link to comment Share on other sites More sharing options...
king_j Posted January 1, 2011 Share Posted January 1, 2011 what psi are ppl using for winter tires? different then summer? Link to comment Share on other sites More sharing options...
Dutch Eagle Posted January 2, 2011 Share Posted January 2, 2011 won't over inflation make the center of the tire wear out faster? No, sportyres in the ZR range have no problem with above average pressures. (Up to a certain level of course) Always driven on 43,5psi front and rear on the Impreza type-RA, and they weared out even. I was advised by tire specialist, when I got my car outlined once. He told me to put 43.5 in it, instead of the 38, and that I didn't have to worry about uneven wear out. Car felt much more sporty, and wear out was complete even. Link to comment Share on other sites More sharing options...
peteyjr Posted January 2, 2011 Share Posted January 2, 2011 40/38 for street on my General UHP 225/18's. For autocross and track I use 44/42 on R compounds. Link to comment Share on other sites More sharing options...
SBT Posted January 2, 2011 Share Posted January 2, 2011 For track days and canyon carving, 38F/36R For all other times, 36F/34R - with 225/40x18 MPS ASes - best mileage state. For winter tires 35F/33R - with 215/45x17 Dunlop Winter Sports Never run same settings front and rear - always keep the stock bias so it doesn't bork the AWD system - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
SBT Posted January 2, 2011 Share Posted January 2, 2011 I wonder why the recommended psi is different for front and rear tires. That is to keep the center differential happy. Subaru is pretty specific about it and has been for as long as they've been running AWD which dates back to the late 80s early 90s. - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
Dutch Eagle Posted January 3, 2011 Share Posted January 3, 2011 2psi difference between front and rear is not because of the (viscous-) center-diff. If you check any FWD car manual, you'll find they allmost allways recommend +1 or 2 psi tire-pressure on the front also. This is due to the weightdifference front/rear, to achieve the same tire-footprint. This will give the best possible grip/stability under most circumstances. Having the rear on higher pressure than front, brings a lot of car's to a point they get too tailhappy on the limit, which most people cannot handle. If you like having the car more tailhappy however, it is recommended to have equal tirepressure front and rear, or even higher on the rear. I always drove my Impreza like that, even when I got the DCCD-center diff. A viscous diff has never had any damage from such small differences in tirepressure, or radius if you want. +1 or 2 psi does not give that much radius difference. To demolish your centerdiff you have to use tires with rather different sizes front and rear. My friend is a gearbox and engine revisor, specialized in Subaru, and told me not to worry about such small differences. The centerdiff works all day long doing nothing else than equalize big differences in wheeltorque, much bigger than the achieved difference in radius by 1 or 2 psi. According to him 2 psi is peanuts for the centerdiff. (He also is the guy who rebuilt my Impreza GTT into a Type-RA.) www.nmb-motoren.nl Completely off-topic of course, and if to be posted elswhere no problem: The latest project by the way, is a 2001 WRX who started with 218BHP. NMB-motoren took a 2.5l (semi closed deck-)engine like the one most of you have, sleeved it with steel cilindertubes, forged internals etc. and a lot more. Last dynorun was 617BHP. I done a testdrive with my friend, the car had 'only' 475BHP then, and I fellt a bit sick.... And now the owner wants more So NMB is now building up a 2.2 fully closed deck, that will be enlarged to 2.35 bar. When this project is ready, this engine can coop with turbopressures that can produce 800+BHP. 617 dyno: [ame=http://://www.youtube.com/watch?v=zuCueLNxUcA&feature=player_embedded]://www.youtube.com/watch?v=zuCueLNxUcA&feature=player_embedded[/ame] [ame=http://www.youtube.com/watch?v=XNHm1B3gNi0&feature=player_embedded]YouTube - 617HP Wrx Dyno gt35 on Bio-Ethanol ( E-85). Hombre @ Verhoeven Tuning[/ame] 3.5 seconds 0-62, and this was ealier with the Rigoli gearbox, and aprox. 550BHP. [ame=http://www.youtube.com/watch?v=5G7kJMPoLNs]YouTube - wrx accelleration with Tony Rigoli's sequential gearbox 0/100 3.5 sec[/ame] Link to comment Share on other sites More sharing options...
scoobydoobie Posted January 3, 2011 Share Posted January 3, 2011 This poll is kind of silly since tire pressure depends on different factors, including tire make and tire size. But that being said 40/38 on 225/45/17 Continental DWSs. Link to comment Share on other sites More sharing options...
SBT Posted January 4, 2011 Share Posted January 4, 2011 2psi difference between front and rear is not because of the (viscous-) center-diff. Sorry - that's specifically why Subaru prescribes it. - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
Mega Users seabass07 Posted January 4, 2011 Mega Users Share Posted January 4, 2011 It is for the same reason that any front engine car calls for higher psi up front...more weight up front. So yes fwd cars will recommend it as well. The difference is that Subaru requires it so the tire circumference is the same front to back to keep the center diff happy. BTW at least on the auto, the center diff is not viscous...it's uses a multiplate clutch. Link to comment Share on other sites More sharing options...
Dutch Eagle Posted January 4, 2011 Share Posted January 4, 2011 Oops, forgotten one thing.. In the US most Legacy's have an automatic gearbox, and you are right, they use a clutchtype diff.(MTP or 'Multi Plate Transfer') On manual transmission car's Subaru placed a viscous type centerdiff, (Plated, submerged in siliconfluid) 95% of all Subaru's here in the EU is 5 or 6MT. I have a 12 year Impreza GTT background, but not to old to learn. I can imagine that the dry clutchtype frictionplates don't like small differences in tirediameter all of the time. On our viscous type diff's this is no problem (Within margins) Nice link about the matter: http://www.autoworld.com/news/Subaru/Subaru_All-Wheel.htm Link to comment Share on other sites More sharing options...
SBT Posted January 4, 2011 Share Posted January 4, 2011 Worth noting: One of the checks that Subaru master mechanics use for checking clutch "judder" issues (on all of the MY1990+ 5MT AWD units) is to change (increase/decrease) the front/rear tire pressures from their stock position, e.g., increase rear TPs over the front. The reason, load the center differential using different circumferential tire sizes front-to-rear, and get the clutch to react to the center differential binding/releasing at the clutch. With the proper TP bias (F/R) Subaru viscous LSD center diffs don't bind - which seems counter-intuitive, but it's not in applicability. You have the same reaction on an autobox, just that the electromechnical clutch is getting different reading front-to-rear (when out-of-bias) from the axles, and is loading at that point. Just one more reason to ensure that you're keeping your AWD system happy by keeping your TP bias in place. - Pro amore Dei et patriam et populum - Link to comment Share on other sites More sharing options...
Frogg Posted January 5, 2011 Share Posted January 5, 2011 48 on all 4 Link to comment Share on other sites More sharing options...
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