Tire Pressure Recommendation?

[azncapcom]

Just wondering what is the recommended pressure to run your rollas at with low profile tires?

For example, since the tire has lower profile, which means it fits less air, shouldn't more PSI be required? I know lower profile comes in wider tires to make up for that loss air, but what if your decreasing the profile more than the width? Is there some kind of calculator to calculate total air volume?

I.e. wouldnt 205/45/16 require more PSI compared to 215/45/16?(wider holds more air) Instead of putting the recommended 30 PSI all around from the owners manual?

Also what PSI do you guys run at? PSI @ stock tires and PSI @ larger wheels.

[fishexpo101]

Depends on the tire and what your ride preference is. Not everyone runs the same PSI for a given tire size, application - suspension modifications, ride quality, driving conditions all come into play.

I would recommend using the OEM 30PSI as the lower bound for air pressure, the tire will have a stamped max cold inflation - use that as the upper bound for the tire pressure. Most lower profiles tires usually have this upper limit at 44PSI to 51PSI+.

Most find the right pressure is likely to be somewhere in between - easiest way to find out what pressure works for you, is to pump the tires up 4-5PSI of max cold inflation (you can get closer if you have a better air pressure gauge). Drive the car around normally, see how it rides/handles. Let the tire completely cool, bleed it down 2PSI - repeat. Once you hit that sweet spot, you've found your tire pressure.

Ideally, you use a precision tire pressure gauge and a contact tire pyrometer (temp gauge) - measuring the tread face temperature for various tire pressure. The "correct" pressure is the one that yields the most even temperature across the entire width of the tire tread. But since many cannot get access to these tools - have to do the old trial and error way.

Personally, I tend to run much higher pressure than average. Examples: Running 48PSI-50PSI on Goodyear RS-A OEM A/S tires (205/55-16) on the Matrix, running 38-40PSI on the Exclaim UHP tires on it now (205/55-16). On the Corolla - the OEM Goodyear Integrity GL tires (185/65-14) - ran them around 44-46PSI, Yokohama H4S (196/60-15) running 40-42PSI, had Kuhmo ECSTA Supra 712 and Yokohama AVS-ES100 tires (205/45-16) also running around 40-42PSI.

Since my driving is primarily highway (80-160 mile commutes daily) - the higher pressures are much more of a benefit for my driving conditions. If I was running 50/50 mix of city and highway - I'd probably drop the pressures about 5PSI across the board to give me a little more compliance in the sidewalls.

[PhatRoyale]

For 45-series tires, I would go at least 40PSI and work up form there.

Check the maximum recommended pressure on the sidewall first.

[azncapcom]

fishexpo:
doesnt running that high PSI reduce your tread contact patch to the pavement? Also would that not cause uneven wear, for example, the middle of the tread wears faster?

When i got the tires, the PSI was at 30 all around. It was somewhat obvious that 30 PSI was short (the middle of the tread had alot less wear than outside) So i imediately increased it to 35 PSI. @35 PSI the ride comfort was good, however i still didnt like the sag that i was getting from the tires, so i raised it to 38 PSI. Now at 38 PSI, rides a little harder but still not bad. However, i did notice that the turning grip wasnt as great at this pressure. When you depress the pedal down from a stand still doing a quick turn (with oncoming traffic and you dont want to wait) The tires start to slip. Would this mean that 38 PSI is a bit too high and im loosing some contact patch? i dont really notice much difference in the stopping grip though. I have a decent pressure gauge but where can you get one of those tire temperature measuring things that you are talking about.

phatroyale:
the max psi would be 50. Going over 40 PSI would give a really harsh ride would it not? Also worried about the contact patch with that high PSI. I do both city and highway. running that high PSI in the city with all the potholes is not a good idea. I do avoid almost all potholes i see, however my brother is much more lazy and just runs over them... that was fine with the 65 series sidewall... but with low pros, i told him its a nono.

[PhatRoyale]

Higher tire pressures = firmer ride.

But not really harsh, no. 45-series tires are not really low-profile..... still provide a decent amount of comfort. My buddy runs 45-series on his Corolla and hits the odd pothole at it's still okay. All depends on the quality of the tires you have. I find that higher tire pressures tightens up the car's handling and makes it turn in quicker.

I run 40psi on my 195/60/14 tires.

[azncapcom]

Higher pressure may make it turn quicker but doesnt mean it has more traction. i think lower pressure has more traction cause of the extra drag. how fast can you push your turns without making it lose traction?

The fastest i tried was 50km/hr (i think thats around 35mph?) the tires starting whirring signalling its about to loose grip but not quite. havent tried to push it any further than that?

yeah that ride is actually not bad at all with 38 PSI, just that my struts are worn, so the rides kinda wavy when theres curves on the road.

[fishexpo101]

How fast you can push it is also a function of tire tread design and tire compounding. Some tires squeal when they are approaching the limit of traction and smoothly break away. Others grip right to the hairy edge and then you are off into the weeds.

Having too high of a tire pressure will decrease grip (traction) and can lead to a very harsh ride. Also tends to sharpen the steering and provide a cushion against many road hazards. Though much depends on the suspension and the tire construction/compounding.

Having too low of a tire pressure will increase traction but will be subject to heavy tire temperature fluctuations. Heat will kill a tire very quickly. Ride will be more supple as there tends to be more sidewall compliance, some tires like lower pressures.

Many of the low profile tires use a beefier sidewall support structure as well. This can influence turn in "feel" - more than absolute traction. This extra structure can also be misleading. A tire can look like it is only slight short of air (15PSI or so) but be completely empty. Car could even run fairly well with a low tire, because of the extra support, but a couple miles on a deflated tire will automatically scrap it.

Just play around with pressures until you find the best compromise - having worn struts makes it tough to dial the pressures in, but you can get pretty close.