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I know most of you guys are out there tonight "gettin' sum", and I do envy you just a little bit, but when you get to be 40 you have to satisfy yourself with lesser pursuits - so tonight I'm thinking about: tire pressures.
First of all I am a fanatic when it comes to tire pressure. I play with it constantly to achieve my personal "sweet spot". I believe our cars are sensitive to even small variations in pressure and that handling balance can be altered by even minute adjustments. One thing I've noticed throughout the TL line is the constant recommendation of 32psi in the rear. My 03 TL-S recommends 32/32. 04 and 05 TL is also 32/32. 06 and 07 TL is 33/32 (I believe). 07 and 08 TL-S is 35/32. In considering this I believe this recommendation comes from the manufacturer's desire to maximize grip on the rear axle given the many possible road conditions the driver might face. This makes sense, of course. After all, these are sedans that are designed to cart the whole fam damily and in all sorts of weather - rain, snow, sleet, hail, dry... But for us enthusiast types, this achieves just the opposite of what we want - by maximizing rear axle grip you are effectively creating more understeer up front. Not something that we need with 60/40 weight distribution and FWD. So, while 32psi might be right on a wet road, it certainly can't be right under dry road conditions.
If 32psi isn't right, then what is? Well, since we would like the rear-end to dance a bit (oh, wish I was "gettin' sum") we could choose any pressure that might make the rear of the car break away sooner (than 32psi, at least , and ideally before the front wheels, if possible). Because 32 is where maximum grip occurs in the rear, we could inflate the rears to more or less than that - both are going to cause earlier break-away.
Ideally, of course, you would also be playing around with the front pressures to arrive at the point where they achieve their maximum grip. This is critical for FWD cars. Knowing this place (psi) will also help to minimize understeer, which is what we need to do. Also, whatever number this is it should be greater than the rear psi because the front end is carrying more load and as such has a larger slip angle - using more pressure up front helps to offset these differences in slip angles.
Anyway, did I mention that I'm certainly no expert on the subject? I'm just reporting on my experiences so YMMV. But congratulations if you made it to the end of this long and winding road. Now, where was I? Oh yeah, "Honey!!....".
^^^ I also run 35psi front and rear on my car. Just preference, no science behind it. It's just easier to set my air compressor to the same psi to inflate my tires the same all the way around than to change them between 2 different psi. Kind of lazy, but, it works for me!
In the case of the TL, there are also differences in PSI between the manual and auto transmission, as well as A-spec 18" vs standard 17" wheels. Dug-mac's specs are for the standard 5As. The 6Ms are all 35F/32R, and the A-specs are 39F/35R (I think; unsure about the R PSI).
The recommended tire pressures are the manufacturer's guesstimate for the best compromise of ride, traction and control for the greatest number of likely car owners. The more PSI, the stiffer the sidewalls for better grip/response in turns. With the FWD TL, decreasing understeer requires increasing the front PSI relative to the rear.
We owners can adjust to whatever feels most comfy for us-- whether that is a more serene ride (32 F/R), better steering response (inversely to a firmer, more sensitive ride/feel), or more response and less understeer.
I ended up at 37F/34R and 36F/33R as the preferred pressures on my stock 5A with the Michelin MXM4s. The only change in ride/feel is for the better, IMO.
YMMV with different tires, a Comptech or 6M RSB, suspension set-up, etc.
The kids should be asleep shortly, so this 42-year old is getting together with the wife after exiting AZ-- she'll see something long other than the road soon, blue pills and toys unnecessary!
From the posts of yours that I've read on here you're as fanatical about tire pressure as I am. Seems like we're in general agreement with regard to pressures and front to back balance. I have just three words for you...
Adjusting air in the tires is the quickest, cheapest and easiest way to affect handling and feel of any car (and I'm admittedly cheap and easy ), so it makes sense to take advantage of it.
Besides, with a background of losing too many SCCA autocrosses in my long-departed youth and putting much better tires on cars than some of them merited, a bit of trial-and-error experimentation on the TL's tire pressures was inescapable to get the right feel (for me) for street driving,
How did you arrive at those numbers? Trial and error or some secret science?...
Hi dug-mac,
No secret formula. Wanted to keep the air pressure balanced per manufacturer's recommendation (with delta of -1 for the rear tires). +2 PSI to all 4 tires felt right for me. Did not experiment with more or less.
I did the same with my Accord but +3 felt better than +2 to all 4 tires. That could be due to 4 people (my wife + kids) in the Accord Vs. 1 (myself) with the TL.
SUMMARY: NITROGEN IS GOOD but not that good. — there is no true or real benefit in using nitrogen over compressed air. However, keep in mind that if you plug the benefits of nitrogen over air in each category and apply scientific reasons and graphs you’ll see that there’s an absolute benefit to using nitrogen each and every time over every category.
However, this benefit is negligible or tiny when weighed in the real world. My opinion is that if someone offers you nitrogen of course take it. But don’t go out of your way to get it. Also, no one has mentioned the idea “why” hot tires increase in pressures.... => normal compressed air causes condensed gas water vapors to solidify into water in the bottom of storage tanks which gets into your tires. This creates heat and friction and expansion later when the water heats back into gas and expands as the tires performs. Not an issue with nitrogen.
Cooler running temperatures: When air is pressurized, the humidity in it condenses to a liquid and collects in the air storage tank you use at the local gas station. When you add compressed air to the tire, the water comes along for the ride. As the tire heats up during driving, that water changes to a gas, which then expands, increasing tire pressure. Because nitrogen is dry, there is no water vapor in the tire to contribute to pressure fluctuations.
SUMMARY: NITROGEN IS GOOD but not that good. — there is no true or real benefit in using nitrogen over compressed air. However, keep in mind that if you plug the benefits of nitrogen over air in each category and apply scientific reasons and graphs you’ll see that there’s an absolute benefit to using nitrogen each and every time over every category.
However, this benefit is negligible or tiny when weighed in the real world. My opinion is that if someone offers you nitrogen of course take it. But don’t go out of your way to get it. Also, no one has mentioned the idea “why” hot tires increase in pressures.... => normal compressed air causes condensed gas water vapors to solidify into water in the bottom of storage tanks which gets into your tires. This creates heat and friction and expansion later when the water heats back into gas and expands as the tires performs. Not an issue with nitrogen.
Cooler running temperatures: When air is pressurized, the humidity in it condenses to a liquid and collects in the air storage tank you use at the local gas station. When you add compressed air to the tire, the water comes along for the ride. As the tire heats up during driving, that water changes to a gas, which then expands, increasing tire pressure. Because nitrogen is dry, there is no water vapor in the tire to contribute to pressure fluctuations.
Thanks for bumping a thirteen year old thread with useless information.
@sdarryl64 Reporting posts unnecessarily is a bigger offense than you being hurt by his sarcasm.
With that said, welcome to the forums and thank you for the additional information. What has always
made this forum great was sharing information from research and your own trials and tribulations!
@horseshoez is in his 60's...he was just politely asking you to get off his lawn.
Well, I was eight years old then, I didn’t get a chance to read it.
think harder and be sweet
you been reported to the administrator
Seriously? You bump a very old thread and post questionable information and then don't like getting challenged on your netiquette so you report my post? Yikes, well done.
Since you want to play @sdarryl64 , got any citations to backup your claim? Curious as to where you came to that conclusion (not that I don't believe you, just playing devil's advocate )
09-29-2007 | 08:06 PM
Rethinking Tire Pressure
My long road before going with the missus...
), so it makes sense to take advantage of it.
