car low profile tire PSI

WWJD

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gots a car with 17" low profile tires on it. Miata stardard 14" rating is 26 PSI front and back. I asked at two tire places - one said "I just go by what it says on the side of the tire...". Mental note to never take my car there and let them touch anything on it. Other place said just use the car's rated PSI. How can that offer enough pressure against road bumps and not damage the rims?

So, I'm toying around with PSI [maybe I'm just too anal about it] to get a good ride, be above the car rating and below the side wall which labels the "MAX PSI" to use with the tire, not a good recommended starting point.

I'm hovering tween 28 and 31ish, sort of aiming at 29 or 30.

Do any of you KNOW what low profiles tires are supposed to be set at? SPILL IT TO ME!

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Its really up to you. Assuming you do not exceed the MAX pressure that is. Less air means a LITTLE softer ride with more traction but less acute steering abilities. (The tires flex before the suspension does creating a small Lull in response) The more Air the firmer the ride and the longer the tire life. Be sure to maintain a good traction patch no matter where you end up. Too little air and you'll ride on the sides of the tires wearing them out prematurely and risking sidewall damage. Too much air and you traction will suck and the middle of the tire will go bald FAST! Hope this reply of ambiguous advice was Helpful? I can tell you that whoever said to follow the Miata's specs was pretty much an idiot on this subject. I am 200% Sure that Mazda does not print the tire inflation specs for tires that will be manufactered 4 years AFTER the car is produced mated to a NON OEM Rim!
The long and the short of it is that there really is no absolute answer.
 
I thought the tire pressure in low profile car tires was supposed to be really high... Like in the 40's.... But what do I know... I ride a Busa and drive an SUV
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Hmmmm tires, always a great subject. The proper tire pressure for your car is what is printed on the white label on your drivers side door jam. In this case it is 26 psi. The reason to follow the manufacturers pressure is in the testing of their car they have found that that particular tire pressure gives you the best handling, tire wear and fuel economy. Yes tire pressure effects fuel economy. But having said that, that is for the stock tire size which was probably a 195/60/14 or something like that. Now that you have changed the tire size the geometry is going to change a bit.

Your new lower profile tires have a very stiff side wall with not alot of flex. So you do not have to worry about any damage occuring to your rims. With 26 psi in them there is more then enough air to prevent any damage. The only way you can damage your rims is if you curb then when parking or if you hit an object on the road. But 26 psi would be a bit low for your low profile tire. you were pretty much dead on around the 29-31 psi mark. I would run 32 psi cold (check them first thing in the morning) and that is more then enough. You will get proper tire wear and good handling. The tires look fairly wide so you will have a good contact patch at all times.

The one tire company that told you to run them at MAX which would be 40-44 psi are out to lunch. That would cause a very uncomfortable ride. Such high air pressure would not allow any shock absorbtion from the tire and that is needed.
Not for daily driving needs anyways.

Hope that answers your question! Good looking car btw. Have you done any other mods to it?

CB
 
thanks tons for the input guys! Helps my confidence hearing from others about this. sounds like I'm in the ball park. I really enjoy the handling when they were at 34, but I ALSO really enjoy the smoother ride at 28
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dang compromises!! I had read about how those low rider cars were blowing up tires because they overheated and would like to avoid that. I guess they were running way too low PSI causing flex > heat > pop!

I bought this car used as is, and it came with an upgraded stiffer gas shock / sway bar suspension system - so that adds a lot to the bumpy ride also, but also the nimble steering... fun taking a RIGHT TURN in town at 35mph without touching the brake!!
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The engine is stock and that is fine by me - I get my speed fix elsewhere... if ya know what I mean [wink wink]

Anyone know if gas shocks make an "air" fssst sound when hitting bumps at low speed is normal? Maybe they are all trash and need replaced. FEELS like they work fine, jsut never heard that before. all four do it and it might be normal.

First mod: Pioneer 50W x 4 !!! Gotta roll with tunes. Might be adding a bass unit in the back: tiny car with top down REALLY lacks low end

thanks for the input!



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Reason for Edit: "mroe typoos than i cuold allow"|1124652363 -->
 
gots a car with 17" low profile tires on it. Miata stardard 14" rating is 26 PSI front and back. I asked at two tire places - one said "I just go by what it says on the side of the tire...". Mental note to never take my car there and let them touch anything on it. Other place said just use the car's rated PSI. How can that offer enough pressure against road bumps and not damage the rims?

So, I'm toying around with PSI [maybe I'm just too anal about it] to get a good ride, be above the car rating and below the side wall which labels the "MAX PSI" to use with the tire, not a good recommended starting point.

I'm hovering tween 28 and 31ish, sort of aiming at 29 or 30.

Do any of you KNOW what low profiles tires are supposed to be set at? SPILL IT TO ME!
Thats a good looking car
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I'm not sure if this applies to low-profile tires or not, but...

Get yourself some sidewalk chalk like the kids play with, then find a nice smooth section of pavement...NOT in the middle of the freeway
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A protable air tank will be needed for this, or do the test near a gas station.

Cover most of the tread on one of the rear tires in chalk. Slowly roll the car forward. Now, inspect the pattern made by the transfer of chalk onto the pavement.

[*]Full pattern transfer - Very close to proper inflation. You might be able to adjust it slightly for added performance.
[*]Outer Edges transfer only - Tire pressure is too low. Add air pressure and redo the test.
[*]Center transfer only - Tire pressure is too high. Lower air pressure and redo the test.

Good Luck Greg
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Or...you could just use the Mfr's recommended pressure.
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thanks tons for the input guys! Helps my confidence hearing from others about this. sounds like I'm in the ball park. I really enjoy the handling when they were at 34, but I ALSO really enjoy the smoother ride at 28
smile.gif
dang compromises!! I had read about how those low rider cars were blowing up tires because they overheated and would like to avoid that. I guess they were running way too low PSI causing flex > heat > pop!

I bought this car used as is, and it came with an upgraded stiffer gas shock / sway bar suspension system - so that adds a lot to the bumpy ride also, but also the nimble steering... fun taking a RIGHT TURN in town at 35mph without touching the brake!!
biggrin.gif
The engine is stock and that is fine by me - I get my speed fix elsewhere... if ya know what I mean [wink wink]

Anyone know if gas shocks make an "air" fssst sound when hitting bumps at low speed is normal? Maybe they are all trash and need replaced. FEELS like they work fine, jsut never heard that before. all four do it and it might be normal.

First mod: Pioneer 50W x 4 !!! Gotta roll with tunes. Might be adding a bass unit in the back: tiny car with top down REALLY lacks low end

thanks for the input!
For that extra bit of HP that its missing, you could always do the "Monster Miata" mod.
 
I had 17" wheels on my 98 Golf GTI and they were 215/50ZR17 and I ran 32 PSI in them. Car was lowered and handled like it was on rails.
 
This thread could turn into one of THOSE threads. Yikes!

The way I understand it is this: The max tire pressure on the sidewall of the tire is the proper tire pressure to use. The tire makers know what makes a tire work optimally, bottom line.

During the Firestone trial a few years ago, Firestone argued that the pressures being used were too low. Automobile manufacturers were recommending to consumers that they use pressures too low for the tire to function properly and that therefore they were blowing out. During the court proceedings it was determined that this was, in fact, true. (It was also show that Firestone's tires were defective which is why they ultimately lost at trial).

The bottom line is, however, that TIRE manufacturers recommend you always use the MAX printed on the sidewall.

If you use the max, and you still have other performance related problems, it's time to check the suspension, alignment, driving habits, etc.

Well, that's what I heard, anyway!

--Wag--
 
wag, I used to think that too but I am not sure it is correct. The "MAX PRESS" listed on the sidewall is just the MAXIMUM amount PSI you should EVER put in it, as well as listing the maximum weight load (?) it can take. The car's rating is designed around that particular car's weight. For example my front engine/front wheel drive Civic has tires on it that say "MAX PSI 35 LBS" or simialr, yet due to my cars light weight, Honda says 30 psi front, 29 rear to produce proper surface contact with the tread. That max press would change per vehicle weight - less PSI for a Yugo, a lot more for a Mercedes Titanium Class with the bullet proof windows and body armor.
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If I had 14 inch factory rims on this Miata, I'd run 26 PSI, but this low profile thing is new to me. I been tooling around a while and am very happy in the 30 PSI zone now

Yes that Firestone thing was a mess. In the end I read the dealers were lowering PSI UNDER the vehicles recommended so teh ride would be smoother to potential buyers on test drives: "... All the truck like features, yet rides like a Caddy!" Yeah, right. Until you melt the tires doing 80 for 6 hours across the start and die in a firey highspeed wreck.


STKR, I'm not falling for that CHALK-SCAPADE!! I know you just want me to look silly in a parking lot, with multi colored kiddie-chalk, drawing on my tires like a 7 year old while trying to explain that to Mall Security! :p
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or, tomorrows headlines:

"Man dies in firey low speed accident as car tires explode from sliding around mall parking lot on chalk!" hahahaha

Kiddin ya, Jim. ;) That sounds like a great idea, I get exactly what you mean. If I try it I'll post pics
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You can get the same results by doing burnouts at different pressures and looking at the black marks, but as you roast the tires, the dam pressure changes and thows everything off.
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Could be more fun than chalk though.
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...and...I was serious about the chalk...read it in Car Craft years ago.
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Always stay close to the tire manufacture's rating. Did the car company make the tire?
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Noooooo! I always set mine at the tire's recommended pressure, then adjust to desired feel. The tires will last longer, and grip better near the reccomended rating.

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Tru, listed on tires is the MAX PSI, not the recommended PSI for your vehicle weight. If it's overinflated, it wears out the center first if the car is not heavy enough to require that High PSI. I get less grip cornering on over inflated - less sruface contact... but it's fun
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I'm starting to worry about you guys!!!
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The correct setting is listed on the car itself, not the tires.... unless you slap on some funky low profilers

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If the tires only list the mzx rating, you can always set it lower. I've had a few vehicles that recommended tire pressure that was higher than the max rating for that car. As long as you don't exeed the max rating, you'll be fine. But if you set it to low, you'll risk the bead seperating from the rim.

Nice car. Enjoy!
 
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