Tire Pressure Blues

"D" (danjee) 09/15/2013 at 21:33 • Filed to: None

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26

I got new tires a few weeks ago and decided to check their pressure levels. They read (front/ rear, right/left) FR: 36, FL: 34, RR: 32, RL: 36. So I'm going to equalize them, but I don't know to which psi.

I'm guessing this is this one of those across-the-board things since the tire doesn't give a rec. value (only max pressure).

While we're on the subject: Autocrossers increase their tire pressure for performance gain. Are there disadvantages to doing this on a daily driver?

UPDATE: According to Miata.net, the manual calls for 26 psi. Now I'm cornfused.

The Opponaut formerly known as MattP123 > D 09/15/2013 at 21:37

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Easiest would be to let air out until they're all at 32, otherwise you gotta lug out the compressor or head over to the nearest gas station. As for the recommended psi, if they are factory wheels/tires, check your manual or door jamb stickers? If not, then not sure.

D > The Opponaut formerly known as MattP123 09/15/2013 at 21:39

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Factory wheels with OEM-sized tires. Already checked the door stickers (nothing) y no tengo manuel.

dogisbadob > D 09/15/2013 at 21:42

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What car is it?

IDDaVo - Now has a Toy Yoda > D 09/15/2013 at 21:43

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Did you check the back of the gas cap door?

D > dogisbadob 09/15/2013 at 21:43

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'93 Miata

doodon2whls > D 09/15/2013 at 21:45

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Srsly ? Driver's door sticker doesn't have tire data ? That's odd... What year/make/model ?

A/X tire pressures are not good for long distances. You'll wear the center of your tire tread prematurely. The higher pressures are a poor-man's way to reduce tire deflection/rollover onto the sidewalls instead of a big negative camber alignment.

D > IDDaVo - Now has a Toy Yoda 09/15/2013 at 21:46

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Yeah, and the underside of the hood. Nuttin

D > doodon2whls 09/15/2013 at 21:47

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It says a lot but not this... 1993 Miata

The Opponaut formerly known as MattP123 > D 09/15/2013 at 21:48

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Supposedly Firestone's web site has a tool to find recommended pressures. I can't find it though:

http://www.firestonecompleteautocare.com/tires/tirepres…

The Real Dacia Sandero > D 09/15/2013 at 21:51

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Start with 28psi and go from there. Any higher and you're just giving yourself a bad ride. What tires did you get?

D > The Opponaut formerly known as MattP123 09/15/2013 at 21:52

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Like Miata.net, they say it's 26. This seems way too different than the levels I got. I even checked twice.

D > The Real Dacia Sandero 09/15/2013 at 21:54

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Yeah, apparently factory rec. is 26. They're BFG G-Force supersports.

These tires are apparently overinflated but don't at all seem to detract from ride quality..

doodon2whls > D 09/15/2013 at 21:56

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26psi seems too low. I would go with 32psi as a safe starting point and go from there.

dogisbadob > D 09/15/2013 at 21:58

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I think Mazda actually says 26 psi,from what I've been able to find online

There's no placard anywhere on the car? On either door, on the frame, under the arm rest, or even in the glove box?

D > dogisbadob 09/15/2013 at 22:04

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Miata.net and Firestone both gave me the same number. I suppose I could scan the entire car but have already checked the obvious places.

MountainCommand > D 09/15/2013 at 22:05

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personally, ive been running tire pressure based on the number on the tire. Tire max is 50 for me. I do about 40-42. The door states 32psi.

I figure since im not running the stock tire, ill go by what the actual tire manufacturer says. Plus it doesnt hurt to add a little extra mpg's here and there.

maybe im wrong, but ive never had an issue.

D > MountainCommand 09/15/2013 at 22:07

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Would the car corner or braking-nosedive any firmer if I upped the psi a bit?

MountainCommand > D 09/15/2013 at 22:22

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I feel the car is a bit tighter. However the bumps are much more noticeable. However, the butt-telemetry is a hard one to read.

In theory yes, since the weight shift would put more weight on the outside tire, if there is more pressure it will be more resilient against compression or deflection. But dont quote me as im not a engineer major. But logically, that seems like it should be correct.

If you are worried about blowing up a tire for fear of over inflation, i suppose just go to youtube and watch just how much psi these things actually take before catastrophic failure.

D > MountainCommand 09/15/2013 at 22:40

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Yeah I wouldn't get anywhere near the limit. I might just do 36 all around and see how that works out.

MountainCommand > D 09/15/2013 at 22:44

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wouldnt hurt to try. Whats the worst that could happen (clarkson quote?). uneven tread wear? pshhhh youll be sideways on those slicks in no time. do a calculated mpg run too. See just how much difference youll get in the miata.

When i see 36psi, thats almost low for me haha. Others might say its high, but it really comes down you your preference.

D > MountainCommand 09/15/2013 at 22:49

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I'll give the situation the ol' "feel it out" test

The Real Dacia Sandero > D 09/15/2013 at 22:59

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28 is what's recommended on the forums.

Those are the tires I run. You'll love them. They have just enough grip for a stock street Miata. They are pretty forgiving too.

D > The Real Dacia Sandero 09/15/2013 at 23:30

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I'm definitely going to opt for a higher grip tire next time, as well as a 15" wheel. But that'll be quite a ways off, so I got time to save.

The Real Dacia Sandero > D 09/15/2013 at 23:35

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Same here. Although I may stay with 14s like the oem bbs wheels.

Sethersm > D 09/16/2013 at 14:21

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So... the following thoughts occur:

1) Tire guys couldn't find a reccomended pressure, just randomly set them to about where they are (one low so soon makes me suspect a leak).

2) Tire guys know 26 is reccomended, but set them higher for some reason (one low so soon makes me suspect a leak).

3) Tire guys set them to whatever, but as the whatever doesn't seem to jive with either reccomended or max rating, perhaps your gage is wonky? Still a possibility of a leak, but a wonky gage might throw a more wonky reading on one tire... Make sure you're using a good gage.

MountainCommand > D 09/16/2013 at 19:46

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attaboy! Trial and error is the way to go!