Well, after catching up with thread today, I've decided....maybe I should keep an open mind about 40 psi. I'm not going to go straight for 40 psi, but maybe increase gradually until I feel like I've reached a comfortable psi since some members have reported braking distance changes.

Yes, I would like to see a magic trick.

 

Yeah this has been an interesting thread for sure

I think some good points have been brought up, I am curious to see how the profile of the tire affects the thresholds. There is a bunch of us in Calgary doing some Autocross in September, is a good opportunity to see what PSI's suit different profiles for max performance and just how much you can push before you get the same exponential failure of traction that I found with mine last weekend.

 

so........Where are the cliffnotes? lol..I want some good gas mileage but also I dont wanna be changing tires every 1k...35PSI?

 

lol, I think this is still debated.

If you ask me I think a nice compromise is 36psi. I personally run my tires at 34psi and I get pretty decent mileage.

 

You're telling you put a straight edge across the tread and all ribs equally touched the edge? Sounds like a shaved tire. Again measure the groove depths.

 

mahout - I do not have a tread depth measuring device. I am merely looking at the wear bar indicator. I will have to purchase a tread depth gauge(how much are they and are they all the same?) and then someone will have to tell me how to use it(the right way!)

Guys, I have been skeptical about increasing the psig in tires from the get go. That is why I did a lot of reading at cleanmpg.com and experimented myself. The proof is definitely in the pudding. I think my pudding is good for now, will it last a long time? I don't know how many miles are left on these tires not to mention the manufacture does not rate or give a mileage for the stock sport tires.

Ultimately I am part of this thread to learn and teach. I want to give out good information and I want to receive good information whether the truth sucks or not.

 

My apologies.
Sorry, it is not my intention, as it may have appeared, to prove you right or wrong, but to find out what you have that may help all of us. There could be a combination of rim width and tire tread width that 'flattens' out better at 40 or even 50 psi.
For example, I would not be surprised to find you wearing 195/55 tires on a 15x7 wheels. When mounted, that combination forces the tread into a concave face surface at 35 psi and perhaps only barely flat at 42 psi and completely flat at 50 psi. Its the geometery of the boundaries of the wheel and tire. And the wear across the tread might be much closer to even than one would ordinarily expect.
We never had the opportunity to test that condition; always we needed to get as much tire tread on the ground with stiffer sidewalls to 'optimize' the track performance. But we don't doubt that the condition you describe could occur with wide rims and narrower tires.
So now having blown my whole case in the making, what is your tire & wheel specs? It won't be as good as if we got them without prior knowledge but it still is an entry in the data base. What's worse we'll probably have to do a whole new data base for the 09's based on the views in the SAE journal. Well, so what. I need something to do in my retirement other than run around racetracks.
cheers.

 

Didn't think it was but i wanted others to understand where I am coming from.

My stock specs: P195 / 55 R15 84H tires and wheels are 15x6

Also, if I didn't make this clear earlier, my set up is strictly for eco. My best mpg to date is 61.5mpg and my average is listed in my signature since I started trying to improve my mpg about 5 months ago - good for me but not the best in a FIT.

 

I've got 3 tread depth gauges! (because I kept losing them, then found both). So far things are even on the Fit and STi. Though with only 5k/year on the STi the tires will probably dry rot before they wear out.

Here's some past experience before hypermiling or the max PSI game ever came into play:
99 Civic Si: 25,000 miles out of stock tires
05 Taurus: 33,000 miles out of stock tires.

If I get that far or better out of the Fit, I will be happy.

 

And really low average speeds.

 

I saw a few mpg difference between two tanks when i pumped up my tires from 32f/r to 48f 40r. I prefer the responosiveness of the higher psi. I also assume that since i rarely carry other people and cargo that using a higher psi (below the 51 max rating on the tire) is safe. I'd just have to lower the psi if i carry excessive weight - esp on the highway.

 

Here's some real results with numbers for a change

I jacked mine to 45psi for 1st 4000miles and for last 4000 have them at 50psi HOT

When new, my factory Dunlaps measured 9.5/32's

I just measured them with 8,300 miles and they are even across and 8/32nds

Now I have been driving aggressive on many corners (My FE driving style), but at a min I can say 1.5/32 got me 8000 miles


Taking them to 3/32's, I have 5/32nds more to go so I can predict end of life at 35,000

PS I love the firm feel of the ride with 50psi

 

Nope. The higher psi benefits higher loads. (up to the 51 psi max of course) Not increasing psi on those Expeditions is why they failed at 80 mph.

 

I can understand the logic in that, however, there's also the manul that says the tires will heat up and have a higher chance of blowout and damage/failure if you have too heavy of a load and high psi. Of course it's dangerous to UNDER inflate tires, but from what i could understand, if i kept the tires at 32 psi i should be able to carry the maximum weight capacity the fit can carry with no issues. Whereas, an increase OR decrease from the factory stated PSI would decrease overall weight carrying capacity (from a safety perspective).

 

From a safety perspective you should use 32psi and never exceed the maximum weight in the manual (which if you look is probably not even 5 grown adults)

However, if you are carrying more weight than normal adding PSI will yield similar results (for tires anyway) as driving on your own.

The tires are typically designed for a wide variety of cars and because vehicles can vary in weight, the recommended PSI from vehicle to vehicle changes. The more weight, the more PSI required.

This is also why tires have only a Max PSI on the sidewall and not the recommended pressure you should use. It is basically the max cold pressure you can use with that tire safely without the risk of blow out or having it blow up in your face. Granted there are safety factors built in, but a few YouTube videos of people getting severely injured is more than enough to make me cautious.

Basically I 100% agree with Mahout, adding a couple of pounds of PSI is beneficial for the car if you are carrying a full load of people or heavy cargo.

 

From an Eco perspective, without doubt, sidewall pressure is better

 

Alright, got it, thanks!

 

I missed that in my manual.Where'd you find that?

 

So..Im just gonna put my tires around 33-35 psi..Keep it stock lol..

 

Check your OEM tire warranty manual - sorry i didnt mean owners manual .
If its not in yours, then i just imagined it. haha.