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Discussion Starter · #1 ·
:?: First, is it possible in for a moderator to set up a 'poll' thread where everyone can post their front and rear PSI figures for comparison?

It would be nice to see as a chart what the overall groups distribution is for front and rear.

:?: Second, I am wondering if having the front at 35 or even lower, and the back at the high PSI (44 or over) would give a good compromise with mpg AND performance?

I don't see any reason to keep the back not at high PSI because it's not the rear that accelerates or needs as much traction in turning, and as long as it has enough traction it won't fly out on a turn - the lower the rolling resistance to the back the better and without a performance hit (other than road noise which can be fixed with sound insulation).

However, for the front, I seem to get less traction with the higher PSI and wonder if it is worth the mpg increase. When I try to back up out of my steep driveway, the wheels stutter a lot at the high PSI, for example.

I'm going to test this out, but my question is:

:?: Has anyone already tried this setup already?

Hi pressure in back, low pressure in front.

I saw some posts about people thinking of different tires in front and back, but maybe you can accomplish the same thing just with PSI differences above the Honda specs.
 

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Discussion Starter · #3 ·
Lower vs higher

Aren't you going to get more traction with the lower inflation, so that if you have the front lower than the back, if anything at all happens the rear might slip more than the front, which would in fact compensate a bit for the front slipping if at all during acceleration or oversteer types of situations?

Having the front lower PSI should reduce oversteer and front wheel drive issues relative to the back. Should it not?

Unless I recall wrongly, the factory specs have the front lower than the rear. The 35 / 44 would just increase the difference more than the factory difference of 35 / 38. It would be less a change than going with 50 psi on all the tires, but still give you benefit of reduced rolling resistance for the rear without losing traction in front for acceleration and steering.

I will have to go check the manual to verify the recommended differential.
 

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Discussion Starter · #6 ·
Rim planes??

I must be thick.

I have no idea what you are talking about wrt the rim plane and tire planes related to PSI.

Horizontal plane? Vertical plane?

:?: Huh? :?: What?

This isn't like underinflating, it is just creating a front/rear differential.
 

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Discussion Starter · #11 ·
Reproduction of test results

I have actually been surprised at how reproducible my test run is when I do it several times in a row.

I have the luck to have a stretch of road nearby which never has a car on it after the late afternoon, is many miles long, has a constant speed limit of 50, and has only gentle ups downs and curves.

I can drive the entire length in 5th and keep the same speed on different runs and come out with almost the identical mpg results if I do trips up and back a couple times within the same evening.

I have done that for cold weather mod testing such as blocking the radiator etc.

http://fungiart.com/insight

I have yet to try it for tire pressures.

Just be sure you do your tests when the temperature is constant and winds are down, and that there are not points where you need to slow down or accelerate which is where you introduce a lot of variation.

You'll be surprised at how well the numbers replicate. I sure was surprised myself.
 

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Discussion Starter · #13 ·
Right on about speed and stopping distance

You are absolutely on the money as far as safety is concerned. If you are driving for MPG, then you aren't flinging around corners and racing in the fast lane so your ability to recover from an emergency is much much greater than someone going 25 - 35 mph faster and driving near their car's limit.

It makes me think I'll go out and bump mine up to 50's. I am still a wee bid skittish, but after a while at 44, it makes it easier.

The flip side is that the safety concern that I have now is that when I am cruising to max my mpg, I have little ability to accelerate in an emergency. When I see that big rig about to run me down from behind, I'll wish I had tweeked for performance! :roll:
 

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Discussion Starter · #14 ·
You are also dead on about how sensitive mpg can be when you are really stretching it for the high numbers. I can come home with a good trip mpg, and then do a 3 way turn in my sloped drive to park the car and blow my trip mileage in the process. Sometimes I wish I lived in flatland.
 

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Discussion Starter · #16 ·
Running over OEM, but differential different

This is diverging a bit, but still interesting to try out. As long as we are talking about having all the pressures over the OEM pressures now anyway, I don't think there should be any issue of too much weight for the tires or too much distortion of the tires. I can't imagine that with such a light car any pressure over 35-38 would cause a problem (given it's only about 450 lbs per wheel).

If we were going to run them well below the Honda specs, then I would worry that they would distort under load, or get hot from rolling at underinflation. Although I've seen some people run them as low as 28 in some posts, and dealers wrongly seem to put them at 32. My initial post (doh!) had the OEM for the front mistakenly at 35 not 38.

Anyway...

Once we are above the 35/38 pressures, I worry only about less contact patch with the road (danger if you need traction vs. mpg) and possible reduced puncture resistance with rough roads, ruts or curbs etc.

My original question has evolved in my mind to why it matters at all to have the rears LOWER than the front when we are talking all over 35/38 realm anyway.

:?: Thus, I wonder if it is wrong to slavishly follow the front/rear differential in pressure when we are running psi way over the 35/38 anyway and there should therefore be no issue of weight support or tire flexing. :?: Why not run the rears at 50 psi for mpg and keep the fronts in the 40s for the extra traction for acceleration and steering?

It's the reverse of the Honda recommendation, but if the Honda recommendation is based upon weight handling and not having too low a pressure for weight, then it only matters that it is above 35. Is the Honda front/rear difference for other reasons than weight distribution of the car?
 

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Discussion Starter · #21 ·
Toyo Tires etc.

Can you be more specific about when you start to see the big difference, under 55 mph? Under 65 mph? (or kmh figures)

It would be nice to have less tracking of grooves, and your description of the handling improvement is very tempting.

Anyone else using these tires out there?

What PSI are you running them?

For a 10% hit in mpg, how would it compare to just running the stock tires at the Honda pressures?

Thank you!
 

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Discussion Starter · #22 ·
P.S. toyo PSI

Me again!

Is the Toyo rating 44 max PSI?

Have you tried pumping them up to 50 like folks do for the stock tires?

If so, how does that change your handling and your mpg?

If not, are you game to try that and report?

I wonder if a high PSI on those tires would give back some of the mpg hit, and at the same time retain the handling benefits!

Honda engineered the car around LRR tires at 'stock' kinds of pressures, and since folks are running well over stock pressures, maybe other tires can perform well on both fronts.
 

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Discussion Starter · #28 ·
I run them all the same in the high 40s to 50 with both stock (GF's Insight) and Yokohamas.

I agree that in practical tests, the lower PSI does NOT seem to give better performance or traction.

The best example to me is that in my Honda Element with stock tires at about stock inflation the front tires would chirp on virtually every start (manual transmission) and I would get oversteer frequently. Then I bumped up the PSI. Suddenly, the chirping stopped almost completely...

Even if there might be more contact patch, it is a sloppy soft contact, and cancels out the increase in quantity by decrease in quality.
 
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