Norm Peterson

For tires, maybe look into 255/70's on the OE 17x8 wheels. It's a legitimate fit on 8's with a little more sidewall shape than the OE 235/55's.


Norm

Mr. D

Thanks for the advice guys! I appreciate it! My '08 is a toy so tire mileage isn't an issue... mainly because I don't even have 9K miles on it yet & it still has a new car smell!

Jazzer The Cat

my car stinks!

Mr. D

Maybe it's those bean & cheese burritos you are eating!

By the way, remembering the basics from all my past "empty bed" pickups, the air pressure should be related to tire shape & amount of weight on the tire. I'm going to work with lower tire pressures in the rear where there is very little weight! Going from 32 to 29 psi made no noticeable change in tire shape & handling was just fine, so I'm going to try 27 psi to improve the ride! I suspect it will handle just fine also.

Jazzer The Cat

Just do a bit of pushing into some corners prior to the continuing of lower pressures. You may not be into hard cornering as a rule, but at some point, you WILL end up needing a quick turn fast for any number of reasons. Maybe someone cuts you off and you have to turn suddenly. Maybe you are booking down a fast straight and a cow suddenly jumps out in front of you. OK, being a little silly, but a tire that is under-inflated, is apt to roll over onto the sidwall and can introduce some pretty serious understeer, so just drive for a while each time you lower the pressure a bit. There will come a point at which any lower will be bad for the tires, so do some research and talk to your tire shoppe for a bit of input on what to expect along with a softer ride.

Jazzer

Norm Peterson

When you drop the rear pressures down, it's a good idea to keep the front tire pressures up. They aren't where the majority of the sting going over sharp bumps comes from anyway.

In fact, with the extra weight of all that forced induction equipment up front, you probably should be running a little more air in the front tires than sticker for a normal '08 GT (32 psi). Maybe about +1 psi in each front tire per 50 or 60 extra lbs, unless Roush has specifically recommended something else.

A little pressure stagger like that can loosen the handling slightly, courtesy of slightly larger rear slip angles. But the rear also gains a little mechanical grip as long as the rims are wide enough, so you can also gain a little more margin against the rear end of the car deciding that it wants to lead the parade for a change.

The 235/55-17 and 235/50-18 are both mounted on wheels which are either at or just below the max recommended rim widths, which should cover the "wide enough rims/adequate lateral support" issue.

I've intentionally run the rears as low as 28 with the fronts at 33 and driven as hard as usual without anything unpleasant threatening to happen. This is for a normal condition of nearly empty trunk, most of the time just me on board but occasionally my wife (call it 1.5 people?). But the usual "YMMV" applies, and anybody who wishes to try doing the same should sneak up on it slowly and with careful observation of the car's behavior.


Norm

Mr. D

I think I'm losing it! I checked the rear air pressure in my Mustang & I have running 29 psi in the rear! It has been handling for me just fine. I dropped it down to 27 psi & it shows no change in tire shape (squat) since the rear of a Mustang is pretty light compared to the front axles. I'm going to play around with pressures from 25 to 27 psi & see how it handles in emergency type moves. I suspect that around 25 psi will be a sweet spot for both ride & handling! Wa-chu-tink?

How do you like the one cylinder diesel hot rod I had in China?

Norm Peterson

About 26 will trip the TPMS lamp, which even the combination of 28 plus driving through a sidewall-deep puddle of cold water will do.


Edit - I'm trying to think how a diesel single would sound . . .


Norm

Mr. D

Good to know! Didn't think of that! If the lamp comes on .... I'll know why!

Norm, Answering your question about the 1 cylinder diesel tractor: Ever hear an old farm, single cylinder, diesel water pump at a county fair display? The make a pac... pac... pac... pac... pac sound! In Asia the unit you see in my post replaces our 1 ton pickups for about $700. No electrical at all, gravity feed fuel, water cooled from a metal pot on top of the engine that cycles water without a water pump simply by heat convection, a crank to start it, & a 2 sp. tranny belt fed to the rear wheels. The front end is like a tricycle & it has many rear ends that attach by U-bolts depending what you need from a pickup bed to cultivation tools! They go about 35 mph & are indestructible! They are as much a trip as the friendly people of China! They have so many types of vehicles of different speeds that the use all 4 lanes going one direction like playing chicken & just make way for on coming traffic! Sound's crazy, but from Shanghai to Beijing I didn't see one accident because they are so cooperative! If a person with a comm'l license breaks a traffic law... the police chew them up on the street & they go to traffic school for days, but you feel safer at midnight in their cities than ours! Don't believe everything you hear on "Corporate TV!" Sorry if my answer is too long... not meaning to highjack my own thread... if that's possible! Huh!

Mr. D

Norm,

Check out the thumbnail of the Chinese 1 cylinder diesel I mentioned! Don't you wish you had one to take to a cruise night?