DCSilvrEvo

iTrader: (5)

WHAT THE FCK THAT SHYT MIGHT AS WELL RACE WIT INDY CARS!!!!!!!!! Downforce for days!

erioshi

Those presures sound really high to me - especially for street use. While those inflations will probably give you great fuel mileage and a very "tight" feeling car, actual stability might be suffering badly.

A real world example of this from my past was that my wife had just gotten new tires for her car and took it out for a weekend trip - about an hour after she left I caght a call from her - she had to do a "panic stop" and the car did a full 360+ and then went backwards into the ditch.

Wen we got the car to a truck stop down the road, I checked her tire presures as part of going over the car - the tires were really over-inflated. What happened was the they were so pumped up that the extra presure has made the contact area of her tires smaller than it shold have been. In addition to that, the extra presure also prevented the tires from using their "natural give" to help keep the tread blocks from slipping when she had to dynomite the brakes. Instead the car essentially acted like it was on ice or wet pavement - once the contact patches had broken free the very high presures let the car just keep sliding along on it's very small and hard contact patches.

While it doesn't sound like your car is anywhere near that bad, you might want talk with somone who knows the Khumo ECSA ASX very well. Even when I run my car at the track, I usually am running lower presures (cold) then you have posted in my R compounds.

TexasRS

Anyone else with kuhmo ecsa asxs (or similar tire) care to chime in on whether or not 45psi (or even 40psi) will cause instability during breaking and/or driving? Thanks.

rsr14

iTrader: (1)

Sweet pic of that Audi. German touring cars are insane!

Stephen Fisher

iTrader: (1)

The twitchiness that I was initially referring to was experienced on high speed sweeping turns (130 plus mph) on a road course. There was external wind, but the back-end was definately light and hopping.

I think that this is the reason that Mitsubishi introduced the vortex generator and hope that this adresses the issue. I do not believe that these conditions could be felt in street driving and not in a straight line.

Kayaalp

iTrader: (1)

Rice? I don't think so! Everything on these DTM cars is pure function. They're probably the fastest and most highly-developed touring cars on Earth.

Emre

erioshi

Oh, another quick point about tire presures. I wouldn't run quite as much presure for the street or on the road course as I would for an AutoX set-up. On the road or track the car will spend alot more time "at speed" putting heat into the tires and creating a higher "hot" tire presure than you would find after a minute or 2 of dodging cones.

The exact increase will vary based on a variety of factors (including the tire), but it's just something to keep in mind.

CDO

iTrader: (2)

I agree. The max tire pressure written on the side of a tire is not what you're supposed to go by. The tire manufacturer has no idea what car that tire's going on. That's merely the max that tire is rated for.

Car manufacturers take a tire, drive it around and figure out what the best setup is for a particular car. 32/29 is what they recommend for the Evo. 45 psi is roughly 40% over that.

jbrennen

iTrader: (1)

The manufacturer's recommended pressures are a "best guess" based on the combination of handling, safety, fuel economy, ride comfort, etc., based on a typical mixture of weather that the car will see, and assuming that the tread depth is anywhere between full tread and almost bald.

On any particular day, for any particular driver, it is very doubtful that the manufacturer's pressures are in any way optimal. However, it's probably true that they are not awful either.

Running 45psi on a dry day with appropriate tires might be a very good choice. Running 45psi on a very wet day with tires which are almost worn out would be a horrible decision.


And just as a cautionary note about trusting the manufacturer's recommended pressures, there is some evidence that the Ford Explorer/Firestone fiasco of a few years ago (where Firestone tires were shedding their tread and causing wrecks) was partly due to Ford recommending some questionably low tire pressures.

CDO

iTrader: (2)

In the case we're talking about though, 45 psi doesn't seem to be hacking it.

Ford lowered the tire pressure recommendation to reduce the chance of rollovers. They were going for a lower center of gravity I believe. They ended up trading one risk factor for rollovers for another.

Cabo

[QUOTE=jbrennen]On any particular day, for any particular driver, it is very doubtful that the manufacturer's pressures are in any way optimal. However, it's probably true that they are not awful either.QUOTE]

Agreed. Recommended is usually a good starting point if you're looking for what would qualify as the best for you...


Cabo

TexasRS

[QUOTE=jbrennen]Running 45psi on a dry day with appropriate tires might be a very good choice. Running 45psi on a very wet day with tires which are almost worn out would be a horrible decision.QUOTE]

I don't quite understand how water (on a wet day) is a factor??? Anyone willing to explain? Thanks...

TexasRS

After decreasing my rear tire pressure to 42 (and keeping my front at 45), I indeed noticed an increase in rear stability on the highway! So, decreasing my rear pressure is good advice!! I'm thinking about trying: 42f 39r.....

By the way, is it safe to have a 5psi difference between front and rear tires? For example: 45f and 40r??

Thanks.

jbrennen

iTrader: (1)

In general, in low traction conditions, you want to make the car's contact with the road as "compliant" as possible.

For instance, if you run lower pressures in the wet, the sidewall (and the tread itself) can flex more to absorb things which might otherwise cause the tire to break loose.


Note that you don't want to go too low on the pressures if there is standing water, because lower tire pressure increases the size of the contact patch. Bigger contact patch means more risk of hydroplaning.


I've run snow tires at 40 psi in extremely wet conditions and actually performed really well (click to read about it) but those were full tread tires with big tread blocks and deep siping, plus a soft tire compound.