Recently the colorado region has aquired use of a parking lot near DIA which is concrete. Before this lot the only parking lots available to us were asphalt. So I'm use to adjusting tire pressure for asphalt. The new parking lot at DIA like I said is concrete and its extremely abrasive/coarse so one might thing grip wouldn't be a problem. But after two events there I'm finding that I have massive understeer where as on asphalt and even the Topeka Pro auto-x pad the car didn't have as much understeer. I'm running relitively the same tire pressures as I would on asphalt and I'm in STS using azenis.

So generally what's the thought for concrete tire pressure. And abrasive concrete. Any thoughts for some reason I think I need to go with less tire pressure up front to correct the understeer.

 

what pressures are you using? the general rule for azenis is to lower rear tire pressure to allow the rear to rotate more.

jeff

 

Usually, when you run on concrete, you need to increased tire pressure vs when you run on asphalt. We would increase the Azenis 2-4 psi on average.

As for why your car is pushing, we would probably need some more info on the car and what the wear on the tires is looking like and best would be to take temp readings of the tires after you run.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jeff R &raquo;</TD></TR><TR><TD CLASS="quote"> the general rule for azenis is to lower rear tire pressure to allow the rear to rotate more.
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wouldn't you want to raise your rear tire pressure for more rotation?

 

Anything off of the optimal tire pressure should result in less grip but I always prefer to go up in tire pressure rather then down.

I find there is a lot of grip differences in concrete sites but generally speaking I'll run stiffer shock settings in the rear to counteract the increase in understeer.

What I do is to get the car set for crazy loose on asphalt, then when on concrete the car doesn't push.



Modified by Geratol at 12:45 PM 4/21/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by illusion &raquo;</TD></TR><TR><TD CLASS="quote">

wouldn't you want to raise your rear tire pressure for more rotation?</TD></TR></TABLE>

As far as Azenis go, absolutely not. LOWER rear tire pressure for more rotation. People who say to run them higher have never experimented with tire pressures using Azenis.

 

Ok well. I have an STS 98 Prelude. Springs 450 front and 425 in the rear. Stock bar up front and Progress adj bar in the rear. I did full stiff for shock and bar in the rear and full soft up front. tire pressures were 37 up front and 40-41 in the rear and the end of the 3rd run. This is the relitive set-up I'd do for asphalt. And I actually did my first run of the heat with 40 psi front and 42 psi in the rear and that was horrible. I decreased the pressure in the front for the remainder of the runs and the car felt a bit better, i.e. understeer was reduced. Some other some what relevent info might be I got 1st out 48 in STS.

 

I experience the same thing when going from asphault to concrete. My logic is because the rear tires have more grip on the concrete they don't let the car rotate as much. I run just a few lb lower in the rear on asphault where on concrete my tire pressures are about 35/25 to get rotation I need.

And I've always liked lower pressures much more than higher pressures. Just works better for me.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ryan12321 &raquo;</TD></TR><TR><TD CLASS="quote"> My logic is because the rear tires have more grip on the concrete they don't let the car rotate as much. </TD></TR></TABLE>
That's pretty much what I've concluded. And perhaps I'm running a bit high up front.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Todd00 &raquo;</TD></TR><TR><TD CLASS="quote">As far as Azenis go, absolutely not. LOWER rear tire pressure for more rotation. People who say to run them higher have never experimented with tire pressures using Azenis.</TD></TR></TABLE>

*enter exception to the rule* i've gone both ways with rear tire pressures. both high/low accomplish the same thing mid corner, but there is a drastic change in corner entry feel. a low rear tire pressure will make the car looser in transitions or corner entry, while high rear tire pressures would do the opposite.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mark Ortiz &raquo;</TD></TR><TR><TD CLASS="quote">Up to the point of rear wheel lift, rear load transfer builds faster than front load transfer. Beyond that point, rear load transfer is 100%, and front load transfer builds rapidly. So does roll angle. So does understeer.</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mark Ortiz &raquo;</TD></TR><TR><TD CLASS="quote">As a general rule, to get a car that has good consistency as grip varies, we want the inside rear wheel to lift just a little in steady-state cornering, when grip is good. If it lifts more than that, we are likely to have a relatively loose car when grip is poor and a much tighter car when grip is good.</TD></TR></TABLE>

nate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">*enter exception to the rule* i've gone both ways with rear tire pressures. both high/low accomplish the same thing mid corner, but there is a drastic change in corner entry feel. a low rear tire pressure will make the car looser in transitions or corner entry, while high rear tire pressures would do the opposite.

nate</TD></TR></TABLE>

Thats a good point nate. I've never thought about it but that make sense about the corner entry and transitions. Thats mostly where I want my car to be very loose. Get it rotated before the turn(turn-in) and then full on the gas before you even reach the apex. Thats just how I drive. Not sure if that style would work for everyone.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">

*enter exception to the rule* i've gone both ways with rear tire pressures. both high/low accomplish the same thing mid corner, but there is a drastic change in corner entry feel. a low rear tire pressure will make the car looser in transitions or corner entry, while high rear tire pressures would do the opposite.

nate</TD></TR></TABLE>

Well, I'm not sure that I agree with you in terms of the Azenis, and I've went both ways. It seems that you must run north of 50lbs of pressure to get any kind of rotation back there, and then you get snap oversteer and the rear end of the car tends to bounce a lot more over rough surfaces (especially in the corners). Something that does not happen with lower pressures as I think rotation is a lot more gradual (and controllable) that way.

And I've done this to several different STS/X cars with varying suspension and springrates, and I will pick lower pressures any day of the week in any situation over higher pressures in the rear.