josesantigo57

iTrader: (4)

Ok, so im heading back home soon and the day after i get home im going to an event. Its set up in a very small short track, dont develop much speed, mostly 2nd and 3rd gear on straight, many tight corners. Ill see if i can find a pic of the layout of the track. I have Falken Azenis 245F and 275R With Tanabe Springs, Tokico shocks, 0 turns from full soft rear, 2 turns from full soft front. Racing on very hot weather (PR) track will be very hot too.

My question is, what would you guys recommend i do to be able to get better entry corner speeds? I was dealing with some understeer when racing earlier this year in another track. Whould i make my front suspension harder and lower my tire pressure? I usually tr to run at 30-32psi when hot both F&R. Im kinda a noob but definately looking to learn and improve my skilz! Thanks !

guitman32

iTrader: (15)

Your tire pressures are already pretty low for track use, so I would only go lower if you think the sidewalls can handle it (I wouldnt go any lower myself - I have the same tires and I run at 37-39psi cold depending on the temp).

Making your suspension siffer in the front will increase understeer. Dont do that. Either soften the fronts or stiffen the rear shocks. Do you have sways? If so, try adjusting them also.

josesantigo57

iTrader: (4)

No i dont have any swaybars yet. For tire preassure ill go to around 39 cold and adjust from there, hmm well i though i need to stiffen broth front and rear, since im near full soft, i must have alot of lean and rool, tightening might help me get some weight off the front of the car @ turn ins, i was thinking going maybe 8-9 turns from full hard on the front and maybe 7-8 turns from full hard on the rear? witha lowe tire pressure in the rear than in the front? ...dunno..damn this is complicated

Q45tech

Until the advent of 51 psi tires, the usual was 80% of max [44 x 0.8=36.2 psi COLD]..........for 51 psi this would be 51 x 0.8= 40.8 psi COLD.

80% of the max usually correlates well with the real static weight on front tires.

guitman32

iTrader: (15)

Listen to him...he is wise! Wiser than most!

julian

if you're understeering transitions then increase the damping in the rear. but if you're understeering during steady state cornering adjusting your damping won't change anything... but it will affect what your car does when you lift throttle to tighten your line.

i dont know how the rest of you guys are running such high tire pressure but whatever works. on the stock tires 37 to 38 psi hot worked for me. i haven't driven azenis before but all the tire tests i've read say both the 215's and 615's are more affected by heat than comparable tires and get greasy at the end of the session.

josesantigo57

iTrader: (4)

Ok, problem is right now im full soft on my settings. So should i stiffen up the front up to maybe 80-90% and leave the rear at 0-20% for more dampening?

julian

no, you should do opposite if you want your rear end to respond faster. you want to increase the damping in the rear RELATIVE to the damping in the front.

i don't know rates of the springs and shocks are on your car but i'll give you an example from my miata. i have koni single adjustables (rebound only). The aftermarket springs I have are 318 lb/in front and 233 lb/in rear. I can't recall the exact stock rates were but they were approx 150 front 110 rear.

if i had my stock springs, i could keep my konis adjusted the same front to rear... like both at full soft because the koni's were designed for the original front/rear spring rate difference. call this baseline1

now that my new springs increase the front rates more than the rear (and everything is stiffer overall), i have a new baseline shock setting. if i had my front and rear konis set to full soft (baseline1), there's not enough damping for the higher spring rates and i can tell my car oscillates over bigger bumps, especially the front end since the spring rate increased so much. so now my baseline2 is 1/2 turn from full soft in the rear, and 1 turn from full soft in the front. baseline2 is what my butt dyno measured as balanced damping front to rear.

now if i want more oversteer in transitions, i would increase the rear damping from 1/2 turn to 3/4 to see how it feels. if not enough then i'd go to 1 turn.

if i wanted more damping overall but still keep the front/rear balance, i would go 1.5 turns in the front, 1 turn in the rear.

hope that helps.

josesantigo57

iTrader: (4)

Hmm ok im kinda getting a feel for this. However wont having such a low setting hurt me by letting to much weight move to the front of the car while braking and turn in causing some understeer? Because i thought this was causing the understeer but now im quite confused

guitman32

iTrader: (15)

josesantigo57, I would recommend some reading to better understand car dynamics and the effects of suspension settings on car balance. Here are some links I found in a quick and dirty search on google. I havent actually read any of these thoroughly as I am at work, but they look to be at least a good start.


http://en.wikipedia.org/wiki/Car_handling
http://rogerkrausracing.com/overundr.html
http://www.bbc.co.uk/dna/h2g2/A1075547
http://www.nsxprime.com/FAQ/Track/highperfdriving.htm
http://en.wikipedia.org/wiki/Oversteer
http://en.wikipedia.org/wiki/Understeer

I know what youre saying and I agree...on autoX in the morning (ie cold morning, no sun) I inflate to 40psi cold. When the tires heat up as I run more I bleed pressure to even out at anywhere from 39-43 psi hot to suit the conditions (the Azenis liked 40 rear and 42 front hot psi in the afternoon this weekend). I didnt notice any greasy-ness on the Azenis yet, but I have read the same reports. I have yet to subject these tires to sustained track conditions so I cant comment.

Q45tech

Shocks just alter the time of the spring compression/rebound.........the transfer weight is the transfer weight only CG and track width and wheel base affect this materially.

josesantigo57

iTrader: (4)

Right...i think ill jsut go 50% F&R and adjust from there, probably soften the front if i still feel the same understeer, ill let you guys know.

Gsedan35

iTrader: (10)

Learn from the autocross guys, this platform is camber defecient and yields benefits from increases in front roll stiffness. The same textbooks that tell you front roll stiffness increases means your adding understeer also tell you to test your resluts and be willing to make changes until you succeed. Their are those of us that have come before you, you can learn or continue on a path of deminishing returns. Your choice in springs is not helping you at all, nor is the lack of aftermarket sway bars.

MoodDude

There is a majical device that will tell you exactly what tire pressures to run to achieve maximum grip on your car, with you driving - it is call a pyrometer. Buy one - learn to use it - and use it. You will then find out your ideal tire pressures to achieve your maximum grip for that coarse.

As far a your dampening settings - again you need to test and tune for that coarse. My rule of thumb is to start out stiffer in front than rear, so my wieght transfer will be quick to the front and the wieght transfer will be slower to the rear - this helps me brake hard for a corner - and I am able to roll on the gas sooner in the corner.

Gsedan35

iTrader: (10)

1+

Q45tech

Consider that ~~40 psi of inflation creates a tire stiffness of 1200-1600 [depending on size/brand etc] pounds per inch of springiness in a tire [measure the deflection of the unloaded to loaded tire [when you unjack and lower the body on it] to gain an exact number [create a graph of stiffness vs DIFFERENT PSI] for each of your tires.....................the same tire may vary 2-4% depending on the way it was assembled [the way the ply splices align] that day.

You have the road stiffness, in series with tire stiffness, all of which are in series with coil spring stiffness............these decrease the effective stiffness of the published coil rate [by ~~ 10%].

MoodDude

What the heck are you talking about Q45tech. You tune your tires to maximize your contact patch, and then tune your spring/dampening to match that pressure and coarse. You don't tune your pressure to gain more spring stiffness!!
The guy wanted to know how to gain more corner entry speed. That means he needs to gain higher grip on the front outside tire. This means he needs to maximize his contact patch with this tire and the road, and the first way you do that is by ensuring that you run the correct HOT pressure and you have the right alignment. And since I have never run his tires, I have no idea what it is for it, but I know for Toyo RA1's it is 36 to 38 psi (get it 1 psi over and under and you are talking 2 to 5% higher lap times), and Pilot Sport Cups it is 37 to 39psi.
Now for your stiffness of your suspension - it depends on the driver and the road coarse. For instance you can gain seconds a lap with 900# springs at Roabling, but take those same springs to Sebring and you will be in the wall! Also, if you take an unexperience driver and put 900# springs on - and they will complain all day about the understeer or overstear (depending on the wieght distribution of the car, sways, alignment), yet put an experience driver with the same springs and they fly around track.
What I am trying to say is there is no correct answer. The best advise is test and tune and have fun with it.