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Suspension settings for autocross

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I am looking for some help with shock settings and tire pressures for my 2013 Boss. I am still fairly new to autocrossing and have been running the same Rivals for the past 2 years. I was trying to make them last for as long as I could just to eliminate a variable while I learned. At the event last month 2 of them started showing cord so I replaced them with RT 660’s and ran my first event on them today. I was expecting to immediately pick up time and found myself frustrated all day long. I felt like I was fighting the car. I know one element I was simply over driver it as it looked like a fast section but there was very little grip in that section of the parking lot and I failed to adjust for it. The rest of the course I felt like I would have been faster on the Rivals, but they are familiar to me.

I am currently running pedders coilovers, 450lb front springs and 275 rear. They are 30 way adjustable and currently I am 15 on fronts and 7 from full soft on rear. I have white line sway bars which have 4 adjustment holes, I am 3rd hole from full stiff on front and softest setting on rear. I have all BMR spherical control arms in the back, middle hole on relocation bracket. Car was set for autocross by a local shop who took care of proper antisquat settings in the rear and -3 degrees camber in the front with .060 of toe out. Car has no aero on it.

I normally finish 2nd or 3rd over all at my local autocrosses and today found myself mid pack. I am thinking of putting stock upper control arm back on as some have suggested on these forums. Wondering if I should be much stiffer on shock settings with spring rates I have. I started out at 34psi front and 32 rear. I slowly came down to 31psi front and 30 rear. Tire wear was right at the triangles on the tread but no where near going over on the side wall. I thought these tires liked higher pressures but seemed like I could go lower if needed. Sorry for the long post, but any help would be greatly appreciated.
 

Mad Hatter

Gotta go Faster
5,293
4,293
Santiago, Chile
Those are the same Rivals you have been running for two years :eek:??? I thinks that would definitely put you down a few places. How does the car feel on the autocross tracks? What would you like to improve?? Mixing tires is really never a great idea but, did you notice which end of the car improved with the new RT660;s?
 

Dave_W

Cones - not just for ice cream
1,016
1,326
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
DId the balance of the car feel different - more understeer or oversteer than with the Rivals? The Falkens should have more grip, but were you expecting too much and overdriving them? Were the drivers the usual group, or were there some better drivers that showed up at this event? Just trying to get more clues to the mystery.
 
After sleeping on it and reviewing the one run that actually recorded I think you are correct and I was over driving them. Still curious as to wether I am leaving any time on the table with my suspension settings. I kind of just took a guess at where I thought they should be when I first started and have basically left them alone while I learned. In hind sight, I should have slept on it before I made this post, I was just super frustrated. Drivers were the normal ones that are at all the events.
 
Do you have videos of the runs we can see? Your overall setup is in the ballpark and a RT660 is a much faster tire compared to an old BFG....but you cannot drive the two tires the same. You can pretty much beat a BFG as hard as you want and it says "that's all you got?! Give me more". Falkens are not as heat sensitive at Yok's, but you can't slide them around like you could a BFG.

What was the outside temp? You can't overheat a Rival but you certainly can overheat a Falken.\

Finally, were the Falkens stickers? They do get better with a heat cycle and with less tread.

DaveW
 
The tire psi was taken before and after each run. I logged the psi before each run and then after. The biggest change in pressure was about 3 psi on the first run. The 31 front and 30 rear set before my final run. I was so frustrated after the run I drove straight back to paddock and never took the final reading.

Ambient temperature was around 80 and it was overcast on my runs. Tires were brand new, I had them heat cycled by tire rack before delivery, but they had not ever been on the ground before this event. I don't have a pyrometer, but I think I will go ahead and get one before my next event. I honestly had not really considered needing to drive them differently, seems maybe the rivals were much more Newby friendly? Currently I am in the middle of buying a new house, and selling my old one, but once that is over I thi k first priority is going to be finding a school to attend. I did 4 driving schools my first year and two last year.

I really do appreciate all the input. Thank you all very much.
 
This is not a tire pressure issue. A pyrometer is useless on a regular Autocross course, you can’t get back to grid and get readings quickly enough to be useful. You need a skid pad (or road course) for it to be an effective tool

your setup is within the ballpark of most people on both car and tires. A few psi one way or the other is rarely able to be felt by most of us until you break out of the 10psi “it’s ok” window and they go away completely. You are dead in the middle of that window and no where near breaking out

too hot for a falken is warm to uncomfortable to put your hand on after a run. If it’s uncomfortable then you should have been spraying a few runs back. They aren’t like a yok or Bridgestone that works ice cold.

glad to give constructive tips if you post a video.

otherwise, keep working on the loose but behind the wheel :)
DaveW
 
Thanks Dave, I will skip the pyrometer and go buy a water sprayer instead. They were definately warm to the touch approaching uncomfortable. The way they felt to the touch was how my Rivals did when they worked the best, which I am going to assume is to hot. And its only going to get warmer from here on out. My wife got a giggle out of the "loose but behind the wheel". I said you misspelled nut, she said you forgot a t lol.
 
6,473
8,403
Pyrometer is not really applicable to autocrosses, unless, possibly, it is an exremely long course. PSI at the end of the run is still in play however, as long as you have someone take them at the end of the run (in some safe area) driving back to the paddock area.. it's just too long of a period of time. It's like trying to do pressures (or temps) after yellow flag laps, it will not yield productive results.
 
Pyrometer is not really applicable to autocrosses, unless, possibly, it is an exremely long course. PSI at the end of the run is still in play however, as long as you have someone take them at the end of the run (in some safe area) driving back to the paddock area.. it's just too long of a period of time. It's like trying to do pressures (or temps) after yellow flag laps, it will not yield productive results.
For autocross, consistency in when you take pressures is the key. Our versions of "cold" and especially "hot" pressures are soooooooooooo different than road race tires, it's just not that relevant. IN fact, I try to not discuss hot and cold regarding autocross pressures, I think it muddies the waters.

I have a pressure I run, I set it before the first run and then bleed it back down to that number immediately after each run. The exact time you do it doesn't really matter IMO as long as it is the same - remember the important thing is that the car does what you want when the tires are at a given pressure *set at the time you set it* and not some absolute number. And you want that setup to be repeatable.

For what it's worth (I usually have a co driver), we find that the tires only build pressure for the first few runs then stabilize for the rest of the heat. This seems to hold at local events where we are at 5 minutes between runs or nationals where it is 15.

Also remember that 200TW tires are not nearly as pressure sensitive as R-comps or especially the non DOT slicks. On the latter 2, 1-2 psi can be a big change in handling. On 200tw, unless you go above or below the happy zone (which is likely 8-10 psi wide) there really isn't a change in behavior.

DaveW
 
For autocross, consistency in when you take pressures is the key. Our versions of "cold" and especially "hot" pressures are soooooooooooo different than road race tires, it's just not that relevant. IN fact, I try to not discuss hot and cold regarding autocross pressures, I think it muddies the waters.

I have a pressure I run, I set it before the first run and then bleed it back down to that number immediately after each run. The exact time you do it doesn't really matter IMO as long as it is the same - remember the important thing is that the car does what you want when the tires are at a given pressure *set at the time you set it* and not some absolute number. And you want that setup to be repeatable.

For what it's worth (I usually have a co driver), we find that the tires only build pressure for the first few runs then stabilize for the rest of the heat. This seems to hold at local events where we are at 5 minutes between runs or nationals where it is 15.

Also remember that 200TW tires are not nearly as pressure sensitive as R-comps or especially the non DOT slicks. On the latter 2, 1-2 psi can be a big change in handling. On 200tw, unless you go above or below the happy zone (which is likely 8-10 psi wide) there really isn't a change in behavior.

DaveW

This is exactly how I run my pressures. Set them at 28 before my first run and then by about run 3 the fronts need bled about 2psi and then by runs 4 and 5 i have to bleed 2psi or so from front and rear, and then by run 6 the temps are usually settled and I don't really need to bleed much more out.
 
6,473
8,403
For autocross, consistency in when you take pressures is the key. Our versions of "cold" and especially "hot" pressures are soooooooooooo different than road race tires, it's just not that relevant. IN fact, I try to not discuss hot and cold regarding autocross pressures, I think it muddies the waters.

I have a pressure I run, I set it before the first run and then bleed it back down to that number immediately after each run. The exact time you do it doesn't really matter IMO as long as it is the same - remember the important thing is that the car does what you want when the tires are at a given pressure *set at the time you set it* and not some absolute number. And you want that setup to be repeatable.

For what it's worth (I usually have a co driver), we find that the tires only build pressure for the first few runs then stabilize for the rest of the heat. This seems to hold at local events where we are at 5 minutes between runs or nationals where it is 15.

Also remember that 200TW tires are not nearly as pressure sensitive as R-comps or especially the non DOT slicks. On the latter 2, 1-2 psi can be a big change in handling. On 200tw, unless you go above or below the happy zone (which is likely 8-10 psi wide) there really isn't a change in behavior.

DaveW
that is remarkably close to how it is done in road racing, only we have 6 or 7 lap intervals, where the tire settles in and gross pressure changes are no longer needed..
 
Our setups seem pretty similar. I also have the Pedders coil-overs with camber adjusting top plate, Whiteline sway bars, and BMR rear control arms with brackets. I'm also running poly bushings in my front control arms, X11 ball joint, and 315/30R19 Falken RT660 tires on 19x11 wheels. My alignment settings are close too, but I think that I have a little more toe-out.

Front Sway Bar: 4/4
Rear Sway Bar: 1/4
Front Shocks: 22/30
Rear Shocks: 18/30
Front Tire Pressure: 37 psi
Rear Tire Pressure: 37 psi
Camber: -3.00°
Toe: -0.14° per wheel, 1/8" total toe out

My car seems to like higher tire pressures, but that is probably because the 315s would work better on 12" wide wheels. My wear marks go below the triangle and I lose grip when I got to a lower pressure. I plan on going with 305s next time I order tires for that reason.

Comparing performance for autocross is hard because every region has different levels of competition and every course is different. That being said, I am typically towards the top of CAM for the regional events I run. I was competing against some fast C5 Z06s and C6 Z06s last weekend and we were all within tenths of seconds of each other in raw time. I feel like my car is pretty well dialed-in and that it's time to focus on the driver.

One thing that I've noticed this year is that turning the shocks down sometimes helps. I run consistently with 2 different regions. One is at a circle track with a paved infield and a lot of grip and the other is typically at a large parking lot with a lot of different surface conditions. That parking lot is part concrete, part old asphalt, and part new asphalt. I softened my shocks to 10/30 front and 6/30 rear at that last event and it was much more predictable on the transitions between surfaces.

It sounds like you have a pretty good setup on your car as-is. You are human, so it may have just been a bad day for you and a better day than others; I have had a few of those.
 
Lots of good advice in here already...I'll offer a couple more nuggets that may or may not help.

I came to the Falken RT660's from the RE71R's. I found that I liked pressures ~1-3 psi higher than the RE71's...and they never touch the triangles for me UNLESS I am over-driving the front end. (295/35-19's on 19x10.5, typical pressures 32-34 psi front, and 1 psi lower in the rear)

The RT660's also turn in faster than the RE71's, which I think turn in faster than the Rivals...due to the stiffer sidewall. As a result, you may need to slow your steering inputs both to prevent overloading (overdriving) the front contact patches, and also to avoid smashing apex cones (which I did a lot in my first season on them).

Finally, I use an IR temp gun to be data-based on when to spray. My goal was to come off course with tire treadface temps no higher than the mid 130's. If I was coming off course in the mid-120's, I started spraying...
 

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