Help me get back on track

[Speedboosted]

2006 Mustang 3v

Setup last fall:
- Bilstein dampers with H&R Race Springs and J&M Camber Plates
- Whiteline Watts
- BMR spherical LCAs
- Whiteline rear bar full soft
- BMR 35mm front bar full stiff
- 3.73 gears with a Boss Torsen diff
- 4 piston brembo up front and Carbotech XP12 pads
- factory rear brakes with Porterfield R4 pads
- 18x10 wheels with 275 Conti slicks

This setup was very simple, yet very effective. The car had immediate turn in, neutral balance, and could induce rotation/oversteer via the throttle on corner exit if desired.

Over the winter, my car underwent quite a few changes. Things of note:
- MCS TT1 Coil overs and Vorshlag Camber Plates with 550/250 springs replaced the Bilstein setup
- 305 Conti slicks on the same 18x10 wheels
- Removed rear sway bar
- Lowered RC pivot on watts from top hole to bottom hole

First track day out with those parts was a huge mess. Understeer everywhere, rear brakes were locking up under braking, zero turn in response or feel. I played with damper settings a little bit that day, but the car was so bad that I knew a lot of things were going to change so I didn't spend too much time at the track adjusting. Arrived with +8 rebound in the front, and +4 in the back. Finished the day on +9/+8 and there was a hair less understeer. Despite all of this, I improved my PB by 1.5 seconds so I was generally happy all things considered.

Next scheduled track day was a month out, so I knew I had to get busy with the adjustments I thought it needed. First take was to reinstall the Whiteline rear sway bar on the softest setting. Next I replaced the rear calipers, rotors, and pads (oem pads in case my issue was too agressive of a pad, even though it had worked fine last fall). I also backed the rear rebound down to +6.

This resulted in a much more balanced car with no braking issues. I still had hardly any turn in response, but I chalked it up to the 305 tire being a little bulged on the 10" wheel. Still lots of understeer, but I could rotate with the throttle now (before it would just push more). Overall happy with the direction I was heading in, however I destroyed two tires that day from what I thought to be a lack of camber. I later realized it was likely from all the understeering/push happening in a couple of the long sweeping corners and just ripping the tread off. Track Addict didn't work at all, but based on me pacing one of my friends during a session and seeing his times, I suspect I was able to improve my PB by roughly 2 seconds. Not what I wanted, but I will take it.

Last weekend I went back to my home track in hopes of establishing some consistency with the car. Having killed off my slicks, and not wanting to destroy another set of slicks in just one day, I chose to run on some very heat cycled 275/35-18 BFG Rivals. I used to track drive on these a few years ago and remember the postive feedback they gave so I thought it would be a good baseline to work from. Chasing down a shimmy from the front, I repalced the control arms with OEM GT500 units as well as the inner and outer tie rods from Moog. Did the alignment myself and set camber to max that the plates allow, and 1/4" toe out. I also wanted to try and alleviate more understeer, thus softening the front bar to the middle setting. Last change was setting rebound to +13 front/+9 rear.

How did it go? Well, ok. Tires visually looked good, but have nowhere near the grip they once had or what I'm used to. Going into the first turn on the warmup lap, I knew it was no good. Turned the wheel, aaaand then the car turned. Zero response and grip, great. With the front bar softer, the car loaded up better than before and actually handled better mid corner then I expected. This time I had lots of understeer on entry, and slowing down didn't do a whole lot to improve it. I also dropped the front rebound down to +9 and there was slightly less understeer. Brakes felt ok, but was getting some lockup on the front which I halfway expected now that most of the bias is up there and the tires don't have as much grip. Took tire temps after each session (laser gun, not a real pyro) and the spread across the tread was very even with the insides being a few degrees warmer. Overall temps of the rear tires were about 25-30* higher than the fronts, may have had too much pressure in them. Dropped them down throughout the day and the gap front to back closed, but the rears were still about 20* more. Tire wear was perfection, which made me happy. PIR is known for being hard on tires, but I saw no problems. Overall, was again fairly pleased with the progress, but the car hsa even worse turn in while not killing the tires, and I was 4 seconds slower per lap compared to last fall (chalking that up to tires and brakes). There is no rear brake lockup, but I have noticed a reduction in overall braking from running the stock pads out back.

So with all this in mind, what is my next step? Here are my initial thoughts, but of course I would love to hear some feedback from you guys.
- Move RC pivot back to the upper hole
- 200 lb rear springs
- Mount another set of 305 slicks on my new APEX 18x11" wheels
- Lower the ride height to gain more camber (will need to open up the strut tower)
- Possibly corner balance

I was expecting more from the coilovers and big slicks to be honest. The old setup was so easy to drive and did what I wanted, but now it's a constant battle. I'm hoping that raising the RC back up will encourage quicker transitions, thus more immediate turn in.

What do you guys think? Any tips or things I'm missing/overlooking?

 

[gripdriver]

I'm not very experienced, but I would guess you made to many changes at once.

Maybe try throwing the rear bar back on, and returning the watts to how it was. Then the only change you have to deal with is tires, and coilovers.

Get the coilovers setup with the new tires, then play with the sway bar, or watts one at a time.

 

[Grant 302]

It sounds like all the recent changes to your car shifted the bias to understeer at the spring and sway bar level. If you're going to go back to 305s, I suggest starting with going stiffer in the back using the bar. If you're sticking with the 275s, then I think it makes more sense to soften the front a bit at the bar.

If the understeer problems persist at turn in, I'd consider changes at the spring level, but I'd only go stiffer in the back since you're running slicks.

I could be wrong and maybe you just need to adjust damping to the same effect. Like if you can still decrease the front rebound without getting under-dampened.

 

[Mad Hatter]

I tried the 305 Conti slicks before on 18x10 drifts and its was not a great combo.... I think that combined with no rear bar could give you too much understeer... to give you and idea, I had faster times with 295 semi slicks then with 305 Contis on the same wheels. But going to the Apex 18x11 wheels should help!!

Camber plates or Bolts would be a better way to get more camber!! Lowering your car too much could affect your front and rear roll center. Found that -3.3 front camber was very nice! tires temps were even with even wear.

On faster tracks I like the no rear bar setup. But if you have some tight slow corners the understeer can be quite sever.... Found that a 18mm bar took care of that. Now experimenting with different rear bars with no final results yet.... (apart from breaking them )

 

[modernbeat]

The slicks you are running are a numb tire. And if they are takeoffs, worse.

The FIRST rule of setup is to have good, fresh tires. If you plan to only ever run these tires, then go ahead and setup around them, but expect that they will need a LOT of heat, and that they don't give good feedback.

For setup using shock tuning (and a lot of other setup help) I can highly recommend Neil Robert's book Think Fast.
https://www.amazon.com/Think-Fast-Racers-Why-Winning/dp/1451558759

 

[racer47]

All of your initial changes were towards understeer.

550 lb front springs are almost twice the rate of the H&R springs = understeer

250 lb rears are actually less than H&R = understeer

The numbers I have on H&R race springs are #51655-88 1.5" front drop, 1.4" rear, variable rate, working rate is front ~300 lb, rear: ~275 lb

That BMR front bar on full stiff is too much with 550 lb front springs = understeer

Removed rear sway bar = understeer

Lowered pivot on watts from top hole to bottom hole = understeer

I would recommend the middle or soft setting on the front bar. Keep the rear bar at the middle or soft setting. And put both the front and rear bar at the same setting (soft or middle). 1/4" toe out is too much. Zero is good or 1/8" out is plenty. Put the watts in the std position if there is one. If there are only 2 positions, put it back on top. The rear roll center needs to be higher than the front.

The coilovers are not the issue. I'd reset those to whatever Vorshlag says is the baseline to start from. Don't try to fix spring and swaybar imbalances with shocks. Leave the shocks alone for a while until you get a good base balance.

The biggest difference is the high front spring rate. But that is what the car needs. You just need to sort out the overall balance and the car will be much faster. That big stiff front swaybar was making up for too little spring rate. Now that you have the right springs you don't need that much bar.

Edit: I originally listed the lowering of the watts link as oversteer. That was wrong. Lowering the roll center means a greater distance from the roll center to the rear c.g. which means less rear roll resistance which is more towards understeer.

So basically every change was towards understeer.

 

[VoodooBoss]

All of your initial changes were towards understeer.

550 lb front springs are almost twice the rate of the H&R springs = understeer

250 lb rears are actually less than H&R = understeer

The numbers I have on H&R race springs are #51655-88 1.5" front drop, 1.4" rear, variable rate, working rate is front ~300 lb, rear: ~275 lb

That BMR front bar on full stiff is too much with 550 lb front springs = understeer

Removed rear sway bar = understeer

Lowered pivot on watts from top hole to bottom hole = understeer

I would recommend the middle or soft setting on the front bar. Keep the rear bar at the middle or soft setting. And put both the front and rear bar at the same setting (soft or middle). 1/4" toe out is too much. Zero is good or 1/8" out is plenty. Put the watts in the std position if there is one. If there are only 2 positions, put it back on top. The rear roll center needs to be higher than the front.

The coilovers are not the issue. I'd reset those to whatever Vorshlag says is the baseline to start from. Don't try to fix spring and swaybar imbalances with shocks. Leave the shocks alone for a while until you get a good base balance.

The biggest difference is the high front spring rate. But that is what the car needs. You just need to sort out the overall balance and the car will be much faster. That big stiff front swaybar was making up for too little spring rate. Now that you have the right springs you don't need that much bar.

Edit: I originally listed the lowering of the watts link as oversteer. That was wrong. Lowering the roll center means a greater distance from the roll center to the rear c.g. which means less rear roll resistance which is more towards understeer.

So basically every change was towards understeer.

Nailed it! Nice post.

 

[Speedboosted]

Thank you for the replies everyone, I really appriciate the feedback!

@modernbeat what would you recommend for baseline damper settings?
@racer47 that was very insightful and helped me see how much I screwed up. Lol definitely going to move the watts back up (only 2 positions). Should I try 200lb rear springs and move the rear bar to 2 positions stiffer, or stay at 250 and go 1 stiffer? Corner exit traction isn't great, but it's not horrible.

Another question I have is relating to roll steer via LCA relocation brackets. Mine are in the middle hole right now and point slightly down towards the axle. What affect would moving them up or down have?

 

[ArizonaBOSS]

With respect to relocation brackets--compared to your current "middle" position:
Moving the LCAs down in the brackets will increase roll steer and traction, up will decrease it.
I usually use the position you describe and typically only use the lower hole on very short, tight tracks (rarely).

 

[racer47]

200 lb springs are too soft when combined with 550 lb fronts. Vorshlag knows what they are doing, 550/250 is a good combination. Work with this a while before changing spring rates.

I'd run both the front and rear bars at full soft. If there is still understeer, go one step stiffer with the rear bar.

Don't mess with the lower control arms right now. Keep them in the middle like the #41 says.

While I admire your willingness to try things, I think you need to slow down and evaluate what you are changing and why.

I wasn't going to mention tires but since Jason did, I'll chime in too. You really should buy good tires. I know tires are expensive but they are worth it. After spending $5000+ on coilovers and wheels, it doesn't make sense to run old Contis. If going faster is the goal, and money is limited, you need to prioritize tires much higher on your list of stuff to buy. I bet a new set of 295/30-18 A7s or R7's, mounted on your old 18x10s would have been faster than old Contis, new coilovers, new springs and new wheels.