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302S setup inquiry

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I've gotten enough laps on my 302S to get interested in setup. And since it's out of commission for a few weeks while we put on a Bosch M4 (aka brakes-i-can-trust) this seems an opportune time to pick folks' brains...

Stock, my '13 302S on 305 pirellis slicks was stable but pushed like a tractor at Laguna. I swapped the rear sway bar, which was a solid 13mm bar measuring 18 in/lbs, for a solid 18mm bar at 55 in/lbs. I ran the car at Sonoma with this config, and it worked well in high speed corners but tended to oversteer trail braking into slow corners, and really did not want to put power down exiting T2, T7 etc. So I'm contemplating what to try next, and was curious if either folks have already been down this road, have suggestions that have worked well at other tracks, etc? Or, if there is a good FAQ on this car's setup, just point me at it?

Thanks in advance,
Ben
 
Which 305 tire are you using? 645, 660, or 680? Use the 680's. Laguna sucks for grip, its slippery and almost no matter what you feel like you should be faster but can't do it. I honestly don't know what rates came on the 302S, I'm thinking 500lbF/300lbR but not sure. I would say drop the front spring rate, but my advice is limited to our shock/front swaybar package, as you can/will run into problems with bottoming out the car or shocks at both tracks.
 

Grant 302

basic and well known psychic
It sounds like steady-state turning is 'fixed' with the 18mm bar, so I'd look more to damping to fix the trail braking and corner exit with damper adjustments. Generally increase in the front and/or decrease in the rear, compression and rebound for both. I'd probably try the corner exit adjustments first.302S adjustments for treynor.jpeg If correcting this way causes issues with steady state or high speed turns getting loose, then go back the the 13mm rear bar and soften the front and increase the rear from where you are now.

Or find somebody to make you the equivalent of a 15 or 16mm solid rear bar! ;)
 
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Which 305 tire are you using? 645, 660, or 680? Use the 680's. Laguna sucks for grip, its slippery and almost no matter what you feel like you should be faster but can't do it. I honestly don't know what rates came on the 302S, I'm thinking 500lbF/300lbR but not sure. I would say drop the front spring rate, but my advice is limited to our shock/front swaybar package, as you can/will run into problems with bottoming out the car or shocks at both tracks.

I have been running the 660 front and 680 rear tires. And oddly I can't find the specs for the stock springs either; I'll probably need to look at the car.

It sounds like steady-state turning is 'fixed' with the 18mm bar, so I'd look more to damping to fix the trail braking and corner exit with damper adjustments. [...]

Thank you. I've been driving for several years now but I'm completely new to suspension tuning, so this is quite helpful.
 

Grant 302

basic and well known psychic
Thank you. I've been driving for several years now but I'm completely new to suspension tuning, so this is quite helpful.

Glad to help! Wouldn't know that from how fast you drive in your videos! Did you have your car setup like in the pdf info below? What are your front alignment and height settings?

https://performanceparts.ford.com/download/boss302spdfs/2014/Boss 302S owners manual version AV3.pdf

View attachment 2884

Adjusting alignment (in this order):
  • Set caster. Recommended setting is typically 7° - 7.5°, but equal on both sides
  • Set camber on both sides to -3.0°
    Set toe to 0 degrees or 1/8" total toe out on 30" toe plates
I you go back to the 13mm rear bar, there could be a little more 'help' with front grip if you carefully go over all your settings and take track specific profile temps and pay very close attention to tire pressures. There's some current discussion in fabman's build thread and tire pressure 'mapping' from @blacksheep-1 here.

I have been running the 660 front and 680 rear tires. And oddly I can't find the specs for the stock springs either; I'll probably need to look at the car.
I've heard 600F/350R more recently, but I *thought* it might be 600F/400R before that for some reason. Maybe the Vorshlag guys know? @Fair @modernbeat One or more of their customers have 302Ss.

DSC_5509-M.jpg
 
I have been running the 660 front and 680 rear tires. And oddly I can't find the specs for the stock springs either; I'll probably need to look at the car.



Thank you. I've been driving for several years now but I'm completely new to suspension tuning, so this is quite helpful.

The 660 is probably most of the problem. That tire was garbage in 2015 on the Mustang in PWC. Run the 680 square. Also, you need to be running as much camber as you can get with the Pirelli.
 
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Interesting, thank you all. I'm going to try both the 680/680 combo, and tweaking the roll bar and suspension settings. It's going to be a couple months (Sakata motorsports has a backlog for the Bosch M4 wiring looms) but I should have track reports by early next year.
 
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I recommend guys stay with one mfg for their suspension stuff, if you mix Vorshlag with Ford Performance, as an example, then call one or the other for advice...what are they going to say?
Pick a road and stay on it.
You're talking to AJ the official driver of the Mustang Mafia, a more experienced person, who actually builds, drives and tunes their car is hard to find
 

Grant 302

basic and well known psychic
I mentioned them because I know they've seen/worked on customer 302S cars and probably since they were stock or as delivered *by* Ford so they probably know the stock spring rates in question.
 

Grant 302

basic and well known psychic
The first chart is for the OEM-style perch springs. The P spring chart has been floating around the 'net for a while, but the 'average' rates highlighted in yellow are irrelevant. The data shows working ranges of 230-260+ F and 202+ R. The tender side of the rear coil is just to keep it in the spring pocket at full droop.

Edit: In other words, ignore the highlighted 195F/148R 'avg rate' values.
 
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OK, let me bring some data to the table. My car is a 2013 Boss 302S with the factory option 3-way Dynamic suspension (base is a Sachs). The spring rates are 600# front / 350# rear. Suspension components are:

Shocks: Dynamic 3-way
Front Springs: Eibach 0900.250.0600
Rear Springs: Eibach 0800.225.0350
 
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trenor, on the Sachs Damper set, I believe the front springs are 8" and the rears are 9".
Not as listed above.
Could be different on your Multimatic set, but I believe they are the same.
 
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trenor, on the Sachs Damper set, I believe the front springs are 8" and the rears are 9".
Not as listed above.
Could be different on your Multimatic set, but I believe they are the same.

Just to be clear, what I've listed above is what my shop reports is actually installed on my car. I do not know if the Sachs spring lengths are different (which I agree seems odd) or if the shop transposed a digit. I can check next time I see the car.
 
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If you have the red Eibach springs, the part numbers (description) will be painted right on the spring.
 

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