S550 mavisky's "LOUDCAR" Build Thread Profile - S550 Mustangs

[mavisky]

I would suggest trying to add more rear bar before softening the front. You need all of the front roll stiffness possible to help the soft front springs. With aero now you could add more rear bar than you think. The only point you have too much rear bar is when you start getting excessive inside wheelspin.

I've come to the realization that I'm on a compromised setup at the moment and will be changing springs. I'm at max rear bar right now so backing down front bar is my only option without removing and swapping parts. If i'm going to be removing and swapping parts then it's the springs that are getting replaced as the bars should be acceptable for the correct spring setup.

 

[mavisky]

I've been discussing with other competitive autocrossers with this chassis and they're suggesting 600lb front springs.

I'd been looking at the 500lb 2.5x7" Hypercoil springs for AJ's setup since he only offers a 400lb max spring offering.

AJoffers a 1200lb rear that I thought would be similar to the high end of what I've got at the rear from the Steeda dual rates.

According to Steeda these are the rates for the dual rates so this would significantly stiffen the front while keeping the rear about the same which should allow me to dial out a lot of front bar and dial up some rear bar.

Dual rate springs
220 - 350 - Fronts
800 - 1200 - Rears

Steeda competition bars
Front 1.5" bar vs Mustang GT bar - 42% stiffer - 97% stiffer
Rear bar vs Mustang GT bar - 23.6% softer - 13.1% stiffer

This month I ran these above rates and the Steeda competition bars at two events. First event was full soft on the bars front and rear (front bar can only be run at position 3 of 4 due to ride height sensors). Car was neutral, but felt like I was standing up in a canoe with all that body roll.
350lb front
1200lb rear
Front 1.5" Bar at 42% stiffer
Rear Bar at 23.6% softer

Last event I moved both bars to full stiff and the car had pronounced understeer almost everywhere. I couldn't really get the car to oversteer anywhere.
350lb front
1200lb rear
Front 1.5" Bar at 97% stiffer
Rear Bar at 13.1% stiffer

This event this weekend I've dialed the front bar down to the middle notch for the next event while keeping the rear stiff to see how that works out.

I'm thinking the move would be the following
600lb front
1200lb rear
Front 1.5" Bar at 42% stiffer
Rear Bar at 13.1% stiffer

 

[Ewheels]

I almost pulled the trigger on a Steeda competition rear bar but then I saw a post on the TMO facebook page about a guy's Steeda rear bar completely shearing in two. Apparently that's not uncommon....
I guess the point of this is words of warning.

 

[mavisky]

I almost pulled the trigger on a Steeda competition rear bar but then I saw a post on the TMO facebook page about a guy's Steeda rear bar completely shearing in two. Apparently that's not uncommon....
I guess the point of this is words of warning.

Living in the south means that corrosion isn't a concern for me.

 

[EF1]

Living in the south means that corrosion isn't a concern for me.

I agree. The ones I have seen broken look like they were rusted through.

 

[Ewheels]

Should have figured rust could've been the culprit

 

[mavisky]

Ran a new event today with Atlanta Motorsports Park where they ran an autocross style event using a portion of their actual track. The classification system they use has only 3 classes that basically break out to Miata type cars, everything else under 475whp, and then anything above that or lightweight snd big power like turbo Miatas or in our case a Can-Am 900cc turbo side by side on 4 Hoosier slicks.

Finished the event with the second fastest run of the day behind a 1972 firebird wearing 12" wheels, a corvette front suspension and a circle track 3 link rear suspension where you could see the ground through the rear window. Considering I was battling that with a full weight street car I felt pretty decent to only be about a half second back for the second fastest time of the day overall and in class.

Going down one notch on the front bar gave me a car thats very responsive to the front end, but we're still dragging the splitter under heavy straight line braking so this setup is only a bandaid to a better spring setup, but I should be able to make it work the rest of the season.

Made it to about 90 before braking on the uphill section except for the third run where we overcooked it and went two wheels off.