Rear Spring

[TeeLew]

I've got the rear subframe out of the car and doing my differential thing. I'm presently on 750# rear springs and going to try something softer. I've got two options. So what do you think? Do I try the 650's or the 500's?

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[TeeLew]

Well, I got this message loud and clear.

 

[GTP]

LOL. You aren't patient enough, it's only been 1/2 day!

I would say that a 10% spring change is noticeable, so I would try the 650#.

 

[WCRookie99]

Well, I got this message loud and clear.

Maybe this will help.

2017 Ford Mustang FP350S Race Car Review: Performance (p)Art (motortrend.com)

650/600

Boss S Race car spring rates | Track Mustangs (trackmustangsonline.com)

600/350

Starting Point for S197 AI spring rates - American Iron Racing - #DRIVENASA Community

750/450

 

[TeeLew]

Maybe this will help, looks like you're way off.

Boss S Race car spring rates | Track Mustangs (trackmustangsonline.com)

Oh, deary me, what will I ever do. Someone else is running a different rate.

P.S. That's not the right car.

 

[K4fxd]

I'm gonna say 500, take a big swing at it. I'm sure after a track day or 2 you will swap again no matter which you start with.

 

[TeeLew]

I'm gonna say 500, take a big swing at it. I'm sure after a track day or 2 you will swap again no matter which you start with.

That's kinda what I'm thinking. I know it's probably too soft, but what does too soft feel like? Maybe swapping my 20mm RARB out for my 24mm one will get the roll couple back in a good window? On the other hand, is it just silly soft and wasting time and effort? Then I look at the Phoenix T1 car on track. I bet its wheel rate is no more than this, but it's a live rear, so that's a bit of a different movie.

It'll be a few hours before I'm bolting it back up.

 

[WCRookie99]

Oh, deary me, what will I ever do. Someone else is running a different rate.

P.S. That's not the right car.

look again, google helps!

 

[TeeLew]

When I click on your link I see a 600F/350R recommendation for a S197 chassis.

I haven't done what everyone else has done on spring rates, so I'm used to people telling me I'm doing it wrong.

 

[TeeLew]

Rear spring put off for a day. 1 vote for 500's, so that's what I'll do. Why stop at Chicago on your way to New York, right? I'll have the subframe studs installed going back in, so if I don't like them, it's really only a couple hours to drop the sub and change them. I bet the rear will be really stuck, but it might be a wet noodle as well.

So I ended up having to swap the pinion flange for the new rear end and I'm going to put a new nut on, so I have to wait until tomorrow AM to get that. I removed my red puck bushing kit from the subframe bushings and then cut the stocks subframe bushings out. It does a man good to tear shit up with a Sawz-All from time to time. I've installed the Whiteline kit to take place of the stock stuff. Those were officially the last stock bushing in the car.

The AL housing and Traction Lok diff are about 32 pounds lighter than the cast-iron housing and Torsen Diff. Having said that, the FluiX finned rear cover I'm using is 11# heavier than the stock rear cover. In the end, I'm right at 21# lighter with the new rear end combo. It's very noticeable when moving the two around. Since I'm changing the diff so much as well, there's no guarantee this will be better that what I had before, but it will be a bit lighter. When you factor in that I've also addressed the cooling issue, then it's a hell of a lot lighter than the cast iron equivalent with a rear end pump and cooler arrangement.

I've been giving my new hydraulic table that I bought for this project a good workout. I don't know how I made it through the day without it.

 

[K4fxd]

Since I'm changing the diff so much as well, there's no guarantee this will be better that what I had before, but it will be a bit lighter.

Why not swap the torsen into the Al housing?

 

[K4fxd]

I bet the rear will be really stuck, but it might be a wet noodle as well.

I'm sure you will need more bar, I'm about to remove my 800's so am interested in how ends up.

 

[TeeLew]

Why not swap the torsen into the Al housing?

The whole exercise is to put a 3.15 gear in the car, which will come in handy for Auto-X (I'll be able to stay in 2nd the entire time. Keep in mind, I'm an Eco, so 1000 fewer revs than a Coyote). When you change to the 3.15, it's a smaller ring gear, so the Torsen doesn't fit. It only works with 3.31 and numerically higher ratios. That means you're stuck with the Traction Lock diff, which sucks. To reduce the suckage, I've made alternative differential plates, so my Traction Lock will have a significantly higher preload and torque bias than a stock diff. I'm also going to guess it's a little noisier, but that remains to be seen.

I'm putting in Whiteline diff bushings. I previously had the BMR red pucks over stock rubber. This should be a little more robust. Rear subframe studs are going in from Kell-trac. The last thing to plop in will be the rear spring du jour.

I'm leaving the 20mm RARB on to start with just to have a good back-to-back comparison, but I have a 24mm bar that's easy enough to pop on.

 

[K4fxd]

I've got a set of the kel-trac studs or more accurately all thread.

I don't trust them since there is no way to tighten them to the car. What I do use them for is I'll remove the bolts one at a time and replace with the studs. This makes it easy to lower the cradle and when done I pull the studs and use the bolts for final assembly.
.

 

[GTP]

I've got a set of the kel-trac studs or more accurately all thread.

I don't trust them since there is no way to tighten them to the car. What I do use them for is I'll remove the bolts one at a time and replace with the studs. This makes it easy to lower the cradle and when done I pull the studs and use the bolts for final assembly.

Same here. I made my own set. Each all-thread is 10" long!

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