SCCA ESP Thread

[boardkat]

yep, 315/30R18 A7s on 18x11. fender liners still there, no rubbing. significant wheel offset difference front to rear though, to keep the wheels off the strut/spring perch up front..

the issue i'm having with the rear is not having ENOUGH spring. 1600# is only about 385# wheel rate due to motion ratio - and at my current weight, only about 2Hz. i already have a set of 2000# on order, and will most likely try 2400# as well. on bumpy courses, the problem i'm having is with shock - given the relatively soft rear, and having only 2.5" of shock compression travel from static ride height coupled with being underdamped, i'm running out of travel, and riding on the internal bumpstops. i expect with more spring and a revalve (and possibly a shortened body for more travel), that my issues will disappear.

700# up front currently, but i expect to move up to 800# and testing 900# and 1000# once i get the rear figured out.

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[Sock]

Is your rear spring in the stock location? Motion ratio is .48 in stock location.


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[boardkat]

Is your rear spring in the stock location? Motion ratio is .48 in stock location.

yep. i came up with a different result when i measured (0.49), but seems we arrived at similar conclusions - it sucks!

... and i'm powerless to do anything about it in ESP unless (until?) they change the rule to allow relocation. i wrote a letter last month proposing this allowance, i expect to see a response in the next fastrack or two..

 

[341hcmonster]

yep, 315/30R18 A7s on 18x11. fender liners still there, no rubbing. significant wheel offset difference front to rear though, to keep the wheels off the strut/spring perch up front..

the issue i'm having with the rear is not having ENOUGH spring. 1600# is only about 385# wheel rate due to motion ratio - and at my current weight, only about 2Hz. i already have a set of 2000# on order, and will most likely try 2400# as well. on bumpy courses, the problem i'm having is with shock - given the relatively soft rear, and having only 2.5" of shock compression travel from static ride height coupled with being underdamped, i'm running out of travel, and riding on the internal bumpstops. i expect with more spring and a revalve (and possibly a shortened body for more travel), that my issues will disappear.

700# up front currently, but i expect to move up to 800# and testing 900# and 1000# once i get the rear figured out.

Much appreciated on the response.

 

[boardkat]

been awhile since i've updated this. work's been crazy :(

started planning for 2016. i've been a bit gun-shy to go all-in with an fully spec'd ESP build, given that STP is now on the table and i expect that an S550 will eventually be competitive in absence of the 10/285 restriction (good on you, chris, for building in spite of this). however, i can't sit idly by and wait for that to happen in a few years, so i've made a conscious decision to go off the deep end! here's where i'm headed, over and above where i'm already at:

18x12/335 square setup
47lbs/hr injectors
edelbrock IM
FRPP 90mm TB
E85
8,300RPM
splitter/spoiler
weight reduction (no more stock recaros, tow hitch, stock mufflers)

more to follow, stay tuned

 

[Schu]

Very interested... I had always though 12's were in the future for this chassis.

 

[boardkat]

335/18x12 vs. 315/18x11
p.s., they fit

 

[boardkat]

unfortunately, i have to wait a little while longer on extra power with the new IM/TB/injectors/E85. ford packing ftl :(

 

[Simmons-Racing]

335/18x12 vs. 315/18x11
p.s., they fit

They fit without cutting?

Simmons

 

[Grintch]

They fit without cutting?

Simmons

Up FRONT?

What offset & aspect ratio?

 

[boardkat]

They fit without cutting?

Simmons

in the rear, yes. need to wait until my reworked MCS struts are back before i can verify how much fender i need to cut up front for them to work.

 

[SteveW]

You're gonna need a bigger trailer, haha

 

[boardkat]

GT350 IM/TB & 47lb injectors installed:

still working out the kinks with surge/hanging on my tune, but i did finally find the culprit for 3deg of timing retard above 6000rpm:

*highly* recommend anyone with longtubes to confirm that you have enough clearance to the a/c line bolt & bracket!

car fell off the wagon today, too!

15.6 gallon fill, only took a few miles for the gas to clear and the flow/timing to increase. hitting the dyno tomorrow.

 

[boardkat]

tl;dr
18x12/335 "fits" in the rear, but only verified under a very specific scenario with almost no inboard/outboard room.
There are certain modifications that will open up the ability to fit under almost all scenarios.
Read further for more info

The packages I've been waiting (2) months for finally arrived Friday: (2) Forgestar CF5 18x12 wheels. I forgot to grab a pic of the wheel weight before I mounted the tire, but my bathroom scale said 25.6lbs. I wasted no time mounting the Hoosier A7 335/30R18 tires I picked up a few months back.

This setup is WIDE. ~2" wider than my existing 18x11/315 setup.

"I don't think I could use another couple inches"
- said nobody, ever.
:lol:

First thing to try: bolt on and see what happens! Note that my current camber in the rear is -2.4, and I'm lowered from stock about 1".

They fit! Well, at least at full droop. Jacking up until the spring started lifting the car, I still had no interference. That said, I couldn't fit a poker chip (3mm) between the upper shock mount and the tire, so there's almost no space. I'm also equally close to the e-brake bracket, but figure it'll self-clearance. But the tire freely rotated, so there's "something" there!

First observation: I'm running a *lot* of camber - more than I want to run when I get my rear perches installed and can finally run 2000lbs+ of spring. So inboard clearance will improve when that happens (at the expense of outboard clearance, of course). After I unbolted the wheel, I put a 3mm spacer on, and retried - poker chip fit this time. And to be completely honest, I expected this - my math said I should have optioned a wheel with 3mm less offset, but I knew I could run a spacer if needed - my ultimate goal is to keep as little inboard clearance as possible, so that I don't have to pull the fenders too much. Mission accomplished in the near future when I take out some camber.

For fun, I unbolted the front wheel, and tried fitting the same wheel with a 1.5" spacer. Here's what it looked like at full droop.

This was the first surprising news of the day; before that though, a little history. With the recent work I had MCS do to machine the strut piston down so that it would fit below the center clearance hole, I was able to remove my camber plate spacers and move my spring perch back above the wheel/tire. As a result, I gained back about another 8mm of inboard clearance. Why is this important? The 18x12 loses about 8mm of inner clearance relative to the 18x11, so in the end it's a wash (theoretically). Well, in practice too! I have about 2mm to the strut, and the wheel freely rotates, so I'll be able to run a square setup and rotate front/rear. Should enable me to get a little more life out of my tire$$$ as a result. Gotta love math

For even more fun, I took the spring off and saw how far I could compress until fender interference.

The wheel articulates a LOT, given the -3.75 camber that I'm running. I'd been planning to bump the front spring rate up when I go stiffer in the rear, and the net result might be that I never find myself compressed that much, meaning I could continue to run the stock fenders. But as you already saw, it just looks plain stupid And since I've already got an extra set of fenders, I just need to spend some time cutting and flaring, now that I have my wheel/tire setup to test against. Soon

Back to the rear. I did the same here, and took the spring out to compress fully and see what (if anything) would cause interference.

As you can see, it compresses. Fully. With no interference. To be sure, I took the car for a spin around the block, and hit some potholes at speed. Came back, unbolted, and inspected. No rubbing, anywhere. No fender deformation. And the zip ties on the shock pistons told me that I did compress both sides almost fully. Meaning if I want to bolt this setup on and go race right now, I don't need to do *anything*. I didn't think I'd be able to say that (and it would be by no means ideal in terms of setup), but kinda cool that I could if I wanted to.

Here's a few shots of the rear at static ride height; obviously the rear springs haven't fully settled, although the 335 is a very short tire (25.6").

Next steps: I'll be pulling the rear fenders a bit, to give myself some breathing room when I take some camber out. Rather than run a rear spacer, I'll probably shave the upper shock mounts a few mm.

As the picture above shows, they're already angled the correct way, so I'll only need to mill a small amount off near the bottom (hopefully maintaining the integrity of the mount). Hoping the aftermarket comes up with something eventually (if only to get rid of the soft rubber).

If you've read this far, you're probably wondering why I haven't mentioned offset. To be honest, I don't want to be held accountable by anyone trying something similar and not having it work for them. It's still a work-in-progress as far as I'm concerned, and until I've actually gone out and raced on them without any gotchas, I'm going to keep it to myself. But rest assured, it won't be long

 

[jhols]

Way to push the boundaries! I would have never of guess that we could fit 335s up front with the stock fenders! You are doing god's work.

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