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S197 JDMac's Autocross GT Build Thread Profile - S197 Mustangs

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I love the splitter bracket, keep in mind anything up front needs to be addressed at the rear of the car also.Did you get rid of those press in spacers? Because they really need to go. I'm surprised you didn't get busted at tech with them.
My car has the raised wing that was apparently an option in 2011. My understanding is that the Boss 302 Laguna Seca cars have the same wing with a splitter, so I should be fine without changing anything back there. While I do want to improve my aerodynamics as much as possible, the addition of a splitter is mostly to protect the bumper from cones that tend to jump out in front of me all the time.

I'm assuming that you are referring to the wheel spacers with pressed-in studs - no, I have not changed those out yet. I have brought them up every time that I've gone through tech (mostly autocross but one track day) and nobody has had an issue with them. I check them every time I rotate my wheels (typically every other event) and haven't ever had a loose nut. I can't speak for the Time Trials rules, but there isn't anything in SCCA's Autocross rules saying that I can't use them. Are they the best option? No, probably not. Are they wrong? Also no. However, they are still on my list of things to change.
 
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The splitter project is crossed off the list! It's not perfect but matches the good-from-5ft rule that the rest of the car is on.

I ended up creating the outline based on a few different designs that I saw online. After printing the shape and going through a few revisions, I settled on a 4" offset in the front and 1.5" on each side. The green line is my bumper w/ chin spoiler's profile with a few sets of 1" offset dashed lines. The blue line is the shape of my splitter.
336885314_152209014101351_1727607236120541307_n.jpg

I ended up designing two main brackets that went between the bumper bar and the middle of the splitter, two smaller ones that went from near the headlight to the edges of the splitter, and a couple of splitter rods for the front. I wanted the support rods to go into the chassis somehow, but that seemed to be too much of a pain in the butt. The brackets worked so well that I was comfortable mounting those to the bumper cover instead. All of the splitter-end brackets had slots designed in them to allow for 1.25" of height adjustment. Below is a CAD model of the splitter and brackets, but I revised the main mount soon after.
336879779_208844218399273_9026536830567747780_n.jpg

I ended up making the splitter out of 1/2" plywood. I thought that it would be super heavy, but Autodesk Inventor estimated it to be about 20lbs. When comparing that to the aluminum sheet that I had in mind, it was actually a little bit lighter and a small fraction of the cost. I was able to use a large printout of the profile as a template and cut it out using a jigsaw. The brackets were made out of 1/8" steel. These ended up being about 6lbs, so pretty reasonable considering how strong they should be. After paint and hardware, I'm guessing that this project added a total of around 28-30lbs to the car.

Here are the parts mocked up before painting. Everything fit better than I expected and was as sturdy as I hoped.
IMG_6715.JPGIMG_6716.JPGIMG_6717.JPGIMG_6713.JPG

Knowing that wood and rain/carwashes don't mix well, I made sure to put a lot of paint on it. Both faces got 2 thick coats of interior/exterior gloss black paint, the visible parts of the top face got an extra coat, and the leading edge got probably a total of 5 thick coats. The brackets were just regular spray paint. If I were to do it again, I would have looked into spraying the splitter too. I brushed the paint on which gave it some...character. The brush strokes are visible and I'm glad that I considered that while painting and made sure they all went in the same general direction. Painting the edges caused some runs on whatever face ended up being on the bottom. I tried to watch for this as I was painting but wasn't very successful.

After letting everything dry, I began the final assembly!
IMG_6730 (1).JPGIMG_6731.JPGIMG_6732.JPGIMG_6733.JPG

As I said in the original post, I'm not too concerned with its aerodynamic performance. Any improvement would be great, but that wasn't the main goal. With the tall ride height that I have in the front of my car, this sits about 5-3/4" from the ground. As for weight, I think that the CAD estimate is very close but I did not weigh anything. Overall, I'm very happy with how it turned out.

IMG_6734 (1).JPG
 
99
112
Exp. Type
Autocross
Exp. Level
Under 3 Years
Southern Illinois
The splitter project is crossed off the list! It's not perfect but matches the good-from-5ft rule that the rest of the car is on.

I ended up creating the outline based on a few different designs that I saw online. After printing the shape and going through a few revisions, I settled on a 4" offset in the front and 1.5" on each side. The green line is my bumper w/ chin spoiler's profile with a few sets of 1" offset dashed lines. The blue line is the shape of my splitter.
View attachment 85310

I ended up designing two main brackets that went between the bumper bar and the middle of the splitter, two smaller ones that went from near the headlight to the edges of the splitter, and a couple of splitter rods for the front. I wanted the support rods to go into the chassis somehow, but that seemed to be too much of a pain in the butt. The brackets worked so well that I was comfortable mounting those to the bumper cover instead. All of the splitter-end brackets had slots designed in them to allow for 1.25" of height adjustment. Below is a CAD model of the splitter and brackets, but I revised the main mount soon after.
View attachment 85311

I ended up making the splitter out of 1/2" plywood. I thought that it would be super heavy, but Autodesk Inventor estimated it to be about 20lbs. When comparing that to the aluminum sheet that I had in mind, it was actually a little bit lighter and a small fraction of the cost. I was able to use a large printout of the profile as a template and cut it out using a jigsaw. The brackets were made out of 1/8" steel. These ended up being about 6lbs, so pretty reasonable considering how strong they should be. After paint and hardware, I'm guessing that this project added a total of around 28-30lbs to the car.

Here are the parts mocked up before painting. Everything fit better than I expected and was as sturdy as I hoped.
View attachment 85312View attachment 85313View attachment 85314View attachment 85315

Knowing that wood and rain/carwashes don't mix well, I made sure to put a lot of paint on it. Both faces got 2 thick coats of interior/exterior gloss black paint, the visible parts of the top face got an extra coat, and the leading edge got probably a total of 5 thick coats. The brackets were just regular spray paint. If I were to do it again, I would have looked into spraying the splitter too. I brushed the paint on which gave it some...character. The brush strokes are visible and I'm glad that I considered that while painting and made sure they all went in the same general direction. Painting the edges caused some runs on whatever face ended up being on the bottom. I tried to watch for this as I was painting but wasn't very successful.

After letting everything dry, I began the final assembly!
View attachment 85316View attachment 85317View attachment 85318View attachment 85319

As I said in the original post, I'm not too concerned with its aerodynamic performance. Any improvement would be great, but that wasn't the main goal. With the tall ride height that I have in the front of my car, this sits about 5-3/4" from the ground. As for weight, I think that the CAD estimate is very close but I did not weigh anything. Overall, I'm very happy with how it turned out.

View attachment 85320
Awesome! You have motivated me to give it a shot. It doesn't seem like too much of a challenge. Might go grab some stuff tomorrow. I do want to try and maximize the splitter for Cam-C. Dave says the front end is the limiting factor with downforce now that wings are allowed. I believe 6" past bodywork is allowed for front splitter. I have been looking at splitter ramps and canards also.
 
Awesome! You have motivated me to give it a shot. It doesn't seem like too much of a challenge. Might go grab some stuff tomorrow. I do want to try and maximize the splitter for Cam-C. Dave says the front end is the limiting factor with downforce now that wings are allowed. I believe 6" past bodywork is allowed for front splitter. I have been looking at splitter ramps and canards also.
Yep, 6" past the furthest bodywork is the CAM rule. The center section of our bumper sticks out further than the bottom edge, so that measurement goes from there. Based on that rule, my 4" splitter only sticks out 2-3" and I could have gone 3" longer. I'll probably look into that if I ever swap my factory wing for something more aggressive.
 
The next step for preseason prep was brakes. My rotors were grooved and discolored from the last time I went to the track and cooked my pads. Fresh rotors, pads, and probably fluid were needed. Also, I might have accidentally hung the axle by the rear brake hoses at one point on accident... They never leaked or gave me any trouble, but I'd hate to regret that down the road and decided to swap those out for stainless braided hoses while I was in there.

Hawk Performance is headquartered less than an hour away from me, and they sponsor a ton of events in my area. Between that, the good experience I've had with them on my previous car and current truck, and the discount that Summit Racing had on Hawk parts, I went with them for pads and rotors. I got a set of their 14" Talon rotors for the front and 11.8" rotors for the rear. I decided to go with their HPS 5.0 pads for the street and autocross and DTC-60/30 for the track.

I started at the rear and did not run into any issues. The one weird thing that I noticed was that the caliper needed a little bit more effort to seat before it was able to be bolted to both slide pins on the bracket (this will be discussed later) I figured that it was because of the springs on top. Everything seemed to work fine, so I kept working.

The front was where I ran into my issues. After taking one of the hoses off and trying to install the new set of hoses that I bought, I noticed that the new one was way too short. I tried to orient it in every way possible but it just wouldn't fit. After reading the fitment information listed on LMR's website, I noticed that it was quite vague and figured that they just weren't for cars with the Brembo calipers. Luckily the previous hoses were stainless and had not been abused (to my knowledge) so I decided to reuse them. As I went to put the new pads into the caliper, they were about 1" too short... After double-checking part numbers and dimensions, I realized that the calipers that my car came with were not the Brembo calipers that were offered for the S197 generation. I did some research and found the set of pads that my car requires. According to Hawk's website, the calipers that I have are the 4-piston non-Brembo calipers from an S550 (Hawk PN: 802_). I ordered the correct size, put the old pads back in, and continued with the job.

The next issue came when I went for the test drive to bed in the new rotors and rear pads. I bled the system twice while my neighbor pushed the pedal and everything seemed to get out. As soon as I left, the pedal felt really spongy. It didn't seem solid at all and would go to the floor easier than it did before; not to the point where I felt that it was dangerous, but something to check later for sure. The parking brake would barely work and it took the pads 3 full bedding-in cycles (per Hawk's suggestion) before I considered them to be acceptable. I figured that this was because the fresh rotors had the coating on them and the used front pads had to wear into the new rotors. When I got back and the car cooled down, I tried rebleeding the system and didn't see a single bubble. I went out again and the pedal felt the same. I went to an area with gravel and put the ABS to work hoping to possibly work some bubbles out. I thought that it felt better immediately after but back to before once it cooled down.

A few days later I put in the fresh HPS 5.0 pads and tried bleeding the system again. Again, no bubbles at all. I bedded in the new front pads and the car had as much stopping power as it did before I cooked the old set of pads. After doing some research I saw a thread on here where somebody said that the stock S197 brakes won't ever feel great because of the master cylinder design and that most will pump the brakes before laying on them before a turn. I believed that and considered my job done. I was happy with the braking power and decided to not worry about the pedal feel since it wasn't that bad, just not what I was expecting for a sports car of this caliber to feel like.

I just lifted the car back up to do the final two jobs (oil change and trans fluid change) before the season starts and noticed something odd. Only ~70% of the inside of my rear rotors had been rubbing on the pad because the coating was still on the outside edge.
IMG_6779.JPG

I took the caliper apart and sure enough, there was a nub on the bottom edge of the brake pad that didn't allow for the piston to sit flush on the inner pad's backing. This caused the bottom edge of the pad to make contact before the top even touched. The pictures below show the marking on the pads and piston. The green circle shows the nub that is making contact.
IMG_6773.pngIMG_6774.JPGIMG_6775.png

I am 90% sure that this is what is causing my poor pedal feel, parking brake lever feel, and parking brake performance. As I was writing this I realized that the notches in the piston need to be lined up correctly so that the nub on the pad sits in there instead of on the face of the piston.... damn it... I'll fix that issue and continue with the oil change tomorrow afternoon. Hopefully I'll be able to say that my brake pedal feels better and that all will be good once it's back on the ground and I have a chance to test the brakes.

I'm going to go have a drink and kick myself because I missed something dumb but celebrate that the fix was easy. Cheers! 🍻
 
225
177
Exp. Type
Autocross
Exp. Level
Under 3 Years
Colorado Springs
View attachment 85724

I am 90% sure that this is what is causing my poor pedal feel, parking brake lever feel, and parking brake performance. As I was writing this I realized that the notches in the piston need to be lined up correctly so that the nub on the pad sits in there instead of on the face of the piston.... damn it... I'll fix that issue and continue with the oil change tomorrow afternoon. Hopefully I'll be able to say that my brake pedal feels better and that all will be good once it's back on the ground and I have a chance to test the brakes.

I'm going to go have a drink and kick myself because I missed something dumb but celebrate that the fix was easy. Cheers! 🍻

Question, when you thread in the piston, it sets in like the above yes? Once you drive n brake, when you remove the caliper, the piston is still recessed like that right? I am thinking I am not getting mine set in all the way and thats why I am getting some brake squeal all the time. Do you use the special tool or just redneck engineering to set it in?

PS, love that style hood, looks badass. It's what I want, but since I am cutting the stock up, just gonna live with it.
 
Question, when you thread in the piston, it sets in like the above yes? Once you drive n brake, when you remove the caliper, the piston is still recessed like that right? I am thinking I am not getting mine set in all the way and thats why I am getting some brake squeal all the time. Do you use the special tool or just redneck engineering to set it in?

PS, love that style hood, looks badass. It's what I want, but since I am cutting the stock up, just gonna live with it.
The green arrows are where the notches should be relative to your caliper - straight up and down. If you are able to set your mount your caliper correctly without forcing it, the piston should be in enough. What brake pads are you using? They might be the cause of your squeal if they are an aggressive compound.

Untitled drawing.jpg

Guys, buy the tool. The set of tools will save time and money in the long run. Press the piston in while turning.
What he said - either buy or rent. I bought my tool last year and have used it more than I expected. I'm all for redneck engineering some things but don't want to risk damaging a vital brake component.
 
Yep, 6" past the furthest bodywork is the CAM rule. The center section of our bumper sticks out further than the bottom edge, so that measurement goes from there. Based on that rule, my 4" splitter only sticks out 2-3" and I could have gone 3" longer. I'll probably look into that if I ever swap my factory wing for something more aggressive.
Yes, a 6" overhang is pretty far when you look at it.
52723850065_464d10f405_o.jpg

If you go this far I'd reconsider your support mounts as I built chassis mounts and re-located the support struts to the bumper support bar vs just the actual plastic bumper.
 
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225
177
Exp. Type
Autocross
Exp. Level
Under 3 Years
Colorado Springs
The green arrows are where the notches should be relative to your caliper - straight up and down. If you are able to set your mount your caliper correctly without forcing it, the piston should be in enough. What brake pads are you using? They might be the cause of your squeal if they are an aggressive compound.

View attachment 85739


What he said - either buy or rent. I bought my tool last year and have used it more than I expected. I'm all for redneck engineering some things but don't want to risk damaging a vital brake component.


I think you misunderstood my question. I wasn't asking about the alignment of the notches and where they go, I was specifically asking about how far in did you thread the piston and is it still recessed to that same depth after use.

There wasn't a rental device at the local shop but my caliper tool arrived this week. threaded the caliper all the way in (which was a solid qtr inch) more than it was when I removed it, reinstalled, squeaky brakes resolved. I think it was in enough that i could mount, but not in enough that it didn't drag.

I am using Hawks, but I cannot find the box they came in to see which ones are on the rear. No squeaks today after adjusting the driver rear tho....
 
I think you misunderstood my question. I wasn't asking about the alignment of the notches and where they go, I was specifically asking about how far in did you thread the piston and is it still recessed to that same depth after use.

There wasn't a rental device at the local shop but my caliper tool arrived this week. threaded the caliper all the way in (which was a solid qtr inch) more than it was when I removed it, reinstalled, squeaky brakes resolved. I think it was in enough that i could mount, but not in enough that it didn't drag.

I am using Hawks, but I cannot find the box they came in to see which ones are on the rear. No squeaks today after adjusting the driver rear tho....
Correct, I did misunderstand your question. As I was pressing the caliper in I slowed down and made sure to stop as soon as it bottomed out. When I went to install my track pads last night the piston was extended to its usual position.
 
After fixing that silly mistake, by brakes feel better. I pulled the rear pads after a day of driving and the uneven wear was still noticeable; hopefully they improve even more once that goes away.

NEOhio SCCA has a motorsports expo tomorrow morning and a Track Night in America at Nelson Ledges. In preparation for that, I installed my set of Hawk DTC-60 and DTC-30 track pads last night. Holy crap. I about ripped my seat belt out of the chassis when those hit full stopping power. I was very impressed with how well they stopped compared to my HPS 5.0 pads.
 
TNIA went well, but the weather was terrible. I think that we had a high of 50° and on-and-off rain all day. It was really slick all day and I think I only had a handful of laps where I felt confident with the car.

Unfortunately, I did run into some issues. As soon as I got on track I was having issues with AdvanceTrac interfering when it didn't need to. As I was entering or mid-corner I would feel it try to engage the inside brakes even though I had full traction. The car was fine once I turned it off, but it is something that I'd like to look into further because a wet track was pretty sketchy knowing that I didn't have anything to save me if I needed it.

Also, I had a weird thumping/grinding noise towards the end of the day. I'm 80% sure that it's just tire rub on the fender liner, which should be easy to fix.

Other than those two things, the car did pretty well given the power that it has as well as the driver it had. I left the track thinking that my car had a bad oversteer problem, but I noticed a lot more understeer after editing my video. I'm guessing that the two oversteer events were more serious and are stuck in my head because of it.

Here is the video of my close calls. I have the full video uploaded on my channel as well.

I think that both of those slips were caused by driver error and that I hit the brakes a little too hard and a little too late. Below are the adjustable suspension settings that I was at for most of the event. I got these based on my experience with the car on large and smooth autocross courses.

Whiteline Sway Bars
Front Stiffness: 4/4
Rear Stiffness: 2/4
Pedders Coilovers
Front Damping: 24/32
Rear Damping: 20/32
Tires
Front Cold Pressure: 36 psi
Rear Cold Pressure: 36 psi

In the middle of the second session, I lowered my damping setting to what I believe was 6 front and 2 rear which seemed to make the car much more predictable. With how slick it was, I should have done that way earlier.

In the past, 4 extra clicks of front damping made the car pretty well-balanced. I could get the car to experience both understeer or [mostly] oversteer depending on what kind of inputs I'd give it. I'd like to set the rear sway bar to full soft and see what that's like.

Do any of you have any suggestions on things to try? I have an autocross Test and Tune event this Saturday and planning on finally spending the time to fine-tune the shocks.
 

Bill Pemberton

0ld Ford Automotive Racing Terror
8,623
8,799
Exp. Type
Time Attack
Exp. Level
20+ Years
Blair, Nebraska
My question is why were you running your tires at such a high pressure cold , since they probably should have been no more than that hot.........and likely even a little less, imho.
 
My question is why were you running your tires at such a high pressure cold , since they probably should have been no more than that hot.........and likely even a little less, imho.
36 or 37 hot is what I had to have them set to at autocross last year to keep them from rolling over and rubbing the sidewall. It seemed a lot higher than I expected, but I tested that with both chalk and a paint marker with similar results. With how cold and wet it was, the tires didn't get any heat in them. I checked the pressures at the end of the first session and it was within half a psi from what I started with.
 
I thought it was high too. I'll try lowering them at the test and tune this weekend, but 36 or 37 seemed to be where it was happy last time
It may have to do with squeezing the 315 onto an 11" wheel. It will fit but it's a little squeezed which will want to make it roll over more. That tire mounted on an 11.5" or 12" wheel would probably roll over less at lower pressures.
 

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