SCCA F-Street Setup. What's Everyone Done so Far?

[Dana Pants]

So did anyone increase the rear brake bias with a pad change yet? I saw it discussed around page 47 without conclusion. Trail braking isn’t working for me... it just understeers and understeers.

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[DickR]

So did anyone increase the rear brake bias with a pad change yet? I saw it discussed around page 47 without conclusion. Trail braking isn’t working for me... it just understeers and understeers.

I have thought about doing this but a couple of things (other than inertia) have caused me to question the need/value.

1) When Mark Daddio, who you probably know or have at least heard of in the NE, drove my 18 at the NJ Pro and when Sam Strano drove my 15 at practice events neither had any trouble making the car rotate. Both cars were/are GTPP's.

2) I don't know if ABS and/or EBD would actually allow the effective bias to change with a pad change either F or R. The last time I tried this before changing to a CM FF was with a Datsun 260Z back in the 70's. It worked then but obviously no ABS or EBD. Plus the Z had LOTS of trailing throttle oversteer due to suspension geometry to the problem was to tame it with high grip front pads. With our cars playing with pads might simply encourage the Camaro problem commonly called "ice mode".

Info from the FSM:

Anti-Lock Braking

The ABS module continuously monitors brake pedal input, longitudinal vehicle motion and the rotational speed of each wheel. The ABS module receives the brake pedal input from the PCM and the longitudinal acceleration sensor information from the RCM . The PCM sends the brake pedal input message to the GWM over the HS-CAN1 , the GWM relays the message to the ABS module over the HS-CAN2 . The RCM sends the longitudinal acceleration sensor message directly to the ABS module over the HS-CAN2 . Wheel speed information is received by the ABS module using 4 wheel speed sensors. When the ABS module detects an impending wheel lock during a braking event, the ABS module modulates brake pressure to the appropriate brake caliper by opening and closing the appropriate solenoid valves inside the HCU while the hydraulic pump motor is activated. Once the affected wheel returns to the desired speed, the ABS module returns the solenoid valves in the HCU to their normal position and deactivates the hydraulic pump motor.

When the ABS module is initialized (ignition ON), a preliminary electrical check of the wheel speed and brake booster vacuum sensors is carried out, and the hydraulic pump motor is activated for approximately one-half second. During this time, a buzzing or humming noise may be heard and a vibration may be felt in the brake pedal, this is a normal condition. During the module initialized self-test, the pump motor check is carried out at approximately 10 km/h (6.2 mph). Any malfunction detected in the system causes the ABS module to set a DTC , disable the ABS function and send a message to the IPC to illuminate the ABS warning indicator. The base hydraulic power assist braking system functions normally.

Electronic Brake Force Distribution (EBD)

On initial application of the brake pedal, full pressure is applied to the rear brakes. The ABS module then uses wheel speed sensor inputs to evaluate rear wheel slip. Once the rear wheel slip exceeds a predetermined threshold, the ABS module commands the HCU to close the appropriate isolation valves to hold the rear brake pressure constant while allowing the front brake pressure to build. This creates a balanced braking condition between the front and rear wheels. If the rear wheel slip continues and exceeds a second predetermined threshold, the ABS module commands the HCU to open the dump valves to decrease the rear brake pressure and allow the rear wheels to recover. A slight bump sensation may be felt in the brake pedal when EBD is active.

If the ABS is disabled due to a DTC being present in the ABS module, EBD continues to function unless the DTC is for wheel speed sensors or the HCU . When EBD is disabled, the ABS warning indicator, the red brake warning indicator and stability-traction control indicator (sliding car icon) illuminate.

 

[thasuperdude]

Thanks for the replies. So yeah, the PS4Ss are, um how do I say it, not great? Maybe a better track/street tire, they were fine in the mountains. I'm well aware of the RE71s and what they are, so I'm not holding these to their worthiness. But yeah, the initial turn-in is extremely slow. I found 36ish front was working, but I really didn't dick with tires as much as understanding what all the different drive setting do on-course. Track mode with TC & SC full-off and 4-wheel slides don't mix well. It turned everything back on and set off like 5 different bells. Hope that's not a normal occurrence.

I went into Sunday wanting/expecting to wrangle in the rear-end all day, but it was the front-end that wasn't doing what it was told. It was a super busy and slow course so that didn't help, but I learned a lot. Out of the box it's fun and kind of fast, but it drove more like my WRX than the M3. It took me years to dial in oversteer on WRX with a bunch of parts, the M3 was a plug and play car. I didn't do a thing to it and it was fast and turned like no other car I've driven. The last 2 years I autox it with PS A/S 3+'s and I feel those tires had better turn-in bight. Side note: After running RE71s for 3 years, run a set of good all seasons for fun. It's a blast, trust me.

With that said, this car/chassis is a blast and a lot more challenging. My best run was up there with everyone else in my class, so it shows me it can be fast for sure. Most everyone was on RE71s and familiar with their cars, so I feel good about the GTs potential.

Seat time, alignment and I'm guessing a front bar to tighten things up? A lot more reading and chatting is needed for sure.

 

[jpaulson]

So did anyone increase the rear brake bias with a pad change yet? I saw it discussed around page 47 without conclusion. Trail braking isn’t working for me... it just understeers and understeers.

I had some hawk money to spend so I am running HPS 5.0 in back and OEM PP pads up front. I think it improved the balance but it is a pretty subtle change. Haven't noticed any I'll effects.

 

[thasuperdude]

Ok, so I didn't do as bad as I thought. I'll take 2nd in class, only to be beat by a nicely modded '14 GT. 24th in RAW time, too. So after some Monday morning QBing on myself, I think I could have left the car in 1st for most of the course. It was a Miata course and a new car to me, so I didn't really think it though on Sunday. I might have gotten over 4k once on course. I'm going to leave it as is and see if I can fix my driving style before I go dicking with alinements and bars. It didn't like late-braking too much and I can fix that easily.

 

[Dana Pants]

Has anyone gone ultra mega stiff on the front bar and what was the result? I already have a redrilled front bar and was surprised to see the low load on the inside rear tire. Legend has it that sometimes a big front bar helps camber loss and actually increases front grip. My general complaint is insufficient front end grip and pushyness for steady state cornering.

 

[BmacIL]

Has anyone gone ultra mega stiff on the front bar and what was the result? I already have a redrilled front bar and was surprised to see the low load on the inside rear tire. Legend has it that sometimes a big front bar helps camber loss and actually increases front grip. My general complaint is insufficient front end grip and pushyness for steady state cornering.

People have tried both stiffer front and stiffer rear with success. If you drive with the throttle, stiffer front will help. If you do more of your rotation on corner entry, then stiffer rear. Legend is right though.

 

[NightmareMoon]

People have tried both stiffer front and stiffer rear with success. If you drive with the throttle, stiffer front will help. If you do more of your rotation on corner entry, then stiffer rear. Legend is right though.

When I was playing with front bar setups, advice at the time seemed to be to use the Medium front bar setting.

Once the bar is on there its only a few minutes to change settings. Try it out and see if you like it. I was happy with the balance and grip on Medium, but YMMV. If you want the rear to plant, add throttle.

 

[Dana Pants]

When I was playing with front bar setups, advice at the time seemed to be to use the Medium front bar setting.

Once the bar is on there its only a few minutes to change settings. Try it out and see if you like it. I was happy with the balance and grip on Medium, but YMMV. If you want the rear to plant, add throttle.

Medium for what? a 35 mm bar?

 

[NightmareMoon]

Medium for what? a 35 mm bar?

I was on a 35mm BMR front bar at the time, not one of the 38mm Texas sized front swaybars.

 

[BmacIL]

When I was playing with front bar setups, advice at the time seemed to be to use the Medium front bar setting.

Once the bar is on there its only a few minutes to change settings. Try it out and see if you like it. I was happy with the balance and grip on Medium, but YMMV. If you want the rear to plant, add throttle.

FWIW @Dana Pants I went from the stock GT bar to the BMR front bar on the middle setting before my autocross this weekend. Holy cow what a difference! Still GT PP OE rear bar, but man does it keep the front flat and plant the outside tire hard. It reduced understeer dramatically, but did so in a way that allowed me to use the throttle a lot more and with a lot more confidence.

 

[Whiskey11]

FWIW @Dana Pants I went from the stock GT bar to the BMR front bar on the middle setting before my autocross this weekend. Holy cow what a difference! Still GT PP OE rear bar, but man does it keep the front flat and plant the outside tire hard. It reduced understeer dramatically, but did so in a way that allowed me to use the throttle a lot more and with a lot more confidence.

Which is why some of us run a front bar instead of the rear bar... on my 2015 GT/PP we have the BMR bar at the softest setting (like 15% stiffer than stock or something, not much, just enough). It made a huge difference. I have run it in all three settings and full stiff is absurdly pushy in tight elements and pretty "lazy" turning in. I'm zero toe all around and about -2.1 degrees camber all around (including out back). Anyway, with the bar in the softest position it works really well. Plenty of rotation at entry, some lift off oversteer in really high speed sweepers but overall very well controlled in slaloms. It works for Justin and I, and we seem to be capable of trophying, but when it comes to catching Cashmore and the other Bimmers... I think it's a lost cause. I'm not sure anyone of us can do it. The M3 is just that fast of a car and Cashmore is just that fast of a driver.

 

[BmacIL]

Which is why some of us run a front bar instead of the rear bar... on my 2015 GT/PP we have the BMR bar at the softest setting (like 15% stiffer than stock or something, not much, just enough). It made a huge difference. I have run it in all three settings and full stiff is absurdly pushy in tight elements and pretty "lazy" turning in. I'm zero toe all around and about -2.1 degrees camber all around (including out back). Anyway, with the bar in the softest position it works really well. Plenty of rotation at entry, some lift off oversteer in really high speed sweepers but overall very well controlled in slaloms. It works for Justin and I, and we seem to be capable of trophying, but when it comes to catching Cashmore and the other Bimmers... I think it's a lost cause. I'm not sure anyone of us can do it. The M3 is just that fast of a car and Cashmore is just that fast of a driver.

I'll have to try the other settings with my setup, as I'm running 245/980 spring rates vs your 165/728 for FS, but also have those massive rear control arm bushings removed (which add a good amount of stiffness).

 

[Schnupper]

The front bar maybe my next purchase. I'm currently stock gt pp with square 275 g force rivals. I hate the understeer the car has.

 

[DickR]

The front bar maybe my next purchase. I'm currently stock gt pp with square 275 g force rivals. I hate the understeer the car has.

FYI the Tire Rack comparison test against the RE-71R indicated that the Rival is more "understeery".

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