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Oricle

Member
Jul 12, 2010
61
57
I've been co-driving and working on setup in a Roadster for 3 seasons now and I feel like I'm finally getting to the point where the car is quick and playful around the cones, so I thought id share my setup and hopefully start a serious discussion about autox setup and driving technique for this car. I've also been petitioning the SCCA Solo Events Board (and failing) to move the Roadster from SS to AS class where I think it'll be more competitive, and to allow the Roadster into the CAM classes so modified Roadsters have a class to compete in.

2017 setup for Super Street class:
Roadster 2.0 (Non Sport)
"Normal" drive mode (not Performance)
TC Off

Tires:
RE-71R
F: 205/45-16 (34psi hot)
R: 245/40-17 (43psi hot, +/- 2psi depending on surface grip and rotation)

Wheels:
Stock (non-sport)

Brakes:
F: EBC Yellow
R: EBC Yellow (may change to a more aggressive rear pad next season)

Dampers:
F: Stock Sport Suspension (7)
R: Stock Sport Suspension (3)

Sway Bars:
F: BWR "Hardcore" (Full Stiff)
R: Stock Sport Suspension (Full Stiff)

Alignment:
(I dont have the alignment print out anymore, but I know what the shims are)
F: Max Caster (all washers in front)
Max Camber (No shims)
0 Toe
R: Camber (2 shims)
0 Toe

Ride Height:
(No actual height measurements because I'm running at the ends of adjustability)
F: Min height
R: Max height
 

Oricle

Member
Jul 12, 2010
61
57
What is the benefit of running in std. drive mode, instead of performance mode in AutoX?

Heat and power. The car will heat up too quickly in Performance mode, and when it's hot out it'll go into reduced power mode. Performance mode also has a narrow temperature operating window, after a few full power corner exits the car goes into "Red" performance mode, which is nearly the same as standard mode.

On a cold day, you might be able to stay in "White" performance mode for the first lap, but the first lap is usually never your quickest (due to tire temp and unfamiliarity with the course layout), and after the first lap it's just inconsistent power delivery. As a driver, it's easier to push the car hard when you can anticipate the amount of power the car will deliver.
 
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DieAbetic

Member
Jan 16, 2014
168
16
Los Angeles
Hey there fellow SCCA member! I’m running my Roadster in SS now :)

Why did you go with 245R 205F? Doesn’t that cause understeer?

I heard RE71Rs like 28-34 PSI hot. Why go with regular recommended higher PSI?

Sorry for all the questions - you are the only one i can ask! Lol. As you know at the meets you get lots of advice... I’m just not technically knowledgeable enough to figure out the best setup (yet).

Thanks for all the research and help!
 
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Oricle

Member
Jul 12, 2010
61
57
Hey there fellow SCCA member! I’m running my Roadster in SS now :)

Why did you go with 245R 205F? Doesn’t that cause understeer?

I heard RE71Rs like 28-34 PSI hot. Why go with regular recommended higher PSI?

Sorry for all the questions - you are the only one i can ask! Lol. As you know at the meets you get lots of advice... I’m just not technically knowledgeable enough to figure out the best setup (yet).

Thanks for all the research and help!

Hey! Nice to see another AutoX'r on here.

Unfortunately the Roadster has really narrow wheels, add to that the stagger in wheel height and width, and supposedly a finicky regen and ABS when running a different circumference stagger than stock, that makes tire choices is extremely limited.

For the 2015-2016 season we went with a 205/50r16 235/45r17 setup that worked well. The tire sidewall was quite a bit taller than stock which made the tires a bit squirmy which I didn't care for, and theoretically made it slower to accelerate due to the effective gear ratio change.

2017 season we switched to the 205/245 setup with shorter sidewalls. My datalogger broke so I can't compare acceleration between the tires, but honestly the difference probably would be negligible. The main improvement is in response, the shorter sidewall with higher pressures makes the car much more precise. Since the tires are quite a bit wider than stock (but still on skinny wheels), they seem to like the higher pressures more. I started out the season at 25psi front 30psi rear, and every time I added more pressure the car felt better and was quicker till I got to 34/43.

Corner entry is easily the most difficult part of racing the Roadster. The ABS system comes in too early and strong, and is biased too far to the front (in my opinion). The trick to getting the car slowed down is a light initial pedal application (to get the weight shifted to the front), then gradually roll into the pedal firmly but stay out of the ABS as much as possible. If you jump into the pedal full force, the ABS locks out the rear brakes, overpowers front grip, and the car comes to a worryingly gradual and understeery stop (you can test this on the street to see what I mean). So, best way to enter a corner is by getting on the brakes early and soft initially, then roll into the pedal without getting into ABS in as straight of a line as possible, trail brake on turn-in to get a little rotation/minimise understeer. Steady state cornering is pretty neutral with the current setup, I can tighten a line easily by letting off the accelerator. Corner exit will probably always understeer, unless you are really aggressive with it (lift off, quick turn in, stab the accelerator) but that's not very fast. Typical corner exits are fastest when you get the car pointed as quickly as possible, roll on the accelerator as you straighten out the steering expecting the line to loosen and track out wide. Finding that balance takes practice. Getting on the accelerator too early unloads the front tires and understeers bad. Too late and too abruptly spins the inside rear and the car won't accelerate as quick.
 

DieAbetic

Member
Jan 16, 2014
168
16
Los Angeles
Thank you again for all the tips. Had a nice weekend at autocross school and getting some good times. Definitely agree on the early brake, release, and then punch it when lined up. I really need to get new tires and a front sway bar.

I'm tempted to get the RE71-Rs, but I also know the new Rival S 1.5s are very popular this year. They only come in 215/45 R16s - do you think that will fit the car?

I've also seen recommended on some posts here to get these pads: Carbotech AX6 Brake Pads LOTUS ELISE

Let me know what you think. Cheers!
 

Oricle

Member
Jul 12, 2010
61
57
Thank you again for all the tips. Had a nice weekend at autocross school and getting some good times. Definitely agree on the early brake, release, and then punch it when lined up. I really need to get new tires and a front sway bar.

I'm tempted to get the RE71-Rs, but I also know the new Rival S 1.5s are very popular this year. They only come in 215/45 R16s - do you think that will fit the car?

I've also seen recommended on some posts here to get these pads: Carbotech AX6 Brake Pads LOTUS ELISE

Let me know what you think. Cheers!

Good to hear you're getting some seat time.

Tires make the most difference, hands down. I'd probably stay away from the 215s, they are just too wide for the skinny wheels even though the compound is slightly quicker.

We went with the EBC pads because they were cheap and we weren't sure how competitive the car would be. Now that we have a setup that is doing well locally, I plan to change out to the AX6's in the rear in an effort to move the brake bias rearward.

Front sway would be the last mod i'd do to the car. I feel it's the highest cost to performance gain. You can make the car plenty quick without it.
 
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Oricle

Member
Jul 12, 2010
61
57
I've never done autox but have raced Willow Springs - Streets and Big Willow, and 3 days at Laguna Seca. It's fun but scary putting a valuable car into some of those turns.

Agreed, I've done 2 of the early Refuel races at Laguna Seca in the Roadster. Had an off track experience on turn 3, and an unexpected power oversteer on 11 which sent me towards the pit wall. That was about the time I decided AutoX was the better sport for the Roadster, and if I wanted to do track days id use my old Miata instead.
 

DieAbetic

Member
Jan 16, 2014
168
16
Los Angeles
I've never done autox but have raced Willow Springs - Streets and Big Willow, and 3 days at Laguna Seca. It's fun but scary putting a valuable car into some of those turns.

Yeah I freaked out a little bit on my first spin. And I'm nervous about PEM/Battery already, but oh well.

Good to hear you're getting some seat time.

Tires make the most difference, hands down. I'd probably stay away from the 215s, they are just too wide for the skinny wheels even though the compound is slightly quicker.

We went with the EBC pads because they were cheap and we weren't sure how competitive the car would be. Now that we have a setup that is doing well locally, I plan to change out to the AX6's in the rear in an effort to move the brake bias rearward.

Front sway would be the last mod i'd do to the car. I feel it's the highest cost to performance gain. You can make the car plenty quick without it.

Ok I'll stick with your 205 recommendations and the RE71Rs. AX6s in the back - are you going to keep EBCs up front?

Agreed, I've done 2 of the early Refuel races at Laguna Seca in the Roadster. Had an off track experience on turn 3, and an unexpected power oversteer on 11 which sent me towards the pit wall. That was about the time I decided AutoX was the better sport for the Roadster, and if I wanted to do track days id use my old Miata instead.

I sold my 2004 MazdaSpeed Miata after buying this Roadster... but I still miss it. Those are fun cars, and E-Street is a huge class with lots of competition. I have a lot of friends still in E-Street, so I can always drive their Miatas and MR2s

Thanks all for the advice!
 
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Oricle

Member
Jul 12, 2010
61
57
Are you running the 205/45/16 fronts on the stock 6" wide rims?

Yes. The rules for Street class do not allow changing the width of the wheels. Note, this is an autocross only setup, and Bridgestone does not recommend using the RE71-R in that size on a wheel narrower than 6.5"
 

Oricle

Member
Jul 12, 2010
61
57
Finally got a chance to AutoX the Roadster again this weekend, and after racing my Miata most of the year the shortcomings of the Roadster braking system were very apparent to me. Once the second step of ABS engages the Roadster does not want to stop quickly, so I tried a few runs with the ABS disabled (pulled the 10A #1 fuse next to the glove compartment). My conclusions from that experiment are the car is difficult to drive fast without ABS. Its been several years since I AutoX'd a car without ABS, so my threshold braking is a bit rusty, so I never became fully comfortable enough to be on full attack. Front end lockup came quick, especially when there is some side load on the car, and the car doesn't communicate lockup well so its difficult to feel that threshold.

TL;DR the ABS system is not ideal, but the car is probably quicker through most corses with it enabled. I stick with my original advise, a slow enough initial brake application to allow weight transfer to the noise, and try to stay at the threshold just before ABS activation.
 

Oricle

Member
Jul 12, 2010
61
57
I made a few changes to the car this weekend, some good, some not so good.

I changed from a standard wheel to the performance forged wheel to shave some unsprung rotational weight. The performance difference is negligible, but every little bit of weight removed helps.

I decided to try a more basic brake pad in the front in an effort to shift the brake bias more rearward. We have been using the EBC Yellows all around for the past few seasons (and have been happy with the stopping consistency throughout the day), but have been running into issues with the ABS system being too disruptive during runs. I installed EBC Red pads in the front and am happy with the change so far. I feel more confident with quicker applications of the brake now, though a soft initial brake application (waiting for weight to transfer to the front) is still the best way to slow the car.

Between events on Saturday and Sunday (similar course run in reverse) I decided to try more negative camber in the rear in an effort to increase high speed transitional stability. I went full negative in the rear (no shims) and found high speed stability to be similar but low speed rotation suffered greatly. In an effort to get that rotation back I stepped up the damping in the rear between runs shocks till they were maxed at 10. It helped marginally but by the end of the day I was not happy with the amount of push exiting slower corners. With the previous setup the car would rotate well with a lift off, or light brush of the brake. Before the next event i'll add one shim and play with the damping again to see if I can find a balance of low speed rotation while keeping the car more stable during high speed slaloms.
 
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Oricle

Member
Jul 12, 2010
61
57
Race weekend update: I added one camber shim to the rear to get rid of the understeer from running zero rear shims. We ran at a different (smaller) venue so it's hard to tell how much it helped with rotation, but the car felt pretty good (I ended day one 2nd in PAX, and day two 1st in PAX and 1st in raw time :)). Rear dampers were set to 8 (I think) with the single "thin" shim in the rear. The weather was pretty cool, high 60s to low 70s, so we decided to try some runs in Sport Mode. The power and throttle response benefits are pretty obvious while on course, but as expected the car can't keep cool for long. Thermal management is a whole nether aspect of trying to race a Roadster competitively. If you live in a cooler climate and only have a single driver, you could probably do a whole autox day in Sport Mode and be quicker.

The previous race weekend was in hot weather and we ran into overheating issues. Debug warning ID:1463 HVAC: Compressor OverTemp. I'll have to take apart some stuff in the front to find the compressor and figure out a way to cool it with a battery powered leaf blower, since we can't make any modifications for the "stock" class. If anyone has an HVAC schematic or advise on cooling, im all ears.
 
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ML Auto

Member
Mar 8, 2014
751
791
SW Florida
I have only seen the compressor overtemp warning when the A/C refrigerant is low or overfilled. When operating properly, the low side refrigerant return into the compressor is fairly cold, and helps to cool the compressor. I'm curious why the A/C was on at all. If the battery got warm and requested cool down mode, that only takes a few minutes and shouldn't have overheated the compressor. If you are keeping the cabin cool, you should turn it off during a run to allow max power to the PEM.

Check out this post if you need to cool down the battery between runs.
Manual battery cooldown mod - a cure for the Roadsters insomnia

I upgraded both my rear cooling fans (dual fan setup) with higher CFM units, so I don't have cooling problems unless the temps get into the mid 90s, and then the PEM goes red. I use performance mode exclusively.

I set my rear camber to -1 degree not for the understeer, but to get more traction during acceleration. When I had it at -3 degrees, I could overpower the tires at almost every exit. It's a little tail happy, and I have spun more than once. But a lot more fun.

I runs slicks and 4 piston brakes on all four corners (ABS off), so my setup wouldn't apply to your class.
 
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Oricle

Member
Jul 12, 2010
61
57
I have only seen the compressor overtemp warning when the A/C refrigerant is low or overfilled.
Do you know what the system pressure should be reading in the diagnostic menu? It only seems to happen on hot (90f+) days. The battery will get in the 43c range and can't cool down past that between runs. I'll look into the battery cooldown mod and try to pre-cool the battery between each run.

I upgraded both my rear cooling fans (dual fan setup) with higher CFM units, so I don't have cooling problems unless the temps get into the mid 90s
Which fans are you using? A bearing on one of our fans is going out (squealing occasionally) and will need to be replaced soon.

I set my rear camber to -1 degree not for the understeer, but to get more traction during acceleration. When I had it at -3 degrees, I could overpower the tires at almost every exit. It's a little tail happy, and I have spun more than once. But a lot more fun.
It's a difficult balance between rotation and putting power down. In my experience, slow applications of throttle work best on corner exit, anything quick and the inside rear spins.
 

tvuolo

Supporting Member
Supporting Member
Sep 8, 2013
292
105
Colorado
It's a difficult balance between rotation and putting power down. In my experience, slow applications of throttle work best on corner exit, anything quick and the inside rear spins.
I concur. I used to mash the pedal on the exit and it would ultimately cost time due to slipping. Now I've learned to restrain myself.

I've never had a problem with overheating at an autoX event. Not even close. Even when I took a class and we did a lot more driving than a typical autoX event. However mine is a 1.5 and I've never had heat issues off the track either.
 
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Oricle

Member
Jul 12, 2010
61
57
I've never had a problem with overheating at an autoX event. Not even close. Even when I took a class and we did a lot more driving than a typical autoX event. However mine is a 1.5 and I've never had heat issues off the track either.

I always assumed it was normal, but reading the forums I think we're the exception. We do run 2 drivers and typically race in 90f heat, so maybe we are on threshold of being too hot. I'm going to check the HVAC system pressure before the next event, according to Gruber it should be no higher than 175, and if I have time i'll wire up the pre-cooling mod MLAUTO posted.
 

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