Anti-roll bars Feb 4, 2006
Today we'll look at anti-roll bars (aka sway bars). The primary function of anti-roll bars is to combat the body roll produced as the suspension reacts to cornering forces. Body roll in and of itself is not a bad thing, but too much of it allows the suspension to venture into areas where the camber situation is grim or where the suspension bottoms out on one corner. Body roll can also exacerbate a roll steer geometry problem. Large anti-roll bars can prevent these things from happening, keeping our tire contact patches flat on the ground, and pointed mostly straight ahead.
There is an age-old debate about how much roll stiffness to provide via sway bars and how much via the springs. Sway bars have a huge advantage in that they can provide much larger amounts of roll stiffness than typically usable spring rates. To get the equivalent roll resistance of a typical sway bar, you'd need springs that were so stiff that you'd be losing tire grip on anything but a super-smooth surface. So we use a combination of both, but rely primarily on the anti-roll bars.
From our CSP setup we've found that the 1.125" hollow front bar from Racing Beat provides the necessary control to keep our chassis roll angle at about 2 degrees. Since the camber gain curve on the Miata's double a-arm suspension provides a favorable return of about 1 degree gained for every 2 degrees of roll, this means we'll only need about 1 to 1.5 degrees of static negative camber to keep our outside tires vertical in a turn. This also keeps the inside tires flatter than they might be with more static camber. This is tremendously important at the rear of the car as we fight to put the power down on corner exit.
Its important to note that with the reduced cornering forces of STS2's street tires vs CSP's wide, fat and sticky Hoosiers, we'll be generating less body roll. But that will be counteracted by the fact that the relatively soft street tires typically need more camber for optimal performance than the super-stiff R-compounds. Once again, this is just a starting point and we'll need to revisit and tune once the car comes together fully.
While we generate more of our roll resistance at the front of the car, we need to balance that in part with a rear bar. In addition to providing necessary roll resistance, a rear bar also helps us to balance the effects of weight transfer from front to rear. In short, we can alter the steady state balance of the car quite easily via the rear sway bar. In CSP, we ran in three different configurations: 1) no bar, 2) stock 12mm bar, and 3) Racing Beat 5/8" bar. Option 1 was used on very open courses on slippery surfaces to combat the natural oversteer tendencies of the car in those situations. Option 2 was used when either the course was tighter or the surface was much gripper. This was a very stable combination that allowed for early power application on corner exit and was our typical setup. Option 3 was rarely used, but was ideal for tight courses on grippy concrete.
While sizing the bars is important, mounting them for optimal performance is critical. Particular attention must be paid to removing any tendency for bind. This is especially important when urethane frame mount bushings are used. These typically are sized too tight. In almost every off-the-shelf aftermarket application I've ever seen, these required some modification to facilitate smooth movement. Lubing the inside of the bushing will provide some temporary relief, but under pressure, the lube will just be forced out over a very short period of time. Once that happens, the bar will act a lot stiffer than it is or it will be erratic. It will also start to fatigue the frame attaching hardware or the frame itself. It is common to see either the saddle bracket or frame extension on a Miata cracking from improper front bar installation.
To fix this problem, there are two easy solutions. One is to grind away some of the material from the flat outside part of the D_shaped bushing. Alternatively, you can put a washer or two under the saddle mount to shim it up. I prefer the former method. Ultimately, you are looking to be able to smoothly move the bar arms up and down when the end links are disconnected.
End links are also critical to proper sway bar performance. Stock rubber bushings provide a delay or offset in the action of the bar in exchange for less road vibration. Urethane link bushings are a better alternative, as they reduce this offset effect, but the best performance is provided by spherical rod ends. These remove all compliance so that the bar is always in action. 1999 and newer Miatas come from the factory with a similar setup and it can be emulated on the earlier models as seen in the pictures. At the front of the car we have merely screwed together a pair of male/female rod ends to provide the desired length. At the rear, we need a longer end, so we have screwed a pair of male ends into a coupler purchased at a local hardware store.
Rod ends vary tremendously in quality and you do get what you pay for. Teflon linings will keep road dirt out of the joint, which in turn will reduce wear. Cheap rod ends will typically start their tell-tale clicking sounds after just a few months of use. Of course, if you are willing to replace them frequently, go for it. We have good bearings at the front of the car and cheap ones at the back. It just worked out that way.
In addition to removing compliance, end links can also provide needed adjustability. This is important for two reasons. The first is to remove any pre-load from the bar when the car is in a neutral state (at rest, with driver). The second purpose is to compensate for lowering of the car and larger diameter bars. In the front of the Miata, use of standard length end links will typically place the large aftermarket sway bar in contact with the upper control arm. In addition to nasty handling effects, this puts tremendous stress on those frame mounts again. You should remove the spring, connect one end of the sway bar, and move the suspension through its entire travel to verify no contact. You also want to be sure that the rod ends do not move into a state of misalignment where they bind against their mounts.
Next up is a report on some tire testing we did recently.
Crunch Time! Mar 5, 2006
Its been awhile since the last installment for two reasons. First, we took a vacation/racing road trip to Florida to compete in the Ft Myers National Tour and also the two-day Florida Special Tour held the week prior. We also found time to visit Mickey, explore the Everglades, and visit relatives at the beach. The second reason is the subject of this installment, which I am writing from the road to California, with an STS2 Miata in tow! Yes, we have achieved our stretch goal of making it to the first Pro Solo of the year, and will debut the car at the San Diego National Tour. But, I am getting ahead of myself.
When we first started this project, it seemed very doable to get the car ready in time but everything hinged on the motor. Our partners at Applied Racing Technology have been very busy in this pre-season period building motors for Spec Miata racers and we were right in the middle of that bunch. These motors take many iterations of handwork, assembly, and measurement. As such, it can be difficult to predict finish times. Prior to leaving for Florida, we informed ART that if we were to take the car to CA, we'd need the motor in our hands by Monday, February 20. I checked back on the return trip a couple weeks later and sure enough, it would be done.
So here we were, less than one week from the time we'd be leaving for CA. Build up a race car in a week? Been there, done that. No problem! And thus starts another most excellent adventure...
A call goes out to the usual suspects, veterans of the "Scrappy-build" STS Civic adventure from last Fall. Several key players are available, albeit at disparate times since the importance of this build is not quite as high as last year's pre-nats situation. Special thanks go out to Steve Hudson (of the infamous Hudson's Storage, Chop Shop & Wedding Chapel), Zack Barnes and Drew Vanderploeg for their assistance and camraderie.
As Tuesday morning dawns, we are rolling back into Austin. Another call to ART reveals that the motor is close, but will be at least one more day. We take the opportunity to visit the shop and take some pics of the final assembly stages, but we leave the Civic on the trailer as a back-up plan. The rest of the day is spent working on the rear end assembly, swapping out the open differential for the viscous LSD unit. It's a very straightforward procedure, with the exception of setting the pre-load. The latter requires a dial indicator, calipers, and a deft touch. We've done one of these before, but we will have ART check our work to be sure.
Drew comes by on Wednesday and work begins in earnest. The motor is due late today, so we begin to unearth the car. As the pictorial reveals, leaving a disassembled car in storage for several years can turn it into quite the mess. All manner of stuff finds its way inside of, underneath, and on top of the chassis instead of nicely organized in bins on shelves. Some of it is just plain comical, most notably a huge tow-tube for boating and a stuffed Sponge Bob! Oh my...
Much of the day is spent moving everything from the one side of the garage to the other in which my daily driver usually sits. After removing enough stuff to actually get to the car we remove the TEC3 engine management system we used in CSP and replace it with the stock ECU. Though it's a bit of extra weight, we leave the TEC3 wiring harness in there since it goes through the firewall and cannot be removed easily. It is coiled up on both ends and stored out of harm's way. Bad news then comes in the form of a call from ART. No motor today, but definitely tomorrow morning. Damn! So instead we spend some quality time in the engine bay cleaning and prepping for the new powerplant and then call it a day.
Thursday morning bright and early I am at ART and there it is! All together, sealed up, and ready to go. Woo-hoo! We load up quickly and I am on my way. And almost immediately, the issues start. Here's the "clutch story"...
Back when I competed with this car in the Stock category six years ago I had to replace the clutch and found out that Mazda had superceded the part at some point and the new clutches were a pound lighter than the originals. I also noted that the clutch was made by Daiken (now owned by Exedy) and that it was the same as what could be purchased from various parts stores in town. Given that, I had the guys at ART source one locally for me. When I opened it up at the house, though, I weighed it and found that it was the heavier version. One pound may not seem like a lot but it is flywheel-speed rotational weight which magnifies its effect on acceleration. Trips to parts stores yielded nothing so I checked with the local Mazda dealers and found that they no longer carried the original Mazda parts in stock (no surprise there). But they instead kept Mazda's line of "Value Parts". Hmmm... Trips to two dealers with fish scale in hand verified that these parts were the desired lighter ones. And they matched the original Mazda part exactly! Bingo!
The crew starts to arrive and we get down to it. First the clutch and flywheel go on, then the tranny is joined up and miscellaneous engine parts go on. Of course, finding some of these parts is always exciting since they been stored in various boxes above the garage for several years, or shoved in a corner somewhere. And Lord knows where the attaching bolts are! Much time is lost on search missions.
Progress is steady now as we move through the install procedure as outlined in the service manual. The motor/tranny are hoisted up and carefully placed into the engine bay and attached. Various hoses and wires are then connected, radiator goes in, sway bar, shifter, clutch slave, etc. Four major snags show up. One is that we do not have the intake manifold bolts/nuts, so our hopes of firing up the motor that evening are dashed. We also don't have an original O2 sensor (long since replaced by the four wire TEC3 unit). Another is that the clutch slave has frozen from the long time off. The latter problem is solved via careful application of a large c-clamp. The final issue is that I had modified the accelerator cable to work with the TWM throttle body setup I used in CSP trim and it would no longer work for a stock motor. We call it a night with the drivetrain now neatly in the car, but much still left to do.
Friday morning is spent running around town to collect missing parts. First a trip to ART yields some intake bolts and an O2 sensor, and then a trip out to a local wrecking yard nets a throttle cable and a set of driver's seat rails. The ST seat rules are more restrictive than those in CSP and my super-light kart seats would have to go. For now the plan is to use a set of stock seats, and later get something lighter that has a full-sized back and weighs enough to meet the ST rules.
That afternoon, the intake manifold goes on and Steve and I tackle the Chinese puzzle of trying to figure out how the OE air intake system goes on the car. Without pictures/diagrams for reference, its quite frustrating! And the service manual is useless. The same can be said for replacement of the accelerator cable. Hey, now would be a good time to pull out that driver's seat! Good thing no one had a camera to record the contorted position that must be assumed under the dash to get the magic clip off that retains the cable to the firewall! Drew then calls and is on his way over. We divert him to a parts run for fluids (oil, MTL and coolant).
After dinner (did I mention that Ann cooked us all dinner each night?), we finish the remaining items on the motor and then realize that the gasoline in the tank has been sitting for three years. Yuck. Not what you want going through your freshly cleaned and blueprinted injectors. Its Steve's turn for a parts run, this one for a few gallons of fresh high-test. The powerplant frame is now connected to the rear end assembly and the stock exhaust downpipe and cat are installed. Well almost. No nuts. We have lots that have the correct size but wrong thread pitch. Looks like one more parts run and this time everyone looks at me! Off to Home Depot with cat in hand, arriving just as they are closing. I enter before they can close the front door and find what I need quickly. While I am gone the team replaces the passenger side kart seat with the OE seat. The attaching bolts are frozen, but a die grinder makes quick work of the offending party.
Back at the house, the moment of truth is fast approaching and the excitement level is rising. I install the cat and...hmmm...no muffler...what to do? This is a residential neighborhood, after all. And its now 9:30 pm. In a moment of inspiration I spy the old CSP glasspack "shortie" exhaust and figure out that it can be bolted on the back of the cat...sort of. The "angle of dangle" is not quite right, but it will suffice to at least fire up the motor.
Here we go...everyone stands back and I turn the key. After a few seconds of cranking to build fuel pressure it fires right up! ART's recommended break-in is to run above 2000 RPM for 20 minutes. I attempt to do this and have a hard time keeping it running steady at anything less than 3000 RPM. We shut it off and check everything. Gosh, the cam sensor is loose. Guess maybe we should set the ignition timing? Duh! So we do that and the symptom is a bit better, but the problem persists. At this point everything points to a vacuum leak causing a lean miss. I spy the make-shift "PCV valve substitute" that a certain someone fabbed when no actual valve could be located, but was assured over and over that it would work fine. We try again and just keep it above 3000 to seat the rings. Its now late and we are reminded forcefully by the head of the household that we are disturbing the neighbors, so we call it a night. I have a hard time sleeping while I ponder the surging problem.
Saturday morning I make a parts run to get a real PCV valve, and also visit Steve's extensive used Miata parts inventory to get some more missing odds and ends required to make the car ST legal. I also pull the original stock exhaust down from the attic and install it to reduce the "neighborhood nuisance" factor. The PCV valve cures the surging and the motor now is purring like a kitten. In fact, it is noticeably smoother than a "normal" Miata motor. That "parts-bin" balancing really works!
Steve comes over and helps me install the hood and put wheels/tires on it. The car now sits on its own weight for the first time in three years and we anxiously prepare for the maiden voyage. As I back out of the driveway I hear some nasty popping/clunking sounds from the rear of the car. Ooops! Pull back in and look around, but nothing seems to be loose or amiss so we try again. I go up to a cul-de-sac and do some slow turns and hear ridiculously loud noises coming from the diff. Ouch! Back to the garage. Its now mid-afternoon and we are really wanting to autocross the car the next day for a shakedown. Our plan had been to use the clutch-style LSD for the regional event and run in CSP, using Monday to build-up and install the ST-legal viscous unit. Now there was no choice, the VLSD install would need to move up two days.
A quick call to Ed at ART reveals that he has come in to work on Saturday so I take the diff down to him to verify my measurements. For setting diff backlash, Ed has some custom tools and a very specific procedure he has developed over the many years as a Mazda Service Tech and racer. He does a lot of it by feel. Ed verifies that I was close, makes a small adjustment, and reminds me to check the torque on the saddle bolts when I get home. Back home, I do so, but also succeed in pulling the diff right out of the vise dropping it three feet down to the concrete floor!!! Arggggghhhh!! Miraculously, there appears to be no damage, not that I could have done anything about it at this point anyway. So I install the differential into the rear end housing.
The next step is to replace the differential mount bushings with the harder rubber ones from Mazdaspeed. Following factory procedure, we drill holes through the old ones to remove pressure and try to hammer them out. No dice. Out comes the grinder again and we grind away some of the metal where the two halves come together and then can easily remove them. Next, we use a trick that the ART guys told us about, and that is to use a hose clamp on the new bushing to hold the two halves together while they are hammered into place. This works pretty well on the first one and we have it together in short order. But the second one seems slightly oblong and does not seem to want to go into the hole. Since the differential housing is aluminum, there is trepidation towards hammering too hard. An urgent call goes out to another racer friend (Denny Feigenspan) who owns a press, I plead my case, drive over and he helps me press the other one in. It is now 8 pm and I spend the next 2.5 hours removing the offending rear end and replacing it with the new viscous-equipped one. It is now 10:30 and I once again take the car out for its maiden voyage. This time there are no issues at all and I drive it around town for 30 minutes. Success! We shall race tomorrow!
Sunday morning I awake from a dead sleep dreading changing tires and loading up the car on the trailer. Instead I decide to just drive the car on the old skinny tires the 100 miles to the event, race and drive back. Just like the good old days. Of course, the car does not have a current inspection sticker or insurance yet so getting stopped by the gendarmes would be a bad thing.
The trip over is fun in its own way as I rediscover the fun of a Miata as a street car. At the event, it performs well (i.e. nothing falls off of it and it doesn't blow up) and we put down some good times. Halfway home I suddenly remember that I failed to tighten the bolts that attach the rear upper control arms! Of course, this realization occurs along a two-lane country road that I am traveling at 70 MPH and there is no shoulder and no place to pull over. Finally, a gas station appears and I check out the bolts. Yes, they are loose, but have not backed off at all from the finger tight install I did. Since I have no tools with me anyway, I simply press on.
Most of Monday is spent fabbing up a muffler setup so that the car will pass sound control at the San Diego Tour. The Supertrapp on the Civic worked for it, so I start by stealing that piece. Next, I cut the flange off of an old failed Miata cat and proceed to enlarge and reshape the hole, and drill out the mounting studs. The exhaust has to make a bend right at this joint so several hours are spent grinding and test-fitting until I get it just right. A two-inch piece of leftover pipe from a previous project is just long enough to do the job so I weld it all up. This results in a sporty exhaust note that can be easily tuned to meet sound limits, or uncorked for times when there are none.
At this point, the car still has an entirely stock intake tract and exhaust, except for the muffler. Luckily, part of this project will involve doing some future dyno comparisons of popular intake/exhaust parts. A quick e-mail to Per Schroeder at GRM and he is on the task. Several hours later he has arranged to have a Racing Beat intake, header and plug wires shipped to meet me in CA. Looks like we'll be doing some parking lot installs!
With the car now totally presentable, its time to make it totally legal. Much of Tuesday is allocated to reinstalling the original soft-top, seat belts, brake proportioning valve and bleeding out the brake system. Ann goes off to see Vitek Boruvka at Axware Systems to have some "2's" made to match our "STS" letters and numbers. Right around dinner time we are done and packing begins. Wednesday morning, we are on the road with our newly built STS2 Miata in tow.
While crazy at times, this sort of adventure with racer friends is what draws me to this sport. Its amazing what can be accomplished when you combine the wide-ranging talents of a group of racers. Everyone has their area of expertise, and all are dedicated to the goal however ridiculous it may be. In this case, we got a motor on a Thursday, and put a race car around it in time to race it on a Sunday. Two more days, and it's a nationally competitive, legal race car. Pretty freakin' amazing.
Next installment will be the results from the debut in CA.
Showtime! Mar 6, 2006
As discussed last time, the car was put together in a hurry to meet our stretch goal of a debut at the San Diego National Tour and the Fontana Pro Solo. With that goal made, it was time to get a baseline on national level performance. We were still running with a totally stock intake and exhaust system with the exception of a Supertrapp muffler but we had parts meeting us in San Diego from Racing Beat. The good news is that they arrived at my daughter's place in SD intact. The bad news is that she twice failed to bring them out to the site before Saturday so we had to run it that way for the first day. Kids! What are ya gonna do?
Friday at the track was spent getting a few runs in on the practice course. It was pretty tight and the surface was greasy, though, so little info could be gleaned from that other than the fact that our car was way too quiet and hardly moved the sound meter. We also spent some time getting the required series decals and the requisite partner logos on the car. After that, it was "wax on, wax off" in preparation for Saturday's competition debut.
With very little seat time in the car and a very narrow course, my first day competition runs were very tentative. For sure, the LSD was working, as pressing the throttle too quickly produced a nasty oversteer. Still, the car was pushing badly in sweepers, and even some transitional maneuvers. At the end of the day we were 8 tenths back sitting in second place.
That evening, we broke open the box of Racing Beat go-fast bits and installed both the beautiful stainless header and the intake system. The header install was very easy and everything matched up. Almost. The non-stock flange mounting nuts on our catalytic converter were too large to fit over the ridge in the header output flange, so we'd have to find some replacements. An hour's worth of parts store searching netted us a pair of "manifold nuts" which were perfect!
The intake install also went well, with just a little bracket bending required to avoid the adjuster on our aftermarket shock tops. Firing up the car with the new parts yielded a much throatier sound emanating from both intake and exhaust. A quick trip up and down an adjacent street and our butt dyno gave a resounding thumbs up to the newfound power. Throttle response was also very much improved. We'll be dyno testing these parts in the weeks to come to get real numbers on the improvements.
In addition to our newfound ponies, for Sunday's competition we made some shock adjustments to compensate for the pushiness of the car and to combat the LSD-induced oversteer (less front rebound, less rear compression). We also focused on being more aggressive driving the car and getting it to slide just a bit. The results showed the improvements as were right in thick of things now, leading the class right up until the very last run. In the end the first day leader moved back ahead (they were having their own troubles), and we stayed in second place. But the margin of victory had been cut to a measly .144 seconds. Not bad for a first outing. Still we were back away from STS and we should be beating that class.
One thing that needs immediate attention is our alignment. We still have the CSP low-camber settings on the car that worked so well on the short, wide, and stiff 13" Hoosier R-compounds. Unfortunately, this is not nearly enough camber for the comparatively mushy Falken street tires. We'll be addressing that to some degree this week before the Fontana Pro Solo. And the 12-run format of the Pro Solo will give us several chances to try things. Then later, we'll focus on it during a test session we have scheduled back in Texas in late March.
Next stop: Fontana.
Fontana Pro Solo Mar 13, 2006
Another quick update from CA...
In short, the Fontana Pro Solo was a miserable experience due to some of the worst weather I've seen at one of these events in years. Cold, rainy, and windy. Yuck.
When we arrived on Friday, it had already rained and practice starts were an exercise in futility. We did find that revving the motor to about 2700 RPM and then releasing the clutch in a deliberate manner would provide a zero-slip start, while minimizing bogging of the motor. Anything more than that and the tires would spin forever.
As for the competition itself, each day we ran in drying conditions and each day the second driver of our competitor's car put down the fastest times. In the end, we had fast time on one course, but finished second on total time by a solid half-second. While its rare that conditions improve that much between first and second drivers, this weekend it happened twice. Running in first group seems to make this more prevalent.
Due to the weather conditions, we did not change any of the alignment as we had planned to, instead softening the shock settings to full-soft for the slick surface. This worked reasonably well in the inclement conditions.
One more teething problem reared its ugly head in the slick conditions: brakes. The fronts are locking up horribly. We noticed a little bit of this in the dry at San Diego, but in the wet its ridiculous. A cursory inspection reveals some weird wear pattern on the rear rotors, so it may be a frozen caliper from sitting unused so long. Or maybe the aggressive pads I was using for CSP are just too much for the street tires. We'll mess with that one soon, too.
Brakes Mar 22, 2006
In our initial national competition outing in California, we noted a terrible braking issue. In the wet, the brakes were almost unusable since the fronts would lock up with very little pressure, and were difficult to modulate. This was also an issue in the dry, though not as severe.
A rainy Saturday at home gave us the perfect opportunity to ignore the yardwork and spend some quality time in the garage. The first thing to check out was wether or not our brakes were actually functioning as designed, and then we'd look into additional modifications to improve performance. Too often people dive straight into mods when, in fact, there is some fundamental maintenance problem.
So we pulled all four wheels and used hand pressure to move the calipers back and forth on the sliders. Some squeaking ensued. Hah! A possible problem due to drag. I guess that what happens when the car sits on jackstands for three years. Each brake assembly was then taken apart, caliper slides lubed, pad slides cleaned and lubed, and everything carefully reassembled with special attention paid to the pad springs and clips. Its also a good idea to work the pistons back and forth some to dislodge any dirt or rust that has gotten past the boot.
As we took apart the the final brake assembly (left rear), it all came apart in our hands! Turns out that the retaining tabs for the pad sliders had broken at some point and the sliders had relocated themselves in such a way as to keep the pads from functioning properly. In fact, the pads on this side looked very new in thickness, while those on the other side were half gone. Oops! I wonder how long that has been going on?
New clips and pad sliders were sourced from our good friend and DP Miata competitor Steve Hudson's large stash of take-off parts and everything was reassembled. Special care was taken at the rear to properly set the pre-load on the piston. This can be accessed by removing a plug at the rear of the caliper and inserting an allen wrench. The manual specs it at 1/3 of a turn from first contact. Don't go too tight or the brakes will operate by themselves when they get hot and everything expands! (Note: This same adjuster is used to pull the piston back to allow room for fresh pads. Never use a c-clamp for this purpose or you will ruin the caliper. Ask me how I know...)
Since it was still wet out, a quick test drive was in order. Hmmmm...much improved performance! And use of the e-brake gives very even side-to-side performance from the rear brakes. Well, right until the point where you lock them both up and the car goes sideways. Don't try this at home, kids!
Properly lubed up, adjusted and working correctly, the brakes were now much easier to modulate. But the fronts were still doing too much work compared to the rears. Time to attempt some mods to fix that.
Early Miatas have a two-stage proportioning valve that sends most of the brake pressure to the front when you exceed a moderate amount of pedal. There is a chart in the service manual which diagrams this. For the street, this is a Good Thing, since it causes any panic stops to lock-up the front wheels only, keeping the car from fishtailing. For racing, when exceeding moderate braking is common, its a disaster. In CSP, where brake proportioning valves are unlimited, we merely plumbed it out with a pair of brass flared unions. This is not legal in Street Touring, though, so we'll have to look elsewhere.
The other mod we had done for CSP, was installation of Carbotech's carbon-kelated pads in the 913 compound. This, combined with the prop valve removal, gave very balanced braking that was aggressive yet easy to modulate. In STS2 trim though, we transfer less weight forward because the real street tires grip way less than the short, fat Hoosiers. In fact, we probably generate less forward weight transfer now than the car did in Stock category trim way back when. We need to get the rears to do more work to deal with all the extra weight they now carry under braking.
Since we are limited in STS2 to Stock-legal brake mods, we can only alter the pads. Being the pack-rat that I am, I find the original pads that came on the car stuffed in a box in the attic above the garage. These are basic cheap no-name parts store organic pads. Using these in the front only will give even better modulation and provide less coefficient of friction relative to the rear Carbotech's. Installation is a breeze and in no time we are out testing again.
The very first stop is disappointing, but subsequent stops are very nice indeed! Mixing pads is a bit of a black art since the friction produced by each compound changes as the pad heats up. In our case, it is clear that the rears need a bit of temperature for them to give the the proper balance. In fact, we notice that the rears start to squeak when they get properly warmed up.
The next day was a regional event in San Antonio in mixed weather (wet morning, dry afternoon) so we double-entered to run in both conditions. In the wet the brakes were incredible once warmed up. Totally "night and day" compared to what we experienced in Fontana. In the dry, they were also much better balanced but now required a bit more pedal pressure. Nothing drastic, but not the lightning quick response we had before. Still, they were better balanced, easier to modulate, and similar in feel to the STS Civic we also drive.
One note on brake -warming: All too often we see people moving from grid to stage, surging along on and off the gas/brake to warm their brakes. This is much easier to accomplish by just applying constant pressure to the brake (left foot) and using the right foot to work the gas pedal against the brakes to move the car forward. You'll easily get more heat, and you'll won't risk the ire of the Safety Stewards or run into someone. In our case, since we are just looking for heat in the rear, we just set the parking brake up a couple of clicks and drive to the line.
So, now we have decent brakes again. In the future, we will likely try some other compound mixes to see if we can improve even more. We'll likely try the products from Hawk since they support Pro Solo. And those of you with ABS, we salute you!
Next up this week is a quick corner weight session and baseline alignment as we prepare for an all-out suspension dial-in session this weekend.