An Autocross Season- Part 7: Moultrie Test

Numbers Installed And Falkens Mounted

I was invited to the Pro-Solo Test down in Moultrie this past weekend. Moultrie is quite close to the site of this year’s Red Hills Tour, way down there in the South of Georgia.

Moultrie Courthouse

After the problems with the Pro-Solo system early last year the SCCA began a crash effort to fix the issues. A few events got cancelled, but an improved system was then fielded mid-year.

Raining On Thursday Arrival

What I didn’t know previously what that a significant effort has continued since then to further improve the system to make it even more reliable and easier to operate. So last weekend the SCCA ran a test in Moultrie on the concrete pad at Spence Field to shakedown the revised software and hardware implemented since the end of last year and prior to the first points Pro-Solo event in a few weeks in Florida. We did a lot of starts and runs over 3 days, testing single-course, dual-course and challenge modes multiple times.

Saturday The Surface Was Dry And Cold

The system worked really well as far as I could tell. I got something like 60 full runs and an additional 40 or so practice starts on Friday which began wet and slowly dried a bit as we went along. (This went a long way to minimize tire degradation as I learned to launch the car.) The Corvette was awesome the entire time. The clutch never overheated and stayed consistant for every run the entire weekend.

Just before I left I received a set of upper shock bushings made from polyurethane which will be installed with the Penskes when they get here. Some people may not realize that these are legal in Street class. They should make a slight improvement in shock response. The Ohlins I had on the C5 had no bushings at all… they fitted metal to metal at the upper end and transmitted a lot of additional noise into the cabin. The Konis mounted now re-use the stock rubber bushings. I have them cranked down pretty tight to limit lost motion.

Poly Upper Shock Bushings

The two very short courses were not quite identical and that was a good thing. In fact, I wish they had differed even more than they did for additional variety. Both had a tight section that rewarded excellent braking, car control and a good knowledge of the braking understeer point for the front end. These sections also rewarded narrow cars and better transient response.

Of course the drag start rewards power-to-weight and forward grip. I think the rear 305 Falkens did a pretty good job of putting the power down once I really tuned into the feeling and sound of incipient wheel spin and could control the application of torque. The Sunday morning session contained my fastest times on both sides and is shown below.

Results From One 10-Run, 16-Minute Session

In the picture above you have, from left to right on the top row, the clock time of the first run which happened to be from the left side, its sequential number in that session and that side, the total time of the run, the Reaction Time, and the time to travel the first 60 feet. Then you have the same data again for the first run on the right side. For those not familiar, the quickest left side time is added to the quickest right side for your total at a competitive event.

The sharp-eyed and clued-in may notice that the clock times look a little strange, i.e. they don’t all swap from side to side like normal as we cross-over behind the start, alternating side to side. This is true. After the second run, which was on the right, I pulled back into the right lane again to even up the lines of cars on both sides and ran my third run from the right side again. Later in the session I did the same thing but on the left side. This could never happen at a real event, but at this informal test things were laid back.

The red, crossed-thru time was a red light run, i.e. I left too early and crossed the start beam before it had turned green, which is 0.500 seconds after the last yellow light. I had been playing around a lot with my launch technique, but by this time I was getting reasonably consistent in the 0.6’s and 0.5’s.

The 60-foot times are a little slow with the best being in the mid 2.2’s. I attribute this partly to the cold conditions which limited grip. In warmer weather I’d hope to be running consistently low 2.1’s, but I’ll have to improve my launches some more to get there. Barry K. cut a few 2.0’s in his mid-engined C8. Donour S., owner of a Lotus Evora he’s taking to STU this year, was consistently in the 2.1’s and sometimes dipped into the 2.0’s. I expect he’ll cut some 1.9s this year in that mid-engined car that has over 60% of its weight on the rear tires similar to the C8. It’s not horsepower that nets good 60-foot times. The car has most of the energy it needs to get started well already present in the engine’s rotating mass. It’s grip and technique that make for good 60-foot times.

You can find a video of the last 8 of these 10 runs on Youtube here.

This concrete site is not big enough to have much in the way of fast sweepers and probably couldn’t hold a real Pro-Solo event, though it could host a single-course event nicely.

Loaded Up For Home

An Autocross Season- Part 6: B-Street Ratings

Some may know that I’ve been compiling a rating system for autocross cars for several years. It’s aimed primarily at A-Street and B-Street. Below is the list of BS cars for which I’ve run the numbers.

Fisher Autocross Speed Ratings- B-Street Cars

I calculate four individual Ratings which are then combined per the formula shown in the Total Rating box. First is Grip. This is very simple: weight of the car (with a 200lb driver) divided by the sum of one front and one rear rim width. So, for instance, it might be 3200 pounds divided by 9″ + 10″ which is 3200/19 = 168 pounds per inch of rim width.

Then I normalize all the resulting grip rating numbers for all the cars. This means I pick some car (originally the best one) and make its value equal to 100 and proportionally adjust all the others to suit. Of course, when it comes to grip, less weight per inch of rim is better, so it gets inverted.

You may be asking why there is no car in BS with a grip rating of 100. This is because the C6Z06 in AS got the 100. If you look at the list you can immediately see that none of these cars in BS comes close to the 100 Grip score of the C6Z06. Now you know the basic reason why the C6Z06 is so fast on an autocross course!

A rating value can be over 100. I typically don’t go back and re-normalize everything when a new car is better in some respect than the original car I set at 100. This means that the Total Rating is no longer strictly a 100 point scale. Maybe I’ll go back and change that.

I would love to be able to use center of gravity height in my rating system for evaluating Grip. Unfortunately, that’s not a number that is often published for most cars.

Once I have the individual Ratings, I create a combined Total Rating. Grip, Width and Thrust numbers are added in equally. Transient Response is weighted at only 50% compared to the other three. All of this, while based on numbers, is still, in the end, only a partially objective way of evaluating autocross speed. You will have to decide for yourself how accurate you think it is.

I show the individual Ratings for a reason: it allows you to combine them differently. If you think Grip is 25% more important than Thrust you can revise the total and get your own answer.

I recognize that there are many intangibles in autocross performance that can’t be put into such a system. Some subjective adjustments have already been made and are explained on the chart. For instance, it wasn’t until I autocrossed a 2019 Cayman GTS that I realized how detrimental turbo-lag can be even in a modern car with the latest-design variable-geometry turbo in certain types of autocross features. I penalize the M2C less than the M2 for turbo lag based on the faster-spooling system in the M2C which people have praised as significant over the original M2. In reality it’s very course dependent. In a course with nothing but standard corners linked by short straights turbo lag is almost a non-factor. This is because we do not require instant full torque at the apex of a standard corner. We only require a smaller amount of torque to be ramped up as we open the wheel. But in many linked features we can use instant torque for a very brief time. That’s when we get nothing, or worse than nothing, from a turbo engine.

For the Thrust rating I calculate the theoretical acceleration at peak torque in 2nd gear, unless otherwise noted. To do this I use the weight of the car plus 200 lbs for the driver, 88% of the manufacturer’s rated peak torque (to account for drivetrain losses), 2nd gear and final drive ratios and the rear tire diameter. The proper rear tire diameter is something I spend a lot of time figuring out. I don’t use what came on the car. I find what I think is the best (usually smallest diameter) wide, 200TW tire that’s legal to use on that car. I assume the owner will spend the money on custom wheels if necessary. This often has a significant effect on the ratings.

This Thrust rating is representative of the acceleration performance but clearly does not tell the whole story. Yes, it would be better to integrate the total acceleration from, say, 30 mph to 65 mph using dyno graphs. I simply don’t have the time to collect and process all that data so I leave it to others.

Width is a straight-up comparison using the manufacturer’s stated width, not counting mirrors. I do not go around measuring the actual width on the ground at the rear tires of cars at autocross events. I’d probably get run over.

The Transient Response rating is, well, it’s a little complicated. To my knowledge I’m the first to calculate such an estimated number from internet-available data. I received an inquiry from the SCCA as to how I do it. (I told them.) It’s clearly only an estimate of a very complicated property, but the key thing I came to understand is this: when a car begins the transition from going straight to turning it does not rotate about the center of gravity of the mass, i.e. it does not rotate about the middle of the car. Instead, the initial motion is a rotation about a point somewhere behind the rear bumper for almost all vehicles. Therefore, the initial resistance to that rotation is the inertia about that point, which is located at a percentage of the distance from the rear axle to the CG behind the real axle. Got that? So, I estimate the mass moment of inertia around that point. As the car transitions into the turn the center of rotation moves forward.

This means that the polar moment of inertia value, a property at the CG point and so often bandied about, is a poor gauge of Transient Response. Polar moment mostly tells you how fast the car rotates once already spinning, not how fast a car transitions. Even once fully into carving a turn the rate of rotation about the center of the car is low. A car only rotates once per full revolution around a driven circle, say, a 200 foot skidpad, which requires multiple seconds to negotiate. But the initial turn rate about the initial rotation point behind the rear bumper is very fast and substantially limited by the inertia around that point.

Also of next to no importance is the peak turn rate in degrees per second that a car eventually reaches at the end of the standard step-steer test, a mistake some people (Car and Driver, for one, in their Mid- vs Rear-Engine Debate in 2011) have made. You may notice that the 996, recently moved down from AS to BS, is the only car with a higher Transient Response rating than the Evora, which had previously been the 100 point standard, and which in turn has a higher rating than the Cayman. The Evora, while mid-engined like the Cayman, rates higher because it has more rear-weight bias than the Cayman. Lotus knew exactly what they were doing in designing a car that’s almost universally praised as better handling than the Cayman.

The 996 rates higher than the Evora because it has a shorter wheelbase (even shorter than the Cayman) and even more rearward weight bias, both of which tend to reduce the moment of inertia around the point of initial rotation. 911s have always been more “nimble” than Caymans in spite of having more weight and a higher polar moment of inertia. Car and Driver was unable to figure this out.

Silver Ghost, my C6Z51, is third on the Ratings list, a full point behind the M2C and half a point in front of the Supra. (Note that I think it requires about a two point difference to indicate a consistent advantage, so I think these cars are really very similar in autocross speed.) I’ve used the 305/30-19 Falken as the tire when calculating the Thrust Rating for Silver Ghost. If it turns out that it is possible to use an 18″ tire (ABS issues and availability of a properly small diameter front tire seemingly block its use) the Thrust rating will increase enough to vault the C6Z51 right up there with the M2C. Please note that these calculations necessarily assume that every car can employ every bit of torque produced by the engine at all times, whether or not they have an LSD, enough tire with enough weight on it or a sufficient suspension setup to actually do so. That assumption is clearly not always true.

I took a look at recent, same-day, same-equipment, dyno results comparing the 2022 Supra to the older ones. It’s clear that it has more peak power… significantly more, and in recent BMW fashion the car continues to be seriously underrated as compared to other manufacturers. However, the peak torque, which occurs at a very low RPM, is essentially unchanged. Boost is apparently increased only in the top half of the rev range. Therefore, the Thrust Rating for the 2022 model wouldn’t change much, if any.

If you have questions or want to know more details of how the Ratings are calculated leave me a comment and I’ll do my best to explain. As always, feel free to tell me where I’ve gone off the rails.

Silver Ghost With Her New Falkens

An Autocross Season- Part 5: Silver Ghost Pulls Hard

Took Silver Ghost out with the Vbox GPS data collector and performed a pull in 2nd gear now that the slightly smaller race tires (26.3” diameter) are on and she’s burned down to 1/4 gas. Results are shown below.

Vbox GPS Data-Acceleration from 30mph to 71mph In 2nd Gear

This plot is from 30mph up to fuel cut at 71. The peak (at the cursor location) is 0.575G.

This compares closely to two friends, one who has a C6Z06 and one a C7 Grandsport. Recently the Z06 peaked at 0.62G with a 315/30-18 rear tire (25.6″ dia.) in similarly cool conditions. In theory, given the tires employed, Silver Ghost should be matching his peak acceleration. But it isn’t the case.

The C7 Grandsport was wearing an all-season 335/25-20 run-flat rear tire that is 26.6” diameter. He also recorded a peak of 0.62G. In theory he should be beating the Z06 by a good margin, but that isn’t the case either! No doubt, he’ll pull harder when he gets some shorter Hoosiers on there for SSR.

I suspect the LS7 motor in the Z06 is a bit underrated. Also, the measuring equipment used was not all the same, not at the same location, time of day, etc.

The real test will be how well Sliver Ghost puts down power on the autocross course coming off a slow corner. That’s when these Falken 305s and my suspension tuning need to earn their pay. First chance to really evaluate it will be our Test & Tune in three weeks.

I took Silver Ghost on a little trip yesterday, a mix of country and highway roads… no interstate, following a buddy in his Porsche 993. This was his favorite test-drive route. At one point we were detoured around a closed bridge onto a narrow, gravely country road with half our lane washed away in places. That was a little tricky when meeting on-coming traffic. Averaged 25mpg.

As always, let me know if there are things you want to hear about that I haven’t mentioned.

An Autocross Season- Part 4: National Event Plans

Silver Ghost

I plan to compete in six national events with the Silver Ghost C6 in B-Street this year, not counting Nationals themselves and regional events. Three Solo Tours and three Pro-Solos. The first is in less than a month.

Planned National Event Schedule for Silver Ghost

By the Florida Pro, which is a single-course Pro-Solo event, I plan to have a few more things done to the car. I’ll sand the brake disks and install some Carbotec street pads, my preferred autocross pad. I’ll change the diff fluid, trans fluid and engine oil, putting in my favorites: Miller’s Nano in the diff, AMSOIL in the trans and Redline in the engine. I’ve already installed Brisk Racing side electrode-type spark plugs which were proven in the C5 to add a little horsepower and torque in the mid-range. (I’ll be happy to provide details on these items if you ask.)

The Florida Pro registration is filling out nicely with 115 of the 125 spaces taken. There’s only one other person registered in BS, which is disappointing but not surprising. He’s a fast driver in a 2014 Boxster. If they set the course up like last year with a fairly long drag-race start I should be a few tenths in the lead by the first braking point, assuming it’s dry. If it’s wet, I could be in trouble!

Oh yeah, my numbers came in. I got them from autocrossdigits.com

An Autocross Season-Part 3: Car Setup

The formula for a full-tilt, max-attack assault on a Street class in a Corvette is pretty well known. Modifications are severely limited by the rules. The four key areas are 1) a stiffer front sway bar to improve transient response and limit camber loss in roll, 2) an alignment with increased tire static negative camber to produce more grip at the cornering limit, 3) sticky, autocross-specific, fast-heating, quick-responding, fast-wearing, too-fat-for-the-rims tires to produce more longitudinal and lateral grip from the first turn, and 4) pimp, double-adjustable shock absorbers, properly valved for autocross to produce the least amount of tire patch force variation considering the bumpy surfaces we race on and, specific to Street class, to act dynamically as springs to supplement the insufficient spring rates provided by the manufacturer. The first three mods are relatively simple. The last one not so much.

One other modification that I initially assumed would be required is a second set of custom, lighter wheels, 18″ diameter all around, mainly to allow a shorter rear tire to improve the gear ratio for better acceleration in 2nd gear. I discovered an issue with this plan, however, which I’ll discuss further down.

I started with Sam Strano’s 1-5/16″ diameter front sway bar with adjustable end-links. It has a choice of two holes in each end, which give you three possible levels of stiffness: both first holes, one first hole and one second hole, and both second holes. I bolted it up with the stiffest setting to begin with and it feels great so far on the street.

C6 Front Wheel-well

In the picture above the yellow number 1 arrow is pointing to the new front sway bar. At the very end of the bar you can see the unused hole which would produce reduced roll stiffness if the drop-link were located there. Magenta arrow 2 points to the adjustable-length drop-link. At the bottom end you can see some of its spherical ball-joint. Cyan arrow 3 points to the steering tie-rod where the flats are formed that you can count as you turn it to adjust toe.

Next I increased the negative camber at all four corners to the max and reset the toe-in to near zero at the front and 1/4″ (total) at the rear. I was able to do this in my own garage and got about 3 degrees in front and around 1.75 degrees in the rear. (These are approximate as my camber gage doesn’t fit these wheels very well.)

C6 Camber Eccentric- Lower Front Control Arm

The car had a stock alignment not long ago and I found paint marks that indicated nothing had slipped, so I assumed things were still straight and even from side to side. See the red paint marks in the picture above. The black arrow indicates the direction the lower control arm moves when increasing camber. The eccentric rotated about 90 degrees to get to the place where it wouldn’t go any farther.

Going for max camber at all four corners is simple and straight-forward on the C6. Turn the eccentrics to the stops. You get what you get and don’t worry if one side has a little more than the other. It will happen. You won’t notice. You do want all that Chevy gave you.

Then I use toe plates to get the wheels pointed back straight. Going from half a degree of negative camber to around 3 degrees in the front produces a massive amount of toe-in as a by-product. I counted the flats when turning the 6-sided toe-link, putting the same changes into both sides, until the total toe-in was near zero. Same for the rear, except it got massive toe-out from the camber change. At some point I’ll take it to Brad at Clem Tire and have it set more precisely, once I decide on what I want after some testing.

Using Toe Plates To Measure Toe Angle

By the way, you don’t have to worry about the caster angle in the front. It will go where it’s gonna go. Let it be, let it be.

For tires I went with Falken RT-660 200TW, 275/35-18 in the front on the stock 8.5″ wide rim and 305/30-19 on the stock 10″ wide rim in the rear. They were here within a few days from Tirerack, but I waited until the weather warmed up a little before having them mounted. Luke at Wheelfixit was kind enough to store them in the middle of his heated shop, in line with the heater output, to make sure they were toasty prior to mounting.

Front And Rear Tire Fit

The 305s in the rear are 26.3″ diameter which is a little shorter than the stock 26.9″ tire. The car goes about 72mph in 2nd with the 305, which is still a little too fast. 69-70mph is considered more perfect.* I could have gone with a 315, but I wasn’t able to positively conclude it would fit without rubbing given the narrow body of the base C6. (It’s appears to be a close thing.) The standard lower rim range for both of these tires is 10.5″ so pinching them onto a 10″ rim is not particularly radical. The 315 may be an option for the future if I’m having trouble putting power down. It’s only 0.2″ bigger in diameter so it won’t hurt the gearing very much though that’s moving in the wrong direction.

On the other hand, there’s a 315/30 in 18″ which is only 25.5″ in diameter, producing a significant gearing and unsprung weight improvement but will require a custom rim. My plan was to see how the 305 does early in the season and then make the decision whether to obtain a new set of wheels. Then I stumbled into a glitch in the matrix.

The glitch is that there may be no suitable front tire to match to this 315/30-18 rear. I have it on good authority that the front tires needs to be at least 1% smaller diameter than the rears in order to not upset the antilock brake system. (Forget about traction control and stability control… those will be turned off anyway.) The 275/35-18 is slightly taller than the 315/30-18 rear, so it’s out, and the 265/35-18, which would otherwise probably be acceptable, is 25.4″ diameter, which is only 0.4% smaller, less than the supposedly necessary 1%. Concurrently I found a confirming report from a well-known tuner with the same year Corvette who mounted 4 tires of identical size on 4 identical wheels and the ABS tried to kill him and his wife on the track by locking up the rear tires anytime more than 1G of braking was attempted. Will that happen at autocross speeds with a front tire 0.4% smaller than the rear? Dunno, but I hesitate to risk thousands on custom wheels that will be difficult to resell only to have that sort of problem.

With my C5 the front to rear tire size delta was not an issue. I raced for years with the front tire larger in diameter than the rear. As long as the other nannies were turned off the ABS had no issue. That was a different Bosch system as compared to the later Delphi.

So, I’ll see how the 305s do. This car accelerates so ferociously in 2nd gear I really don’t know if a smaller rear tire will even be useful. It could just make the car harder to drive for this old man.

Now we come to the shocks. At present I’ve mounted my old Koni 3013s. These are pretty good performing rebound-adjustable shocks, though the damping curve shapes and force values are not much like what I am specifying to Penske for the 8300-series double-adjustables I’ve ordered.

Yellow Koni 3013 Front Shock Absorber

So, what exact shock characteristics am I specifying? Um, sorry, but I’m not telling.

If I have any competitive advantage over my competition it may be all the research I’ve done into shock absorbers over the last few years. You can find much of it published elsewhere in this blog.

I will describe the process, however. Just not the exact choices I made.

Step 1: The first thing I did when I got the new car was measure the motion ratios for the shocks and the leaf springs. I found a couple of people on-line that had done the measurements. They didn’t agree very closely and they didn’t provide enough information to determine if one or the other had measured correctly or incorrectly. I had to do it myself. If the MRs are not right you might as well buy an off-the-shelf fitment from one of the usual suspects and twiddle with the knobs.

Step 2: The next thing to do, once I had the tires mounted (and the tire/wheel combos weighed), the new FSB in place and the Konis installed, was to weigh the car on a set of scales (borrowed from Tom at the Little Raceshop of Horrors) and get the corner weights. The car weighs 3206lbs with 3/8 fuel and the targa top in place and has 52% of that weight on the front. The cross-weights are quite good and get better with a nice plump driver in the seat.

Step 3: Get numbers for front and rear unsprung weights. These weights are going to be subtracted from the corner weights in the on-line calculator, which mostly uses the front and rear sprung weights in order to calculate system natural frequencies, which is how the suspension stiffness of a car is actually measured. About half of the unsprung weight is simply the wheel/tire combo, so that always gives you a good, easily measured, starting point. I was able to find discreet weights for things like brake disks, calipers, hubs and suspension arms, etc. and come up with pretty good numbers without having to disassemble and weigh each piece of the suspension myself. That’s one nice advantage of operating a car popular with enthusiasts. Some of this work has already been done and is available on the internet.

Step 4: Find the spring rates for the front and rear leaf springs. The internet is your friend. However, there’s a teeny-tiny issue, which I’ll describe in the next step.

Step 5: Now you can go online to Dennis Grant’s Autocross To Win website and find his Dynamics Calculator and start entering numbers. Except, and here’s the teeny-tiny issue, the Corvette suspension design is incompatible with his calculator because it’s not a coil-over design. The Corvette has FRP transverse leaf springs that do not act at the shock mount location as does the more common coil spring wrapped around the shock or strut.

What I had to do was to mathematically transfer the spring force to the shock mount locations while correcting for the shock angles. (For once, a mechanical engineering background paid dividends.) Of course, the front is very different from the rear and must be figured separately. Then I could trick that bastard calculator by entering modified front and rear spring rates. It never knew what hit it.

Step 6: So far this is all pretty cookbook (except maybe for modifying the spring rates) but now you have to insert some knowledge, hunches, guesses, or whatever you got. You must decide how much damping you want in terms of what percentage of critical damping (65%?, 75%?, 95%?, 120%?) and what damping curve shapes and knee locations you want to specify. Will you use regressive, linear or digressive shaped curves, or mixes of each, and then choose the corresponding main piston designs? And how do you want to split the total damping up between compression and rebound? In most shocks they are not anywhere close to equal and it is not clear at all that what road-race teams do is particularly applicable to autocross. The author of The Shock Handbook questioned various people in the automobile industry as to why they used the split they did between compression and rebound and got no sentient answers. DG’s calculator seems to provide a 2 to 1 ratio, that is, twice as much rebound as compression, which is common. (I’ve used that before with excellent results.) I’ve seen some custom-valved shocks with 4 to 1 ratios. This was common in the 1960’s until Jan Zuidijk at Koni Racing (later the founder of JRZ Suspension Engineering) showed the world that it wasn’t fast and put Koni on the racing map. To make things more complicated, if the compression curve is digressive and the rebound linear, a ratio split doesn’t really make sense. You are forced to decide on a ratio at only one shaft velocity and the ratio will be less on one side and climb rapidly on the other. Many road-race teams these days split it evenly between compression and rebound and a few even bias toward compression, sort of like in the graph below. Almost all use velocity histograms during practice sessions to fine tune for each different track.

Shock Dyno Graph For Ohlins Shocks On My C5- Full stiff

The shock dyno graph shown above is for the Ohlins shocks I had on the front of the C5. The people that valved it gave me pretty much exactly what I asked for, but I didn’t actually know what to ask for back then!

Note that the compression values (upper half) have distinct “knees” at 1 in/s shaft velocity. Beyond the knees the curves flatten out and rise much more slowly. This is a “digressive” curve shape.

The rebound curves (lower half) are linear, i.e. basically a straight line. You can see that at 1 in/s the compression values are higher than rebound. (Not good.) By 8 in/s the rebound values are higher. (Not good either.)

I chose a knee velocity I like and altered the results from Dennis Grant’s calculator to split it up at my own custom ratio that I think is more suitable for a Street-class car. Then I gave the numbers as targets to Penske.

There is no one and no analysis that can tell you the for-sure answer about how much total damping you should have or compression to rebound damping ratios, especially for this weird sport of autocross where we race on all sorts of strange surfaces in all sorts of conditions. There are many people with many different opinions who will be glad to tell you what they think, especially if you buy from them. I have my own opinions, but I’m not going to reveal exactly what I decided. We will just have to wait and see how it works out. I am happy to say that Steve Horn at Penske was a great pleasure to interface with throughout the process of working through the shock specifications and options, not least of which was making sure the resulting dimensions would be legal per SCCA Street-class rules. He was invariable polite. Not once did he tell me I was nuts.

*Edit: I was recently informed that 69-70mph would be too slow (causing me to run out of gear early) given the rate at which this car can accelerate and that 72 is actually more perfect. Always better to be lucky than good!