MDeg

I ran my first autocross event in my C4 last summer and have gotten absolutely hooked since. I have scoured over dozens of old C4 autocross /track day threads on this forum but most of them are years old and difficult at times to get specific information from.

I wanted to start a thread to help:
1. Obtain recommendations and insights for setting the car up for different competition levels and events
2. Get driving feedback / advice from more experienced drivers
3. Potentially serve as a means for finding go-fast parts, tires etc.

C4s, although not nearly as capable as the C5 / C5 Z06 platform, are in the obtainable first autocross / track / performance car category for a lot of potential buyers right now. I know I was interested in reading about how the car holds up these days and I'm guessing there are lots of others who are currently in the same boat.

A little about mycar -

I went to the Ron Fellows school for C8 owners last spring and had an absolute blast on the track and in their autocross competition. My C8 was on the far side of the country being worked on for most of the year and I left really wanting a "cheap" performance car that I could cruise around in and occasionally autocross or take to track days until I had the 8 back. The obvious answer was just to buy a Miata... but C4s were only slightly more expensive, and I'm a Corvette lifer, so that made for an easy decision. I ended up finding a yellow 94 LT1 6 speed car in Tallahassee with about 120k miles. At the time I was buying, there were very few manual cars available locally ( I live in Ohio), and this one was the best deal I could find on this half of the country. The same lady had owned the car since 96, and didn't have time to enjoy it any more, but the car appeared to be in great shape given it age and mileage. I ended up flying to Tallahassee on the Saturday of Memorial Day weekend, driving the car 8 hours to Nashville that same night, enjoying the city with friends the next two days, and then hitting NCM and checking out Bowling Green on the way home to Ohio that Monday.



First shots of the spring here in Ohio


The car made it back to Ohio fine, but ended up having a few things that needed updating throughout the summer. I replaced leaking brake and fuel lines and installed new O2 sensors and weatherstripping. On more thorough inspection, its a clean car for the most part - but it has some rust on the underside and at the end of the day 30 year old cars are not perfect.

I've had it at 4 autocross days since - I'm off to bed but will post about those tomorrow if I find some time. Hopefully this thread serves as a mean towards some helpful conversations for new drivers / owners (like me ). -MD

MDeg

Between the car being in the shop waiting for parts and me being busy with life things, I only made it out to one event in the Vette last year - happened to be the DriveAutoX event by Optima held in Ohio. I was familiar with the OUSCC but "DriveAutoX" sounded like it was geared toward beginners - I showed up in the C4 bone stock and almost turned around when the parking lot was full of guys from around the midwest bringing their purpose built competition cars out of trailers. The classing they use pretty much puts all modern vettes together - so I was running against C5 / C6 Z06s that were built for CAM-S or Ultimate Street Car. There were a couple C4s - the one that sticks out was JB Boyer's silver car (think its a 92?) with an LS7 swap. Really bad *** car. Obviously, I was not even close to being competitive, but I was able to get a lot of seat time. I think we ran something like 6 times in the morning and 6 in the afternoon.

To that point, the extent of my "competitive" driving was taking part in the owners school and participating in a novice school held by our local SCCA club in my daily driver econobox Focus. The Vette again had been in and out of the shop a few times and I wasn't sure it would survive the weekend. These are all my excuses for why I was ridiculously slow by the way, if you can think of any other ones I can use, let me know.

Video of one of my runs from that day. Very soft on the brakes and kind of babying the car around the course as you can tell.

MatthewMiller

First, congrats and yay for getting your Corvette (of any generation) out doing what it was designed to do: go fast around corners! This always warms my heart. At this point, the only person you really need to think about competing with is yourself: i.e., just improve on your last run each time, if possible. Pick one thing to do better (could be one corner entry, one line through a slalom, whatever) and just do that thing better. The times will come along. Your C4 isn't going to compete with heavily modded cars, and that's fine: it's perfectly good for getting started. I wouldn't modify anything until you sort out what group(s) you want to regularly run with and which class you want to be in - these decisions will dictate what mods make the most sense for you, if any. For now, just make sure everything is safe and maintained and maybe get an alignment to crank in the most camber you can get front and rear with zero toe.

The Drive AutoX events are kind of nice for beginners because you get lots of runs which helps you get seat time. There is nothing more important than seat time...if you can get "seat time" riding through with the best drivers that's really helpful too (or riding through as they drive your car). If your SCCA Novice School event is anything like the ones we do in my region, that's a great thing to do (do it again this year if you can). If you have any regular NCCC events in your area, they usually give a lot of runs and you can be classed with other stock C4s for a better comparison. If you get serious to spend a weekend in a school setting, I strongly recommend the Evolution Phase 1 and 2 schools. You will get instruction from some of the best drivers in the country, including them riding with you and you riding with them. Later, you can go back do their Challenge class as an advanced curriculum.

MDeg

Matt, thank you for the advice and guidance. I have read through a number of your posts about these cars and their best set ups and tire combos. Like you said, I am planning on keeping the car stock outside of maybe a few mods to keep it safe and reliable.

Ironically, the Evo 1 + 2 schools are this weekend at our club and I signed up for Phase 1...but there are 16 people waitlisted in front of me. Did not realize it was such a small class. I will certainly do the event next year if they don't end up planning a date for NCM, which I hear may be in the works.

But there is a silver lining - I saw a post from Nelson Ledges this morning advertising a beginner track day on Saturday, so I will be making the hike up there in the C4 tomorrow to partake in that instead of Evo since I couldn't get in. Outside of Motul RBF and other fresh fluids, the car is untouched, so I will be interested to see how it holds up and performs. As you suggested, I am taking every opportunity I can to get more seat time.

Will post an update after Saturday - thanks again.

MDeg

I was waitlisted for the Evo autocross school last weekend and therefore out of plans for the weekend until I saw an add pop up on Facebook for a beginners track day event at Nelson Ledges. I live in Dayton, about 3.5 hours southwest of NL, so the idea of driving a 125k mile Corvette so far away for its first time on track was a bit intimidating. But I tend to just go for these things so - I sent it. Stayed with friends near Kent State Friday night and finished the last 30 minutes to Nelson in the morning. It's a trip driving by horse drawn buggies through Amish country on the way to a race track.

The event was structured through Reed Kryder racing and only cost $200 for 5 20 minute sessions. The first heat would begin around 10 and the day would end at 4. There were a couple other Vettes - C5 and C6 Z06 specifically, a lot of Mustangs including a brand new GT500, a couple Porsches, and a hodge podge of other street cars in attendance. I showed up in the C4 completely stock (outside of racing brake fluid) on an old Yoko 300 TW 275 mm square tire set up. It was a cool morning - in the low 50s - which I was happy about because my car doesn't like running hot.

We began the first session with 3 guided laps at low speed, and I found myself behind a ton of slow traffic once the lead car pulled into the pits. I babied the car impatiently behind older guys in Mustangs who were either being super cautious in warming up the tires or had no pace whatsoever. After another slow lap, they pulled into the pits, and I suddenly had what felt like the entire track to myself. I gunned it on the front straight and turned into the first corner..... and almost completely spun the thing out. I'm honestly not sure what happened, from the video it looks like I felt a little understeer and then maybe pumped the brakes mid turn, cutting the rear end loose. I fought the car for what felt like an hour, thinking for sure I'd end up in the grass and looking like an absolute idiot.


Well I definitely still looked like an idiot - but I somehow managed to keep the car on track. Again, I don't know if the tires were just too cold to be driving that aggressively yet or if I braked in the corner or what happened, but open to any suggestions / advice that would prevent me from crashing at my next event...

I got through the rest of the first session with no other real issues. I was driving much more conservatively but didn't let the scare shake my confidence too much. Started to find a bit of a feel for the car as the session ended.

I went out for the second session with only a new 911 in front of me. Plenty of space this time - and an opportunity to actually try to find some pace. I stayed out of traffic for most of the session, and ran low 1.28's at my fastest. A guy in a small block Ford swapped MG on track tires was running 1.27s and a guy in a C6 Z06 was running in the teens... so I'm not really sure how to judge my times. I think I read somewhere on the forum of one of the guys in a modded C4 running in the low 1.20's.

My only previous track experience was with the C8 owners school at Spring Mountain. The two experiences could not be any more different. At the Ron Fellows school, we had classroom and film sessions, lead cars to teach lines, passenger rides with the instructors, turn in and apex cones, etc. With these event - there was no instruction outside of generic safety rules and a quick overview of the track. For $200 you can't complain but I would have felt more comfortable pushing harder without having to guess and check where the limit and appropriate lines are.

The cars are polar opposites as well. The C8 was my first Vette and after driving 9k miles around America in it, I knew it like the back of my hand. I could push and push and push in that car and never once felt uncomf
on track. By the end of the second day at Spring Mountain I was in the fastest group on track and placed third in the autocross shootout. So - based on this limited experience - I somehow had convinced myself that I was a natural at this whole driving thing.

Reality sank in after a few hot laps in the C4. Where I could stomp the gas and brakes in the C8 without losing traction, the rear end of the C4 would cut loose with any sudden inputs. Im not sure if this is just the nature of these old analog cars / driver inexperience or if a lot of it was due to the tires I was running - but there were a few harrowing moments. You can see in the video quite a few times where the rear end gets light under hard braking and almost snaps out. Nelson is a very fast track with lots of large radius turns and sweepers, so you're going to either add or lose a lot of time if you're not willing to carry them with speed. In the C8, it wouldn't have been a problem, in the C4, I felt much less confident. I felt myself braking early just because I wasn't sure how the car would track out of the corners under speed. It was a bit of a handful to drive.


After lunch, I did a quick run around on the car to make sure nothing was smoking, leaking, etc. I did a double take when I looked at the front brakes....my pads were completely gone and I had been rubbing metal to metal on the rotors. After calling 3-4 places trying to find pads, I finally found an O'Reilly's nearby that could order them in from an hour away. I babied the car there, jacked it up, and did a front brake job right there in the parking lot. I finished around 330 - and rushed back to the track by 340. Just in time to sneak in halfway through the final session of the day and log another 10 laps.




Overall - there were a LOT of learning moments in my first track day. Being more thorough in preparation, being cautious until the tires are properly heated, doing more research into proper racing lines etc are all going to make my next event more enjoyable. But - I got it under my belt - had a lot of fun - and somehow managed to drive the car home with no issues that night. I am running AutoX next weekend with CincySCCA (and potentially one of the Columbus Regions) and then hoping to get back to Nelson for SCCA Track Night near the end of May. I am picking up a pair of used Toyo RA1s in Tennessee this weekend and hope to have them mounted for my next day. It will be interesting to see how much of the car's unpredictability stays with the new tires.

Open to any thoughts / insights / advice in track day prep, things you noticed in my driving, upcoming events in Ohio, etc. Thanks !

MatthewMiller

Great stuff there! The pit stop at O'Reilly is fairly heroic. The second video looks pretty good to me, actually. You're on good lines and your inputs seem pretty calm and well blended. Also, props to you for giving a point-by when someone faster was behind you. Your lap times seem to be pretty solid compared to the other cars you mentioned. So it seems like things are going well.

The first video with the near-spin was entertaining. I think you just kept pushing on the brake pedal, whereas the best idea with oversteer is to get off the brakes and lightly feather the throttle in so you are stressing the rear tires as little as possible. It's counterintuitive for most of us, and it takes practice to make it second nature to get off the brakes when things are literally going sideways. But the thing about braking is that you're heavily unloading the rear tires, so they have less lateral grip. As you feed in steering angle to enter a turn where you're still braking on the way in (trail braking), you generally need to gradually let off the brakes at the same rate you add steering angle. I'm guessing you didn't quite let off the brakes enough as you turned in, and therefore asked a little too much of the rear tires. Then as you started to feel the rear tires let go, you braked even harder (the natural instinct plus decades of erroneously being taught that slower is always safer), inducing the "death wobble of oversteer." It's a classic.

As far as any setup tips that could help avoid the over steer on corner entry, make sure you have the max negative camber in back and maybe a touch of toe in (1/16" or so). Make sure you're wheel bearings are in good shape as well as your halfshaft U-joints - if any are bad you could be gaining positive camber on the outside rear tire and losing grip. Also, make sure your front shocks in particular are still damping adequately - if they aren't (or even just one of them isn't) then you'll get oversteer as the car rolls on corner entry. Finally, make sure you don't have toe out up front - zero or maybe 1/16" toe in is good. The C4 is generally a pretty stable platform, so it's not prone to lots of snap oversteer or other evil handling traits. But it doesn't have the sophistication of the C8 platform, and it also doesn't have any nannies to help you keep it straight (you can turn the nannies all off in the C8, but I'm betting they didn't advise that at the Ron Fellows school). Finally, remember that in the C4 you are nearly sitting over the rear tires but in the C8 you're stilling way further forward, and with a 13" longer wheelbase. If the rear starts to come out in the C4, it's going to feel a lot more dramatic than the same amount of slip will in the C8. So part of it is just perception.

Keep up the good work!

VikingTrad3r

There has been a real uptick in cars on track this year! Awesome

On the corner entry oversteer I didn't see any abrupt steering inputs but I did see what looks like your nee slightly raising which implies you either lifted or lifted and breaker as you maybe thought u were going to fast.

I'm noooo expert on this but I'm learning along with u and a few others on here right now .

What setup are you running?
I remember seeing your pickup vid on YouTube and I don't think I saw fx3. Is it an fe1 or z07 car?

I suspect alot of the looseness u r experiencing is base springs, narrow bars, and old tires? What tire pressure were u running?

I'm not sure what the c8 is like but the difference between my c4 zr1 (which all came with soft springs and narrow bars), my 86 base soft spring 4+3, and my 89 z51 stiff spring car is night and day different. its not even close. The true z51 car is way less noodles.

In 94 what brakes was it still j55 as option?

I found that with new tires at the 34hot max tire pressure I could get around the track fine but the car flops and lunges and rolls around with the soft springs. Turning the fx3 to performance mode helps but in reality it simply dampens (slows) the movements of the car, it's still rolls and tips the same amount. Z51 springs feel way ways better

Matt you said something the other day I've been thinking about. You said that stiff or soft the weight still transfers. (I think, I can't find the thread but I think that is what you said)

is It that it does it with less body roll with the stiffer springs? I need to review all my YouTube educational videos again on this subject.

MatthewMiller

Yep, the weight transfer due to acceleration (in any direction) happens because the car's CG is above ground and all acceleration forces ultimately act through it. You could have literally no suspension (weld the control arms to the frame so it doesn't move at all) and the same weight transfer would happen.* A go-kart has no real suspension and it still has weight transfer. There's a useful discussion of weight transfer at the beginning of this website, among many others.

Lateral weight transfer is always bad: four tires holding up a given mass will always give the most grip when they are equally loaded, so weight transfer causes reduced grip. That's why getting the CG lower is always helpful: it reduces weight transfer. Likewise, a wider track width helps reduce lateral weight transfer.

*If a vehicle rolls or pitches, the CG actually also moves a little bit in the same direction. So technically roll or pitch causes a bit of weight transfer of its own, but the CG is low enough and the chassis movement small enough in most cars that we can ignore it.

MDeg

As you said, just based on the video I think I either lifted or got back on the brakes which upset the balance of the car. Scary moment to say the least lol.

It is a base FE1 car - none of the go fast parts. The previous owner put the 275 square set up on, I believe it would have originally come with 255s up front and 285s out back. It does not have the J55 either - I think those became standard in 95. I will eventually put wilwoods on it but can't afford at the moment - may pick up some C5 Z brakes for a budget option for the time being.

MDeg

Lots of helpful info as always, Matt. Going to have to work on balancing this car with the brakes and throttle. The pit stop will definitely be a story to tell - I was just lucky they were able to order in pads. I was amazed that none of the other stores had anything that would fit my car. As far as my driving - I couldn't quite figure out the carousel which is one of the most important sectors as it sets you up for the longest straight. Think I needed to hold an outer line and then come in for a late apex; I was more or less hugging a middle or inner line from what I remember. And again, felt like I could have been braking much later than I was in some of the quicker corners. Just didn't want to learn where the limit was the hard way.

I am gone for a side by side / offroading trip this weekend and then its back to work. Multiple AutoX opportunities next week, SCCA track night the following at Nelson Ledges, and then NASA HPDE Memorial Day weekend. Hoping to hit all of the above - need to get my ducks in a row with the car first.

VikingTrad3r

boy do you guys have alot of hpde events. up here in canada its not that way.

c5 fronts are BIG step above J55 in my limited but experienced opinion. i can compare my c5 mn6 to my zr-1 with j55 (and i actually have gs calipers which are a smidge stiffer yet), both with same compound pads, and the c5 stops WWWAAAYYYY better than my Z. there may be other thing going on, but c5 i think is awesome, cheap (i see c5 front calipers for 50$ all the time) and easy upgrade.

so far i have not seen an indepth review of the wilwoods for c4’s. there is a couple vids of a guy who spent a few thousand on c6z06 upgrade for his c4, he says they are fantastic. just too much cake for me. ive done three seasons with my j55’s using powerstop track day kits and i finally got to the stage where i was at the cars max last year....but im doing another season unchanged because i think there is more in the car and im using it as an excuse.

im stoked for all the c4 track hpde and auto cross threads!

MDeg

I will probably just go with the C5 brakes for the time being - as you said they are super cheap (relative to other upgrades, lol) and should be all I need for the time being. The only downside is Im not sure how it will effect how Im classed for autocross - not that it really matters for a newbie anyway, but getting put into CAM-S or one of the prepped classes with a stock motor would be... rough. Regardless, want the car to be more reliable / safer/ enjoyable for the track.

Also looking into options for seats - open to any thoughts on what will actually fit / are reasonably usable for the street as well as track.

MatthewMiller

Brakes will bump you into CAM-S or SSM (there may be another class for you, but those are what I know). But you are headed there anyway if you get wider wheels and tires.

On brakes, my car had a set of the Wilwood 6-piston Superlight calipers and the floating rotors to go with them. It still had stock brakes on the rear. For the track, they made a big difference in heat capacity when loaded with good track pads. You really don't have to do the rears. Wilwood now sells a ready-to-install kit for this setup. The downside is that you can't use stock 17x9.5 wheels with this kit. I'm not sure about the C5 brakes. However, be aware that comparing the way a C5 brakes to a C4 doesn't tell you much about the brake hardware: it tells you a lot about the C5's much longer wheelbase and more rearward weight bias, both of which help any car stop faster. The stock C4 brakes will lock up the tires, so you don't improve col-stop braking distances by upgrading the brakes. You only improve the heat transfer capacity of them, which is really only important on track days where you are running multiple hot laps before coming in. So the Wilwoods with good fluid and pads will help you stop a lot better 10 minutes into your lapping session.

VikingTrad3r

Matt you are always good for grounding in facts and reason!! I guess you are right. They will certainly lock up the tires so i guess i was noticing heat fade.

Mdeg, on seats, not sure what your vision is for your car but for autocross and hpde, this may sound surprising but the stock sport seats from both my 1989 z51 and 1991 zr-1 are perfect for hpde and autocross. I can see how the lack of side bolstering on the later style seats would suck for hpde. My wife has a 99c5 she tracks and she had to get an aftermarket seat. those are similar to the late c4 syle i think in they have no bolsters.


One trick you can try for your upcoming hpde week is, use power seat track to go full rearward. Then press the cinch button on your seatbelt. use your hand to tighten the belt. then move your power seat track forward and you will be ultra cinched into the seat. combine that with the style of seat i have, im not going anywhere! i had an instructor comment on how the seats are the best hpde stock seats hes ever seen by a long shot.

i am building my 89 into a dedicated hpde car , still street legal, i am going to try to find an “alcantara” microsuede seat skin forbthe driver seat. havnt found them will probably have to get it made. that would add a new layer of friction!

Some guys swap to the manual seat racks to save a pile of weight. ill be doing this on my 89 build.

obviously, a dedicated wheel to wheel competitive build requires a full on race seat.

MDeg

So I could be wrong but I think you can run updated calipers / brackets in STU. You can also run up to an 11 inch wheel and 315 tire. Thinking this might be the ideal fit for the car for the time being - could be reasonably competitive at a local level without spending a fortune to LS swap etc to keep up with the guys in CAMS, but still have enough flexibility to update the car a bit for the track.

Was off this weekend - doing some side by side riding in Tennessee. Running SCCA Solo Sunday, then hoping to hit Nelson and Mid Ohio back to back the next two weekends. We will see how the car holds up...

MDeg

Some pics from a test and tune a couple of weeks ago with Cincy SCCA... with some fresh cone markings of course...

DWAVette

Very cool thread. Thank you. I am hoping to begin this soon myself. My 91 coupe (stock) is almost ready to start playing with the little boys. There is a track club that runs monthly about 45 minutes from my house.

I can’t add any value to the thread. Just a consumer here.

Would something like the side mirror window deflectors be allowed on a car? I added them to my 91 and found a huge difference in the amount of wind entering the car with the windows down. These were adhesive backing only but I added some rivets in addition.

MatthewMiller

Sorry, been out of town and now catching up a bit. Yes, STU would be a very interesting option for a C4 with a stock engine. That's why I didn't ever consider: my engine wasn't close to stock! You could definitely upgrade the brakes, and you can run any springs/swaybars/shocks (including coilovers if you're inclined). And 315s on 11s is perfect for this car, front and rear. The pax index is slower than CAM-S by a decent margin, so that tells us that overall CAM-S is faster. So an STU-legal C4 driver should definitely look at STU as long as the owner doesn't want to mod the engine.

Yeah, my 96 had the base/manual seats and they were lighter than any aftermarket seat with padding and real upholstery! with a harness and harness bar, they held me in reasonably well, too. The real challenge with any aftermarket seat is getting it to sit down low enough. The previous owner of my car found that they all sat higher, and headroom is at a premium in a C4. So measure twice, cut once...or something like that.

BTW, a good steering makes a real difference. The PO of my car added a Momo Corsa and it was great. It's a bit smaller in diameter, too, which helps with knee-to-wheel clearance.

MatthewMiller

I think those are probably allowed even in stock classes. Aftermarket wings and spoilers aren't, but these deflectors can't realistically be claimed to add any downforce. Sam Strano sells something like this for new Camaros and people use them all the time. He is a multi-time autocross champion and I'm sure he wouldn't sell anything that's not legal. And now that I'm tracking my Camaro, I will probably be buying some soon.

Addendum:
You made me go look in the rules. SCCA's Solo (autocross) Rulebook says in Street (stock) class the following
I would lump these wind deflectors in with "comfort and convenience modifications which have no effect on performance and/or handling." So no problem with them in any class I can think of.

MDeg

Got it. I am still intrigued by trying to fit 11.5s to maximize performance as building on the car continues and it moves to a different class anyway but for the time being, I think STU is perfect. Should give me some flexibility to replace things with reliability upgrades / make the car a bit more track capable without having to spend a fortune and compete with the national champion level drivers our region has in CAMs.

I will be running our novice autoX school Saturday and then points event 2 Sunday. Fitted the pair of RA1s (275 -40-17) I picked up in Tennessee, and had Paul Curley do an alignment on the car. Will be interested to see how much the new tires and alignment change the feel of the car. Obviously will have to run in a class that I am outgunned in but should be a good learning opportunity.

Hoping to pick up some C5 brakes and install next week and then have a number of little things I need to do around the car this week to prep for track days the next 2 weekends.