Has anyone skid pad tested the C4 with modern rubber compounds? Wonder how it would compare to modern vettes? I always thought the C4 was way over tired for its weight. Most modern cars do not run 275s up front and supposedly handle much better. How much is suspension vs rubber?

 

Would love to see the answer to this

i believe a c4 , with z51 or z07 package would match a c8, on the skidpad, if the same tires/wheels (as the c8) were installed.

that said, the c4 suspension has its flaws.
It telegraphs potholes and road irregularities from one side of the road to the other side of the car (my belief is thru the transverse spring)

my old 2004 bmw 330i with zhp performance package felt way more buttoned down on ohio’s typical patched potholed roads

however, on a smooth racetrack, the c4 would outgrip it (generate more g’s) with its wider tires. In my case 275/40r17 on the fronts and 315/35r17 on the rear

 

Unfortunately tyres not even available for my car now 😢

 

I had a C7 Z51 and will say with the pilot sport tires it held extremely well on corners. My new to me C4 has nitto motivo (i don't like) and its no comparison. I do think the C4 could do way better with a comparable tire and new technology shocks. I think the C4 could be close with the new tech. My tires are 275 up front with 315 rears.

 

If you're in the market, consider upsizing your wheels too? Either 17's or 18's...or combo? It might require spaces to push them outboard a bit.

I also have the ZR1 tire combo (like Admiral). Just got home with Michelin Pilot Sport A/S 4's mounted. I didn't have time to test them a bunch, but my first impression is very good. Somehow, they manage to feel firmer, but still "soft". (New tires..ya know!). The steering feels tighter than the Sumi's I took off. Less "lag" in turns. Very smooth on the hwy too. Can't wait to challenge them a bit. Has a bit more of that go-kart feel -- which is GOOD!

 

Any spring design will do that. And anytime you raise or lower the tire on one corner it will change the corner weights of the other three.

 

So correct me if wrong the C4 having slight weight (3300 vs 3400) advantage and tire width advantage (contact patch)the C4 should be able to outperform C7 skid pad with same tires/shocks? One thing that may help C7 is the slight rear balance of weight distribution though. I think the two cars would be pretty close in numbers.

 

Let's dispel a couple myths:

• There is no such thing as "over-tired for the weight." The lighter a tire is loaded, the more lateral and longitudinal grip it provides. That is a fundamental tenet of suspension design, tuning, and dynamics.
• There's no more "telegraphing" of irregularities from one side to the other with transverse-sprung car than with a car that uses coil springs. Wheel rates are whatever they are, regardless of whether they are provided by a coil or transverse spring or a sway bar.

Suspension does matter, and the C5 and up are better in this department than the C4. The rear suspension of a C4 is probably a bigger compromise than the front, but the front has some issues, especially in the 88-96 models. This basically means the tires aren't always aligned to the road in the best way possible. The C5+ also has a bit more rearward weight bias, which generally helps lateral grip. Finally, the C5+ have wider track widths, which helps lateral grip.

All that said, you can get C4 to generate impressive skidpad numbers with the right tires, and you can fit a lot of tire under a C4 at both ends. The OP's issue is that there aren't a lot of really high-grip street tires in his sizes. However, put a set of Hoosier A7s in stock sizes on that car and it will have grip for days. I did some autocross events on 315 Hoosiers at both ends of my C4 and it was sublime. Best time ever! I don't think skidpad numbers are the most important aspect of road course performance, though. The place where modern cars have improved the most is in transitional handling and when combining inputs such as braking or accelerating while cornering.

 

Totally agree track width is a factor. Come to think of it the extra width would allow a thinner tire as the load is spread over more area to create similar effects. I also agree improvements in transitional articulation is also very evident in later year corvettes. C4 has no chance against the more modern cars in this arena without significant mods and even then i doubt it could compete. I chose skid pad to mitigate the power difference in the cars which would be a greater factor in say slalom testing to try and isolate tires as the main factor. I mean the C7 still uses transverse leaf springs just like the C4. The design does not appear much different. Little tweaks in geometry for sure to meet the weight, balance, chassis stiffness, and track width for sure also complimenting new shock technology such as magnetic ride control.

Found this Car and Driver article. 1.01g with now terrible compound goodyear garorbacks. Just makes you wonder about modern tire capabilities on the C4.

 

The load is still only spread over the contact patch, no matter the track width (or wheelbase). It's just that there is load transfer for a wider track width if all else (especially CG height) is equal.

Small correction here: slaloms also make power completely irrelevant because you maintain a constant speed through them, just like on a skidpad.
The front architecture is similar (both use double A-arms with a short upper and longer lower) but the geometry is quite different. The rear architecture is completely different and vastly improved on the C5+. Instead of trailing arms and using the halfshaft as an upper lateral arm, the C5 moved to upper and lower A-arms with a halfshaft that just drives the car instead of also serving as a suspension link. I think the trailing arm part can work well, but using the halfshaft as the upper lateral link on the C4 really hurts the geometry. It's elegantly simple and works well, and it was a massive improvement on the shitty C2/3 rear suspension.

 

Thanks for the wealth of knowledge. I enjoy learning and you have shown me a ton. I was a fox mustang guy for years and ended up going three link on them for better handling. The three link much improved those cars cornering ability but I'm still a newbie on corvettes and IRS systems. My C4 is a base and i took some spirited on ramp turns just for fun and started feeling the rear 315s start to slide a bit earlier than id expect. Coming from the C7 i knew the C4 would not be as good. Not that it was bad just not what i was used too. Felt a bit like my 2003 mach 1 mustang three link with 305s in rear. Also granted this car is still sitting on all original suspension including shocks and bushings at 110k miles. I’d like to get a bit firmer ride and turning performance by swapping in the z51 bilsteins and all new bushings to start. It’s purely a street car right now. But i figure tires have a lot to do with it which got me thinking.

 

I owned and autocrossed/tracked an 89 Fox police car and a 97 SN95 SVT Cobra. Those cars definitely had bad suspension architecture (rear) and geometry (front)! Replacing the entire rear suspension with a torque-arm or 3-link was definitely a big help.

Depending on the year, the base C4s were pretty soft from the factory because they were aimed at old men who just wanted to drive around on the street slowly. The later the year, the softer the springs, basically. The good news is that they are just a set of springs and shocks away from being way better. The bad news is that there are essentially no new stiff monoleafs on the market anymore. There may be in the future (Van Steel as the old VBP Xtreme spring molds but they haven't offered any new ones for sale yet). For now, the only ways to improve the spring rates of an 88-96 base C4 are to find a used set of "challenge" or VBP Xtreme springs (probably not easy), or go with a coilover setup (all the rage, overhyped, but a good kit works well).

Tires have a ton to do with it. What's on your car now? Also, what year and wheel size(s) do you have? If you can tell us how you plan to use the car, we can provide some recommendations for good tires. For shocks, instead of the Bilsteins, you may want to consider the Ridetech HQ single-adjustable shocks. They are really high quality monotube Fox dampers with easy-access adjuster ***** (unlike the rear Konis for this car), and they have good damper curves for a range of stock C4s (including the Z51s with "challenge" spring rates). OTOH, if you might go with coilovers anyway, just hold off on purchasing shocks. The Ridetech coilover setup is a great option for that, btw.

Finally, if you're at all interested in really exploring the limits of your car, I strongly suggest finding some local autocross events in your area. You can really wring the car out safely there, and you'll learn a ton about vehicle dynamics along the way. You'll also see a wide range of tires at all performance levels so you can get a better idea of what you might want to use.

 

My car is a 1995 base with A-Mold 17x9 front on 275s and 17x11 out back with 315s. Tire are nitto motivo which were on car when i bought it. They were brand new so ill run them out but i don't care for them. I know moving to an 18 rim gives more options but the vette looks fitted to 17inch wheels despite being able to go bigger they just don't look right imho. Maybe I'm just spoiled by the C7 handling although i think this C4 has great potential. It is a street car but may autocross for fun. I actually daily drive it most of the time just because I would rather drive it than my truck. Never been a truck guy but they are useful. I would like to get suspension set up for 450-500hp. Likely stroker or engine swap in future.

 

On tires, almost anything would be an improvement on Nitto Motivos in terms of performance! The M/T Street Comps would be a ton better in the dry. If you need an all-season (the Motivos are all-seasons, as in they suck in all seasons) then there is very good news: Michelin has their newest performance all-season, the Pilot Sport All Season 4, in the sizes you need. Those can be driven year-round and they are very good dry-weather performers (probably not quite as good as the M/Ts, but I be they are close) and they will of course do well in the wet and cold. You can autocross on them, although they won't be competitive with the really good competition or the best summer tires. If you don't need cold/rain performance, then the M/Ts are probably your only decent option. They should perform better than the Nitto 555 G2 in the dry and wet. There are a few competition tire options in your sizes, but they won't make good street and daily driver tires.

If you really want to prep your car for 450hp, you should probably wait on shocks and get a good coilover setup. You'll want stiffer springs than whatever you have right now, and as I wrote before, that's about the only way to go about it these days. You'll want stiffer damping rates to go with them, too. 450rwhp is a lot of power, more than most people think. I don't think my C4 had that much (it's a 396 with around 420rwhp) and people who rode in it always thought it had 600hp! In reality, it was a touch faster from a roll than a stock C6 Z06, which is still fast. It was fun, and still streetable, with a very wide powerband.

 

as a guy who is in the process of learning to be an amateur racer, my unsolicited advice right now to forget about hp for now. learn car control first. a decent driver in a miata will be faster than you for the first couple years. that is humbling. your ho doesnt matter right now.

 

I disagree with The guys on here saying that the bmw suspension (on my 330i zhp) doesnt telegraph road irregularities from one side to the other differently.

Running my c4 down a road where the ride side is patched potholes throws me all over the place

where as in the bmw , it felt more buttoned down to the road and less scary to drive fast around hills/corners

on a smooth racetrack, the opposite is true on my c4 (the c4 was less scary to corner fast in)

 

my experience is this topic is highly tire age, tire pressure, and alignment specific.

 

Nobody said your BMW doesn't articulate over uneven surfaces better than your C4. We said that the fact that it does has nothing to do with the transverse monoleaf spring in the C4. There are a bunch of variables that affect articulation over bumps, but the form factor of the spring isn't one of them. Here's a writeup I did for my local NCCC club: Transverse Leaf Springs.

 

My last track day was on 315/35R17 Nitto NT 555 G2S on all four corners. Accelerating out of turns and even neutral input in turns I definitely was able to find the limits of my traction, and as a totally novice new racer I felt a bit disappointed by the "lack" of gs experienced (as compared to say ripping a berm on a mountain bike, or hitting a step up at high speed).

I have a race in 6 days and a set of brand new 315/35R17 Nitto NT05 (not the R version) on all four corners and I am interested to see if the increased grip will help in the corners!

 

had a look and i see the nt05 are 200tw tire vs the nt01 is r compound (100tw?)

does the race series you compete in limit you to 200tw? Thats pretty normal actually and in my series it is also limited to 200tw. (Champcar, Luckydog)

I currently have the 555’s on my zr-1 and just got home from a monster track day and i pushed those things way way beyond grip. i wanted nt-01’s but none available.

lets us know how the nt05 compares please!