I don't want to spend 600 bucks. Are you in a position to weigh your hoods and tell us what the diff is?

 

I read the first 5 pages, and page 15 so I don't know if this was covered or not...couldn't find it in a thread search. But, I made two runs at a SCCA autocross track. It was when I first got the car, so it was just for the fun of it...repro tires had a rating of 500 BC or something like that...they made a LOT of noise.

The first thing I realized was that the inside door strap which is there to pull the door closed whacked my left hand so bad it was bruised and sore for a week. I'd say removing it is a required safety upgrade, or getting a smaller steering wheel.

I was really pleasantly surprised by how nicely the vette performed even with the suspension in as bad a shape as it was...being a 40,000 mile original with bushings that you can see through. A C3 is nicely balanced 51%/49% F/R for road courses.

My first upgrade was tires...BFGoodrich R1's were available with a rating of 200AA and well worth the $80 each. But, they don't make them anymore and the Drag Radials have too soft a sidewall for road racing. After doing a lot of searching I figure that the Dunlop SP8000 in a 245/50ZR15 with a rating of 200AA available at TireRack.com for $156 each...they have full tread depth an an excellent street/race tire.

If you compare the specs of the Dunlop to the Hoosier R6 245/50ZR15's you will find that the specs are identical with the exception that the Hoosier has just 4/32" of tread while the Dunlop has 10/32". The Dunlop are a LOT more affordable since the Hoosiers run $200 each and will need to be purchased at least 2.5 times the rate that the Dunlop would need to be purchased.

As far as weight is concerned I am always an advocate of a heavier vehicle so that the tires can get more traction and a more powerful engine to take advantage of that traction. When speeds get beyond 60mph then of course a lighter vehicle with air foils is the way to go, but for auto cross I don't see any reason to try to lighten the load.

 

you got to be sheiting me.

245/50/15's are going to look like lowrider tires on a vette. Got any picts. Hoosiers are a racing tire and will wear out 2.5 times faster but you would get a whole lot more grip too. There's a big big advantage running racing DOTs.

 

yeah that's the not making sence...a lighter vehicle is easier on the tires, it's not just the weight that gives you grip. When cornering with a heavy vehicle all that weight will start to work against you when you get lateral weight displacement (and therefore body roll) the tires have to work so much harder. Oh and a lighter vehicle stops faster, corners faster, handles better, consumes less gas, accelerates faster.....lighter = better

Turtle, I can't weigh my hood...not unless I cut it out

I got mine from JCWhitney!! Yes, from them! They have the same hoods as zip has, from legendary fiberglass. Anyone with a zip hood will have received one drop shipped from LF most likely. It was much less than 600$ back then and it fit pretty good.

 

I agree that the Hoosiers are a better tire than the Dunlops. Notice that I made sure I didn't say the Dunlops were better, just that the specs were identical...which they are:

Tire Specs for Dunlop SP8000

Tire Specs for Hoosier R6

Here's the comparison:

SP8000: 200 AA with 10/32" of tread
R6: 40 CA with 4/32" of tread

The SP8000 has 2.5 times more tread (10/32" vs 4/32").
The UTQG rating indicates that the R6 wears out 2 times faster than the SP8000 ( (200/10) / (40/4) ).

So...my mistake...the SP8000 will last 5 times longer (2.5 * 2). And, the R6 apparently has a rubber compound 2 times stickier than the SP8000...on dry asphalt. On wet asphalt the SP8000 has an A rating while the R6 has a C rating. If you only drive when the roads are dry then the Hoosiers are the way to go if you want to spend over 5 times as much as the Dunlop. I suppose you can just change your tires to the Dunlops if the roads are wet. But, I didn't think you wanted to spend too much money on tires. I think the Dunlops would work for you...yeah the Hoosiers might give you a little more traction, but not as much as you might think. If you are constantly sliding around then yeah the Hoosiers would be a necessary dollar sponge, but I'd suggest trying the Dunlops before you start spending a lot of money on tires.

OK...that's just the tread depth and UTQG rating...now let's look at the shape of the tires.

SP8000: Section Width=9.6" Tread Width=9.1"
R6: Section Width=10.1" Tread Width=9.2"

The sidewall of the SP8000 appears to be stiffer...it's mid-wall bulge is .5" while the R6 has a .9" bulge. This spec indicates that the R6 will have more sway and roll than the SP8000...though not as bad as the BFGoodrich Drag Radials which have about a 2" bulge. So, with this spec the SP8000 appears to be the better road racing tire.

All the other specs are too close to make any difference. If the difference in these two specs is worth over 5 times (add in dismount, mount, and balance) the price of the Dunlops then you are much richer than I am. I had to install a set of BFGoodrich T/A Radials because that's all I could afford at the time.

 

I agree that the tires have to work harder. And since the tires have relatively the same contact patch then yeah...there is a sweet weight which would maximize the tires ability to grip...any less and you wouldn't be using your maximum traction capability...any more and you would be sliding around and not be able to accelerate, corner, or stop as fast. What I'm saying is that in an extreme case where the tire contact patch was increased by like twice as much then the weight of the vehicle could be increased...not twice as heavy, but still heavier...and be rewarded with increased performance. There are light weight go-carts that have a very high power to weight ratio, but they are just too light to get enough traction from their tires to beat a heavier vehicle which has a lower power to weight ratio...in this match-up the heavier vehicle wins...partly because of weight and partly because of the tire contact patches. But, lighter race cars compensate with air foils to create the additional down force which weight would have otherwise given them. Yes, the lighter vehicle with the same horsepower would have less momentum and be faster in the corners which is why I said that the heavier vehicle needs more horsepower to compensate.

I don't know...that just makes sense to me, but I think I was speaking out of context. Some crazy thought in my mind is a vehicle which has a tire diameter of 1 mile and weights 100 tons and has 1 million horsepower Vs. a C3. I'm thinking the monster vehicle is going to win.

 

I run cheap 160 wear rating Summitomo's on my car for the very same reason. Impractical to drive on the street with racing compounds high cost yada yada yada.

I am just saying the guys that come to the track and switch to racing compounds can corner much quicker. Big big advantage.

At the point where i want to get more serous i will have to find a small trailer and bring a set of racing compound tires with me.

Racing tires = more fun.

 

Yeah...you can always ignore the jokes about being a Trailer Queen as you fly right by them on the course. A serious racer knows that it's fairly cheap to find a decent trailer and tow vehicle and the benefits are a whole lot more than just being able to have some nice tires for the course without wearing them out on the street.

1. If you break your car you still have something to get home with.
2. You can bring refreshments and not have to leave it lying around on the ground.
3. You can bring company that can make beer runs...or perhaps to get parts...yeah that's what I was thinking.
4. You can have something with more room to change into your driving gear (shorts and T-shirt look funny with that helmet).
5. You can bring more tools than just a set of sockets with the rounded out 9/16" socket and the bent 1/2" combo wrench.
6. With all the other stuff you are bringing then where are you going to fit that air compressor in the vette if you don't drive something else too?
7. Plus, you'll have another vehicle to make beer runs...or did I mention that?

 

I was thinking about pulling a small trailer with the vette. Putting the car on a trailer kicks it up a huge notch in the expense department but would be nice.

I'm not about to buy another new big vehicle now so that's not an option for me. What the hell am i going to do with a big as SUV or truck? It's not like i work for a living and need one.

Now, using that money I would be spending on a tow vehicle on a new Saturn sky and roll bar? Hummm.....sounds like more fun to me.

 

hey jim, i recently cut out a large section of the innerlining of my hood (for clearance) and it doesnt seem to flex much more than before. now that im running slicks at the track (1/4) i feel there is a much greater chance of not coming home on my own . so i rigged the tractor trailer and used a friends truck for the 75 mile treck to moroso in west palm beach. trailering is a pain in the ***. twice the stuff to worry about. twice the tolls much more gas. so i traded the slicks for a set of et drag radials and its back to driving. if it breaks ill call AAA and come home for free as they now tow the first 125 miles without a charge. people were laughing at me cause we looked like the beverly hillbilly race team see attached.

 

did you leave the stock latch mechanism?

 

Thanks for the heads up regarding the Steeroid's bracket!

Am I understanding correctly that it's only the passenger side that causes problems?

Any details appreciated...

Doug

 

I have both and can tackle that (Hi Evan, when did you move to WA?)...

The C4 has the following improvements...

a) A way stiffer structure.
b) Better Steering (front steer rack)
c) Lower Unsprung Weight (aluminum suspension and brakes).
d) Has Anti-Dive and Anti Squat (allows softer springs for better performance in the rough stuff)
e) Allows for more Caster up front, better directional stability.
f) Can run wider wheels without modding body etc.
g) ABS!
h) In some cases factory coolers (PS and Oil).
i) More gears (stock).

..that should cover the main differences.

Doug

 

Have you guys thought about safety wiring some of the suspension bolts?

I've been doing some reading about building a track motorcycle... seems like a good idea on them, maybe good on ours too?

 

I will safety wire most of the bolts. The biggest trick to safety wiring is getting a GOOD safety wire pliers, not the cheap chinese stuff on ebay. A good pliers will run well over a 100$ and can do left and right hand windings.

 

Drove Mt. Tremblant on Thursday. Again another fun fun time. I'd like to get more C3s involved.

Will post picts if i can find some. I need to get a video setup.

 

Hey turtle, how did last Thursday go? Do you have your new shocks in and did they make any difference?

I just got back from running the morning session and doing a little skid pad testing. I'm still having issues with the engine but overall it was fun and I learned a bit more. Some guys from Unique Performance were out there with their Eleanor Mustangs and their new Foose Mustangs and Foose 69 Camaro. They are nice looking cars but they drove like girls (no offense to the ladies but you get my point). The Camaro had sticky R compound rubber on it yet they babied it in the corners. It had to have had a 572 in it because after sleeping in the corners it would easily pull away from me in the straights only to early brake into the following corner.

Anyway, skid pad testing was very informative. I haven't distilled the data yet but initial results show a rough average of around 0.95g and a peak of 1 to 1.08g on street tires. The peaks really aren't meaningful but it's nice to see it anyway. This is with a slightly revised roll center yielding a more aggressive camber gain. Next time I'll have it all the way. What I find interesting are the tire temps. Here they are.

With 1.5 degrees of negative camber
.........LF.....................RF
157..147..118......134..130..121

.........LR.....................RR
106..104..100......109..108..120

This is with about .75 degrees negative camber
.........LF.....................RF
216..181..120......127..130..115

I find it very interesting that even with all that negative camber in the front it is still not enough. The body and tire are clearly rolling to the point where the outside edge is taking more of the load. It will either take more neg. camber or less body roll to get the temps more even.

 

[QUOTE=burners]Hey turtle, how did last Thursday go? Do you have your new shocks in and did they make any difference?
.[/QUOTE

Shocks did not make a noticable difference. The 17 inch tires are the only thing i've done that has been noticable.

I did spin the car once but kept it on the track.

 

They are adjustable, correct? Have you experimented with different settings? Remember, they are really only going to make a difference in transition.

I almost spun yesterday. I had the rear hanging way out for a while.

 

Not a lot of quick transitions on a road course. Shock probably a bigger factor for autocross.

I have them on the stiffest position.