VikingTrad3r

Hi All. I'm a regular over in the C4 section. Loved these cars from when I was a kid. The only thing I cannot stand is the 80's rims.

Getting ready for my first season on the track, and some autocross events. I have zero experience and I'll be easing into it, with lots of coaching from the passenger seat.
I currently run c6 base 5 spokes on my c4, using the c6 tire size.

I need new tires, and would like to buy a tire that will serve me well as a street tire and will handle a beginners level of track events. I have a lot to learn so I do not need a dedicated set of track tires yet as I would be wasting them. I will be keeping my c6 rims as my track rims (unless there is something inherently dangerous about these particular rims on the track?)

So here is my question:

Should I match the replacement tire size to the same diameter of the original c4 tire? The width in the rear is going to be a tad bit wider, and the width up front is actually a tad bit narrower.

I was going to ignore the width differential, and was going to match the diameters of both wheels to the OEM diameters, buy altering the tires from what the stock c6 tire size is.

Curious if the group here has any counsel or guidance for me in this aspect.

I suppose another question is that I am using proper billet hubcentric adapters for my wheels to fit on my 86. I should probably ask if that is suicide. From what I have read, proper adapters are fine but go ahead and let me know what you guys have for experience there too. Thanks.

VT.

VikingTrad3r

Followup question, I'm looking for a set of stiffer springs from an 84 z51, and when I swap those, I'd like to lower the car. Should I keep the rake?

dclafleur

The adapters are fine, just make sure you check the torque on the adapters and then again on the wheels before you run. Do you have the tire sizes you're wanting to run picked out? Limitations in finding a matching set of tires for staggered front and rear sizes tends to dictate tire choice as much as anything else. Finding wide tires in 17's for my C4 is a bit of a pain and I went square on my C5 just to make it easier finding a tire I wanted to run. If you lower the C4 try to keep the rake, they're actually pretty well balanced despite having a big lump of iron out front.

mattastick

I actually have a perfect set of wheels/tires for you sitting in my garage that I'm trying to sell. C5 front wagon wheels with 275 width Conti ECSs square. They were an awesome daily/rain setup on my C5 (pulled .98g lat in the wet on concrete), and will survive reasonably well at entry level pace on a racetrack. Going square means you can rotate to get better life out of the tires, which is a big plus.

Tomswheels

Sox-Fan

Before you make any wheel, tire, spring, or shock decisions have you decided what class you plan to run in? Class limitations might change your wheel/tire and or spring decisions.

MatthewMiller

So generally I lead with the same advice that Sox-Fan just posted. However, for VikingTrader I'm understanding that he wants to start with something for dual-duty and something that may get replaced later if/when he gets more experience and picks a class, etc. IOW, I'm understanding that what he buys now may not be the last set of rolling he'll ever buy for competition. That is pretty freeing. Also, I like mattastick's approach and would advise you to buy his setup, but you already have wheels you want to use. So...

I'll knock two questions out right away. Don't worry about the adapters, they should be fine. I'm actually a bigger fan of spacers (if the wheel studs are long enough), but these will be fine. Also, I would try to stick to similar tire diameters as OE to the C4: 25.5"-26.1". Am I right in assuming your wheels are 18x8.5 and 19x10? If so, then your front tire size would be 245/40/18 and the rear would be 275/30/19. Good news: the Continental ExtremeContact Sport is available in those sizes. This is a great street-and-autocross tire. It has excellent dry-weather grip (maybe 1 second off the best 200tw tires on a typical course), and it's the best wet-weather tire you can get short of a Hoosier rain tire (not legal in most classes). And these are real-world street tires. The only thing they aren't good for is cold/snow/ice: continental says not to drive below 40*F, although I think they'd be safe down to 32F. Again, this is the same tire that mattastick is offering, and I agree with everything he said about them.

As for lowering, I'd say generally to keep a small amount of rake in the car, but emphasis on the word "small." I'm not sure it's super critical in these cars. In an early C4 suspension like yours, the rear has a fairly high roll center, which isn't ideal. So don't leave the rear up in the air very much - the lower you run the rear, the lower the RC and the less jacking effect you'll get in corners. Also, you didn't ask about alignment but I'm going to say something about it anyway. In the rear, I don't know what a stock early car can get for camber but I'd shoot for -1.0 degree (that's negative) if you can get that. You want zero toe in back, or maybe 1/16" toe in. Up front, for a dual-duty car you should probably run -1.0 to -1.5* camber (again that's negative camber), and all the caster you can get at that camber setting. Then run zero toe or again, a teeny amount of toe in. That alignment should be a reasonable compromise between street and autocross duties. If you get more serious about competition, you'll want more negative camber (if the rules for your class allow it).

My last advice: you're approaching this the right way: get a set of tires and start building experience. Run for a year or two and start pondering what class you want to aim for in the long term. Then we can come back and have a discussion about other mods and other whee/tire sizes!

mattastick

Pricing out those sizes on TR: $840 for the set. I'd sell my set for $450 and they have ~2k miles on them + 6 autocross runs at Nats. That leaves a lot more money for entry fees so that VikingTrad3r can get to more events and get more seat time. By the time he wears out the Contis, he'll be ready for a better tire.

VikingTrad3r

mattastick

Correct. All 4 wheels are 17x8.5" wide, and apparently have a +58mm offset. They also have TPMS installed at the moment, which I don't think you need, but figured I'd at least mention it.

VikingTrad3r

Thanks for the replies guys.

Question though, why would I want a set of all season tires for the track? Wouldn't a dedicated set of track tires be more of a summer / track combo rather than an all season ?

Seems like a good price offer, just wondering if thats really the best way for me to go.

mattastick

The Conti ECS (Extreme Contact Sport) is an evolution of the DW, which is a Max Performance Summer Tire. Here's the TR page: https://www.tirerack.com/tires/tires...eContact+Sport

They're going to give up performance to a 200tw or similar aggressive tire, but they're also going to wear significantly better and last a lot longer. Plus you won't be screwed if you run into a rain storm, as they're a phenomenal wet tire. Here's a nice tire test by Andy Hollis with the tire: https://grassrootsmotorsports.com/ar...laren-mp4-12c/

MatthewMiller

Yep. These are not all-seasons by any stretch. Not only would they not perform well in snow and ice, the company specifically says not to drive them in cold temps because you could crack the compound. They are summer max-performance tires that are a notch below competition-oriented tires (the Rival S and RE71R in 200tw, and the Hoosier A7) in speed, but are legitimate street tires that you can comfortably drive around on all the time (except winter). The bonus is their outstanding wet-weather performance. The other tire that's in their range of performance is the Michelin PS4, but it's more expensive. They are recommended by us for you because you aren't looking for a dedicated track tire.

You could use Rival S or RE71R tires and drive them on the street. They just won't last as long, and they won't be as good for as long when it rains (they are okay at full tread, but that tread depth isn't very deep and doesn't do so well in rain once it's half gone). And overall, they won't wear as long as the Continentals. It's all just tradeoffs at this level: a competition 200tw tire is faster but not as versatile on the street and in the rain as the Conti, and not as long lasting.

Solofast

Pretty much agree with all that Matthew is saying his alignment is right on. You can go to a tad bit of toe out in the front for track or autocross but it will eat tires on the street. One thing that you can do is crank about a half a turn on each toe link from a zero front toe alignment and that will get you a bit of toe out for turn in, and then you can crank that same half turn out for street driving.... Would add that you can't lower the front unless you get different springs, so you are limited in that you can't lower it much in the front and if you keep rake level or a bit higher in the back for track duty you're pretty much stuck with stock height in the back.

As far as tires go also look at the Hankook RS4's. They are really a long living tire and have decent amounts of grip for a real "street" tire. While the RE71's and BFG's are faster you won't get any street miles out of them. I've had the RS3's for both street and autocross and got great life out of them. If you're doing a track day you can't go wrong with them.

As far as sizes go, don't consider anything less than a 275 section width. Less just won't work on a C4. More isn't really better or faster. We went as high as 305's and it wasn't really faster on a stock class car, but less than 275's was really noticeable. Wider tires need less pressure to work properly and that means more negative camber is required to keep them from rolling over. With a C4 you're lucky to get a half a degree in stock class form in the front. You'd need offset bushings or mods that aren't legal in stock to get bigger tires to work. Although you can fit them you could go as big as a 285 but I don't think that I'd go wider than that.

Finally, C4's like a square setup. Don't go with wider tires on the rear. If you do you'll find that you need more rear roll stiffness in the back to balance the car and this will lead to jacking in the rear suspension, so don't bother trying that. It doesn't really work. If you stay square you can rotate tires front to back and this will maximize tire life...

VikingTrad3r

Ok so when i piy the base c6 rims on my early c4, 245 front, 285 rear. for STREET, i havnt done any track with it, i noticed that the car felt more "modern"...meaning it just felt. etter driving on the street. Apologies for use sotp and qualitative descriptions.

Perhaps it was more the lower profile tires. it just "felt tighter".

So i thought staggerd was the way to go.

But i have read from multiple places that the c4 "likes" a square setup. Especially for track.

im leaning towards the c5 wagon wheels in square 4 setup above if they are available, but im curious why my 86 and 87 and 85 "felt" so much better taking the oem c4 rims off and putting base c6 on?

Bare with me, im new to thinking in terms of suspension but i am grasping it slowly as guys are helping me learn.

Solofast

Of course it "feels" tighter. Lower profile tires make the steering much sharper. I went from 70 series tires on my wife's 626 sport coupe in the 80's to a set of 50 series low profile Goodyear's (which were notoriously "sharp" handing tires) and the difference was like night and day. It went from being a nice sedan to driving like a go-kart. I let a friend from the Proving Grounds drive the car and even he was amazed how it turned a pedestrian sports coupe into a slot car.

Never confuse "feel" with fast... Feel makes you think you're fast.. Grip wins races.

In the 80's I had an RX-7 that had 70 series tires on it and with the then fastest Yoko's on it, it was awful in how it felt, the steering was rubbery and you had to anticipate like crazy to get the car where you wanted it to go.. But it was a Divisional Champion and took me to a 2nd at the Nationals... It had tremendous grip and you could fly in that car. You had to put in huge amounts of steering lock in slaloms and offsets but you could fly thru them once you figured it out..

Tires have come a long way and lower aspect ratios make all tires much better in regards to steering feel, but never go by feel.. Lap times don't lie.... It's up to the driver to get the car in the right place at the right speed on the course, if you have big grip you just have to figure out how to drive what you have quickly. Having a car that "feels" good makes it fun, but if the grip isn't there you won't be fast.

You really don't know how a car feels until you get it to the limit. The setup with the C6 wheels and tires will feel a lot sharper, in handling and might feel pretty good even at a relatively spirited driving conditions. But if it falls flat and pushes at the absolute limit on the track, then it won't be fast, then it doesn't work.

What you want with any setup is just a pinch of understeer at the limit, that is you want to be able to get rid of that understeer with a bit of a lift, and be able to power hard out of corners, but if you have massive understeer you won't be fast, and if you have much oversteer you'll be slow because you can't use power to come off of corners.

Shortcutsleeping

There is a lot of REALLY good advice in this thread, but I don't believe this statement gets enough credit.

Starting out, I think everyone who is climbing the speed pyramid will agree that a LOT of track time is what is needed. Making the tires and wheels the same size means you can put any tire/wheel in any position on the car to even out wear and extend the usable track life (sometimes dramatically) of your tires.

Sure, later on when you're really fast and searching for bits of time, going to position-specific tires/wheels can help you there. But in the beginning seat time is king and a square setup can reduce the cost of doing that. Regardless if you buy the setup from the person I quoted, my advice would be to seriously look at a square setup if possible.

Costas
cars and such...

VikingTrad3r

pm sent

jefnvk

I just went through the same decision, having a C4 with C6 rims. I'm keeping the C6 rims for street duty (like the looks better), and bought a set of stock sawblades. I went back and forth between that and square18s, but trying to build to a couple rulebooks keeping it stock size for now was easiest.

I did choose the Conti ExtremeComtact DW. They do stack up well in reviews against everything but Pilot Sports and true 200TW options, but I also get a substantial discount that made those differences fairly minimal as well. If I didn't, I probably would have thought harder about some of the 200TW if I were planning on being competitive (full disclosure: I pretend I am, I'm not).

Worst case with this line of action, in a year I upgrade to 18s and the 17 Contis become dedicated wet tires, wheee they supposedly wipe the floor.