Autocrossed my Series 3 Cat today

[sparecr]

First time I have tried autocrossing my Caterham. Yep just as fun as everyone says. But I have one small problem the car is undertired. I ran today on my 13x6 Panasports with Yokohama P400 Touring tires that are at least 5 years old (185/70/13). To say it lightly it pushed a tad. I would like to get some better tires to autocross with. I have a second set of wheels 13x7 that I would like to use for the tires, but are these even big enough to help? Any advice would be nice. Sizes? Brands? Deals? My other problem is I have the typical 2 inch oil pan ground clearance so any loss of side wall height may hurt.

[pi7ot]

In order to find out how far to mod the car you may first have to decide on a few things.

 

To help that decision there are some questions that may need to be answered.

1, Are you in it for fun or are you a competitive sort?

 

If it is only fun then you may be satisfied with 205 55 or 60 series rubber... if you can find it.

 

 

If you are of the competitive sort , you'll run in to a heavy rule set regarding the prep of a 7 for autox.

 

Before you get deep into car prep, you'll need to get a hold of the rule book(s) of whatever sanctioning bodies the car runs under.

 

7s are tossed into 3 classes by the SCCA...

1, Real Lotus 7 in some street prepared class.

2, Clones with engines under 2l in D-Mod

3, Engines over 2L in E-mod.

The latter 2 classes are slick shod with wheels wider than 7", gutted, often bespoilered machines. basically race cars geared for squirts.

 

Your street legal Westie would be classed in D-Mod by the SCCA.

 

Another thing is that if your car was a Lotus 7 and you're the only one in your class, you tend to get bumped into D-Mod anyway. If you have one competitive bone in your body, but don't want to convert your street car into a full bore racer, bumping will get old, fast.

The classing depends on sanctioning body.

As a 7 owner who wants a street legal fun machine, I ignore Autox and attend time trials, high performance driving schools and track days at Road race courses within a 300 mile radius of my home.

I drive to the track on 14 or 15 inch R compound radials, A higher roll bar, a racing shell and 5 point harnesses.

 

The Autox milieu is useful for you to get to know your machine at the limit at low speeds, but the classing structure for the 7 does not favor street legal machines.

 

if you like the autox, the road course environment is potentially better, with more time in the car at whatever limit you are comfortable with.

 

m

[Kitcat]

I do exactly as Pi7ot does. But, I think auto-x, wh/I have somehow never done in my Cat, wld be a great starting place to learn the car-you already discovered it pushes.

 

Most Se7ens seem to have over-steer, not under-steer (pushing), and the common cure seems to be to add wider real tires. You have the opposite problem. Understeer can be fixed with a stouter front roll bar (wh/makes the rear stick better), or a smaller rear bar-same effect. Maybe you just need an alignment?

 

Tire pressures can be used to fine tune grip. Drop some out of the fronts (in 2 lb increments) and see if that helps. Upgrading your tires to something with more grip wld not remedy the push problem as the issue seems to be imbalance between front and rear grip. I run 205 Toyo RA1's all around and the car balance as set up is perfect: I can steer with the throttle and the steering wheel and get the car to do pretty much what I want, within limits.

 

Mike

[snookwheel]

I run 13 X 10 Diamond Racing Wheels with Hankook Ventus 240/570 C91 compound tires for autocross. the sidewall is every bit of 3.75 inches tall, so no ground clearance issues. I buy scrubs. I have seen them for +- $35.00 tire + shipping with plenty of life left. (I'm cheap).

 

The hot set-up (IMO) is the Goodyear R160 12 X 20 X 9.5 tire. Much lower profile. I borrowed a set for my fronts at an event and the turn in was definitely better. The Stalker that placed 3rd at Nationals was running the Goodyears.

[turboeric]

Understeer is often a symptom of entering the corner too fast. When you find the car pushing, you'll need to enter the corner slower and get on the power sooner to induce some oversteer to get it to turn in. Then you can start changing the car. I'd echo what the others have said - learn the rules for your class, then make decisions about autocross tires.

[sparecr]

In my area they are fairly easy with the rules. I just went D-mod. The only other guy that normally runs there is in a VW bug. The Big cars here are CSP Miatas and EVO's. I am in it for fun, don't have the time or money to do a full national race car. I can see track days in a year or two.

 

Yes I enter corners to fast and don't use the brake enough. I ran yesterday with a co-diver who has much more experience and they could only beat me by 5-6 secs. She highly recomended R-comps agreeing that the 5 year old touring tires on our gravelly surface are useless.

 

So any good websites or places to look for scrub tires?

[snookwheel]

This guy has been selling scrubs / used tires for a while and has a good reputation from what I have heard. http://www.jbracingtires.net/

 

Scott

[SkinnyG]

I ran a set of Gooyear R160 (or was it R175??) 20x9.5x13 slicks for two years. On really short asphalt autocross runs I could not get enough heat into them.

 

I'm now running a set of Hoosier R35 20.5x7x13 slicks that feel grippier, and I can get them hotter.

 

I run in D/Mod in a very under-prepped street legal 7. Our events are scored via PAX, where I do not have a chance. I run for the fun of it. Or at least that's what I tell myself.

 

I'd seriously consider running RA1's for everything, and not have to carry a set of slicks to and from events. But.... slicks are addictive.

 

I bought the Hoosiers used, at $35/pair from this guy: http://myworld.ebay.com/ebaymotors/leegrx7/

[pi7ot]

One last tip for auto x or track.

once you get your tyres sorted and the suspension the way you want it, be sure to add 2psi to the rear, or take 2 psi out of the front tyres if you carry a passenger.

This will prevent embarrassing terminal understeer.

BTDT :jester:

 

m

[Boxologist]

John- if ur driving to the event on the same wheels/tyres, 225 width toyo r888 or RA1. if u have been trailering the car, bumping to either the Hoosier (purple crack) or goodyear slicks will be very fun.

[L8 Apexr]

I do exactly as Pi7ot does. But, I think auto-x, wh/I have somehow never done in my Cat, wld be a great starting place to learn the car-you already discovered it pushes.

 

Most Se7ens seem to have over-steer, not under-steer (pushing), and the common cure seems to be to add wider real tires. You have the opposite problem. Understeer can be fixed with a stouter front roll bar (wh/makes the rear stick better), or a smaller rear bar-same effect. Maybe you just need an alignment?

 

Tire pressures can be used to fine tune grip. Drop some out of the fronts (in 2 lb increments) and see if that helps. Upgrading your tires to something with more grip wld not remedy the push problem as the issue seems to be imbalance between front and rear grip. I run 205 Toyo RA1's all around and the car balance as set up is perfect: I can steer with the throttle and the steering wheel and get the car to do pretty much what I want, within limits.

 

Mike

 

Adding a bigger bar to the front is the wrong way to go imo(unless your running a stock class vw perhaps),the end that loses grip 1st is the end to soften not make stiffer as its already transfering too much weight.

Soften the front 1st(assumming your alignments in the right place),get as much grip as you can find and once your there than tune the rear with stiffer springs,bar and shock settings for the balance you want.

Always tune the end with the least grip 1st,makes no sense to try and reduce the rear grip to balance out the front without 1st optimising the front.Also if your looking at a different tire I wouldn't spend too much effort tuning with the stuff you have now,sticky tires will need a different alignment and roll stiffness front and rear to get the most out of them.