hunting for grip

[vagen]

As most of you know I use my RX as an autocross toy. I have noticed more and more the cars that are beating me have bigger tires. I am losing due to lack of grip in the corners (mind you we are talking at g levels that no normal street car ever sees). I don't see how I stand a chance against a 1600 LB rabbit on 255/13 hoosiers when I have 205 13 ra1s. Its like trying to catch a real live rabbit they change direction too well. Any suggestions will be weighed against the arbitrary budget but are welcome.

 

 

rant/

[Turbone]

Your just going to have to bite the bullet and do the 5 lug swap.

That opens a big window for wheels/tires and suspension options.

[vagen]

I know and I have a pair of new WRX struts for it too

[Turbone]

Upgrading to XT6 swaybars helps a lot also.

[WASHroad]

Does everyone run open diff's? What if the rear has a locker in it so both rear are bitting? Just a thought, new here but that came to mind.

[JWX]

That car already has a 20mm front sway bar on it. You're running into what me and Will did when we ran them. It's pretty much either 5lug swap time, or look into wider 4 lug stuff.

[JWX]

Does everyone run open diff's? What if the rear has a locker in it so both rear are bitting? Just a thought, new here but that came to mind.

 

Rx's already have a rear LSD and the one in that car was nice and tight when I had it.

[vagen]

On top of the 20mm front bar I added an xt6 rear bar. I just need more rubber. I'm going to have a look at a wrecking yard that has a few lift backs here and see if they have any xt6s.

 

I tested the torque brake away on this diff and it was in the 90-95lb/ft right where it's supposed to be

Edited May 15, 2010 by vagen

[carfreak85]

CAMBER!!! Actually, make sure those RA1s are new. As is less than 5-years-old. The tires are the single most important and impactful thing you can do to improve handling, then start looking for things to replace.

 

The factory suspension geometry is not all that bad. Besides a serious lack of camber and caster, there is pleanty of travel, there is zero scrub-radius (at least on EA81s) and the ity-bity wheels/tires and brakes all keep unsprung weight extreamly low.

 

Your list of mods to do:

 

1 - Best tires you can find

2 - Lightest wheels you can find (The enkei wheels in my avatar are 8 lbs per corner.

3 - You have camber plates, right? If you're not around 2-3* static front camber and 1-2* static rear camber, you need more.

4 - If you are allowed to strip the car, do it. Weight kills and compared to a 1600 lb VW rabbit, you are about 1000 lbs too heavy to win... Sorry.

5 - If you want more oversteer, put on the smallest front and largest rear anti-roll bars you can find. If thats not enough, simply pull the front bar. Still not enough? Put on a second rear bar.

 

This info is based on my own personal AutoX experience and on my Vehicle Design degree.

Edited May 17, 2010 by carfreak85
More info

[vagen]

CAMBER!!! Actually, make sure those RA1s are new. As is less than 5-years-old. The tires are the single most important and impactful thing you can do to improve handling, then start looking for things to replace.

 

The factory suspension geometry is not all that bad. Besides a serious lack of camber and caster, there is pleanty of travel, there is zero scrub-radius (at least on EA81s) and the ity-bity wheels/tires and brakes all keep unsprung weight extreamly low.

 

Your list of mods to do:

 

1 - Best tires you can find

2 - Lightest wheels you can find (The enkei wheels in my avatar are 8 lbs per corner.

3 - You have camber plates, right? If you're not around 2-3* static front camber and 1-2* static rear camber, you need more.

4 - If you are allowed to strip the car, do it. Weight kills and compared to a 1600 lb VW rabbit, you are about 1000 lbs too heavy to win... Sorry.

5 - If you want more oversteer, put on the smallest front and largest rear anti-roll bars you can find. If thats not enough, simply pull the front bar. Still not enough? Put on a second rear bar.

 

This info is based on my own personal AutoX experience and on my Vehicle Design degree.

 

I will respond to these in order if I can

 

1. I am currently running RA1s sized 205/60/13 currently these are the best I can afford (Thanks JWX)

 

2. I am running the same wheels as you have in your avitar.

 

3. I do have camber plates that give me -2.3deg camber front and -1.5 rear

 

4. I do outweigh the rabbit but I have 70-80hp on it too

 

I have 20mm bars all around and the car rotates beautifully no understeer and mild oversteer with lift off snapage if needed.

 

My quest for grip is focussed on getting enough wheel to handle wider tires. wider tires=more grip more grip=more speed into and out of corners and faster times.

If I could fir 315 tires I would

Edited May 17, 2010 by vagen

[Gloyale]

Buy some pugs and and go to a low profile tire.

 

anywhere from a 225/60/14 to a 265/50/15

[hatchsub]

I kno they made 13x6 inch Enkeis for our cars but good luck finding a set. I think Carfreak has been searching for a long time for a set himself so you would probably have to fight over em.

 

As for your suspension setup your running the same swaybars as me but im still running "stock" springs and struts. I need to go stiffer front and rear if i want this car to actually handle to its potential.

[Qman]

Buy some pugs and and go to a low profile tire.

 

anywhere from a 225/60/14 to a 265/50/15

 

Pugs are too heavy and not wide enough. The only answer is 5 lug or custom built wheels.

[vagen]

Qman that is the conclusion I am coming to...

 

 

If I go 5 lug there will be three sets of wheels going up for sale...... 2 sets of premiums and one set of Enkies. the enkies have used Toyo RA1s and one set of premiums has BFG comp t/a Legend series all in 205/60/13

Edited May 18, 2010 by vagen

[carfreak85]

My quest for grip is focussed on getting enough wheel to handle wider tires. wider tires=more grip more grip=more speed into and out of corners and faster times.

If I could fir 315 tires I would

 

Horsepower is meaningless, especially when you have to turn. Build a lighter car and you will win. Witness any Lotus, Ariel, Caterham, Westfield, or any other little-bity car. They clean up Ferraris, Lambos, Koenigseggs, Gumperts and Nobles.

 

I'll be generous and assume you have 150 WHP. @ 2600 lbs you're pushing 17.3 lbs per horsepower around the track. Your buddy in the rabbit, assuming your weight and HP estimates are correct, is pushing 16.4 lb/hp. He will still be faster.

 

His little tires are not working as hard as yours. There is a reason the Lotus Elise has 175 width front tires. Drop some weight and your lack of grip will become less of an issue. Move some of the weight off your front end, and the grip will improve further. Shoot for something like 52% front/ 48% rear weight bias.

 

The 5-lug conversion might bump you into another class, so read the most recent edition of the rule book carefully to see if that kind of mod is allowed in your class.

[vagen]

The rabbit is not running little tires he is on 255/45/13 Hoosiers that stick out a mile. I think I'm going to end up on Hoosiers too because I can get light 5x100 15s that will handle wide tires. This is of course after the five lug swap

[carfreak85]

the 5-lug conversion might bump you into another class, so read the most recent edition of the rule book carefully to see if that kind of mod is allowed in your class.

 

+1

[vagen]

in FSP I am allowed to upgrade to bigger brakes providing they came on a similar chassis and are a "bolt on" so the XT6 is perfect

 

FSP requires full interior but other than that anything goes. The only thing I'm not allowed to do is an engine swap that would put me in SM.

Edited May 19, 2010 by vagen

[Gloyale]

Pugs are too heavy and not wide enough. The only answer is 5 lug or custom built wheels.

 

There are some nice alloy pugs.

 

Or........

 

redrill hubs for six lug and go alloy 14",15", or 16":grin: