DavidNJ

Most of the front bar stock class threads talk about the AP1. Here I'd like to focus on the AP2.

The anti-roll bar, one, either front or rear, is the only change allowed in mechanical springing. There are a couple of tire size combinations used but 225/255 and 245/255 seem to be the dominant choice; I will have 225/255. There are also a variety of tire brands with Rival, RS3, V2SS, and RE71R being the common choices. I'll be using RE71Rs.

I have on autocross on the car. It had the original RE050's that came with the car in January 2004 (I am the original owner). Before the autocross they had 13k miles with some early signs of cracking in the tread. At the end of the autocross deep cracks the circumference of the tires had developed in each circumferential groove. Let's say they were shot. Otherwise the car felt ok...the shocks which crash into every pothole and bump in the street were reasonably firm, the balance seemed ok given that the limits were probably much lower than they will be with the new tires.

Sidebar: I ran Yokohama A008Rs on my 1986 MR2 back in...1986. Half or at least the other third of that tire was a slick. Although this was my first autocross in 12 years, I've done over 150 plus SCCA and oval track racing.

A stiffer front bar has seemed to be the B Street's most recommended change after tires. However, given that the balance seemed ok I'm wondering if a larger front bar might upset that.

So, what is your experience? How stiff a front bar should an AP2 with stock shocks have?

Sidebar: I will probably use the Karcepts bar. That bar is offered with 4 different 1.25" diameter options: solid, .250" wall, .188" wall (sort of recommended by Karcepts, and starts at AP2v2 bar levels), and a .120 wall which goes softer than stock. There are generally the same torsion springs offered by Small Fortune Racing Gendron bar and since both have solid arms I would expect they have very similar stiffness.

What do you recommend and why?

Thanks,

David

iamxpl

IMHO a front bar is necessary for autocross in an s2k to be competitive. In the past i had a Gendron hollow 1.25 bar set on 3 from softest. On the CR i have the karcepts 1.25 hollow on setting 2 from softest. in an AP2 considering the springs and shocks are softer I would start off on setting 3 and adjust softer as needed. i run a 225 255 set up on hankooks, but lets not get into the tire debate. a lot of this will have to take into account your driving preference. I also prefer the karcepts bar due to the adjust ability and less weight. granted you do not have the ball bearing mounts but.

again im no pro or anything, this is just my experience. maybe Nick B or the other pro's can chime in. i see you're from NJ, were you at meadowlands yesterday?

DavidNJ

Yes....

iamxpl

a bit off topic but i should be setting up a get together for our local group members soon maybe you can come out and chat a bit with us. https://www.s2ki.com/s2000/forum/61-...-s2000-owners/

thats our sub forum.

Forcednduckshn

Hi David,

Come and stop by next time we are both at a NJ event, I look forward to meeting you. I would have been happy to give some advice, take your car for a ride to show you its limits and provide some instruction and feedback on setup changes to the car.

For now I would just focuse on the driving portion and getting to the limit and keeping it there. Then once you are more comfortable, focus on setup changes. I appluad you for your technical questions on bars though:

You will need more bar as the grip levels go up. On the stock, old dry rotted tires, a soft bar will work great But not on the HoosierStones

A stiff bar is great on a stock s2000 for many reasons. Mainly because it keep the rear inside wheel down at corner exit, and because it keeps the front wheels a bit happier at the limit by limiting body roll, alleviating the lack of front camber issue. And the car be manhandled through slaloms more quickly.

I concur with Brian Karwan's recommendation on where to start with bar sizes, though you may need more stiffness depending on your setup particulars and driving style.

Karcepts

My recommendation to David was to run the .188" bar, but only if he's adamant about installing 225's up front. However, my all out race recommendation, which I'm pretty sure my buddy Nick and I agree on here, is to go with the .250" bar on a 245/255 RE71R setup. 95% of our customers on the Karcepts bar are running the .250" wall (in both BS and STR trim).

Forcednduckshn

+1 100% agree.

I also will add that, in all of my past experience, cars with more front tire width needed more bar, which could be viewed as substantiating evidence to support the conclusion that the wider tires (e.g. 245) make more grip, despite the pinch.

DavidNJ

And I have another thread on the tire sizes! Todd, running an A Stock CR with 225/255 tires said in his spec he was using a Gendron 1.25" solid bar at the "4th stiffnest" (3nd softest?) setting. Applying that to Brian's Karcept's bars (which look like a work of art, I could always mount it on my living room wall!), that would put it within the range of both the .188 wall (2nd stiffest) and .250 wall (3rd stiffest).

Another poster in the thread Todd started is using the RE71R 255/40 on the stock 7" front. Not sure if he is A Street or B street, or what anti-roll bar and bar setting he is using.

The softest setting on the .188 bar is very close to the stock bar (maybe 15% stiffer than a 2004, similar to a 2008), the .250 maybe 30% stiffer. Compared to the stock CR bar, Todds setting would have been about 40% stiffer.

That begs the question, what settings on a Karcept of Gendron bar are people using in B Stock with 245/255 and 255/255 tires?


0.188" Wall:
Hole 1 = 349 lbs/in
Hole 2 = 385 lbs/in
Hole 3 = 428 lbs/in
Hole 4 = 480 lbs/in
Hole 5 = 542 lbs/in
Hole 6 = 624 lbs/in

0.250" Wall:
Hole 1 = 400 lbs/in
Hole 2 = 442 lbs/in
Hole 3 = 491 lbs/in
Hole 4 = 550 lbs/in
Hole 5 = 622 lbs/in
Hole 6 = 715 lbs/in

Solid Bar:
Hole 1 = 459 lbs/in
Hole 2 = 507 lbs/in
Hole 3 = 564 lbs/in
Hole 4 = 632 lbs/in
Hole 5 = 714 lbs/in
Hole 6 = 822 lbs/in

DavidNJ

But do they loose anything in response? Do they have issues on the street (I would think most B Streets are also street driven). If 245 why not 255? At what point do they have clearance issues with +55 offset stock wheels?

Karcepts

Hey David,

Please note that the rate settings we have provided are effective rate "at the shock", not at the end of the arms like many are used to seeing. I thought I was helping by converting to rate at the shock for customers who play with aftermarket spring rates, but lately these numbers seem to be confusing too many, and I plan to revise shortly.

Here is some more usable info for now:
- The .120" wall on the softest hole will be ~1.2 times stiffer than a CR bar
- The .188" wall on the softest hole will be ~1.7 times stiffer than a CR bar
- The .250" wall on the softest hole will be ~1.9 times stiffer than a CR bar

With this being said, I know many of our B Street customers float on average around setting 2-3 on the .250" wall center section. But now with these crazy new street tires, guys may be running even stiffer.

Hope that helps,
Brian