Hi Folks


I'm working on my setup for my SRF, planning to take it to Limerock for a DE event on 4/12 for a test day to see how it runs after my "Frame off" rebuild.

Two items that I am not completely sure on for the setup and was looking for some advice/guide.

1. Caster...I have a spec on the caster setting. But what is a good way to measure it? Not really sure how to do this accurately.

2. Sway Bar, i've seen references to "stiff" and "soft". What are those and how are they measured? I'd imagine you need to adjust the heim joints somehow? I am going to run it with a new set of Penske shocks which I'd like to run somewhat "stiff" since I prefer a little more stiff handling than a looser suspension.

Thanks for the tips in advance!

Steve,
Caster is tricky. You need a camber gage and an accurate way to turn the wheels +- 20 degrees (usually). Perhaps there are some other trick ways to do it.
Sway bars are easy. Loosen the block that clamps on the sway bar, and slide it to the desired position. Towards the end of the bar is softer (about 1/8" is Min.) more stick out is stiffer. I started at 1/8" and have worked my way to about 1/2" last year. Don't know what Max is. I've heard that some bars are marked.
What did you do for your fuel pump?
Good luck with the early testing.

Hi!

I have a camber/caster gauge....was coming up with some way to do the +/-20 degrees thing which is what I read about...was hoping there was some trick way. I set it last year, but I wasn't really happy with any kind of accuracy, although it "seemed" fine

Thanks on the sway bar! That makes a ton of sense now!

On the fuel pump, part# eas E8312 etched in the pump so I was able to get a local one at Napa.

Really looking forward to getting it out for testing! It seems so much better already and i've only been spinning the wheels by hand and such, really excited to try it!


- steve

xvracer wrote:Steve,
Caster is tricky. You need a camber gage and an accurate way to turn the wheels +- 20 degrees (usually). Perhaps there are some other trick ways to do it.
Sway bars are easy. Loosen the block that clamps on the sway bar, and slide it to the desired position. Towards the end of the bar is softer (about 1/8" is Min.) more stick out is stiffer. I started at 1/8" and have worked my way to about 1/2" last year. Don't know what Max is. I've heard that some bars are marked.
What did you do for your fuel pump?
Good luck with the early testing.

you can measure the caster angle directly by using a digital level on the uprights. Unless you want to put the level on the bolt heads that hold the "cage" to the upright a piece of tubing or some type of spacer is required. If that doesn't make sense, I'll take a picture in the next few days.

steve kramer wrote:you can measure the caster angle directly by using a digital level on the uprights. Unless you want to put the level on the bolt heads that hold the "cage" to the upright a piece of tubing or some type of spacer is required. If that doesn't make sense, I'll take a picture in the next few days.

I've seen this technique. It seems easier and more reliable than the 20 degree thing.

If you have a digital camber gauge, the angle of the gauge is the 20 degrees. By holding it sideways against the wheel you can "eyeball" the wheel angle against the frame so that when the gauge is parallel to the frame you're at 20 degrees. Take that camber measure, then repeat in the opposite direction, then subtract that camber setting from the camber measure, then multiply the result by 1.5. Where people get into trouble is when they run a lot of caster and the camber goes from negative to positive and they fail to take that into consideration when doing the match.

At one time I built a 20 degree template that went against the wheel and used the toe-strings as a reference line.

Or in a pinch, I use a free iPhone measure app against the bolt heads on the uprights.

Of course, all of this depends on the car being on a level surface.

BTW, if you're going through all this effort, are you also checking bump steer?

Also, if you're coming from Koni's note that the Penske's at full soft are nearly as hard as Koni's at full stiff, so you might want to start in the middle and work your way to the right level of stiffness. Most noticeable effect if you run too stiff in the rear is the car will turn in really "well", sometimes more than desirable, and the car will lose contact patch in the rear under hard braking.

On the sway bar, do you have a reference point, or are you starting from scratch? Given the front and rear tires are the same size, we generally have started with full stiff front bars (note that there's a difference in pivot points depending on which way the block is positioned so that affects the stiffness as well.) From there I'd suggest starting pretty soft in the back and working your way stiffer until you achieve a good mid-corner balance, then balance entry/exit with the rear/front shocks as needed.

I wasn't aware that there was a legal after-market version of the fuel pump.

That makes alot of sense using the digital level to measure the caster! I had some setup I was using last year for the +/-20degree, but I really question its accuracy..

i do have a laser bump-steer gauges and and set of scales, so I've gotten decent at going through the setup process, plan to recheck bump-steer this week.

the sway bar does have some marks on it, but now it makes sense alot on where to start and how to setup the say bar.

i was going to run the Penske's somewhere in the middle of their settings, as it did seem like their chart said that the "soft" on a Penske was "hard" on a Koni.

On the fuel pump? Someone else on this forum said they could get it at a local parts store. I dont know? The one on mine seemed to match an Artix E8312 pump? It's spec enough for a "DE" event...I'll call my CSR and double check. I'd HATE to actually win race and get bounced for a fuel pump

- thanks!

I have used steering plates for caster for a while now, but I keep seeing differing calculations on the 20 degree measurements. Is it truly a multiplicative factor of 1.5 or is it 1?

Also, I haven't seen a SRF in SOWDIV with a full stiff front sway bar in, well, ever. There are wildly differing (often by area) baseline setups.
My front sway bar is always .5" off of full soft or softer (it was off the bar soft until the GY's came along).

Denny

It all depends on how you like the car to feel. With the Yoks, I always liked stiff set-ups and the car a little twitchy. With the Goodyears (and the big front contact patch), I want to induce some under-steer into the front and I do that with a stiffer front sway bar setting, but 10 or 11 of stiff on the front shocks. It comes down to driving styles and what you like. And mileage may vary...

DaveP

For caster formula, here's the SmartCamber reference manual:
http://www.solotime.info/dotnetnuke/Por ... manual.pdf

I suspect the difference in setups on sway bars is affected by tracks. On the West coast, the tracks are pretty high grip, with high speed corners, and there's more front grip with the larger GY fronts, so settings have moved softer in the back vs. stiffer settings all around in the old (radial) days. On lower speed tracks with flat, pushy corners I suspect that the softer front setup works to rotate the car (or if you like a really loose race car).