Event #3 - one of my best

[STLMARSHALL]

I ran event 3 today and the car was better than it ever has been. I did a lot of mods over the winter and am very pleased they have paid off. The car was a tad softer and much easier to control than it ever has been. The fear of it jumping up and trying to kill you is gone. It will still get out of control but it now is so much easier to get back. The NT01's do not quite have the ultimate grip of my old R-comps, but now that I have found some balance I can really push the car to the limit without the fear of it biting me. What a cool feeling to have found the sweet spot.....finally!!!! Today was my 4th best pax finish ever. The other 3 were all on R-comps. Rear tires were rolling over pretty far and needed more air. I never touched them though as the car was so good....I did not want to ruin a good thing.

Here is my current setup: Springs 350F/250R, FFR Konis all set at min rebound, big front swaybar, no rear bar, NT01 275F/315R, 28 psi F / 25 psi R (set cold), LS1/T56 moved 3" forward of stock, 1/4 tank of gas, custom 3.5" exhaust (sounds awesome!).

Here is a video of my fastest run of the day. I still made a few mistakes and could have been faster.

https://www.youtube.com/watch?v=JRgIw4NMS80&feature=youtu.be

[skullandbones]

Nice run! What sort of mods have you done over the winter? I'm interested in autoX and was wondering if you did any mods that might be transferable to the roadster. Your front springs seem light to me but maybe the sway bar helps on that note. I like to hear about any mods that help these cars handle better. I'm still at the "it could kill me" stage.

Thanks,

WEK.

[Jeff Kleiner]

Good on ya' Mike! Thanks for the report and rundown of your setup. As you know I'm on NT-01s this year and am starting to get them figured out after 2 events. Interesting, and kind of reassuring, to see that you run a 3 pound split; I have found that ~2.5 pounds works well for my setup which is a change from the Kumho XS which was generally 1 to 1.5 pounds. You are running somewhat higher pressure than I am (mine are usually in the 18-22 range) but I am on significantly more spring with 750# in the front and 500# in back. If I have time before the event next weekend might swap to a bit less spring in back to see if it tightens it up. Because of the additional front grip from these Nittos the car is a little more loose than it was on Kumhos. I prefer loose to a push but am curious to see where something like a 350 in the rear puts it. If it pushes though I'll yank them out so quick it will make your head spin! I'm liking these tires...last event I was top 5 overall and on a 50 second course was just 0.288 behind the fast guy running on Hoosier A6s!

One of these days we've got to meet up and run together...do you ever go to Rantoul?

Cheers,
Jeff

[CraigS]

Is that 350 for the front springs a typo? Even way back in MkI days the FFR standard was 450 and that is soft for autocross.

[STLMARSHALL]

Also had a real tank slapper on run #3. Here is an external view from grid and an in car video of the same run.
Run 3 event 3, out of shape across the finish - YouTube (https://www.youtube.com/watch?v=csz0H_xqPEM)

https://www.youtube.com/watch?v=f57g2BIc-4I&feature=youtu.be


WEK I am not sure you can completely duplicate what I have done as my engine + trans has been moved forward 3". I have not weighed it yet but I am guessing it will come in at 50/50 bias empty and 48F/52R w/driver. I have found the bias moves about 1% per inch the engine is moved. With my original 302/TKO 500 setup I was at 45F/55R bias w/driver. That being said tell us what your car is doing that you don't like and we can try to help you fix it. In my case my car would oversteer badly anytime I was turning. Here is an example of how quickly it happened: https://www.youtube.com/watch?v=ztlSTYh69V0

Jeff I am not sure the 3lb split was optimal. The front tires did not roll over much at all at 28 psi. The rears were rolling over too much (well into the diamonds) and needed a couple of pounds....but because things were so good I did not want to make any changes that might throw things off. I originally decided to go high on the front to try to induce some understeer and planned on dropping the front pressures to fine tune the balance. In the end the balance was so good I never touched the tires all day. I have no idea what pressure they crept up to once they heated up. I don't think I could have dropped the rears to the 18-22 range without tearing up the sidewalls. I have never been to a race in Rantoul but it sounds like fun.

Craig the 350# in front is no typo. I know it goes against the grain and most advice given, but it worked well. I just went out and checked my zip ties on the front shocks to confirm the success. With the 500# springs I always had about 1/2" of unused travel, and now with the 350's that is down to 1/4". I am amazed that with that light of spring up front and a 50/50ish weight bias that the fronts never bottomed once with the severe thrashing I gave them on Sunday! The zip ties do not lie though. On the street the ride is much improved and the front does much less pogoing. On the track the bumps that used to bounce my head off the roof now actually gets soaked up by the suspension and the car stays much more stable.

Watch the video and you can see that the body roll is still controlled. I run a 7/8" front sway bar off a Ford Explorer and none in the rear.
https://www.youtube.com/watch?v=csz0H_xqPEM

I race with some pretty fast cars that still have some body roll:
http://i464.photobucket.com/albums/rr2/mmarshall01/Rick_3_alt.jpg (http://s464.photobucket.com/user/mmarshall01/media/Rick_3_alt.jpg.html)

http://i464.photobucket.com/albums/rr2/mmarshall01/DSC_3410.jpg (http://s464.photobucket.com/user/mmarshall01/media/DSC_3410.jpg.html)

[skullandbones]

How did you come to the conclusion to soften the front coils that much? It doesn't look like you have much body roll at all. So the explorer sway bar is responsible for all that? In other words: were you getting excessive roll last season without it? I'm trying to figure out how you came to the combination of stuff you have now. BTW, I haven't made my first AX so it's all theoretical for me at this point. But I want to optimize the suspension as much as I can for the day that it does hit the track. I've done some mods to the front suspension to bring the geometry closer to the MKIV and Spec Racers but nothing with the spring rates or sway bars and such.

Thanks, WEK.

[STLMARSHALL]

How did you come to the conclusion to soften the front coils that much? It doesn't look like you have much body roll at all. So the explorer sway bar is responsible for all that? In other words: were you getting excessive roll last season without it? I'm trying to figure out how you came to the combination of stuff you have now. BTW, I haven't made my first AX so it's all theoretical for me at this point. But I want to optimize the suspension as much as I can for the day that it does hit the track. I've done some mods to the front suspension to bring the geometry closer to the MKIV and Spec Racers but nothing with the spring rates or sway bars and such.

Thanks, WEK.

The idea came from the fact that every bump I hit felt like a car crash. Sometimes it would throw me out of the seat and dislodge my feet from the pedals. On the track I stopped pushing the car hard across the bumpy sections. I would just coast across the rougher sections. I was becoming concerned that I might break something. I can now hammer through those same sections at full tilt.

No I never had much body roll. I added the swaybar a couple of years ago trying to control the oversteer. It did not help but the bar stayed on the car anyway. Knowing that it would help keep the roll at bay only encouraged me to try the softer spring rates. They were just sitting there on the shelf as I had already gone to the 250's on the rear so I figured why not try it.

The other thing is how overly stiff our cars are sprung. Check out page 20 here: http://magazinevolume.com/12765BF/#/1/ My car should have 125# springs on the rear according to the chart. So the 350's were nearly 3 times more stiff than they suggest. My super soft 250's are only 2 times stiffer than they suggest. The 350's up front are really close to their suggestion once you consider the motion ratio and mounting angle.

I have driven a friends roadster with the stock FFR/Konis setup and thought it rode much better than mine did with the same setup. I also raced it once and it did very well on the track....I was very impressed. Because of this I would suggest you finish your car as delivered and make the changes to fix problems once you find them. Making changes to fix problems you have yet to identify might make things worse. I hope my experience will help others to fix what they don't like and give a guide as to what is possible. I do not want to be the cause of someone creating problems that did not exist in the 1st place.

Listen to the throttle oscillations across the bumps at the finish. They are caused by my feet bouncing on and off the gas pedal. My head also hit the ceiling hard and the rear of the car was airborne: https://www.youtube.com/watch?v=vZGnl3Jhd10

Now watch the finish on the roadster as it glides across the same bumps on the rev limiter: https://www.youtube.com/watch?v=GpJW0E5j6GM

I was driving both cars in the videos and the difference was huge!

[skullandbones]

You didn't mention how the roadster was sprung, I don't think. Was it stock from FFR? I think they come with Koni's with #450 or #500/F and #350/R. Mine are still #450/F and #350/R. I am curious to try reducing the coils especially in front as the ride is very stiff and I don't use nearly all the available travel. When you press hard on the front fender it barely moves.

Re oversteer: moving the engine forward 3 inches should reduce that tendency, right? I have no oversteer that I can feel unless I haven't pushed the car around the curves hard enough yet. I haven't been on a track or AX so I may have to simulate that by finding a rural area and take the curve faster than normal just to see the tendency. I've been on the road for about 1500 miles but much of that was sniffing out other issues or just driving. BTW: I have -1 camber, +6 castor, and as best I can figure, 0 toe. I have not taken it to an alignment shop to verify that yet (probably will just to be sure). As Pres. Reagan said, "trust but verify".

Love the videos! Wish there was more of this. It makes you feel like you are in a simulator: next best thing to being there yourself.

Thanks,

WEK.

[Jeff Kleiner]

Bill,
With the factory spring combination (500F/350R) the roadster has a natural tendency to understeer. Understeer is safe, oversteer (controlable oversteer) is fast!

Jeff

[skullandbones]

I get your drift (pun!). I was referring to not feeling a marked oversteer or understeer but mine may actually oversteer a bit. I say that as it initiates the turn with no effort but doesn't feel out of control. The PS may mask the feel a little. I'm not sure without some track time or many curves to test it if it is possible to really tell. Obviously, STLMARSHAL advocates the softer springs (front), how about you in your AX experience?

Thanks,

WEK.

[Jeff Kleiner]

Obviously, STLMARSHAL advocates the softer springs (front), how about you in your AX experience?



I'm the opposite and run a very stiff Challenge Car type setup with 750# in front and 500# in the rear. When I speak of over/understeer I'm referring more to steady state rather than initial turn in. This photo that someone took a couple of years ago is a good indicator of what the car does in a steady state. At the time I had just changed to stiffer rear springs in an effort to free up the back and this showed me that it had indeed loosened up and was oversteering slightly just as I was feeling:

http://i269.photobucket.com/albums/jj43/jkleiner/CSCC-10-16-110171-L.jpg

This is a long right hand sweeper that goes a little more than 90 degrees. You'll see that the car is hard on the left rear by how it is deflected under but the left front is slightly turned in countersteer and the right front is unloaded indicating that I'm on the throttle.

Fun stuff :)

Jeff

[STLMARSHALL]

Wek

Yes the roadster had stock 500/350 springs. I can't speak to it's balance as it had An odd tire setup. The ride was far better than my coupe with the same spring setup.

Yes the main reason for the engine move was to reduce the over steer issues via a cg shift. Changing from a 315/315 tire to 275/315 tire was more effective than any other mods. Next was the cg shift.

Glad you enjoyed the videos. I use them to identify flaws in my driving.

[skullandbones]

I don't see how a soft setup in front and a super hard setup can both work. It appears that both of you are successful at what your doing so it is a little counter intuitive. Unless there is a marked difference in the type of courses that you race on, you would expect it to go one way or the other. I didn't know the coupe and roadster were that much different as far as handling. The coupe is 5 inches longer on the wheel base, right? It looks like it would be a better platform but from what you've said, it's easier to set up a roadster (STLMARSHAL).

Yeah it is fun stuff! I don't know why I'm so interested in this aspect of the cars; oh yeah, I do. I don't want to end up with my wheels pointing up!

Thanks, WEK.

[STLMARSHALL]

WEK

There is more than one way to do things. We have stock Miatas, the red Boss Mustang, my Daytona, Exige V6 cup, and tube frame E-Mod cars all running the same course withing a few seconds of each other. They are all setup completely different yet perform very similar to each other.

IMO the Daytona is better at higher speeds due to aero and wheelbase. I think the shorter wheelbase roadster is naturally a better platform for autocross. Any car has to be setup for achieve some balance. In the end the ratio of my 350F/250R rates are the same as the stock 500F/350R and not much different than Jeff's 750F/500R setup. I don't believe that my new found balance has much to do with my spring rate changes. I think the changes in tire sizes and cg shift are what changed the balance. The overall softer spring rates have improved the way the car handles the rougher courses.

Mike