Larry Herman

I'm with Darren here. Especially considering your comparison of two similar cars. Maybe it's just that the Motons work and the Ohlins don't?

I think that your alignment specs are ok, so assuming that the car is actually set to what the specs are, you should be ok there. BTW I have seen settings easily change on the new cars because the mechanics just don't tighten the eccentric bolts enough.

Next I would take a hard look at the shock settings. It could be that you have them set such that they are inducing this strange behavoir. You may just want to soften them up all the way around so that you can better feel what the inherent balance is. Your spring/swaybar balance will be most noticeable at mid-corner, or on the skid pad. Shocks affect the balance in a more transient way, and so exert more of their influence during corner entrance and exit. Incorrect/mismatched rebound settings can negatively affect grip and make the car feel nervous.

BrianKeithSmith

I have been there and done that...

va122

Your springs are fine. You need more tire f/r and your shocks are adjusted wrong.

Seth Thomas

So far everything said about the car is really too general to make a decision on changing spring rates. From the numbers it appears that you are pretty close to what everyone else with a similar setup on similar cars are running. More info on what you are feeling when driving the car would help.

When does the car feel twitchy?
Where in the turn does the car lose grip?
Slow turns or fast turns are more of an issue?

All of these questions will help get a better answer. At this point what is the reason for not trying the wider tires? From what I have seen on 996s they like to get a wider tire in the front than came from the factory. The 245/40 on the front with a 305/30 or 295/30 on the rear seems to be a pretty decent setup on these cars with those spring rates. At this point I would bet your suspension is overloading the grip of your tires

onefastviking

+1

Specifically on Seths questions, corner entry, mid corner, or corner exit ?

I know you are trying to set the car up for Spec 996 so why not run the tire you are suppose to ? The Hoosier 245/35 285/30 combo won't throw off your rake, and will give you the more front tire that you need.

I think your springs and align are all close to where you need them, I think it's more in the tires and shock settings that need adjustment. Also I know this is a fairly new car for you and it does take some getting use to a new car and it won't handle quite like the 951, it is different.

My advice would be to get the right tires on it, set the shocks full soft, and then work up from there. Use sway bars for final adjustments once you get the shocks sorted.
I have been putting together a set up sheet of what I do with a car on initial set up to help out maybe we can work together at an event and help get it sorted.
I'm (and you too) are too busy at the PCA events, but it would be good to do an open track day to do it. There is a friday event in a couple weeks. Or we could do another one at TWS or MSRH.

Mike's car got better this weekend with what we did but there is still a lot more left in it, I am guessing yours is the same.

onefastviking

I do still feel your springs are a little stiff btw, but we have had this conversation before.
Some of what you are feeling could be the stiffer springs not allowing the tires to work and since they are so stiff they are overloading the DOT tires you are running causing some of the feeling you are having.
Going with a softer spring, or a tire that can handle a stiffer spring could help this out. I would recommend a softer spring, say 600/800 or 650/850 even.
Rememeber that you have no aero on this car and running DOT tires you are better with a softer spring.
I am using much less spring than you, much more tire, and going much faster, and we have a little aero.

trackjunky

Seth, the car turns in almost too well. I did run 245 front and 285 rear and it was still pretty nervous in back.

When does the car feel twitchy? I can't trail the brakes into a corner at all. The rear will step out. With normal straight line braking, after turn in, the car wants to oversteer. Turn in is razor sharp, which tells me that I have plenty of grip up front.

Where in the turn does the car lose grip? See above, but the car doesn't really want to take a set. When I went to the bar settings described, the car did get a whole lot better. This was the very first time that I could actually feel the rear take a set and load up the suspension, you know the kind you feel in your hip. It's this point that makes me think about spring rates.

Slow turns or fast turns are more of an issue? Well, since I'm not confident in the car's ability to hold, I have really been ***** footing it around. I was only able to get the tire temps into the optimal zones after really going to extremes with the sway bar. For example, I'm about 4 seconds slower than my 944 Turbo times at TWS.

I think the prime set up is 245 front and most likely 295 rear, which would make the rears about .5" smaller in diameter than the fronts for BFG-R1's or R888's. I'm not going to run Hoosier's so that comparion is out.

Really appreciate all of the help here guys.

trackjunky

Larry and Viking, I went down two more clicks on compression in the rear on the last run and the car improved further. I'm now 17/25 clicks from full hard on compression and I think 24/40 from hard on rebound. (Ohlins recomends going to hard and counting back to soft)

VR, resist the temptation my brother.

Larry Herman

Keep going softer on the rebound until the car feels floaty. Most people make the mistake of running too much rebound because it makes the car feel "tight".

mglobe

Bill,

I'm curious why you don't go 245/275. Both Toyo and Nitto make tire sizes that work for that stagger. That's what I'm running, and the car feels good. I think Viking is right (ok I KNOW Viking is right) about my car still having a fair amount of improvement left in it, but it seems to me to be quite balanced and predictable. You'll get a chance I hope to check it out at ECR and see for yourself.

Veloce Raptor

Yup, you gave me this advice when I first got the current suspension, and it was spot-on.







Professional Racing and Driving Coach

trackjunky

Mike, if you recall at the last DE I did run 245/275's. That's why I bought the 275's and that's when I told you about the effect on the traction control and ABS with the 245/285 set up. I went 225/275 to get the same rolling circumference for the 8 & 10 inch wheels.

If the 245/285 set up was causing oversteer, going to a smaller rear tire didn't help. I think that Larry is on to something here with rebound, as I did not adjust that from the factory Ohlins setting.

Thanks for stepping in though, because most feedback here has been that a 275 at the back is no good and you are running the 245/275 combination. You are running 600#front and 800# rear. Where are your sway bar settings? I know that you tightened up your shocks, where did you wind up?

mglobe

I'm at 11/15 front and 13/15 rear on the shocks now. That's four clicks higher both front and back than where I was before. It made a very big improvement for me. Viking pointed out that we're getting some rear end hop (for lack of a better word) now, particularly at places like T6/T5 going CW. He thinks we can take it out with the sways. I'm one off of full stiff on the rear sway, and I'll have to check but I think I'm in the middle on the front. I'll have the car up on stands next week to put on new rotors, and I'll check it then.

trackjunky

Boy, that makes me think that Larry may have hit it on the head with going full soft on the shocks and seeing what happens. If I remember correctly, that's the advise I first gave you. Funny how I don't listen to my own advise.

I'm going to check canister pressure to see what's in there. Larry, any suggestions?

Veloce Raptor

If it's below 150 front, 175 rear, add N now. Ideally, with your springs, maybe 175 front & 225 rear? Larry may disagree.....







Professional Racing and Driving Coach