Bang for the Buck, er Points

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Bang for the Buck, er Points

Postby bryanearll on Wed Jan 05, 2005 8:39 pm

996 C2 2001 (class NS/S - currently)
Problem - I'm convinced I would be much faster if I could eliminate the problem understeer. There is no adjustment in the stock shocks possible and only the very smallest amount of camber adjustment possible. (or so I'm told and have read)

1) Current tire (in December) was a well used Dunlop Sp Sport - Dot 280; I've been reasonably sold by the members and the price on the Kumho MX - Dot 220. However, the Bridgestone Potenza SO-2a and RE050A both have a Dot 140. How much sticky do you get for the 60 pts between what I've been driving and the Kumho's and the 80 pts and Kumho's? Is the difference between the Dot 220 and Dot 140 a noticeable difference? The 140's cost 1 point, the 220's are free.

2) In the NS/S class you are allowed 0-2 points. Nothing I can do for 2 pts is going to fully correct the understeer problem, or is it? The best I can find googling on the web was: http://www.rennlist.com/996_faq/
Is this information reliable?
A stiffened spring is only 2 points and less intrusive than a GT3 swaybar for 2 points.

I can't adjust the suspension further within NS/S, and frankly I have a hard time seeing a suspension improvement: monoball, camber plates, sway bar, wheels, without moving on into NP. The only other improvement I can see is to get 140 tires and a "shock tower stiffening device" (whatever that is)

So I guess the real question :roll: is: for the 2 points allowed, keep the Kumho's and do "x" or take the Dot 140's of choice and "what"?
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Postby Jad on Thu Jan 06, 2005 9:29 am

Tires are going to help your lap times the most. Don't read too much into the exact DOT number. There is no standard used in getting those numbers, so they are a general guideline at best. A year or so ago, there were basically 3 'catagories' of tires in my opinion, the sub 50 ratings, the 50-100 tires, and the above 100. Each step was worth a solid second in a typical autocross. The numbers within the range were meaningless, as a 140 was often much WORSE than a 240 from another company. Recently, there is a new range developing in the 100-140 range (this is new and I am not convinced yet as I think there are just a couple of good tires out that happen to have those numbers) that gets about 1/2 second from std performance street tires. As Bob pointed as, the DOT rating of the Toyo RA1 changed from 40 to 100 without any change in the tire.

So, if you goal is to eliminate understeer and improve times, I would put a bigger front tire of the stickiest type you can get on while going with the same type of tire in back in the stock size.

A caveat back to my normal preaching, if you are pushing a lot, it usually means you are over-driving the car, not that the car has a problem. You will be faster if you go in slow and out fast. If you try to carry too much speed into the corner, you will push - period. By adding a bigger front tire and keeping the rears std, you will reduce push, but you are giving up traction in the back that could be used to get on the gas sooner and harder (ie slow in, fast out setup)
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Postby bryanearll on Thu Jan 06, 2005 10:07 am

Thanks for your thoughts. I guess the only frame of reference I have on the understeer problem is this:
1) Nobody, not even several instructors, could get my car to pitch and catch on a soapy skid pad.
2) Clearly the best set up 996 I've ridden in has been Chuck Hassel's. He's made several improvements, wider tires, R rated tires, lowered the suspension. He's also a good driver. His car however could carve turns substantially faster than mine. 4 seconds faster at the Dec. AX. Chuck, what class do you figure you will be racing this year, N/S or N/P?
3) Doug Kott's 944 obviously is a different car but the ability to throttle steer effortlessly through the turns against my choices of:
a) enter slow and exit fast as you suggested (this is what produced the fastest times for me in December.) 3-4 seconds slower than Doug.
b) overdrive the car and be forced to lift while going through the turn (which does in fact get the rear end around a bit). Might have seen a cone doing this.

Keeping the car carving the turn and having the option to throttle steer more effectively is what I'm looking to balance.
Thanks for your thoughts!
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Postby Jad on Thu Jan 06, 2005 11:07 am

Are your front and rear tires worn evenly? And what air pressure where you running? Amazingly, changing air pressure by 2-3 pounds can have a big effect on performance. Generally, take 1-2 pounds of air out of the end you want more grip in.
Last edited by Jad on Thu Jan 06, 2005 12:17 pm, edited 1 time in total.
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Postby martinreinhardt on Thu Jan 06, 2005 11:12 am

Jad, is right.

I am not familiar with the 18", but it definitely helped with the 17" to go from 205 to 225's and leaving the rears stock 255.

My recommendations:

1) Get an alignment from a shop with racing experience like: Dieter, Black Forest or Mind Over Motorsports. Tell them you autox the car and have an understeer problem. Get as much negative camber as you can get (won't be much without lowering springs). Maybe the ROW M030 Springs are free, not sure about this because the US M030 are different.

2) Get a good stock class tire like the Kumho MX with the front going to 235 or 245

Note: Don't bring it to the Official Porsche dealers, because they have no clue on how to setup these cars for this kind of driving. I know because I went thru that process.
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Postby bryanearll on Thu Jan 06, 2005 11:21 am

That's cheap and easy! Last time I started with cold tires at 32/36 PSI. I'll try 32/40 next time, though the rears might get a little hot.
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Postby Kim Crosser on Thu Jan 06, 2005 12:07 pm

I had a lot of understeer originally in the Boxster. A fair amount of that was my driving - going in too hot, not starting the rotation right, and consequently "pushing" in the corners.

I now have virtually no understeer and can throw the tail around pretty much at will.

The only adjustments I had made to the suspension was to set up maximum camber and have all the toe-in removed (I think Pioneer called it a "track alignment"). I think the toe-in affected the understeer more than the camber (the camber changes are quite limited without suspension mods).

After the toe-in changes, the car is a bit "twitchier" in normal driving, but it seems easier to start the rotations in the corners (this could also be 99% due to a better driving style).

Virtually every student I have had with understeer problems were due not to the car, but to the driving style. Changing tire pressures reduced the problems in a couple of cases, but mostly the understeer was due to one or more of: too fast in; sharp steering change on entry (breaks the tires loose); too much steering input (scrubbing because the wheel angle is too great for the speed); trying to get on the gas too hard/too early while the car isn't far enough along in the rotation (reduces grip as weight transfers back). Fixing those usually fixed the understeer problems.
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Postby bryanearll on Thu Jan 06, 2005 12:15 pm

Once again thanks for the thoughts Kim.

My instructors have been great in helping me to improve and you can bet I will have one with me again on the 30th. (Thanks to Dan Chambers, Chuck Hassel, and Doug Kott once again for past instruction, helping to get past those little hurdles.)

I will have the alignment checked when the Kumho's go on the car.
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Postby David J Marguglio on Thu Jan 06, 2005 12:24 pm

First, I would like to second Jad's thoughts that it is probably the driving; however, as part of that learning curve, it is important that you understand how changes in your setup affect the car. You are correct that changing pressures is cheap, and like Jad indicated, it can have a profound difference on performance. The best set up for you and your car is a tough boggie to hit, but you can speed up the learning curve by finding other drivers that are using the same tire (and hopefully the same car) and pick their brain on pressures. Personally, I think that a common mistake is to over-inflate and therefore would suggest that you leave the rear alone and take two pounds out of the front. Play with them and you will soon find what works best for you.
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Postby Jad on Thu Jan 06, 2005 12:24 pm

Those tire pressure 32/40 cold, sound like a good starting point. Watch them and I would keep the rears at or below 44 hot and the fronts at or above 32 hot. That should keep you in a safe range for street tires and give you lots of room to adjust.
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Postby rss996 on Sun Jan 09, 2005 9:01 pm

I run my tires at 30/32 cold at the auto x....

Bryan,

I have h&r springs with a great alignment and my car is very easy to pitch and catch. Steve Dente said my 996 was one of the most well balanced 996's he has driver at the driving school.

Go have Jae Lee take care of you he is a master and one of the nicest guys you will ever meet!

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