Boxster in NASA-TTC

[iflyadesk]

Hi, my name is Sam and I asked these same questions over on Rennlist. I enjoyed reading your "Autocross Monster" thread and others on setup, but I wanted to ask some more application-specific questions as well as some clarification questions.

Background
-New to racing 2002 Boxster S, but not new to racing. Have qualified pole in a $7k Spec Miata against national cars (which have $7k engines), so I can at least put down one fast lap.

-Want to build up Boxster S to win in NASA Time Trial class C

-Currently bone stock with street tires

Setup
-Current gripes:
(a) steady state understeer
(b) roll stiffness
(c) ultimate grip
(d) latent turn-in

-What I think will work
(a) bigger front tires & more negative camber (from lowering)
(b) stiffer springs or sway bars
(c) sticky tires
(d) sticky tires

-What I'm hoping you can help me with
--will my ideas work?
--what spring rates are popular?
--can I get away with not upgrading the shocks?
--have you driven the Pilot Sport Cup? --does it really work as a street/track tire?
--would you go with stiffer bars and softer springs, stiffer springs and leave the bars alone, or stiffer both to fix roll stiffness?
--what are the tricks for stuffing more tire in the front? --how big can you go?

-My goal is to modify as little as possible, not for $$ reasons, but simply because less is often better when it comes to tinkering.

-And of course, what am I completely neglecting to think of? (strut bar, blinker fluid, electric supercharger, etc.)

Thanks in advance for your advice, and I look forward to being an active member of the Boxster community.

[joyfrog]

I do not know the largest possible application however I know I have 245/35/19 front and 295/30/19 rears with I believe a 10mm spacer for offset. I am not sure how this would work for the track but I know they fit nicely on factory suspension 2002 Boxter S

[easyc]

Most of your questions will be answered by searching over at the Boxster Racing board....


But I will give you my 2 cents worth...

I want to eventually make my 01 S into either a stock class Cup racer or NASA car, but its already a pretty formidable DE'er.
Tires... hoosier are what the best are running... you want to be competitive in NASA you have to have them. If not... the MPSC or Toyo RA1 or the new R888.
In the front you will want to run 245 width... depending on wheel height your sidewall number will change obviously. With a 17" stock rim (which is light, strong, and cheap to get used) you would run 245/40-17 in the front... some will run the same size in the rear... now you will need a 17x8.5 boxster rear rim to fit that size tire so you aren't pinching it on a 7". Also others run up to a 275 or so in the rear. The front 245 will need a spacer (5-7mm).
Suspension... GT3 front adjustable sway bar, and either a Tarret or HR rear bar with stronger droplinks... you will have your understeer dialed out with those. Most Boxster racers choose to go with the Bilstein PSS9's... I have them and love them and they work great with the aforementioned sway bars... They are relatively cheap for coilovers too. Last problem you will run into is alignment settings... I will spare you another paragraph about that stuff needless to say if you want full potential you will need control arms in the rear from tarrett and at least camber plates OR GT3 arms in the front. Rear you can get fine camber, but Toe is a problem... in the front stock only gets you around -1.5. Now if you didn't want to get coilovers a ROW 030 setup will be pretty good as well... its the euro factory suspension option, but its almost as coilovers.

As I said the boxster racing board is a wealth of knowledge on the subject... you will find some properly setup 2.7 spec boxsters outrunning GT3s.

[racer_d]

I guess the real first step is confirming what improvements are allowed for NASA TTC class (or any other groups you would use the car with) before doing anything.

Sticky tires will help immensly, as will reducing tire stagger front/rear. Not sure MPSCs are the best out there but certainly a safe place to start. I would the worthy tires in the following manner, best to worst: Hoosiers, then Khumo V710s, then Victoracers, then RA1/R888 then MPSCs.

the GT3 front sway bar is a popular upgrade for reducing understeer.

5-7mm spacers up front is also helpful to dial out understeer

Alignment is critical. Using factory components, you will never get "enough" negative front camber for use with the tires mentioned above. Most can get between -1.5 and -1.9 degrees, beyond that you need camber plates and/or GT3 Cup lower control arms. Not sure how legal these would be for your class.

IMHO, PSS9s are too much of a compromise (catering to street and track compliance is not easy. They are a good upgrade, but still a compromise). If rules allow, I would search out something more "race" oriented.

[iflyadesk]

If I read you guys correctly, the car needs more tire and camber in the front. So, probably a good first step would be GT3 control arms, 245s, and a strut brace (how much of a factor is the strut brace?). Additionally, I'll get the sways.

To answer one question, the way NASA-TT works is you are assessed points for each mod. So you get to choose your mods, rather than say having springs alone bump you into street prepared, like Solo II. I'm pretty confident I could work in every mod I want and still be within the base class for this car (TTC).

I'm a bit confused on the tires. Are you saying I should run 245s all round, but keep the 7/8.5 wheel staggering? One of the rules for TTC is you are assessed points for the tire width of the widest tire. So, if I had 205/255s, I'd be charged for having 255s. However, if I ran 245s all around, it'd actually be less points than the previous setup.

I was pretty proud of my 1.5 deg neg camber... I guess it needs much more.

Finally is springs. I want more spring, but there are only two available: H&R and Eibach. These are nebulous progressive spring rates, so I have no idea how they compare to a standard racing spring. I noticed the BSR runs 450/500.

I want to avoid the purchase of dedicated coilovers for several reasons. (1) The increased complexity often just causes more headaches than it's worth. Without a true data acquisition system and a shock dyno, trying to tune shocks is a nightmare and best left to the pros. (2) The corner weighting on my car is already close enough to perfect to not warrant fiddling. (3) I have no intention to fiddle with ride height. (4) $2000-$4500 is a lot of races. I think seat time in the new car will be more valuable to me than Motons.

So, the only options I see for getting a lot of spring without buying coilovers is: (1) Some sort of custom fabbed sleeve similar to a ground control sleeve over the stock shock combined with re-valving the stock shock (they are after all Bilsteins) (2) having a custom spring fabricated. (2) is probably not possible, and would probably be more expensive than it's worth.

Has anyone on here ever tried fabbing their own coilover sleeve?

[racer_d]

Originally Posted by iflyadesk

I'm a bit confused on the tires. Are you saying I should run 245s all round, but keep the 7/8.5 wheel staggering? One of the rules for TTC is you are assessed points for the tire width of the widest tire. So, if I had 205/255s, I'd be charged for having 255s. However, if I ran 245s all around, it'd actually be less points than the previous setup.

I was pretty proud of my 1.5 deg neg camber... I guess it needs much more.

1) I am not sure you can fit a 245 on a 7" rim..

2) Running 245's all around will reduce understeer and make the rear a bit more tossable. I know several folks who ran Carerra Lightweight 18" wheels, I believe 8" (possible 8.5", sorry) wide all around, with 245 hoosiers with great effect.

3) Hoosiers and R comps will wear on the outer edges with less than -2.0 degrees. I think Tirerack has a "care and feeding" section for all the top tires. Seeing neg camber of -2.5-5.0 is really where these tires need to be to maximize potential.