RE: racin' mods

[Ed Walters <EdW@xxxxxxxxx>]

How do we make an E28 or E24 go fast?

Don't worry about power adders.  If you absolutely need more, get a JC
chip and put a K&N filter in your stock air box.  I found that driving
with a disabled O2 sensor made part throttle drivability worse.  You can
make an E28 (and E24) much faster around the track, parking lot, and off
ramp by improving handling.

1. Wheels and tires.  Go with 15" wheels and the applicable tires if you
are keeping stock springs.  Lots of body roll and short, stiff sidewalls
yield obscene tire wear patterns and slow lap times.  16" wheels and
225-50 or 245-45 tires go well with most off-the-shelf aftermarket
springs.  Do not use 17" wheels unless you have extremely high spring
rates or have removed 700 lbs from the car.  More on that later.

2. Camber and Caster.  More body roll needs more negative camber.  BMW
sells offset strut bearings which give you about 5/8 of a degree
additional negative camber.  Some tuners sell offset plates which bolt
to the strut bearing which give you about 3/4 of a degree additional.  I
would not combine the two because of the small diameter of the E28 strut
tower.  You might get spring to sheetmetal contact.  More negative
camber requires smaller diameter springs. (More on that later.)  I am
using camber/caster plates for an E30 with the corners shaved a bit to
fit in the strut tower.  However, adjustment is limited due to the small
hole in the strut tower and mods to this hole are not allowed in SCCA
street prepared.  I am now designing my own over-the-tower camber/caster
plates to allow more adjustment.

3. Shocks and struts.  These depend on what springs you run.  Bilstein
HD's go well with stock springs.  Bilstein Sports or Koni Sports are
well matched with aftermarket springs.  Right now, I am using Koni Sport
(Yellows) shocks and struts but have a set of custom valved Koni strut
inserts ready for my new camber/caster plates.

4. Swaybars.  Go with the stiffest you can find.  Most bars are 25mm
front and 19mm rear.

5. Springs.  Run the stiffest springs you can stand.  Stock springs for
the i, is, and M are approximately 150, 170, and 190 in/lbs
respectively.  Most aftermarket springs are between 200 and 240 in/lbs.
I ran into a clubracer using rates a little over 300 in/lbs.  I use a
rate much stiffer than that and drive it to work every day.  To run a
stiffer spring, you either have to call Eibach and ask them to wind you
a custom spring to fit your stock spring perches, or run 2-1/2" i.d.
racing springs on threaded spring perches.  This also requires
camber/caster plates designed for 2-1/2" springs.  This requires careful
selection of spring height to avoid lowering the car excessively.  Coil
bind is another factor to consider.

6. Strut brace, HD bushings, etc.  Yes, get them

7. Brakes.  Yes, better brakes make you faster at the track.  Good pads
and fluid are a minimun.  Do NOT run cross drilled rotors.  A better
brake setup is E32 front rotors and calipers with E34 (I think) vented
rears.  I am working on a front system with aluminum two piston calipers
and 12.5" dia. x 1.25" thk. directionally vented rotors.  Thats about
320mm x 32mm thk for us metric minded people.

A car with these mods will not dissappoint you (or others) at the next
driving school.

Ed
- ------------------------------------------------------
Ed Walters
1988 BMW 535is 1998 Pizzafest Sport BMW 1st Place
		   1997 NNJR SCCA ESP SOLO II 1st Place
		   1997 NJBMWCCA Points Series 2nd Place
		   BL/SSed, ERKed, coilovered, camber/castered
		   Soon to be EW/MAFed
		   Chip? We don't need no stinking chip
1974 BMW 2002

www.shortshifter.com, UUC Motorwerks, "Holy Shift!"

Pomoto Pictures, "The Deer and the Cheetah",
	an unromantic comedy, coming this fall
	to a theater near you

------------------------------