<e36> M3 Suspension Upgrade Questions

[Jay Sala <jsala@xxxxxxxx>]

I just upgraded my 98 328i with a take-off M3 suspension a couple of weeks
ago.  The components that were sold to me were the following:

Front:	- struts
	- springs
	- spring plates
	- anti-roll bar

Rear:	- shock absorbers
	- springs

Total installation time was 2.5 hours by an experienced installer with the
proper tools (spring compressor, etc.).  The springs worked fine (no size
problems).  But, keep in mind that the springs I bought were from a
(low-mileage) 95 M3.  I understand that spring rates were slightly
different in the 96-98 M3, but I don't know for sure if spring size
changed.  Perhaps not?  

There are other parts that are different between the M3 and the 325/328 and
which were not included in the swap as the M3 owner continued to use them
with his new suspension (H&R springs, Koni struts/shocks, RD anti-roll
bars, in case you're curious).  These are:

Front:	anti-roll bar linkages (attach to strut, rather than control arm),
spring pads, reinforced lower control arm bushings, reinforced steering
knuckles, reinforced lower control arms
Rear: 	reinforced trailing arms

So, upgrading a 325/328 to M3 specs isn't quite as simple as swapping out
the springs/shocks/anti-roll bars.  Most of the components seemed geared
more to durability rather than performance.  The exception are the
anti-roll bar linkages.  I'm told that the modified attachment points make
the anti-roll bars more effective and the car more responsive.  The M3
linkages cost about $35 each, or $70 for the pair from the dealer.
However, you can use the stock 325/328 linkages if you so choose.  

To complete the upgrade, you'll also need to have the car re-aligned to M3
specs.  

The 328i with the M3 suspension handles great, like a BMW on steroids, as
you'd expect.  It turns in more crisply and has much less body roll and
squat/dive on acceleration/braking.  It is not as absorbent of sharp bumps,
and you'll feel road imperfections that you never noticed before, but the
ride is by no means harsh.  In corners, it has significantly more grip and
composure.  You have to be a bit more alert since the car seems to
transition to power-on oversteer a bit more quickly, but that's to be
expected since stiffer springs do bring about faster weight transfer.
Considering how capable the M3 is, the ride is surprisingly livable on a
day to day basis (though I have a high tolerance for ride firmness).  

With regard to tires, I drove the car with the stock 15" tires for two
weeks before I put in 17" wheels/tires.  I strongly advise getting 17s
since the M3 suspension is calibrated for them.  With the 15s, the ride was
firm (due to the stiffer springs/shocks), but not very absorbent, and a bit
floaty when going over humps and undulations on the freeway.   And, the car
would scrape the oil pan on tall humps since the tall, soft sidewalls would
compress so much.  In a way, you had the worst of all worlds.  When I got
the 17s, the ride got only very slightly firmer, but seemed to absorb some
types of bumps better.  The ride lost that last bit of floatiness, and you
got significantly better grip.  I guess the firm sidewalls of the 17s
transmitted the road information the suspension was designed to deal with.
This experience proved to me how important it is to match suspension with
the proper tires.  I can't comment on how the M3 suspension would match up
with 16-inch tires, but I do know that 15s don't work well and that 17s are
great.  

Well, I hope you find this useful.  Good luck.  

Jay Sala
BMW CCA, Golden Gate Chapter
328i  (with M3 suspension/wheels/tires)

>------------------------------
>
>Date: 06 Dec 1998 22:22:58 -0600
>From: Mike Schaublin <mschaublin@domain.elided>
>Subject: <e36> M3 Suspension Upgrade Questions
>
>     Hello fellow digesters,
>     
>     I want to improve the suspension on my '94 325i.  I have seen some 
>     posts referring to upgrading to an M3 suspension.  What components 
>     are involved in the swap?  I have read that the springs are not 
>     interchangeable between a 325 and M3 due to different diameters, I 
>     think.  Could someone please enlighten me about this upgrade?  
>     
>     On a completely unrelated note, what doe the letters "YMMV" at the 
>     end of messages endorsing a product or service stand for?  
>     
>     Thanks,
>     
>     Mike Schaublin
>     '94 325i - gonna get sharked for xmas!! 
>

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