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Corner scales, missed shifts, and more

Somebody wrote, in response to a question on corner scales, that raising
one corner would increase the weight at that corner and at the opposite
corner. Not true. Raise the right front, and you lighten it and increase
the weight of the left rear. 

Note a car has to be dead level before checking corner weights.

Normally you need height-adjustable suspension to do this, but you can
fudge with a stock car. Those rubber spring spacers can raise one
corner. Shifting some weight (like the battery) around to a different
location can change weights. Spare tire in or out? there's stuff you can
do, just think creatively. The Big Guys will move the engine mounting
points to get better weight distribution: that's a tad excessive for us
weekend warriors.

Missed shifts: God, I hate to weigh in on this one, but it's been
bugging me for two years. I had an early production M3 (5/94) which
supposedly had the "bad" detent and PeeKay (production date 9/95) with
the "good" detent, and I can't tell a damn bit of difference between the
two. Frankly it's inconceivable to me that you could accidentally stick
it in 1st gear at 80 mph without knowing it. First of all, you have to
pull the shifter against a stiff spring (gate detent). How can you not
feel that? Secondly, you have to accelerate the tranny shaft an ungodly
amount over a very short time; you'd feel some resistance. 

JimC says that under hard accel/cornering the transmission can somehow
shift itself from 4th to 2nd. Perhaps, but that isn't what people are
saying happened. 

Somebody said the M3 transmission was unlike any other BMW transmission
or any American car transmission. Untrue in the first part. It's exactly
like other BMW transmissions, just shorter throw, shorter gates. Same
exact feel otherwise. Someone else commented on the Miata, and they were
right on: it has a much tighter tranny than the M3 (best I've ever
felt). If you're used to aVette, then an M3 will be a huge change-up for
you, but a Miata would be more so. 

As someone else pointed out, Porsches blow shifts as well. Couple of
track days ago a nice slantnose got an appointment for a head job after
the owner let a friend try a lap or two. 5th-2nd and bounced all the
valves. 

The only explanation I can imagine is that people are trying to shift
too fast, or too hard. fast shifting buys nothing. Zero. Nobody on this
list ever races their BMW for possible gains approaching the cost of a
blown engine. What's afraction of a second gained by a speed-shift
worth? Zip. The only guys I canthink of are the IMSA guys, and they're
running non-stock gearboxes. Besides, if you're trying to go fast,
banging gears is not the way. You should shift slowly and deliberately,
all the time. Move that shifter into neutral, pause, then slip it into
the higher or lower gear. When the tranny is in neutral, the shift
detents will force it to stay in the 3rd-4th gate. All you have to do is
move it straight up or straight down. Impossible to miss-shift. If in
doubt, learn the old trick of double clutching. That will force you to
shift slowly. Moving slowly inside the car is the secret of going fast
outside. This applies to all the controls, not just the shifter.

And (as it's been said a zillion times), hold the shifter like an egg. I
like to pull back (say from 1st to 2nd) with my 1st-3d fingers, held
vertically and slightly bent. Very little pressure. If the shifter won't
easily slip into gear, I didn't match the engine speed properly: go
around again. To push up, I hold my hand horizontally and push on the
back of the shift knob with my thumb and first two fingers. Again, light
pressure is all it should take. 

Shifting this way not only helps you be smooth and prevents mis-shifts,
it saves clutches. When you've exactly matched the engine and road
speed, there's virtually no wear on the friction disk, so it can last a
long time. Not to mention synchros. My old 1602 had a shot 2nd gear
synchro when I bought it with 55K miles on the clock. I replaced it,
drove like the above for another 200k miles on the new synchro, and it
was still perfect when I sold it 15 years later...

Having driven a Neon recently, I know first hand what a shitty tranny
feels like. I kept getting 3rd and 5th mixed up in that car ( did it 3
times). Even when I was shifting gently. The gates are close together
(not a problem in the M3) and the shifter is rubbery (ditto). 

I don't want to start a flame war, and I'm deeply sympathetic to anyone
who's paid for a rebuild on these engines. I understand there may be
other factors, and certainly if someone maintains that their
transmission slipped silently and easily into 1st at 60 or 80 mph, well,
I won't argue that that wasn't their experience. I've had two of these
cars (E36 M3s), one new and one old, I've rebuilt BMW manual
transmissions, and I just can't imagine how it's possible.

Cheers,

John Browne
M3 LTW (PeeKay)