I agree with Ron all his points.
Our 77 280Z with a SBC 350 / T5 is lowered about 1-1/2". I used progressive
wound springs and gas strut carts. as well as PU bushings all around. I had
to modify the the front cross member moving the lower control arm pivot
points up .75 and out .25" to maintain effective steering geometry and to
reduce the inherent bump-steer of the Z chassis. Had to fabricate some
camber adjustment plates for the top of the strut towers front and rear with
slots to allow enough camber adjustment to get it back to where it needed to
be.
Changed the rear springs twice, once using the two that came with the set,
the second with slightly higher rate, custom wound locally to accomodate the
extra weight of the rear-relocated battery and the roll-bar. Suspension
tuning is a fit and test proposition. Luckily with the 350 set back 3.5",
offset to the passenger side .75" and fitted with alum. intake, headers, and
other lighte weight parts, the Z has a weight balance as good as stock,
maybe even a tad rear heavy. The local alignment shop is run by a guy who
races SCCA, so he did a great job doing the final set-up.
With the car as low as it is, and having a BRE "spook", I've had to patch
the glass at least 3 times since the car hit the road - mostly due to uneven
driveway aprons.....
Roadster content - the "R" is coming along - real close to final
engine/tranny fit then will be on to header / exhaust fabrication. Should
have new pics up later this week.
Mark Sedlack
OROC
Cuyahoga Falls OH
66 1600 http://home.neo.rr.com/mark2000/images/datsun1600/
77 280Z http://home.neo.rr.com/mark2000/Myz.jpg
----- Original Message -----
From: "Ronnie Day" <ronday@attbi.com>
To: "Roadster List" <datsun-roadsters@autox.team.net>
Sent: Sunday, February 10, 2002 11:55 AM
Subject: Re: Lowering Front End (long, maybe boring)
>
> In addition to the comments from Tom and Todd I'll add the following.
Since
> the car wasn't designed with 50 series tires, using them or any wheel/tire
> combo that's much smaller in diameter than OEM may not "look" right, but
> that doest mean the suspension needs to be altered to achieve what's
> essentially a cosmetic fix.. Still, if you want to do this don't lower the
> car by heating the springs, cut them. If you heat the springs, there's no
> way you can control the results nor are you likely to end up with the same
> rates on both springs. It just ain't gonna happen in the real world. You
can
> cut them using a cut off wheel in either an air or electric die grinder,
or
> with a Dremel tool which will probably take longer, but it can be done.
Same
> idea if you're tempted to cut them with a torch, don't. Cut them, or have
> them cut.
>
> For street use I think you'll regret trying to drop the front two inches,
at
> least all at once. Aside from the big increase in spring rate caused by
> shortening the spring enough to lower the car two inches, you're loosing
> that two inches of suspension travel, too (already pointed out), and
you're
> almost certainly going to mess up your suspension geometry, since the
> geometry is designed around the stock ride height.
>
> What do I mean? Well, for a number of reasons the wheel doesn't move
> straight up and down with the wheel/tire combo always perpendicular to the
> road. The angle changes constantly as the suspension moves up and down.
When
> you alter the static (at rest) ride height of the car by lowering it, at
> least without also relocating the suspension attachment points, you may
not
> have enough alignment adjustment available to compensate. Traditionally
> you'll end up with way too much negative camber, with the top of the tire
> tilted in toward the car's centerline.
>
> I know it'll be a hassle to do, but I'd suggest cutting off no more than a
> half a coil at a time and then reassembling the suspension to evaluate the
> changes. You can always cut more off, but it a real PITA trying to super
> glue springs back together. ;>) If you're going to test drive the car
after
> a change, then you really need to get it aligned, every time, first. Or,
you
> could just roll it back and forth a few times to get the suspension to
> settle in before deciding to take more off, or not.
>
> Finally don't get sucked in to slamming the car just because it looks
> "cool". I see so many otherwise very nice late model import sedans and
> coupes that almost drag on the pavement and that have incredibly obvious
> misalignment problems. They've got to be uncomfortable and at the least a
> handful to drive, if not actually dangerous.
>
> One of the biggest mistakes folks make on 510's is excessive lowering in
the
> rear which, unless you go to the not small expense of relocating the
> suspension pickup points, causes a toe out condition in back. This creates
a
> very loose handling condition which has caught many by surprise big time,
> often with very unfortunate results. If you look at the BRE 2.5 Trans-Am
> cars so prominently covered in a number of magazines the past couple of
> months, you'll notice that they actually sit a bit higher in back than in
> front. There's good reason for this. The ride height was adjusted for the
> best handling, not just for looks.
>
> Lowering vehicles the right way is the reason that a number of companies
> offer dropped spindle setups for newer vehicles, particularly trucks.
Moving
> the wheel spindle up lowers the vehicle while leaving the suspension in
it's
> as designed position. Then the main thing you need to worry about is speed
> bumps and such tearing up your (usually) custom bodywork and paint.
>
> Bottom line, take your time and approach your goal slowly. If you don't
have
> them already, I'd recommend buying a decent air compressor (two
> cylinder/belt drive/20 gallon tank or larger) along with a fair set of air
> tools. You should be able to get both from Costco or Sam's for around $400
> or $500. The tool quality won't be the best, but should be good enough for
> the weekend hobbyist. Take the word of this "old guy" (ask Gordon if you
> want/ need that explained), these tools will make work go much faster,
> probably safer and are well worth to investment.
>
> FWIW,
> Ron
>
> Ronnie Day
> ronday@attbi.com
> Ronnie_day@acd.org
> Arlington, Texas
> ***********************
> '71 510 2-dr (Prepared Class Autocrosser)
> '73 510 2-dr (Street Toy)
>
> /// datsun-roadsters@autox.team.net mailing list
> /// Send admin requests to majordomo@autox.team.net or go to
> /// http://www.team.net/cgi-bin/majorcool
> /// Send list postings to datsun-roadsters@autox.team.net
/// datsun-roadsters@autox.team.net mailing list
|
