[DeTomaso] Resetting Ride Height With Stiffer Coils

Thu Aug 26 00:02:19 EDT 2010

Actually I think one could calculate how to set the new coilovers

If your car is stock and your springs are still at original strength then the distance from mounting bolt center to MBC is 13.683" loaded.  

You will have to measure the MBC to MBC distance on your stock coilovers before disassembling them.

Then you will know how much the unit compresses under load

The new unit will compress 350/450 as much.  This is an assumption on my part, but no matter what the wheel rate is, the proportion should stay the same, since the geometry is the same.

So say (uncompressed distance minus 13.683) = Z inches.  ( I think the guy at Aldan said they figure about 1" when fitting shocks), then the new unit will compress Z x 350/450 = Y
You want the new unit to be 13.683" when it is compressed, just like your current one.

So you will want the new coilovers to be ( Z - Y) inches shorter from MBC to MBC unloaded before you install them.  

A possible spoiler here would be the degree to which the stock springs are preloaded in the coilover unit.   If they are already compressed a few mm to keep them from moving about when they are unloaded, that would affect how much more they compress under load.  The springs in your coilovers will have no preload unless you crank down on them.

Also, if your stock springs have weaked to some number other than 350 then that will affect the outcome too.

But I would think you will at least be in the ballpark with this calculation.

The 0.5 to 0.337 ratio would apply if you wanted to lower the car by 0.5"-- you would shorten the unit by 0.337" before installing it.

Make sense?  Remember-- I'm not an engineer and college physics was a long time ago. :-)

Jim

-----Original Message-----
From: Pantdino <pantdino at aol.com>
To: detomaso at realbig.com
Sent: Tue, Aug 24, 2010 10:33 pm
Subject: Re: [DeTomaso] Resetting Ride Height With Stiffer Coils

 see on Ted's site that a half inch bump compresses the front shock / spring 
rom 13.683 to 13.346"-- or 0.337" change.
o that is your ratio of wheel displacement to shock shortening-- 0.5 to 0.337 
So if you want the wheel to be a half inch closer to the fender, you will want 
he coilover unit to be 0.337" shorter from mounting bolt center to mounting 
olt center at rest loaded position.
ith that information you may be able to calculate how much shorter the coil 
ver should be at fully extended / decompressed mode, given the 350/450 rate 
atio.
Or I may be completely wrong.  If so, Mike will let us know.  :-)
Jim

-----Original Message-----
rom: Ken Green <kenn_green at yahoo.com>
o: detomaso at realbig.com; Pantdino <pantdino at aol.com>
ent: Tue, Aug 24, 2010 6:56 am
ubject: Re: [DeTomaso] Resetting Ride Height With Stiffer Coils

ed Mitchell's web site has this suspension data:
ttp://web1.wavelinx.net/tmitch/tech.htm
ou probably can figure it out there.
en
-- On Mon, 8/23/10, Pantdino <pantdino at aol.com> wrote:
rom: Pantdino <pantdino at aol.com>
bject: Re: [DeTomaso] Resetting Ride Height With Stiffer Coils
: detomaso at realbig.com
te: Monday, August 23, 2010, 10:40 PM
It will be interesting to see if that is the case.
ran sent me some information regarding suspension systems once that was over 
 head, but I do remember that the force felt by the spring is not the same as 
e weight on the wheel.  Therefore the change in spring compression may not be 
4"
im
----Original Message-----
om: David & Marilyn Bell <davidabell at worldnet.att.net>
: Mike Thomas <mbefthomas at comcast.net>; 'Tony DiGiovanna' <tonydigi at optonline.net>; 
etomaso at realbig.com
nt: Mon, Aug 23, 2010 10:23 pm
bject: Re: [DeTomaso] Resetting Ride Height With Stiffer Coils
ike,
 your car weighs roughly 3200 lb and the weight distribution is roughly
60 front to rear, then the weight on the front is 1280 lb so each front
ing must support 640 lb.  A 350 lb/inch spring will deflect 1.8" under
n load while a 450 lb/inch spring will deflect only 1.4".  So you need to
p your front spring perches by approximately 0.4" to maintain the same
e height.
ve Bell
---Original Message-----
m: detomaso-bounces at realbig.com
ilto:detomaso-bounces at realbig.com]On Behalf Of Mike Thomas
t: Monday, August 23, 2010 7:44 PM
 'Tony DiGiovanna'; detomaso at realbig.com
ject: Re: [DeTomaso] Resetting Ride Height With Stiffer Coils
anks.  Should have added that both new and old springs are 10" Aldan
ls, so the free height is the same on both rates.
ke
---Original Message-----
m: Tony DiGiovanna [mailto:tonydigi at optonline.net]
t: Monday, August 23, 2010 5:23 PM
 'Mike Thomas'; detomaso at realbig.com
ject: RE: [DeTomaso] Resetting Ride Height With Stiffer Coils
n't assume the new springs will have the same free height.
nk you are best served to measure the ride height of the car relative to
 ground with the old springs, then change springs and adjust back to
se settings.
---Original Message-----
m: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
alf Of Mike Thomas
t: Monday, August 23, 2010 8:11 PM
 detomaso at realbig.com
ject: [DeTomaso] Resetting Ride Height With Stiffer Coils
, time for the math wizards to have a head shed . . .
m swapping out my front springs from 350 lbs to 450 lbs, and want to
ieve the same ride height.  Since I won't (I assume) get as much spring
pression with the 450's, I'll need to revise the spring perches on my
an shocks.  I'm guessing I'll need to compress them slightly more on the
ck (the collar height up the shock body) since the springs won't drop as
h when I let the car back down and the springs settle in.  My car is
ck up front with the addition of an aluminum radiator, so probably close
stock weight on the front wheels.
y thought on how much more to compress, or notes form someone whose been
re, would be helpful.  Pulling and readjusting or trying to adjust the
nt on the car are both a much bigger PITA than the rears.  I'd like to
e to do it as few times as possible.
anks in advance for your sage advice.
ke Thomas
low '74 L #6328
_____________________________________________
tomaso Forum Managed by POCA
chive Search Engine Now Available at http://www.realbig.com/detomaso/
Tomaso mailing list
omaso at list.realbig.com
p://list.realbig.com/mailman/listinfo/detomaso
_____________________________________________
tomaso Forum Managed by POCA
chive Search Engine Now Available at http://www.realbig.com/detomaso/
Tomaso mailing list
omaso at list.realbig.com
p://list.realbig.com/mailman/listinfo/detomaso
_____________________________________________
tomaso Forum Managed by POCA
chive Search Engine Now Available at http://www.realbig.com/detomaso/
Tomaso mailing list
omaso at list.realbig.com
p://list.realbig.com/mailman/listinfo/detomaso
______________________________________________
etomaso Forum Managed by POCA
rchive Search Engine Now Available at http://www.realbig.com/detomaso/
eTomaso mailing list
Tomaso at list.realbig.com
tp://list.realbig.com/mailman/listinfo/detomaso
_____________________________________________
etomaso Forum Managed by POCA
rchive Search Engine Now Available at http://www.realbig.com/detomaso/
eTomaso mailing list
Tomaso at list.realbig.com
tp://list.realbig.com/mailman/listinfo/detomaso
_______________________________________________
Detomaso Forum Managed by POCA
Archive Search Engine Now Available at http://www.realbig.com/detomaso/
DeTomaso mailing list
eTomaso at list.realbig.com
ttp://list.realbig.com/mailman/listinfo/detomaso