[DeTomaso] Sway bars

The Goyaniuks andriykoisg at yahoo.ca
Thu Apr 9 17:57:17 EDT 2020


 Thank-you for the response and some good insight.
Very much appreciated.

There is much to say about setting up the suspension for best handling.

Weight distribution, Centre of Gravity, Moments of Inertia, Spring rates, Unsprung weight, Wheels/Tires (as you mention), Type of tires ... etc.

For some reason, I thought the stock set-up was 3/4 front and 7/8 rear. Thank-you for putting me straight.

I guess I will go with putting the 1" sway bar with spherical ball ends and poly mid bushings. I will keep the front 7/8" and see how it goes. I have a 1" front bar - but I have opted NOT to put that on.

Some other thoughs:
I wonder what the skidpad result would be when:
1) Weight is taken off the front with a Fluidyne Aluminum Rad.
2) Lightweight bumpers front and rear
3) Weight taken off the back end with a lighter (100lbs) aluminum engine set-up.
4) Rather than the stock Arriva's ... GTS set-up with Campis and Pirrelli 10s, 8s. OR. As you say, Wilkis 17x11 and 17X8s with rear 315/45/ZR17 and 245/45/ZR17 
5) Upgraded springs and shocks

Any other thoughts?

Happy Easter

Bohdan G.

P.S. I am working on it at Mark's
     On Thursday, April 9, 2020, 05:09:19 p.m. EDT, Mike Drew <mikeldrew at aol.com> wrote:  
 
 BG,

Your car is stock, 7/8 front and 3/4 rear. The cars were deliberately set up to understeer (push). 

Euro cars had, as an option, 7/8 rear swaybars which made the cars very neutral. 

Back in the 1990s Larry Stock and Jack DeRyke and I conducted skidpad tests with a primitive G-meter using Larry’s black Pantera. We started off with the stock configuration as a baseline, then installed 7/8 rear bar, then 1-inch front bar, then 1-inch rear bar. 

More is always better, right?

Wrong. We saw a HUGE improvement in cornering power going from 3/4 rear to 7/8 rear leaving the stock 7/8 front bar alone. We were surprised to then see a decrease in performance going to a 1-inch front with 7/8 rear, and an even greater decrease going to 1-inch front and rear. 

Jack’s theory at the time was that the stiffer swaybars were imparting loads to the somewhat flexible chassis that it was incapable of withstanding. He had a beautiful turn of phrase: he said he thought the chassis was “acting like an undamped spring”.

The graphs of the cornering G-forces were very smooth and controlled with the smaller bars.  But when 1-inch bars were introduced, there would be sharp spikes and troughs in the graphs, especially with 1-inch front and rear. Instead of delivering a constant .93 gs, let’s say, the graph showed cornering gs rapidly oscillating between .89 and .83 (or something like that).

This was long before anybody ever invented chassis stiffening kits. It stands to reason that once the chassis is stiffened up, cornering performance might be improved by using 1-inch bars. But it’s fairly clear that for a stock body, 7/8 inch front and rear is optimal, with the caveat that you will lose some of the built-in stability imparted by having a smaller stock bar in the rear. 

That means with a bigger rear bar, you can go around a given corner faster, but you need to be a better driver.  With the stock setup, if you go into a corner too hot the car will understeer, or plow/push toward the straight ahead. If you lift off the gas the great likelihood is that the front end will be weighted, the tires will become more effective, and the nose will politely tuck in and the car will safely negotiate the corner. 

With a more neutral setup, you can go whipping around that same corner at a higher speed.  But if you lift off the gas, the rear end will be more inclined to step out, and a spinout could result. 

Note that most aftermarket wheel and tire combos aggravate the understeer/plowing condition, because the width of the tire contact patch is normally increased far more in the rear than the front. This upsets the balance and promotes understeer. So a given car will need a swaybar change to maintain the same cornering balance after switching from old-fashioned stock-sized tires to slightly wider front tires and ridiculously wider rear tires. 

Most people who go the big-wheel route opt for 335-width rear tires, but some have opted for 315 for this very reason.

Mike

Sent from my iPad

> On Apr 9, 2020, at 13:06, The Goyaniuks via DeTomaso <detomaso at server.detomasolist.com> wrote:
> 
> 
>  There is dialogue about sway bar bushings going on right now.
>  I am busy putting my 74 back on the road - Stock body.
>  (upgraded springs, shocks, brakes)
>  Can anyone let me know what the stock sway bar set-up is?
>  I ask this simple question because my FRONT is 7/8 inch and my REAR is
>  3/4 inch. I was surprised by the sway bar thicknesses. I thought that
>  the rears should be the same or thicker than the fronts.
>  Anyway, my second question is:
>  Any performance improvement by leaving my fronts as 7/8 inch and
>  putting 1" on the rear.
>  BG
> _______________________________________________
> 
> 
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-------------- next part --------------
    Thank-you for the response and some good insight.
   Very much appreciated.
   There is much to say about setting up the suspension for best handling.
   Weight distribution, Centre of Gravity, Moments of Inertia, Spring
   rates, Unsprung weight, Wheels/Tires (as you mention), Type of tires
   ... etc.
   For some reason, I thought the stock set-up was 3/4 front and 7/8 rear.
   Thank-you for putting me straight.
   I guess I will go with putting the 1" sway bar with spherical ball ends
   and poly mid bushings. I will keep the front 7/8" and see how it goes.
   I have a 1" front bar - but I have opted NOT to put that on.
   Some other thoughs:
   I wonder what the skidpad result would be when:
   1) Weight is taken off the front with a Fluidyne Aluminum Rad.
   2) Lightweight bumpers front and rear
   3) Weight taken off the back end with a lighter (100lbs) aluminum
   engine set-up.
   4) Rather than the stock Arriva's ... GTS set-up with Campis and
   Pirrelli 10s, 8s. OR. As you say, Wilkis 17x11 and 17X8s with rear
   315/45/ZR17 and 245/45/ZR17
   5) Upgraded springs and shocks
   Any other thoughts?
   Happy Easter
   Bohdan G.
   P.S. I am working on it at Mark's

   On Thursday, April 9, 2020, 05:09:19 p.m. EDT, Mike Drew
   <mikeldrew at aol.com> wrote:
   BG,
   Your car is stock, 7/8 front and 3/4 rear. The cars were deliberately
   set up to understeer (push).
   Euro cars had, as an option, 7/8 rear swaybars which made the cars very
   neutral.
   Back in the 1990s Larry Stock and Jack DeRyke and I conducted skidpad
   tests with a primitive G-meter using Larryas black Pantera. We started
   off with the stock configuration as a baseline, then installed 7/8 rear
   bar, then 1-inch front bar, then 1-inch rear bar.
   More is always better, right?
   Wrong. We saw a HUGE improvement in cornering power going from 3/4 rear
   to 7/8 rear leaving the stock 7/8 front bar alone. We were surprised to
   then see a decrease in performance going to a 1-inch front with 7/8
   rear, and an even greater decrease going to 1-inch front and rear.
   Jackas theory at the time was that the stiffer swaybars were imparting
   loads to the somewhat flexible chassis that it was incapable of
   withstanding. He had a beautiful turn of phrase: he said he thought the
   chassis was aacting like an undamped springa.
   The graphs of the cornering G-forces were very smooth and controlled
   with the smaller bars.  But when 1-inch bars were introduced, there
   would be sharp spikes and troughs in the graphs, especially with 1-inch
   front and rear. Instead of delivering a constant .93 gs, letas say, the
   graph showed cornering gs rapidly oscillating between .89 and .83 (or
   something like that).
   This was long before anybody ever invented chassis stiffening kits. It
   stands to reason that once the chassis is stiffened up, cornering
   performance might be improved by using 1-inch bars. But itas fairly
   clear that for a stock body, 7/8 inch front and rear is optimal, with
   the caveat that you will lose some of the built-in stability imparted
   by having a smaller stock bar in the rear.
   That means with a bigger rear bar, you can go around a given corner
   faster, but you need to be a better driver.  With the stock setup, if
   you go into a corner too hot the car will understeer, or plow/push
   toward the straight ahead. If you lift off the gas the great likelihood
   is that the front end will be weighted, the tires will become more
   effective, and the nose will politely tuck in and the car will safely
   negotiate the corner.
   With a more neutral setup, you can go whipping around that same corner
   at a higher speed.  But if you lift off the gas, the rear end will be
   more inclined to step out, and a spinout could result.
   Note that most aftermarket wheel and tire combos aggravate the
   understeer/plowing condition, because the width of the tire contact
   patch is normally increased far more in the rear than the front. This
   upsets the balance and promotes understeer. So a given car will need a
   swaybar change to maintain the same cornering balance after switching
   from old-fashioned stock-sized tires to slightly wider front tires and
   ridiculously wider rear tires.
   Most people who go the big-wheel route opt for 335-width rear tires,
   but some have opted for 315 for this very reason.
   Mike
   Sent from my iPad
   > On Apr 9, 2020, at 13:06, The Goyaniuks via DeTomaso
   <[1]detomaso at server.detomasolist.com> wrote:
   >
   > i>>?
   >  There is dialogue about sway bar bushings going on right now.
   >  I am busy putting my 74 back on the road - Stock body.
   >  (upgraded springs, shocks, brakes)
   >  Can anyone let me know what the stock sway bar set-up is?
   >  I ask this simple question because my FRONT is 7/8 inch and my REAR
   is
   >  3/4 inch. I was surprised by the sway bar thicknesses. I thought
   that
   >  the rears should be the same or thicker than the fronts.
   >  Anyway, my second question is:
   >  Any performance improvement by leaving my fronts as 7/8 inch and
   >  putting 1" on the rear.
   >  BG
   > _______________________________________________
   >
   >
   > Detomaso Email List is not managed by POCA
   > Posted emails must not exceed 1.5 Megabytes
   > DeTomaso mailing list
   > [2]DeTomaso at server.detomasolist.com
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   >
   > To manage your subscription (change email address, unsubscribe, etc.)
   use the links above.
   >
   > Members who post to this list grant license to the list to forward
   any message posted here to all past, current, or future members of the
   list. They also grant the list owner permission to maintain an archive
   or approve the archiving of list messages.

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