[DeTomaso] Rear A-arms

Göran Malmberg hemipanter at hemipanter.se
Thu May 31 16:55:18 EDT 2007


Ken, my message wasnt really for anybody to follow, only to tell what I did. Maybe its fun 
to read and look at those images. Yes, int the past I mentioned that the original control 
arm geometry was not designed for modern wheels and tires. Now, people use different
height rollcentres from using different ride height. This upset A-arm angles, or should I say
ALTER the A-arm angles. A good stariting point is parallell to ground lower arms. But in 
such case the tire diameter will dictate ride height. Thats the first problem, the inner lower 
mounting points may need to be relocated to obtain this depending on tires. 4"  to the 
lowest part of the rear and front frame to ground is a good starting point. 
Let us say that we now have a car with 4" grdh and parallell to ground lower arm. Then the 
upper A-arm should be some 3/4" lower to the ground in the chassis than at the uppright.
It is the centre of the balljoints-bearing that counts, NOT the leg of the A-arm. This is with
about 2 hz spring setting. This means a higher located inner upper A-arm mount, have a look
at my site to see what I did to get it higher.

The ORR is another thing. I am not really in to what it is all about but I understand it is a high
speed straight on course. Ok, I understand that there ARE turns, but not slalom. I this case
I believe even more parallell to ground upper arm will do pretty well. As the car is more subjec 
to heave movements than roll, suspension movement camber effect is less of an advantage. 
Therfore, we might use even less than a 3/4" to gound inner upper A-arm points, say 1/2".
But thats strictley ORR stuff. And if some ORR course happen to have much turns, more bars
will be needed or else to much roll cals for more camber compensation. The trick with those 
things is to understand how all parameters works together to get the right combination.
We can for example, not look at corenring setting separate from stright line setting.

Goran
  ----- Original Message ----- 
  From: Ken Green 
  To: Göran Malmberg ; DeTomaso at realbig.com 
  Sent: Thursday, May 31, 2007 9:45 PM
  Subject: [Norton AntiSpam] Re: [DeTomaso] Rear A-arms


  Goran,

        I think most of us have stock fenders and 16 to 18 inches wheels with about as much tire as will fit inside the fenders.  You mentioned in the past that the original control arm geometry was not designed for modern wheels and tires.  Is there a short answer to how we might modify the mounting points and/or control arms to better match modern tires.

        Not really looking for an optimal race car answer, looking for something good for a street/track/ORR car.

  Thanks,

  Ken

  Göran Malmberg <hemipanter at hemipanter.se> wrote:
    Hello!
    I have been driving around with two different upper rear A-arm geometry, to be able to compare
    the two setups directley by turning left and right. Beside beeing very interesting driving a car
    with different A-arm geometry side to side one direct effect is totally wearing out the inside of 
    the tire at the "cambercompensative side" (from acceleration). I decided to make a new right 
    side A-arm using a geometry in between the original and almost parallell arms of the left side.

    I also made the new arm design a little better than that of the last year. In fact a lot better use of 
    the original mounting ears on the chassis. The ball joint chassi mount is horizontally located 
    which is the best angle for a ball joint. It also makes it possible to shim upp and down for perfect 
    Rc. Total weight including all balljionts 2,2 pounds.

    http://www.hemipanter.se/ klick Rollbars springs schocks and A-arms 

    Regards
    Goran
    _______________________________________________

    Detomaso Forum Managed by POCA

    Archive Search Engine Now Available at http://www.realbig.com/detomaso/

    DeTomaso mailing list
    DeTomaso at list.realbig.com
    http://list.realbig.com/mailman/listinfo/detomaso





More information about the DeTomaso mailing list