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Recent content by Joest

  1. Joest

    Is a lighter car always better for cornering?

    If this is a FSAE car you really want to take a good look at tire compounds/carcase construction and also get some pressure sensitive paper and experiment with various tires to see which give the largest foot print for the loads you will be seeing. Much is to be gained in these areas (wink...
  2. Joest

    Is a lighter car always better for cornering?

    From my experience, as long as you re-tune the vehicle and change to tires that are able to get up to operating temperature with the given loads place on the them, the vehicle will keep getting faster or as you put it "handle better." It is possible to get out of the operating range of the...
  3. Joest

    Info Needed on TA Height

    Yes, the only way to change the antisquat is by either changing the angle of the LCA or by changing the CG height (unlikely). Like I said, put some wheelie bars on the car and go do some testing. Play with the angle of the LCAs, tire pressures, and with shock bump settings. That should get you...
  4. Joest

    Info Needed on TA Height

    See Jason's earlier post, but I believe you want to replace the vertical line in the layout with one that goes through you front TA intermediate link (its two pivot point). I'm not exactly sure what your front mount looks like, but if you could post a link to a picture of it, I could give you...
  5. Joest

    Info Needed on TA Height

    Jason, Yes, I agree. I wanted to start with the basics first.
  6. Joest

    Info Needed on TA Height

    I have layed out the TA geometry for your reference. Assume the numbers to be arbitary. Pay particular attention to the vertical line at the TA front mount, the IC location, and the line from the rear tire contact patch through the IC that extends up to the front axle (this is how the antisquat...
  7. Joest

    Info Needed on TA Height

    I don't understand you argument about the lines not intersecting. Lines (in mathematics) are infinitely long and will always intersect unless they are parallel. The point of intersection is your rear suspension IC in the sideview. I don’t understand your question about front or rear IC. We...
  8. Joest

    Info Needed on TA Height

    Ok, that might changes things a bit, but fundamentally, the way you are laying out your IC is not correct. Your vertical line and the line going through your trailing arms will always intersect. This is what determines the height of the IC. The intersection point determines both the...
  9. Joest

    Info Needed on TA Height

    What you want to look at is the angle of a line drawn from the rear axle centerline through the TA front mount (your virtual TA angle). This is what is critical, not the actual TA structure angle. Another point that needs clarification is that the front TA attachment is not the IC. The IC is...
  10. Joest

    Info Needed on TA Height

    Larry, From my experience, I'd have to agree with Greg and Norm. Changing the TA front mounting height does nothing in terms of instant center or antisquat. Obviously you are concerned with damaging your car again, but this could simply be a case of a very sticky track that particular day...
  11. Joest

    Scrub forces at the contact patch

    You got it. That's why there is significant concurrent engineering of new racecars and the tire they will use. Facilities like Calspan, that provide tire testing, typically charge about $30-40K to do a study and the customer must provide 30+ sets of tires. Amateurs just don't have that kind...
  12. Joest

    Scrub forces at the contact patch

    A general rule of thumb is that half the compliance of on any corner of a racecar comes from tire deflection. Therefore, if you are in steady state cornering and you calculate that the outside front suspension is compressed 25 mm, then the chassis is actually 50mm closer to the ground. I'd say...
  13. Joest

    Scrub forces at the contact patch

    Dynamic tire deflection can have a significant effect on steering feel. One notable example is during heavy braking combined with turning into a corner. Pneumatic trail will increase as the tire carcass deflects allowing the tire contact patch to move forward relative to the tire rotation...
  14. Joest

    Objectively measuring and defining subjective steering "feel"

    When the average driver report that a car has "good steering feel" I don't think they are only talking about steering feedback and precision, but also how well a car turns in (goes where you point it). Several factor are responsible for this, namely stiff springs, but a high roll center can...
  15. Joest

    Modern Spindle Geometry Design Practices

    The C4 corvette did have the spindle offset from the steering axis although it was in the opposite direction of the 2005 mustang. I have one of each spindle here before me right now and the mustang steering axis is about 20-25mm behind the spindle axis (reducing mechanical trail) however, the...
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