Modern Spindle Geometry Design Practices
Modern Spindle Geometry Design Practices
(OP)
After closely inspecting the front spindles of a new '05 Ford Mustang (strut suspension) I notice that the hub centerline lies forward of the lower ball joint by about 25mm. I was hoping to spark some dialog about what effect this geometry has in terms of handling and steering feel. Perhaps Ford moved the spindle pin centerline forward as a way to run a lot of caster (10-15 deg) without offsetting the steering axis too far from the tire contact patch center as to not make steering effort excessive. Assuming a castor angle of 14 degrees, I come up with about 26mm of mechanical trail. The benefits of caster (hence mechanical trail) are clear to me, but what I am specifically targeting is whether it makes sense to run lots of caster, yet limit the amount of mechanical trail.
Cheers,
Joest
Cheers,
Joest





RE: Modern Spindle Geometry Design Practices
I think you don't want too much mech trail, because that will mask the change in pneumatic trail as the tire approaches its limit.
For whatever reason the mech trail of modern cars falls in a tight band, so even if detecting the limit is not the reason, some limit still applies.
OK, then I'd wonder about what castor is optimum. It helps a bit with camber gain in tight turns, but frankly, with radials, who cares?
It seems to add damping to the steering. That's a good thing.
However it does confuse things, vertical forces at the tire patch will become tie rod forces. This is bad. The driver doesn't need this information.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Modern Spindle Geometry Design Practices
Norm
RE: Modern Spindle Geometry Design Practices
RE: Modern Spindle Geometry Design Practices
As for the original topic: It appears that everything they did was to help out the steering feel. More caster gives you better camber gain and thus produces better cornering feedback for a sporty car. Another good example of this is found in the Nissan 350Z/G35 vehicles (almost 9 degrees of caster I think).
RE: Modern Spindle Geometry Design Practices
RE: Modern Spindle Geometry Design Practices
The Corvette (starting with the C4) and the Honda (nee Acura) NSX were early adopters of this geometry in production. Not sure what they did with their racing versions. Not sure if their specifications are available in the public domain.
Best regards,
Matthew Ian Loew
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Modern Spindle Geometry Design Practices
-Joest
RE: Modern Spindle Geometry Design Practices
That's why I work back from a mech trail at the ground, i bet they are both 15-35mm.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Modern Spindle Geometry Design Practices
RE: Modern Spindle Geometry Design Practices
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Modern Spindle Geometry Design Practices