Vixen suspension data
Discussion
I can't understand why the fronts are supposed to be up to 1.5def positive. I'm sure it's the same on our data sheet for the 1600M. Why would anyone want positive camber on the front wheels?!
Took ages to persuade Dad to wind it back to at least vertical, and it still needs a bit more neg if the pictures from the trackdays we've done are anything to go by,
Took ages to persuade Dad to wind it back to at least vertical, and it still needs a bit more neg if the pictures from the trackdays we've done are anything to go by,
Cerberus90 said:
I can't understand why the fronts are supposed to be up to 1.5def positive. I'm sure it's the same on our data sheet for the 1600M. Why would anyone want positive camber on the front wheels?!
Took ages to persuade Dad to wind it back to at least vertical, and it still needs a bit more neg if the pictures from the trackdays we've done are anything to go by,
It relates to the factory's expectation of camber gain, with standard road set-up (including period tire technology). It translates to yaw response/predictability at corner entry and exit as much as anything else. I'm sure they did R&D on it, and came up with a compromise that related to the expected style of ROAD use. Took ages to persuade Dad to wind it back to at least vertical, and it still needs a bit more neg if the pictures from the trackdays we've done are anything to go by,
I'll guess that your dad's car isn't using period tyres, springs, shocks, and, possibly ride height. So, having changed almost all parameters, you'll get to do your own development.
Also, factory recommendation for at least some of the Ms is -.5 deg., front and rear.
Consider that even if you ONLY changed side wall stiffness, it could have a big impact on feel.
Best,
B.
Yes, your right, we've got modern yoko tyres on it and modern shocks.
I suppose that's probably right. The car being nearly twice as old as me, I have no experience of old flexy tyres etc,.
So when in the turn, the inside wheels tyre could be too far out past the rim (like trying to come off) if there was too much neg camber. So the positive camber makes the tyre further in, so when it gains neg camber mid bend it doesn't come off the rim?
(not easy to explain this,).
So with 0 camber, the tyre could do this?
Crude drawing,
<outside
| rim |
_| _|
/ /
/ tyre /
I suppose that's probably right. The car being nearly twice as old as me, I have no experience of old flexy tyres etc,
.So when in the turn, the inside wheels tyre could be too far out past the rim (like trying to come off) if there was too much neg camber. So the positive camber makes the tyre further in, so when it gains neg camber mid bend it doesn't come off the rim?
(not easy to explain this,
).So with 0 camber, the tyre could do this?
Crude drawing,
<outside
| rim |
_| _|
/ /
/ tyre /
Rather than get too far into theory, which I'm sure I don't understand near well enough, I'd say take pyrometer readings (@ right, center, and left side of tyre) at the track, and adjust the camber and pressures accordingly. Record the car set up*, tyre pressures, tyre temp readings, ambient temp., track temp., (... ad nauseam). It's likely that some generous soul has dumped their Excel template on the web. Get one you like, and use it. It will help you get a base set up for each track. No point in re-inventing the wheel (uh, pardon the bad pun).
*as well as getting detailed chassis geometry information on a true chassis set-up plate (all from referenced datum points), it's possible to shunt, and repair the car back to the original set-up. That way, your work won't be lost.
Most importantly, don't listen to me; I've no real-world experience setting up a car for the track. Instead, get some books on chassis set-up. I hear the Milliken and Puhn volumes are what a lot of people recommend, to gain a good understanding.
Also, pay attention to how toe settings affect turn-in feel, and stability and feel, before the car takes a set.
Best,
B.
*as well as getting detailed chassis geometry information on a true chassis set-up plate (all from referenced datum points), it's possible to shunt, and repair the car back to the original set-up. That way, your work won't be lost.
Most importantly, don't listen to me; I've no real-world experience setting up a car for the track. Instead, get some books on chassis set-up. I hear the Milliken and Puhn volumes are what a lot of people recommend, to gain a good understanding.
Also, pay attention to how toe settings affect turn-in feel, and stability and feel, before the car takes a set.
Best,
B.
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