Riddle Me This

[kyepan 291]

Used to have the MX-5 set up lovely, very neutral, and temptable into oversteer if required on private runways / private tarmac.

 

It was set up with

 

front

-1.5 deg camber

-4.5 deg caster

0.05 deg toe in

 

Rear

-2.0 deg camber

0.05 deg toe in

 

 

i got it aligned and fluffed it up by asking for toe out at the rear and front, which resulted in a superbly stable rear, under-steery but nervous front.

 

Just had it put back to how it was before, the front is more stable, and the rear has more life.

 

All is good in the world.

 

Question is, how can 0.05 deg of toe out at the rear have such a profound effect upon it's stability?

 

 

J

[EdCherry 34 1 Cars]

The heaps of compliance in bushes probably comes into question here, and give the huge variation of feel you've experienced.

[kyepan 291]

possibly, granted it is a mk1, but I have a tight bush. I mean my bush hasn't done many times around the block.. 45 thousand miles.

 

erm..

 

However i know what you mean, and i know what i feel, and it's not my .. erm .. Bush-es.

 

back to back testing.. showed that just tweaking the toe transformed how it handled... only change was the front and rear toe.

 

I just want to know why..

Edited December 23, 2011 by kyepan

[Paul_13 212 1 Cars]

Time to go slideways again? Bit dissapointing that last effort

[Anthony 1,003]

i got it aligned and fluffed it up by asking for toe out at the rear and front, which resulted in a superbly stable rear, under-steery but nervous front.

Given your track record J, perhaps you subconciously asked for that so you'll keep it both on the road and pointing the right way for once?

 

Surprising that just 0.1 degrees had such an impact though, even considering that you were going from toe-out to toe-in Certainly that sort of difference seems to have very little noticeable effect on a 205, although I appreciate that an MX-5 is a different animal entirely.

 

Definitely 0.05 degrees though, as 0.5 toe-in to 0.5 toe-out (ie 1 degree total) would be much more noticeable...

 

PS. Where did you get it setup, as I probably should do my '5 when I pull it out of hibernation next year after giving all the bushes/balljoints a once over.

[kyepan 291]

yes probably 0.5, but it came up as 0.05 on the screen, so perhaps it measures in minutes... or seconds.. or whatever the larger denomination is!! inches.. it's all greek to me.. and mostly skued by american imperial measurements.

 

look up the Miq setup, but bear in mind, ours are both lowered.. rule of thumb is 0.5 deg more camber at the rear than the front an as much caster as you can get. Toe out at the front, and in at the rear.. as much as you want to wear out your tyres.

 

The one time i did manage to get it sideways with the intervening setup, it was gradual and controllable, now it is a trifle more snappy.

 

I'll ignore the comment about my driving, I am not a driving god, and I worship at the cold steely alter of the armco ;-)

 

he he,

 

J

[Baz 421]

You'll never be a 'driving god' if you don't embrace the armco every now and again!!

[kyepan 291]

embrace the armco

 

is exactly the phrase i was originally going to use.