Castor for 39's

[Z()LTAN]

Castor angle for my cruiser?

what Castor should i run for 39" tires?

positive how much?

[ats4x4dotcom]

We like to run around 2.5 deg castor, and around 4-5mm toe in with that size tyre and lift to suit.

We also like to run 1-1.5 deg neg camber so they turn in.

[ChrisV]

What does "toe in" and "camber" mean?

I think castor is the angle the diff points up at the gearbox right?

Does "toe in" mean the front tires are slighty pigeon toed?

And camber is the angle they tyres sit related to the diff isn't it? eg /--o--\ instead of them being straight like |--o--|.

Am I right?

[Z()LTAN]

your right on the money there Chris.

But castor is measured on the kingpin axis not the pinion angle axis.

thus the need for a Cut and Rotate

[ChrisV]

OK I get it I think.

Sorry for hijacking this thread but I'm about to SOA my FJ40 and put 38.5's on it too and I want to get it right.

When I cut and rotate do I need to make the king pin directly vertical or slightly offset. Is this what castor angle refers to?

[Z()LTAN]

Yep exactly.

You need some positive castor, ive been told between 5-7 degrees

this may help you

[rickzta]

dont go 5-7 deg castor...

it will turn in great at high speed ie 150-200km/h

but will be a bit@h to turn at low speed

the more castor the heavier the steering.

cheers

ricky

[ChrisV]

Why do I need castor at all? can't I just have zero castor?

I disagree with your theory rickzta. Positive castor will make it similar to the rake angle of a motorcycle front wheel. The faster you go the more stable it will be but will turn in faster at low speed and less likely to straighten up when you let go of the wheel.

That's not fact, just what I reckon....

[bazooked]

the more castor the more stable at staight line speed and the more centering effect you will have at the steering wheel at any speed, this is fact, but dont overdo it with castor.

[ChrisV]

Cool.

Thanks for your help.