Originally Posted by Rsimps

I love all this trying to use full size car theory on a model car, it works to a point.

On full size rally cars I was always work from the stiffest and lowest setup that you think will work for the conditions. That was from David Lampworth at Prodrive in the UK. They always would start a test with their most aggressive set up.

Most of the time trying to work figures out and theories is a waste of time. You generally know if you change x, y and z it has a certain effect and you are best starting with a locals setup or use the kit set up and start from there and change one thing at a time (try and get some practice days rather than race days to do this). If you have a plan of what you want to do, you can get through a full RC car in one days testing.

Its very easy to tune an RC car, not so easy on a rally car based on a production car. If I wanted to change the ackerman on my rally car we had to use the gas welding torch and a big hammer and change the rack arms. To get more rear camber we got the gas out again, drew straws and the looser had to heat the back axle tube up with a plate guarding a full fuel tank, while the lucky bloke had to use a scaffold on a hub puller to lift the car up and gain neg camber.

On a full size car we tended to reduce ackerman to reduce front inner tyre scrub on fast corners. Road cars are made so someone can park them at slow speed, so nearly always have a too tighter inner wheel radius. The only time you would want scrub was if the corners were very slippery and tight. Now if you take one wheel off the front of your RC car and run it on a flat surface you will see it turns a lot with the inside wheel, do that with a full size car and it will go straight on. RC cars use massive amounts of ackerman and inside wheel scrub, you will also see the chassis jack due to the wheel offset and castor by a massive amount too, all very unlike real cars (we ran about 3-8 deg castor and then it would rip your arms off).