Up until now, I've been making very few changes to the setup of my RF89 Van Diemen. Make sure the tires are pointed pretty much straight ahead, and pretty much vertical (the car came with 0 degrees camber at each corner), and go out and get some seat time.
But the time has come to make some adjustments. I've got information from Van Diemen International about the initial recommended setup for the RF89, but:
It occurred to me tonight that the setup numbers I've been given were based on tire sizes that were at least potentially quite different than what we use on FFs now. So I did a little checking and sure enough: using Avon's tires for "historic" FFs and and even their more modern ford tires, the tires my Van Diemen was probably set up to use were enough different to give me some pause for thought.
In particular, when I look at the recommended rake in the setup notes, it's based on front to rear tire sizes that result in about one half an inch of the ride height difference coming from the different tire radii front to rear. But my American Racer tires have more like a full inch difference in radius front to rear. So this is my question:
Am I right in thinking that if I want a certain amount of rake to set the suspension geometry properly, then if the new tires have an inch difference where the original tires had only half an inch, then I need to add that difference into the rake.
In other words, if Van Diemen was recommending ride heights of 1-11/16" Front / 2-1/4" Rear for a rake of 9/16" for tires where the radius difference was 1/2", then I need to have a rake of about 1-1/16" to match the geometry they were intending with tires that are 1" different in radius?
Does that make sense?
But the time has come to make some adjustments. I've got information from Van Diemen International about the initial recommended setup for the RF89, but:
It occurred to me tonight that the setup numbers I've been given were based on tire sizes that were at least potentially quite different than what we use on FFs now. So I did a little checking and sure enough: using Avon's tires for "historic" FFs and and even their more modern ford tires, the tires my Van Diemen was probably set up to use were enough different to give me some pause for thought.
In particular, when I look at the recommended rake in the setup notes, it's based on front to rear tire sizes that result in about one half an inch of the ride height difference coming from the different tire radii front to rear. But my American Racer tires have more like a full inch difference in radius front to rear. So this is my question:
Am I right in thinking that if I want a certain amount of rake to set the suspension geometry properly, then if the new tires have an inch difference where the original tires had only half an inch, then I need to add that difference into the rake.
In other words, if Van Diemen was recommending ride heights of 1-11/16" Front / 2-1/4" Rear for a rake of 9/16" for tires where the radius difference was 1/2", then I need to have a rake of about 1-1/16" to match the geometry they were intending with tires that are 1" different in radius?
Does that make sense?
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