1969 Torino

[carbuff]

Wow... Ask what I thought was a pretty simple question, and I got an amazingly detailed answer! Thank you for taking the time to explain all of that! I've read it twice, and I'm still absorbing it, but your explanation made sense and was very well presented!

I think the next thing I need to figure out is what scrub radius I actually have now. It sounds like that would be one of the next big factors in the equation...

Thanx again!

[carbuff]

On the subject of caster, I do have another question...

I've heard that changing the amount of caster has an impact on the 'feel' of the steering. I've also heard that caster is often used in a street alignment to offset the irregularities that we may experience when driving down the road.

Can you touch on either or both of those, particular how either would relate to the KPI / SAI as you explained them above? Is there a crossover point, for example, on how increasing / decreasing the caster will affect the steering 'feel'? I ask partly because if that's true, I wonder if you can hit a point where we might 'overwork' the steering rack we are using? In other words, I would guess that if we make a change to the caster that causes us to have to use more force to turn the wheels, are we possibly putting more pressure on the rack, and risk damaging it?

I'm thinking out loud with that question, so perhaps it's irrelevant... But in my case, since I'm using a Ford rack that was likely never built to take much abuse, I wonder if that can become a problem?

[Ron Sutton]

Hi Bryan,

On the subject of caster, I do have another question...

I've heard that changing the amount of caster has an impact on the 'feel' of the steering.
More caster increases the feel of the track in the steering wheel ... communicating to the driver what the front end is doing. Less caster decrease this feel.

More scrub radius increases the feel of the track in the steering wheel ... communicating to the driver what the front end is doing. Less scrub radius decrease this feel.

Since reducing scrub radius is good for turning ability ... but takes away the feel ... and adding caster also helps the turning ability ... and returns the feel ... these are two good tuning changes to do together. .

I've also heard that caster is often used in a street alignment to offset the irregularities that we may experience when driving down the road.
What your referring to is factory passenger car settings to help the car drive straight on roads that are crowned. Some mechanics like to put a little more caster in the RF wheel to offset this ... others prefer to add a little static camber in the RF to achieve this.

I'm a race car designer & crew chief, focused on track cars, so we don't do this on road course or AutoX cars ... just oval track cars.

Can you touch on either or both of those, particular how either would relate to the KPI / SAI as you explained them above? Is there a crossover point, for example, on how increasing / decreasing the caster will affect the steering 'feel'? I ask partly because if that's true, I wonder if you can hit a point where we might 'overwork' the steering rack we are using? In other words, I would guess that if we make a change to the caster that causes us to have to use more force to turn the wheels, are we possibly putting more pressure on the rack, and risk damaging it?
That question reminds me of a guy one time buying a large duration, high lift, "mean" aggressive inverted flank ramp roller cam to build optimum power in his 434" SBC ... and then asking how the fuel mileage would be?

Yes, almost anything you do to make your front end grip more & turn better, is going to put more load on the steering box. Wider tires, grippier tires, wheels with the width wider than the tread width, low profile tires, faster steering ratios, more caster, more camber, bigger sway bars, springs & shocks to provide grip, etc, etc, etc.

About the only thing that will help the car turn better & not increase the load on the steering box is reducing scrub radius.

I'm thinking out loud with that question, so perhaps it's irrelevant... But in my case, since I'm using a Ford rack that was likely never built to take much abuse, I wonder if that can become a problem?[/QUOTE]
That's smart thinking. If you build a mean handling machine & utilize a small, moderate duty steering box, you could have issues.

What R&P do you have ?

.

[Flash68]

Originally Posted by carbuff

But in my case, since I'm using a Ford rack that was likely never built to take much abuse, I wonder if that can become a problem?

I am assuming you (and I) have the same rack that Jake used (and still is being used by Vinny in AIX) ?

[FETorino]

Ron

It is enlightening to see the full discussion of KPI/SAI & caster and it's relationship to camber laid out in an easy to digest discussion.

I'm tempted to cut and paste your roll center discussion on here also but maybe I should leave that to you.

Reading this reminds me of why I reached out to you. A statement made by Carroll Smith in Tune to Win. c.1978. He was speaking of purpose built race chassis. More narrowly focused than the quality pices of engineering available to the PT market.

"What you can buy is a starting point. In a really competitive class of racing it is unlikely to be capable of winning races out of the box. Development is up to you. You will do it by tuning"

Even with a Camaro there are many variables introduced by the owner that a suspension designer cannot account for. And every design brought to mass market is a compromise that will work for the whole market.

What most of us have from the vendors is a good or great starting point. But if you really want it to work, to the nth degree, you have to invest some time to understand what you really have and how to tune it.

With nothing more than a proper install, most, if not all, of these systems would produce a more than competent street car with good manners and ride. But then some people just have to really beat on their stuff.

Instead of race class rules there exists another set of limitations dictated by style and some minimal rules such as tire compounds.

I really enjoy your willingness to post some of the thought process of how to squeeze more blood out of the Turnip or in this case the Torino.

I have plenty left to do on this build and plan on continuing to post all of tweaks that I hope in the end will result in a very competent big boned girl.

[MX145]

Originally Posted by FETorino

Ron

It is enlightening to see the full discussion of KPI/SAI & caster and it's relationship to camber laid out in an easy to digest discussion.

I'm tempted to cut and paste your roll center discussion on here also but maybe I should leave that to you.

Thanks for getting this started Rob!
Ron, I greatly appraciate the information. Roll center please!

[Ron Sutton]

Originally Posted by FETorino

Ron

It is enlightening to see the full discussion of KPI/SAI & caster and it's relationship to camber laid out in an easy to digest discussion.

I'm tempted to cut and paste your roll center discussion on here also but maybe I should leave that to you.

Reading this reminds me of why I reached out to you. A statement made by Carroll Smith in Tune to Win. c.1978. He was speaking of purpose built race chassis. More narrowly focused than the quality pices of engineering available to the PT market.

"What you can buy is a starting point. In a really competitive class of racing it is unlikely to be capable of winning races out of the box. Development is up to you. You will do it by tuning"

Even with a Camaro there are many variables introduced by the owner that a suspension designer cannot account for. And every design brought to mass market is a compromise that will work for the whole market.

What most of us have from the vendors is a good or great starting point. But if you really want it to work, to the nth degree, you have to invest some time to understand what you really have and how to tune it.

With nothing more than a proper install, most, if not all, of these systems would produce a more than competent street car with good manners and ride. But then some people just have to really beat on their stuff.

Instead of race class rules there exists another set of limitations dictated by style and some minimal rules such as tire compounds.

I really enjoy your willingness to post some of the thought process of how to squeeze more blood out of the Turnip or in this case the Torino.

I have plenty left to do on this build and plan on continuing to post all of tweaks that I hope in the end will result in a very competent big boned girl.

Hi Rob,

Thanks for the kind words.

Your points are all spot on. If you want to optimize performance, you need to tune & test. I have always found the people that do that most, are the ones to beat.

P.S. Love Carroll Smith's books. I read them in 1980 & it set me on the path to design, build & tune race cars the way I do.

.

[Ron Sutton]

Guys,

I'm getting conflicting information on the C6 spindle KPI angle. So take that into account when reading #1234 & #1235.

If the KPI #'s I have been given are incorrect, I will correct the KPI # & the equation in these posts and let everyone know.

.

[Ron Sutton]

Originally Posted by FETorino

Ron

It is enlightening to see the full discussion of KPI/SAI & caster and it's relationship to camber laid out in an easy to digest discussion.

I'm tempted to cut and paste your roll center discussion on here also but maybe I should leave that to you.

Rob that's a good idea.

I'll add in the roll center information after we have fully discussed this topic first.

[Flash68]

Ron,

Since you've entered Rob's world I think some people might actually be scared of this big boned girl.