Let's talk anti-roll bars

[Ron Sutton]

Hey Tom,



When you removed the rear sway bar, what changed in your handling specifically ?

[Tomswheels]

With sway bar on the car was always oversteering. Rear broke away early and often. Taking it off made the car lean more, but stick better.

[Ron Sutton]

With sway bar on the car was always oversteering. Rear broke away early and often. Taking it off made the car lean more, but stick better.

Thanks. That's the normal affect for a stock suspended car.

[iadr]

I just wanted to say (aside from sorry if I came off rude with Tom's car- they say sarcasm is lost on the autistic. Certainly, if there's a spectrum, I'm over on that end... :( ) that I found the explanation of why SAI stuffs the outside tire into the pavement, one of the few things Ron sort of glossed over. I'd thought about it for what a couple weeks now? And didn't "get it" until an hour ago.
Figure 5 here: (I didn't even need to get to 6-10, I had my a-ha! moment before I scrolled):
http://www.ismasupers.com/downloads/...ations%204.pdf
The spindle's snout (being a traditional spindle illustrated, not a bolt on hub type) being at an angle is really what "does it", or rather, that, as the complete knuckle rotates the "theoretical" 90 deg, the SAI goes from its true angle to being, as viewed from the side, vertical. And the snout's previously "appropriate" built-in angle..., well, you wish it would go away. lol
This is harder to explain than I thought.

Anyway, I was wondering if Ron you felt like commenting on: if a close to Zero SAI spindle would be ideal for street/Autocross. Or why you wouldn't want that. ??? I have an interesting project on a non-protouring vehicle, which is to adapt Lexus IS-AWD front spindles and upper arms in place of a macpherson strut. The parts are one of those tall spindles with the "hook" at the top putting the upper BJ overtop the inner tread blocks of the tires. Just a conventional 10.5* SAI, but it looks like they could have gone further out with the upper BJ and reduced the SAI if they wanted too. They compete with the German cars that use two separate upper BJ's to (at least to my eyes) put the effective upper BJ location well out over the tire. Are you familiar with what I mean? Theoretically, you could do a conventional lower BJ, and one of those up top to have Zero SAI. Would your steering feel be poor? (not that it's that great on the last few year's car's anyway... you get on local snowy roads here in Canada with a car with 40-series tires and a 10:1 steering ratio+electric boost, and little body roll, and you have zero progessiveness, or ability to finesse-catch it...because the reactions are all moved up to high G points. Back in the day street cars gave feedback at like .15-.2G. Not anymore.)
I gather of bits of the puzzle from places as disparate as Edmunds Suspension walk arounds, and the Locost Lotus seven replica building community.
On the former, here are a couple interesting ones:
http://www.edmunds.com/car-reviews/t...alkaround.html
http://www.edmunds.com/car-reviews/t...alkaround.html
The second has an animated .GIF picturing the one thing I mentioned.

[iadr]

Hmm, watching the BMW .gif, I think I need help understanding what is going on. It is not as simple as moving out the pivot point, because at higher angles the pivot tucks *inside*. Hmm.

(???)

[Ron Sutton]

I just wanted to say (aside from sorry if I came off rude with Tom's car- they say sarcasm is lost on the autistic. Certainly, if there's a spectrum, I'm over on that end... :( ) that I found the explanation of why SAI stuffs the outside tire into the pavement, one of the few things Ron sort of glossed over. I'd thought about it for what a couple weeks now? And didn't "get it" until an hour ago.
Figure 5 here: (I didn't even need to get to 6-10, I had my a-ha! moment before I scrolled):
http://www.ismasupers.com/downloads/...ations%204.pdf
The spindle's snout (being a traditional spindle illustrated, not a bolt on hub type) being at an angle is really what "does it", or rather, that, as the complete knuckle rotates the "theoretical" 90 deg, the SAI goes from its true angle to being, as viewed from the side, vertical. And the snout's previously "appropriate" built-in angle..., well, you wish it would go away. lol
This is harder to explain than I thought.

Anyway, I was wondering if Ron you felt like commenting on: if a close to Zero SAI spindle would be ideal for street/Autocross. Or why you wouldn't want that. ??? I have an interesting project on a non-protouring vehicle, which is to adapt Lexus IS-AWD front spindles and upper arms in place of a macpherson strut. The parts are one of those tall spindles with the "hook" at the top putting the upper BJ overtop the inner tread blocks of the tires. Just a conventional 10.5* SAI, but it looks like they could have gone further out with the upper BJ and reduced the SAI if they wanted too. They compete with the German cars that use two separate upper BJ's to (at least to my eyes) put the effective upper BJ location well out over the tire. Are you familiar with what I mean? Theoretically, you could do a conventional lower BJ, and one of those up top to have Zero SAI. Would your steering feel be poor? (not that it's that great on the last few year's car's anyway... you get on local snowy roads here in Canada with a car with 40-series tires and a 10:1 steering ratio+electric boost, and little body roll, and you have zero progessiveness, or ability to finesse-catch it...because the reactions are all moved up to high G points. Back in the day street cars gave feedback at like .15-.2G. Not anymore.)
I gather of bits of the puzzle from places as disparate as Edmunds Suspension walk arounds, and the Locost Lotus seven replica building community.
On the former, here are a couple interesting ones:
http://www.edmunds.com/car-reviews/t...alkaround.html
http://www.edmunds.com/car-reviews/t...alkaround.html
The second has an animated .GIF picturing the one thing I mentioned.

When I'm designing a race car with no rules limiting me on spindles or control arms ... I am using custom built spindles with very low KPI/SAI ... long control arms pushing the ball joint out & deep back spaced wheels ... to arrive at zero scrub radius. You don't need any more KPI angle than necessary to achieve a zero scrub radius.

I personally have no experience with a zero KPI spindle, and could not tell you if there are any issues. I have no experience going that low, because I haven't been in a situation where zero KPI would get me zero scrub radius. Zero scrub radius is the primary goal.

I have several projects where we achieved zero scrub radius with 3 degree & 5 degree KPI spindles. As long as we can achieve a zero scrub radius set-up ... and the caster can be adjusted 1-2 degrees more than KPI ... one isn't necessarily better than the other.

[Ron Sutton]

Hmm, watching the BMW .gif, I think I need help understanding what is going on. It is not as simple as moving out the pivot point, because at higher angles the pivot tucks *inside*. Hmm.

(???)

I did not understand this message. Is there a BMW.gif on this thread? If yes, in what post?

[Norm Peterson]

It's not in any post here.

Look about a quarter of the way down the BMW suspension walkaround link http://www.edmunds.com/car-reviews/t...alkaround.html for a picture that animates automatically.


Norm

[Ron Sutton]

It's not in any post here.

Look about a quarter of the way down the BMW suspension walkaround link http://www.edmunds.com/car-reviews/t...alkaround.html for a picture that animates automatically.

Norm

Thanks Norm. That's pretty cool.

Iadr, I couldn't speak intelligently on the BMW suspension that has a dynamic scrub radius, as I have no experience with it. But it's looks neat.

.