12:05 Garage- ’70 Duster build
Here's one from one of the T/A or AAR cars, it was in a Mopar Action article. The sway bar tube runs right through the K and is braced. Also shows the notch in the frame where the factory cars have the frame stop for the LCA bump stop, not only is that gone but the notch allows even more suspension compression travel. On an A-body that notch would probably put the tire into the inner fender on full compression even with a stock LCA.
The kit car/circuit car stuff is pretty interesting, there's some really cool tricks in there but really at this point with the parts available today a lot of the stuff they did isn't relevant anymore, or isn't relevant to a street car. It's helpful to understand the suspension and the chassis some, and then there's just the wow factor of seeing a part number for a 1.64" diameter torsion bar with a 1,455 lb/in rate!
I ran a 270 lb/in wheel rate on my Challenger for the entire 70k+ street miles I put on it. It was a decent wheel rate for a street car, once I ditched the KYB's and added RCD Bilsteins the ride improved to the point that I was ready to up the torsion bar size again. With a set of 200 tread wear tires on an autoX course it would probably be a bit light. I think 300 lb/in is a better starting point, and honestly for a dedicated autoX car that's probably the light end of the range. For a car that still sees the street I don't know how high you'd want to go, I guess I'll find out when I fit my 1.18's (370 lb/in rate).
The problem with a good progressive bump stop is they're tall, they need room to work. And on these cars with only like 5" to 5.5" of travel you don't have a lot of travel to give up to bump stop, unless you want to be constantly using them. It's one thing on an off-road vehicle running high speeds with a long travel suspension set up, it's something else on a car that gets used on the street and has a fairly limited amount of suspension travel. Personally I'd rather tune the suspension with the wheel rate to use almost all of the available travel and limit bump stop use, rather than figure in the progressive rate of the bump stops in that last bit of travel. But that's my opinion, and there are definitely some different takes on how to set a car up. On that note...
Birdsong is junk science. He throws around a lot of technical terms that he's using incorrectly and reveals exactly NONE of his actual geometry data while making wild unsupported claims. The few things he gets right he explains incorrectly so I have to assume he stumbled into something that worked just by sheer luck. And he clearly skips past signifiant issues with his own set up. Good for youtube views I guess, but that's about it.
Here's one from one of the T/A or AAR cars, it was in a Mopar Action article. The sway bar tube runs right through the K and is braced. Also shows the notch in the frame where the factory cars have the frame stop for the LCA bump stop, not only is that gone but the notch allows even more suspension compression travel. On an A-body that notch would probably put the tire into the inner fender on full compression even with a stock LCA.
The kit car/circuit car stuff is pretty interesting, there's some really cool tricks in there but really at this point with the parts available today a lot of the stuff they did isn't relevant anymore, or isn't relevant to a street car. It's helpful to understand the suspension and the chassis some, and then there's just the wow factor of seeing a part number for a 1.64" diameter torsion bar with a 1,455 lb/in rate!
I ran a 270 lb/in wheel rate on my Challenger for the entire 70k+ street miles I put on it. It was a decent wheel rate for a street car, once I ditched the KYB's and added RCD Bilsteins the ride improved to the point that I was ready to up the torsion bar size again. With a set of 200 tread wear tires on an autoX course it would probably be a bit light. I think 300 lb/in is a better starting point, and honestly for a dedicated autoX car that's probably the light end of the range. For a car that still sees the street I don't know how high you'd want to go, I guess I'll find out when I fit my 1.18's (370 lb/in rate).
The problem with a good progressive bump stop is they're tall, they need room to work. And on these cars with only like 5" to 5.5" of travel you don't have a lot of travel to give up to bump stop, unless you want to be constantly using them. It's one thing on an off-road vehicle running high speeds with a long travel suspension set up, it's something else on a car that gets used on the street and has a fairly limited amount of suspension travel. Personally I'd rather tune the suspension with the wheel rate to use almost all of the available travel and limit bump stop use, rather than figure in the progressive rate of the bump stops in that last bit of travel. But that's my opinion, and there are definitely some different takes on how to set a car up. On that note...
Birdsong is junk science. He throws around a lot of technical terms that he's using incorrectly and reveals exactly NONE of his actual geometry data while making wild unsupported claims. The few things he gets right he explains incorrectly so I have to assume he stumbled into something that worked just by sheer luck. And he clearly skips past signifiant issues with his own set up. Good for youtube views I guess, but that's about it.