12:05 Garage- ’70 Duster build
I agree the 270 is a bit on the low end but they are for sure better than the 109 lb bars that are currently in there. I got the TBs a long time ago and have a lot of other things higher on the spend money list than slightly changing the spring rate for now. now if I find someone who wants to trade or a smoking deal on some big bars that may change haha.
I also agree on your take of most of the stuff Birdsong does. I actually commented on one of his videos to explain some of the downsides of his "magical balljoint drop plates" which I feel are a downgrade in geometry. Probably will get lost in the comments though. oh well.
Oh for sure, you can do a lot with a 270 lb/in wheel rate. And the whole spring rate vs sway bar rate balance is something that even the really knowledgeable/experienced racers still disagree on, you have folks with tons of race experience in each camp for big springs/tune with sway bars and big sway bars/tune with springs. There's an article in the June '81 Hot Rod magazine that's a shootout between Dick Gulstrand and Herb Adams, with Gulstrand believing in poly bushings, high spring rates and sway bars for tuning only, with Adams being in the rubber bushings, stock (ish) springs, stiff shocks and giant sway bars camp. It's a Camaro shoot out, and there were other non-matching modifications to the cars that are not insignificant, but after comparing cars with very different set ups the result was the cars put down almost identical lap times, with each matching the driver's preferences for handling feel.
With a 270 lb/in rate you’d be in the ballpark for sure, if you could come up with a sway bar large enough it would be fine as long as you maintain some suspension travel. But I think you’d need a splined sway bar set up to do that, the off the shelf bars may not quite be enough. Still, you’d be able to do a lot with that set up.
I really don’t see how the ball joint drop is any significant improvement in geometry like he claims, especially since some of the conditions that he claims happen with the stock suspension don’t actually happen (positive camber gain, for example, isn’t a thing at all even after a 1” ride height drop). He makes claims that are flat out false about the geometry of the stock system and then makes really dramatic, unsupported claims that don't necessarily match up with the geometry he's changing. Based on what I've seen for geometry changes with a drop spindle, I'd think that his ball joint drop is likely to induce MORE bump steer, not less. That effect may be offset by the effective height of the spindle being taller, but that's something you'd have to see in the numbers, which he doesn't give.
Yeah, they essentially did a body lift in relation to the suspension. I'm assuming for tire clearance?
In general for higher spring rates you have to have a stiffer shock to control the oscillation force. So if you have a higher spring rate and more force and you are already at the top of your adjustment range you would likely have to look at re-valving or changing shocks.
I’m not positive with a B body, but with an A body and an E body I know that the tire clearance to the inner fender at full compression is an issue with a lowered car. If you alter the suspension travel so you get more compression the inner fender quickly becomes a limiting factor. My Duster is lowered about 2" and with a 25.6" tire and QA1 LCA's and modified bump stops heights my tires will just kiss the inner fender at full compression. Lower would require raising the inner fenders.
Thing is, raising the body with relation to the K and suspension also raises the the CG. And he hasn’t raised the engine, so, the header to ground clearance is still an issue. I mean, on my car I’m sub 4” from header flange to ground at ride height. With a couple inches of compression travel that doesn’t leave the hard parts very far off the tarmac. He claims he has 1” of clearance at full compression, but in the one video you can literally see and hear the header clanking on the ground. Even if he’s got 1” a moderately bumpy road could easily ground him out. On a street car you have to pay attention to your ground clearance at full compression, especially if you're running lower wheel rates. It's not like we're driving F1 cars on the track, if you go through a dip and bottom your suspension AND hard parts it could be a bad day for you.