I agree. ...I want the suspension to take all the bumps...not the chassis. If I understand it correctly, bigger stiffer bars would spring less, transferring all the shock to the chassis and then to my seat.
Jeff
You’re radically oversimplifying. Your slant 6 bars aren’t “taking all the bumps” either. They’re being overloaded, which causes the suspension to bottom out, which transfers suspension energy directly to the frame in the form of a violent collision. Which is exactly why you have a thread about making the ride on your car smoother, even though you have really soft torsion bars already.
These cars were undersprung from the factory. They were designed around using a bias ply tire, which has a very stiff sidewall and a fraction of the grip offered by even the BFG T/A radials most run. Thinking that you can swap out the tires and significantly change their capabilities without changing the suspension is a big mistake.
No, not everyone will want to use 1.12” bars, the car has to be built up to take advantage of bars that large. But by the same token,
no one should run /6 bars on the street with radial tires, even on an otherwise stock car. Those are just as much of a mismatch as running 1.12’s without additional modifications.
Suspension has to be matched to the rest of the car. Lower your car and run better tires, you need larger bars for the suspension to do its job. The factory suspension set up is a mismatch at that point.
This is a well-written post that I can, to a fairly large degree, agree with. See more below.
This is my point of view for 99% of our cars. As I interpreted the original post, 'I installed huge T-bars. Why is my ride so stiff?' Basic trouble-shooting still applies. Bottoming out the suspension in
any car is a
really bad thing when cornering, yet several said, 'if it's bottoming out, trim the stops for more travel' which should be a huge red flag to any
dedicated cornering enthusiast.
Chassis rigidity is a huge part of any proper-handling vehicle, and yes, our old-*** cars have plenty of flex. I agree with GMachine that increasing chassis rigidity, better tires, wider wheels, etc. opens the doors increasing spring rates, improved valving in shocks, etc. Absolutely, 100%, I agree.
That said, my point is that for most folks, they're heading towards the suspension equivalent of this:
View attachment 1715343722
Or did I mis-remember the whole '80's "Pro Street" thing?
I am 100% positive that most people that use a level of research that involves clicking a mouse on the 'add to cart' button for biggest T-bars out there. I've said for years: If somebody makes it for your car, someone out there will buy it, and install it; it doesn't matter what 'it' is. See Pro-Street comment above.
Most racers would gladly accept a spring rate that would drive 99% of the population nuts. Or else cars would already
have those rates.
I don't see anybody asking what's the final usage of the car, and
that should be the first question being asked. It sure would be if this was a cam selection question...
Unfortunately you’ve missed the mark. The OP is setting his car up for fairly aggressive street handling. I know this because we’ve had more than a few conversations on this board and by direct message. Although really you can pull most of that out of the very first post, it’s pretty clear this car is being set up for handling.
It’s also very clear in the very first post that the OP thinks there’s something going on that’s more than just “ I installed big torsion bars and the car rides stiff”. He said it rides stiffer than he expected, and that’s different. Not only that, but more than a few people that run the same or larger torsion bars as the OP have agreed with him, myself included. His issues are not because of the size of the torsion bars. He has a different suspension problem.
Your opinion on people buying large torsion bars is also just flat out misinformed. Sure, I'm sure there are some people that just buy a large torsion bar without fully understanding how to set up the rest of the suspension and chassis around that choice. But there are also a lot of people out there that have the
completely misinformed opinion that the factory torsion bars will give you the proper ride quality with radial tires. That's a far more ignorant a position than just buying a big torsion bar and expecting your car to handle well. The factory suspension was not designed for radial tires. It doesn't have the proper suspension geometry, the proper range of alignment adjustments, or a high enough wheel rate. Period. Regardless of the use of the car, if you change to radials, you should not be using the factory suspension specs. Any of them.
As for the bump stop deal, again, you're misinformed. No one here just said "if it's bottoming out cut the bump stops". It's way more complicated than that. There are VERY legitimate reasons to run shorter bump stops on an old Mopar that is being set up for handling. Back to- the factory set up is WRONG. The factory geometry sets the suspension to have positive camber gain. That's bad for radials. It sets it up with 0 or negative caster. That's BAD for radials. It used very soft torsion bars, and coupled those with very tall, soft bump stops. That's because the factory was using the bump stops as part of the suspension. They didn't have the shock technology to run large diameter torsion bars and control them well enough for a decent ride. And it was the 70's, and the novel trend at the time was a marshmallow soft suspension. So the torsion bars were small, and the bump stops were big and soft. Basically, the factory was using the bump stops as a secondary spring, and counted on them being used as part of the suspension.
Well, that's all terrible by modern standards. Add radial tires and you darn near double the grip of the original bias plys. Add radials and all of the alignment specs are wrong, you want negative camber gain and positive caster. How do you deal with that? You lower the car. With the UCA parallel to the ground the camber gain is negative. There's more caster. But you lost suspension travel. So, how do you make that up? Two ways. One, you increase the wheel rate. There isn't a modern car on the road that runs a wheel rate that isn't close to double what these cars had from the factory, it was that bad. The factory suspension needed a lot of travel because it was undersprung. Larger torsion bars up the wheel rate, and less travel is needed for the same suspension input. And then the second one, you run shorter bump stops. But that's not as big a problem as you think. The factory was using the bump stops as suspension, and a /6 car hits the bump stops all the time. We're not going to. The larger bar, paired with the shorter bump stop, better shocks, and the appropriate ride height for the wheel rate shouldn't hit the bump stops very often, if at all. So the bump stop can be smaller, as it will only be used infrequently (assuming the car is set up properly). That improves handling by itself, because you're not constantly transitioning on and off the bump stops and changing the wheel rate.
Suspension is a system, and there are always trade offs. Sure, I'd prefer to run larger bump stops than I do, because it would give me some more "wiggle room" in my ride height tuning. But I'd rather have better suspension geometry, and if I've done my research and tuned properly I'm not hitting the bump stops like a factory car. The large torsion bars are taking up all bumps, the bump stops aren't being used, and the suspension geometry is right. And not only does the car handle better, it RIDES better than some /6 torsion bar car that's beating the bump stops to death on a trip around the block.
