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Re: Chassis stiffening for street car

Posted: Sat Jun 03, 2017 3:27 pm
by John Wallace
There is also a reason the Vettes change to a solid axle when drag racing?

I figured the Mustang change was for street use or road racing type use, for turns?
(for the factory reason)


Re: Chassis stiffening for street car

Posted: Sun Jun 04, 2017 7:02 pm
by Brian P
One would expect a solid rear axle to be better for drag racing for two reasons (1) less stuff to break (no CV joints), and (2) it is possible to have a decent amount of anti-squat in the geometry while still allowing suspension compliance (IRS causes the torque reactions at the diff to go straight into the chassis and these reaction forces therefore cannot be used to influence the suspension). I'm not a drag racer but I've still heard plenty of complaints about wheel hop from those who do, on various IRS-equipped rear drive cars.

If the intent is to go around corners then the balance tips to IRS. But it isn't an absolute necessity. The S197 Mustang handles very well. The 3-link-plus-panhard arrangement allows good toe control, has minimal binding, and avoids having the roll center too high, and it can be set up with anti-squat if you wish. The merits of this suspension design have been discussed before.

The limitation is still what happens on choppy surfaces. A live rear axle is a whole bunch of unsprung weight no matter how you slice it.

Still, on this car, I would consider a live axle to be "period correct", if you wish, and certainly easier to integrate into the design and probably easier to make it work properly.

Re: Chassis stiffening for street car

Posted: Mon Jun 19, 2017 11:27 am
by pdq67
How's this thread coming along?


Re: Chassis stiffening for street car

Posted: Tue Jun 20, 2017 7:51 am
by BobbyB
I am enjoying my my comet more than ever. I had weldcraft widen a couple of wheels to fit 235-50-15 r888 tires to the rear and put 205-60-15 advan ao48 in the front. I have put 500 miles on them in about a month never getting more than 20 miles from home. These tires cost a lot and won't last long but i am having a blast with them.

Tomhorn, any falcon leads?

Re: Chassis stiffening for street car

Posted: Tue Jun 20, 2017 8:16 am
by n2xlr8n
BobbyB wrote: Tomhorn, any falcon leads?
I hope he read what I suggested, anyway.

Re: Chassis stiffening for street car

Posted: Sun Jul 02, 2017 2:38 pm
by tomhorn1913
Still here,

Still reading, thanks. Got side-lined on planning a new house for the missus, so the Falcon project got moved to the back burner. As a result, I've shown up a day late on a couple of promising prospects. I continue to process the thought-provoking input.

Thanks guys!

Re: Chassis stiffening for street car

Posted: Mon Jul 03, 2017 4:29 pm
by BobbyB
The wife & I took the Comet to the Blue Ridge Parkway yesterday evening. It is about 60 miles from our house, the "Feels Like" temp went from about 90+ degrees to about 75 degrees in about an hour and 2500 feet of elevation. The car did great on the curvy roads. I really enjoy the 3 link. Tom, why the "tomhorn1913" handle? Are you a long range shooter? I hope you find your falcon soon.

Re: Chassis stiffening for street car

Posted: Thu Jul 27, 2017 10:47 pm
by tomhorn1913

I'll "shoot" you a PM...


Re: Chassis stiffening for street car

Posted: Sun Aug 20, 2017 12:06 pm
by peejay
PackardV8 wrote:Seeing a '63-65 Falcon or '65-68 Mustang stripped to the tub is scary. There's nothing there but bent tin and not much of that. ... shell.html

Rather similar to the Falcon/Mustang but with strut suspension instead of control arms for even more weight savings.

Firmly remember a long time ago someone posting that Ford engineers have made a science out of using not enough sheetmetal, but putting a fold here and a crease there makes it sturdy enough to work in the real world.

Re: Chassis stiffening for street car

Posted: Wed Jul 18, 2018 9:24 pm
by tomhorn1913
I'm back...

No, really - keep your seats. Thank you everyone. Thank you.

Finally located a '64 Falcon Sprint. Needs just about everything, but the unibody is nearly pristine. A blank canvas to paint pretty much whatever picture I like. But back to that later. I need to hijack my own thread.

I picked up a rebuilt steering box. 19:1 ratio, I believe, 5 turns lock-to-lock. Problem(?) is, at the mid-point, there is a barely detectable bump in the otherwise smooth rotation of the steering shaft. Anyone had any experience with a 60s Ford steering box that would make them think this is "normal?" I don't want to install this box, or return my core, if I need to be returning the rebuilt unit.

Much obliged,

Re: Chassis stiffening for street car

Posted: Fri Jul 20, 2018 8:50 am
by mk e
tomhorn1913 wrote:
Wed Mar 15, 2017 12:05 am

I'll throw in another twist. After a couple weeks of internet research, I've found a few folks who are completely unapologetic in their condemnation of roll bars/cages in street-driven vehicles. They point out that a roll bar or cage is unsafe without a helmet, due to the risk of severe head injury in ANY vehicular mishap. I must admit to having bounced around in a few minor crashes, & discovering mystery bruises a couple days later, from striking parts of my body on who-knows-what in the cabin. The prospect of kissing a steel tube (even one wrapped with approved roll bar padding) with my melon, strikes me (pun intended) as, wellllllll - "bad"...

That's all true....but modern cars have what is effectively a cage built into the structure and they are safe. If you know it's a street car that will be driven without a helmet then you need to design the cage accordingly to prevent all the concerns you mention....a cage like structure is the only practical way to stiffen that car.

Re: Chassis stiffening for street car

Posted: Sat Jul 21, 2018 12:19 am
by tomhorn1913

Yeah, I'm still inclined toward a basic cage, with the main hoop moved rearward as far as possible, without completely defeating its purpose. I'll be deleting the rear seating, so no worries of those passengers bouncing off tubes. Full harness restraints in the front seats should limit free movement of front seat occupants, in the event of a mishap. Cage on top of through-the-floor subframe connectors should add some rigidity? Plans may change, but if I try to be objective & realistic, I think I can get what I need.


Re: Chassis stiffening for street car

Posted: Sat Jul 21, 2018 8:44 am
by mk e
I saw a build on....bitchin rides? Where they put the cage behind the a-pillar trim and up under the head liner....if you didn't know it was there you'd probably miss it. They were after looks but I think safety wise it made a lot of sense....a classic "doing the right thing for the wrong reason"

Re: Chassis stiffening for street car

Posted: Mon Sep 24, 2018 1:47 pm
by BobbyB
Hi Matt,

I just now saw your question about your steering box. I think what you are feeling is actually where the rebuilder has removed all of the gear backlash in the center of the travel, which is normal.

Is your falcon a driver yet?

Re: Chassis stiffening for street car

Posted: Tue Sep 25, 2018 4:09 pm
by bigblockmopar
Nice topic, although the amount of pics here are a bit lacking I think :wink:

I'm dealing with a similar situation, which is looking to improve/maintain rigidity in my daily driven '73 Dodge Dart.

Some years ago I installed subframe connectors on the car, which got rid of some rattles and made the ride more quiet overall.
Suspension-wise the car is still fairly stock, apart from increased springrate (thicker 1" torsionbars, was 0.87") on the front and rear (added leaf in springpacks), beefy swaybar and adjustable shocks all around. Poly-uretane bushings about everywhere except for the UCA's. 17" wheels.

The roads the car sees every day are 'littered' with speedbumps, roundabouts and coble stones, so the suspension gets quite a workout.

Lately I've been busy repairing some rust-issues on the car and I noticed a few locations, and in the area where the floorboard is seemwelded to the firewall, was starting to tear on the pass.side.
After rewelding and reinforcing the area again with fresh metal, it was noticable the car had become a bit less 'noisy' again.

I plan to add chassis/frame reinforcements along the way as time allows. Maintain the car's daily driver status is more important, and that also means fighting sheetmetal rust-issues on an almost 3-4 yearly basis.

Pic of the daily 'chore';