Steering, Suspension, & Brakes

I would think if there is flex, it would show up in the inner fenders - but would be hard to detect - they already have some ripples built-in. The other spot may be where the rails connect up underneath or the rails themselves. I suspect it takes more torque and traction than most of us have to be a big issue unless we've done something that left things a little too flexy in the front.

You'll spot it first as stress cracks showing up in various places, particularly at any stress riser, for instance at the intersection of the inner fender with the firewall or the pyramid section up high and possibly along the frame rails. Also the stock motor mounts are prone to cracking. Also around any cutout in the fenderwell.

Jim

This may take the discussion down a different path... but hey, I'd have never anticipated where this thread has gone anyway... So, consider bracing under the motor instead of across the top like the strut tower braces discussed above. I've been thinking about radiator protection... and having a front jacking point that's a bit higher than the bottom of my suspension cross member... and reading this thread off & on... so what do you think about the idea of using 1x3 rectangular tube to drop down from the frame rails & go under the radiator. Seems like it'd provide the same sort of bracing as the "over the motor" type (can't call it a strut tower brace so not sure what to call it) & address both of my other goals. I'm thinking 1x3x1/8" wall but that may be heavier than needed. Thoughts on the idea & if it's a good one, how thick would the 1x3 need to be to support the weight when jacking up the front? Assume it'd drop down from the frame rails & be pie cut to make curved 90* bends then welded back up.

Good or bad idea? Too much weight too far up front?

Good or bad? The devil is in the details. A well anchored round tube about 2" dia. welded between the frame rails in a way that won't allow any twist whatsoever would do wonders for the rigidity of the front monocoque but that's impractical and doesn't guard the radiator from ground attacks. OTOH, my radiator guard is pretty rigid, light weight for it's size, and also acts as the center section for the spoiler, meaning if I bump a curb there's no harm done and it's strong enough for a jacking point. It also has the attachment points for the bonnet tilt assembly. It is constructed of large dimension thinwall tubing, mostly square and rectangular, with a round forward lip and a detachable top panel, and another panel under the radiator between tubular members. It is quite rigid and is welded into the bumper support brackets.





Jim

Assume I do what I noted above -- how thick would it need to be to a) support the weight for jacking & b) help minimize any twist. e.g. would 1/6" wall work? or would i need 1/8"?

Seems like i should have thought of this earlier, but maybe I should forget that idea & do something that does this but also ties into the lower lip of the front valance to help protect it too? E.g., kill 3 birds with one stone...

Rob

I think I have some more photos.









This is way stronger than it needs to be, and considerably stronger than the metal it attaches to. However, it isn't at all heavy. Doing it again, I would use 1/16 and 3/32 wall materials and use less massive rectangular tubing at the sides. I've banged it on the ground really hard with no ill effects. I'd also use heavier wall tube at the front. I've ground it over curbs, bumped metal posts, all kinds of stuff and I did put a dent in it but that's it.

Jim

Good info, thanks Jim. I think I'm going to do something similar -- probably tie it into welded brackets on the frame rails, but address adding some rigidity behind the valance, a jacking point, and minimize twist. I'll have to go by the local MetalSupermarket & see what they have & go from there. Will post pics when i get it done -- may not be this weekend though -- not sure if i can get by there before they close today & not open on weekends. Wish i could find a metal mart that was open on Saturdays

This is slightly off topic to the way this thread is heading. For those of us who are sticking with the stock cross member, I’m wondering if a noticeable improvement can be made to the rigidity of the front of the car by replacing the rubber pads between the front cross member and the frame with something stiffer like polyurethane pads or steel spacers? I heard Ted Lathrop discuss them at the last v8 meet and he seemed puzzled/disgusted that the manufacturer would use this approach.

Thanks

Scott

I think a nylon pad would be perfectly acceptable. The old rubber ones squish down over time and the suspension has isolators anyway. In fact you could probably mount it without any pads at all but it'd probably be a good idea to have some sort of bushings to prevent lateral movement. I really can't see a problem with rigid mounting and doubt the cushions do much anyway, except for one thing. I have seen stress cracks develop around the mounting bolt tubes in the unibody.

Jim

Make sure you catch this point from Jim... but it'd probably be a good idea to have some sort of bushings to prevent lateral movement. The holes in the stock cross member are larger diameter thant the mounting bolt tubes in the front rails. On the stock rubber pads there's a lip around the holes on the bottom that protrudes into the holes on the cross member to keep it lined up. If you direct mount like Ted recommends or use poly pads, you'd want to use some sort of bushing to achieve that same purpose. I'm guessing the difference was to allow for minor manufacturing variances in placement of the holes in the frame rails vs. the ones in the cross member.

On Ted's IFS, the holes are 1/2"; equal to the holes in the frame rails. I couldn't get more than 2 of the 4 holes alignedt without reaming the holes out about 1/32" each.

New to your forum,

I have a Cobra replica (remember this WAS based on an AC Ace and it does have a V8) :-).
Anyway, my car uses an MGB front suspension and for quite awhile I've bee lookiong into upgrading it. I looked at Must.II and found that I could get a custom Fatman Ind. hub to hub for about $2300 USD. I contacted FastCars and their unit is $3200. I contacted John Hoyle and found that the "frt.suspension kit" is about $1025 USD.
I then looked into the ROI (return on investment) and found what some have mentioned in this thread; 1) Mustang II would take considerably more work than the ROI would support (basically other options are equal of better than going this route). FastCars is a nice setup and would provide better steering than stock (so I've been told), but the Hoyle setup seems to make the most sense. Engineering wise its a sound design, cost wise it's the lowest cost option. Installation is pretty straightforward with a small amount of cutting and welding of the spring perches for clearance of the coil-overs. I'm running a BB-Ford 500+ HP and engine weighing 690lbs.49/52 CRG to the rear. With my current 275/50/15 front tires my steering is less than desirable so I'll be going to narrower tires which will in-turn improve "steerability".

On your discussion regarding frame "twist", you may want to take a look at what ERA (Cobra replica manufacturers) have done regarding frame design. [erareplicas.com] you might be able to adapt some of their techniques in strengthening your conversions.

One last thing if anyone is interested Hoyle has offered a 15% discount on a group buy of 3 kits I am buying soon so that would mean just 2 more to get this break.Let me know if anyone is interested.

Good Luck, good info here THANKS,
Mike