stretched and jacked

[Buck70]

Tweeker asked how I stretched the wheelbase on my 4 link so here's a quick rundown.
The two problems were, 1. the wheelbase is an inch to short to match the fenders and 2. The FF design ride height with fenders and boards leaves
3.25" under the running boards, which is not OK for a street driven rod.

The wheelbase was fixed by ordering longer lower custom control arms, BUT that moves the chassis ends sideways due to the triangulation of the 4 links, so I used rod ends at the chassis to eliminate bind and since the R.E's are narrower than the stock eye you can use different width spacers on the bolt. I also had sway bar tabs put on the lower bars to take a stock Mustang bar. Due to FF spring/shock bracket the angle of the LCA will still be OK with the 2" of added ride height I need.
The upper Control arms are at a much sharper angle apx. 34* so stretching them moves the frame tabs much further sideways and the 2" of ride hgt change needed puts them at a very bad angle for squat control, braking, and causes forward bite issues by drastically moving the instant center.
I used rod ends there as well to reduce binding, but I also had to stretch the length and move the pivot points inboard and down to correct the angle/anti-squat values. There are some great websites to check that %
After looking at the upper link FF tabs and how much all the welding in that area had already distorted the 1/8th wall tubing I decided it was safer to replace part of the tube than cut tabs off, grind the old welds and weld new tabs to the existing heat affected zones. So I designed new longer tabs from 1/4" plate and had them plasma cut. Then I cut 11" out of each side of the frame tube where the tabs land. I welded the new tabs on the new tubes added a gusset between them and plug welded a short pipe inside the new SQ tubes ends. I cut a flap out of one face of the chassis tubes to allow the internal pipe on the new pieces to slide inside the chassis tube. That allows a bead weld inside the splice and the tab is welded back on and the tubes are welded all around the perimeter. Most people won't even notice the changes. The stretch was easy, the ride height repair not so much. You will likely have to move the top of the shocks back as well, but since I wanted to tip mine in slightly for more clearance I will be making brackets anyway.

I'll try to post a few pics when the bars are all in place again, and I find a sway bar from a 6cyl mustang.
Dale

[joejohnson50]

Great information to plan according. Thanks for sharing, looking forward to seeing the photos.

Originally Posted by Buck70

Tweeker asked how I stretched the wheelbase on my 4 link so here's a quick rundown.
The two problems were, 1. the wheelbase is an inch to short to match the fenders and 2. The FF design ride height with fenders and boards leaves
3.25" under the running boards, which is not OK for a street driven rod."...
Dale

[Arrowhead]

Did you find that you needed additional clearence for the driveshaft with the increased ride hieght? I clearenced the frame and fish mouthed the lower frame tube so the driveshaft wouldn't hit under full droop of the suspension. The roads in NY suck and can (and have) experiance the tires in the air from unexpected road conditons.

[Buck70]

Originally Posted by Arrowhead

Did you find that you needed additional clearence for the driveshaft with the increased ride hieght?

I haven't installed the driveline yet, but I do think it will need some notching at that point.
I am thinking about adding a tube and gussets under that area and I might carry that tube clear across so the open ends can act like hitch receivers for running board support steel. The front down bars on the roll cage are going to be the hardest part to design.
Did you use limit straps or were the shocks just out of stroke when you got airborne ??
Dale

[Olli]

Wow. Those are some very serious modifications. You must have some fabrication experience to do all that. You might want to add a warning to the inexperienced to not try making the changes without accepting all risks of destroying the chassis.

Seriously, it sure sounds like you did a nice job and I would love to see some pictures posted.

Olli

[Buck70]

Originally Posted by Olli

Wow. Those are some very serious modifications. You must have some fabrication experience to do all that. You might want to add a warning to the inexperienced to not try making the changes without accepting all risks of destroying the chassis.

Seriously, it sure sounds like you did a nice job and I would love to see some pictures posted.

Olli

Thanks Olli
So you don't like the leave out the warnings and let Darwin sort it out approach
FWIW
I never copy someone else's approach without thinking it through, and I hope everyone else does the same. I did detail the extra pipe I put inside the butt joints to stress how important it is NOT to just butt weld in a new piece, especially since I moved the pivot further off-center adding more stress when a moment is created during acc-decelleration. The 500 plus HP Hemi will be working the chassis hard enough already.

I would like to hear from owners with the 4 link set-up that have raised their ride height more than an inch by adjusting the coilovers. Taller tires don't count here. I want to take someone else's real world specs and run them through the anti-squat formula to show what it does to their instant center.

I need about 10 dimensions from a completed car to post the results
Any takers?
Dale

[1fastsedan]

I'm interested in your results, but right now I don't have anything assembled to help you. Sorry.

[Buck70]

Originally Posted by 1fastsedan

I'm interested in your results, but right now I don't have anything assembled to help you. Sorry.

Adam
I don't recall you having running boards?
This is really about guys that do have running boards because I think they will have to jack their ride height much higher to make them streetable.

The FF UCArms are under 10" long and when you change the ride height 2" the front pivot moves up that far. When you triangulate that out for instant center it shoots for the moon. At some point it also starts to skew the pinion angle more severly. I have mine corrected with the new tabs and when the last couple parts are in place I'll post it up.

I am curious about the front spindles, since I haven't looked at how to raise the front enough without trashing that geometry.
Dale

[1fastsedan]

Originally Posted by Buck70

Adam
I don't recall you having running boards?
This is really about guys that do have running boards because I think they will have to jack their ride height much higher to make them streetable.

The FF UCArms are under 10" long and when you change the ride height 2" the front pivot moves up that far. When you triangulate that out for instant center it shoots for the moon. At some point it also starts to skew the pinion angle more severly. I have mine corrected with the new tabs and when the last couple parts are in place I'll post it up.

I am curious about the front spindles, since I haven't looked at how to raise the front enough without trashing that geometry.
Dale

I haven't installed any of it yet, but I do have a full fender package...so I'm interested. I just sent my chassis to powder coat, so I won't be making any drastic changes, but I'm interested in adjust-ability with the control arms.

[Buck70]

Originally Posted by 1fastsedan

I haven't installed any of it yet, but I do have a full fender package...so I'm interested. I just sent my chassis to powder coat, so I won't be making any drastic changes, but I'm interested in adjust-ability with the control arms.

Have you decided on your ride height and r tire size yet?
Dale

[1fastsedan]

Originally Posted by Buck70

Have you decided on your ride height and r tire size yet?
Dale

Funny you should ask that, since my buddy who owns a wheel company just went out of business.

So now I'm looking at all options again. I can tell you that I'll be right at the max specs that F5 lists for wheels when running full fenders. Just trying to decide on 17 or 18" wheels. Ride height we'll figure out once the thing is running.

[Buck70]

Originally Posted by 1fastsedan

Funny you should ask that, since my buddy who owns a wheel company just went out of business.

So now I'm looking at all options again. I can tell you that I'll be right at the max specs that F5 lists for wheels when running full fenders. Just trying to decide on 17 or 18" wheels. Ride height we'll figure out once the thing is running.

Adam
I will use either 15 if the brakes clear or 17 if not as long as I can find lots of tire options. I'm pushing up to 27" tall looking for the best ride and hgt combo. I will be buying taller softer springs as well. I had dubbed her
"Bon Temp" but maybe it should be Geritol since it's becoming an old mans hotrod.
Dale

[Buck70]

Originally Posted by Olli

Wow. Those are some very serious modifications. You must have some fabrication experience to do all that. You might want to add a warning to the inexperienced to not try making the changes without accepting all risks of destroying the chassis.

Seriously, it sure sounds like you did a nice job and I would love to see some pictures posted.

Olli

Olli
I couldn't figure out how to embed the pics here so I posted them in the gallery. For reference you can also see one of the stubs with the old tabs still on it that I cut out sitting up high in one shot. Let me know if they look OK or I need better pics
Dale

[Buck70]

Originally Posted by Arrowhead

Did you find that you needed additional clearence for the driveshaft with the increased ride hieght? I clearenced the frame and fish mouthed the lower frame tube so the driveshaft wouldn't hit under full droop of the suspension. The roads in NY suck and can (and have) experiance the tires in the air from unexpected road conditons.

Arrowhead
Got my driveshaft in today and I don't have to C-notch the frame due to my change in ride height. This is partly due to my auto tranny being so long that the front U-joint is 3.5" behind the FF hoop. The shaft is 24" c to c on the U-joints. The other thing I did today was build a new battery shelf 2" lower than the FF location. The ride height change made extra room there and now I can run ANY 27 series battery with room to spare.
Pics of the new bigger battery tray are in the gallery http://www.ffcars.com/photopost/showfull.php?photo=8230
Dale