Help With Designing New Front Suspension for 71 Javelin Road Racer

[Bulletpruf]

Fellas -

Details on the car - 71 Javelin, 401, 4 sp, 500 flywheel hp, 9" full floater with FlexForm leaf springs, 3,300# race weight, street legal but just barely.

The problem with AMC's is that there's not a lot of aftermarket support. I can get a Pro-Touring front suspension that's Mustang II based, but it's $4,000 and not exactly what I'm looking for - http://www.freakride.com/2011_amc_suspension.pdf. Geometry is better than stock but not ideal.

I can also get some adjustable coil-overs with tubular control arms but that's not cheap, either ($1,800, I think) and it still has stock geometry.

I plan to race the car in NASA American Iron - plenty of leeway in the rules - - "All cars must have OEM front and rear shock towers in the same location as stock. AI cars must utilize the OEM rear shock towers for rear shock attachment. Attachment of camber or caster adjusting devices is unrestricted. The OEM rear shock tower must be intact and the shock mount must pass through the original hole in the tower. The tower may be modified to install shock mounts, reinforcements, or spacers but the OEM assembly must remain in place."

I'm thinking I can find something off the shelf that would fit and have good geometry or I could have something custom designed and built. This is somewhat of a budget build, so cost is a consideration. Would be nice if I could go with stock car parts - - inexpensive, rugged, easy to find replacements.

Anyone have any thoughts? Any information missing? I can take measurements if necessary.

Here's the stock suspension (former owner went a bit overboard with yellow paint)


Engine compartment


Passenger wheelwell


Stock control arms




Thanks!

Scott

[exwestracer]

I would suggest looking at the "build up" control arms available from the circle track industry. Basically a ball joint holder that you attach your own radius rods to. No reason you couldn't put a coil over mount plate where the spring pocket is now and run the shock down through the upper arm. Use heim joints for caster/camber adjustment. THis stuff is all relatively cheap. I'll try to find some links for you when I get more time, but I wouldn't be surprised if you couldn't buy it all from Speedway. Don't want to offend any site sponsors, but I doubt they have a lot for your application anyway!

I'd look at going with a wider spindle track width (longer arms), and run less wheel offset and scrub.

[Bryce]

I would start to plot out your suspension pickup points, calculate Camber Gain, RC, RC migration, ackermann, bumpsteer, etc....

Then decide where you want you want these specs to be. Then start looking at the limitation of the stock pick up points. What can be adjusted easily and what needs lots of work. I agree with Ray, build up your own control arms with circle track stuff. Thats what I did, and I am super happy with it.

[High Plains Mopars]

With the spring on the upper control arm, it has me wondering if some gen 1 mustang parts could be adapted.

[Bulletpruf]

I would suggest looking at the "build up" control arms available from the circle track industry. Basically a ball joint holder that you attach your own radius rods to. No reason you couldn't put a coil over mount plate where the spring pocket is now and run the shock down through the upper arm. Use heim joints for caster/camber adjustment. THis stuff is all relatively cheap. I'll try to find some links for you when I get more time, but I wouldn't be surprised if you couldn't buy it all from Speedway. Don't want to offend any site sponsors, but I doubt they have a lot for your application anyway!

I'd look at going with a wider spindle track width (longer arms), and run less wheel offset and scrub.

Is this what you're referring to for an LCA?

http://www.speedwaymotors.com/AFCO-L...its,40160.html

UCA here?
http://www.speedwaymotors.com/TUBULA...TEEL,2124.html

Or here?
http://www.speedwaymotors.com/Adjust...afts,2117.html

Thanks,

Scott

[Bulletpruf]

I would start to plot out your suspension pickup points, calculate Camber Gain, RC, RC migration, ackermann, bumpsteer, etc....

Then decide where you want you want these specs to be. Then start looking at the limitation of the stock pick up points. What can be adjusted easily and what needs lots of work. I agree with Ray, build up your own control arms with circle track stuff. Thats what I did, and I am super happy with it.

Bryce -

As usual, you're making my head hurt. Probably need to buy a book or check out a website in order to get smart on this. Any suggestions?

Thanks

Scott

[exwestracer]

I

http://www.speedwaymotors.com/Adjust...afts,2117.html

Thanks,

Scott

Scott,
The last one. They also make that same style larger for lower ball joints. Then you build the arms to whatever length you need. You can modify the strut rod mount to put a Heim in double shear, and that's about all it needs. I like Bryce's idea about moving the upper mount points. With 1/2" Heims in there, you could probably move them quite a bit within the stock ears.

It's not really that hard to figure all that geometry out. First decide what tire and wheel combo you are going with, and stick to it! We can take it one step at a time from there.

[Bryce]

Bryce -

As usual, you're making my head hurt. Probably need to buy a book or check out a website in order to get smart on this. Any suggestions?

Thanks

Scott

Check out chassis engineering by herb adams. This is a good starting point.

[Bryce]

Scott,
The last one. They also make that same style larger for lower ball joints. Then you build the arms to whatever length you need. You can modify the strut rod mount to put a Heim in double shear, and that's about all it needs. I like Bryce's idea about moving the upper mount points. With 1/2" Heims in there, you could probably move them quite a bit within the stock ears.

It's not really that hard to figure all that geometry out. First decide what tire and wheel combo you are going with, and stick to it! We can take it one step at a time from there.

Thanks Ray,

I would weld plates onto those stock upper control chassis mounts and cover up those holes and redrill where you want them. Let me know if you want geometry help.

If your LCAs are horizontal and you are happy with the ride height I would keep the same chassis pickup points. For budget reasons, you might want to keep stock spindle.

[Rod]

I have to watch this one, I have a similar car build coming

[Norm Peterson]

Probably need to buy a book or check out a website in order to get smart on this. Any suggestions?

Fred Puhn's "How To Make Your Car Handle".


Norm

[Bulletpruf]

Ray -

Many thanks for the info. I have a few follow up questions:

The last one. They also make that same style larger for lower ball joints. Then you build the arms to whatever length you need.
-Am I just starting out with a cross shaft and then finding the correct sized arms and ball joint mount? What about lower arms?

You can modify the strut rod mount to put a Heim in double shear, and that's about all it needs.
-Ok, assume this is something I can do after I figure out the control arms.

I like Bryce's idea about moving the upper mount points.
-Would prefer to do this in my garage and keep it uncomplicated (within reason), so I'd really like to keep the stock pickup points.

With 1/2" Heims in there, you could probably move them quite a bit within the stock ears.
-Can you elaborate a bit? Where would I be mounting 1/2" heims? Keeping the stock mounting location?

It's not really that hard to figure all that geometry out. First decide what tire and wheel combo you are going with, and stick to it!
-Wheels will be 17 x 9 and tires will be 275/40-17.

We can take it one step at a time from there.
-That works for me. What would be the next step? Figure out what size cross shaft I need? Also, what spindles would I be using here? I'd prefer to get rid of the AMC spindles; not many aftermarket brake options.

Thanks!

Scott

[Bulletpruf]

Check out chassis engineering by herb adams. This is a good starting point.

Ok, I'll get one ordered.

thanks

Scott

[Bulletpruf]

Thanks Ray,

I would weld plates onto those stock upper control chassis mounts and cover up those holes and redrill where you want them. Let me know if you want geometry help.

If your LCAs are horizontal and you are happy with the ride height I would keep the same chassis pickup points. For budget reasons, you might want to keep stock spindle.

Bryce -

Appreciate the detailed input. I have a few follow up questions/comments -

I'd prefer to keep the stock pickup points at this point.

I'd like to use coilovers; can't I change the ride height with these?

You said - "If your LCA's are horizontal and you are happy with the ride height..." I'm not sure I can figure that out now. Car is complete disassembled, but before I took it apart it had 14" wheels and complete stock suspension. I've got a buddy who has a 73 Javelin with stock front suspension and 17 x 9 wheels; do I need to check with him to see if his LCA's are horizontal?

I can afford a decent aftermarket spindle; any recommendations? Speedway has Mustang II and a few others.

Thanks!

Scott

[exwestracer]

Scott,
Your lower arms are what is referred to as "strut rod" type. LOTS of circle track arms available for those. You might even find a design that bolts right in to your lower mount.

The upper arms can be made with bent rods (adjustment is a little more difficult) and no cross shafts. All you need to do is get the heim joints square to each other and they will bolt right in your stock upper mount holes. That is where I was referring to running the 1/2" heims. They are small enough that you might fit a couple alternate mounting holes in the stock brackets, if you so choose.

To figure out the ride height, all you need is a front tire diameter. You already have the spindle and ball joint. Put the spindle back on the lower ball joint and measure from the center of the spindle pin (drill mark on the back side) to the center of the ball in the lower ball joint.

Let's say that's 4". If you run a 26" tall front tire, the center of the tire (spindle height) is 13"... - 4" to the ball joint puts the lower ball joint 9" above the ground. With the LCA "level" at ride height, then the LCA mounting hole on the crossmember would also be 9" above ground. From there you can find the height of the rocker panel, bottom of the crossmember, etc. to determine if that ride height is acceptable.

[funcars]

Coleman and Port city racing have a lot of circle track stuff too. The Javelin design looks very similiar to a mustang just with the link going forward instead of back - lots of options there that may give more ideas as well. Good luck

[javelin66]

http://www.martzchassis.net/project-gallery
this has front suspension for javelin ford

[riles]

Looks an awful lot like the suspension on my 65 mustang, especially that stamped lower arm. Check with Global West or TCP and see what they say. They may carry products for your car. Also look at Street or Track for some ideas.

[AMC Racer]

Pictures from '71 T/A Javelin. Looks like stock car type spindle mounted on boxed stock UCA & LCA, coil over, sway bar with link to UCA, cooling ducts to brakes, etc. Maybe gives some ideas? Since stock ball joints and spindle are bolts ons, could tweak geometry with spacers, spindle lowering plate, etc. if you don't want to fab all new. LCA bolts to engine crossmember which bolts to frame, so could make custom crossmember or modify stock.

Some guys use drum brake hubs with hat for rotors then make a caliper mounting bracket bolted through the spindle ... Wilwood, Aerospace & McIntire also have aluminum hubs for AMC spindle ... more pro-street than race.

'71 Trans Am Javelin: