Preston's 1967 Mustang

[preston]

Suspension design is one of the main things that got me into building my own cars. When I started on my latest design the C5 stuff was fairly new. I agonized a long time between using C5 and the circle track race equipment. At the time there was a lot of complaining on the vette racers forums about spindle flex, pad knockback, and bearings wearing out. THis was before the upgraded SKF and ZR1 bearings were available. I had visions of a super car that could be run on banked race tracks and I'd had pad knockback before and it sucked. Plus I wanted the design freedom to put my pickups and such wherever I wanted and create longer controls and such. I could already see a future where the majority of hot rods would be using the vette stuff too and I wanted something different. Nowadays I'm a litle more inspired by pro-touring and hot rods, at the time I was much more inspired by true racing cars so that also aided my decision. PIctures like this made it more stark - just compare the C5 hub to a real aluminum racing hub (slightly different than the one I used).



The downsides were
1) Big hub means big wheel offset to get a good scrub radius, which means I am limited on my wheel choices and have no recourse to buy/sell used wheels.
2) no parts compatibily, all the brakes and steering are custom
3) the biggest downside is weight, a C5 hub is ~8.5 lbs, but the spindle and brake bracket are only 6 lbs with UBJ. My hub is ~6 lbs, but my upright and brake bracket is 13.5 lbs for a 25% increase in weight.

However, it also looks way more hardcore and of course quite different from another me-too vette front end. Also my LCA's are about 1" longer (always good) and my spindle pin is very high, ie my CA mounts are very low allowing me to retain a very low RC without compromising other geometry. I also can use mammoth brakes as I have no issue with wheel clearance, and I use a direct mount hat which is stronger with less deflection than an offset hat. My crappy photography doesn't do it justice but the latest package looks truly awesome when you pull the wheel off. For some reason I don't have that picture.

The first upright you see in the photos is a Coleman modular asphalt spindle with custom dimensions. It is the same basic spindle used on the Agent47 front end and the Schwartz chassis. As you can see I added some further boxing and pin reinforcement at the expense of 1 lb.

Some of things I was striving for in my design were low scrub, low scrub radius, mild camber gain under bump and aggressive caster gain for extra camber gain in turns. In the end I actually copied the layout of the C5 pretty closely (I had a geometry file for the vette). The difference is my design ended up with less RC movement and less scrub and less bumpsteer, with longer IC's and slightly lower RC, while maintaing similar figures for trail, caster gain, and camber gain.
I wanted a high performance suspension, but I also wanted something that felt very stable going down the freeway, my sports cars have always felt darty to me with their big tires. I also tried to set the coilover as upright as possible for maxium motion ratio. Note also the high mounted swaybar, based on the standard circle track splined hollow bar and bendable aluminum arms.

I am running a 450 lb spring and I think it works out to about a 275 lb/in wheel rate. Pretty stiff on the street but then again my daily is a '92 Cadillac.





One regret was not setting the UCA up with a shim style alignment system. THe adjustable length UCA is actually pretty easy to setup and adjust, but not as easy, fast as a shim setup, plus with a shim setup you can instantly go back to previous settings.

The bushings are Currie "JOnny joints' which are basically an articulating polyurethane rode end. They are hard to keep greased and honestly the NVH level doesn't feel that different from when I used QA1 teflon rod ends. And they definitely have more stiction, so that's some thing I might change abck to using rod ends at some point. All of the coilovers also have a poly bushing at one end. I'll be honest though, the NVH in this car is pretty high, despite all my efforts I cannot really say it feels as streetable as I would like.

My street wheel is a 18*10.5" with 9" backspacing and my track wheel is a 18*12 with 9.375" backspacing. In the rear I use 18*13 wheels for both street and track.

Just last year I built my own uprights out of box steel re-using the Coleman aluminum steering arm/BJ mount. My overall design saved about 2lbs from the modified coleman. You can see the new spindle being built below, although I really didn't take enough pictures. Note the double shear mounting bracket for the caliper adapter, with enough room to shim it side to side to make up for welding distortion and tolerances. That system worked pretty well. With machining and fastidiousness you could probably shave another lb out of the whole design, but by the time you are done with everything its like "eh".

These are the original modified and gussetted Coleman spindles based on a Grand National pin.



Here are some of the parts of the one I built















Note the custom built trigger wheel from eMachineShop that will eventually be connected to a Racelogic traction control system.





You also may note the change in steering rack- I originally had a circle track rack that I had modified to support my wide track that never worked well. My suggestion is if you need any kind of custom steering - go directly to Woodward. This would have saved me a lot of headaches if I had done that originally. This new rack works great, and looks very pretty as well, and was setup with custom width for me. Tony Woodward got the assist just right on the first try too based on my input.

here are some pictures of the rack






The new uprights helped support an eBay purchase I made of some SERIOUS PFC Endurance racing calipers. These things retail in the Hoerr catalog for $3k apiece. Needless to say I paid no where near that. THey were a lightly used spares package from a Ferrari challenge team that was based in England. NIckel plated mono-block goodness !! Only downside is pads are hard to get, very expensive, and since they are race pads my wheels are permanently dusty. But man do they look cool LOL. I have not even had them on track yet. Remember how I mentioned lots of brake clearance ? I am using a 15" rotor in a 18" wheel with a ~8+" wide caliper that uses 1.25" thick brake pads. Makes all the Baer/Wilwood/Stoptech street based stuff look pretty wimpy (and looks are what we care bout on lateral-g right ?)

The hat is direct mount and uses Brembo floating hardware with anti-rattle clips (as developed for the McLaren F1 !). THe rotors are custom made from Coleman.



I'll have to look on the camera for some other photos, I can't believe I don't have a photo of the mounted caliper on the 15" rotor. The rears are 14" Coleman rotors with the same floating hardware. I am using a racing style dual M/C system driven by a hydraboost. I built the custom adapter to do this i'll show that some other time.


The shocks are nothing to be proud of however, some rebuilt obsolete Bilsteins in the back and some AFCO adjustabl circle track shocks up front. Someday I would like to upgrade those pieces, but I really don't feel like my driving is sophisticated enough to pursue that right now. Mostly I think they could be a little softer for street driving.

Anyway I hope you enjoyed the photos and seeing a suspension design that is quite a bit different from an upgraded '60's era GM or another plain jane vette front end.

[preston]

The rear suspension is an 3 link with an underslung watts. I love the lightweight and simplicity of this watts, no giant cantilevered brackets hanging off the rear housing. However it is not adjustable, I use the rear sway bar and springs to tune. A low rear RC is highly recommended by Mark Ortiz and other live axle racers, and this is about as low as you can go. I just reinforced and gusseted the housing and pierced it with some threaded rod, also gusseted inside the housing, then added a double shear bracket out of .125 steel. I forget the name of the guy who made my "football" it was kind of a one off deal. In the photo a few things are mismatched, that is a very old photo that was still using mockup pieces.







Oh here I did find the rear caliper mounted, not a good photo as the light doesn't really catch it and you can't really tell how large that caliper really is, plus my older equipment is kind of dirty not like the real sexy build photos of all new parts we're used to seeing here.




Note that the link and swaybar and caliper brackets are all bolt on not weldon. I use anti-rotation bolts and I've never had a problem. Heckuva a lot easier than welding them.



The links for the 3 link are 29" long, and use Howe rubber bushings up front.

It is a full floater of course, but without some of the fancy hubs and hardware that have been showing upfor PT cars in the last year. But again, big beefy circle track hubs and direct mount hat with floating 14" rotors. Aluminum 3rd member case (10 lbs lighter). Trutrac diff with 3.08 gears, 31 spline axles.

I think my Anti-squat percentage is only about 50%, but I'm still not convinced you want greater than that or not for road racing. Never had a problem with brake hop !

I am running 250 lb springs for a wheel rate of about 275 lbs with a 1.1 motion ratio.

[Flash68]

I was just wondering the other day if there were any updates forthcoming here.

Would love to see a pic of those ridiculous calipers on rotors swallowed up by the 18" wheels... what wheels you running BTW?

I seem to be struggling with the opposite of you... starting with pro touring and getting more and more influenced by race cars lately.

Keep posting!

[Ron in SoCal]

You're an animal Preston. Do me a favor and post updates a little more often?

[Payton King]

the time to continue your build thread here. Lots of good stuff!

[WSSix]

Yeah Preston, you're a bada$$. Seriously wicked stuff you're putting together. Good job.

[preston]

I thought I would post today about my fuel system but I wanted to post just a few more photos of these brakes...because I'm vain. I didn't manage to get one with the wheels on though but I will tell you that right now its not impressive, the CCW wheels ahve a pretty large flange and smaller center section so you can hardly even see the calipers.



Note that is 4" ducting hose for scale



Rear brakes:

[preston]

So my fuel system - nothing too different but a few good ideas I think.

I run dual tanks in front of the rear axle. This allows for better weight distribution, packaging and perhaps safety then a rear mounted tank.

These tanks were originally built for my last chassis otherwise I would have done some things differently. In fact, redoing it today, I would probably use stock Vette twin tanks or even twin tanks off the new Mustang to get all that good OEM engineering.

Although the overall design is sound, I should have built them out of SS not aluminum, and taken the 12 lb weight penalty - For safety reasons obviously.
Even though these tanks are ensconced in the frame, and I have a 3/4" .063 tubing as well as .063 steel protecting them from the driveshaft, they still seem vulnerable to me. The chassis does protect them from major impact, but they are vulnerable to penetration. And obviously a car of this level
should have fuel cells but because of their unique layout, we are talking about $4k+ to build proper fuel cells. Come to think of it I have never really seen if ATL or Fuel Safe makes a drop in Corvette based fuel cell solution, might be something to check into.

Unlike the Vette, I call the passenger side the main tank, which means it is the most likely unit to have fuel in it. This is better for weight distribution than using the drivers as the main tank.

Each tank holds 10 gallons. They are joined in the top middle by a 2.5" crossover tube and at the bottom by a -10 hose. This lower hose may not be necessary but I'm too lazy/chicken to remove it, and it probably does help with fuel fill as it will give a false shutoff signal to the pump as it nears the top as I guess fuel cannot transfer fast enough ( you just wait a few seconds and keep filling). The crossover tube is special fuel filler hose from Coleman is 1/4" thick plastic of some kind.


As you can see I built a fuel "module" with twin in tank Bosch 044 pumps. The 2nd pump is turned on by the Megasquirt ECU under high load. The fuel sender is a standalone VDO unit as often found in
boats. It is a "capacitance" fuel meter with only one moving part and packages better than the usual float arm.

The other "trick" thing going on is that I am using a late model GM/Vette siphon pump to pull fuel from the 2nd tank into the main tank. That is where you see the outputs of the two pumps going to the Y and a 3rd hose is coming off of it.This hose travels through the fuel crossover tube
into the bottom of the drivers tank where I have adapter fittings that connect to the siphon pump, and then returns fuel to the main reservoir in the passenger tank.

The main tank has a half height vertical barrier with a one-way door in the bottom of it, the pumps sit behind that. The fuel return comes into the main tank as well as the return from the siphon pump obviously. Combined with the vertical design of the tanks, I seem to get good fuel supply under all conditions.

All hoses are teflon lined style or OEM in tank fuel hoses, and power for the pumps comes straigh from the battery via trunk mounted relays.

I started out with the little Walbro 155's that a lot of people used, and they were totally in adequate. I bought them from APE so I didn't think they would be counterfeits, but they could not supply enough fuel for even 600rwhp. When I opened up the tank to run some tests, I could actually see them spitting fuel out of the top of their canisters
so they were obviously defective, both of them. I woudl say stay away from these pumps, the 044's are so much stronger and better if you can fit them.

When I found the problems with the pumps on the dyno I spent quite a bit of time testing the flow (dangerously) through the hoses timing how long it took to fill a bucket. With an open -4 spigot obviously I couldn't get the pressure very high but it was still easily measurable that the free flow of the two pump systems was night and day.

The piece of aluminum angle that the pumps are sitting on is welded to the fuel lid, and was the very first aluminum TIG welding I ever did for real. So far so good it has held up.

-8 braided SS/teflong lines to the front and back. One experiment I would like to tryin the future is moving the fuel regulator back
to the tanks and running a deadhead line up to the engine. I haven't had any problems but this would really reduce fuel heating. I know others with big pumps have had issues in extended driving with
fuel heating. But I guess I rarely drive it for hours on end on hot days here in Washington.

If you go back above and look at the photos of the rear suspension, you can clearly see the tanks nestled into the frame in front of the axle.
They were in fact the very first things installed in the brand new painted chassis and I don't want to have any problems because they
are a pain to get in and out ! They do not drop out becaue there is 16awg steel shelves that hold and protect them.

Oh, and I use a standard race car rollover vent to a -8 teflon hose that manages to go up and a few inches higher than I ever fill up the fill tube and then does a loop before exiting into the rear axle area where I cover the end with a piece of pantyhose for a filter......Hmm, maybe I could manage to at least put a K&N on there.

Oh, almost forgot - the tanks are also stuffed with fuel cell foam to reduce slosh and dampen the chances for an explosion.

[GregWeld]

I gotta say it ---- I like the do it yourself attitude -- I like the engineering...

The welding -- not so much.

Before you go out and start stressing stuff -- I'd have those spindle additions ground out and welded by a professional.


I'm not trying to be critical -- But I'd like you to be safe, for yourself, as well as others that share a track with you.

[INTMD8]

Wow, crazy amount of fab work here. Very cool build.

Good point on the cabin vents. I thought those GM door jamb vents were to release pressure when doors were closed (and windows shut) but it makes sense that it would work with outside air intake as well.

As for your worries with the fuel cells, have you considered a carbon fiber driveshaft?

And holy hell, those are the thickest brake pads I've ever seen