Chassis and suspension set-up and tuning

I don't recall that anyone on this forum has posted that they have tuned the chassis and supension of their SPF GT40 to race-level performance and exactly how they did it, or who did it. (At least in the couple of years that I've been on the forum. Anybody please correct me if I'm wrong --- and refer me to the posting.)

Be that as it may, and this may be a bit off topic, but there is an article entitled, "Chassis Tuning, Part 1" by a guy tuning the chassis and suspenion of his RCR GT40 Mark I to track-level performance in the current issue of Kit Car magazine. (I rarely pick up a magazine on kit cars, but did recently.) I know that this is a different car, but the article gives you an excellent idea in what's involved in getting a race car to handling performance way, way above what is adequate for the street. The article goes into engineering-level discussions of suspension geometrics, springs rates, formulas, etc. and the theory of chassis design and tuning way more than you probably care to know, but does provide a good indication of the knowledge, equipment and instrumentation involved to bring a car up to, allegedly, racing-level handling.


(Whether I get a SPF GT40 or not is contingent on being able to have the car's handling performance tuned to track-level, and I am unawares of any constructors of the car that have the knowledge and equipment to do such. (Some can't put the car together well enough to get the new owner home.) Dennis Olthoff may be an exception, but nobody has reported so. The video clips of him tracking his car at a couple of tracks linked to from this forum a few months ago don't indicate that his own item is tuned to anywhere near race-performance handling.)

Alan, are you referring to the current-edition Kit Car Magazine article by Dean Lampe and his RCR40? If so, that article has recently been discussed on this forum - do a search for "bump steer" as that is the subject of the article.

As you probably know, adjustment for bump steer is just one of many tuning adjustments for a race-level chassis. That article doesn't go into detail on the full range of considerations such as camber and castor, spring and damping rates, CG, tire/wheels, etc. as doing so would undoubtedly take several hundred pages at least!

Good luck with pulling together the tuning data for an SPF. I'm sure there are many here that would love to not have to reinvent the wheel so when you do have the data then let it be known!

Cliffbeer2 said:

Alan, are you referring to the current-edition Kit Car Magazine article by Dean Lampe and his RCR40? If so, that article has recently been discussed on this forum - do a search for "bump steer" as that is the subject of the article.

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Yes, that sounds like the article. I didn't purchase the issue, but just skimmed it. Just wanted to get a conversation going on the subject as per the SPF GT40, if possible.

Cliffbeer2 said:

As you probably know, adjustment for bump steer is just one of many tuning adjustments for a race-level chassis. That article doesn't go into detail on the full range of considerations such as camber and castor, spring and damping rates, CG, tire/wheels, etc. as doing so would undoubtedly take several hundred pages at least!

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I know. The article was, "Chassis Tuning, Part 1". Hopefully, subsequent articles will go into the other chassis/suspension tuning parameters.

Cliffbeer2 said:

Good luck with pulling together the tuning data for an SPF. I'm sure there are many here that would love to not have to reinvent the wheel so when you do have the data then let it be known!

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Thanks. I wish I had the information; that's why I haunt this forum. I have no desire to go to the time, money and hassle to "pioneer" the issue, what with just getting a driveable, half-way dependable item delivered from the dealer seeming to be a major problem in many cases. Unfortunately, the ready answers, if they exist at all, are probably buried in Ford's or Shelby American's filed or warehoused archives. More's the pity . . . . . .

When I got my car on the road I took it up to 100 mph and it was wondering BAD so I called a good friend who suggested some simple measurements and some simple tools to check the suspension out. Most of the painted red marks mean nothing! They just look good. He suggested 1/8 to 1/4 toe in on the front 0 toe on the back. I then pulled up some figures that Lynn had and went to work. I took a digital inclinometer and checked the camber first (because this changes toe a bunch) adjusted the front to -.75 degree camber and the rear -1 degree camber. Then I took an old aluminum level and cut to the size that would fit on the aluminum rim without touching the tire, then measured the diameter of the tire and cut some smaller pieces of aluminum to tape to the level, I taped the smaller metal to the level so they were at the same distance as the tread. I then strapped to the center of the wheel and leveled them both on the front right and left. Using two tape measures, one on the front and the other on the rear of the tires and using a plumb-bomb to take the measurements I adjusted the front toe with the steering wheel straight. I put the same set up on the rear and found the left rear was toed in .5 inch and the right was straight! I adjusted the rear toe to 0 degrees and then using a laser level (taped to the cut aluminum level) pointing toward the front and measured from the front hub to the beam of light, then adjusted the toe adjustment on the left and right (rear) to get the same distance from the center of the front hub equal left and right and checked my rear toe once again. The only thing that was not out of whack and not sure if its correct or not is the caster which was the same .66 degree on both left and right rear. Anyway at 135 it feels good. Thanks to Mike Trusty for guidance and if its wrong its his fault. Ha! Also this was just to get the car feeling good on the road, I understand that you should put your weight in the drivers seat and unladen the suspension to do a perfect job with correct figures but its a start in the right direction.

the SPF cars should be able to be tuned for track use without problem, independant of who puts the car together. I would assume all cars would come with a basic set up so you can take it to a qualified person to set it up for your needs. keep in mind that a race setup is likely to be very different than a street set up. The suspension on the SPF cars is very good. My car has been up to 130 at Road Atlanta with no problem. Now I cannot help you with the correct settings but I can tell you the car will do well when it is set up correctly.

I wrote the article on chassis tuning. In this issue I discussed bump steer and spring selection with a lot of help from some professionals in that area. The next article is on alignment. Then we go to corner weights and swaybars. That is a general outline of a very complicated topic. After that you really need to fine tune at the track with tire temps and seat of the pants feel. That will all come in the next 4 issues. This just scapes the surface but my hope was to at least offer some basic guidelines. If I can help just send me a note. I agree with you about the lack of performance chassis information on the forum. My RCR is well documented. I would love to see the numbers from the other manufacturers. This is where fact and fiction are seperated and propaganda is left at the door.

Good luck on your search.
Dean

Dean:

We'll be watching for your research and experimentation results in subsequent issues.

Although the cars aren't the same, the methodology and procedure that you are using will probably be invaluable when it comes to doing the same thing on a SPF GT40.

Keep up the good work.

FWIW, I was chatting yesterday with a good friend of mine, Andy Prill in the UK. He is going to be driving P/1080 at Le Mans Classic in a few weeks, which is a 100% stock and original Gulf-spec car. He's been sorting the car for its owner, tuning the chassis etc.

He ran it at Silverstone a couple of weeks ago, and was within a couple of seconds of another GT40 that was running at the same time. The owner of that other car was quite impressed, because he had spent £170,000 on modifications to his car to get it to that speed (full carbon fiber body, engine lowered and moved forward, massive weight reduction program, and who knows what else), while Andy had spent about £1000 and just done some basic spannering. The 250 kilo weight differential alone might have explained the lap time difference.

That goes to show that with a chassis featuring this level of adjustability, there is a lot to be gained by adjusting it properly. The downside is that there is plenty of opportunity to screw things up too!

Given that the SPF chassis is nominally identical to the real thing, you should have the same opportunities to excel (and similar opportunities to turn your car into a complete fright pig!) :laugh:

I'm getting in on this thread a little late, but there's something all the SPF owners should check. Mike Trusty noticed it on his car and told me to check mine.... and it is the same.

The front sway bar is loose. What I mean by this is that the arms that are on the end of the bar are splined. And no matter how tight you make the little bolt that is supposed to clamp them on, the bar will still rotate inside the arms. One side or another. Mine is stripped on the right side.

Jack the front of the car up, take just one of the arms off by removing the large bolt that attaches it to the suspension. Then put an adjustable wrench on the arm to give yourself some leverage and move the arm up and down.

You'll hate what you see....

The splines don't seem to be large enough to take the torque of the arm moving when the car is being driven. So they strip out and the sway bar is effectively useless.

Just thought you'd like to know. No, I don't know what to do about it yet... I'm calling Olthoff today.

Kirby

Alan in Nevada said:

I don't recall that anyone on this forum has posted that they have tuned the chassis and supension of their SPF GT40 to race-level performance and exactly how they did it, or who did it. (At least in the couple of years that I've been on the forum. Anybody please correct me if I'm wrong --- and refer me to the posting.)

Be that as it may, and this may be a bit off topic, but there is an article entitled, "Chassis Tuning, Part 1" by a guy tuning the chassis and suspenion of his RCR GT40 Mark I to track-level performance in the current issue of Kit Car magazine. (I rarely pick up a magazine on kit cars, but did recently.) I know that this is a different car, but the article gives you an excellent idea in what's involved in getting a race car to handling performance way, way above what is adequate for the street. The article goes into engineering-level discussions of suspension geometrics, springs rates, formulas, etc. and the theory of chassis design and tuning way more than you probably care to know, but does provide a good indication of the knowledge, equipment and instrumentation involved to bring a car up to, allegedly, racing-level handling.


(Whether I get a SPF GT40 or not is contingent on being able to have the car's handling performance tuned to track-level, and I am unawares of any constructors of the car that have the knowledge and equipment to do such. (Some can't put the car together well enough to get the new owner home.) Dennis Olthoff may be an exception, but nobody has reported so. The video clips of him tracking his car at a couple of tracks linked to from this forum a few months ago don't indicate that his own item is tuned to anywhere near race-performance handling.)

Click to expand...

I'm getting in on this thread a little late, but there's something all the SPF owners should check. Mike Trusty noticed it on his car and told me to check mine.... and it is the same.

The front sway bar is loose. What I mean by this is that the arms that are on the end of the bar are splined. And no matter how tight you make the little bolt that is supposed to clamp them on, the bar will still rotate inside the arms. One side or another. Mine is stripped on the right side.

Jack the front of the car up, take just one of the arms off by removing the large bolt that attaches it to the suspension. Then put an adjustable wrench on the arm to give yourself some leverage and move the arm up and down.

You'll hate what you see....

The splines don't seem to be large enough to take the torque of the arm moving when the car is being driven. So they strip out and the sway bar is effectively useless.

Just thought you'd like to know. No, I don't know what to do about it yet... I'm calling Olthoff today.

Kirby

Alan in Nevada said:

I don't recall that anyone on this forum has posted that they have tuned the chassis and supension of their SPF GT40 to race-level performance and exactly how they did it, or who did it. (At least in the couple of years that I've been on the forum. Anybody please correct me if I'm wrong --- and refer me to the posting.)

Be that as it may, and this may be a bit off topic, but there is an article entitled, "Chassis Tuning, Part 1" by a guy tuning the chassis and suspenion of his RCR GT40 Mark I to track-level performance in the current issue of Kit Car magazine. (I rarely pick up a magazine on kit cars, but did recently.) I know that this is a different car, but the article gives you an excellent idea in what's involved in getting a race car to handling performance way, way above what is adequate for the street. The article goes into engineering-level discussions of suspension geometrics, springs rates, formulas, etc. and the theory of chassis design and tuning way more than you probably care to know, but does provide a good indication of the knowledge, equipment and instrumentation involved to bring a car up to, allegedly, racing-level handling.


(Whether I get a SPF GT40 or not is contingent on being able to have the car's handling performance tuned to track-level, and I am unawares of any constructors of the car that have the knowledge and equipment to do such. (Some can't put the car together well enough to get the new owner home.) Dennis Olthoff may be an exception, but nobody has reported so. The video clips of him tracking his car at a couple of tracks linked to from this forum a few months ago don't indicate that his own item is tuned to anywhere near race-performance handling.)

Click to expand...

I put mine on the lift last week because the arms on my Daytona were loose so I wanted to check the 40. They were not stripped on the Daytona and after they were tightened they were fine. The GT40 arms were ok, no problems

Hello

I am not using my car racing profesionally, but attend to a few track days during the season. My car is an SPF MKII with the Roush 427SR and a ZF gearbox (one of the pre-production cars, I think number 3 to be prodused). I have set my car up with the factory suggested geometry, made the shocks a little bit stiffer all over, and put a set of Goodyear slicks on it. Thats it.

I have just returned from a track event i Poznan, Poland with a lot of supercars attending. The list includes Porche Carerra GT, Porche 997 Turbo/GT2/GT3, Ferrari 430 Challenge, Dodge Vipers, Corvette Z06, Lamborghini Murcielago/Gallardo and so on. The GT-40 had the best time around the track, and none of theese cars was able to take out the "oldie" with 60`s technology. With the same setting as on the track, but with 17" wheels and modern street tires we drowe the car at speeds up to 291 km/h on the autobahn through Germany on the way home.

Of course, there is a lot you can do to make the car perfect. But, as mentioned in this thread earlier, I think you often get out in the other end with a lot of time and money spendt without achiving a lot.

Just relax, accept the noise, the heat and the fact that both water and dust will enter the car AND ENJOY IT. I think the SPF is a fantastic car, with the correct "aura" of autenthisity over it. I have expirienced almost every one of the problems/defaults mentioned on the forum regarding the car, but everything is possible to fix without too much hassel.

Here is a couple of youtube-clips from the event: (a little accident in one of them)
YouTube - Ford GT40
YouTube - Ford GT40

Regards
Trond

The front sway bar on all spf GT40 cars is a problem because the bar itself has a relief cut into the splines approx 1/4" accross for the entire circumference to clear the pinch bolt in the arm. The problem is that there is less than 1/8" spline contact on either side of the arm because of the relief. Both of my cars had almost immediate failure. Because the sway bar drops out of the tub from the bottom, I welded the arms in possition, shortened the links and reinstalled again with no problems. You must split the urethan bushings with a razor knife and move them to the center of the sway bar before welding, also don't don't forget to load all the mounting hardware before welding. If this problem hasn't happened yet, it will. If you disconnect the links and move the arms in opposite directions you will see what we mean. P/2080 & P/2242

I have 4500 miles on mine and they remain solid

Rick,

A few questions:

How were you able to weld as a unit assembly and mount as the frame flanges interfer with the triangular mounting brackets if the assembly is mounted assembled (at least on my car)? Did you cut/mod the frame flanges to allow the flanges to not interfer with the mounting brackets as the assembly is raised into position for bolting?

Assume you welded the arm to the bar relief (bit of bar protruding past the arm)?

Any pics?

Steve P2125

ps: I have my assembly out of the car now deciding how to improve.

I have a short and long term solution to the poor front sway bar situation.

You will note that getting the sway bar off of the car is somewhat of a hassel due to removing the bolts that hold the sway bar mounting brackets. Plus once the ends have been welded in place there is no way to replace the bushings and the mounts are now a non-removable part of the assembly.

I took a chance and ordered the "original" style split front sway bar mounts from Cushman assuming that the SPF car really is a duplicate of the original. Well, to my joy, at least in this department they are exactly the same.

With the original "split" two piece mounts they can be bolted in place and the bar can be removed easily.

The metal sleeve bushing that comes with Cushmans "original" bracket fits the SPF furnished bar exactly.

Now you simply weld the arms on the bar and then clamp it into place.

It also gives me the time to work on a proper bar with adjustable ends that can be later bolted into place in a matter of minutes rather than having to dismantle the car to get the brackets off.

For the hard core, I plan on coming up with an adjustable blade type assembly with the option of remote on the fly adjustment.

I really want to thank Jay Cushman for his efforts to reproduce "original" parts which just might help the SPF owners in the future.

steve c said:

Rick,

A few questions:

How were you able to weld as a unit assembly and mount as the frame flanges interfer with the triangular mounting brackets if the assembly is mounted assembled (at least on my car)? Did you cut/mod the frame flanges to allow the flanges to not interfer with the mounting brackets as the assembly is raised into position for bolting?

Assume you welded the arm to the bar relief (bit of bar protruding past the arm)?

Any pics?

Steve P2125

ps: I have my assembly out of the car now deciding how to improve.

Click to expand...

Steve,
If you slightly chamfer both sides of the sway bar arm, you can cleanly tig weld the arm to the bar(both sides). Leave the bar slightly proud to the arm. Remove any plating from the spline area of the bar with a wire wheel before welding. Once the arms are welded into place, move the floating spacers, chassis mounts and bushings into place all the way to inside of the arms. You can now wiggle the bar assembly into place and reinstall the mounting bolts. After you have remounted the sway bar, you can center it and lock down the floating spacers with the set screws and you are done. Remember to shorten the links while yo have the assembly apart. Good luck, Rick

Rick/Mike,

Thanks for details.

I'm in process of repair based on your inputs.

Steve

Sorry I'm a bit late to this party but this is what I found on my car. With one side of the sway bar disconnected I found when I put pressure on the free end there was some movement between the splines of the arm and the bar.

When I took the arms off I found that when they painted the arms they also painted the inside of the splines. The silver paint is very thick and soft. I went in with a scribe and cleaned every grove. After reassembly the “squishiness” disappeared. I also put in a 1/8” roll pin. Time will tell if this a good fix or not but as I don’t have a TIG welder I had to make do.

One nice thing is I can take it apart later if I need to. Mike was right, I tired taking the sway bar off and found the nuts for the two bolts are on the inside of the car in the foot box, what a pain, they should have welded them in but maybe that's the way they were back in the day. I didn't say that back in the day they didn't have their own set of issues.

If anyone is interested I drilled the arms in a drill press off the car then finished by drilling the sway bar in place using the arms as the drill guide. I found 1/8" roll pins a Lowes that were just the right length.

Herman said:

If you really want the best available suspension setup on the market by now: we offer custom developed and build coilover sets for different kind of sportscars.

To adjust and finetune your GT40 suspension you can buy our Wilbers Multi adjustable reconstructed coilovers, track tested on the famous Nurburgring in Germany, and custom build in Germany.
These sets have redisigned springrates, are Hi- and Low speed compression adjustable and also rebound adjustable.
Basic versions with only rebound adjustment are also available.
We have the option to adjust the spring pre-load hydraulically, ideal for quick corner weight adjustment.
There is also a 2 year warranty on these shocks.

Wilbers is a motorcycle suspension developer/builder and using this technique in your car gives a huge improvement in driveability and sensitivity, you getting a way better feeling and handling from your car.

I am prepared to setup a group buy with a nice discount, and I throw in the book: "Motorcycle Suspension Technology in Detail" written by Mr. Wilbers and Werner Koch.

We have several sets in stock in our warehouse in Edgewater FL and we offer install in our workshop in Edgewater FL.
Also sets in stock for: Cobra, Coupe, Ferrari, Lamborghini, FF GTM etc.

For more info: HermanUSA .com or 1-386-690-4239

Herman

Click to expand...

roughly arent these around 4500 per set?