Tubular Control arms?

[Dominik]

Good morning!

I see the extra cost for tubular control arms is $15.000 for a Kirkham.
Can the billet control arms be replaced with the tubular ones?
Is it a straight swap or are other parts involved too?

Dominik

[1ntCobra]

I think it is a lot more complicated than just replacing the control arms.

There is a photo album on the Kirkham Motorsports facebook page called "427 Stainless Chassis". It shows a frame with the traditional suspension on one side and the billet suspension on the other side.

Here is a link to the Kirkham Motorsports "wall": Kirkham Motorsports - Local Business - Provo - Wall | Facebook

Scroll down that page and you will find the album on February 8th.

[mreid]

There are frame changes required.

[1ntCobra]

Originally Posted by mreid

There are frame changes required.

Where did you hear that? I always thought, that the billet suspension bolted directly onto the original style frame. Take a look at the pictures that I mentioned above. Do you see a difference in the frame on either side?

I think much of the cost of the Kirkham "original" style suspension is getting the girling brakes and other traditional parts that are made out of "unobtainium". The Shelby CSX?000 cars use modern brakes with their tube control arms, so the CSX cars are not as "original" as the Kirkham version of "original" suspension.

If you wanted a more traditional (but not quite original) suspension on a Kirkham, perhaps you could try sourcing the Shelby style suspension from Vegas. But who knows how much Shelby would charge you for their parts.

[1985 CCX]

I think that Nick @ Acton Custom has worked on both, drop him an email.
He fabs this stuff as well..........

[mreid]

Originally Posted by 1ntCobra

Where did you hear that? I always thought, that the billet suspension bolted directly onto the original style frame. Take a look at the pictures that I mentioned above. Do you see a difference in the frame on either side?

I'm only basing on that when I ordered my Kirkham 289 fia, I later called back and upgraded to the stainless frame. I asked Tom if that was a problem and he said no, but then added if I later wanted to change to the original style suspension it would be a problem as there are frame differences.

Now it's possible he was referring to the 289 leaf spring upper control arms. Kirkham still refers to my car as a hybrid as it is a 289 with a 427 frame, although interestingly, when you order a ss frame, the main rails are only 3.6" in diameter.

Perhaps the best bet is to call Kirkham and stop the speculation.

[Dominik]

My mate Nick knows?

Let me mail him.
I had inquiries from Germany to change to tubular arms for historic registration reasons.

[cobrakiwi]

This guy supplies most of the big names out there,
Cobraracing Racing Suspensions
Great parts, send the Kirkhams an email with your car's number they would be the best to ask. I would think you will need to change out just about every thing from the frame out to convert to the steel tube control arms, I have a Hi Tech, a Kirkham, and CSX car in the shop and they are close but all have there little differences.
I have 3 types of CSX control arms, 2 types of Hi Tech control arms and 2 sets of steel Kirkhams control arms as well as there alloy arms and I can tell you no 2 are the same.
Cheers.

[Dominik]

Thanks!

Sourcing the parts is easy, but the variations described by Cobrakiwi are scary!

If I had the car in the shop I could check, but it's a long-distance inquiry. The car is Germany, Nick makes the parts in NH, I could have them done here in South Africa too...

I wait for David to comment, or mail him directly.

I don't want to fit new control arm only to find out that they are slightly shorter/longer and won't fit to the uprights anymore!

[cobrakiwi]

Does the Hi Tech in your back yard sell there parts out side of there Shelby builds?

[mickmate]

On the 427 frame shown on the facebook page they didn't make different chassis pickup points from one side to the other. That shows tubular with Girlings one side, K billet the other. Kirkhams claim from the beginning was that their parts interchange with originals. The mounts are the same but Steve will be able to tell us if they adjusted arm lengths at all for rotor hats on the outside of the pins or anything that changes track width.
There are original tubular Metalistik bushed arms, the same thing bronze bushed for Comp cars, there are early CSX Vegas/HST style with turn buckles and heim joints for added caster adjust, there are South African HiTech arms with turn buckles and heims with straight tube triangular arms, then there are late Shelby ones with screw in Chrysler style ball joints for the billet uprights. Kirkhams have also been through a couple of revisions as they improve geometry and manufacture methods. They have added heims to tubulars, made billet ones, made billet ones with improved steering points to virtually eliminate bump steer with Morris. Other than the 289 and hybrids which is a different deal they all will mount the same.

[Dominik]

I see.

The car should essentially get custom made arms once in the shop. If I knew just a bit more I could supply "raw" arms and get my race car fabricator in Germany to finish them off, on the car.

Are the uprights the same, front and rear??

Cobrakiwi:
I have 2 sets of rear control arms, for reasons described above they are not interchangeable with original ones...
I build one last car (for now) and that's where they will work one day.
Nick can help you out. I figure you speak the same language ;-)

[Tom Kirkham]

I hope I can clear up some of the confusion.

The two billet chassis cars we have built have almost nothing in common with any other car. Other than bearings, the suspension is not interchangeable with anything else.

All of our 4 inch round tube frames (427, 289 hybrid) have the suspension points in the original 427 coil over suspension location. This means that if you have a complete suspension corner from a CSX3000, a CSX4000, a AC MKIV or a Kirkham and I also believe Hi-Tech, you can bolt the complete suspension corner into any of the other cars. Please note that I said complete suspension corner, as parts between the various manufactures are not completely interchangeable.

The 3 inch round tubular chassis also known as a 289 leaf spring has a very different, yet similar suspension. Our leaf spring suspension frames have the suspension pick up point in the same location as the original CSX2000 leaf spring cars.

Now a little history of the 427 suspension. According to my discussions with Pete Brock and others, as well as what has been published, Negstead (he also designed the GT40 suspension) designed the 427 Cobra suspension on Ford's computer. And if you look at the rear lower control arm you can see the similarity. The problem was AC had according to Peter had "rooms" full of parts and were not about to discard all of these parts. The Hurlocks had also already bought the 4 inch tubes cut to length to work on a 90 inch wheel base car. So Negstead's suspension was not going to work as designed. For example the trailing link suspension point would have ended up in the driver's hip pocket. Remington was sent over to help sort out the mess. That is why the 427 suspension uses several modified components of a 289 suspension. The 427 front lower control arm is a modified 289 front lower control arm. The only difference between the two is the 427 has two ears welded on to hold the shock. This sounds like a simple change but.... The 289 loads the suspension through the top of the upright due to the leaf spring and the 427 puts almost the entire suspension loads through the lower control arm. The problem is the lower ball joint. On a 289 Cobra the suspension ball cups (part of the ball joint) almost never wear out, and on an original 427 Cobra it is a very well known problem area.

Now many years later with 20/20 hindsight and lots of river having passed over the dam... There is a market for original style suspension cars. What to do about the problematic front lower ball joint? There is also another less known problem with the original ball joint. It is very small. The original A-arms have the ball joint housing very, very, and let me repeat, very close to the brake rotor. It is very common for original cars that are driven on the track to have a grove in the rotor where the A-arm (ball joint housing) rubs into the rotor when the car is cornering. This is caused by the front spindle flexing, allowing the rotor and the A-arm to contact each other. So what we have here is a double whammy. The rotor is too close and the ball joint is smaller than any off the shelf ball joint from a major manufacturer. If you make the ball joint bigger you have to make the lower control arm shorter. If you make the lower control arm shorter, you change the king pin inclination angle, scrub radius (which already is not great), etc., which forces other changes... And this is where the various manufacturers diverged on the front suspension.

[4pipes]

Tom, after reading your post I got a little concerned. I have 15,000 miles with some track time on Kirkham #185, what inspection technique should I use to check my ball joints and what would you expect the ball joint life to be?

[Tom Kirkham]

The 427 rear suspension has it own set of problems. For example the trailing link on the 427 has a rod end on one end and a spherical bearing mounted into a cross sleeve welded onto the other end at an angle. By making the trailing link in this manner, the rear toe adjustment is limited to one complete turn of the trailing link. The other bad thing about this arrangement is having to remove the trailing link from the frame to turn it, greatly increasing the time to do the alignment. Almost everyone has updated this piece to have rod ends on both ends.

Other issues on original style suspensions are the brake rotor are behind the hub, making changing brake rotors time consuming and messy.

Setting front caster is very time consuming and limited. This is why adjustable upper control arms are so popular.

On 427 Cobras front lower control arms sagged. Comp and SC cars had angle iron reinforcements welded on the underside.

On the rear lower control arm, the original Rose bearing is no longer commercially available. Forcing a change to a wider bearing. This is not without its own set of problems...

Front spindle flexes too much.

Setting up the rear upright bearings is very time consuming if done correctly. The distance piece needs to be cut from hardened steel and trimmed to length. Using shims to space out the bearings will not work as they will break and go through the bearings. That is why we changed out to a cartridge bearing.

Rear upper control arm rod end is prone to breaking on a street car. Comp cars used a bigger rod end.

289 roller bearings will not stand up to comp use.

There are more problems, but this is enough for now.

I would be very careful of having someone just "fab up" control arms without them being aware of all the compromises that are being made. Makes me very concerned that being in Germany this car will be driven on the autobahn or even the Nuremberg ring...

[Tom Kirkham]

4 Pipes. You do not have the original three piece ball joint. You have a ball pin with a spherical bearing. The original cars would pull apart. Almost impossible with our ball pin and spherical bearing. The check is easy. Jack up the front of the car and push and pull on the top and bottom of the tire and feel for any play in the ball joints.

[Tom Kirkham]

Dominik,

Front and rear uprights are completely different.
More than likely the uprights will need to be changed also.
Post (or send me) pics of the parts and I can tell you.

[4pipes]

Thanks, Tom.

[mickmate]

Duh I said Steve and meant Tom, sorry Tom. The other guy on the original suspension design project was Klaus Arning. It is an interesting design and geometry that has a lot of toe change through the suspension travel on the rear. The design also has a bind deliberately built into it which is an anti-squat feature. It was also, according to the history books, the first computer designed suspension. It was race car suspension on a road car and was a huge input of technology on 30's suspension under a 50's car. It's a shame the resources were so totally committed to GT40's that they didn't really give much Team support to the 427's in racing. Especially after they had such success with 289's.

[Dominik]

Thanks Tom, I let Carsten in Germany know.

Mods would be done by a 75-year old racing car fabricator who knows the Nürburgring in and out. He placed a Camaro in between the 911s back in the days :-) Lives close by too and still races his M8F.