Original Cobra Hub face to Hub face Measurement?

[Ant]

Can anyone help me with a ballpark measurement of the original front suspension Hub face to Hub face, that is where the back of the wheel touches the pin drive flange, of either the Trigo adapter or original six pin hub.

Also approx length of suspension arms from inner pivot to center of ball joint, as I have a wheel hitting guard problem with a 235/60-15 Bridgeston 340 Eager (I have only borrowed this new tire, but its the approx right diameter of 26.3") and its cross section is 9.5" which interferes with guard.

My aim is be able to import Goodyear slicks from either Roger Krause or Goodyear, else use Hoosiers which are readily available in this country, but they all seem to have wide cross section on a 7.5" wheel of around 10.4" thats the buldge of the tire!!

Having said all that my car has original style body taken from an original and original dimension offset Trigo wheels.

[mickmate]

Ant maaate, see what ya think of my numbers.
Front wheel width 7.5"
Actual width 8.425"
Offset edge/hub 3.625"
Original track 56"
Half wheel width to centre (track) 8.425"/2=4.2125"
hub to track (wheel center) = 4.2125-3.625 = .5875"
Track + (2 X .5875) = 56 + 1.175 = 57.175" flange to flange.
I'm glad to see more people this deep into it. We gotta keep kicking this stuff around. Let me know what you think.

[Ant]

mickmate,

Yep thats helpful information, will check mine out and see what I come up with. The problem I have got is the car was built Body/chassis in the effort to make it easier to certify with the Land transport here in NZ, or as the manufacturer states a Sportsman chassis, which is okay and serves a purpose, but throw me into the mixing pot and its nowhere near advanced enough handling wise.
If there was a next time I would just get a body and make my own chassis, and start from the wheels first, but I am doing that now!!!!
We have the patience, so this baby is going to get a modified Cobra Coupe style or "much better in theory" race chassis, and good suspension geometry.

Another thing I am curious on and this is really what works in each individual situation depending on chassis width, Is the length of an original top and bottom front suspension arms
I could end up with a bottom arm measurement of 11.25" and top arm of 7" thats pivot point measurements, I dont really want to go any shorter, but will check out body roll and camber change and it still may be a good compromise.

I have looked at arms on Canam McLarens etc and some of those are really short, and I realize that they have very little suspension travel, and also some Tranam cars setup to run on radial slicks have shorter style arms to get this compromise.........I think I will shut up now in case I get my mouth gets me in the s**t

[Rick 427 Cobra]

Glad to see this topic.
First question, where exactly is "track " measured? Center of the wheel, hub face or outside tire surface?
Second, what is the difference in track between a slabside and a street 427?
Kirkhams talk about using a "hybrid" chassis on a 289. How?

[chopper]

I don't know if this is of any help to you guys, but I found this site about the Coupes while doing some dreaming:

http://www.thecarsource.com/shelby/c...tonaspecs.html

and they quote a number for front track at 51.5 inches, rear track at 52.5 inches. Since all of the coupes were built on the roadster chassis, I would assume they're the same for both cars. Any help?

[grumpy]

ANT,
You have eMail in exchange for the *.jpg drawing see my eMail on the rear request noted.
I hope it didn't go via slow boat to China then to down under.
grumpy

[Robert Duncan]

The reference that I have (AC Cobra The Complete Story, Brian Laban) indicates the 289 track was 51.5"/52.5" F/R and the 427 was 56"/56"/F/R. Not sure if this is flange to flange or not.

[mickmate]

Hey Ant, I think this is supposed to be
Track - (2 X .5875) = 56 - 1.175 = 54.825" flange to flange.
Rick the track should be centre of the tire to centre of the tire. The outer suspension pivot points should line up with the tire centre or you will get scrub steer. This is important as you know how heavy your steering gets with a worn balljoint never mind a mislocated one! This is where it gets confusing as Robert points out about every piece of cobra literature I have seen with specs gives a 56" track front and rear for the 427 and coil sprung 289's. The chassis instruction/ owners handbook for the 427 gives a track of 53.96" on the front for std and racing and rear is 53 std and 55 1/8" racing. These last couple of numbers are I believe the flange to flange dimensions not the track dimensions as that is what works with the dimensions I have compiled for the rear. That allows for different wheel widths and offset between the different models ( same track though ). The 52.5 and 51.5 numbers are for the 289 and coupe which was built on the roadster chassis. Chopper it was the "289" roadster with 3" frame rails and leaf sprung. I believe the Kirkham hybrid reference is the 289 body on the 427 (4" frame rails ) coil sprung chassis.
Ant, what parts are you working with? Are you stuck with frame mounting points or the stub axle mounts as you need to establish some points for dimensions considering bumpsteer, steering rack length, tie rod lengths, roll center height and on it goes. If you are making the a-arms you must be able to move some points to get your geometry correct.
Grumpy, could you send me the info you sent Ant also please. Remember your buddy who sold you the FFR interior at a good discount

[Ant]

grumpy,
Thanks for the mail, and now will work through the critical pathways and see what needs to altered or even remade, as below!


mickmate,
I am working with a Holden Torana rack and pinion with lower inner pivot points at approx 25.5" apart (1" further apart than original) I assume the original uses an MGB rack and pinion steering. My setup looks quite original but as mentioned is based around this steering unit, with 3 turns lock to lock, but is very quick with short steering arms!

At this point we are now using 2" dropped special axles, and have a front roll centre about 3" above ground, the rear is higher up, but we haven't got to that yet.
We are now going to look at bump steer and the possibility of moving the lower pickup points inwards about 1" each side to get suitable wheel to body clearance. The top arm is easy as its out about 2" from the bottom and the whole mount can be moved across, if I cant move the lower mount in due to steering issues with bump, then I can shorten the lower arm 1" down to 10.50" and the top arm is now 7.5" (I hate shortening these arms) as what I have read in the past, but.......camber curves with 1" of suspension travel to 1 degree of negative camber might require a short top arm. A good point maybe with the bottom arm is it is below center and going through its travel will lengthen and then shorten a small amount above centre!

I am a learner at car suspension geometry, as you can probably gather, so I am going to stop working on other areas of the car and get this sorted properly.

[mickmate]

Ant, does the Almac have some frame issues or are you going for different look or application on the hardware? You can make about any hardware work if you are able to move suspension points around to where you want them. The trouble is where do you want them. The Mustang II set up is popular as all the geometry stuff is a known factor. This obviously wasn't designed for a Cobra which is why I wouldn't put this set up in my car. There's a lot to be said for someone having it all figured out for you though so the hard part is just putting it in there. It comes down to what you want, can afford, and can do yourself. What is your other hardware, spindles etc?

[Ant]

mickmate,

The almac is a good kit and a good compromise for road and "sportsman" type racing. I am going to run Goodyear slicks or Hoosiers which are of a less diameter, and being 26.3 - 26.5" this complicates suspension geometry etc, and I am going for 4.5" chassis clearance front and 5" rear, because with the different spindles I have just imported gives me good roll centers etc, but I am getting heaps of bumpsteer.

My setup is based on the Holden Torana XUI/L34 setup, but uses Holden HQ spindles and Torana 3.25 turns steering rack with shortened steering arms, the setup looks very much like an original Cobra, but very much like an ERA with 4X3 rhs box section, which we are once all the front and rear wishbones etc are altered to firstly suit Trigo knock off wheels and sort geometry we are going to reduce main rails to 3X3 rhs and fit a chrome moly backbone much like a Cobra coupe linking all the suspension points. We are going to make a jig to hold all the relevant points and then get a Plasma cutter etc.

This is probably going to put my project back a year but handling is paramount before horsepower in race cars years ago we didnt know any suspension issue apart from castor camber and changing shocks and springs, this time its geometry and getting a suitable compromise.

The car has T/bird rear end with the H type suspension, this is going to get a once over with refabricated arms and a proper rose jointed top wishbone with anti-sqaut built in instead of a single strut with a wide bearing as it has now. The chassis will be lighter than it is, stiffer and hopefully will turn in nice and have good driveability, but its still a road car first.