428 Rear Suspension

[Emmanueld]

jbottini, I am willing to listen, please tell me your source for this 4", I deal in facts, maybe compared to a leaf-spring car you may be right but definitely all coil sprung cars share the same track! Some like the AC 289 or the Frua have narrower wheels which can make the overall with of the track narrower, but the suspension is the same!
   
   Emmanuel

[SB7019]

According to the 60's road tests the 427 has a rear track of 56 inches - as does the 428 Frau.
   According to my handbook and the published material form AC the MkIV has a track of 58.5 inches - though a 1986 Motor Trend road test suggests it is 60 inches.
   
   60's road tests of the Leaf Spring 260/289 show a rear track of 52.5 inches and of 54 inches for the coil spring AC  289.  As track is calculated as the distance between the mid point of the tyres then the suspensions can be identical with differences being accounted for in the tyre widths and wheel offsets.

[jbottini]

SB7019
    While you are correct in A. the leaf spring cars are very different in frame, track weight etc and B. in your assumptions vis a vis wheel differences, my ex CSX 3327 Street (- not a replica/extension or copy), 427 owners manual calls it this way  "track  front -53*96 standard & racing" (writers note: I assume that the 54 point 96 refers to the measurement)rear 53 standard and 55*1/8 racing. In the rear are different part numbers for the carrier, hub & calipers for standard as well as racing. I honestly cannot interpret the drawings in the manual, but I can not imagine why there would be differt part numbers for the same parts if the specs were the same.
   
   Now , my AK states  "track - front 56", rear 60". (Some of the other dimensions are different such as overall length for nose extension, weight for the "improvements", cockpit size & etc.)I have not examined the all period magazines I have, the ones I looked at agreed with my AK owners manual for an 86'.
   
   I have cross referenced parts between the two cars and find that the above rear suspension parts are not directly interchangable. I further have been advised that the Frua was an extension of the 427/428 coil suspension car, but that new uprights were done to increase the track, (it is possible that I've been misinformed)to impove both the look, road ability and clearance issues in the beatiful Frua coachwork.
   
   It is my understanding that these rear changes were kept in the MKIV to allow for mufflers (silencers for those over there) to be fitted for US approval in the rear wheel wells.
   
   While I can not, with any authority comment on what Kirkham has updated or improved on since they began (except to build the most sincere XXXXX of the type in various configurations). I heard at one time that they used a 427 SC for their digitising...if so the track should have been in the above spec area as stated.
   
   It is possible for the back space to be the cause of the track growth, but then why change other parts? Could some of this been to improve the adjustability of the alignment that was a bear on original 427's and while is more aqdjustable on both Frua's and Mark IV's it a job in itself? Unless we can dredge up a Hurlock or Ford engineer who did the design work on the 427 suspension, we may never know. I would defer some of this lore/urban legend to MKIV "a legend in his mtinmde"
   
   I'd love to know the correct answer and it has nothing to do with "4" inches in my dreams.
   Jim
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   8

[Emmanueld]

Jim, I doubt they would be different, I know that the Kirkham control arms are bolt-on on the 428, however since the Kirkham control arms are the SC designs with solid bushings, to be fitted on a street car with rubber bushings they have to be machined (tapered), this would account for the different part number from AC. That is what we did when we fitted the rear control arms to my Frua. The original Frua control arms are not adjustable, so you can't increase the ride height and keep a good geometry. The street version of the Cobra 427 MKIII also has the exhaust in the fender well. The uprights are probably slightly different to account for the different trailing arm bushings, however if they were thicker (Wider) then the half shafts would have to be different as well.
   When I had my MKIV, rear bearings on both sides were replaced using MKIII bearings. I had a problem with a half shaft and same thing. However, I know that the trailing arms are different and don't attach to the chassis with a heim joint but a much larger cylindrical bearing, similar to the Frua. I was told the control arms are the same as the other coil spring cars but that machining is required as well to account for the different bushings. If the half shafts are the same, the width should be the same as well! I think SB7019 is right and the difference if any is in the wheel offset and maybe the rotor and hub thickness! I will try to find out for sure.
   
   Emmanuel

[SB7019]

Jim.
   
   Interesting that that manuals for the MkIV should show different measurements.  Mine (from 2001) shows front 55.6 and and rear 58.5.   When it next has wheels on (currently sitting on stilts in my garage having it's winter clean and service) I will measure the actual car.  Whats the betting that this will show a different number?

[jbottini]

all bets off!!! I'm sure there will be a disparity. i will check witha couple of orcales such as trevor on this whole thread, but it certainly is confusing...

[TLegate]

I'm definately not an engineer (just an enthusiastic amateur) but I had this info from Hawk Cars today:
   
   It seems Brian Angliss brought a large quantity of Frua rear uprights and used them on the Mk4. The Frua had larger offset rear uprights to allow it to run 6x15 wheels which were spline-drive, same as the 289. They have track comparable to the front, without undue strain on the wheel bearings.

[redcar]

One possible reason for different part numbers for the rear hubs (racing/road), is that the aluminium racing calipers had a different hole spacing compared to the cast iron road calipers and as AC only seemed to thread one set of holes in the hubs they would have needed to differentiate.
   You'll probably find that the front steering arms have different numbers (racing/road) for the same reason.
   I agree with Trevor, the Frua rear hubs are different to Mk3 Cobras. The bearing position is further outboard relative to the wishbone pick up points thus making the track wider without loading the bearings.
   
   Cheers

[jbottini]

Trevor and Redman...thanks for the enlightenment.....other comments??Jim

[nikbj68]

quote:Originally posted by Trevor Legate
   I'm definately not an engineer (just an enthusiastic amateur) but I had this info from Hawk Cars today:
   "It seems Brian Angliss brought a large quantity of Frua rear uprights and used them on the Mk4. The Frua had larger offset rear uprights to allow it to run 6x15 wheels which were spline-drive, same as the 289. They have track comparable to the front, without undue strain on the wheel bearings."
   

   Words & Photos from Gerry Hawkridge to accompany the above information:
   
   

quote:From Gerry Hawkridge: Rear uprights, as you can see Frua/Mk4 on right is different to Mk3 on
   the left !!! Regards Gerry

   

[SB7019]

I think Nik has just proved that a picture is worth a thousand words!  The picture explains why a MkIV has a wider track than a Mk3.   At the same time it can explain why the Frau has the same published track as a Mk3 as the Frau wheels look like they have a shallower dish which could counteract the wider spacing of the uprights.  Does it also explain why the MkIV has the lip on the rear wheel arch that was fitted to some Mk3's only (presumably those that were fitted with wider tyres?) ?

[Emmanueld]

Interesting,now the hub itself has to be different as well, longer, correct?
   
   Emmanuel

[Mark IV]

The MK IV uses wheels with less offset than a MK III. The Frua upright/hub was specified for the MK IV by Bob Negstad, the Ford suspension engineer who DESIGNED the MK III along with Ford's Klaus Arning.
   
   Bob wanted that hub used to reduce camber change to suit the 16" Goodyear Gatorbacks that were used. Bob also bought a MK IV so I presume he knew what he was doing. Sadly Bob passed on a couple of years ago but I had the great pleasure of knowing him.
   
   One day when I saw Bob in Dearborn with his Roush powered car, he told me that if he, Jack (Roush) and Michael (Kranefuss)all of whom had stroked 351s in the cars, revved 'em to 5000 and dropped the clutches at the same time, the Earth's rotation would change!
   
   Rick

[jbottini]

Interesting, the parts are different...any other comments?

[Emmanueld]

AK02 had a Roush built 351 Windsor, It was not very powerful and rought running, 5000RPM was the most you could get! Hot rodders over here like the 346 which is a bored out 302, with a good set of heads, it is supposed to be the best running small block!
   
   Emmanuel