T-Top Frame Connectors ?

[racerxmd]

Undecided on frame connectors for my '85GT T-Top car. I already have the Maximum Motorsports Full Lengths bars that are new and ready to install, but might do the Thru-Floors like my MDmonster project. What's your opinion?

Thanks

[xctasy]

If you love the car and want to enjoy it, Tick the box and have them installed. Frame strength in a Fox is marginal when the car has the T roof. No one loses points for protecting a uni body car used for performance. The only thing is periodic checking for rust when you've welded something non stock into a unibody car.

[brianj]

Full length sub connectors are plenty strong, don't interfere with foot space, and install easily. Through the floor are probably stronger, but unless you are doing truly brutal things with the car, they are probably overkill.

[wraithracing]

I second the opinion that full length SFC like MM are plenty good for a street car, even with T-tops. If you plan on serious Road Racing or Autocrossing, then maybe the thru floor connectors. Good Luck!

[erratic50]

+1 on full length under car unless you will be heavily abusing the car.

My 1/2 million mile 1986GT had 200K miles when it developed a 1 7/8” twist in the body. My fault - I ran it without any connectors for years. I had done some work - SD friendly cam, ported intake, carbide opened then patch welded back stock headers, VM1 ECU, timing cranked up to the max, etc. Straw that broke the camels back was slicks plus a shot of NOS ....

A body shop straighten it out and welded up the body worked the diagonal crack in the floor then arched the center of the body slightly and welded in HPM subframe connectors.

I havent dared run slicks or NOS on it since but they cured it. The car has near 1/2 million “drive it like you stole it” miles on it now. Frankly if it didn’t have connectors the body would have fallen in 1/2 from rust a while ago. The car still drives fine and feels good with connectors under it.

I will never make the mistake of doing any spirited driving in any 79-04 Mustang that doesn’t have subframe connectors ever again. If you plan to drive your car with any authority at all ..... if you don’t like “left on gas, right on brake” autosteer to the point it’s undriveable you need subframe connectors. Shame on Ford for not doing it from the factory!

Also it is a major safety consideration. You would not believe how poorly a fox holds up in the midsection without connectors and you also won’t believe how well they do with. Guaranteed there was one person in Omaha last year that’s alive because of their decision to weld in connectors. Their driving choices being a topic for another thread.

The Maximum Motorsports subframe connectors Trey welded into my 1985-006 Saleen project are a stout piece and will no doubt handle everything I throw at them. They are the best the market currently has to offer IMO. If you dig you can find new in box moly SFC from HPM out there still. Those are the only other one I’d look at if making a 2nd choice for my cars simply because I have experience with both.

My dad and I helped my son weld in SFC on his convertible. It’s not something to leave to chance. If you don’t have an old iron and construction worker or body man with 50 years behind a fire stick helping you or haven’t passed the plate steel certification test yourself, just have them professionally done. Weld strength matters!

[xctasy]

There’s a lot of flex in any of the early 1978-1993 Fox bodies, but it can be tamed by adding supports that stiffen the chassis structure.

If you've ever driven an old A or B body Mopar with torsion ride IFS hard, the corkscrew motion is the tosion effect, and it creates uncontolled pitching. The Fox Mustangs unstable transitional responses from understeer on entry to un contolled over steer on exit is mostly due to a lack chassis ridgity. The four link geometric rears problems are eccentuated by the chassis lack of strength in bending. Ackerman issues, TRX ties, lack of feel in the power steering, they are minor in comparison.


For Ford to fix this at a factory level would have required retooling, and most likely re crash testing, along with wheelbase changes to do with the front subframe position....and then pre production prototype work, and a whole bunch of the Fox 4 chassis additions. On every line of Fox platforms. Any State trouper will tell you, a Fox is kind of cramped head room wise compared to other Fords. Fords costly re profiling of the floor on 82 Mustangs and some other Foxes was evidence of the limited space even in a unibody. The added intrusion on the already cramped head room on the Foxes prevented Ford doing anything structural unless it was associated with the newe S cars, the Stirling built Tbirds, LSC's and Cougars.

So the Stang and Capri never got upgraded like it could have for 1989...the rear drive Mustang was supposed to die that year, and be replaced by the Ford Probe. Further Fox 4 chassis stiffening updgrades as per the SN95, had to wait another 5 years.

See http://vb.foureyedpride.com/showthre...ts-on-bare-car

Muliply 1 kg m (kilogram meter) by 7.233 to get ft-lb torque
Divide 1 Nm by 1.3558179483314004 to get ft-lb torque.
http://www.eng-tips.com/viewthread.cfm?qid=354865

11 Nov 13 19:30

Chassis Stifness:


Alfa 159 - 31,400Nm/degree ----->23151 ft-lb per degree
Aston Martin DB9 Coupe 27,000 Nm/deg
Aston Martin DB9 Convertible 15,500 Nm/deg
Aston Martin Vanquish 28,500 Nm/deg
Audi TT Coupe 19,000 Nm/deg
Bugatti EB110 - 19,000 Nm/degree
BMW E36 Touring 10,900 Nm/deg
BMW E36 Z3 5,600 Nm/deg
BMW E46 Sedan (w/o folding seats) 18,000 Nm/deg
BMW E46 Sedan (w/folding seats) 13,000 Nm/deg
BMW E46 Wagon (w/folding seats) 14,000 Nm/deg
BMW E46 Coupe (w/folding seats) 12,500 Nm/deg
BMW E46 Convertible 10,500 Nm/deg
BMW X5 (2004) - 23,100 Nm/degree
BMW E90: 22,500 Nm/deg
BMW Z4 Coupe, 32,000Nm/degree
BMW Z4 Roadster: 14,500 Nm/deg
Bugatti Veyron - 60,000 Nm/degree
Chrysler Crossfire 20,140 Nm/deg
Chrysler Durango 6,800 Nm/deg
Chevrolet Corvette C5 9,100 Nm/deg
Dodge Viper Coupe 7,600 Nm/deg
Ferrari 360 Spider 8,500 Nm/deg
Ford GT: 27,100 Nm/deg
Ford GT40 MkI 17,000 Nm/deg
Ford Mustang 2003 16,000 Nm/deg
Ford Mustang 2005 21,000 Nm/deg
Ford Mustang Convertible (2003) 4,800 Nm/deg
Ford Mustang Convertible (2005) 9,500 Nm/deg
Jaguar X-Type Sedan 22,000 Nm/deg
Jaguar X-Type Estate 16,319 Nm/deg
Koenigsegg - 28,100 Nm/degree
Lamborghini Murcielago 20,000 Nm/deg
Lotus Elan 7,900 Nm/deg
Lotus Elan GRP body 8,900 Nm/deg
Lotus Elise 10,000 Nm/deg
Lotus Elise 111s 11,000 Nm/deg
Lotus Esprit SE Turbo 5,850 Nm/deg
Maserati Quattroporte - 18,000 Nm/degree
McLaren F1 13,500 Nm/deg
Mercedes SL - With top down 17,000 Nm/deg, with top up 21,000 Nm/deg
Mini (2003) 24,500 Nm/deg
Pagani Zonda C12 S 26,300 Nm/deg
Pagani Zonda F - 27,000 Nm/degree
Porsche 911 Turbo (2000) 13,500 Nm/deg
Porsche 959 12,900 Nm/deg
Porsche Carrera GT - 26,000Nm/degree
Rolls-Royce Phantom - 40,500 Nm/degree
Volvo S60 20,000 Nm/deg
Audi A2: 11,900 Nm/deg
Audi A8: 25,000 Nm/deg
Audi TT: 10,000 Nm/deg (22Hz)
Golf V GTI: 25,000 Nm/deg
Chevrolet Cobalt: 28 Hz
Ferrari 360: 1,474 kgm/degree (bending: 1,032 kg/mm)
Ferrari 355: 1,024 kgm/degree (bending: 727 kg/mm)
Ferrari 430: supposedly 20% higher than 360
Renault Sport Spider: 10,000 Nm/degree
Volvo S80: 18,600 Nm/deg
Koenigsegg CC-8: 28,100 Nm/deg
Porsche 911 Turbo 996: 27,000 Nm/deg
Porsche 911 Turbo 996 Convertible: 11,600 Nm/deg
Porsche 911 Carrera Type 997: 33,000 Nm/deg
Lotus Elise S2 Exige (2004): 10,500 Nm/deg
Volkswagen Fox: 17,941 Nm/deg
VW Phaeton - 37,000 Nm/degree
VW Passat (2006) - 32,400 Nm/degree
Ferrari F50: 34,600 Nm/deg
Lambo Gallardo: 23000 Nm/deg
Mazda Rx-8: 30,000 Nm/deg
Mazda Rx-7: ~15,000 Nm/deg
Mazda RX8 - 30,000 Nm/degree
Saab 9-3 Sportcombi - 21,000 Nm/degree
Opel Astra - 12,000 Nm/degree
Land rover Freelander 2 - 28,000 Nm/degree
Lamborghini Countach 2,600 Nm/deg
Ford Focus 3d 19,600 Nm/deg
Ford Focus 5d 17,900 Nm/deg

1. A Fox hatch is only about 4200 to 6200 lb-ft per degree of torsional load, very loose, and
2. It drops as it ages, rusts, or fatigues. Sun roof and t roof options drop the figure below 4200 lb-ft per degree of bending.
3. Only 75% of the factory spot welds take, so they are below full possible strenghth from birth.
4. The Notch is about 20% stiffer.
5. The Fox 4 SN95 and New Edge SN98 are far stiffer, but all new cars have gotten stiffer as car makers spend more budget on this.

A Lamborghini Huracan has 25807 lb-ft restance per degree of bending. The best modified road car might make 44000 lb-ft with a full cage and all the stiffining gear. The Bugatti Veyron was that stiff off the production line.

Chassis stiffness stops the most of the known "Ricochet Rabbit & Droop-a-Long" problems with the stock four link Fox rear ends chronic binding under on and off throttle, the things that cause a lack of stabilty in "on throttle" overstear.



Ford and GM both understood perfecly well that four link live axle rear suspensions with rack and pinion steering unibody cars had the potential to be world beaters in handling. The Australian 1978 VB Commodore had the same rack and pinion steering as the Mustang.


The Fox Mustang and Unied Kingdom TC-TF Cortina and West German TC-1-TF Taunus didn't steer badly, the US Fox chassis was better than the Cortina and Taunus by a significant margin, but each had a very bind prone bushing system on the rear four link suspension.

The Fox had much more torsional rigidity, but wasn't untill 1994 and the SN95 that the twisting resistance in foot pounds per degree of bending improved enough to support fully fleged 351's and Modular V8's. Jack Roush found that the 25 th Aniversay 5.8 Mustang wasn't able to meet the chassis durablity targets.

It was planned to axe the Fox platform, and the planned mid 1989 "King of the Hill" ZR-1 Vette slayer never got released due to that body twisting and gearbox durabilty issue.

GM Germany was stuck with existing recirculating ball steering patents and contracts from key supplier ZF, so the GM V car (based on the 1966 Opel Rekord C, 1967 to 1971 Opel Commodore A, and 68-72 GM Ranger A/66-71 FD Victor/Ventora) was manufactured with old style recirculating ball steering. The English versions of the car, they used Cam Gears rack and pinion steering, just like the UK 71-83 Cortina/ German TC1-TF Taunus, Australian VB Commodore. And the Fox Fairmont and Mustang used it as well as the same power steering as the Vauxhall Ventora.

In the Fox chassis Fairmont and Mustang, Ford USA copied the Cortina rear suspesion hard dimensions into a Pinto/Mustang II base chassis with a similar upper strut system to the German Commodore C based Independent Front suspension. The lower coil spring was a blended Pinto/Mustang II subfame structure, so essentialy, the Fox Mustang was very much a development of the European Cortina/Taunus T series of 1971, and the exsting Pinto/Mustang II hard points.


Ford discovered that forward mounting the rack and pinion steering reduced over steer, and they left the compression binding Upper and Lower arm Four link with its problematic geometery as it was. Vauxhall and Opel had found that Fords Galaxie Panhard rod, a 5th link on the GM V cars, was able to unbind the upper links in a similar manner to the poor mans three link. Ford didn't do anything much to the four link rear. They were more worried about how the Cortina, Taunus and GM V car axles vibrated so badly and wanted to avoid using the Cardan jointed drive shaft that caused so much NVH in all those cars. The dog bone axle counterweght and gear box vibration damper was the result.

[vintageracer]

Thru the floor connectors.

Let's cut that sucker up!!!!

[2nd chance cobra]

As I read through this I noticed a comment by erratic," the gas left turn and brake right turn" I have noticed this on my car and chalked it up to need ing to "recheck" the underside of my car. Not to hijack but is this correct/common on un connected framerails?

[Tula77]

I am a visual learner. How about pictures of the recommended solutions?

[homer302]

https://www.youtube.com/watch?v=qhRETBALi10

http://forums.corral.net/forums/road...or-instal.html

[erratic50]

If there is unibody flex, it will do it a little without being noticeable. If the unibody is twisted it will do it all the time and it can get quite severe.

When Autokraft took mine on in 1997 the main things found were:
1 - 1 7/8” diagonal twist in the unibody
2 - diagonal cracking in the floor mostly following a line between the left motor mount and the inside edge of the right rear tire
3 - cracking at the A pillar and rear roof seam.

fast forward another 250K miles and the right rear and left front springs were broke too. Hard to say how long they were that way honestly. That said the twisted unibody fix held up.

the twist was corrected on a frame machine. Chain the car down to the frame table on the low sides. Heat the areas sprung then pull the opposite corners down while the center is supported. Once it was flat it was twisted opposite 1/16” and the floor cracks were cut out and welded then worked back to show no signs of the operation. next the center was tensioned 1/8” and subframe connectors were welded in. When all was said and done it was true side to side and diagonally.

The roof seam at the A pillar got tacked back but without removing the glass and the rear of the top was left alone. No body work was done to fix the roof seam cracks.... this is how the car is to this day.

I was told at the time that if it sprung again the only options were the scrap heap or a full cage. Fortunately it’s held up, but I haven’t put slicks on it or sprayed it since either.....