Subframe connector question.

SIIaCanuck

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Has anyone tied a full length sub-frame connector to the floor pan along it's entire length? If so, what was the result.

Looking at it, a sheet metal sheer web between the sub-frame connector and the floor pan should give 90% of the stiffening effect of a through-floor installation without the intrusion into the footwells.

I know it'd cost a fortune in fabricating if you paid a shop to do it, but if you have your own shop and time to do the work, it seems like it could work well to really stabilise the whole floor pan.

I'm thinking of a competitive autocross car that remains a daily driver.

Thoughts?
 

white95

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One of the most competitive, auto cross Mustangs is owned by MadStang and he has Roush, full length subframe connectors (FLSFC) that are tied into his roll bar.

roush113014.jpg



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Paul94gt

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I have a set of full length Maximum Motorsport connectors for my 94GT. Hopefully I will have them in sometime in September. The car isn't going to bebuilt as competitive as above, but it is certainly going to be sporty. Were I too put a cage in it, it would be tied to the connectors as mentioned above. As for zipping up the pans to the subframe connectors, wouldn't it stiil be better to do throught the floor connectors and weld the floors to the boxed steel?
 

white95

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I have MM FLSFC and when I jack my car up behind the front K member mount and it lifts the rear tire also.
 

Paul94gt

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Makes me so happy to hear that. I can't wait to get mine installed.
 

ttocs

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I had to go to spintech for my sub frame connectors to get around the side exhaust they are stepped. I know it gave me a bit of a scare the first time I jacked up the rear pass side and saw the front pass wheel come off the ground. I thought the weld in full length connectors were welded into the floor?
 

ttocs

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I was right on the verge of buying my welder and doing it myself when I had mine done but my stomach crap was keeping my physically from doing it. I think I got the welder 4-5 months later after all so I wished I spent the money I paid for install toward the welder but again physically it would have been hard. Its been years since I looked at them but I there were a couple bends in them, do you have access to a metal break to bend them?
 

SIIaCanuck

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I'd considered the through-floor connectors but would prefer not to go that route for a couple of reasons.

First, the car will remain my daily driver so I don't want to mess up the interior floors and/or carpeting.

Second, while MM's full length connectors would probably be just fine for my application on their own, I'm an engineer and I've built one, and helped build two more, semi-spaceframe cars in the UK when I was in the RAF (mine was a Sylva Striker Mk.II). I modified the chassis on my car and one other and I'm always keen to try to find another way of skinning the cat.

The main weakness of the Fox/SN95/Fox-4 chassis is the floor pan, with insufficient stamped in stiffness features to prevent buckling instability under load (particularly for high performance loadings). A sub-frame connector carries part of this load and provides additional stability to the floor-pan through the seat connector but I figured that a full-length connection would help the floor carry greater loads before any buckling occurs. That'd add rigidity and fatigue resistance (if the floor isn't buckling, you won't get the localised fatigue cracking along the rocker panel).

However, I wondered if someone else had tried the same thing and, if so, what difference did it make.
 

wmfateam

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I have through the floor connectors and when I had my carpet in you could not tell.

Sent from my XT1254 using Tapatalk
 

jun10r

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Wow some really neat options here, I thought the comment at Griggs was interesting about mandatory for Verts! Def subscribing here to find out more!!


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SIIaCanuck

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The issue I have with Stifflers ladder system is that it does nothing to address the main problem, that of poor rigidity in the floor pan. It adds weight and possibly strength, but strength isn't the problem, this isn't a highway tractor.

The engineering issue with the Stifflers product, as well as the Kenny Brown version and Global West's (there may be others) is that they do nothing to tie into the floor pan and prevent buckling instability, the main design failing with the monocoque structure of the Fox/SN95/Fox-4 chassis. The ladder structures built by these companies act in the same plane as the floor pan and add no third dimension structure to add stiffness.

Strength isn't the problem with the Mustang chassis, buckling instability (and over the long term, localised bending beyond material fatigue limits) is.

The Griggs system uses through-floor upper sub-frame connectors. As they tie into the floor pan along their entire length, they add the vertical structure needed to counter buckling. However, that takes us back to the invasive through-floor option.

I've asked a lead engineer from another aftermarket supplier about this idea. He also considered the option that I'm looking at and says it will add considerable stiffness by increasing the effective depth of the sheer web of the connector. However, as the Mustang floor pan is so flexible, it would be impossible to produce a laser cut pattern to match the bottom of the floor so it wouldn't be a commercially viable option. The only option is to custom cut and fit the structure.

I guess that's the answer I was looking for. It'll perform much the same function as the Griggs upper connector but without altering the interior floor.

And so the scheming continues!
 

SIIaCanuck

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You need something like this then if you're wanting to get away from the flimsy floor pans.

http://www.schwartzperformance.com/1964-1973-mustang-chassis-full-frame/


Please tell me this is a joke! Instead of stiffening a monocoque into a decent chassis, you think I should put a 1930's Model A frame under it!?

I've got a '69 Land Rover with a Heavy Duty Richard's Chassis under it. It's 3mm wall thickness welded box section throughout and will outlast me and take being dropped by parachute out of a Herc. However, it'll still flex more than a stock Mustang chassis.

That's why the original Cobra was such an evil handling car, the chassis was a ladder frame and only managed about 900 ft.lbs/deg of torsional rigidity. Factory Five's Mk.IV has a backbone structure in the centre section and gets over 4000. David Borden customised his and got it in the region of 8000, a fair stiffness for a 2100lb sports car.

The stock Fox-4 is stiffer than that, with a 2003 coupe at about 11800 ft.lbs/deg. However, the floor pan lets the rest of the chassis down so it needs stiffening.

Sitting it on a Peterbuilt frame won't add anything but weight.
 

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