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Mitch Alsup (Mitch_alsup)
Username: Mitch_alsup

Post Number: 871
Registered: 4-2002
Posted on Friday, July 11, 2003 - 1:58 pm:   

"No matter if the car is cut to a targa or cab, once there is no support thru the roof section, the only support is the floor pan. A flat floor pan is not very stiff when it comes to torsional forces."

Take a piece of tubing 1" in diameter and measure its stiffness with respect to bending. Then take a piece of the same material 2" in diameter of the same wall thickness and measure its stiffness. The 2" stuff is 8 times stiffer than the 1" stuff. If the wall thickness is scaled up in the 2" tube, the resulting stiffness is 16 times as much as the original 1" tube!

What this means is that to regain the stiffnes of a thin roof section 35" away from the rest of the frame will take a great amount of reinforcement!

Since cars chassis are designed to carry the majority of their loads in the main frame, and little across the roof; chopping off the roof does not lead to undrivable cars, but just to chassis that are no longer anywhere as stiff as they were before chopping.

Now you know the reason race cars use full tubular roll cages and integrate them into the chassis as stiffeners. The bars nearest the roof begin to carry 'significant' loads and provide a great "moment" (~= covered area) of stiffness to the chassis.
david handa (Davehanda)
Intermediate Member
Username: Davehanda

Post Number: 1191
Registered: 5-2001
Posted on Friday, July 11, 2003 - 1:56 pm:   

Robert Oglesby (Testar1988)
New member
Username: Testar1988

Post Number: 16
Registered: 5-2003
Posted on Friday, July 11, 2003 - 10:12 am:   

Your right on the $$$ with that comment!!! A kit car who gives a rat's...!!! but a TR??? I think Enzo would be rolling over in his grave on that one!! But like you said, it's his money, and his car, but the thought does sting!!!!
Paul Thompson (Paul_t)
New member
Username: Paul_t

Post Number: 3
Registered: 6-2003
Posted on Friday, July 11, 2003 - 3:51 am:   

Cutting a Testarossa kit car is one thing but to cut the real thing is, in my eyes a horror story. I know it is your own car and you can do as you please but think VERY carefully before lighting that torch!!
Dave Wapinski (Davewapinski)
Username: Davewapinski

Post Number: 561
Registered: 8-2001
Posted on Thursday, July 10, 2003 - 9:59 pm:   

Also on a cut car, if the next owner has an accident and blame can be placed on the car not being regid enough, can you be held legally libel?

Do not know the law, but I think you can be held libel.
Verell Boaen (Verell)
Username: Verell

Post Number: 942
Registered: 5-2001
Posted on Thursday, July 10, 2003 - 9:42 pm:   

Chances are good you could sell your TR, buy a Straumann converted one & bank some $$.

Straumann put a fair amount of engineering time into the design of his conversions. Even so, allegedly they don't handle very well on the track.

MY $0.02:
A Strauman conversion is recognized as quality work. To be blunt, No one's going to want to buy an unknown amateur's conversion. But, it's your car...
Robert Oglesby (Testar1988)
New member
Username: Testar1988

Post Number: 15
Registered: 5-2003
Posted on Thursday, July 10, 2003 - 12:16 pm:   

I find it hard to image cutting a top of a TR, we are not talking here about a old Chev!!!! This is a fairly low production car, the idea to butcher it give's me chills..My thought's are, if you must have a spyder, buy a 348, 355, 360!!! I own a 88 TR, someday I will buy a spyder, but I think I can wait for a factory model!!! Just my 2 cent's worth...Robert
Craig Dewey (Craigfl)
Username: Craigfl

Post Number: 643
Registered: 1-2001
Posted on Wednesday, July 09, 2003 - 2:44 pm:   

No matter if the car is cut to a targa or cab, once there is no support thru the roof section, the only support is the floor pan. A flat floor pan is not very stiff when it comes to torsional forces. That's why you get the "cowl shake" in a lot of convertibles -- the front of the car is twisting with respect to the rear.

It would be very difficult to regain the torsional rigidity that would give you back the cars original handling. You might be able to gain something so it would be acceptable on the street. Some places offer a stabilizer subframe mounted under the floorpan to add rigidity. I've even seen some cars where the doors were modified to fit tightly and add rigidity.
Luigi Nicoletti (2mmuch)
Junior Member
Username: 2mmuch

Post Number: 73
Registered: 9-2002
Posted on Wednesday, July 09, 2003 - 12:29 pm:   

I was planning on doing it myself. I was wondering if anyone had info on the Straumann conversion. Did they have to put in any type of sub frame to support the car from splitting in half before the roof was cut off.
Henryk (Henryk)
Username: Henryk

Post Number: 901
Registered: 8-2001
Posted on Wednesday, July 09, 2003 - 10:56 am:   

I think the targa version would look nicer than the convertible.

When my 88 TR gets down in value, let's say into the $20Ks, then I may consider doing it myself.

To pay someone to do it, on a $20K car, would be stupid!!!!
Evan Friedman (Evan)
New member
Username: Evan

Post Number: 12
Registered: 5-2003
Posted on Wednesday, July 09, 2003 - 10:30 am:   

The reason the handling went down the drain was that there was inadequate frame reinforcement. Even with that, there is more chasis twist possible. My GTO kit required a roll bar and reinforcement revision before it started handling rock hard again. It too is a convertible. What did you do to reinforce the Testarossa kit? I have steel tube in the rocker panel carried through a double hoop roll bar, welded to plates welded to the side frame behind the door and into the rear shock towers. The front of the tube welds to another plate at the front door hinge location. SOLID. Check out my website and you'll see the original vs the replacement roll bar. As far as the Ferrari, you can wait untill a Straumann conversion presents for sale. I think it would be very costly to carry out yourself. Catch the depreciation and you get to evaluate the job before you buy. These cars will only be worth money to those specifically looking for them.
Luigi Nicoletti (2mmuch)
Junior Member
Username: 2mmuch

Post Number: 71
Registered: 9-2002
Posted on Wednesday, July 09, 2003 - 9:22 am:   

Ok here goes nothing. You see about 6 years ago I build a Testarossa kit car. 2 years after I had the car I got the itch to make it convertible. After a year of modifications it was complete and looked great. I included a picture to see for yourself. The problem was that after I did this the cars handling went out the roof to. After driving it for a couple of years I decide to sell it and buy the real deal. But there was nothing like driving around town in a convertible Testarossa. Now I own a real 87 Testarossa and guess what, the itch is back. Call me crazy and my wife thinks I am but you see I was looking at a 348 convertible and I just can't get that sweet look of the Testarossa out of my head. Also I know my car and everything I did to get it just perfect. I've seen convertible Testarossa's on the net and I was just looking for information. Frame strength? Handling after the roof is removed, etc. Is there any flex in the body? Will the door start to hitting after awhile do to not enough frame support in the middle of the car? Is there anybody out there that does this type of conversion? I know the Testarossa is a great looking car just the way it is but a convertible is heaven. I would why Ferrari never made one??? Just thinking out loud.

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