C4 design question
Thread Starter
Burning Brakes
Joined: Jun 2014
Posts: 1,020
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From: Connecticut
C4 design question
So this is a question for all of you that know the in's and out's of the design of the C4.
Why does the Targa Top not have the the front release handles that were designed for the Convertible Top?
I know the Convertible C4 came a few years behind in the C4 era but the design probably was there already.
I have only been in a C4 Targa once with the top off and I remember it being quite the process of undoing the allen bolts, lifting and then storing the top.
I had a demonstration of the new C7 and was surprised the top came out so easily. No tools required. Three latched and out it comes.
I love the look of the Targa Corvette and would love to add one to my garage alongside my convertible. I think it is the best of both worlds with almost none of the compromises.
Why does the Targa Top not have the the front release handles that were designed for the Convertible Top?
I know the Convertible C4 came a few years behind in the C4 era but the design probably was there already.
I have only been in a C4 Targa once with the top off and I remember it being quite the process of undoing the allen bolts, lifting and then storing the top.
I had a demonstration of the new C7 and was surprised the top came out so easily. No tools required. Three latched and out it comes.
I love the look of the Targa Corvette and would love to add one to my garage alongside my convertible. I think it is the best of both worlds with almost none of the compromises.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
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From: Ashland Alabama
Because if I release my convertible top at 55 mph its not likely to actually come off the car but even if it does its not likely to kill anyone.
You pop the top on a targa at 55 mph and it gets wind under it somebody behind you is getting a killer frisbee in the face.
You pop the top on a targa at 55 mph and it gets wind under it somebody behind you is getting a killer frisbee in the face.
Thread Starter
Burning Brakes
Joined: Jun 2014
Posts: 1,020
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From: Connecticut
Still... the new C7's have latches similar the convertibles so that alone cannot be the answer.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
Never watched fast and furious actually. They launch a targa top in it?
The bolt down design was part of gm's safety worries. There is so much flex on a coupe with the targa top out that with it in and the lock design the convertible uses it would never hold.
Without an x brace like the convertible has the coupe flexes a bunch with the top out.
All the car companies during that time were using the threaded bolts too.
The bolt down design was part of gm's safety worries. There is so much flex on a coupe with the targa top out that with it in and the lock design the convertible uses it would never hold.
Without an x brace like the convertible has the coupe flexes a bunch with the top out.
All the car companies during that time were using the threaded bolts too.
Thread Starter
Burning Brakes
Joined: Jun 2014
Posts: 1,020
Likes: 51
From: Connecticut
Never watched fast and furious actually. They launch a targa top in it?
The bolt down design was part of gm's safety worries. There is so much flex on a coupe with the targa top out that with it in and the lock design the convertible uses it would never hold.
Without an x brace like the convertible has the coupe flexes a bunch with the top out.
All the car companies during that time were using the threaded bolts too.
The bolt down design was part of gm's safety worries. There is so much flex on a coupe with the targa top out that with it in and the lock design the convertible uses it would never hold.
Without an x brace like the convertible has the coupe flexes a bunch with the top out.
All the car companies during that time were using the threaded bolts too.
I can only imagine that is what it would be like in a C6 Z06 or ZR1 when the roof delaminates and blows off. Who else used a bolt on Targa? The C4 is my only real experience with a Targa and it's removal. I have seen the early Porsche 911's but never saw one while the targa was being removed. If I recall correctly, the those were folding canvas style tops.
I get the C4 top is part of the upper structure and needed for rigidity of the frame and the car was initially designed to have a T roof vice Targa. However, I just think a better design could have been made by the end of the C4 life span. Seems that the Targa design was really never revisited during the C4 lifespan.
I have no idea how the C5 or C6 Targa latches so I have no idea wen the bolts and "special tool" process were abandoned in favor of latches.
Race Director
Joined: Jan 2007
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From: NYC NY
With an additional 30 years of development and structural improvement the C7 should be easier to remove and have less of a body rigidity compromise when it's removed.
The C4 chassis is nowhere near as rigid as the C7 design. If you can catch the "How It's Made" C7 Corvette episode on Velocity I think you'll be impressed with how far the assembly line process has progressed.
The C4 chassis is nowhere near as rigid as the C7 design. If you can catch the "How It's Made" C7 Corvette episode on Velocity I think you'll be impressed with how far the assembly line process has progressed.
Thread Starter
Burning Brakes
Joined: Jun 2014
Posts: 1,020
Likes: 51
From: Connecticut
With an additional 30 years of development and structural improvement the C7 should be easier to remove and have less of a body rigidity compromise when it's removed.
The C4 chassis is nowhere near as rigid as the C7 design. If you can catch the "How It's Made" C7 Corvette episode on Velocity I think you'll be impressed with how far the assembly line process has progressed.
The C4 chassis is nowhere near as rigid as the C7 design. If you can catch the "How It's Made" C7 Corvette episode on Velocity I think you'll be impressed with how far the assembly line process has progressed.
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Thread Starter
Burning Brakes
Joined: Jun 2014
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From: Connecticut
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The targa tops in the C3 generation also used pairs of latches. Two latches at the outer front and rear and two tabs that slid into slots on the "T" portion of the roof. These latches were very small compared to the C5 latches. They didn't provide any structural support so all the latches had to do was to keep the tops in place and keep rain out.
Thread Starter
Burning Brakes
Joined: Jun 2014
Posts: 1,020
Likes: 51
From: Connecticut
The C5 and C6 targa tops use latches; one at each front corner and a single latch at the rear center. But the C5 and C6 frame is much stiffer than the C4. In fact, the C5 frame was designed with the convertible in mind. The C6 frame is basically the same but with some added stiffness.
The targa tops in the C3 generation also used pairs of latches. Two latches at the outer front and rear and two tabs that slid into slots on the "T" portion of the roof. These latches were very small compared to the C5 latches. They didn't provide any structural support so all the latches had to do was to keep the tops in place and keep rain out.
The targa tops in the C3 generation also used pairs of latches. Two latches at the outer front and rear and two tabs that slid into slots on the "T" portion of the roof. These latches were very small compared to the C5 latches. They didn't provide any structural support so all the latches had to do was to keep the tops in place and keep rain out.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
Yup, they launched one from a Toyota Supra. I can only imagine that is what it would be like in a C6 Z06 or ZR1 when the roof delaminates and blows off.
Who else used a bolt on Targa? The C4 is my only real experience with a Targa and it's removal. I have seen the early Porsche 911's but never saw one while the targa was being removed. If I recall correctly, the those were folding canvas style tops.
I get the C4 top is part of the upper structure and needed for rigidity of the frame and the car was initially designed to have a T roof vice Targa. However, I just think a better design could have been made by the end of the C4 life span. Seems that the Targa design was really never revisited during the C4 lifespan.
I have no idea how the C5 or C6 Targa latches so I have no idea wen the bolts and "special tool" process were abandoned in favor of latches.
I can only imagine that is what it would be like in a C6 Z06 or ZR1 when the roof delaminates and blows off. Who else used a bolt on Targa? The C4 is my only real experience with a Targa and it's removal. I have seen the early Porsche 911's but never saw one while the targa was being removed. If I recall correctly, the those were folding canvas style tops.
I get the C4 top is part of the upper structure and needed for rigidity of the frame and the car was initially designed to have a T roof vice Targa. However, I just think a better design could have been made by the end of the C4 life span. Seems that the Targa design was really never revisited during the C4 lifespan.
I have no idea how the C5 or C6 Targa latches so I have no idea wen the bolts and "special tool" process were abandoned in favor of latches.
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The bolt down design was part of gm's safety worries. There is so much flex on a coupe with the targa top out that with it in and the lock design the convertible uses it would never hold.
Without an x brace like the convertible has the coupe flexes a bunch with the top out.
All the car companies during that time were using the threaded bolts too.
Without an x brace like the convertible has the coupe flexes a bunch with the top out.
All the car companies during that time were using the threaded bolts too.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
The reason is that the top is a structural part of the car. Latches aren't strong enough to perform that task.
EDIT, I see this was covered already.
Last edited by Tom400CFI; May 3, 2015 at 05:40 PM.
Team Owner
Joined: Aug 2004
Posts: 21,543
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From: Park City Utah
I get the C4 top is part of the upper structure and needed for rigidity of the frame and the car was initially designed to have a T roof vice Targa. However, I just think a better design could have been made by the end of the C4 life span. Seems that the Targa design was really never revisited during the C4 lifespan.
"The latches weren't able to transmit as much load into the hatch as the car wanted; they'd actually pop open.
So we had to go from the quick release latches to the bolt on roof. We measured the maximum load going through the latches and found it to be about half a ton."
^That is a lot of force...too much for a simple latch.