Shurshot

All the renewed interest here over the GS models that are currently available from kit to turn key got me thinking about possibly building a roadster GS

Seems to me that the roadsters are pretty rare and just for convenience sake and weather related protection I can see why.

Maybe because I never have had a roadster or possibly because I have had a midyear coupe for many years I think having a roadster might be nice.

So for those here who are familiar with the pros and cons beyond the obvious of staying dry or having AC in the coupe what other concerns do the roadsters present? Are these cars like the early Cobras when it took the coupe to allow even experienced drivers to remain confident at high speeds?

Do the C4 suspension kits currently employed with the GS kits negate this or is there an inherent airflow problem that the roadster cannot overcome?

Is there a high speed handling limit to the roadsters that the coupe overcomes and if so what is the MPH difference in stability and tracking between the two models ?

Thanks in advance

Doug

Procrastination Racing

In the case of the regular '63 coupe/convertible, there were some pros and cons. While the real GS cars had some changes to remove or reduce these effects, some were bound to remain. In the cases of the reproductions, I would think some of these are still present although many have had modern changes to fix these issues.

1. Lift - both coupes and convertibles have a lot of lift in the front but the coupe also had lift in the back. Phil Currin and I were discussing this once and he mentioned how his '63 IMSA coupe would lift so much the rear wheels would lose traction around 140 to 150. This was before the rear spoilers allowed in GT racing by SCCA and GTO in IMSA.

However, without any spoilers, you have a good chance of getting airborne in the 150 mph range. At Daytona, with about 6 inches of full width spoiler, my '66 convertible wanted to leave the ground around 170 and you have to remember the 32 degree banking tries to plant you into the pavement. 10 inches held it to 190 but the tail was light.

2. Drag - both have a lot with a blunt nose but the higher roof is more drag, regardless of the streamline shape. The taller of two cars with equal width will have a larger frontal area and this will go to higher drag. It is a mathematically equation; calculate it.

3. Weight - in stock trim, the coupes were heavier, however, in race trim, they could be made the same. For the real GS, I haven't seen accurate data. They have a lot of figures but they always seem to be in different configurations so you couldn't really compare.

4. Chassis flex - while most think the convertible is more flexible and would be the worse of the two, a lot of the handling chassis flex is from the firewall forward which is common on both.

Check with Jim Lockwood. I believe he has run with Phil Currin out at some of the vintage events in CA and since he runs a pair of Grand Sports, will have a lot of what you are looking for.

Shurshot

Thanks for your reply

Well I just learned something new. I would not have thought that the coupe body presented airflow problems...... I have been exposed to the front end lift at over 125 and figure that would not be hard to overcome with a front spoiler

I am not sure what speeds are necessary to obtain in class racing with whatever class an old GS style body on a newer C4 frame would fall into but hopefully 150 would be fast enough.

That is probably pretty close to the limit where I would still be comfortable. Ten years ago I had an Impala set up that I was happy to take to 170 plus but now for some reason that seems little to fast. :o

Doug