Top speed higher with roof down or up?

[KRAMSNEHPETS]

Thoughts and experience please

[Topdownman]

No experience as such but I would imagine the top up would have better airflow and reduced turbulence and therefore higher potential top speed.

[lamcote]

Whenever I have seen both top speeds quoted for convertible cars the roof down speed has always been lower than roof up.

[KRAMSNEHPETS]

Roof up when I am next on the autobahn

[ChrisGB]

What sort of top speed are you geared for? I've always been paranoid that the roof could pop open at really high speed. Remember, the top was only designed to go to 130 or so, with your power, you could be going a lot faster that that.

[lamcote]

The man has a point!

[KRAMSNEHPETS]

Didn't think of that, would be a massive air brake! Has for face lift 6th gear that lets it sit at 90mph at 4000 rpm. Don't think the gear will  limit top end. My hood is very tight to latch it shut so I think it would be ok. What autobahn top end have you done Chris?

[MilesH]

We tried a hard top on and off test on the roll caged race car and the hard top on terminal speeds were quicker.

[MilesH]

Double post oops!

[ChrisGB]

Didn't think of that, would be a massive air brake! Has for face lift 6th gear that lets it sit at 90mph at 4000 rpm. Don't think the gear will  limit top end. My hood is very tight to latch it shut so I think it would be ok. What autobahn top end have you done Chris?

I think that if it did pop open, the roof would be decimated. It would certainly get your attention  s:shock: :shock: s:shock:   I haven't maxed it out on the new gearbox with the longer diff ratio, but on the old one it pulled strongly past the end of the speedo and into the rev limiter at around 150. I'd be intrigued to know if it would pull to the rev limiter now, that would be about 175mph. Other things to consider are stuff like the front bumper and arch liners, which could bend extensively at the speeds that 300+ Bhp can enable.

I need to find somewhere to max it out sometime.

[KRAMSNEHPETS]

I need to look at my front bumper, Front splitter has sorted out  the car feeling very light above 100 but the bumper seems to have dropped away from bonnet and head lights a bit...

[Topdownman]

I did have a period when one of my roof catches would suddenly decide to pop open at, ahem, motorway speed occasionally. Very scary! Cant imagine what that would be like at autobahn speed.

Hasnt happened since I tightened up the catches I am glad to say.

[ChrisGB]

I need to look at my front bumper, Front splitter has sorted out  the car feeling very light above 100 but the bumper seems to have dropped away from bonnet and head lights a bit...

The point where the bumper meets the wheel arches stretches a bit too.

[delhusband]

I did have a period when one of my roof catches would suddenly decide to pop open at, ahem, motorway speed occasionally. Very scary! Cant imagine what that would be like at autobahn speed.

Hasnt happened since I tightened up the catches I am glad to say.

Wonder if it would be like Mark Webber's '99 le mans experience?   s:shock: :shock: s:shock:

[lgriffiths]

Roof down would be massive amounts of drag.

Unless you sealed the cabin around you with some kind of skirting and took the windscreen off & pillars off...

[BahnStormer]

Unless you sealed the cabin around you with some kind of skirting and took the windscreen off & pillars off...

you honestly want to give these nutters any more ideas!!!   s:scared: :scared: s:scared:  
(guys if/when you remove the A pillars and windscreen to test this theory, please make sure you get pics!)

Didn't think of that, would be a massive air brake!

I think I can safely say that at >100mph an extending roof probably wouldn't stick around for very long, unless you've reinforced it! The only question would be how much it would destabilise the car while it was in action... I don't think the car was designed with a top-mounted drag parachute in mind.

[KRAMSNEHPETS]

Might go to the autobahn sunday with the roof up!

[m1tch]

#hardtoplife  s:D s:D