Roof up vs. Roof down..

[JonnyFive]

No, this isn't about you pussies with hardtops

Does roof up compared to roof down make a difference to speed? And if so, is it alot?

[tuttle]

Possibly a couple of mph off the top speed but not for normal hooning about.

[JonnyFive]

Ah right, thanks!

[hornetrider]

Offset by lower CofG with the roof down. Make sure you open your glovebox too in order to get weight even lower.

[JonnyFive]

hornetrider said:

Offset by lower CofG with the roof down. Make sure you open your glovebox too in order to get weight even lower.

Oh really? Hmm.. What about with tonnau cover on?

Will the aerodynamics out weigh the weight difference?

[beeblebrox]

I keep my spare wheel in the passenger footwell to get the CofG even lower. Seems to make quite a difference.

[Ben3883]

Hard top on: 35mpg, 50% smiles/mile, stereo quality 10/10

Poof-roof up: 33mpg, zero smiles/mile, stereo quality 6/10

No roof: 30mpg, 100% smiles/mile, what stereo? Increased suntan, much happiness.

[mk1salami]

It does make a difference. In my scientific tests (ahem ), I consistently ran a best time of 13.2s quarter mile with the roof down (repeated about 5 times). With the roof back up I nudged into the 12's (12.96s). So it's worth ~0.2s over a quarter mile finishing at ~110mph.

The difference gets even bigger with less power to cut through the air.

[mk1salami]

hornetrider said:

Offset by lower CofG with the roof down. Make sure you open your glovebox too in order to get weight even lower.

[piefacemate]

So what, if anything, could be done to offset the aerodynamic inefficiency of having the roof down?

Obviously windbreakers aren't allowed cause they're gay.

[Mr MXT]

Slightly OT but it made more of a difference in my S2000 than I'd have thought.

156 roof up, 145 roof down.

The MXT is 113 whatever, roof up or down

[JonnyFive]

Mr MXT said:

Slightly OT but it made more of a difference in my S2000 than I'd have thought.

156 roof up, 145 roof down.

The MXT is 113 whatever, roof up or down

You see, I was on a run this weekend and had 132 indicated but 125 on gps.. And wondered if it'd be different if I had the top up.

[piefacemate]

Mr MXT said:

Slightly OT but it made more of a difference in my S2000 than I'd have thought.

156 roof up, 145 roof down.

The MXT is 113 whatever, roof up or down

You not disabled the speed limiter yet? Even my aging one can just about crack 140. Essential for when Nobles overtake on the M60.

[Mr MXT]

I don't know how to disable an NB

[piefacemate]

Ahh, forgot yours was a later one. Guessing it's not the screw in the back of the speedo jobby then. Someone more knowledgeable than I will no doubt be along in a minute...

[trackerjack]

Though I own an MX5 I have not tried to find out but reckon Ben is correct.
When I used to speed everywhere and owned a TR5 (1980) I found that the car would do 125 mph with the roof up and about 118 mph with it down, I also used to sprint and hillclimb in those days and my best roof up sprint lap was 1 min 49 sec but a lowly 1 min 54 with no roof.
However I reckon roof down unless its really pouring down with water is best.

MX5's do not buffet you much neither does my Quantum Turbo 2+2 but the TR did,so I deduce its also much to do with aerodynamics.

[AmiableChimp]

I shave my head to reduce drag when the roof is down - good for an additional 2mph!


(May not be strictly true).

[MX-5 Lazza]

AmiableChimp said:

I shave my head to reduce drag when the roof is down - good for an additional 2mph!


(May not be strictly true).

That would also help lower the CoG

[The Hypno-Toad]

A wooly hat increases drag.

A leather flying helmet just makes you look like a dick.

A baseball cap acts like a splitter and increases downforce around the centre of pressure.

A baseball cap round the wrong way just makes you look like a massive dick.

[AmiableChimp]

The Hypno-Toad said:

A wooly hat increases drag.

A leather flying helmet just makes you look like a dick.

A baseball cap acts like a splitter and increases downforce around the centre of pressure.

A baseball cap round the wrong way just makes you look like a massive dick.

What about a leather flying helmet round the wrong way?