I've seen for a long time, since about patch P, that UF and LX roofs no more affect physics. UF roof no more adds weight and no more improves aero. I think this must have been explained, but I don't know where to search. What was the reason? Actually, I've asked Scawen online at balancetesting, but I couldn't comprehend the response.

Because having an option to go slower isn't a very exciting feature.

Only the UF1 was once affected for speed with the top being placed on and off. But Scawen figured it was used more as a cosmetic preference to the car, and some people prefered to use the UF1 with the top ON... though that would make them slower through corners because of the added weight.

Surely it was realistic, but for now, I think it is best to keep the car with the option of having it on and off, because quite frankly, the top being OFF is just a bit of humour added to the game, and other drivers like myself don't want to drive a stupid looking convertible UF1 on the track just because it is faster with low weight... I like a hardtop UF1 to be honest. That's the reason why it is unaffected.

What I do know is, having the tops on or off in the UF1 and LX's affects the loudness of the wind buffeting when you drive

Having the roof up improved aerodynamics without a weight penalty, so everyone in the know used it. Nobody races Caterhams IRL with the roof up so, while realisitic, it wasn't having realistic uses.

Ditto with the UF1, most tracks that the UF1 is raced at are slow, so everyone raced with the open roof guise to save weight at the expense of increases drag. You don't race open roof cars IRL, besdies the open roof version should have been heavier if different at all.

With the UF1000, maybe the fact that body flex is not modelled in LFS makes it impossible to have realistic variation between hard top and convertible anyway. So it makes sense just to have it as a cosmetic only choice.
(these being stock road cars, hard top version would be more rigid, so handling would be better and setups easier to fine tune)

I thought the UF1 had a removeable hard top? Maybe the rollbar should be visible inside with the hard top on? Just a thought.

Quote from wheel4hummer :

I thought the UF1 had a removeable hard top? Maybe the rollbar should be visible inside with the hard top on? Just a thought.

The UF1 is based on a Mini, the convertible is simply a crude removal of the roof. Due to body flex you'd never ever even consider racing an open top Mini, you'd actually get weight gain due to the amount of reinforcing work that would have to be done to stop the thing folding in on itself.

You can always use the Handicap option to add 20 or 30 kg and simulate the tops weight...

Quote from ajp71 :

The UF1 is based on a Mini, the convertible is simply a crude removal of the roof. Due to body flex you'd never ever even consider racing an open top Mini, you'd actually get weight gain due to the amount of reinforcing work that would have to be done to stop the thing folding in on itself.

As the Top Gear guys would say, it would need tonnes of oak trees and girders to keep it from going floppy

Maybe when body flex is implemented it will have an effect...

Actually, I've found this very strange also. It was really fun, choosing between top speed and lightness of the car. Sure, maybe it wasn't simulated correctly, but there always will be some tiny things, that will be unrealistic. Perfect realism is unreachable, we have reality for that