Racing with a hardtop vs roofless

[CrazyRacer]

I was wondering what most peoples thoughts were racing an MX5 with a hardtop vs roofless.

I'm looking to get a roll cage built in the NB soon and was wondering whether to try and squeeze myself under a hardtop or just go roofless and get a taller wider cage installed.

Eventual goal will be to do QLD ProdSports, probably 2B. I notice that a few cars do run a hardtop, but most seem not to (and a couple have removed the windscreen as well) and have rollcages that would exclude the possibility of fitting a hardtop.

The the issues that I can think of

Hardtop Pros

• better aerodynamics
• convenience of not getting soaked when it rains or fried to a crisp when it doesn't

Roofless Pros

• weight saving
• safer rollcage, taller and wider with more head room

[Magpie]

In the alternative what about a carbon fibre hard top with a Perspex window. Probably about 6 kg.

Danny Irvine posted some information a while ago showing that a hard top does add some rigidity.

[manga_blue]

I logged my car at almost 10kmh slower up the back straight at Sandown with the soft top down compared to top up. A friend was more than 10 sec slower around Philip Island with top down in a stockish NA6.

In the worst case a soft top and closed windows keep your arms safe in a rollover.

[CrazyRacer]

In the alternative what about a carbon fibre hard top with a Perspex window. Probably about 6 kg.

That would partially offset the weight penalty, but not really help with the head room unless there are ones with a different profile. Not sure that a carbon top would be in budget at the moment anyway, but in the future maybe. I have a factory top I can use which will cost me nothing but it is a bit weighty.

Danny Irvine posted some information a while ago showing that a hard top does add some rigidity.

Even on a car with a weld in cage?

[Trackphotos]

Ah, something I can weigh in on. I once did a back to back comparison, hard top vs no top at lakeside, same air temp, literally one session apart. The difference being a 20-25kg weight loss on the top-down session. I measured 7 tenths of a second loss on the roof-down runs, then immediately gained those same 7 tenths when I put the roof back on in the next session. A scant 2.4km track, Lakeside is heavily dependent on maintaining corner speed for low powered cars, the full throttle sections of track make up about 85% of a lap and every little bit counts. All that being said, for door to door racing, a cage is more important if the options are faster with only a rollbar or slower with a full cage. I'm lacking the will to spend anything on my car for racing anymore, but if I were already resigned to spending more, I'd ditch the lid in favour of a full cage. I run the mx5/86 challenge, so you and I may end up next to each other at some point at lakeside and/or qr.

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[CrazyRacer]

I logged my car at almost 10kmh slower up the back straight at Sandown with the soft top down compared to top up.

Sandown is a big power circuit, so I can believe that.

A friend was more than 10 sec slower around Philip Island with top down in a stockish NA6.

10 sec is a lot to lose around PI, which is probably equal parts about handling and power. But I suppose even a small amount of extra drag would account for a big percentage of your power in a stock NA6.

I'm not familiar with the QLD tracks though, having just moved here from Vic, so I haven't got a good handle on how much affect a bit of extra drag will have.

[rascal]

You can still fit a full cage under a hardtop.
If you are struggling for room then i’d be lowering the seat before i’d ditch the top..

IMO the advantages outweighs the disadvantages.

[CrazyRacer]

Thanks Trackphotos. Just the kind of feedback I was looking for.

The car is a turbo, so it might lessen the loss from the drag a little...maybe???

I am leaning towards the lidless option so I can go for a better cage, but thought I'd seek some feedback from others with experience.

I'm mounting a new seat at the moment trying to get it as low as possible to see just how much headroom I can get with the top on, but I think its going to be a squeeze.

I'm guessing that the weather isn't such problem here, as even when it does rain its usually not that cold. From past experience, going lidless at Phillip Island would be diabolical as you've got about a 95% chance of getting drenched in at least one session over the course of any weekend, and then the icy blasts off Bass Straight, straight from Antarctica, will give you frostbite. They're bad enough when you're not wet.

Hoping I can get the car out later in the year, so maybe we will end up next to each other. Before that though I'll come and check out the racing anyway, so I'll try and find you.

[CrazyRacer]

You can still fit a full cage under a hardtop.
If you are struggling for room then i’d be lowering the seat before i’d ditch the top..
IMO the advantages outweighs the disadvantages.

Yep doing that at the moment.

Bought a lower profile glass seat, cut out the rear seat mounts (gives me about another 8mm of clearance) and going to bolt the side mount seat brackets straight to the floor (without runners of course).

Hoping to get that done this weekend and then I'll have proper idea about the clearance. But with the Brown Davis roll bar currently in it which is hard up against the top, I don't think I'll have enough, even with the seat cushioning removed. I know there are some bars that mount further forward (like the AGI) that are a little higher, but I need the leg room too.

Trying my hardest to make a hardtop possible, but suspecting it wont be. Time will tell.

Hmmm, maybe MX5s aren't the best cars for even moderately tall people. Oh well, too late now.

[StillIC]

Hmmm, maybe MX5s aren't the best cars for even moderately tall people. Oh well, too late now.

I have been saying that for 9 years now, and I am still trying to get my seating position lower.

[Trackphotos]

Thanks Trackphotos. Just the kind of feedback I was looking for....
...
...Hoping I can get the car out later in the year, so maybe we will end up next to each other. Before that though I'll come and check out the racing anyway, so I'll try and find you.

I'd say a few extra killerwasps should lessen the need for slipperiness a fair amount, but that's just a guess; I'm still running stock power after 4 years of sprints and 2 years of occasional racing.

The pscraq are hosting three mx5/86 challenge rounds this year, they're basically an entry level round to introduce sprinters like myself to door-to-door racing in a safe manner with only marginal speed differences between entrants. This year there will be two lakeside rounds and one qr round, which gives us one extra lakeside round over previous years. I plan to run all three, and we generally get 20+ entrants per event so there will be a lot of people to question ahead of your own racing endeavours if you feel the need. They're a fantastic way to get started if you've never raced before.

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[Nuddy]

Get the best roll cage you can then build a custom soft top to go over it. You dont need a rear window.

[CrazyRacer]

Not a total newbie to racing. I raced a Datsun 1600 in 2 litre sport sedans in Victoria on and off for several years . But I'm going to be pretty rusty as I haven't been on a race track for about 15 years and have never dríven on any of the Queensland tracks.

I'd better do a few sprints to start with to learn the tracks and develop the car.

[Magpie]

http://mx5cartalk.com/forum/viewtopic.php?p=900897#p900897This is when Jamie and I made custom brackets as Jamie needed his seat much lower (due to his height).

If you have a harness installed then the lower eye bolt location may prevent you from getting the seat far enough back.

I plan to run all three, and we generally get 20+ entrants per event so there will be a lot of people to question ahead of your own racing endeavours if you feel the need. They're a fantastic way to get started if you've never raced before.

Hopefully will be there with you for at least one of these events.

[CrazyRacer]

http://mx5cartalk.com/forum/viewtopic.php?p=900897#p900897This is when Jamie and I made custom brackets as Jamie needed his seat much lower (due to his height).

If you have a harness installed then the lower eye bolt location may prevent you from getting the seat far enough back.

Thanks Magpie. I'd actually looked at your seat install pics before to get some inspiration. I'm trying to get the seat even lower and further back than that, which I think is possible but its a bit of work.

I originally was trying to put a Cobra Monaco seat in which is pretty similar to the Sparco Sprint, but it was just too high in the base. But recently I picked up a second hand Cobra Evolution (Standard) which looks like being a brilliant seat for an MX5. Its quite narrow in the base (so it doesn't foul on the harness eyelets), but still fits my not so narrow butt in it. My shoulders would have preferred the wider GT version of the seat, but that wouldn't have fitted the head/shoulder wings inside the car. You can also get variable height padding for them, or remove the seat base padding all together so you really can get as low as is possible.