Oversteer: FM Stage 2 V-Maxx kit + turbo

[zossy1]

Hi guys,

As most of you know, my car is now turbocharged and has far more power than it used to. It hasn't been dynoed but I would estimate around 200whp and very fast spool.

Power oversteer was always going to be a risk, but I am of the view that the car really is far too tail-happy for its own good right now. I think it may have something to do with the FM rear swaybar.

The stage 2 kit beefed up both the front and rear sway bars. However, the rear bar, proportionally speaking, much more so. The overall roll centre of the car therefore has probably shifted forward a bit...? When getting on the power, it sure feels that way. There is no hint understeer, just bucketloads of drift and wheelspin - especially off slow corners when getting on the power a bit early.

I was thinking about going back to the OEM rear bar and giving it a try. Has anyone ever given this a go? Any thoughts?

My tyres are not so great - fairly new (but mediocre quality) Achilles 195/50/15 on 15x8 +25 wheels. These will be changed to KU31 in the near future but I'm not sure if this will improve balance (although I suspect the rear grip will still be improved with the KU31).

Alignment is per FM specs, although I am running around 0.5 degree more neg camber on each of the rear wheels owing to the low ride height of the car. This may also have something to do with it...

I will also be installing FM chassis rails in the coming days but not sure if that will make things any better.

[Dweezle]

I too am very interested in this.

With the Silver NA, my brother is just running a Racing beat front bar with stock rear.
It seems to have neutralised it a great deal.
Almost to the point of understeer.

But this is pretty stock power wise.

[93_Clubman]

I was thinking about going back to the OEM rear bar and giving it a try. Has anyone ever given this a go? Any thoughts?

Yeah, a number revert to OEM, & even no bar in some cases depending on use. Not sure what you're running, but some options might be stock NA8: 11mm, stock NA6: 12mm, & MazdaSpeed (red): 14mm.

[BadBong]

Agree that you should give a thinner rear bar a try.

PM Boyracer if you're looking for a SE rear bar. He's parting a whole SE out atm.

[deviant]

My first NA turbo was the same, really really drifty...great fun but not at all quick. I sure as heck learnt a lot about car control though but even at high speed it could still happen. Be warned!

The race car was the opposite, bags and bags of grip. This was partly down to running semi-slicks but also in the set up. FM alignment specs, NO rear bar, front 24mm whiteline bar set to softest. Tein coilovers were full soft on the rear and only 8 or 9 clicks from soft on the front.

I know the new owner of my first car is still struggling with it a bit. There is no rear bar and a set of very soft coilovers with a low spring rate also set to full soft and it is still pretty taily.

I cringe when I see the spring rates some manufacturers choose for MX5 coilovers.

[Muzdaman]

What spring rates are you running?

[zossy1]

According to the FM website:

The secondary springs are 112 lb/in, which gives them enough strength to overcome the damping of the shock. On most cars, they are just barely fully compressed at rest. The primary rates are 391 lb/in in the front and 258 lb/in in the rear, which gives a good handling balance.

[Muzdaman]

Its easiest to try no rear bar first, just disconnect an end link and see what difference that makes.

[Charlie Brown]

According to the FM website:

The secondary springs are 112 lb/in, which gives them enough strength to overcome the damping of the shock. On most cars, they are just barely fully compressed at rest. The primary rates are 391 lb/in in the front and 258 lb/in in the rear, which gives a good handling balance.

I haven't looked at the FM site but I'd say the secondary springs are just helper springs.

As everyone has said, loose the rear bar or go as light as possible.

Next a decent set of tyres. Performance tyres not KU31, Achilles, etc etc. It's far cheaper to buy a good set of tyres than be up for a repair bill when the rears let go and your car and maybe someone else's gets bent.

[MINX]

Next a decent set of tyres. Performance tyres not KU31, Achilles, etc etc. It's far cheaper to buy a good set of tyres than be up for a repair bill when the rears let go and your car and maybe someone else's gets bent.

Plus 1

The false economy of, well, economy tyres, is so obvious once you start using good quality tyres.
You can mess with coilovers, dampers and sways all you like, but if you have cheap nasty, or old hard tyres, you are fighting a losing battle.

So many on this forum seem to push the low end tyres.
I have made the mistake of basing tyre purchases on price, and been very dissapointed.
Poor tyre choice can easily ruin an MX5

[Dweezle]

Next a decent set of tyres. Performance tyres not KU31, Achilles, etc etc. It's far cheaper to buy a good set of tyres than be up for a repair bill when the rears let go and your car and maybe someone else's gets bent.

Plus 1

The false economy of, well, economy tyres, is so obvious once you start using good quality tyres.
You can mess with coilovers, dampers and sways all you like, but if you have cheap nasty, or old hard tyres, you are fighting a losing battle.

So many on this forum seem to push the low end tyres.
I have made the mistake of basing tyre purchases on price, and been very dissapointed.
Poor tyre choice can easily ruin an MX5

In what way are KU31's Economy tyres??

[zossy1]

Price isn't a huge deal for me, an neither is tyre life as the car is not my daily.

Star Specs? Something else? I am thinking about moving up to 205/50/15 on the 8 inch wheels...

[deviant]

In what way are KU31's Economy tyres??

A good clue to just how much of a performer a tyre is is to look at the UTQG rating: http://www.tirerack.com/tires/tiretech/ ... ?techid=48

KU31 is more of an acceptable performer for the road than a true high performance tyre.

[deviant]

Next a decent set of tyres. Performance tyres not KU31, Achilles, etc etc. It's far cheaper to buy a good set of tyres than be up for a repair bill when the rears let go and your car and maybe someone else's gets bent.

Plus 1

The false economy of, well, economy tyres, is so obvious once you start using good quality tyres.
You can mess with coilovers, dampers and sways all you like, but if you have cheap nasty, or old hard tyres, you are fighting a losing battle.

So many on this forum seem to push the low end tyres.
I have made the mistake of basing tyre purchases on price, and been very dissapointed.
Poor tyre choice can easily ruin an MX5

It is bloody dangerous to, I hate going on car forums and seeing people harp on about how awesome a piece of equipment is. Not everyone has awesome driving skills or a car that is even set up the same.
I fairly got shot down on here for suggesting that the Bridgestone RE001 that a lot of people push is actually not the tyre a lot of people say it is. Many posters jump up and down "OMG I can totally take corners 20KMH faster and my circuit times are better"....MAYBE for their car with their driving skills okay. When I used them on track on my turbo NA they were just completely hopeless.

In what way are KU31's Economy tyres??

A good clue to just how much of a performer a tyre is is to look at the UTQG rating: http://www.tirerack.com/tires/tiretech/ ... ?techid=48

KU31 is more of an acceptable performer for the road than a true high performance tyre.

[red devil]

the never ending battle for grip!

would changing you diff ratio help? I have a 3.9 in my car, sure the acceleration is not what it used to be, but neither is my arse hanging out around corners or off the lights when its raining

Eren