Model: MX5 MK1 1.6.
Query: Anti roll bar options to reduce (you guessed it) roll
Hello dear reader,
I’m looking for options on upgrades of the stock MX5 MK1 anti roll bars.
The car is already fitted with lower stiffer coilovers but the body roll for its use case is still too much.
I’m already aware you can get aftermarket roll bars around £300-£500 but I’m finding it hard to part with the money for what is basically slightly stiffer piece of metal.
Does anyone know of any alternate options from other mx5s/rx8/mazdas that can be fitted/modified to suit? (e.g. like how the mk2.5 sport brakes can be fitted to mk1s).
Front ARBs are all 19mm, except for 1.8 Eunos Roadster S-Specials (and derivatives), which had a 20mm bar. To fit a 1.8 front ARB on a 1.6, you need to drill a hole in the ARB for the droplink, closer to where the bar bends. By comparison, an Eibach front ARB is 24mm thick.
All rear ARBs are 12mm, except 1.6 Eunos Roadster S-Specials, which dropped down to 11mm, to dial in understeer. Too thick a rear ARB might might the car an oversteery monster.
Putting on too thick a set of bars will flatten cornering, but at the expense of increasing spin.
Its not as simple as just throwing on some scrapyard ARBs that happen to fit. The wrong combination of ARBs will very likely ruin the handling of the car.
You say you have fitted “stiffer” lowring kit, what’s the spring weight front/rear and have you maintained a 60% rear spring bias? There are some rubbish lowering kits out there.
Sounds like there’s probably not much between other similar alternatives for bars from Mazda. I’m guessing the best bet is to grab a set that can be adjusted and turn it up and down until it spins just enough.
The front coilover spring stiffness is 9kg/mm and the rear 7kg/mm - so like a 56/44 front to rear?
I had a car with FM bars. Couldn’t tell you if they were any better than others. They’re just lumps of iron. There are 3 adjustment holes, so “tuning” is crude. But then you will also need adjustable drop links/
I could tell you what happened to a club member, ex-police driver. He had a lovely late Mk1, lowered it, but wanted to reduce roll, so he made the mistake of giving Moss a call. They enthusiastically recommended Jackson Racing tubular ARBs; tubular bars are stiffer than solid bars.
Fitted them up and promptly stuffed the car down his favourite lane. He was on 14s. Normally, the tyres would give some aural warning if you are pressing on too hard. This time they didn’t and he was able to corner until the bread broke…
You have 504/392 lb springs? So not road use then. Not sure why you chose that set up, without also thinking you will need other changes as well.
And read loads of threads on miataforum. I think you need to be thinking a bit more deeply than just wanting to “eliminate” roll, because roll can be your friend.
So with your setup, of very stiff springs and standard ARBs, you’ve actually ended up dropping the front roll couple, making the car oversteery and “loose”. The rear springs seem too stiff. Putting on a thicker front ARB won’t do much for the FRC. For the track, you want FRC of about 63-65%. A stiffer rear ARB will make it worse. Actually, throwing on an 11mm bar off a 1.6 S-Special makes quite a difference; almost the same FRC as standard, but still oversteery. Add a 20mm front bar from a 1.8 S-Special gets you even closer to standard FRC.
Whiteline bars are probably some of the cheaper ones; a 24mm front adjustable is about £200, and that will put you over 60% FRC with the 12mm rear bar.