2011 MX5 Mod Options and their impact on Roadworthiness

Charlie Brown · Postby **Charlie Brown** » Mon Mar 02, 2015 4:19 pm

Regie wrote:When i ran 17x8 wheels i had 215-45's on them. They fitted quite nicely

Yep but if you were going to buy a set of 8" rims and your old tyres were shagged, you'd fit 225s.

jassi · Postby **jassi** » Mon Mar 02, 2015 5:04 pm

Regie - I think our NCs are the same colour, of course under the hood you've got way more going on :lol:

So if I went 215/45 on my current 17x7 rims then later I could easily upgrade to 17x8 and get the same 215/45 tyres on.

Charlie - won't 225/45r17 be too tall and need rolling fenders? 225/40 doesn't really exist as an option and then it's 235/40 where there are few choices but not many.

Dan · Postby **Dan** » Mon Mar 02, 2015 5:28 pm

It depends on the offset of the wheels, I recently ordered a set of Weds TC105n in 17x8 +49 after doing some research and it seems like people run these wheels in the states with 225/45 without rolling fenders.

If it was me if buy wheels and tyres at the same time and avoid any compromise. If you want to run keep both sets you can buy the new set up and hold onto them while you run the stock ones down and if you want to sell the stock ones just sell them with tyres on.. Saves some cash in not having to swap tyres on rims too.

jassi · Postby **jassi** » Tue Mar 03, 2015 12:29 pm

Dan wrote:If it was me if buy wheels and tyres at the same time and avoid any compromise. If you want to run keep both sets you can buy the new set up and hold onto them while you run the stock ones down and if you want to sell the stock ones just sell them with tyres on.. Saves some cash in not having to swap tyres on rims too.

Hey Dan - agree on that logic. WIll need to see how much I have left on my current tyres and then budget accordingly for the best path.

Arty · Postby **Arty** » Tue Mar 03, 2015 4:12 pm

Charlie Brown wrote:I think most of your questions have been answered but I’ll summarised it for you starting from the front and going to the rear.

POWER
AEM CAI – not worth the money, possible increase in power on a good day 0.5kW, can lead to bent rods when the engine ingests water due to the low intake position. The NC has a stock CAI.
GWR header – the best bang for the buck modification for the NC. Will add about 10kW. No it’s not legal, it deletes the first cat. You need to add another O2 sensor bung after the second cat and extend the O2 cables to fit either side of this cat. To make legal you need to fit another (read ‘bigger’) cat in the midpipe, which given the room, may be a problem.
GWR mid pipe – If you don’t have the header you’d be hard pressed to notice any difference in performance.
GWR muffler – a legal modification, good sound for a small gain in output, maybe 2 – 3kW.
You didn’t enquire about a tune. More power is to be gained here especially if you install the header.

WHEELS & TYRES
The stock rim is 17x7. 205x45x17 tyres are the stock size but the rim width also supports 215x45x17 tyres which are cheaper to buy. You can’t go wrong with the Michelin PS3’s at around $180ea. The stock rim is too narrow for 225 section tyres.
Maximum legal width is 8” and to maintain a legal track width you need to have a minimum 43mm offset. Also you need light rims, which restricts you to just a few brands.

UNDERBODY BRACES
Save your money for something else. They are on par with CAI’s.

SUSPENSION
The cornering ability of a stock NC improves dramatically with a set of adjustable sway bars. Probably should be the first modification you make.
Shocks - Save, save, save for the best you can afford. Do not buy cheap coil overs. You are far better off with a set of lowering springs and quality adjustable shocks rather than $1100 coil overs, especially for a daily drive. Remember to stay legal the car has to have a minimum underbody clearance of 100mm. It starts at 119mm and as most of the aftermarket springs have a 35mm drop you can see you may run into problems straight away.

You should also remember that some of what you read on the US sites may not apply to us here in AU. Tyres (not tires), rim widths, power output, gear ratios, diff ratios, model year, etc are just some of the things that are different. We don’t have Mazdaspeed equipment here so it’s not considered a legal Mazda extra when fitted.

If you need to find out more, join the VIC MX-5 Club and have a chat to the boys there who have done it all before.

What he said :mrgreen:

but "super-q" stands for super quiet :wink:

jassi · Postby **jassi** » Tue Mar 03, 2015 4:43 pm

^^ lets see. I hear super-q is around 15% louder than stock.

While I wait for my super-q to be delivered, I'm getting worried about the muffler flange and oem mid pipe flange not sealing well with gwr supplied flat gasket. There is a whole thread on it here http://forum.miata.net/vb/showthread.php?t=468164 Unsure if others with oem mid pipe and aftermarket mufflers had this issue!

Arty · Postby **Arty** » Tue Mar 03, 2015 5:45 pm

jassi wrote:^^ lets see. I hear super-q is around 15% louder than stock.

While I wait for my super-q to be delivered, I'm getting worried about the muffler flange and oem mid pipe flange not sealing well with gwr supplied flat gasket. There is a whole thread on it here http://forum.miata.net/vb/showthread.php?t=468164 Unsure if others with oem mid pipe and aftermarket mufflers had this issue!

Nothing to worry about, just buy a thicker gasket.I've got the Roadster II and the gasket supplied is for Goodwins mid pipe not oem but it's not a deal breaker so everyone with a stock mid pipe has this issue.

jassi · Postby **jassi** » Tue Mar 03, 2015 6:59 pm

Thanks good to know its well known and I'm hoping the guys at mx5 factory can address it. The thread I put the link to above advises to use the oem o-ring gasket and Permatex ultra copper silicone gasket maker. I don't want the muffler flange ears bent in case I want to go the gwr mid pipe and headers later

Charlie Brown · Postby **Charlie Brown** » Wed Mar 04, 2015 9:01 am

You're worrying about nothing. The flanges won't bend.

I fit and remove my muffler every track day, so once a month on average over the last 4 - 5 years and have only replaced the gasket once.

jassi · Postby **jassi** » Wed Mar 04, 2015 10:25 am

^^ thanks Charlie, won't bother too much about it then. By the way that's a lot of track days

Regie · Postby **Regie** » Wed Mar 04, 2015 12:23 pm

Phils car was the first nc to take to the track in Australia.

hks_kansei · Postby **hks_kansei** » Wed Mar 04, 2015 5:28 pm

It sounds like you've got the basics covered regarding legality in Vic.

Height can't be lower than 100mm from the lowest point (take into account things like exhausts etc that may hang lower than stock)

Exhaust can't be louder than 90db. From memory the measuring point is 3/4 redline (including the down-rev) and measured from 1m away. Removable silencing devices technically wont pass (if you show up for an EPA noise test with one they'll likely ask you to remove it.

Headers etc are ok if they;re designed for the car and retain any pollution stuff the car came with (EGR, cat)

Intakes are ok, no oiled filters allowed, I have heard that open filters won't pass, but havent been able to find it in the regs.

I've made a point of reading the regs in regard to my car, mine's not legal, but at least I know what parts aren't legal

jassi · Postby **jassi** » Wed Mar 04, 2015 7:40 pm

I've made a point of reading the regs in regard to my car, mine's not legal, but at least I know what parts aren't legal

So is it recommended to keep the oem parts at home, so in case they tell you to come for a road worthiness inspection, you can just get the stock stuff back on

hks_kansei · Postby **hks_kansei** » Wed Mar 04, 2015 8:17 pm

jassi wrote:
I've made a point of reading the regs in regard to my car, mine's not legal, but at least I know what parts aren't legal

So is it recommended to keep the oem parts at home, so in case they tell you to come for a road worthiness inspection, you can just get the stock stuff back on

Very much so.

While it sounds like your choices will all be legal anyway, for some of the ones that may be looked at (mainly suspension height, and exhaust volume) it's a good idea to keep them anyway.

There is a fair degree of discretion as to if an officer wants you to go to Vicroads and have things checked, and the discretion isn't always perfect (in saying that, usually they are pretty good unless you've done something stupid like speeding or wheelspins etc)

jassi · Postby **jassi** » Thu Mar 05, 2015 8:49 am

taminga16 wrote:Start with a good front/ rear alignment
Greg.

Hey Greg - i currently get servicing done from a mazda dealer and they claim to do some wheel balancing (and i believe alignment) on my 6 monthly services. Should i go to someone else and/or ask for a specific alignment? I have researched a lot on specific alignments for stock nc2 prht but mostly people are talking about alignments for lowered or wider tyres. Any thoughts on this? Also I know my mx5 needs an alignment when I change rims/tyres but does it need an alignment after i do sway bars (guess not)?
lastly what are the thoughts on dealer servicing vs an mx5 specialist doing it (also given I be will be doing some mods)?

hks_kansei - thanks for the recommendation, will make sure I retain the oem parts being replaced with mods!