MX5/Miata Thread

MX5/Miata Thread


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Reposted from my own thread:

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For 400 pounds you get a roof, two more seats, and a lot more power :p

BlaRo, I just realized your roll bar matches your stripe color, that is actually quite awesome.
 
Have a roof (which also comes down! Imagine that!), don't want, and don't want. I could get a lot more power for a lot less than 400 pounds, if I wanted it!

And that's for only around 250 to 350hp. If I was willing to spend the money and the 200 pounds or so, I could get 500+hp.

Now, if you could take away 400 pounds without taking away any of the safety or ability, and without increasing costs, I'd be interested. The costs are the only thing keeping me out of an Exige.
 
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Now, if you could take away 400 pounds without taking away any of the safety or ability, and without increasing costs, I'd be interested. The costs are the only thing keeping me out of an Exige.



:p

(given some wiggle room on your weight, safety/ability, and cost requirements)
 
That takes away ability, sorry. :( I've competed with MR2 Spyders - they're in the same class as my NC. The Spyders were built to the limit of the class, while mine was far from it. Even so, the Spyders weren't competitive with the NC.

They're great cars, and welcome competition, but they're more competition for the NB than the NC.
 
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What were their strengths and weaknesses?
 
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~1,600 pounds. With its late '50s chassis, anemic engine, and rear leaf springs it is unmatched by today's cars. :p
 
What were their strengths and weaknesses?
A lack of tire was a big hindrance for the Spyders (and for the NAs and NBs, once the NC came along). The NC can fit either 275 or 285 (depending on the wheel:sidewall preference), while the others can maybe fit 255 while staying within the class rules. My car had coilovers, a lightweight flywheel, and a lighter exhaust (saved maybe 20 pounds), and the fat tires on light wheels in a class that allows changing seats, changing steering wheel, chassis bracing, swaybars, full intake and exhaust swaps, tuning, and more. The acceleration of the Spyders wasn't far behind that of the NC, but they couldn't maintain as much speed in the corners and they couldn't brake as effectively.

My car was about 180 crank hp with about 2500 pounds. A fully prepped NC would be 200 crank hp with about 2300 pounds.

The NC has fantastic brakes - the balance is wonderful and the ABS is absolutely perfect for competition. The ABS will allow the tire to reach its threshold of grip and slip just a little bit, and only interferes if the wheel is actually locking up. It can activate on only one wheel at a time, too, adjusting for brake bias issues that happen while cornering. I'm not sufficiently familiar with the Spyder's brakes to know how they compare, but the NC sets the standard high.

And the fat Hoosiers make it seem like the car can break the laws of physics in a corner. The NC's chassis is stiff for a convertible, and add in the huge grip from the Hoosiers and stiffer springs that can use the stiff chassis and huge grip, and it'll go through corners literally 20mph faster than it does on 225 width streets (a corner where my minimum speed is 40mph on the streets, the car will do at 60mph on fat Hoosiers).

The fat tires are an autocross specific setup, and slow the car down on road courses. On road courses, 225 is about as wide as a naturally aspirated NC should go (barring an engine swap). Fatter and acceleration is badly impacted over about 65 to 70mph.

~1,600 pounds. With its late '50s chassis, anemic engine, and rear leaf springs it is unmatched by today's cars. :p
GrandPa class (GP) is calling!
 
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I'm posting this here, because I realize a lot of you (MX-5 owners) do at least a little bit of autocrossing, or actual racing.

Has anyone installed a rear UPPER chassis brace on their car? One that goes in the trunk and connects the upper shock mounts. And if so - have you noticed any benefit/improvement from it?

I want to stiffen up my car's rear end (not a Miata...), a lot of people say that bigger swaybars are the way to go, but they are a bit costly. I found that rear upper braces go for under $100, and was wondering if there is any point of trying one?

There is a fundamental difference in the function of the anti-roll bar (sway bar) and chassis brace. Chassis brace prevents unwanted movement of the chassis, rear damper in this case. If the shocks move, it might cause less accurate damping.

I'm pretty sure the S70 doesn't have struts at the back (= MacPherson style suspension at the back), but a multilink setup or something similar. I might be wrong, I've never done any work with those. So the rear end should be pretty rigid and there shouldn't be any real value gained with chassis brace.

If you want your car to understeer less it's a good idea to fit harder anti-roll bar to the rear. Cars roll is controlled by front and rear anti-roll bars and their relationship can be used to fine tune understeer/oversteer balance. So if you now fit harder rear anti-roll bar and the car becomes more neutral. Then if you next month buy similarly harder anti-roll bar to the front also, your car will maybe roll less, but the balance is once again like it was in the beginning.

So actually by fitting harder anti-roll bar you move part of the load caused by weight transfer to that very axel. Because grip doesn't increase at the same rate as load, that means the axel you just fitted the harder anti-roll bar can sustain less grip than it used to in relation to the other axel. So harder rear-antiroll bar basically decreases grip (in relation to the front that is, not absolute grip) in the back making the car turn better.

But you should consider the fact, that harder rear anti-roll bar might be extremely dangerous if you need to swerve a deer or something other happens. Your car has a front biased weight distribution, so even if it were RWD it couldn't be modified to be neutral in every kind of handling situation. That's why cars like the Miata is designed to have about 50/50 weight distribution and also most of the heavy stuff is put as close to CoG as possible to reduce inertia when turning or balancing at the transition point between over and understeer.
 
Thanks for this explanation! I guess I'll save up and get front and rear swaybars - it makes the most sense.
 
Doesn't the MX5 already come with front/rear sway bars?
 
Thanks for this explanation! I guess I'll save up and get front and rear swaybars - it makes the most sense.

But like I said, if you put similarly harder font and rear sway bars the balance will not be affected at all. You just have more resistance to roll and the car will become quite a bit more uncomfortable when driven straight.

zephyrus17: yeah, but _HighVoltage_ asked help from autocrossing Miata people for his Volvo.
 
It comes standard with 22mm/19mm bars. IPD offers 25mm/22mm.

A lot of people suggest keeping the stock front one and putting a 25mm rear for autocrossing.
 
Why would you replace the front sway bar? A bigger one would just make the car understeer more and (at least partially) negate any benefit of installing a larger rear bar. I suppose it's a cheap (and IMO crappy) way to reduce roll without coilovers...
 
Why would you replace the front sway bar? A bigger one would just make the car understeer more and (at least partially) negate any benefit of installing a larger rear bar. I suppose it's a cheap (and IMO crappy) way to reduce roll without coilovers...
In Stock class SCCA Autocross (at least, the last time I checked the rules), one could replace the front sway bar, but not the rear and not the springs. Competitors will replace the front sway, and then play tricks with the alignment to get a touch more rotation.

Ignoring cases where the rules limit options, my preference is to use springs and shocks to control roll (and dive/pitch), and use swaybars to tune handling. I've actually disconnected my rear sway to reduce oversteer (similar effect to getting a larger front sway) for track time, while connecting it for street and autocross, to get the different handling balances I want for the different situations, while using one alignment.
 
In Stock class SCCA Autocross (at least, the last time I checked the rules), one could replace the front sway bar, but not the rear and not the springs. Competitors will replace the front sway, and then play tricks with the alignment to get a touch more rotation.

Ignoring cases where the rules limit options, my preference is to use springs and shocks to control roll (and dive/pitch), and use swaybars to tune handling. I've actually disconnected my rear sway to reduce oversteer (similar effect to getting a larger front sway) for track time, while connecting it for street and autocross, to get the different handling balances I want for the different situations, while using one alignment.

It's actually better to soften the rear rather than stiffen the front anyway. Stiffening your ARBs messes with the crossweight too much.
 
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