bracing

bryan Sampson · Post by **bryan Sampson** » Fri Oct 12, 2007 6:28 am

Can anyone tell me if adding upper and\or lower bracing to my 89 mx would make any noticable difference in normal road driving? Not that she aint sweet now!

Bazza · Post by **Bazza** » Fri Oct 12, 2007 9:58 am

Welcome to the forum Bryan. I was wondering about the engine bay
strut myself so will watch and see the response - there's one on TradeMe at the moment but a bit pricey. Bazza.

poison · Post by **poison** » Fri Oct 12, 2007 10:07 am

I have the aluminium engine bay brace and to be honest they are really just for looks as they all have some flex in them, I have seen lots of brand over the years and they all have some flex. Some of the NB’s came out with a steel three way brace which takes it back to the fire wall too. These would be the only one’s that could possibly make any difference, the MX5 does not have a tall shock towers so any improvement is not likely to be noticeable for a road car. All of course IMHO which by the way is right J

The rear sub-brace is supposed to give the biggest improvement at open road speeds. I have an unused one I bought for my NA that I would sell for $50 if anyone is interested. The NB comes for the factory with this sub brace factory fitted.

Growler · Post by **Growler** » Fri Oct 12, 2007 10:26 am

poison wrote:...I have an unused one I bought for my NA that I would sell for $50 if anyone is interested.

Can you post a picture of it please?

Growler.

Ian · Post by **Ian** » Fri Oct 12, 2007 11:55 am

Underbody braces are the most effective.
Mazda responded to the the need for underbody bracing (front and rear) from about 1993 onwards, and these should be a very easy addition. Aftermarket versions are also available but are not really necessary you dont have access to some oem ones (MX5 Mart can help here). The rear brace set up is a bolt on ladder frame type, with the front being a simple cross brace.
Unless you have billiard smooth roads or only drive to the supermarket, this would be the FIRST mod I would do to an early car.
MX5s don't have struts, so this needs to be stated first.
In saying that, the jury is out on the benefits of a front shock tower brace. It took Mazda 9 yrs to introduce a brace with the launch of the NB, and personally, I suspect that it was more driven by their marketing dept than their engineering dept.
Many of the aftermarket (shock tower) bars on the market are subject to flex and as such, look good but achieve absolutely nothing.
I was lucky enough to pick up a good second hand genuine NB bar which is strong but heavy (certainly none of the factory ones I have seen are braced to the firewall, and that includes the 1994 MX5 Turbo and the Aussie MX-5 SP turbo).
On my next track day, I will be removing it to save 3.5kg....but depending on lap times, I may reinstall for circuit use, given that the loads imparted by a modified suspension together with R spec tyres on a high grip surface are way more than could be generated on the highway.

Hope this helps,

Ian

Growler · Post by **Growler** » Fri Oct 12, 2007 1:13 pm

Ian wrote:...MX5s don't have struts...

Huh???

Ian · Post by **Ian** » Fri Oct 12, 2007 1:55 pm

MX5s have always had telescopic shock absorbers and coil springs, incorporating wishbones in their suspension design, and this is one of the reasons why MX5 suspension provides superior handling.
"Struts" is the usual shortening or the word used to desribe a different type of suspension mechanism - McPherson Struts. These, by their very nature and design, place substantial loads on their top anchor points, hence the growth in the market of 'strut braces'.
Mazda could so easily have taken a 323 engine/suspension and given us a front wheel drive with McPherson strut MX5....but they chose not to. Celebrate the fact they chose to spend more money on a better handling layout! I do, every time I drive mine.....

Growler · Post by **Growler** » Fri Oct 12, 2007 3:47 pm

Ian wrote:MX5s have always had telescopic shock absorbers and coil springs, incorporating wishbones in their suspension design, and this is one of the reasons why MX5 suspension provides superior handling.
"Struts" is the usual shortening or the word used to desribe a different type of suspension mechanism - McPherson Struts. These, by their very nature and design, place substantial loads on their top anchor points, hence the growth in the market of 'strut braces'.
Mazda could so easily have taken a 323 engine/suspension and given us a front wheel drive with McPherson strut MX5....but they chose not to. Celebrate the fact they chose to spend more money on a better handling layout! I do, every time I drive mine.....

Yes - But the shock assembly bolts into the strut/shock tower.
They have struts...or telescopic shock absorbers. They both do the same job (Just different naming I guess)
A top and bottom arm (Std MX5 suspension) arrangment is superior because the wheel stays upright thoughout its arc as the wheel goes up and down. With a McPherson set up the camber (And caster to a degree)increases as the wheel goes up.

Any brace you put on will be beneficial as it will stop the body flexing through a corner. A strut brace merely transfers the load from one strut to another and stops the strut towers from flexing towards each other.
The same principle applies to the rear suspension. If you look at it the rear subframe it is similar to the front only upside down. From 1991? onwards they put a brace across the bottom to pick up the inner bottom arm suspension points. This acts similar to a strut brace.
I'm guessing Mazda engineers didn't add to the original design to save weight and cost and that most cars weren't intended to be driven on a race track.

Back to Bryans original question. A brace wouldn't make much of an impact with normal day to day driving - however driving quickly on winding roads there will be a slight difference...whether you feel it or not is up to the individual.

OK...It is beer o'clock now!!

Growler.

Ian · Post by **Ian** » Fri Oct 12, 2007 6:17 pm

Growler...be reasonable! The MX5 either has struts or it doesn't!!
Your post more than adequately justifies the use of a 'strut brace' on a McPherson Strut equipped car.
You then imply that because a telescopic shock/wishbone set up (the MX5 method) and a McPherson strut are both forms of suspension damping, it stands to reason that the MX5 will also benefit from an underbonnet brace!
This is false logic. The way the respective forces are transmitted into the chassis are very different, the point I tried to make (unsuccessfully it would seem) in my original post.
This also goes some way to explain why a Honda S2000 has no underbonnet brace (I think).

Trevor · Post by **Trevor** » Fri Oct 12, 2007 7:56 pm

Growler ---- “A top and bottom arm (Std MX5 suspension) arrangement is superior because the wheel stays upright throughout its arc as the wheel goes up and down.”

This is not so. The offset of the tyre contact patch in relation to the pivot point must be allowed for, and this is arranged by means of unequal length wishbones. The wheel does not remain vertical. If it did so, the tyre would side slip on every bounce and rebound.

For performances purposes, negative camber is often used to negate this design feature. Such an adjustment should increase tyre wear, but strangely I have found in practice that a slight negative camber can be of benefit, because edge wear during cornering is eliminated, at the possible expense of overall wear.

Interestingly I have a 1971 FF1 Subaru, which is designed to overcome this problem, by incorporating inboard brakes, thus enabling a large wheel offset, so that the pivot point is placed over the contact patch.

Growler ---- “Any brace you put on will be beneficial as it will stop the body flexing through a corner. A strut brace merely transfers the load from one strut to another and stops the strut towers from flexing towards each other.”

This is also not so. ---- The MX5 front suspension, for good reason, is arranged so that only vertical forces are involved in respect of the spring/shock assemblies. There is no loading across the car, except for an insignificant twisting moment.

Ian ----- “The way the respective forces are transmitted into the chassis (and) are very different,”

Exactly correct.

Whatever, the bendy bow shaped cosmetic gismos sold by accessory shops and purchased by “ricers” are a joke as are the said ricers.

No doubt my comments will encourage another negative Karma point, but so what.

poison · Post by **poison** » Fri Oct 12, 2007 8:56 pm

Trevor wrote:... purchased by “ricers” are a joke as are the said ricers.

Am I missing something... aren't we "ricers" as we drive a Jappa?

By the way Bryan welcome to the list and the passions of the fans within

I (obviously wrongly) thought the MX5 did have McPherson Strut’s… what is the difference??

And here's a pic of the brace.....

WiM · Post by **WiM** » Fri Oct 12, 2007 9:29 pm

From my own experience I would say that:
1) underfloor bracing is a must if you like the twisties

2) strut brace over the engine... nah, not really but it looks good

3) rear strut brace, dunno, but looking forward at testing this

4) get or the brace behind the seats OR if you want to get some more protection, mate get a roll bar! I used to have a Hard Dog in my car in Europe and OMG that made a huge difference!

I just bought a 5 over here and I will be going for 1, 2 and 4

Ian · Post by **Ian** » Fri Oct 12, 2007 9:30 pm

Trevor... Thanks for your support.

Gazza needs more answers!

Your turn...I give up!

Ian

bryan Sampson · Post by **bryan Sampson** » Fri Oct 12, 2007 9:32 pm

thanks for the thoughts guys as I thought these are probably unnecassary eye candy bits. And I do and would call the front suspension as by way of explaining what an MX5 has "McPherson struts.
Sambo.

Ian · Post by **Ian** » Fri Oct 12, 2007 9:39 pm

Oops, sorry Growler...
My apologies - I mistakenly attributed Poisons question to you.

Ian

Ian · Post by **Ian** » Fri Oct 12, 2007 9:49 pm

Bryan, as WiM says, the factory brace across the car behind the seats between the top seat belt location points (fitted from the 93 updates onwards) can be retrofitted to earlier cars. The NB versions of these incorporated windblockers and these also can be retrofitted. (MX5 Mart in Hamilton often sell them.)
If you are not fitting a roll cage, I would be doing this right after the under car bracing...

Cheers, Ian

Trevor · Post by **Trevor** » Fri Oct 12, 2007 10:25 pm

poison wrote:
Trevor wrote:... purchased by “ricers” are a joke as are the said ricers.
Am I missing something... aren't we "ricers" as we drive a Jappa?

By the way Bryan welcome to the list and the passions of the fans within

I (obviously wrongly) thought the MX5 did have McPherson Strut’s… what is the difference??

And here's a pic of the brace.....

A "Ricer" on most internet sites describes any sort of make believe "Racer", evident as a result of the useless cosmetic junk on his car, regardless of make or model.

McPherson was the inventor of the strut given his name. It was first extensively used in every day production models by Ford. The design considerably reduces the number of components required in the front suspension/steering, Do a Google.

Trevor · Post by **Trevor** » Fri Oct 12, 2007 10:50 pm

WiM wrote:From my own experience I would say that:
1) underfloor bracing is a must if you like the twisties

2) strut brace over the engine... nah, not really but it looks good

3) rear strut brace, dunno, but looking forward at testing this

4) get or the brace behind the seats OR if you want to get some more protection, mate get a roll bar! I used to have a Hard Dog in my car in Europe and OMG that made a huge difference!

I just bought a 5 over here and I will be going for 1, 2 and 4

Please not number TWooooooooo. It will not look good to those who know what is what. Same for three provided you mean some form of top bracing at the rear.

A big yes for number one, provided you are referring to the rear end. A look underneath will disclose how the lower wishbone points are out on a limb, and should be connected.

My 1997 as manufactured, has a second set of braces running forwards so as to resist longitudinal loads. All braces are tubular and straight, for maximum compressive strength, just as they should be. Piece of cake to reproduce using scaffolding, or any thick wall tubing.

Please explain the advantage of number four.

Trevor · Post by **Trevor** » Fri Oct 12, 2007 11:21 pm

Ian wrote:Bryan, as WiM says, the factory brace across the car behind the seats between the top seat belt location points (fitted from the 93 updates onwards) can be retrofitted to earlier cars. The NB versions of these incorporated windblockers and these also can be retrofitted. (MX5 Mart in Hamilton often sell them.)
If you are not fitting a roll cage, I would be doing this right after the under car bracing...

Cheers, Ian

Ian,

I can not agree that this brace is of real value. I have read that this was a factory addition, fitted in order to meet side impact rules, and its strength is debatable.

As I see it, it has no application in regard to chassis performance. I have removed mine to secure more leg and arm room. N.B. Contrary to previous argument, I do know something in respect of driving position.

Sincerely, Trevor.

biff · Post by **biff** » Sat Oct 13, 2007 8:50 am

Hi Poison,
If the brace will fit an NA I’ll have it.
How would you like me to pay for it, and can you courier it to Christchurch?
Cheers mate
Biff

biff · Post by **biff** » Sat Oct 13, 2007 8:50 am

PS, ya forgot the pic J

Ian · Post by **Ian** » Sat Oct 13, 2007 11:43 am

Trevor...
Re interior brace. I got off subject slightly. I did not mean to inferr that the interior brace acts as a chassis brace, but I do believe it offers a modicom of bracing to the body of the car, making for a slightly stiffer structure, just as a hardtop does in its own small way. I have a welded in (6 point) roll cage so my seat belt tower brace had to go as well.
Racing Beat make an alloy underbody brace (front) wich can be fitted either in place of or in addition to the factory front chassis brace. One of these is on my shopping list as is their front swaybar mounting support blocks. The Flying Miata butterfly brace is tempting, but freight would be a killer, and don't know if I want the extra weight of it, given my modest horsepower (these forced induction blokes don't have to worry! Right Biff??)

Cheers, Ian

Trevor · Post by **Trevor** » Sat Oct 13, 2007 12:12 pm

Ian wrote:Trevor...
Re interior brace. I got off subject slightly. I did not mean to inferr that the interior brace acts as a chassis brace, but I do believe it offers a modicom of bracing to the body of the car, making for a slightly stiffer structure, just as a hardtop does in its own small way. I have a welded in (6 point) roll cage so my seat belt tower brace had to go as well.
Racing Beat make an alloy underbody brace (front) wich can be fitted either in place of or in addition to the factory front chassis brace. One of these is on my shopping list as is their front swaybar mounting support blocks. The Flying Miata butterfly brace is tempting, but freight would be a killer, and don't know if I want the extra weight of it, given my modest horsepower (these forced induction blokes don't have to worry! Right Biff??)
Cheers, Ian

I have no info on the front braces you describe but will check further on the net. Is the factory front brace you refer to standard on the 1997 1800 I have, and if so what does it comprise?

The flexing I have noticed at certain speeds and which is well documented, appears to involve lack of torsional stiffness in the mid structure, always a problem in respect of open cars with full doors. However it could well have something to do with the front end, hence my interest.

However, the MX5 is very stiff when compared to many sports cars, and this was a feature I was aware when I purchased mine. Most important is that there is no scuttle shake.

Regards, Trevor.

biff · Post by **biff** » Sat Oct 13, 2007 12:37 pm

Hahaha,
I wish, the hairdryer isn’t on, the downpipe wouldn’t match up, and I want to get the sump done correctly, so it’s still on hold unfortunately L

From: Ian [mailto:mx5talk@mx5forum.co.nz]
Sent: Saturday, 13 October 2007 11:44 a.m.
To: mx5talk@mx5forum.co.nz
Subject: [MX5] Re: bracing

Trevor...
Re interior brace. I got off subject slightly. I did not mean to inferr that the interior brace acts as a chassis brace, but I do believe it offers a modicom of bracing to the body of the car, making for a slightly stiffer structure, just as a hardtop does in its own small way. I have a welded in (6 point) roll cage so my seat belt tower brace had to go as well.
Racing Beat make an alloy underbody brace (front) wich can be fitted either in place of or in addition to the factory front chassis brace. One of these is on my shopping list as is their front swaybar mounting support blocks. The Flying Miata butterfly brace is tempting, but freight would be a killer, and don't know if I want the extra weight of it, given my modest horsepower (these forced induction blokes don't have to worry! Right Biff??)

Cheers, Ian

93 1.8 NZ new, intake and exhaust mods, torsen lsd,konis and RB springs,Toyo T1Rs.
Roll cage, momo seat, Willans harness.

Anthug · Post by **Anthug** » Sat Oct 13, 2007 1:05 pm

Hi,

I installed the under car bracing front and rear on my 90 from Ross at MX5 Mart and noticed a good improvement.

After that was the front shock tower brace (STB) from an NB but only noticed a small difference.

It wasnt until I installed the Roll Bar that the car really stiffened up (bolted to 4 points welded). That was the most noticable change by far.

The STB has just been re-installed but did not notice much difference, just a little in the steering.

Regards,

Anthony

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Just my $0.02

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