1 2
NOHOME
NOHOME MegaDork
1/19/22 8:44 p.m.

Looking for ways to upgrade the brakes on the Molvo. I am aware of the sportsbrake option that is just a caliper mount and a rotor away from done and it would keep it all Mazda. I am also aware of the big $$$ Willwood stuff.

 

Ran into a conversion in one of the FB groups that uses a Mustang caliper and a 2016 ND rotor. The vendors cake is in the $200 bracket sale. These calipers are cheap and seem like an upgrade from the stock Miata units. 

 

Has anyone here seen such a conversion in the flesh and or have any opinions?

My concerns are with the rest of the system as it pertains to MC size and front rear balance.

Javelin
Javelin GRM+ Memberand MegaDork
1/19/22 8:53 p.m.

Honest question, what's the point of a caliper upgrade on a track car that's not a fixed-caliper?

ShinnyGroove (Forum Supporter)
ShinnyGroove (Forum Supporter) HalfDork
1/19/22 9:26 p.m.

What are you trying to fix with the braking?  The usual issues with stock Miata brakes are low heat capacity and pad taper that's inherent to sliding pin calipers.  Seems like these would solve the heat capacity issue, but probably double the unsprung weight and make it ride like a garbage truck over bumps.  

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
1/19/22 9:50 p.m.

Bigger rotors, but then drill and slot them so they have less mass to absorb heat?

Are those calipers iron, or the nice aluminum calipers?

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
1/19/22 9:53 p.m.

What's the piston area on that caliper?

NOHOME
NOHOME MegaDork
1/19/22 10:10 p.m.
Keith Tanner said:

What's the piston area on that caliper?

Bit of googling suggest that they are 38mm dual pistons.  So 2260 mm sq.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
1/19/22 10:30 p.m.

That's about 15% larger than stock, back of the envelope. 

Javelin
Javelin GRM+ Memberand MegaDork
1/19/22 10:47 p.m.

I did a video on sliding versus fixed calipers and the weight alone is insane thanks to the brackets and pins.

 

Shavarsh
Shavarsh Reader
1/19/22 10:50 p.m.

I have a set of those on the shelf waiting for a rainy day if you need some measurements.

akylekoz
akylekoz SuperDork
1/20/22 6:15 a.m.

I also have a set of calipers if someone wants them.  Aluminum two piston, 28k miles on them over 15 years.

z31maniac
z31maniac MegaDork
1/20/22 9:30 a.m.

By the time you order their brackets, get some calipers and rebuild them, how far off are from one of the BBK's already available for the Miata?

amg_rx7 (Forum Supporter)
amg_rx7 (Forum Supporter) SuperDork
1/20/22 10:00 a.m.

Those calipers look rather heavy 

NOHOME
NOHOME MegaDork
1/20/22 12:36 p.m.

In reply to z31maniac :

This setup will cost $350+/- depending on the pads you choose. ( vendors FB page of propaganda)

 

Have not looked at the cost of the other options recently but  keeping in mind that stuff in Canada is roughly twice the advertised price in USD, nothing is cheap. These guys are actually on this side of the border.

What are you trying to fix with the braking?  The usual issues with stock Miata brakes are low heat capacity and pad taper that's inherent to sliding pin calipers.  Seems like these would solve the heat capacity issue, but probably double the unsprung weight and make it ride like a garbage truck over bumps.  

 

All of the above. Keep in mind that the Miata brakes I have are working with a 2800 lb car. Besides, are we as enthusiast not always in "Continuous improvement seeking" mode?

The problem I have with brake design is that it is such a Rube Golberg system. Pedal ratios, cylinder ratios, boosters, F/R distribution, clamping force and coefficient of pad friction and rotor lever-length all conspire to make the amateur f -up something that results in a complicated effort for a null gain and future maintenance difficulty. 

 

codrus (Forum Supporter)
codrus (Forum Supporter) GRM+ Memberand PowerDork
1/20/22 12:52 p.m.

2267 mm^2 is about the same as an NB2 sport caliper (single piston 54mm gives 2287 mm^2).  What master cylinder are you using?  That might be a bit squishy on a 90-00 7/8" master, but I would think the NB2 15/16" or 929 1" would work well.

I don't know if a 2-piston slider is enough better than a 1-piston slider to be worth the hassle of having a mix of different parts though.

 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
1/20/22 12:57 p.m.

It is important when seeking improvements to be able to identify what actually constitutes an improvement :) That's what ShinnyGroove's question meant.

With brakes, there are two basic things: single stop distance, and heat capacity. If you're street driving, you're mostly interested in the former. So that's all about balance. As long as you can generate enough brake torque to lock the tires, you can't really use any more. This is where front-only "big brake" changes can result in decreased braking performance - if you bolted those Mustang calipers with larger rotors on the front of a Miata, you'd have a bunch more front brake bias on a car that already has lots. Especially with a longer wheelbase Molvo that has less weight transfer than a Miata and thus requires even less front brake bias than stock. So your single stop braking distance would get longer because the rear brakes would not be able to contribute much.

The best investment you can make in single stop brake performance on this car is an adjustable proportioning valve.

Heat capacity requirements go up directly with weight and with the square of speed. So a 2800 lb car isn't that big a step up from a 2400 lb car, but a 200 hp car can put significantly more heat into the brakes than a 100 hp car. Of course, that assumes that you're doing multiple hard stops so it's rarely a street car problem unless the brakes are badly underspecified.

The prop valve will help here as well, because it'll let the rear brakes do more work and thus absorb more heat for a given amount of decel. In reality, in track work, you'd probably just be decelerating harder because you could :)

obsolete
obsolete GRM+ Memberand HalfDork
1/20/22 12:58 p.m.

Looks like the ND rotors gain you about 1.75" in diameter (and corresponding amount of mass) and the aluminum Mustang calipers gain you a fair amount of pad surface area while being lighter than the iron NA calipers. Despite the objections from fixed-caliper purists, this seems like a win to me. We did a very similar upgrade on our Chevy Beretta LeMons car using brakes from a 4th-gen F-body and went from melting pads to being able to outbrake most of the field with consumables that were dirt cheap.

Edit: I should mention that we also added a larger master, swapped rear drums for discs, and added a proportioning valve at the same time. It wasn't a simple front-only upgrade, it was pretty much a whole new braking system.

rslifkin
rslifkin UberDork
1/20/22 1:00 p.m.

From what I'm seeing above, I'd consider it a worthwhile upgrade (albeit not as good as fancy fixed calipers).  It gives you a lighter caliper that accepts bigger pads (and should still have good pad selection available).  And lets you run bigger rotors.  So other than the downside of the extra rotor weight, I'd expect better performing brakes from the swap. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
1/20/22 1:03 p.m.

In reply to rslifkin :

I predict a downgrade or at best, no change (assuming the existence of adjustable brake proportioning) along with a slightly longer pedal.

NOHOME
NOHOME MegaDork
1/20/22 3:05 p.m.

Context: This car will never see competition of any kind. It was built as a cruiser. Just looking to make it better at that job.

Had NOT considered the more rear bias as Keith suggested. As is, with the 200 TW tires, I feel like it is does not want to lock up the front brakes as easy as I would like. Of course, I weight this against the FRS that I drive all the time, so maybe not fair.

 

Obsolete wrote:

 I should mention that we also added a larger master, swapped rear drums for discs, and added a proportioning valve at the same time. It wasn't a simple front-only upgrade, it was pretty much a whole new braking system.

 

 

And this is the crux of the matter. I don't want to re-invent brakes because I don't feel that I am qualified to do so. I posted this originally to see if this vendors idea was already in use in the community and if there was any feedback. I think it runs into the same problem as all big brake stuff: It is only one link in a complex chain and hard to predict what it will do to the system.  Not looking to make brakes my next hobby.

z31maniac
z31maniac MegaDork
1/20/22 3:33 p.m.

Have you considered changing pads for something with a bit more bite? For something that's going to see pure street use, this doesn't sound worth it. 

rslifkin
rslifkin UberDork
1/20/22 3:38 p.m.

If the concern is just stopping power and not heat capacity, go for more aggressive pads.  That alone was enough to take the tiny brakes (single piston calipers, 11 inch rotors) on my Jeep from crap to damn good in terms of stopping power.  And that's stopping 4300 lbs. 

Berck
Berck New Reader
1/20/22 3:42 p.m.
NOHOME said:

Not looking to make brakes my next hobby.

Then you probably shouldn't:)  Mazda professionals spent time/effort/money designing a brake system that's really pretty good.  Spec Miatas don't have major problems with stock 1.6l brakes and they use them a lot more than any cruiser will.

I enjoy brake pads with a lot more bite than what seems typical for street use.  I really, really love the feel Carbotech/G-Loc brakes, but I don't like them on the street because of the noise and the wheel-destroying dust.  Finding some pads with more bite might be exactly what you want.  Unfortunately, I've tried a bunch, and ever since the Axxis metal masters went away, I've been disappointed, so I don't have specific recommendations.  I'm running the powerstop Z26 now, and I'd like something more bite than that, but it's better than stock pads.

obsolete
obsolete GRM+ Memberand HalfDork
1/20/22 4:10 p.m.
Berck said:

...ever since the Axxis metal masters went away...

I miss those too. 

WonkoTheSane
WonkoTheSane GRM+ Memberand UltraDork
1/20/22 4:52 p.m.

I'll second Keiths' comment that a brake bias adjustment is an amazing upgrade on a NA.  It really helped dial it in on track.   I wouldn't have bothered for the street, though.

What pads do/did you have on it?   Also, how old was the fluid?   Fresh fluid and some Hawk HPS might be enough to make you happier with the performance, but remember that the fancy track-oriented fluids will want to be changed a bit more often than generic parts store brand stuff. 

NOHOME
NOHOME MegaDork
1/20/22 4:55 p.m.

Open to brake-pad suggestions then.  Might also try the bias thing since I think I have a spare Willwood proportioning valve kicking around for some reason.

1 2

You'll need to log in to post.

Our Preferred Partners
dwqFngCWUzSOekOxFM81Cj9vYCJt5sECMjzwjRrfEllLLcJIR8nDLjXj6e385GjS