mazdaspeedmiata

i just found this on the ricer forum incase anyone is interested

ClubRoadster.net

charchri4

That is really interesting he had to tip his front bracket back just like I did. Thanks for the post!

577nitro

Big brake questions seem to never end. So Jim, I understand the 1"+ master size and you have chosen correctly to do so, But using what boost with this set up? I will be running 14 " Wilwoods up front and 11 in the rear, so both pressure and volume are going to be very important...this is a 90% track car

V8droptop

Keith had a lot to say on the subject. We are really out of the "normal" brake sizes for most miatas, but you want to focus on caliper volume and make sure your master is a match. For boost ratio, I'm not really sure, but here's some of my research threads, there is mention of a few ratios:

Miata specific:
Some interesting brake information (tech!) - MX-5 Miata Forum
Mixing and matching brake masters and boosters - Miata Turbo Forum - Turbo Kitten is watching you test compression.
General:
Outlaw Disc Brakes
Brake Technical Information
https://www.facebook.com/notes/joes-...18382938195729

577nitro

I think Wilwood said a min of 1" on the cylinder. but I'll check for sure...mostly interested in the booster id anyone has gone a different direction

Shrimpy59

I'm out of town and can't get logged in with the admin security stuff but I'm still Jim... I just used the booster as it was in the Miata and it works great. The only tweak I need to make is I have the prop valve turned all the way out and still need more back brake so I am thinking of moving it to the front lines.

577nitro

Hmm, I think the line size to the rear is too small if you are running larger calipers to the rear as well. I know that I would absolutely want to be able to correctly adjust the balance

Shrimpy59

I thought about the lines but leaning toward mis matched calipers. In 98 GM improved the F body brakes with larger caliper pistons all around and I'm running 96 rears with 00 fronts. It's not far enough off to really bother anything but at the very edge of grip especially I am starting to turn in the fronts will lock before the backs do and it's kind of annoying.

577nitro

That almost sound like more of a weight transfer issues, under braking the nose dips, under the compression. You might look at the compression ratio is of your shocks, and are they able to support you spring weights. I feel once I settle my own booster quiz, I will be using AN-3 (3/16th) fitting on a Tilton lever prop valve with control in the cockpit. They have pretty much figured out the amount of residual pressure needed...here is a write-up from them;
https://tiltonracing.com/wp-content/...ning-Valve.pdf

charchri4

Nahh I'm running Spec Miata track suspension and it was fine with the stock brakes. I'm running 3/16 lines also but what's the booster quiz question?

577nitro

Well, I have seen everything from a GM (some year Vet) to a Explorer, and a Miata Sports boosters. My question is has anyone done any kind of a test on them?
On the diving are you running autocrosses or real road course, and then what shocks and spring rates

charchri4

No tests that I know of but I suppose the bigger the booster the bigger the boost. I would rather have a bit less boost and more feel of the road myself but I really never gave it much thought. At low speed my pedal feels about the same as it did with the stock brakes. Anything over 100 is way more responsive than it was before but that really doesn't have anything to do with the booster I don't think. I think if I were you I'd try whatever you have and see how it works before changing it.

On driving yes it's road course, autocross, back and forth to work and even a drag strip. I never would have changed the brakes if it wasn't for running road courses. Most of my track time is on a 2.3 mile, 13 turn road course that goes from the top of 4th, 130 mph to comfortable in 3rd at 65 mph.

Suspension is Spec Miata exactly what the race cars run which I also would not run if it wasn't for running the road course. Bilstein HD SM shocks F4-B46-1488-H1 and F4-B46-1489-H0 with Eibach 700/325 springs. I'd like to take my fronts up some though maybe around 800 and a tad softer bump in the shock.

Shaikhs sheet has been around a long time but still pretty useful.
http://www.y8spec.com/suspension/Mia...eet_v5_1SI.xls

577nitro

Me too, I am going to use the spec Miata as a guide on springs, and using either Ridetech, or Qa1 double adjustable coilovers will probably start with 650 up front and 375 in the rear, and use a 27mm bar...not set on what size for the rear yet. I will limit the rear suspension travel to 2 up 1 down t star with

charchri4

That is a pretty out dated ratio and IMO too much rear spring for only 650s up front. I'm not saying it won't work because guys used to run rates like that all the time but check out 949, Fat Cat, SM or anyone else out there actually on track these days (meaning not Tein or Ohlin) and the ratios are never over 2 to 1. SMs are 700/325 Xiadas are 700/300 and even Shaikhs personal turbo car (the brain behind Fat Cat) is at 550/250. BUT those numbers are all for 4 cyl cars that don't carry the load we do up front which is why I feel mine would be better balanced around 750 to 800 in front for the 325s out back.

577nitro

Wel, my rear suspension is not MX5, so will have a different baseline than you have and will start low and move up if I must. Try your better balanced approach, and You will be able to do so, before mine is on the road It will be interesting to see what turns out. This would be useful to a lot o folks as I have found on 3 other forums a lot of the cars are wanting in a different set up

577nitro

Here is a spread sheet to do some calculating


Spec Miata Community: If you could pick your own spring rates...

paNX2K&SE-R

So the Explorer master cylinders bolt right up to the Miata boosters and function fine as-is? No problems with a different stroke length of the pedal actuating rod or anything like that?

577nitro

A bit of a spacer 1/8th or more is required as I have been told by those who use them

charchri4

Humm. You know I honestly don't remember and I just did it 4 months ago! Mostly what I remember is messing with the end support to rebuild it for the bigger master. I did play with shims in the end of the master to find out where engagement started. It's no big deal you just take a small thin washer and put it in the end of the master and it stays there. But I'm pretty sure mine engaged right away and I have no shim in it.

BTW there is a couple different configurations on lines over the years for this master and for mine I had to get adapters for 2 of the lines. There probably is one made with the right line size already and it would be handy of someone tracked that down!