Reply With QuoteSo you're running the 9" rotors up front & the 10" rotors in the rear? Does that require any change to the master cylinder? Did you need to put in a proportioning valve?Originally Posted by jrj512
Ditto from the guy that got volunteered to have the discussion. And i am one of those supposed A-holes in tech...And those of us in E Street who do care and are running for season points do appreciate what you did!
You were great and we welcome you to the mean STS class.
fun place to play.
So you're running the 9" rotors up front & the 10" rotors in the rear? Does that require any change to the master cylinder? Did you need to put in a proportioning valve?
I did not measure them. It's whatever rear brakes came on NA 1.8. You have to get a new rotor, new pads, and a new caliper mount, but the rest stays as is. 1.6 and 1.8 had the same rear calipers.
You're making this much harder than it is.
They are similarly proportional front to rear in terms of size, so rear would never be larger than front. Listen to JJ, its not that tricky.
For 1.8 brakes, get oem 1.8 calipers in front and the corresponding bracket/rotor/pads. For the rear, keep your caliper/pads, get the larger rotor and bracket. Done.
Polished Turd Racing
Mick wrote: "I think Jerrett is the best autocrosser I have ever seen naked."
Why go to 1.8 front brakes? The idea is to provide better balance by adding larger rear brakes so the fronts do not lock up so easily. That is also why you run crappy ceramic pads in the front and grippy pads in the rear with this setup.
Leave the front brakes as is, but with ceramic pads.
Yes, there will be fade issues at ECR, but you can mitigate that with bigger balls and more efficient braking. I would not base my whole brake setup on ECR when they seem to work fine everywhere else.
^+1000
Polished Turd Racing
Mick wrote: "I think Jerrett is the best autocrosser I have ever seen naked."
Gotcha'! Now I understand.
To play devil's advocate; wouldn't a proportioning valve do the same thing? At that point you could upgrade to bigger brakes all the way around & then balance them out to avoid lock ups on the front wheels. I just know that a good brake setup can make a big difference on a track & since I plan on tracking the next year (hopefully) I want to spend the winter months getting it dialed.
Last edited by Nudnik; 10-08-2014 at 03:59 PM.
Check the rulebook.
1995 M Edition
Yep, time to dig in and read. The first couple of questions are freebies, but you've reached the quota and now must read the rules. Remember, if it doesn't say you can, then you can't.
Polished Turd Racing
Mick wrote: "I think Jerrett is the best autocrosser I have ever seen naked."
HAHAHA! I totally forgot the original purpose of this thread. I got lost in a world of upgrades.
We would never intentionally give you bad information, but it’s best to read the rules for your class yourself. Memory and interpretation can shade what we think the rules are. Believe it or not I have seen rules misquoted on the internet. (not interpreted the same as I would so they were wrong)
If you get called out on something (it will not happen at a local event unless it’s something that gives a large advantage) it best to know for yourself what the rule book says.
Here is the deal on 1.6s & STS brakes IMHO. Replacement prop valve not allowed though you might be able to slide the OEM AT valve by at local events. Going to really stiff front springs (700 or so) and appropriate shocks decreases weight transfer thus flaming right front flat spots and lesser rear influence in turning. By my voodoo math (i'm sure someone will tell.me this is wrong) you increase swept area at rear by 17 percent or so. Combining that with less agressive fronts and nasty grip rear pads eliminates front lock AND enables you to rotate the car with the brakes. The junk yard swap parts less pads cost less than the rear Hawk pads. It absolutely works and is $$$$ cheaper than using the aftermarket brake allowance available under the rules.
David W planted the idea of more rear brake bias and parts book shopping with input from mazdacomp proved it right at least in my uninformed opinion. We moved from cheap lifetime fronts with HP30 rears to HPS front and 30s rear before nats and it is even better balanced. Just need to learn how to drive..
Steve E
Since I talked to you about this a few years ago I have learned a lot more. At a certain line pressure the stock proportioning valve starts restricting additional force to the rear brakes. So the harder you push the pedal the higher percentage of force goes to the front brakes. For a street car this simple solution works pretty well and keeps grandmothers from locking up their rear tires. But for a race car it sucks.
The solution is two fold. One we want to add more rear bias through more aggressive rear pads. Second we want to make the brake system more aggressive overall such that we can lock up the tires at a lower line pressure. The stock proportioning valve allows for 50/50 bias up until a certain point, then it kicks in pretty hard:
http://www.flyinmiata.com/tech/stock_bpv.php
As a side note the real solution would be to allow adjustable proportioning valves. But that is never going to happen in ST autocross. One other solution that actually has a possibility of passing would be to allow stock proportioning valve removal. If anyone is interested in experimenting and testing this this let me know.
Since I'm new to Miatas & specifically the brake setups used, I lack the knowledge to understand some of your "shorthand." Can you elaborate on "HPS front" & "30s rear"? I know that I'm currently locking up the fronts long before the rear wheels lock up & I'd love to get a better balance in the system. I have a set of brakes from a 1.8 that I plan on putting on the rear but I guess I'm not sure what pads to use.
While I'm here, is a Racing Beat intake allowed? According to the rule book on page 85 Rule 14.10 Section C. (see below)
"The air intake system up to, but not including, the engine inlet may be
modified or replaced. The engine inlet is the throttle body, carburetor,
compressor inlet, or intake manifold, whichever comes first. The
existing structure of the car may not be modified for the passage of
ducting from the air cleaner to the engine inlet. Holes may be drilled
for mounting. Emissions or engine management components in the
air intake system, such as a PCV valve or mass airflow sensor, may
not be removed, modified, or replaced, and must retain their original
function along the flow path."
That reads like Greek to me b/c I can't tell if I can or can't change it out. I'm pretty sure I can b/c I think it uses the stock MAF sensor but not positive. Ugh... these rules are hard to decipher sometimes.
^As for the intake, you can install the RB and it does use the OEM MAF.
HPS is for Hawk HPS pads. Not sure which pads the 30s are.
2004 Mazdaspeed Miata- Velocity Red (sold)
Hawk DTC 30.
Those are so grippy that my back brakes don't make brake dust, they make rotor dust.
- James
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