spd579

iTrader: (1)

Ok, so I was driving to work this morning and braked hard and the right locked (a lot easier on cold roads) and I almost rear ended someone. So on my way home this afternoon I thought I'd try to see if it was bad enough to pull the car to the right...and it does relativly bad. From like 60 mph it will pull into the other lane without my hands on the wheel. So when a friend get over I'm going to bleed the drivers side hoping I can find an air bubble....we'll see. You guys have any other ideas besides what you've already stated and the possibility of a bad caliper.

sjmarcy

Largest issue is that you have two wheel braking for the most part. Get larger rears, something like NB Sport Rears at least. You have a big brake kit and stock 1.6 rears, is that correct? Get the car corner weighted, make sure calipers are good and well bled, basic stuff.

Savington

iTrader: (31)

I know brake bias is your "topic of the week" but I'm having a pretty hard time seeing how a front/rear bias issue would cause the car to pull to the right. He should address bias, but it's not causing his particular issue.

spd, bleed the fronts, check tire pressures, and if you have coilovers at least make sure the ride heights left to right are close to the same. Chances are you have a low tire or a bubble in a caliper somewhere.

sjmarcy

Topic of the week, huh? How about my first post on Miata.net over five years ago?

See post #18: http://forum.miata.net/vb/showthread.php?t=41805

Brake balance is basic Engineering and is far off on many, many Miatas. In fact my first posts on Miata.net years ago noted the issue. I always test that on any car when performance-driven. Excess front bias will accentuate any tendency towards pulling as there is insufficient stabilizing from out back / sharing the work at a given rate of deceleration. Miatas tend to front-lock the front right corner, just as this person has experienced. If you want your car to stop as fast as possible, in a controllable and consistent manner, you need all four tires helping out in a balanced manner.

I used to design braking systems, many are out on the market.

Following the principles I've explained here and elsewhere leads to better braking. I showed a now well-biased Miata braking system which can trail brake like crazy, unlike most Miatas. The car has been transformed, inexpensively. You can't fool the datalogger along with some basic tests Mr. S. Let's see your G-Gs and other data, if there are any issues I'd be happy to help you out.

From what I can gather in this thead, the OP needs some attention to braking fundamentals on his car. Such as those noted, and others. This seldom comes from vendors.

Savington

iTrader: (31)

Yes, topic of the week. You have an exceptional ability to constantly talk about a very specific topic, regardless of whether the topic is relevant to a specific problem. I'm not sure why you think G-G plots of Miatas showing excellent trailbraking capabilities has even the slighest thing to do with a car that pulls right under hard braking. I have a car exactly like the OP's sitting out front of the shop right now (Wilwoods on 11" rotors in front, 1.6" rears, stock bias) and it will stop straight and true from triple digit speeds. I won't argue that the bias isn't absolutely awful on that car, and we'll be adding a bias valve and 1.8 rear rotors (just like my own turbo car which has excellent bias) but it doesn't cause undesired lane changes on street tires or r-compounds - this is a fairly concrete fact.

I'm not really sure what you're trying to insinuate with your vendor comment, either. It appears at first glance to be an exceptionally petty (and poorly veiled) shot at me and Trackspeed, but I'll give you the benefit of the doubt on that one. There are plenty of vendors that understand the bias issues these cars have. FM had their own fittings made to make the Wilwood prop valves install significantly easier than they normally would. M-Tuned offers a bracket that allows 1.8 owners to install sport rotors without changing the caliper over, which makes it easier and cheaper to address bias issues. V8Roadsters offers different piston areas front and rear on their mondo 4-wheel 11.75" BBK to ensure proper bias. Trackspeed recommends the use of a Wilwood prop valve with our 11" BBK, and that recommendation comes from our own experience comparing stock bias vs. modified bias on Wilwood 11" fronts and stock 1.8 rears.

When the OP is ready to address his bias issues, there are a variety of vendors in the community that will be more than willing to assist him with a solution that matches his needs and usages, and Trackspeed is one of those vendors - but I won't attempt to delude the OP into believing that a rear brake upgrade will somehow solve a problem that isn't caused by inadequate rear brakes.

sjmarcy

Are you a vendor? If so, of what?

I know a lot about brakes, and share what I know. I'm helping 4-5 Miata owners get their brakes optimized right now. They'll all speed up and their Miatas will be easier to drive fast.

I'd be happy to help you out, just let me know.

hustler

iTrader: (6)

I'd love to hear what you can do to improve the brakes on one of the top 3 fastest Miatas in the country, I genuinely mean it. I'm not sure which caliper he and I have up front in respect to bore size. I don't seem to have a problem trail-braking into the apex with my car even without aero.

mgeoffriau

iTrader: (7)

That's a very generous offer.

What kind of help could you supply?

I am thinking of going to 1.8 front brakes.

But I will probably be stuck with 1.6 rear brakes.

Upsizing my brakes is an issue because of RPF1 clearance.

Going to much larger rear brakes would likely require new wheels.

I have no idea when my budget would support both new wheels and brakes.

So probably I will just try it and see if I can correct bias with different brake pads.

emilio700

iTrader: (3)

sjmarcy

You can trail brake about any car, but are you doing so using all of the available traction or not, and how stable is the car at that time, etc?

Cars that are running well tend to have things ignored on them, just the way it goes. Since they are fast enough to beat those they presently run against, effort eases off. Some of the earlier Miatas I measured with significant brake bias woes left their brakes alone at the time, noting that they were beating others. There are always things to improve on any car. Whether it be brakes or other stuff.

Let's see some performance data on the cars you noted to start out with, along with the brake specs, car setup, lap times, driver comments, etc.

Thanks.

JasonC SBB

If one has no adjustable end links, adjusting one corner up and the opposite wheel down will also not affect height.

Savington

iTrader: (31)

Not my car. I just wrapped up my 4th win in a row at Buttonwillow in the Miata Challenge Unlimited class, edging my main rival by about a tenth and a half (1:55.804 to his 1:55.930). Second time this season we've been split by less than two tenths of a second. In addition to tires (NT-01s to C71s and back again) and power development (up to 350whp and 290wtq, peak torque available from 4200rpm to 6200rpm, ABSURDflow owns your soul), I've had three different pad compounds in the front this year, two different compounds in the back, with constant tweaks to the bias **** to ensure the car is to my liking. Not to toot my own horn, but I cut my teeth 7 years ago on 125cc single-speed karts with rear brakes only so I like to think I know a thing or two about the benefits and nuances of trailbraking. One of my pet peeves is a car/kart that doesn't rotate on the brakes.

hingstonwm

iTrader: (2)

Congrats!!! Would love to see an in car of you hustling the car around the track!!

hustler

iTrader: (6)

Wilwood front calipers (not sure on piston size) on Corrado rotors
1.8 rear brakes
Wilwood prop valve
DTC-60 all the way around
AST 5100 shocks with 700/400 springs
2.7*f/2.5*r camber, 3.5*caster, 1/16 tow-in rear
4.0"f/4.25"r ride height
No aero

4.1 seconds under the SM record at Hallett, my buddy who knows how to drive went even faster. I should have added rear sway bar because it still under-steers a little but the car is incredibly easy to drive in all situations (my "real-driver" buddy agrees and got out of the car commenting about how much he liked the car).

sjmarcy

Do you have data besides motor output?

Rear braked karts don't really trail brake.

Car details besides power and that you've used a few brake pad compounds?

Need aero and downforce figures, etc.

sjmarcy

Datalogs for a few sessions at a few tracks, and other details?

Machismo

iTrader: (1)

Check out BOTH build threads - information you seek is there. In the real world - faster is faster. I have watched both of these cars morph into what they are now. There is a method to their madness, and depending solely on datalogs and dyno plots is for bench racing. Lap times speak for themselves, period.

hustler

iTrader: (6)

Do you want "shock-pot" data too? I don't have a data-logger that logs YAW so i guess we'll have to assume that everything is wrong. I'm certain that no matter what anyone posts here, you'll deem it "wrong." Its easy to go through your posts here and on miata.net and see you demonstrate that no one has ever done anything to your liking. Obviously your service of arbitrary criticism is a labor of love. I'm also fairly certain that you'll never find the CFD, wind tunnel, YAW logs, or any other data you dream up that no low-budget, weekend warrior owns. Now is that part where you'll tell us that we cannot pick the "appropriate brake equipment" without $20,000 in data logging equipment so we should all leave our brake stuffs stock.

sjmarcy

Perhaps a new thread could be opened as this one is getting off topic for the OP. If one wants some help from the experienced, a decent attitude might help.

So far the only data I see here is a few chassis dyno plot peak readings. On yaw FWIW you can get decent information from the GPS alone if so desired…if more detail proves necessary then you can add a sensor. I've set up many, many very fast cars behind the scenes, and helped them go even faster. A key requirement in such an endeavor is a good attitude, this appears to be hidden or in short supply here. Perhaps I am mistaken, I have limited time, so I choose.

hustler

iTrader: (6)

"Insufficient data" on a handful of the fastest Miatas in the country [not mine] doesn't bode well for you assertion of abject failure, nor does it suggest that your attitude is "good" either.