Laur3ns

Not until you've driven the Nürburgring Nordschleife, at speed, in the wet, without ABS. It's only 20.8km with ~73 bends of which most blind. And very bumpy.

JasonC SBB

Don't forget that the prop valves change through the years and on ABS / non ABS. My car is a 2000 with ABS. The brake balance on my car is waaaay better than my former 1997 without ABS.

It's not that simple. The prop valve is a 2-line segment approximation of a sideways-hyperbolic-looking curve.



3 parameters describe these 2 lines:
1) slope of first line
2) slope of 2nd line
3) location of knee

An adjustable prop valve only adjusts 1 parameter, the knee location. In theory you can adjust the other 2 parameters by diddling the front and rear brake pad friction coefficients.

The ideal curve is a function of car's weight distribution, wheelbase, and CG height. Note that the tire's grip does NOT affect the shape of the ideal curve.

With the ideal curve, you always get the right proportioning regardless of surface, from ice, to race tires on hot concrete. Front and rear will lock up at the same time.

The problem is when you use a prop valve which is a 2-segment approximation. As you can see there are only 2 points where the prop valve is exactly correct, where it touches the ideal curve. Everything else is a compromise. What part do you compromise? Hot concrete? Rain on shitty tires? Snow?

It is possible that for a given adjustable prop valve, which only has one adjuster (and not 3), that the slopes are wrong, and so you would have to adjust the **** for different levels of grip. And it is possible that for one setup, rain required the **** turned down, and on another, it requires the **** turned up.

Here's a long discussion. Pay special attention to the posts by Jon H:
[NA] Brake proportioning math - MX-5 Miata Forum

JasonC SBB

Here's more

arbinshire

Any idea if this would work with Konig Heliums?

hustler

iTrader: (6)

Jason, I don't think you can understand the difference until you've driven on the track with a proper tuned brake bias.

Laur3ns

I want to know how this is for ABS cars.

hustler

iTrader: (6)

I've driven my sister's MSM on the track and it could use significantly more brake in the rear.

JasonC SBB

Hustler, with Cobalt GT's (high c.f.) front and rear my car is slightly unstable braking hard from 100 -> 50 (or so) entering turn 14 at Thunderhill.

On the street Cobalt GT's front and rear will easily induce oversteer in trail braking.

My conclusion is that I don't need more rear bias with the stock brakes, if I use high cf pads front and rear.

BTW in the MF thread, I explained why increasing the c.f. of both front and rear increases rear bias.
With stockish front and rear pads, yes, it needs more rear bias.

JasonC SBB

Here are the Dynalite calipers
Wilwood Engineering - Forged Billet Dynalite Caliper

Can someone measure the approximate distance from the spindle to the middle of the pad on the Corrado rotors?

JasonC SBB

I eyeballed my '00 brakes. Radius from spindle to center of pad appears to be 3.9".
Because the Corrado rotors are 1" larger in diameter, I will assume their radius is 4.4", or about 13% more. So the piston area of the Dynalites will need to be 11% smaller to maintain the bias.

If the 94-00 stock piston dia is 2.00", then the dynalites would have to be 1.33".

The 1.38" dynalites would have 10% more front braking than stock.
The 1.25" dynalites would have 12% less than stock. This may be a good choice for those that want more rear bias.

I would go with the latter, then fine tune the bias with the rear pads. Because the front pads need to be more aggressive anyway than the rears, this may be perfect, by using a milder rear pad.

JasonC SBB

Oh, and do Carbotech make XP12 pads for these Dynalites?

Savington

iTrader: (31)

Ideal curves are great in theory, Jason, but in the real world we have to deal with factors like changing pad temperatures (and thus changing coefficients of friction) and changes in traction between the front and rear tires. If you obtain that perfect bias with pad material and piston sizing, you WILL spin your car eventually - I guarantee it. Race tracks are not magical lands where the pavement is absolutely and utterly smooth - if you take a "perfectly" biased car into a rough, bumpy braking zone, eventually you will lock the rear tires, and a locked tire does not easily unlock - and presto, you're backwards into the soft stuff.

No part - you adjust the valve for your conditions. In the rain, you want a car with more rear bias (knee moved up) because even though the 1:1 curve might exceed the ideal curve at some point, and rise up into the no-man's land (rear lockup), by the time you've applied that kind of force to the front brakes they've locked up due to the reduced traction conditions.

The slopes are always wrong with prop valves, though - they are lines and not curves. They have to be wrong, because if they weren't wrong people would spin their cars left and right for the reasons I mentioned above.

I don't think this is possible. If you look at those curves, it's possible to set the knee so high that you get rear lockup. If you set it perfectly (such as in your first chart) and then reduce traction, you will always lock the fronts first, and it will get worse for a while, and then better. Bring the knee up by increasing rear bias, and the 1:1 line gets closer and closer to the ideal curve - thus, better bias. If you need to turn the rear bias down (move the knee down) in order to get closer to the ideal curve, I would suggest that it was *way* too high to start with.

At the end of the day, there's also empirical evidence. I've used XP12/10s in stock brakes and the fronts lock first. I've used XP10/10s, and the fronts lock first - to the point where I can apply so much pedal force that the backing plates warp, and the rear tires never lock. This is all on stock 1.8 brakes with a stock proportioning valve.

Also - Wilwood doesn't make a 1.25" piston Dynalite. They claim in their description of the caliper that they make a 1.12, but I can't find it for a .81 rotor width. They make a 1" caliper, but it's a totally different caliper with different mounts, and only for a 1.25" wide rotor.

Carbotech does make an XP12 for the Dynalite, yes - I am using XP12s front and rear right now. I used to run 10s in the rear, but switched to 12s because the friction coefficient is higher, which provides more rear bias and keeps the bias **** from needing to be set fully in.

Laur3ns

Do people actually mount that thing in the car and fiddle with it because their fuel level is lower? I ordered one and tend to fit it near the OEM location and not fiddle with it much after tuning. Same reason I don't have adjustable suspension, you keep blaming it.

Laur3ns

From the FM kit - I assume you are using the same?
Bore size: 1.38" (35,1 mm)
Disc width: .81" (20,6mm)
Wilwood Engineering - Forged Billet Dynalite Caliper

Laur3ns

Uhh
2" dia = (2/2)^2 * pi = 3.14 sqin
2x1.38" dia = 2 * ( (1.38/2)^2 * pi ) = 3,00 sqin or 4% less.
Or not?

Savington

iTrader: (31)

One of our first buyers backed out, so I have ONE kit available at the $550 price. Send your Paypal address and shipping address to sales@trackspeedengineering.com and I will reply with a shipping quote and total.

hustler

iTrader: (6)

I just sent you money, ------. Tone down the disrespect or I'm going to send you fake billing information next time.

Die of aids, high-pressure salesman.

Oscar

iTrader: (2)

I did. Hasn't changed much since I dialed it in at Zandvoort. It sure is easier than pulling over, popping the hood, adjust and try again tho...

chpmnsws6

iTrader: (12)

You should give a few more people the 550 buy in price...... It'd make me ditch the 949 upgrade I currently have a bit faster

62704 for shipping quote

Laur3ns

This kit is só worth the $650 he's asking.