richardjh

Hi folks.

We all know the Ralliart's front brakes are pretty small. It's a heavy car, and once its engine has been "un-de-tuned", those brakes work pretty darned hard.

One option is to upgrade to larger rotors, better calipers, etc. However, I didn't really want the hassle of going through this. Not just yet, anyway.




So, for now, I'm going for the "traditional" approach. I got my Ralliart fitted out with some slotted DBA 4000 series rotors, along with some Pagid Blue pads and AP Racing DOT5.1 fluid. A few notes on this setup...

• The DBA 4000 series rotors I have are slotted (not drilled). They have thermo-graphic paint on them, with three different temp readings. More on that later.
• The Pagid Blue pads are a brilliant compound. I've used them for years... never before on the RA, though. They are expensive! For motorsport pads, they are very well behaved on the road - usually quiet, good bite when cold. Extremely dusty, though.
• The DOT5.1 fluid was brand new, bled through very thoroughly indeed.
• I'm still on stock brake lines.
• Pads and rotors were bedded in properly.

Pagids: http://www.pagid-brake-pads.co.uk/pr...rbon-based.php

Rotors: http://www.dbadirect.com.au/6x6-wiper-slot

Fluid: http://www.apracing.com/info/index.a...Brake+Fluid_33



For my lap testing, I drove half a dozen 60-second runs, with good cool-down breaks in between. Pedal feel was top-quality, and it was 100% trouble free on these shorter runs.


My tyres are Kumho KU-36 "street and track" friendly tyres, and I have plenty of grip - not quite R-Comp levels of grip, but not too far off. With the GST Base Map (boost pill) tune, the car pulls pretty hard, and I was braking just below ABS every time. Nice and toasty!



The final run was my opportunity to brake-test, so I stayed out for a bit longer.

The brakes lasted for 100 seconds at full noise before braking started to degrade.

By degradation, I mean that the pedal started getting soft. After cool-down driving and being parked up for an hour, the pedal feel was 100% back to normal.

There was no hint of hard brake pedal. I still had all the braking force I had before... but I had increased pedal travel to get there, and a loss of good "feedback" from the pedal.


Edit:

** Update **

Four weeks later, I got the chance to repeat the same test. This time, the brakes lasted the full 130-second course with no degradation. The only difference was that the pads and rotors had worn in better, with the whole surface of the pad now working equally hard on the rotor face. I obviously needed more bed-in effort than I originally gave it!

These brakes feel very good indeed - gotta love the Pagids. Once I find out the new limits on-track, I'll update again.




Regarding the thermo-graphic paint on the rotors. DBA puts the following on their disks...

GREEN paint - after 10 seconds above 458C, the paint goes WHITE.
ORANGE paint - after 10 seconds above 550C, the paint goes YELLOW.
RED paint - after 10 seconds above 630C, the paint goes WHITE.

On both sides, the GREEN paint was no longer its original colour - it had gone WHITE. The other two paint colours were unchanged.

So my rotors had been operating between 458C and 550C. For non-metric types, that is between 856F and 1022F.



Pagid's website says the following for Pagid Blue...

Constant working temperature: 350 – 600C
Max temperature for short period only: 650C





The final results of my little test afternoon...

1. Pad/rotor combination gave great pedal feel.
2. 100 seconds at full noise got me a soft pedal, which was back to normal an hour later.
3. Within that 100-second run, rotors operated above 458C (856F), but did not see temps over 550C (1022F).
4. Either the fluid was pushed beyond its temp limit, or the stock rubber brake hoses got all hot and mushy.

On that last point, I'm tending towards laying the blame on the rubber hoses. I've boiled fluid plenty of times at the track... and the pedal has always stayed soft until the dead fluid was removed by a flush. Having my good pedal feel return as soon as the car has cooled makes me think that the brake hoses were hot enough to expand more under pressure... and that makes me think braided hoses.

I've used braided hoses before, and loved them. Awesome feel, and far better resistance to that loss of firm pedal after getting the braking system really toasty.

I'd like to see the condition of that fluid when I flush through new DOT5.1... but I'll probably go for braided lines just to be sensible.



Hope this is useful info!


Cheers,


Rich

mikesim

Excellent info!

By the way would the rotors need replacing if the hottest reading turns white?

richardjh

I'll let you know if I get there!

I've tortured DBA slotted rotors for years, and never replaced them for reasons other than just plain "used up". They have always performed brilliantly.

Rich

evo_soul

DBA rotors are probably the best rotors available for the Ralliart. Very good quality.

richardjh

One other thing...

After washing the car and getting a bit of spray on the wheels/brakes, a difference in front rotor surface was apparent. The inner 2/3 of the rotor is mirror-smooth, but the outer 1/3 has a rougher texture.

So it's quite possible my front brakes need a little more time to bed in to their ideal pad face "shape", ie. so all of the pad is working equally hard.

I do realise that the RA calipers aren't competition-quality in terms of rigidity, pressure distribution, etc. They are road brakes, and rather average ones at that. Still, if the inner 2/3 of the pad works harder, it'll get worn faster, and after a little while it should even out.

More even pressure, wear and temp across the pad face? It can only improve from here...

...and the next time, my pads will definitely have seen those temps before. My bedding-in procedure just didn't get to the on-track temps - something I need to address the next time I go through this. I reckon a little more prep work would have paid dividends... You live and learn!

Rich

Laza

Nice writeup. Did you ever perform the same testing with the stock brakes?

richardjh

I remember trying "100km/h to 30km/h" hard stops on the stock pads and rotors. Managed three before the pedal went rock-hard! Imagine the fun of a spirited drive in the hills...

On some cheap performance pads (Aussie brand: Queensland Friction Materials' A1RM compound), they survived 80 seconds on-track. At that point, the pedal went rock-hard, and I lost all braking force. That happened quite suddenly... and resulted in me going straight off the track, transitioning neatly from driving to weeding. :P

Just by slapping some Pagids (and better rotors) on, I got to 100 seconds, with:

• No "hard pedal" at that point... just a progressive increase of pedal travel. No loss of braking force.
• A prospect of better braking performance next time, as it seems 2/3 of my pad-rotor surface did all the work. They need more time to bed in, so the whole face works equally hard.
• Stock brake lines - just the factory rubber stuff.

Plenty more "traditional" tricks to try - braided lines, removing the backing plates for more airflow, fitting plastic "duct" style airflow guides, etc.

Stay tuned!

Rich

BravoZero

iTrader: (2)

Very cool. Looking to upgrade my brake setup in the future, this is useful!

Ishi22

Rich - did you get the DBA 4000 rotors on just the front or on the rear too? I'm trying to find a part number for the rear rotors, if they make the 4000 series for the Ralliart.

Thanks

richardjh

Hi - answered your pm.

For the record, no - all I did was put some cheap uprated pads on the rear. I don't expect them to wear very fast, and I don't anticipate any heat issues at that end. My last track+street car went through six front rotors for every rear rotor... and probably a similar ratio for pads. Most of the braking effort happens at the front.



I'll be giving the pagids another try this coming week - same course. If weather conditions are similar (ie. dry), I'll see if they perform better - now that more bed-in has been done.

Also... to hedge my bets, I've bought a set of NFS' Vette caliper brackets! Once I've worn out these pads, I'll decide which way to go.

Rich

03chi-town0Z

iTrader: (7)

Great information. Much thanks for taking the time.

Don't be too hasty to jump on the big brake bandwagon, though. Based on everything you've said, those rubber brake lines are what's killing you, imo.

Get some braided lines and then see how long you can push it without issue. I'm willing to bet you'll be able to add another 15-30 seconds of time before you start seeing the same performance drop-offs you were seeing after 100 seconds on the rubber lines.

richardjh

Yeah, we'll see! I can also switch from the AP Racing DOT5.1 to PBR "Racing DOT4". While DOT5.1 is "usually" regarded as "better" than DOT4, it all comes down to the boiling points. And the PBR stuff is rated higher in that department.

http://www.pbrperformance.com.au/RacingBrakeFluid.htm

NFS' caliper+bracket+rotor stuff can use the stock brake lines. That means any braided replacement can be done now, and remain in place for a bbk.

Come hell or high water, I'm sticking with the current set until it's worn out. So I'll be able to play with a few things and compare...

Rich

2muchboost

iTrader: (10)

Could you post the part # for those front rotors.. I cant find them

Thanks!

richardjh

http://dba.com.au/products/DBA4417SL
http://dba.com.au/products/DBA4417SR

Rich

richardjh

** UPDATE **

Four weeks later, I got the chance to re-test.

No changes whatsoever, except for the brakes being worked on-road in the interim period.

The weather was dry again - similar conditions all round.


This time, I completed the practice course without any loss of braking force or pedal feel. Elapsed time of course: 130 seconds.


That's heading in the right direction!

The Pagids are feeling great. They really pull the car up nicely. Pretty grindy-sounding after being used lightly on-road, but I can handle grindy. It's squeaky I can't cope with... and they don't do that.

I'm now interested to see where the limit really is with these pads/rotors.

Note again that this is all stock size components, stock rubber lines, behind-disc dust-covers still fitted on the hub, etc. Just good fluid, good rotors and rather expensive motorsport pads!

Rich