JDavenport

iTrader: (33)

Preface: My Evo has become a track toy. I'm in NASA DE3 and will probably be running in TT hopefully at my next event. Because I am working towards entering TT, I drive the car pretty hard trying to get better.

Since moving up to NT01's I have found the following issue with my front brake pads:



On the Star Specs I never had this, but on the NT01's I found the increased grip while braking to be quite a bit, so I started compressing braking zones. But I can't keep a hard pedal anymore. On fresh pads, right after seating them, the pedal is rock hard, very little travel. After the first good session, I start getting an extra 1-1.5" of travel and the pedal looses some of it's firmess. I suspect the caliper flex is causing this and the uneven wear. I know the Aluminum looses a great deal of rigidity when it gets hot.

So what is the solution? I'm running 17x9's so the BBK is not an option without new wheels. Are aftermarket calipers in stock size any more rigid (Racing Brake/Stoptech)? My current brake setup:

Girodisc 2-pc front rotors (Curved Vane)
Dba 4000 Slotted Rear Rotors
Binary Eng Brake ducts with 2" hosing
Carbotech XP12's F and R
Motul RBF600 Fluid
Technifit SS Lines
Stock Brembo's

I've had Brake fade in the past and boiled my fluid. This really feels like neither of them. Still have brakes, but pedal travel increases and they are not as firm.

As a side note, this is really screwing with my Heel-Toe, With size 14 4EEE I use the rocker method across the width of my foot and the varying height of the brake pedal under threshhold braking messes with me.

Smike

iTrader: (8)

Or inside piston is sticking some on the top. Impeding an even stoke.

03whitegsr

iTrader: (8)

https://www.evolutionm.net/forums/ev...ace-stuff.html

Possible option for keeping the 17s?

Although, you may want to go up to 18s and a different wheel just to improve airflow? Seems like airflow is the only way to really avoid the issue either way as aluminum does lose a ton of stiffness with increased temepratures. Might want to try and up the tube size on the brake vents and get a good amount of the air pointed at the caliper along with the rotor.

JDavenport

iTrader: (33)

Well, it's evenly tapered across the face of the pad and the same on both front wheels. When using a caliper spreader, they seem to move smoothly.

Smike

iTrader: (8)

For s/g's how does the rotor plane look like? Square?

I think AP had some. But they are likely AL blocks as well.

Wonder if the top pad part is sliding or catching.

JDavenport

iTrader: (33)

Rotors are pretty new Girodisc 2-pc units, very flat and square. Looks like this is not uncommon when Evo's are pushed hard:

https://www.evolutionm.net/forums/mo...ace-stuff.html

Pics from a lot of the track rats in there showing the same thing, tapered wear from caliper flex.

My street pads which have several thousand miles on them are wearing perfectly straight, but they never see the kind of stuff my track pads do. Another reason I suspect caliper flex.

Smike

iTrader: (8)

Word.

Contacted AP? Maybe they can do a caliper and mount bracket that will work with the OE dia rotor? That way you can save the 2-pc.

boomn29

iTrader: (47)

You don't need a BBK at this level; trust me. You could, but that's $2000-4000 you don't need to spend yet. And when you get to TT; that BBK will cost you 2 pts for 'Non OEM Brake Calipers'.

I've seen some of this before too.

First off; get rid of the Motul 600. Immediately. Run the newer 660 they make or run AMSOIL DOT4 or SRF. I do the AMSOIL as several other TT and some racers do. SRF is like $90 a bottle!

I've got a 2" duct kit too; and it's really the bare minimum. Make sure it's as straight as possible and the front openings aren't covered over. And be mindful of not dragging the brake or anything.

Lastly have you ever changed out your seals? I do the fronts yearly - say 15 hard days and they're getting a bit crusty and starting stretch. If you ever pull your pads and the backs are wet, then the caliper seals are leaking already!

JDavenport

iTrader: (33)

Nate, no fluid at all on the outside of the calipers yet. Dust boots are crusty toast, but that happened about as soon as I started tracking the car.

I need to improve the routing of the ducts, I know that. I'll get some of the Amsoil DOT4 and flush with that for the next event.

What concerns me about the pad taper, is after the pads get tapered, the pedal looses it's firmness even before I start a session and get things hot. After the pad picks up taper it only contacts the rotor on the thicker part until you press hard enough to flex the caliper and bring the whole face of the pad into contact with the rotor.

Perhaps pads with more bite would help, require less pedal pressure and reduce the chance of flexing the caliper and starting the taper wear pattern? Thinking of trying the Hawk DTC's.

Got to do something. Main problem is this varying pedal movement and inconsistent bite, really messes with being consistant on the track. Secondly, I'm wearing out a set of XP12's in the front every 10-12 DE3 sessions, which seems high.

As far as points, I'm going to enter TTS, so that doesn't matter. Down here, there is not much difference between TTS and TTA times at most tracks, and with the Evo 8 3-4 gear in the tranny (4 points) and the JDM rear bumper (?? points) as well as other mods I'd have to spend $$$ to demod-remod the car to get it competitive in TTA.

Besides, If a guy wanted to campaign an Evo in TTA, he needs to buy a certain Blue IX that is a well proven commodity

boomn29

iTrader: (47)

It is for sale...

Btw, the altered gearing is just 3pts.

If you're going TTS and don't worry about points, I'd recommend getting a different front bumper and routing some full size 3" hose short and straight. You could work up a cheap front splitter too, even homemade to start. That's all in my plans if I keep the car and goto TTS/ST2 next year. My .02

I run Hawk DTC60's and like them. There's a number of pads that'll work as 'track-only' including ST43/47, Hawk DTC60/70, some CL, PFC01's. I've ran most of them but come back to the DTC60's myself.

First and foremost; good fluid and cooling though. With the AMSOIL DOT4, I went from bleeding every weekend to bleeding like twice a year. I can even drop in new pads w/o bleeding!

Ludikraut

iTrader: (17)

I have the same thing happening in my Evo 8. Never had an issue with pad taper on street tires, but as soon as I started running R-comps (BFG R1 for me), I started to get pad taper and pad knockback. I run Castrol SRF and ghetto brake cooling ducting. I'm going to suffer with it through my next (and final) round of power mods, then I'll be saving up for the AP kit.

l8r)

AlwaysinBoost

iTrader: (17)

Been dealing with pad taper for a while now. Running either xp10s or St43 with Motul or AMSOil barke fluid on either Z1's or RS3's.

Compared to the ST43's, which seem to have more torque with less pressure, it seems the carbos can take a tremendous amount of pressure to get all the torque out of them.

I think in my case braking too hard with the carbos caused my calipers to flex. I would try and push the pedal thru the firewall with the carbos, not so with the 43's. I have to readjust my right foot to NOT brake as hard with the ST43's. My last track day (last weekend at shenandoah) I was way over braking into turn one because I was used to needing a ton of pressure to slow the car down.

JDavenport

iTrader: (33)

Yeah, this really started to be an issue when I went to the NT01's. Much less of an issue on the Star Specs. But the first time out on the Nittos, I was floored by how much harder I could brake without finding ABS.

Going to A6's for TT soon and this will just get worse.

But, Now I am also wondering about pads with higher mu taking less pedal effort (and therefore less caliper flex?).

Seriously thinking about the AP system......

barneyb

Before spending money in an effort to solve a caliper flexing problem I would want to check if it actually exists. With the car on stands I would expect that there would be some measurable movement of the caliper at full pressure if this is happening.

03whitegsr

iTrader: (8)

Anybody used heat paint on the calipers to see how hot they actually get with various power and grip levels?

If the aluminum is getting to 300F, the metal is losing about 10% of it's stiffness and 20% of it's strength. Get it up to 400F and it's down 15-20% on stiffness and 60% of it's strength is gone. The strength is actually the bigger concern as you may actually be permanently deforming the caliper at high temperatures.

Have you measured the calipers piston faces to see if they are still parallel?