Downgrading my Brembo GT Kit

SON240sx Automotive
1

I’m considering downgrading my Brembo GT front brake kit. I’m all about useable power, useable mods, and useable braking power, and I just don’t utilize the kit 100%. The brakes are large, and I’m sure are designed to withstand full day track events without fading, but realistically I won’t be doing that any time soon.

Right now, I push the car hardest at AutoX every weekend. I’ve been playing with some of the setup, and I’ve seen some improvements that I need to make with the car. The front brakes however are more than the car needs to perform at its best, so I’m thinking about trying another setup.

Right now, I run into the problem of the front inside wheel locking up with minimal pedal pressure on the track during heavy braking. My problem is that I can’t hear them locking up, and usually can’t feel it, as they don’t fully lock into a slide when this happens. The wheel locks for a second and it smokes the tire a little entering the corner, costing me time and r-comps…lol. I have noticed, even on the street sometimes, that when I get into the brakes, they can fully lock up pretty easily if I don’t modulate correctly.

I’ve bled the brakes a bunch of times and went back to the “stock” Brembo pads from the Endless Blue track pads, but the brakes are just way overpowered compared to the rears. I don’t have ABS, but this is happening at minimal peddle pressure, so there’s more going on than just driver error…i.e. I’m not mashing the brakes. I’m probably not the best driver out there, but I do have enough seat time to know how to brake properly.

I haven’t tried any brake bias valves, and I have no experience with them, so if anyone can school me a little on their effectiveness, I’d love to hear it. I obviously understand what they do, but I just wonder if it’s the bias that’s causing my issues or just too much braking power. If I were to guess, I’d say that a little rear bias wouldn’t hurt my overall braking setup, but even with the adjustment, the GT kit may be more than I need.

What are your guys thoughts on some of the popular brake upgrades for the 240SX. I used J30 calipers and Cobra rotors last year with my Maxima, and I liked that setup a lot. It was a great improvement over stock, and didn’t overpower the rears a whole lot. It was “just right” for that car. I have some Z32 rears and the 300zx MC, maybe some Z32 fronts would do the trick. I haven’t ever used the Q45 brakes either.

What are some of your setups, and your opinions of them? Maybe getting a set of bias valves for the front lines, and re-installing the ABS system will help out a little. I’d like to hear any experiences using proportioning valves on our cars, and any advice.

I guess if all else fails, I could sell these brakes and try out something smaller. Although at an MSRP of $3195.00 US, I’m not sure I’d find a lot of people willing to pick them up right away…:stuck_out_tongue:

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Bias valve would help a lot with that issue. Most BBK’s have that issue where the front ets teh insano power. Try it out, a 60 dolla valve may be exactly all you need to fee l like you can utilize it all. :slight_smile:

Dude. My biggest regret of selling any parts i’ve had, the Wilwood BBK and they’re not even in the same league as yours.

3

So about installing a proportioning valve…everything that I’ve read up on is basically for cars that have undergone rear drum to disc conversions, and have too much rear bias. The valve will then dial down the rear pressure for a better front bias.

The problem that I’m having is exactly the opposite, I need less front pressure. I think that our front brakes have two separate lines coming from the oem “bias or combination valve” no? The obvious thing to say is install two proportioning valves in these lines, but I’ve also read that you should never install a proportioning valve in the front lines.

I don’t see why you couldn’t install dual front proportioning valves, the only problem I can see is tuning them to both react with the same pressures, which may be difficult. It would be great to hear from someone who has done this, and see what they say about it.

Am I incorrect in saying that our cars would need dual valves, is there another place in the line that would capture both fronts and not bump down the rears?

4

I wouldn’t ditch your bbk setup id adjust the valving and consider more tire front and rear. Pretty much a waste to downgrade… honestly…

If you are building a purpose built car for autox… you should get some lightweight willwood calipers and very small rotors… the ones that look like bike rotors (no joke)… super lightweight… I mean an autox session can’t last longer than 2 minutes more or less… mostly 1 minute runs… so… then again depends what class ur in but still.

If you still want to street your car or go road racing then… gotta make compromises my friend…

I wouldn’t go back to 20 year old oem junkers though…

5

Yeah the car is definitely a daily driver. I don’t think I’d ever run those tiny rotors with it.
I just need to find some useful info on the proportioning valves, and find out if I can indeed use them…and with 245 fronts, I can’t really go much wider without getting into other clearance issues.

Does anyone know where I can get some ABS rings for a 5-lug?
Haven’t seen them on most online oem part supplier websites.

6

You kidding me? 245s and trouble on an s14? Maybe you’re just too low… I run 255s on my s13… 285s can be fitted under stock fenders on an s14… with 18x10+20 wheels no spacers… This guy autocrosses in the states in SM class with the following height/setup though:

You should definetely be able to fit more tire!!!

http://i114.photobucket.com/albums/n247/AceInHole/Panda/DSC_4371.jpg
DSC_4371.jpg800×532

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He is much lower now though:

http://farm4.static.flickr.com/3461/3718377799_f1faa473d9_b.jpg
3718377799_f1faa473d9_b.jpg1023×678

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I’m not as low as that, but I do rub the fronts occasionally at full lock while cornering. Slightly cut splash guards tell the tale.

I also rub the rear sidewalls occasionally when the trunk is full of jacks, r-comps, tools, etc. going to an event. White streaked sidewalls tell that tale.

Here’s a pic of my rideheight.

http://farm4.static.flickr.com/3356/3516359331_a5fc9488f0_b.jpg
3516359331_a5fc9488f0_b.jpg1024×679

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Actually, here’s a better pic, with the exception of me running more caster and much more camber now.

http://i204.photobucket.com/albums/bb101/Puddincole/Kouki%20S14/IMG_1858.jpg?t=1247746905
IMG_1858.jpg?t=1247746905751×500

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I use the 30mm 300zx calipers and rotors with no issues…its really the pads that make the difference…I use hawke ht-10 race pads…

running on 275’s up front and 315’s in the rear

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are those SportContact3’s?

i’d say, if you haven’t already, to change your tires as part of your brake revisions

you won’t lock up hoosier A6s nearly as easily as you will those conti’s

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What are you rubbing on? Investigate that… and that’ll solve your problem. I was rubbing initially too but I took care of the problem (mwahahaha).

You can DEFINITELY stuff more rubber… and not rub. I run 8.5 front caster… so talk about rubbing (initially).

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Yeah they’re Contact 3’s, but I don’t race with those.
I race with BFG g-force R1’s on Enkei rpf-1’s, and they lock up on the track.
That’s where I noticed it.
The Contact 3’s were basically new in May, but they’re about shot now.

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The tires rub on the top of the splash guard, and have actually just poked through to the windshield washer plastic clip on the passenger side.
I also noticed the other day that the lower control arms are slightly notched on both sides, and looks like new metal…i.e. not purposely notched and rusted over. It would almost seem that my rotors are just contacting the lca’s at full lock, but the rotors are mint, so I dunno. It might be just kissing it or something…I was rushing to get the wheels back on after the day to make the ferry, so I didn’t investigate much.

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so u have a couple of different issues.

What do you mean by splash gaurd? You mean you STILL have the plastic inside covers?! Remove those! Anyone who runs aftermarket wheels tends to… as it’ll definietely rub on that. My next enemy in line is the wheel wells… I need to tub mine to fit anymore (and go lower – unless i reduce caster which so far i dont want to).

You should DEFINETELY be able to fit more rubber. 275s are not a problem on an s14… 255s are a piece of cake… so there’s something definetely going on… if your rotors are touching metal… u got bigger problems to worry about.

If you still have those plastic inner linings, remove them… thats your problem then.

16

I don’t have the plastic liners that say run from the bumper up into the wheel wells, but I do have the plastic bits that sit right up in the top of the wheel wells. Honestly, there’s not much room to be saved by removing them, they’re flat plastic liners, and things tend to run through there that I’d rather not have my tires rubbing off of. The windshield washer routing is one example.

Besides those, no, I don’t have any plastics running under the car. If I weren’t always tearing into the car, I would probably put the bottom splash guard back on (the one that runs under the engine), it keeps the engine bay cleaner, and unless you’re wrenching on the car every day like me, there’s no reason to remove it.

My fenders are rolled, so I don’t have that issue, but the rears for example poke out, and therefore when I have an extra couple hundred pounds in the trunk, and I’m driving the car reasonably hard as usual, they do rub…the only way to get around that would be to jack the car up higher, or sink the wheels in.

http://i204.photobucket.com/albums/bb101/Puddincole/DSC_1220.jpg
DSC_1220.jpg1023×685

There aren’t any big problems with my suspension…given that I drive the car as it was prepped to drive almost daily, I’d know if something were wrong. Not sure what’s up with the exposed metal, but it’s tiny and it doesn’t give any driveability or reliability issues, so I’m sure it’s not going to cause any issues. I’ll obviously keep an eye on it, and check it out the next time I have the wheels off.

I’m sure I could probably run wider tires on the front, and if I jacked the car up a little, i could probably run much wider tires on the front…but we’re getting a little off topic. The braking system is not working as I would like it to…regardless of the tire size…so I need some answers about that…lol

So has anyone ran a proportioning valve on their S14 to eliminate a large front bias?
Does anyone know where I can grab some 5 lug front abs rings?

17

I guess it’s worth noting my alignment specs, since it’s came up a few times.
Before this week, I was running a driveway alignment…quite well actually…but I got a proper alignment earlier in the week. No big changes, just setting everything to match on either side.

Front
-3.9 deg camber
7 deg 20’ caster
2.8mm toe out

Rear
-2.5 deg camber
0 deg toe

When I brought it in…after playing with it at AutoX to dial it in a little myself…these were basically the camber settings all around. The toe was all fkkd and the caster (which I didn’t touch) was at about 6 deg 20’. I hadn’t planned on the -3.9 deg front camber, but it worked at the events, so I went with it. Some people stick to less camber on the rears, but I hook up just fine, and cornering is more important to my setup anyway.

I haven’t had it to an event yet…double header this weekend, but it feels pretty good so far. If you’re wondering about the unusual toe measurement, it was going to be 1/8" out (3.175mm), but this popped up on the machine, so I just left it as is. A little toe out helps, and the 0.3mm difference is pretty negligible.

18

Well do this… have someone while stationary move the steering wheel car left/right and observe where the wheel is rubbing/hitting… Of course under compression it may be more pronounced but this should give you an idea.

I don’t know man, I’d have to see it in person :-/… Plenty people run much higher tires… and even I do with my s13… 245s are shorter than my 255s and my 255s are larger than 255s… as azenis run wider than most tires…

Go to zilvia and check maximum rubber thread, I created that thread for maximum wheel/rubber fitment… plenty ppl who run 275s up front…

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I’m sure I could find a way to get more rubber in there if I tried. The touching issue is very intermittent and doesn’t do any damage, so I’ll worry about the brakes first…lol

Anyone have feedback on their brake setup, or proportioning valves?

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Haven’t had time to read through the thread yet, and probably wont get to it for a bit, but the concept seems pretty sweet. Good job man.