GTi-R BRAKES

[CMF_GTRHOLIC]

Hi all, i just fit gtir brakes to my micra super s. ive fitted endless ccm pads and new slotted rotors. by the way, endless REAR pads for the k11 DO NOT FIT THE UK/AUS SPEC MICRA. always learning the hard way. anyway, my question to all is, the pedal feels really spongy, ive called the forum guru TOM and he has attributed the spongy feel to the larger piston in the gtir caliper. should this be the case? the car does stop and stops quite well, however, the initial push of the pedal feels as if it doesnt do anything. please help.

 

[CMF_Geoff W]

Tom's explanation sounds feasible. The only other suggestion is that there might be some air in the brake fluid. Try bleeding the system extensively and see if that makes a difference.

I once had a similar problem with pedal feel with the standard brakes. So much so that i suspected the Vacuum booster diaphragm had failed. I helped my friend/mechanic bled the brakes and hey presto I had a pedal back.

 

[CMF_Sean]

Bleed properly and it will be fine. Pedal feel in my old Micra was exactly the same.. If the problems still there consider your brake lines are over 11 years old now and they weren't the best quality stuff to ever come out of the factory. Also, make sure that the pads are heated up well enough too, the EBC greenstuffs I used to have would be absolutely horrible for the first 2-3 min of driving but once warm would lock up VERY easily and the pedal feel was great.

Process of elimination:

1. Bleed brakes
2. Braided lines
3. Master cylinder stopper (home made or bought)
4. Experiment with larger MC's

Sean

 

[cisco]

I always complained about the same thing. After extensive bleeding, I realised that I had already bled the brakes pretty well, so I didn't get much of an improvement.

The GTi-R brakes definitely do have larger cylinders and I am pretty sure this is the problem also.

On a Super S, the brake lines are considerably longer and more convoluted because they have to go right round and through the ABS system, which absorbs pedal energy and oil volume, then additionally you now have larger cylinders in your calipers.

What worked for me was when I removed the ABS system, but kept the original Super S ABS master cylinder. Because this is a more powerful booster than the non-ABS ones. So you're left with the more powerful booster, that now doesn't have to lose any efficiency through the ABS system. My pedal feel definitely became awesome with this configuration. But removing the ABS was a fairly large job. Plus I needed an expensive engineering certificate to make the car legal again - but YES you can get a car with its ABS removed legally engineered to pass rego.

Hope this helps..

 

[CMF_Brendon]

get a larger brake booster to help.

 

[CMF_Yom]

I don't think its a master cylinder or booster problem at all. Plus I don't know about chris but its a massive stuff around to unbolt the booster and master cylinder and play around with items from other models. I have no doubt something might fit from another Nissan but honestly the task is too big. Bloody easier to ditch the gtir brakes which really arent all that efficient in their task anyway in favour of some nice 2pots from a z31/r32 or something. there's adaptor kits and discs being made up for n13/14/15 pulsars around Aus now so they'll work on the AU/UK Micra.

-Braided brake lines
-Better fluid (NEO Gold brake fluid has claimed to reduce the pedal soggyness the pulsars also get when upgrading to the GTiR/N15 SSS brakes - the pulsar people who are using it absolutely love it)

Thats all I can think of right now.

 

[CMF_ed.]

Motul RBF600 brake fluid if you haven't already used it.

 

[cisco]

Sorry I incorrectly said "more powerful master cylinder", but I meant "booster" - I have edited my post to reflect.

I have heard from a few people and a brake shop that braided lines are more of a myth, if your factory lines are in good condition, then there's no compelling reason to upgrade to braided ones. Autospeed did a comparison test on them a while back and basically proved that there wasn't much point to upgrading that part of the line. Braided lines are like a rice boy performance item to check off the list so your car looks "hotter" and more "race ready".

I definitely agree that the GTi-R brakes are probably considerably overrated for a micra. I never got the N14 1.6 brakes to fade once! Those work great in my opinion and are much lighter than GTi-R brakes. The GTi-R brakes were unstoppable, but they also made my car handle a bit worse and respond to bumps a lot worse. You can really notice when you rip them back off and put tiny factory brakes back on. Next time, I would probably just go for N14 1.6 brakes as they are (a)cheaper (b)lighter (c) still powerful enough. Maybe for pure track work on a powerful turbo setup then the GTi-R ones would be perfect, but probably overkill on the street.

 

[CMF_Yom]

Rubber deteriorates as it ages. The Micra's +10yr old rubbers would be starting to feel the effects of age by now. So its not a bad upgrade which sort of kills 2 birds with one stone.

No good if you don't eat the 2 birds at once though, if you get what I mean.

 

[CMF_GTRHOLIC]

im using a dot 4 castrol hi-performance fluid. meant for hard braking. i dont think the braided lines will make a huge difference in the way of initial bite. even though the pedal feel isnt the greatest, i feel the braking control has actually improved. does anyone agree?

 

[CMF_Yom]

Personal preference I think.

My brake pedal became a bit squishy after putting the N15 1.6 calipers on, which have a considerably larger piston than the stock brakes and even the n14 1.6 and 2.0 calipers. But braking performance improved and I do feel the pedal is more progressive than it was beforehand.

I changed fluids twice. Was a grave mistake. Went from some Fuchs Dot4 stuff (which was purdy blue) to some Nulon 'super dooper ultra high performance for your driving pleasure' and lost brake pedal response. The fuchs definately provided better brake pedal action.

 

[CMF_evade]

i had n16 1.6 calipers/rotors..and they were the best brake setup for me..i could stomp on them so damn hard..and abs was well behaved and wasnt very obtrusive either...if i really mashed them then they would kick in..but rarely did..it just stopped..

big difference. my 200sx comes on ABS so damn easy..

 

[CMF_Yom]

note to viewers, i think aaron made a typo there as n16 have a different hub mounting and stud pattern to k11/n15/n14/n13

 

[cisco]

mmm 200sx

 

[CMF_Nissanmania]

I'm puzzled by some of the points raised here.
1. The amount of convoluted lines through the ABS system shouldn't make any difference to brake feel as these involve solid lines with zero wall flex. They may however pose a potentially greater air trap meaning more bleeding is required to get this out. Deteriorated rubber brakelines though, could have a big effect on increasing pedal sponginess.
2. The type of brake fluid shouldn't affect brake feel until you reach that brake fluid's boiling point. This is unlikely to occur on the street unless coming down a mountain pass or doing multiple stops in rapid succession from 100km/h+.(Or there's heaps of water in your fluid.) Better brake fluid just has a higher boiling point but they should all be 100% incompressible till that point.

I have N15 front calipers with ABS but have had no sponginess. I do have braided lines though so it may be worth getting some new lines or upgrading to braided ones to eliminate ballooning of the lines.

Otherwise I'd keep bleeding the system to flush out bubbles trapped in the ABS system and the associated convoluted lines.

 

[CMF_mipcar]

Not quite true, in the context of type of brake fluid. The full synthetic/silicon fluids have been hotly debated in some of the other forums I am on.

The consensus being that unless filled through a cloth mesh and poured very slowly, also allowing it to settle over (hours), then the silicon fluid holds micro bubbles of air which keep giving trouble.

Also some brakes place will only recommend swapping to Silicon if the cars brakes are completely new as even the slightest residual of old fluid will not mix properly with the new.

Mychael

 

[CMF_Nissanmania]

Silicon fluids (Dot5) generally wouldn't be used in a road car. They're mainly used in race applications for their high boiling point (500F) and stability. Though they aren't hydroscopic if water gets in it tends to bead into droplets which will boil at 100C - not good. This free water could also lead to corrosion though silicons actually prevent corosion. Silicon will also pick up dirt in your system and cause it to sludge. At a risk of contradicting myself, silicon can also absorb gases causing a spongy brake pedal which is one of its major downsides especially in a race application as this gets worse with increasing temperature.

So most of us would be using high end DOT4 fluids (which may be called dot 5.1!) anyway which can still have a high boiling point (446F) without the disadvantages of Silicon fluids.

Once you have put silicon in your system you can never go back to Dot3/4 as they dont mix, much like oil and water. Changing to silicon would require a total sytem disassembly, clean and a pressure bleed to prevent exposure of the fluid to air.

Just to confuse matters, new generation Silicon Esters (not Silicon) may provide all the benefits of glycol and silicon based brake fluids without the downsides.

 

[CMF_Yom]

Unless we can get access to a nissan consult computer I do not believe there is a way to properly bleed our ABS systems. This is part of the problem (unless I can get a wiring diagram and figure out how to 'jumpstart' the compressor so to speak)

The main issue here however is the larger piston size.

 

[CMF_turbo march-rolling shell]

i think that chris should probably get his abs light to switch of on the dash first... that said, rip it out all together, and just get the standard lines from an lx or something. as if the local cunstabulry (however you spell it) will even have a clue that the micra came out with abs. and it should be the last thing he should be worried about on that car anyway.