poor braking

[r3gill]

Hi all, I bought an r32 gtr last year. Car has been great so far but there's something that always worries me. When i drove this car first time brakes seemed to be fine but somewhat weak then most of the cars i've driven so far that incldes r33 gts-t which locked wheels with hard braking.

So I stared troubleshooting and here's the list,

Check brake fluid
check brakes and rotors were worn so they were replaced with brand new ones all four wheels.
Now it seems to stop a little better but never locks the wheels unless I am at really slow speed. I know it's got abs and the wheels shouldn't lock but you can feel the abs working when it begins to lock.

Pedal feels very strong not spongy at all but still nowhere near the braking my dd has.
perhaps a brake booster?
need some advice

Thanks,
Rob

[GTR-Dad]

Pedal effort is quite high on my car, but if I push hard enough wheels will lock.
Does your pedal bottom out or do you lack strength in your leg? (Jk!)

New rotors and pads will take a bit of time to wear in and provide the braking force they have the potential to. Different pads have different 'bite' characteristics too. Which ones are you using?

Good fluid mainly increases boiling temperature, but doesn't affect braking force at modest temperatures.

Dan

[r3gill]

Pedal effort is quite high on my car, but if I push hard enough wheels will lock.
Does your pedal bottom out or do you lack strength in your leg? (Jk!)

New rotors and pads will take a bit of time to wear in and provide the braking force they have the potential to. Different pads have different 'bite' characteristics too. Which ones are you using?

Good fluid mainly increases boiling temperature, but doesn't affect braking force at modest temperatures.

Dan

thanks for a quick reply Dan. No lack of strength in the leg infact even if i stand on the pedal it won't bottom out like it will do if there's air in the system and won't lock the wheels. working and driving on various cars over the years I can tell there's something not right. I am using stock rotors and lordco reybestos brake pads and been driving it since last summer.

It's hard to explain. I mean gtr's are heavy but brakes should definitely be stronger then mine. my 1400kgs dd with haft the size of gtr's rotors will stop in less distance then my gtr.
would like to hear more.

Thanks,
Rob

[frankiman]

have you tried better brake pads?
because lordco just seems like a cheap OEM replacement

but also check the brake master, the booster might be blown, or a vaccum hose leading to the brake booster might be cut/disconnected
seems like the most plausible cause

[r3gill]

have you tried better brake pads?
because lordco just seems like a cheap OEM replacement

but also check the brake master, the booster might be blown, or a vaccum hose leading to the brake booster might be cut/disconnected
seems like the most plausible cause

a cut/disconnected vacuum hose will feel like an old manual brakes. It still has power brakes but not strong enough. Car had same problem with old nissan brakes. So all those causes are ruled out. Brake booster sounds like a good cause but how do i test it?

[markc32]

u didnt replace the pads? only rotors....i always replace both so i dont look back....start with new decent pads since u have new rotors....check leaks....no leaks..then ur calipers are in need of rebuild...

[r3gill]

u didnt replace the pads? only rotors....i always replace both so i dont look back....start with new decent pads since u have new rotors....check leaks....no leaks..then ur calipers are in need of rebuild...

please read. pads have been replaced. and when i replaced brakes calipers had no leaks and were't siezed so i don't understand why will they need to be rebuilded.

[Skym]

Car should start to stop with minimal pressing of brake pedal when brakes are working properly.

From memory, bedding in brakes involves 3 sec on and off brake pedal to wear rotors in for 500km or so when stopping (instructions on bedding rotors in was shipped with new rotors). Then do hard stopping a few times from motorway speeds when exiting motorway to degas the brake pads. That's how I bed my cars brakes in and they work perfectly after. That's with new brake pads and new rotors.

With faulty brake master cylinder, brake pedal will travel to the floor more and car gets harder to stop. If you look under brake master cylinder you'll probably notice a leak (sometimes there isn't a leak). The cause of this failure is not servicing brakes properly (changing fluid) that destroys the seals inside brake master cylinder. Pump brake pedal a few times until it feels hard and see if brake pedal goes to floor when you press brake pedal one time after pumping brake pedal when engine is off.

If brake hoses are a problem (bubble inside but not leaking), you'll notice one rotor is worn more than the others and hear a dragging sound from that corner, etc. Brake hoses should be changed every 4 years as part of routine maintenance. They either leak at caliper side or bubble inside.

For brake fluid you should use at least Dot 4 brake fluid (I use 600+ degree racing brake fluid in my car). Same brake fluid as used on GTR's for racetrack or Targa use.

[markc32]

please read. pads have been replaced. and when i replaced brakes calipers had no leaks and were't siezed so i don't understand why will they need to be rebuilded.

oooops! but yeah raybestos...no good man

[r3gill]

Car should start to stop with minimal pressing of brake pedal when brakes are working properly.

From memory, bedding in brakes involves 3 sec on and off brake pedal to wear rotors in for 500km or so when stopping (instructions on bedding rotors in was shipped with new rotors). Then do hard stopping a few times from motorway speeds when exiting motorway to degas the brake pads. That's how I bed my cars brakes in and they work perfectly after. That's with new brake pads and new rotors.

With faulty brake master cylinder, brake pedal will travel to the floor more and car gets harder to stop. If you look under brake master cylinder you'll probably notice a leak (sometimes there isn't a leak). The cause of this failure is not servicing brakes properly (changing fluid) that destroys the seals inside brake master cylinder. Pump brake pedal a few times until it feels hard and see if brake pedal goes to floor when you press brake pedal one time after pumping brake pedal when engine is off.

If brake hoses are a problem (bubble inside but not leaking), you'll notice one rotor is worn more than the others and hear a dragging sound from that corner, etc. Brake hoses should be changed every 4 years as part of routine maintenance. They either leak at caliper side or bubble inside.

For brake fluid you should use at least Dot 4 brake fluid (I use 600+ degree racing brake fluid in my car). Same brake fluid as used on GTR's for racetrack or Targa use.

sounds good skym. No problems with the master cylinder IE no leaks, pedal traveling all the way to the floor, bubbles in the reservoir etc etc. Pedal feels very firm and normal. Problem is when full pressure is applied to the pedal car doesn't stop the way it should. It almost feel likes I have to start applying brakes way before I would on any other car. weak.

Car had same problem before I did a complete brake job. So I guess bedding isn't a problem here.

Is there something else I can check for? Is there a way to check the brake booster? a weak booster can cause this for sure.

[Skym]

Could be the brake pads used, as mentioned above. Have you bleed the brake system correctly, as that can affect braking. Bleeding ABS is totally different to non ABS, as it requires compressed air driven bleeder, not the pump the brake pedal technique with bottle that you move around to each corner. Sometimes the ABS unit on passenger side of engine bay near firewall can play up, leak and needs overhauling or replacing. Rare to hear about booster failing, unless car has done high km.