Poor braking performance :S

[dmad_dood]

My na8 seems to have incredibly bad braking performance.. Brand new hawk hps's helped a little bit but still overall pretty shocking. Very low bite, very low power and absolutely 0 confidence. I really thought pads would of fixed my problem.

Could a bleed fix this, there is a bit of play in the pedal..

Thanks.

Jono.

[project.r.racing]

Did you bleed the system when you replaced the pads?

[emily_mx5]

did you put new rotors on? or at least machine the old disks?

what colour is the brake fluid? it should be pretty clear, normally yellow. if its brown that indicates water or contaminants have seeped its way in and its old. Could have air bubles also.
Bleed the whole system with new fluid.

Braided lines and a brake master cyl brace help to reduce spongeyness in the pedal. I have both, hawk hps pads and slotted rotors, my brakes are fantastic

[manga_blue]

Hawk are very particular about break-in procedures. Basically new pads must be bedded onto new or reground rotors in a controlled series of stops in order to lay down a new boundary layer on the rotors. Break-in makes an enormous difference. Read all of this carefully:
http://www.tirerack.com/brakes/tech/tec ... ?techid=85

[dmad_dood]

My brake fluid looks quite new.. a nice golden colour but i want to bleed it as a starting point anyway. Bleeding might give me more braking power but i doubt it will change the bite of my pads or anything?

I've already been using my pads for a good few weeks now am i doomed for bedding in? Is it too far down the road to start trying to bed in.

I didn't change my rotors or have them skimmed when i installed the pads.

Thanks.

[MattR]

Flush new fluid through the system, that will help with feel and you will know you have all the air out and new fluid.

For the brake pads, pull them out of the calipers, making sure to note which one went where, get some 120-200 grit sandpaper and go to town on your rotors scratching them up nicely so you know you have all the old pad material off them. Also give the pads a hit with the sandpaper, or the ghetto way of rubbing quickly across rough concrete will do the same job a bit easier, just leaves nice black patches where you did this.

Wipe down the rotors with a clean cloth and put the pads back in. It maybe worth also regreasing the slider pins if this wasn't done at the first pad replacement.

Bed the pads in correctly, for Hawks, I do 10 stops starting from 50km/h up to 80km/hr with a few hundred metres between stops. Don't come to a complete stop or drag the brakes.

This should have you sorted for brakes.

[manga_blue]

x2 for everything Mattr says except I reckon you can be a bit less severe when bedding Hawk pads. I usually do just 5 or 6 spells, one after the after, of hard braking from 50 or 60 down to 5. No need to exceed any speed limits and better not to come to a full stop. Other brands (EBC?) need more than this but it seems to work for Hawk.

[sailaholic]

Did you fix your problem dmad_Dood?

I am having a similar problem, very hard pedal, car does stop, but your really have to stand on the pedal. Have had the car at the track, will pull up ok at qr, but does use lots of pedal pressure and is almost impossible to lock up.
Na8, standard calipers, hawk HPS pads, PBR slotted and cross drilled rotors, braided lines. Pads and rotors were done by steampunk during his ownership, while also feeling braking wasn't up to where it should be.

However, i drove plohls car and repeatedly almost locked the brakes up whe going to stop quickly, and he drove mine and commented "your brakes are ****ing rubbish".

Pulled the vacuum line of the booster and blocked it, makes no difference to the engine idle if it was off and blocked, or on.
Tried a short little drive with no booster. Car was almost unstoppable.
Pulled the rear calipers, both moved easily on the slider pins by hand, evidence of grease around.
Put blocks of wood in each calipers and squeezed the pedal. Left rear left a reasonable indentation. Right rear, barely marked the timber.
Both had the adjustment screw wind back ok and could get pistons back to replace calipers over the pads.
Didn't have time to do the same with the front.

No hot brake smell or evidence of heavy dragging. all the rotors are always shinny.

To me, it means that piston in the RR caliper is a bit suspect as it obviously wasn't exerting much pressure on the timber. However, pressure in the hydraulic system should be equal everywhere (ignoring proportioning valves). so if one caliper is seized, it should have the same pressure, but less travel. Ie, braking should be normal on the other 3 calipers, with reduced effectiveness on the seized one.

So i'm not sure i've really found the problem. i guess it's possible one or both of the fronts is in a similar condition? i've counted the booster out due to much reduced performance with it off, maybe this was incorrect, it works but only just?

I'd prefer not going through the process of bleeding brakes (yes they are due to be done) before emptying the whole system for a caliper overhaul. i also don't think this is the problem as i'm sure steampunk would have done fluid when he did the rest of the system.

Thoughts appreciated

[hks_kansei]

Why not just bleed them?
You aren't doing a full flush, it will only use up 1/4 to a 1/2 a bottle of fluid.


$10 of fluid may fix it before spending a bit more on a caliper rebuild.



The other thing, what temp are the pads? they might just be sh*t when cold.
Do they get better when there's some heat in them?

[sailaholic]

I'm time poor, and have never heard of someone having similar problems of a super hard pedal at all speeds and levels of braking due to fluid, so i've haven't been keen to do it. I also want to do a full flush and again being time poor, don't want to do things twice.

If no one comes up with great answers though, i'll give it ago.

Hawk HPS are the high performance street, one level above Hawk OEM replacment. SO Hps -> HP+ -> Blue. I've dríven Blues, which are known to be a bit so/so cold and they were better, Guran i think uses HP+ and his only complaint is the bite little too well if anything and Plohl has QFM A1RM, which are there Track, but can use at the street, pads and i would say they bite twice as hard from cold.

HPS Ferro-Compound Features:

Increased stopping power
High friction/torque hot or cold
Gentle on rotors
Extended pad life
Low dust
Virtually noise-free

Has anyone had problems with bias valves or master cylinders in these cars?

[manga_blue]

Glazed pads or glazed rotors?

Glazed pads can be fixed by some rough sanding.

Glazed rotors are harder to fix. You could get them surface ground but often when they've become glazed they're too thin to re-surface anyway. My local brake shop guy said he couldn't cut my glazed rotors on the sort of cutting machines that brake repairers use, they need surface grinding at a machine shop.

[plohl]

Glazed pads or glazed rotors?

Glazed pads can be fixed by some rough sanding.

Glazed rotors are harder to fix. You could get them surface ground but often when they've become glazed they're too thin to re-surface anyway. My local brake shop guy said he couldn't cut my glazed rotors on the sort of cutting machines that brake repairers use, they need surface grinding at a machine shop.

Is there some visual check for this? Or just hit the pads with some sand paper and hope they're the problem?

[manga_blue]

I'd just go through "gazed rotors" in google images to get the general idea. Usually there's a pattern of normal metal and hard glossy patches, often with surface microcracking in them.

Not mine, but this is a good example of what mine have looked like (but without the cross-drilling and related cracks of course):


Pads are easier to spot - just a hardened glazed layer on top. It sometimes goes with crumbling, starting at the edges, if they've been terminally overcooked. It would help to google images them too.


If you're overenthusiastic with bedding Hawks in then you can have them like this from new.

[project.r.racing]

i would suggest glazed pads. or worn pads and thin rotors. how old are the pads and rotors?

if a piston was suck, you would be able to lock up the other 3 calipers easier as the pedal pressure is going into 3 pistons, not 4.

if time poor, then make time.

if have no sand paper, then place pads fricton surface down on the concrete and do circle motions 2 or 3 times.

[sailaholic]

combating Time poor is more about making the right time choices then just making bulk time.

Will go back and have another look at the rotors, and sand the pads anyway if i'm going to pull them out to check them.
Pads would have had 6mm i'd guess left in them. In terms of k's they have done very little work 10k km? maybe, same with the rotors. Will do the same with the fronts, as if the rears have glazed i'd assume the front would have too.

Cheers for the advise that what comes up with google images is relevant / accurate.