[droverdave]

How does that help apply more pressure to the disc with the exact same force applied to the pedal?

[royce]

Rough rotors wont do shit but shred the pads, why put the energy into shredding the pads rather than stopping the car?

Temp is a big thing, what brake temps are you testing at? if its these 3 tests from a stand still you wont get enough heat for a performance pad and you'll go backwards.
Discs need a lot more fluid pressure to get the same brake effect as drums, adjust the prop valve up heaps until all 4 wheels lock evenly, might pick you up enough.

A new booster might make a difference, you still need to transmit the mechanical force through to the master cyl once the vacuum is gone, if that part is tight or seized up you'll be losing force there.

I would machine the rotors, get normal old Bendix pads, make sure they are all bedded in properly (driving up and down the road smashing the pedal or dragging the brakes is not properly) have BHSS or whoever strip the booster and check it that its working with no vacuum.

[royce]

BlueSuzy wrote:

It would be just the same as fitting new pads. Some calipers I've come across, new pads are a tight fit with the piston pushed all the way in. Ask the manufacturers what the purpose of the shims are.

Pistons are self adjusting, the pads always sit the same distance from the rotor for the life of the pad, the shims are to stop squeals.

[Zook_Fan]

You're not putting energy into shredding pads. A rough surface has a higher coefficient of friction, therefore for the same pressure it will be harder to move. Getting the friction up will slow you down quicker.

[Scrawny]

Zook_Fan wrote:

You're not putting energy into shredding pads. A rough surface has a higher coefficient of friction, therefore for the same pressure it will be harder to move. Getting the friction up will slow you down quicker.

A machined surface has the benefit of being rough AND flat. Not much point having a rough surface that's not flat and even, that'll just cause more issues with uneven braking

[shep]

royce wrote:

BlueSuzy wrote:

It would be just the same as fitting new pads. Some calipers I've come across, new pads are a tight fit with the piston pushed all the way in. Ask the manufacturers what the purpose of the shims are.

Pistons are self adjusting, the pads always sit the same distance from the rotor for the life of the pad, the shims are to stop squeals.

What the angry midget says

[DarkHorse]

Tests were done initially at whatever temp the brakes were at after the hour or so drive out there. After it failed the last one a couple of times he took the car around the block to warm them up again. Result was better but not yet god enough. I can take a few minutes before I go again to get them nice and warm.

So this is the prop valve:


Only adjustment is the Allen screw on the top, which determines it's 'resting' position... as the rear suspension compresses it pulls the lever down, increasing the flow to the rear brakes... yeah? So I want to screw the adjuster further in to get more rear bias when unladen, yes?

[got_bar_work]

Put a t in place of it
The back of your vit has heaps more weight then stock
they can cause weird shit to happen at bad times .

[royce]

DarkHorse wrote:

Only adjustment is the Allen screw on the top, which determines it's 'resting' position... as the rear suspension compresses it pulls the lever down, increasing the flow to the rear brakes... yeah? So I want to screw the adjuster further in to get more rear bias when unladen, yes?

spot on

[fordem]

droverdave wrote:

How does that help apply more pressure to the disc with the exact same force applied to the pedal?

If this question refers to the braided steel flex lines, the answer is that rubber flex lines expand when the pressure is applied, braided steel doesn't, so the pressure that would have been absorbed by the expanding lines will now get to the disk.

I doubt it will be enough to make a difference, but until/unless you've driven a vehicle with braided lines it's hard to appreciate the difference it makes - a few years back I had an OE rubber flex start to "weep" and swapped all the flex lines out for braided lines, so I got the chance to make the comparison with the only change being the lines and the fluid - it made a significant difference to the feel, but I have no idea if it improved the performance of the brakes.

[DarkHorse]

Thanks Royce.

I can get the calipers rebuilt for $120ish each.
2 sets of pads for say $200

I already have braided lines up front, one for the rear might be another $80ish
Retest will cost me up to $300
Brake shop today suggested slotting the rotors might make a bit of difference...?



For the sake of interest I also have to get the speedo ratio box re-certified for this car, another $100
Replace bent steering arm - $60
Replace weeping rear axle seal - $20
Then the engineer will probably be at least $600

...and that's all before CTP and rego.

[DarkHorse]

Calipers are in for rebuild, rotors getting machined, braided lines made up, and fresh pads.

I'll wind the prop valve in a bunch, and... because... racecar...?
Might have to look at packing out the master to suit the new push-rod angle, but will play with that when I have a chance to put it back in.

Also, thinking ahead - is gravity bleeding going to be the best way to get the system juiced up again? Rear left through to front right making sure the master never empties?

[pezz]

i like the reverse brake bleeders

[atari4x4]

darky, what a drama!!!

slotted rotors front & rear could also help get you a bit more bite, i'm pretty sure i noticed the difference when i swapped over to them in the silver one. the blue one was all done at once so it's hard to say this time around.

also can you pick up a set of road tread in the same size you're engineering, surely there is some gains to be had there or does the cert specify a MT & a sizing in NSW?

[Zook_Fan]

The point of friction that you're concerned about is the rotors on the pads, clamping force to slow down the wheel. If the force at the rotor produces a reactant force greater than the friction of the rubber and the road than you will get slip which is inefficiency. More rubber on the road would help, with HT or dropping the pressure as mentioned on the previous page but I don't think you'll lock up MT's without a booster.

HT's will drop the mass of the car though which is a good thing.

[JrZook]

Zook_Fan wrote:

More rubber on the road would help

More rubber = more weight = more inertia to try and slow down. I think its still quite far from locking up any tires (expect maybe spacies) without a booster.

[atari4x4]

JrZook wrote:

Zook_Fan wrote:

More rubber on the road would help

More rubber = more weight = more inertia to try and slow down. I think its still quite far from locking up any tires (expect maybe spacies) without a booster.

that was my thought, less is more & i'd definately be looking as shedding a few kgs too as suggested.

the chunky retread simex copies that i have weigh a few kgs more each than my MT's & while also being chunkier there was a noticeable difference in breaking & acceleration.

surely with some HT's you'd grab a heap more gription under breaking than a MT there fore transferring what stopping power he has to the ground rather than the tread blocks deflecting & having to try & pull up that extra rotating mass etc etc.

[murcod]

I've fitted slotted rotors (RDA's) on the front of the XL-7 with QFM brake pads. They do seem more powerful than the previous set of QFM pads with plain DBA rotors (but I haven't got any scientific evidence ) PS: avoid DBA's as they seem to have a habit of warping. I bought a set for the XL-7 and a friend bought a set for his Camry and AU Falcon at the same time- all three sets warped. I was using QFM pads, he was using bottom line Bendix.

[Zook_Fan]

JrZook wrote:

Zook_Fan wrote:

More rubber on the road would help

More rubber = more weight = more inertia to try and slow down. I think its still quite far from locking up any tires (expect maybe spacies) without a booster.

Maybe I didn't word it right. A HT has more rubber on the road than an MT, I was saying the lighter tyre with more contact area will be better but more for the weight reason than anything else.

[atari4x4]

how you traveling with this?

i've recently done a pad change while on exile island, these were the RDA semi metallic pads that i was running & seemed to hold up nicely on & offroad, no squealing, shudders etc etc.




the ones that replaced them are the same part# RDB1312SM but now come in gold for extra bling, pretty sure they were about $70 from Power Breaks in SA & included a free RDA air freshener. http://www.google.com.au/url?sa=t&rct=j ... 0277,d.dGI

these are the rotor's i'm running, should really get around to grabbing a rear disk kit from BenT


Front Slot Rotor x2

Part # RDA7610

Rotor Type: Vented

Diameter: 310

No of Bolt Holes: 5

FYI the guys at power brakes recommended a 300km bedding in procedure for the pads & rotors... these guys have done brakes & brakes only for 50+ years & know their shit.

[DarkHorse]

Hey Gussy! Thanks for all that - the brakes guy said he couldn't find slotted rotors for the Vit, so can give him a part number now which is good. He has sourced some semi-metallic pads for me which should be a step in the right direction. Braided lines are also made up, which can't hurt.

The fucken company that makes the testing machines won't reply to my e-mails and the "Find Your Nearest Testing Centre" link on the website is not working. I don't really want to drive an hour each way and pay $100ish to get the test done again until I have a reasonable chance of it passing.

Oh, and Speed Bleeder haven't replied to explain to me why they think Vit calipers are an M10x1.0 when they look more like an M8...

I like the HT idea. Of course I got rid of the old set of BFG ATs 235/85s I had. Anyone got a set of roadies in a 32ish R16 I can borrow?

I've been in Melbourne for a couple of days with work, and am gone again from Sunday for 3 weeks, so nothing is likely to happen for a while now.

[alien]

RE: Tyres - ask around some tyre shops, especially given you're gone 3 weeks... see if you can score 4x barely legal HT tyres they've taken off a customers car.

[DarkHorse]

Ended up with new front rotors (not slotted) machined rear rotors, all calipers rebuilt, new braided lines for the back, new normal road pads for the rear and organic compound for the front.

Bolted the new/rebuilt/machined breaks back on. Bleeding will have to wait for about 3 weeks now. Along with adjusting the prop valve, losing the excess weight etc.



Brake pedal was a bitch to get back in. Wouldn't recommend that to anyone.

[got_bar_work]

Would u be allowed to have a vac reserve tank installed on the booster side of the one way valve.

[DarkHorse]

As a backup/contingency for the booster failing? Dunno... I think it would need to be independently supplied so that it could stay charged if you lost vac, otherwise you're in the same boat

[got_bar_work]

It will be there to keep the booster working for a emergency stop if the motor dies. The check valve should stop it emptying till the booster is used I think.
I think some trucks have a similar setup.
Next step would be look at fitting some lux calipers to the front

[DarkHorse]

OK, Vitara sized bonfire is starting to look more likely...

Finally got around to refilling the system a few days ago. Filled master cylinder and bled out the prop valve, left front and right front as they started to leak fluid...

...

...

...

Nothing from the rears. Not a drop either side. Worked my way back along the lines cracking each joint to see if the fluid had made it that far, and got all the way back to the proportional valve. No flow to the rear outlet whatsoever. I tried it with the rear suspensded, with it sitting as normal, even manually manipulating the arm... and nothing.

The valve was sitting off the car for a few weeks, and I noticed a couple of spots of rust forming on the threads - is it possible that a blockage has formed to stop the fluid getting to the rear outlet? Is there any explanation except for a faulty valve?

Is this possibly an explanation for the weakness in the rears before? There has always been some flow to the rears before (bleeding after the disc conversion went in and during the first round of testing were pretty normal.)

Rapidly getting fed up, so any guidance would be much appreciated.

[royce]

crack the furthest rear nipple and give the pedal a few pumps to see if you need some pressure to get fluid through (I think you might)

is there a nipple on the prop valve?

[missmyljdaze]

DarkHorse wrote:

As a backup/contingency for the booster failing? Dunno... I think it would need to be independently supplied so that it could stay charged if you lost vac, otherwise you're in the same boat

Several of my old fiats had vacuum reserve tanks, one of the 2300's had twin tanks as standard equipment. [hidden behind the front bodywork]
This was not so much in case of failure - but due to having stuff all vacuum in traffic [pretty wild cam timing].
After driving a short while at decent revs, the vacuum reserve had enough vac. to last for several decent hits on the brakes before you noticed any lack of vac.

If you were to rig your vac. lines so you do a blatantly obvious hose disconnect and plug, or clamp the vacuum hose at the inlet manifold for the test - a good sized vacuum reserve tank [or tanks] might get you through the test.

what exactly will be involved with the brake testing?

stephen

[Jezza86]

Jimnys have a vac tank for the air hubs, fyi.