[DarkHorse]

Hey all, I am finally getting around to trying to get the Vit engineered.

First hurdle is a brake test because of the disc conversiin and larger tyres. Thankfully I can get it done with a Safe-T-stop plate test rather than having to hire Eastern Creek. Unfortunately the only engineer with the macine is over an hour away, and still charges $300 for the tests.

Anyhoo, I trundled out there the other day and rolled it up. First test was just an 'as normal' run - passed comfortably first go. Not exactly flying colours but passed. Second run was with the rears disconnected. Again passed first go. Third test was with fronts disconnected. Passed but only narrowly. Third test was all four calipers but with the booster disconnected. Failed. Again and again and again, and by quite a distance.

Short version is it needs more brake power for less pedal effort.
For some reason on all the other tests you can stomp on the pedal up to 880Nm, but for this one only 500Nm (50kg of pressure). He could get it up to the 50% 'pass' level with about 800, but nowhere near it with 500.

Neither I nor the ticketed engineer, mechanic and custom car builder could think of anything that was obviously wrong or would be a simple fix to get it up to spec.

The 'might help' list is:
- check proportioning valve (apparently this was the magic bullet on a previous car that had the same difficulty)
- modify pedal to give more leverage on push rod
- try to find stickier pads
- lose some weight (it was carrying a bit of crap, totalled 1680kg on the weighbridge)
- smaller tyres (not going to happen because that would defeat the purpose of getting it engineered.)

My only other thought would be to replace the master cylinder with something with a smaller bore to give more pressure, or even just a new replacement in case mine is underperforming.

I removed the prop valve yesterday and it looks fine, clean internally and moves fairly freely. I'll see what I can do with the pedal this week.

Any other thoughts or suggestions? Anything that might just be getting old and tired and underperforming?

If I can't get this up it means no engineering cert, which means no rego, so I'd have to get rid of it. Don't really want to give up on it, but that's kind of the reality at this point.

Any help greatly appreciated.

[alien]

That's a very complicated procedure!

A brake test for my engineer consists of me doing 40km/hr and jamming the brakes on- if the front skids before or at the same time as the rear then it passes. lol

If its just all about pedal pressure then can't you just upgrade the booster?

Maybe check this too: http://auszookers.com/forum/viewtopic.php?f=5&t=21781

[droverdave]

He said the test that failed was the test when the booster was disconnected, so id assume a new booster wont help.

One issue you might have with a smaller master cylinder is that yes you will get more pressure for less force, but you will also get more travel.

So you might have to modify the pivot point if you change to a smaller master. Is there a maximum amount of travel you are allowed?

[DarkHorse]

Yeah, that's right Dave, failed test was with the booster removed. Theory being I guess that if the booster crapped itself with my 86yo grandmother driving it she could still pull it up without caving in the back of whatever she was aggressively tailgating at the time.

There is no restriction on pedal travel in the test, hence the suggestion to modify for exactly that purpose. I will have to suss out the legal implications and also the practicalities of changing the angle of the push rod etc.

[pezz]

Would some things like locking in the hubs, droping the tyre preasure and changing diff ratios help with increased drag to help get you there

[Gwagensteve]

Weightweightweightweightweight

You need that car to be EMPTY. it will make a huge difference. loose EVERY bit of weight you possibly can. I'd remove everything that's not specifically mentioned on the cert. Barwork - take it off. Really - everything.

Have you corrected the throw of the prop valve for the suspension lift you are running? This is also critical.

What's the bore of the MC you're running? Getting into pedal ratio and MC bore is a bit of a minefield, as much as anything because you don't have a race pedal box so you don't have any built in adjustment. Most engineers don't like cut/welded modified brake pedal arms etc so that might not be an option.

I'm sure you'll get there. If you drop MC bore, make sure it's not by much or you'll get a loooong pedal and that's spooky.

Are you running a user adjustable prop valve? It sounds like you might have a teeny bit too little rear brakes.

Steve.

[BlueSuzy]

How old are the pads? Might be worth spacing them closer to the discs?

[Scrawny]

BlueSuzy wrote:

How old are the pads? Might be worth spacing them closer to the discs?

What??? How do you 'space' pads closer to discs?

[shep]

Scrawn wrote:

BlueSuzy wrote:

How old are the pads? Might be worth spacing them closer to the discs?

What??? How do you 'space' pads closer to discs?

Troller has to troll.

Back to real help.
Make sure that your tyres are at the correct pressure. To much air and it won't stop as well

[droverdave]

Im suprised that there wasnt a specified weight for the test. Ie half full of fuel, 4 adults, some cargo etc.

Though if you have a bunch of extra stuff on the car, bull bars, etc then yer its prolly worthwhile taking them all off.

Sounds like you were miles off the mark though, how much weight you reckon you can save?

[Zook_Fan]

Get a second pair of discs second hand and rough them up, the more aggressive the better. Then get a set of performance pads that will actually grip as best as possible.

Might not last for long because your pads will tear up but when it grips the friction will be miles higher than a normal disc.

[Gwagensteve]

Isn't 1680kg over GVM for a vitara? It would have to be close.

Steve.

[Zook_Fan]

1875kg for a 2L vitara so not much room for people in there.

[just_cruizin]

Zook_Fan wrote:

Get a second pair of discs second hand and rough them up, the more aggressive the better. Then get a set of performance pads that will actually grip as best as possible.

Might not last for long because your pads will tear up but when it grips the friction will be miles higher than a normal disc.

Best solution thus far.

[5ierra]

just_cruizin wrote:

Zook_Fan wrote:

Get a second pair of discs second hand and rough them up, the more aggressive the better. Then get a set of performance pads that will actually grip as best as possible.

Might not last for long because your pads will tear up but when it grips the friction will be miles higher than a normal disc.

Best solution thus far.

Could also look for a larger caliper along with this? Or atleast a caliper with a larger pad surface. More surface, more friction, more stop.

[tanshi]

im assuming he just wants a temp fix to pass the tests. rough, set of disks should do it.

[Gwagensteve]

IMHO it gets a bit more complicated than that. A larger pad area would imply a larger piston. A larger piston with the same m/c might not increase clamping pressure at the wheel if there is insufficient m/c bore to fill the larger calliper.

[DarkHorse]

Thanks heaps guys...

Weight: can definitely shed a fair bit - roofrack, awning, lights, winch, tools and reco gear... probably 100kgish? I kind of wanted to go in standard form for a trip so I had an idea how things would rate in the 'real world.' 1680kg was with my fat arse in the driver's seat, so vehicle with all the above crap would be about 1600kg flat.

On that note, while I do just need a quick fix to get through the tests anything I can do to actually improve the brakes would be welcome.

Pedal: haven't had a chance to look at it yet, but the engineer was just talking about relocating the pivot point upwards 10-15mm, giving more travel and more leverage. I'm not keen on any drastic cutting and shutting other.

MC: just running standard SV LWB unit. No idea on specs.

Pads/discs: good idea on the disc roughing, hadn't thought of that. Was going to buy a set of sacrificial pads if I can find some 'performance' units for the Vit front and Galant rears... anyone know of any that stick better than the Bendix ones in there now?

Prop valve: again just standard. Calmini rear arm which controls it is supposed to allow for the Calmini lift, so should be OK? Might look at tweaking it for more rear. It has an adjuster on it, but that's obviously just for a minimum point.

Thanks again all.

[Scrawny]

Instead of just 'roughing up' the rotors, why not get them properly machined?

[Zook_Fan]

Properly machined means that they will be rough but still very conservative for the sake of brake pad life. The rougher it is the more grip that will be available and he'll get a rougher finish from something a little less refined than machining.

[DarkHorse]

I'm having mental images of radial gouges cut with a 5"...

Anyone got some old discs they don't want?

[Zook_Fan]

DarkHorse wrote:

I'm having mental images of radial gouges cut with a 5"...

Anyone got some old discs they don't want?

Now we are on the same page

[DarkHorse]

Parts guy recommended EBC green pads to me today - can get them for about $100 from the UK (nearly twice that to get them locally.)

Apparently a bit squeally and need heat in them to really bight, but great when they do. Anyone have any experience with them?

[droverdave]

I had EBC greenstuff in my old corolla, and yep they took a few stops to get the heat into them. I found they were actually a bit dull on the first few stops.

They sound the exact opposite of what you need? To pass your test, don't you want the absolute most bite you can get from cold brakes and work excellently for 1 stop?

[BlueSuzy]

No not trolling. If i was why did the comment go through both of you numb nuts.

The less fluid you have to push the less pedal travel. Pretty simple.

[Scrawny]

You still haven't answered my question.... how do you space pads?

[JrZook]

^^Aluminum sheet or what ever between the pad and pistons

[BlueSuzy]

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.

[BlueSuzy]

Could look at braided brake lines too
For Scrawn: http://en.wikipedia.org/wiki/Braided_st ... rake_lines

[droverdave]

How does that help apply more pressure with the exact same f