BA brakes, AU master cylinder issue

Bushbasher · 24-10-2010, 09:53 AM

Has anyone who has done the BA brake upgrade on their AU upgraded the master cylinder as well and if so ,what was your solution to the problem?

I've just done the Fairlane and now, although there's plenty of braking power, it's at the end of a long pedal which is annoying and means my vertically challenged missus winds up braking with the end of her toes as the pedal goes down too far, plus it's annoying to me to have such a low pedal. Modding a BA master cylinder to take the cruise control switch and low pressure warning switch seems problematic so is there another solution? Can I have the AU one bored out or is there, for example, a larger master cylinder available from say a TE/TS premium brake setup or something?

....anyone?

Cheers
Bushbasher

The Monty · 24-10-2010, 11:09 AM

I didnt have any problems at all with pedal feel. Although I do like it soft, its deffinately not what I would classify as super soft, its still relatively firm. I know youve probably checked and double checked, are you positive you dont need to bleed them to get any air out of the lines?

mik · 24-10-2010, 07:50 PM

i realise its probably more an oil volume effect on the pedal , but i`m wondering if theres any play between the pedal rod and master cylander that could be adjusted out to bring the pedal up a tad?

Bushbasher · 24-10-2010, 08:11 PM

G'day Monty, I've bled the brakes completely twice, including the master cylinder at the c-c switch and ABS plug so there's definitely no air in the system. The pedal feel is not so bad and is firming up as the pads bed in, and they're certainly pulling the car up much better than before but where the brakes used to start to work after, say, 3cm, now you have to push the pedal 6cm before the brakes begin to react. As I said, for me it's just an annoyance as I like my pedal up a bit but my missus is having to brake with her toes as the pedal is too low for her to comfortably put the ball of her foot on the pedal so in an emergency stop she won't be able to put max. pressure on the pedal; that extra inch of travel before activating the brakes makes all the difference. I'd like to go for a bigger master cylinder but just wondered if anyone's done it before I start looking for a way.

Bushbasher

InfernoSR · 24-10-2010, 09:06 PM

When i did mine, i also opted for custom braided lines... maybe something worth looking into.

toughtimes · 24-10-2010, 09:52 PM

Gday bushbasher, like mik has said, can you adjust your booster rod at all? any fluid or vacuum leaks at booster behind master cylinder?

Bushbasher · 24-10-2010, 10:46 PM

Mics' idea is a good one and I'll look into it tomorrow but I'd still like to explore a bigger master cylinder as although it's progressive it still has a softer feel about it than I like.

Bushbasher

urbancowboy · 25-10-2010, 01:00 AM

My two cents,

I put Tickford Premium calipers (brand new fronts) on my AU with new disks (rda slotted) and pads (genuine ford), and braided brake lines all round, i also put a new master cylinder on it (genuine ford) and after some ridiculous headaches (don't even ask!), everything is sorted and my brakes are fine,

BUT the point at which the brakes do the most work seems be a bit further into the pedal travel than before! Not as far as you describe though, i think you might need to bench bleed the master cylinder as it may have a air lock in it somewhere.

I am about to put new rear disks on mine with new pads and i think this will fix my pedal travel issue, since my rear pads are very low on meat it needs to push more fluid through the line to get the rear pads to contact therefore soaking up more of the available pedal travel.

What are your rear brake pads like for wear?

ebxr82nv · 25-10-2010, 10:23 AM

From my perspective and I do sit very left of fieldwith my thinking most of the time, I wouldn't have thought low brake pads would affect pedal travel all that much due to the pistons not retracting fully back into the caliper when you take your foot off the brake. As long as you have the proper amount of fluid in the res and sufficient vacuum that is. If they rectracted that far you wouldnt need to push the pistons back in the caliper when changeing the pads.

I have heard a few others complain of this problem with this conversion and I'm not far off doing it myself so I'll be watching this with interest.

AMB · 25-10-2010, 06:22 PM

I agree with ebxr82nv. And its the same when you put the foot on the brakes, the piston only travels maybe less than mm, so the amount of fluid needed to displace the piston is small. But still you would need twice as much fluid to displace the heavier brake calipers (2 pistons aren't they?). I'm thinking maybe the BA has larger diameter brake lines, to deliver more volume. Does any one know what the diameters are, BA versus AU (we are talking AU series 1 aren't we?)
Edit: Oops, just read the OP signature, AUII! So what's the diff between BA and AUII calipers, I thought they were the same.

ebxr82nv · 25-10-2010, 07:05 PM

Bushbashers car is an au2, so it does come with the twin piston caliper standard but with the ba caliper being larger(I think) they might be a smaller piston than the ba items. The actual diaphragm in the ba master cylinder might be larger to?

GK · 25-10-2010, 09:47 PM

A while ago (read few years ago) someone upgraded from AU1 to AU2 brakes, including the master cylinder. IIRC, they inserted a small spacer to make the brakes engage earlier.

I may have some of these details incorrect, but can anyone else remember this thread?

GK

Bushbasher · 25-10-2010, 10:56 PM

Thanks for all the responses guys, it all helps, cheers. I may have over reacted after the initial fitting. After bleeding the brakes the brake pedal went all the way to the floor to stop the car with any power. Then after the second full bleeding, including the master cylinder, it was only marginally better so I was a little worried, but since then they've only got better and better.

Ok, time for an update and some clarification. Firstly, in my description of the pedal travel in post 4 I said 3cm and 6cm. These were only approximates used to demonstrate and highlight the point I was trying to get across and may have been misleading, sorry about that. At the time the brakes were quite soft as well as being on the long pedal so the soft "feel" was exaggerated. Since then I've done about 300km and the brakes have bedded in quite nicely. A couple of full blooded emergency stops from er, cough-cough, high speed helped bed them in in a hurry as well.
So as of tonight the pedal has firmed right up, in fact it's firmer now than it's ever been with plenty of bite. If anything they're too firm now and have lost that nice smooth progressive response they had as you press the pedal that was there before, you know, that slightly soft not quite spongy feel. The brake response to pedal input now is still further down/closer to the floor than before, maybe 15mm not 30 like I said before, and the effort required to stop the car is also higher but the actual stopping power has increased as would be expected from bigger slotted discs and pads, it just takes more effort to make it happen.(if that makes sense). I still feel that a slightly larger master cylinder will bring the pedal "feel" back closer to what it was, ie. softening the pedal back up and at the same time bringing the pedal response back up as it'll push more fluid to the bigger calliper pistons for less pedal movement. As for the effort required, it's not significant and maybe it'll disappear with a bigger master cylinder but if it doesn't it's no big deal, it's not worth messing about with a BA booster if that's what it would take.

So after all that, I'm very happy with the extra braking power but not 100% happy with the feel.....yet. I'll look into a bigger master cylinder and see what, if anything can be done without costing a fortune. If it's too expensive or too hard then it's no big deal either, I'll get used to the pedal feel I guess but either way, right now I'm more than happy with the my budget brake upgrade considering it's only cost me a grand total of $315 which includes used calipers, new discs, new Ferodo pads and the 5L container of brake fluid I bought. If I can do something about the master cylinder for less than $200 I'll do it and be one very happy camper to have it completely sorted for under $500.

Cheers
Bushbasher

mik · 25-10-2010, 11:17 PM

glad to hear its ok Bushbasher, i`m wondering if it has had any effect on the way the cruise control cuts off when you touch the brake now ?

foxtrot3 · 25-10-2010, 11:50 PM

Hi. A bigger master cyl will make the brakes harder again as you gain more fluid flow per mm of stroke at the expense of ease of moving the piston against the brake fluids pressure. Your couple of hard stops may have cycled the abs enough to help shift any air still in the lines to a point where it could gravity bleed (or let any air work its way back to the master cyl.) Let the brakes bed in a bit more and see what they are like after a month. What pads did you use as some of the ferodo pads can cook out and become very hard and noisy if treated harshly when new. Cheers MD

urbancowboy · 26-10-2010, 12:15 AM

Quote:

Originally Posted by GK

A while ago (read few years ago) someone upgraded from AU1 to AU2 brakes, including the master cylinder. IIRC, they inserted a small spacer to make the brakes engage earlier.GK

This is a old trick! A good one though! I've been contemplating doing it!

For factual sake,
the Tickford Premium calipers have a smaller piston size than the stock calipers,
and IMO the size of the brake lines shouldn't have such an impact, think about it, if it was a performance gain to have larger diameter lines then why don't race cars have lines 1' round?

As for my rear brake pads being a reason to effect the brake pedal travel, i now see why this was a stupid thing i wrote! LOL
But in my search for performance brakes i have spent too much so far and i am still scratching my head!
Think i need to do another master cylinder bleed and line bleed myself, and flush through with some high quality fluid rather than the genuine ford stuff i got cheap to flush the old stuff out with.

Bushbasher · 26-10-2010, 09:33 AM

Quote:

Originally Posted by mik

glad to hear its ok Bushbasher, i`m wondering if it has had any effect on the way the cruise control cuts off when you touch the brake now ?

I haven't actually adjusted the pedal Mic but IIRC the brake light and c/c switch are in front of the pedal so shouldn't be affected by any adjustment of the master cylinder shaft which is behind the pedal. My brake lights and c/c react as soon as you touch the pedal and move it even slightly, it's the same for the wagon.

Bushbasher

Bushbasher · 26-10-2010, 09:51 AM

Quote:

Originally Posted by foxtrot3

Hi. A bigger master cyl will make the brakes harder again as you gain more fluid flow per mm of stroke at the expense of ease of moving the piston against the brake fluids pressure. Your couple of hard stops may have cycled the abs enough to help shift any air still in the lines to a point where it could gravity bleed (or let any air work its way back to the master cyl.) Let the brakes bed in a bit more and see what they are like after a month. What pads did you use as some of the ferodo pads can cook out and become very hard and noisy if treated harshly when new. Cheers MD

Hmmmmm........The pads have Ferodo "Target"on the box and you may be right about cooking the pads out foxtrot3, they certainly were smoking fairly well after the first big stop from high speed and your theory about cycling the ABS and pushing out any air in there makes sense too, at least it fits the in with the time line of how the brakes came good. I'll give it a few weeks and see how they go and if things don't change I might go get another set of pads and try again. I bought the pads on special from Repco for a whole $33 so they were cheap enough. I might go grab another set anyway and stick them in the shed for just in case.

Bushbasher

mik · 26-10-2010, 12:06 PM

thanks Bushbasher , i was`nt sure if it worked off the pedal or was sensed by oil pressure.

Casper · 26-10-2010, 02:05 PM

Something you can look into is getting the master cylinder off an AU 1 tonne ute. They actually had a larger one than fitted to AU sedans. Straight swap over and should solve your problem.

Bushbasher · 26-10-2010, 03:16 PM

Thanks Casper, that was just the info I was looking for, cheers.

Bushbasher

Casper · 26-10-2010, 03:45 PM

This only applies to the AU1 series that I know of. It may be for the later series AU's but am not sure. Thats why you will need to look into it further. Its a known simple solution to upgrading the AU1 brakes, hopefully it might be a solution to later models too.

AMB · 26-10-2010, 06:18 PM

Quote:

Originally Posted by mik

thanks Bushbasher , i was`nt sure if it worked off the pedal or was sensed by oil pressure.

There is a backup one on the master cylinder, works on oil pressure, just in case/when the brake light switch fails.

Daniel B · 03-11-2011, 05:59 AM

Ok, time to dig up another old thread, did the OP get this sorted, was the 1 Tonner Ute M/Cyl the way to go?

Also does anyone know if the Brake Boosters are different between Series 1/2/3 on the AU?

Bushbasher · 03-11-2011, 06:42 PM

I did nothing in the end. The original master cylinder is doing the job ok these days. It took a couple of weeks for it to settle down and the pedal feel isn't quite as soft as it used to be but it's certainly not problematic now and she sure does pull up well when I stand on it for an emergency stop.The initial bite is a bite soft till the pads heat up then it pulls up with a vengeance but that's pad choice rather than a mechanical issue.
As for the other, I believe SII & SIII master cylinders are the same but couldn't swear to SI.

Daniel B · 04-11-2011, 01:36 AM

Quote:

Originally Posted by Bushbasher

I did nothing in the end. The original master cylinder is doing the job ok these days. It took a couple of weeks for it to settle down and the pedal feel isn't quite as soft as it used to be but it's certainly not problematic now and she sure does pull up well when I stand on it for an emergency stop.The initial bite is a bite soft till the pads heat up then it pulls up with a vengeance but that's pad choice rather than a mechanical issue.
As for the other, I believe SII & SIII master cylinders are the same but couldn't swear to SI.

Cool, thanks for that, will give it a few weeks and hopefully feels better.

cedric · 04-11-2011, 11:40 PM

i put ba calipers on my au3 xr8 and did not notice any change at all only went with them as nobody had any au ones in australia apparently

**FLOORED** · 05-11-2011, 09:13 AM

Quote:

Originally Posted by Bushbasher

I did nothing in the end. The original master cylinder is doing the job ok these days. It took a couple of weeks for it to settle down and the pedal feel isn't quite as soft as it used to be but it's certainly not problematic now and she sure does pull up well when I stand on it for an emergency stop.The initial bite is a bite soft till the pads heat up then it pulls up with a vengeance but that's pad choice rather than a mechanical issue.
As for the other, I believe SII & SIII master cylinders are the same but couldn't swear to SI.

Don't take this the wrong way but are the calipers on the right way? Are the bleeder nipples on the calipers at the highest point of the caliper and point upwards and not at the bottom? This fitting problem happens more often than most people think and even experienced mechanics still ring me with issues and find this has happened and what happens is you can't bleed the calipers properly which causes some air to be trapped in the caliper body.
A larger master cylinder will give you a firmer pedal and you actually needmore force on a larger master cylinder bore to get the same pressure out of a smaller bore one.
FYI
There are several master cylinder options for AU falcons from 98 to 2000 and any model after 04/2000 has a 31.75mm fast fill front bore which is the same as a BA.

I hope this info may help.

Bushbasher · 05-11-2011, 09:51 PM

Yes, my calipers are on the right way. My brakes are fine these days but it does take more effort to make the car pull up hard; but I did change to BA slotted discs, new pads and BA calipers all at once so I'm guessing they just took a little while to all settle in. Having said that, they now will happily lock the wheels on the black top and make the ABS work overtime where the old brakes didn't even come close most of the time and I reacon I slashed 3 car lengths or about 15m off of a hard stop from 110.

Bushbasher

Daniel B · 06-11-2011, 09:49 PM

Quote:

Originally Posted by FLOORED

Don't take this the wrong way but are the calipers on the right way? Are the bleeder nipples on the calipers at the highest point of the caliper and point upwards and not at the bottom? This fitting problem happens more often than most people think and even experienced mechanics still ring me with issues and find this has happened and what happens is you can't bleed the calipers properly which causes some air to be trapped in the caliper body.
A larger master cylinder will give you a firmer pedal and you actually needmore force on a larger master cylinder bore to get the same pressure out of a smaller bore one.
FYI
There are several master cylinder options for AU falcons from 98 to 2000 and any model after 04/2000 has a 31.75mm fast fill front bore which is the same as a BA.

I hope this info may help.

Hey Matt, yeah calipers definitely on the correct way up, I remember thinking what a bugger of a position the bleeders are in. So basically being a series 1 master cylinder (smaller bore) it should actually be easier to apply the brakes than if I went to the later model (larger bore) cylinder? I will let the brakes bed in a bit and see how it comes up I guess. Thanks for your input.