Jump to content
SAU Community

Recommended Posts

The most important thing to do is to ensure that the pistons are fully back in the bores so that you can't get air bubbles forming behind them. If you've got AKB springs then you'll need to make some timber wedges to hold them back which is pretty simple - but you'll need wedges for bleeding anyway to stop the pistons moving up the bore.

I'm a big fan of bleeding calipers from the 'bottom' because bubbles like to go 'up'. Since you're going to have the calipers off the car and mounted to some sort of fixture (unless you've got 5 sets of hands) I'd suggest that you bleed it by introducing fluid from both directions and with the caliper in both orientations. Get a barb for the end of your braided line and go to the chemist and get a 100ml syringe to force the fluid through with. You can use any old shit fluid for this (*new) because you'll displace it once you bleed the system properly later on with SRF or similar. Probably worth cracking the transfer pipe too just to be sure.

Once you've got brake fluid everywhere and no more bubbles stick the caliper back on the car and bleed the fluid up from the caliper to the MC.

26 minutes ago, Komdotkom said:

The most important thing to do is to ensure that the pistons are fully back in the bores so that you can't get air bubbles forming behind them. If you've got AKB springs then you'll need to make some timber wedges to hold them back which is pretty simple - but you'll need wedges for bleeding anyway to stop the pistons moving up the bore.

I'm a big fan of bleeding calipers from the 'bottom' because bubbles like to go 'up'. Since you're going to have the calipers off the car and mounted to some sort of fixture (unless you've got 5 sets of hands) I'd suggest that you bleed it by introducing fluid from both directions and with the caliper in both orientations. Get a barb for the end of your braided line and go to the chemist and get a 100ml syringe to force the fluid through with. You can use any old shit fluid for this (*new) because you'll displace it once you bleed the system properly later on with SRF or similar. Probably worth cracking the transfer pipe too just to be sure.

Once you've got brake fluid everywhere and no more bubbles stick the caliper back on the car and bleed the fluid up from the caliper to the MC.

Thanks for that Komdotkom

Does anyone by chance know what the thread is on the end of the hard line of the GTST front brake system before it goes to the braided line - will need to get a fitting to put in there as you say.

Could you do this with the caliper on the car? Just get the pistons all the way back with a spacer or even some clamps? Im running a 36mm disc and 18mm pads - the pistons are almost as far back as they can get but i think with some old pads and a wedge I can make sure. Just easier if the caliper is mounted to something.

Stick the caliper in your vice with soft jaws, that way you can turn it upside down simply.

I think the factory lines are 10x1mm but I'd just take the whole thing down to your local Pirtek/MSCN and get them to sort it out.

  • 1 month later...

Nah never got it sorted. I have clamped all the pistons fully back using g-clamps. Pressure bled, vacuum bled, tapped it with a mallet, sung to the gods of deceleration.....no difference.

My only real conclusion is the brake pressure from the car is to much for the calliper. 

So I would definitely not buy these callipers. Endless would be a better option especially if it doesn't have so much lightening done to the calliper by ways of material removal.

As a side note the new D2 1 piece calliper does exactly the same thing as the Alcon. So there are other callipers that have the same issue. If anything the D2 was worse.

It's really interesting how much it's moving left to right, and doesn't appear to be actually spreading.

For this to be moving left to right, without flaring, means unequal forces being applied until equilibrium hits in one way or another.

 

Reasons it could be unequal;

Piston sizes left to right are different sizes. Only minute differences.

Pistons moving on different planes. That is, are they moving directly straight at each other, or slightly out of alignment.

The fluid is restricted getting to one side.

 

Some tests you could do. Pull the bleeders on the left and right, fit each side with pressure gauges. It will allow you to make sure pressure is equal (and really, it should be as fluid flow is so damn low, so fluid flow dynamics shouldn't come into it).

 

With the calipers off the car, have both sides retracted as far as possible, measure very very accurately (think micrometre) distances between opposing pistons in four different spots per set of pistons.

Firstly, on each opposing pistons pair, the measures on for different spots should be equal. If it's not, and especially if one spot appears to actually get closer compared to another, the pistons aren't aligned, and now the forces left to right won't be equal, as they're the forces fighting each other.

 

You can also pull all the pistons out, and very very accurately measure the diameter of them. If they're not equal left to ight in the pairings, and especially if the area of the pistons on one side is different to the area on the other overall, it'll all be out of whack.

 

My bet, is shit QC in making sure the pistons move in the same plane left vs right. Some minor out of square machining, and nothing will line up, things will want to move around.

 

  • Like 1

While all of the above makes sense, we're not talking about some Ling Long calipers of AliExpress; Alcon would have to be one of the top 5 caliper suppliers in the world and these are not their budget units. If there were manufacturing defects in the caliper causing this issue I'd be very disappointed.

Having re-watched the video a few times I think it's dog bone/mount related. The caliper moves independently to the rest of the suspension and brake assembly which suggests to me that it's not mounted rigidly. I know this sounds stupid, but have you got enough thread on the retaining bolts or are they a poofteenth too long and it's not super tight? For axial movement to be occurring without deforming the caliper that can be the only answer.

Edited by Komdotkom

Yes, you can very clearly see from more than one angle that it is the whole caliper moving left-right, not deformation of the caliper. The top moves, the bottom moves. Equally.

It should be possible to see where the movement is occurring. Just need to look more closely.

Hello,

The dog bone wont have much to do with this - the calliper applies a load about the disc - the outside of the calliper is more flexible than the inside by virtue of it not haveing the big torqued down bolts, additional metal structure on the caliper itself, and mostly not being cantilevered. So the outside of the calliper is pushing away as its more bendy and brining the inside with it as an equal pressure on both sides of the caliper looks to cause more flex on the outside - which makes sense.

I have done this same thing with the calliper unbolted from the dog bone - same thing happens. Although id have to watch more carefully to see how much more the outside moves than the inside in this case.

Im guessing there is a point in the pedals travel where the pressure is not actually increasing in the system - its just volumne displacemnt - and because the outside of the calliper is more flexy, it receives that volume.

Have gone back to Alcon again - but beyond a resolution there I would stay clear of this calliper and possibly any of the lighweight type of callipers - especially if you have the smaller 15/16" master cylinder.

Cheers.

9 minutes ago, GTSBoy said:

But the caliper is clearly NOT FLEXING. The whole bloody thing is moving. Both sides are moving relative to the disc.

Hey GTSBoy.

What would be the reason for that - if the entire caliper is moving to one side because of the dog bone being flexy - what would actually cause that? If a caliper has no physical flex as the pressure on both sides is even - then why would it move at all? Keen to get thoughts - not having a go. I just cant see the mechanism that would cause the entire caliper to shimy to one side.

Setup a dial indicator on the dogbone and pump the pedal. If that's not moving then the caliper is moving in the radial mounts.

If you think about it, the movement you are seeing (3-5mm) is miles above the elastic limit of the caliper material, so you'd be seeing cracks if this was a flex issue.

  • Like 1
  • Thanks 1
52 minutes ago, Komdotkom said:

Setup a dial indicator on the dogbone and pump the pedal. If that's not moving then the caliper is moving in the radial mounts.

If you think about it, the movement you are seeing (3-5mm) is miles above the elastic limit of the caliper material, so you'd be seeing cracks if this was a flex issue.

This ^.

There is massive movement somewhere. If the caliper was flexing you would see it spreading out at the bottom, as if there was a hinge through the top, above the pad pins. That's not what we're seeing.

  • Like 1
  • 4 months later...

Hey Blakeo,

Yeah I have confirmed it is the calliper by testing without the brackets etc. Even Alcon haven't been able to explain that away. They are saying it's normal! To be fair with good pads the car stops fine even on the track. But the pedal feel isn't good. I bet if you did endurance type events they would start to struggle.

Who did you buy yours through Blakeo?

My lines are secured by a bracket off the stock splitter block point. Has some rubber grommets. I also got custom lines made that are a bit shorter than some of the ones you see.

 

  • 7 months later...

Probably too late to reply to this, but worth a try.

It's not calliper flex, the calliper as a whole is moving so it has to be calliper mounting bracket flex.  Calliper mounting brackets are designed to stop the calliper rotating, they don't need to be designed heavy duty to stop the calliper moving in and out. 

Whatever it is is not the major cause of poor pedal feel, the outer pistons are moving towards the disc rotor the same amount as the inner pistons are moving away from the disc rotor.  Hence no change in fluid usage, what extra fluid is needed to move the outer pistons is recovered from the inner pistons.

For a calliper to move as a whole by far the most common reason is the rotor is not perfectly centred in the calliper.  The first thing I check is that hub face is perfectly clean, bare metal, where the rotor hats contacts it.  Then I check the that rotor is firmly held in place by at least 3 wheel nuts (or equivalent).

If all of the above are confirmed to be in perfect alignment then I would check the piston sizes and ensure that the 3 inner pistons and 3 outer pistons have matching diameters (eg; 28/32/36mm).  I have seen a no name 4 spot calliper that had 1 of the 4 pistons a different diameter.

Maybe I missed it, are both the callipers exhibiting the same problem?

I would remove the transfer pipe and inspect it to make sure that there are no restrictions.

Maybe you already have but if not I would return them with the video and have them confirm all of the above.

 

Hope that helps

Cheers

Gary

 

 

  • Like 3

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
    • Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
    • But first....while I was there, I also swapped across the centre console box for the other style where the AV inputs don't intrude into the (very limited !) space.  Part# was 96926-4GA0A, 284H3-4GA0B, 284H3-4GA0A. (I've already swapped the top 12v socket for a USB bulkhead in this pic, it fit the hole without modification:) Comparison of the 2: Basically to do the console you need to remove the DS and PS side console trim (they slide up and back, held in by clips only) Then remove the back half of the console top trim with the cupholders, pops up, all clips again but be careful at the front as it is pretty flimsy. Then slide the shifter boot down, remove the spring clip, loose it forever somewhere in the car the pull the shift knob off. Remove the tiny plastic piece on DS near "P" and use something thin and long (most screwdrivers won't fit) to push down the interlock and put the shifter down in D for space. There is one screw at the front, then the shifter surround and ashtray lift up. There are 3 or 4 plugs underneath and it is off. Next is the rear cover of the centre console; you need to open the console lid, pop off the trim covering the lid hinge and undo the 2rd screw from the driver's side (the rest all need to come out later so you can do them all now and remove the lid) Then the rear cover unclips (6 clips), start at the top with a trim tool pulling backwards. Once it is off there are 2 screws facing rearwards to remove (need a short phillips for these) and you are done with the rear of the console. There are 4 plugs at the A/V box to unclip Then there are 2 screws at the front of the console, and 2 clips (pull up and back) and the console will come out.
×
×
  • Create New...