R32 rear brake conversion

[tony_danza]

Ok, I'll get lost if I do quotes on quotes..

*Bias, I understand what you mean now  - I think somewhere like VWR would be a good place to start with this to understand what settings are required, obviously with their road car developments, as they'll run traditional mechanical bias switches on a race car. I'm not confident with the web's guesswork or dealer knowledge. Do you have any experience in changing the parameters, or is it just something you're aware of?

*R32 rears. Yes, as in the full rear set up, calipers/cariers/discs/splash guards. As mentioned it's just the 3rd hole that's an issue... but I still want to physically see it for peace of mind.

*RS4 fronts. Sorry, I didn't mean I was having them.. they're just "going on" in general. From what I understand there may be a small & easy carrier mod, but it utilises all OEM kit - it may be RS4 calipers and RS6 discs or something? You'd need to ask AMD.

*Piston size. You confused me here as you were talking about the Autotech kit and I just assumed you were talking about the front AP's they do that'd I've bought recently and why I went into the garb about them not being right - I now see you meant the rear kit they do. D'oh!

So, I'd have thought you'd not be able to use the GTI rear caliper as it's designed for a single disc, not the much thicker vented disc of the R32...? that's not to say they're might be using the one from a MKIV Anniversary instead because it's already red and designed for the vented brakes that had? Pure speculation on my part, I don't know.

[Top Cat]

Ok, I'll get lost if I do quotes on quotes..

*Bias, I understand what you mean now  - I think somewhere like VWR would be a good place to start with this to understand what settings are required, obviously with their road car developments, as they'll run traditional mechanical bias switches on a race car. I'm not confident with the web's guesswork or dealer knowledge. Do you have any experience in changing the parameters, or is it just something you're aware of?

*R32 rears. Yes, as in the full rear set up, calipers/cariers/discs/splash guards. As mentioned it's just the 3rd hole that's an issue... but I still want to physically see it for peace of mind.

*RS4 fronts. Sorry, I didn't mean I was having them.. they're just "going on" in general. From what I understand there may be a small & easy carrier mod, but it utilises all OEM kit - it may be RS4 calipers and RS6 discs or something? You'd need to ask AMD.

*Piston size. You confused me here as you were talking about the Autotech kit and I just assumed you were talking about the front AP's they do that'd I've bought recently and why I went into the garb about them not being right - I now see you meant the rear kit they do. D'oh!

So, I'd have thought you'd not be able to use the GTI rear caliper as it's designed for a single disc, not the much thicker vented disc of the R32...? that's not to say they're might be using the one from a MKIV Anniversary instead because it's already red and designed for the vented brakes that had? Pure speculation on my part, I don't know.

Crap - this moved on a lot!

Erm, in brief:

Brake bias, I don't know anyone who knows how to change it via the ECU, so I'll chose the physical method instead... that's not poo-pooing your idea - just makes more sense to me.

You cant actually 'adjust' the bias in the ECU.  But what it does do is basically re-define the default bias, depending on what physical hardware is at each end.  So if we just stick with the same size rear anchors, and look at differing front anchors - then a 312mm disc will provide more effective braking effort for the same pedal pressure as a 286mm, and a 345mm disc will be more than the 312 and the 286.  But because the bias is actually controlled electronically, rather than by old skool pressure limiting valves or load sensing valves - then any 'change' to disc performance at one end, which isn't matched by a (proportionately) equal change at the other - well this can seriously upset the bias - or brake balance.

Detail here: http://wiki.ross-tech.com/index.php/VW_Golf_%281K%29_Brake_Electronics_%28MK60%29

R32 rears go on ok, although the splash guard will only locate to 2 holes instead of 3. I haven't done the mod myself, so until I do then that isn't gospel... but seemingly plenty of others have.

As in - R32 rear calipers, discs, etc - or just the discs?

RS4 fronts are going on, it's being done by AMD and others - I have no idea what's involved to say if it's a simple or chisel & hammer job??

The caliper mounts will be quite different, as will the disc 'bells' - so some 're-engineering' will be required.  I take it you arn't going for the Ceramics off the RS4?   

Not sure what you mean on the caliper piston size point - the APs are 6-pots and the R32's are twin, so I wouldn't necessarily  expect the same sizes, don't 6/8-pots usually have staggered size pistons for "feel" and even pad wear??

I'm referring to the actual diameter of the piston in the caliper, and specifically for the rears - and this is all relevent to the hydraulic advantages formulae.  The dia of the R32 rear piston is 41mm, whereas the GTI has a 38mm piston.  If those Autotech rear kits are using a standard caliper with a 38mm piston, then because the piston is smaller than the pukka R32 calipers, the rear brakes from Autotech will not be as effective as genuine R32 rear anchors.

And the R32 has single piston calipers at all four corners, just like the GTI (only the R32 are bigger!).

And yes, 4/6/8/10 pot calipers often have differing diameter pistons - for a variety of reasons.  Pedal 'feel' and pad wear are the usual cited reasons, but also brake noise, physically 'packaging' the pistons correctly in the caliper, and lastly, fashion can all be cited.

They made custom bells & carriers for the AP discs & calipers. I sent them back as I wasn't happy with the clearance on the lower ball joint. IMO they needed a 20mm reduction on the bell offset and the carrier altering accordingly - so, I wouldn't bother asking them TBH. I do however know someone who can engineer carriers, if you have CAD to spec.

Nice, keep us updated when you can, thanks.   

                       

[Teutonic_Tamer]

Ok, I'll get lost if I do quotes on quotes..

LOL !!

*Bias, I understand what you mean now  - I think somewhere like VWR would be a good place to start with this to understand what settings are required, obviously with their road car developments, as they'll run traditional mechanical bias switches on a race car. I'm not confident with the web's guesswork or dealer knowledge. Do you have any experience in changing the parameters, or is it just something you're aware of?

I have no personal experience of this, mainly because the anchors on the GTI are still standard, however, there was an in-depth thread on the Vortex.

Re your comments on VWR, and the likes - I personally very much doubt they would know about this thing.  I raised a thread on the other GTI forum a while back, prompting the likes of RedRobin and Hurdy (along with others) who already had front big brake kits - asking them to check with their suppliers/installers.  Awesome GTI, along with AP Racing both seemed to completely bury their heads in the sand, and seemed to completely dismiss the issue without further investigation!    Anyhow, you can lead a horse to water . . . . 

If you scan over this newly updated thread - http://www.golfgtiforum.co.uk/index.php?topic=54324 - the first manual in the brakes section details the issue (page 5 of 58 if you are short of time  ).

*R32 rears. Yes, as in the full rear set up, calipers/cariers/discs/splash guards. As mentioned it's just the 3rd hole that's an issue... but I still want to physically see it for peace of mind.

OK, understood.    Yup, I am waiting for some real pictures too - before I decide on my own plan of action.

*RS4 fronts. Sorry, I didn't mean I was having them.. they're just "going on" in general. From what I understand there may be a small & easy carrier mod, but it utilises all OEM kit - it may be RS4 calipers and RS6 discs or something? You'd need to ask AMD.

Ahhhh, OK, no worries, thanks for clarifying. 

*Piston size. You confused me here as you were talking about the Autotech kit and I just assumed you were talking about the front AP's they do that'd I've bought recently and why I went into the garb about them not being right - I now see you meant the rear kit they do. D'oh!

LOL, OK, cool!

So, I'd have thought you'd not be able to use the GTI rear caliper as it's designed for a single disc, not the much thicker vented disc of the R32...? that's not to say they're might be using the one from a MKIV Anniversary instead because it's already red and designed for the vented brakes that had? Pure speculation on my part, I don't know.

Ahhhh, my turn for admission of numpty-ness.  I completely forgot about the rear disc thickneses! 

[Teutonic_Tamer]

                       

Too much for the cat, eh? 

[JPC]

to dig this up again, sorry, im going for it! ill report back my finding, next week probably! ;)

[neg]

Nice one, still got round to painting mine - no garage at the mo and if I do it inside I'll get linched

[JPC]

I bet, i guess the house is still undergoing a lot of work? hope its going to plan

[neg]

I bet, i guess the house is still undergoing a lot of work? hope its going to plan

Getting there, couple of slow days due to the weather but still on target, its a race to what happens first - baby or building!

[liamo]

I now have these fitted , if only everything in life was as easy .

[gazbutS3]

nice 1, well done, I take it its not a problem?

[MAT ED30]

Nice one well done

[liamo]

No problem , just need to drill a  hole in  the splash gaurd to fit the third bolt to it . A couple of washers as spacers , a longer bolt and it looks factory .

[gazbutS3]

  o dear egg on the face for someone

[neg]

Thats great, looks like I'll put the full set on mine then being as I have them!

[RedRobin]

....

Very interesting thread

I haven't bothered, as yet, to investigate with either AP Racing or VWR about 'front-rear brake balance', or whatever the correct term is. I tend to go on the principle that if it works, don't mend it and I have more faith in AP Racing's specialist experience than some - I find it too difficult to believe that they wouldn't be aware of such considerations and consequently wouldn't do something about it if they thought it important. But, I'm keeping an open mind and will eventually get around to asking (particularly if I end up in a hedge!).

I'm curious whether anyone here has been experiencing any rear brake problems to merit/justify bothering with this conversion.