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Discussion Starter #1
Hello!
So there i am. And i searched the forums but never quite got the answer to my question and problem at hand.
The car: GTV P2 3.0
The situation: Car failed MOT on rear brakes although new brake pads, braided hoses, couple months ago overhauled brake pistons (seals, etc), cleaned and greased guides. The hand brake isn't holding the car even on a slight hill.
What i am looking for: Rear brakes that actually work. And handbrake that does not fail mot. Plus recommended increase in size of the disc and brake calipers. As they look ridiculous on 19" and in front i have 355 mm brakes.
Given all this info the option to just overhaul the calipers ain't no more option. They'r done. I have to buy new calipers. OM or increased in size.
I found the Tarox upgrade kit, but that's just increasing the disc size and using the original calipers.
Then someone mentioned that one can fit 156 FL and GTA rear brakes. Never found confirmation of that. And 156 brakes are fitted in front part of the brake disc but GTV caliper sits on the back side of the brake disc. How will hand brake work after that?
What is the caliper bracket bolt distance on GTV? maybe someone has the calipers on the table an can measure this.
i got my hands on scraped 156 FL calipers and measured 118 mm between the caliper securing bolts.
Whats with the offset of 156 calipers?

As You see many questions but no answers. Therefore i was hoping someone can give me some information.
 

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Did you reset the handbrake mechanism properly after the work was done? The handbrake will never work properly unless you follow the manual to reset the mechanism.

None of the work you've done ( other than the pads ) has any effect on the handbrake - just the footbrake.

How will hand brake work after that?
It won't. Just swapping the calipers left to right & vice versa to compensate for the calipers needing to be on the trailing edge of the disc won't be enough. The handbrake mechanism would also have to be removed from each caliper and swapped over. Even then, the end stops may not be in the correct place.

Incidentally, have you checked the handbrake cables?

By the way, testing the handbrake to MOT standard is fairly easy. Handbrakes have to operate at 16% efficiency. Sounds terrible right? Just 16%! Except the 16% refers to a 16% hill. Before you go back for an MOT, find a 16% hill ( or preferably a bit steeper ) and park on it. If the handbrake holds the car you can be reasonably confident it'll pass the MOT. I do this as a routine pre MOT check as I have a suitable hill nearby. I stress it a bit more by slipping the clutch a bit as well to get the car moving a fraction, release the clutch and see how quickly the car comes to rest again.
 

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If it's an early phase 2 then rear brake problems are usually caused by the rear brake compensator valve. This siezes partially closed and reduces pressure to rear calipers which might also mean the auto adjust doesn't operate properly hence the handbrake issue. I had the same issue but compensators were not available new so I bypassed it with new brake lines. MOT passed but ABS was activating early. Found a used valve in the end.
 

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As to upgrades. There's very little scope by parts binning. The Peugeot 805 rear discs would be a good option except they are too deep and rub the rear upright. A thin spacer between the disc and hub can solve that but then you'd still need to get a caliper adaptor.

Using the same caliper on larger discs isn't such a problem. The larger disc provides greater leverage so the same caliper can work more effectively.
 

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It refers to brake effort as recorded on a rolling road expressed as a percentage of vehicle weight.
Yes. (total efficiency for both wheels in kgf/vehicle weight)*100 > 16.

Which also equates to a 16% hill where gravity takes care of the vehicle weight.

It'll never be a perfect test of course because a hill will only test the total performance and will not, for example, highlight an imbalance between the wheels. But as a fairly basic pre MOT check, parking on a 16% hill works well enough. At the very least, it'll give someone some confidence when submitting the car for a test.

I know that if the handbrake on my GTV doesn't hold the car on my test hill or doesn't stop the car fairly quickly when I get it moving on the hill against the handbrake ( at very, very low speed ), the car will fail the MOT.

EDIT : I can't recall where I got this info ( it was years ago ). But it is somehow linked to real world brake tests conducted even before the days of accelerometers ( which of course are still used today for some problematic vehicles ).
 

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Discussion Starter #7
Did you reset the handbrake mechanism properly after the work was done? The handbrake will never work properly unless you follow the manual to reset the mechanism.
The cable for hand brake also is new.
What is the correct procedure for resetting the hand brake?
The car is 2001 p2. no idea if it has or no the balancing valve.
 

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If it's an early phase 2 then rear brake problems are usually caused by the rear brake compensator valve. This siezes partially closed and reduces pressure to rear calipers which might also mean the auto adjust doesn't operate properly hence the handbrake issue. I had the same issue but compensators were not available new so I bypassed it with new brake lines. MOT passed but ABS was activating early. Found a used valve in the end.


I absolutely agree with Danny, Ive had exactly the same problems with the rear brakes. Replaced everything in the system, discs, pads, calipers, brake lines, cables and followed the handbrake reset procedure to the letter. All to no real improvement until I replaced the brake compensator !


Sent from my iPad using Tapatalk
 

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Ned at Autolusso persuaded me to ditch my alloy OEM rear calipers and I think he fitted new steel units from the Fiat Punto. My problem was with the alloy caliper binding inside and not returning.
The early Phase 1 cars also have the steel calipers, rather than the later aluminium 'finned' calipers. So far to date this early set-up has never failed an MOT. However the idea of using larger diameter discs with the same calipers is certainly an interesting idea and worth exploring.
 

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Would this be the difference between the Lucas and ATE rear calipers, that swapped at some point during production.
 

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The early Phase 1 cars also have the steel calipers, rather than the later aluminium 'finned' calipers. So far to date this early set-up has never failed an MOT. However the idea of using larger diameter discs with the same calipers is certainly an interesting idea and worth exploring.
Are these the ATE calipers?
 

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Would this be the difference between the Lucas and ATE rear calipers, that swapped at some point during production.
Yes

ATE - steel - 4 fin

Lucas / Girling - Alloy - 6 fin
 

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Are these the ATE calipers?
Apparently not. Lucas also produced a steel version for the early phase 1 with no fins at all, rather four flat ridges toward the back of the caliper - the outward (visible) side of the caliper appears smooth. An example for sale here:

https://www.ebay.co.uk/i/332401819152?chn=ps&dispctrl=1&adgroupid=47842945425&rlsatarget=pla-380312378131&abcId=1129946&adtype=pla&merchantid=6995734&poi=&googleloc=1006774&device=c&campaignid=974959912&crdt=0

I'm getting the rear brakes/pads changed next week so will post up some photos of the calipers on here.
 

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Yes

ATE - steel - 4 fin

Lucas / Girling - Alloy - 6 fin
As pointed out in the ad above, Lucas provided a steel version for the early Phase 1, this is the same on my 916 Spider, no problems with these at all. I gather they were taken from the 155 parts bin at the time.
 
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