AP brake upgrade a little too powerful?
17 February 2009, 04:49 PM
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AP brake upgrade a little too powerful?
I recently got the AP 4 pot kit from Godspeed for my classic and thanks, in a large part, to the wonderful weather we've been having recently I've not really had a chance to use them in anger after the 300 miles of bedding in. But last night I got a chance to hit the brake pedal with a bit of enthusiasm and that caused big retardation following by a quite a pronounced oscillation between what was apparently the wheels locking and unlocking. It was a bit like the ABS was suddenly working in a damned sight more clumsy fashion than it had been with the OEM brakes.
What could be causing this: is there something else I need to upgrade, or is this par for the course with powerful aftermarket brakes and one simply has to modulate pedal pressure accordingly?
Ta for any advice.
Ns04
What could be causing this: is there something else I need to upgrade, or is this par for the course with powerful aftermarket brakes and one simply has to modulate pedal pressure accordingly?
Ta for any advice.
Ns04
17 February 2009, 05:04 PM
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never had a problem with the abs, are you sure you didnt just hit a big pile of grit, as this seems to drive the abs wild
When I upgraded to the ap 355 on stock wrx stuts ( all be in with prodrive springs) I found the car very un balanced when braking from speed
as soon as I fit my extc coil overs this went and the car feels as it should be
When I upgraded to the ap 355 on stock wrx stuts ( all be in with prodrive springs) I found the car very un balanced when braking from speed
as soon as I fit my extc coil overs this went and the car feels as it should be
17 February 2009, 05:19 PM
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I've read that the ABS is calibrated for the brakes on the car (OE) and if you replace them with bigger volume (or smaller I suppose) brakes, and probably, to some degree, bigger rotors, the systems calculation/tables get it all wrong.
I have bigger brakes than OE and have only noted much better braking myself! (Brembo 4pot vs Suaru 2pot...)
On the other hand I had a very 'snakey' car on hard braking (race tyres on track-braking)with the 1pot rear brakes... disappeared with brembo 2pot rears.
I have bigger brakes than OE and have only noted much better braking myself! (Brembo 4pot vs Suaru 2pot...)
On the other hand I had a very 'snakey' car on hard braking (race tyres on track-braking)with the 1pot rear brakes... disappeared with brembo 2pot rears.
17 February 2009, 05:20 PM
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never had a problem with the abs, are you sure you didnt just hit a big pile of grit, as this seems to drive the abs wild
When I upgraded to the ap 355 on stock wrx stuts ( all be in with prodrive springs) I found the car very un balanced when braking from speed
as soon as I fit my extc coil overs this went and the car feels as it should be
When I upgraded to the ap 355 on stock wrx stuts ( all be in with prodrive springs) I found the car very un balanced when braking from speed
as soon as I fit my extc coil overs this went and the car feels as it should be
That is kind of what it feels like though: like you've hit a loose surface and the ABS is confused!! It's a bit unnerving!
Maybe I'm tearing up the tarmac!
Ns04
16 April 2009, 03:35 PM
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I have AP 355mm brake kit and the rear kit on my WR1. I too when heavily breaking on slightly uneven roads get the ABS going ape sh*t. I called RCM who said i need to upgrade from prodrive springs to EX-TC coil overs. They said anti lift kits wouldnt resolve the issue neither would ARB's. They said the best solution is not to brake as hard but then why buy huge brakes if you cant use them to their best? 
16 April 2009, 04:52 PM
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Doubt it will be your suspension mate: The super streets are very well suited to UK roads and I have adjustable dampers and it seems to happen at various settings. I think it's just that the retardation of the brakes exceeds the traction of the tyres. Would probably be ok with slicks!
16 April 2009, 05:11 PM
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I have AP 355mm brake kit and the rear kit on my WR1. I too when heavily breaking on slightly uneven roads get the ABS going ape sh*t. I called RCM who said i need to upgrade from prodrive springs to EX-TC coil overs. They said anti lift kits wouldnt resolve the issue neither would ARB's. They said the best solution is not to brake as hard but then why buy huge brakes if you cant use them to their best?
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17 April 2009, 04:52 PM
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The problem isnt the brakes locking up with me its the ABS coming in on uneven surfaced roads randomly under spirited but not emergency stop style braking... If the council would fix the roads then I wouldnt have this problem
18 April 2009, 09:16 AM
#11
I believe it is possible to disconnect the ABS by removing a fuse?
Might be an idea to try them out at a "track" in this configuration.
21 April 2009, 01:03 PM
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I recently got the AP 4 pot kit from Godspeed for my classic and thanks, in a large part, to the wonderful weather we've been having recently I've not really had a chance to use them in anger after the 300 miles of bedding in. But last night I got a chance to hit the brake pedal with a bit of enthusiasm and that caused big retardation following by a quite a pronounced oscillation between what was apparently the wheels locking and unlocking. It was a bit like the ABS was suddenly working in a damned sight more clumsy fashion than it had been with the OEM brakes.
What could be causing this: is there something else I need to upgrade, or is this par for the course with powerful aftermarket brakes and one simply has to modulate pedal pressure accordingly?
Ta for any advice.
Ns04
What could be causing this: is there something else I need to upgrade, or is this par for the course with powerful aftermarket brakes and one simply has to modulate pedal pressure accordingly?
Ta for any advice.
Ns04
There's a nice write up on the Stoptech site about ABS. The system works on "happy values" derived from real-time testing.
Changing for calipers with different piston sizes or massively increasing the one-time abilities of the front brakes can cause problems. The system isn't configured for it.
Anyways, I thought that the main technical reason for getting bigger brakes was to offset fade caused by repeated hard slow-downs or stops?
J.
21 April 2009, 09:23 PM
#14
Surley braking is only as good as the tyres... Why would bigger brakes cause the abs to go crazy? the tyres are still losing/regaing traction at the same rate?
How come stiffer suspension fixes this?
I can only think the rear has too much brake bias with bigger brakes?
How come stiffer suspension fixes this?
I can only think the rear has too much brake bias with bigger brakes?
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