AP Brakes users - Opinions please
Discussion
I have just had fitted AP 4 pots to my E30 M3. Ran the car at Outloon on Saturday and to say the least I am not a happy camper.
I am using Ferodo DS2500 pads and have proper ducting to back plates.
Either with the ducts fully open or closed I found the braking very inconsistent. You get an initial bite (but not a throw you out of the seat bite) followed by a period of very little retardation and then a big stop when at very low speed. Surely this isn't right. I was at times thinking I was going to hit people in front of me, I didn't as the car pulled up, but it wasn't confidence inspiring.
It would be interesting to hear other people's experiences, I have no reason to doubt that the hardware is good and can be made to work properly, or am I expecting too much.
One final point, with the engine off I have a firm pedal but it will slowly sink down under pressure, is this normal ?
I am using Ferodo DS2500 pads and have proper ducting to back plates.
Either with the ducts fully open or closed I found the braking very inconsistent. You get an initial bite (but not a throw you out of the seat bite) followed by a period of very little retardation and then a big stop when at very low speed. Surely this isn't right. I was at times thinking I was going to hit people in front of me, I didn't as the car pulled up, but it wasn't confidence inspiring.
It would be interesting to hear other people's experiences, I have no reason to doubt that the hardware is good and can be made to work properly, or am I expecting too much.
One final point, with the engine off I have a firm pedal but it will slowly sink down under pressure, is this normal ?
Only just fitting mine to my wedge so I can't comment on the actual use. But your pedal sounds the same as mine was, which is leaking past the seals in the master cylinder. Could explain your inconsistent performance as well. Have you thoroughly bled the system as this will also cause the same problems?
Will give an ipinion on AP performance once mine is up & running. Good luck,
Mick
Will give an ipinion on AP performance once mine is up & running. Good luck,
Mick
I have AP 4 pots and DS2500 pads in my Ultima - no servo assistance. The pedal feel is excellent and very consistent once pads are warm, and as yet no hint of fade on track. The only downside IMO is that when pads stone cold the pedal is a bit wooden and you need to be careful initially - pads don't need much heat to start working well though.
I've never had any success with ferodo pads .. always have poor cold performance and very bad feel.
First step i would think is cure the pedal sinking .. sounds indeed like master cyl seals, but also check the servo non-return vacuum valve, if it leaks then you'll lose vacuum when on power, but only get servo assistance when you've built vacuum back into the servo after decelerating .. could explain the end-retardation if the servo is gaining assistance throughout the stopping period.
I'd also advise junkng the ferodo pads and getting something more consistent .. we use mintex 1166 on our race car and they're fantastic.
First step i would think is cure the pedal sinking .. sounds indeed like master cyl seals, but also check the servo non-return vacuum valve, if it leaks then you'll lose vacuum when on power, but only get servo assistance when you've built vacuum back into the servo after decelerating .. could explain the end-retardation if the servo is gaining assistance throughout the stopping period.
I'd also advise junkng the ferodo pads and getting something more consistent .. we use mintex 1166 on our race car and they're fantastic.
rlk500 said:
Thanks. Gdr, do you get a consistent stop when hitting the brakes, also do you have any ducting to the brakes ?
TIA
Yes, stopping power is very consistent and linear with pedal pressure. I don't use brake cooling ducting, but as brakes are big (320mm), car is relatively light (1000 kg), not on slicks and I am a bit of a track novice anyway, I'm probably not as hard on brakes as some.
Sounds like you may have a problem with master cyl or servo as mentioned by others though.
Some types of pad are very sensitive to being bedded in properly. Did you follow the manufacturers bedding in procedure?
On the servo front, it would be interesting to know whether the brakes behave differently when you nail them immediately from hard acceleration, versus coasting on a trailing throttle for a couple of seconds first. This would show whether the servo was seeing full vacuum immediately, although if you have just changed the brakes there's no particular reason to suspect a servo fault.
If the brakes are working correctly you should be able to lock all four wheels at any speed (subject to ABS) although trying this at very high speed can be dangerous and expensive on tyres!
On the servo front, it would be interesting to know whether the brakes behave differently when you nail them immediately from hard acceleration, versus coasting on a trailing throttle for a couple of seconds first. This would show whether the servo was seeing full vacuum immediately, although if you have just changed the brakes there's no particular reason to suspect a servo fault.
If the brakes are working correctly you should be able to lock all four wheels at any speed (subject to ABS) although trying this at very high speed can be dangerous and expensive on tyres!
Thanks guys. I have spoken to the guys who fitted the kit, who were most apologetic that all did not appear to be well and we discussed what to do. As I am a fair distance from them, I have been supplied with a list of items to check, but ultimately as most have implied, it seems most likely that there is a problem with the master cyclinder or I have a leak somewhere.
Hi, I have AP calipers and discs on my Esprit with ferodo ds3000 (!) pads. They grip and stop the car in a very short time. I don't hammer them from cold because I warm up everything , engine, brakes and cabin first so all is in harmony. They apparently wear discs quickly but the impressive stopping power makes it worth it for now, may get some DS2500 soon though.
Good fluid and braided hoses are fitted and are a must for improved stopping power.
Dom
Good fluid and braided hoses are fitted and are a must for improved stopping power.
Dom
I have now bedded the brakes in carefully to the manufacturers instructions. Bit of a pain but seems to have been worth it. The brakes have a nice feel, not too firm but not huge amounts of travel like before. They seem to pull the car down from speed with no fuss or fade. Had a good workout on the way to BTaP and again on Sunday with the club.
So far, very very pleased, a good investment, making the car even more of a joy to drive
So far, very very pleased, a good investment, making the car even more of a joy to drive
I used to run my road car on DS11 pads. The thing to realise is that brake pad mu level varies according to temperature. So you need to select for application.
A hillclimb car needs low temp high mu and will never warm it's pads so the rest is irrelevant.
A racer or track day car needs the brakes to take a good pasting, but that often is at the expense of cold performance.
Better for a road car used occasionally at the track to have a medium spec pad that is consistent mu at the range of temperature it works under, if required change pads at the circuit if you have a daily driver as your race car.
A hillclimb car needs low temp high mu and will never warm it's pads so the rest is irrelevant.
A racer or track day car needs the brakes to take a good pasting, but that often is at the expense of cold performance.
Better for a road car used occasionally at the track to have a medium spec pad that is consistent mu at the range of temperature it works under, if required change pads at the circuit if you have a daily driver as your race car.
Ultima use AP.
100mph to zero in 3.9 seconds
Yes, I think they work OK.
Flash claims aside, I have them on my Ultima and they are without servo so slightly on the hard side but are progressive and very powerful. They are still easy to live with in normal day-to-day road use.
Another point on brake pressure is that normal braking requires so little pressure (due to the size of the discs) some of us have found that it is not triggering the pressure operated brake switch so we have replaced them with adjustable switches.
My only down side is that they squeal at low speed and brake pressure.
Steve
100mph to zero in 3.9 seconds
Yes, I think they work OK.
Flash claims aside, I have them on my Ultima and they are without servo so slightly on the hard side but are progressive and very powerful. They are still easy to live with in normal day-to-day road use.
Another point on brake pressure is that normal braking requires so little pressure (due to the size of the discs) some of us have found that it is not triggering the pressure operated brake switch so we have replaced them with adjustable switches.
My only down side is that they squeal at low speed and brake pressure.
Steve
Thanks fro the comments, gives me a good idea that all is definatley not well. I have recieved a set of Pagid pads to try, which are slightly better, but the car doesn't really pull up any better than the stock brakes did. I have spoken to the guys who fitted them and they are dead keen to have the car back to get it sorted, so it will be going back in early December.
Just a quick update on the brake issues. I returned the car at the weekend and the proprieter drove the car. There I am thinking "what if he comes back and says they are fine.....". I need not have worried. His first comment was something along the lines of "mmmmmm...the're interesting" and then "you drove it here like that, and all they offered you was tea, should have been a large whisky...." So it does appear there is a problem. They are fairly sure that the brakes are working but one of the other systems is failing, either Servo, M/cylinder, ABS control unit etc etc. I await further news.
I have fitted std Tuscan TVR calipers (CP6600) and 300mm rotors and alloy bells. Grooved cross-drilled.
They are fantastic - bloddy brilliant. Well they were after the second full bleed - did the all the hoses to braided at the same time - no brakes firt time up the road. Bled again - Eye Popping.
They are fantastic - bloddy brilliant. Well they were after the second full bleed - did the all the hoses to braided at the same time - no brakes firt time up the road. Bled again - Eye Popping.
I spoke too soon.........bl**dy problems are back. Initial bite then very little, then they come back strong again as the car is almost stationary.
The appear to detoriorate over time, which would imply a leak, but then I would have thought it would be mushy all the time.
I have a new master cylinder on ordere to go in, fitters would like to replace the bias valve again as this fixed it last time. So It's MC first, then another bias valve if that doesn't sort it.
The appear to detoriorate over time, which would imply a leak, but then I would have thought it would be mushy all the time.
I have a new master cylinder on ordere to go in, fitters would like to replace the bias valve again as this fixed it last time. So It's MC first, then another bias valve if that doesn't sort it.
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