AP Racing Brakes
Discussion
I seem to be having problems with the feel of my brakes. The problem can be best described as a 'wooden pedal' feeling. On the roads (as opposed to the track) you really have to stand on the brake pedal and even then there is not enough bite. I would have thought that the spec of the AP brakes should be more than enough. I stared of with Mintex M1166 which came with the car and changed to Ferodo DS2500 pads after some research. During the change I have rubbed the discs with 60 grit to remove any residual pad material as recommended. I have even considered adding remote servos to give power assistance. Has anyone else experienced similar problems and if so did you resolve it to your satisfaction?
Many thanks.
Roj
Many thanks.
Roj
Thanks Johnny
I know this isn't the first time I've raised subject. I now think it's more than just a type of pad issue. The road going Radical had similar issues. It seems that the brakes need to really hot or the pressure from the master cylinders needs increasing without the pedal pressure increasing. I am seriously considering adding remote power assist servos to overcome the problem. Just bare in mind that on the track the brakes don't cool as they do on the road.
Anybody fitted power assist?
I know this isn't the first time I've raised subject. I now think it's more than just a type of pad issue. The road going Radical had similar issues. It seems that the brakes need to really hot or the pressure from the master cylinders needs increasing without the pedal pressure increasing. I am seriously considering adding remote power assist servos to overcome the problem. Just bare in mind that on the track the brakes don't cool as they do on the road.
Anybody fitted power assist?
If I go the route of power assisted fitting the servos in the side pods isn't that difficult as you would cut a door in the front of the pod with a recess plate fitted behind to allow the cut out section to be bolted back on. You can then face the door with anti chip material. Someone has suggested on a pm to look at putting the brake bias to 60% on the front. As I have adjustable brake bias I am going to try this.
Hi Dom
I first set them up statically, i.e. stationary by having someone sit in the drivers seat (the wife) and gently press the pedal so that both wheels can be turned by hand. I then adjust the bias until I feel that the balance is 60/40. I then take it on a test drive and make any further adjustments on the fly. This was obviously easier on the track in my racing days and also assumes that you have a remote bias adjuster fitted to your Ultima.
I first set them up statically, i.e. stationary by having someone sit in the drivers seat (the wife) and gently press the pedal so that both wheels can be turned by hand. I then adjust the bias until I feel that the balance is 60/40. I then take it on a test drive and make any further adjustments on the fly. This was obviously easier on the track in my racing days and also assumes that you have a remote bias adjuster fitted to your Ultima.
Just an update after speaking to others. I have master cylinders front 0.75 rear 0.625. I will be changing to 0.625 front and 0.7 rear. This will give greater pad pressure with the same pedal pressure. From my racing days I remember that the front master cylinder always has a smaller master cylinder bore therefore greater pressure on the front than the rear then in wet conditions we then adjusted bias more to the rear with the brake bias adjuster. We will see how this works.
I will let you know how it goes. I gave just ordered a standard Girling remote cylinder 0.7 for the rear. I have noted that some recomend Tilton or AP but at this stage I will just run with the theory on this. I have ordered from Merlin on this occasion. Sorry Mark not sure how to put a link on. Still learning on this.
Hi Pete
I hear what you say but 'the people' have been talking too are top technical on this without mentioning names. The change I am making is putting more pressure on the front pads and less on the rear so I don't see how the rears would locking up, it surely would be the fronts. There are some aspects of this that I don't want to discuss openly as it will cause problems. From my experience the performance of the brakes on my car are not where they need to be and therefore I will be trying to find a solution. I do have an adjustable brake bias system fitted also which allows on the fly adjustment to fine tune. Thanks for your concerns.
I hear what you say but 'the people' have been talking too are top technical on this without mentioning names. The change I am making is putting more pressure on the front pads and less on the rear so I don't see how the rears would locking up, it surely would be the fronts. There are some aspects of this that I don't want to discuss openly as it will cause problems. From my experience the performance of the brakes on my car are not where they need to be and therefore I will be trying to find a solution. I do have an adjustable brake bias system fitted also which allows on the fly adjustment to fine tune. Thanks for your concerns.
Top tip Pete, some of the mechanics used to do that but I'd forgotten about it. Also I checked the build manual this morning and there is a specific measurement for setting the correct brake bias on an Ultima ( I assume this is a dry setting). It relates to the amount of screw thread that should be protruding on the right for right hand drive cars.
Hi Pete
Please let me know if the torque wrench works. I will try it Monday or Tuesday next week.
Dom you are quite correct but I think I covered that in an earlier post hence 0.625 front and 0.7 rear.
Other technical points noted but some of it a bit over my head, as I said earlier I am taking top technical advice on these changes along with my own experience.
Its nice to know that those posting on here are prepared to stand up and say if they have concerns especially safety ones. Thanks guys.
Please let me know if the torque wrench works. I will try it Monday or Tuesday next week.
Dom you are quite correct but I think I covered that in an earlier post hence 0.625 front and 0.7 rear.
Other technical points noted but some of it a bit over my head, as I said earlier I am taking top technical advice on these changes along with my own experience.
Its nice to know that those posting on here are prepared to stand up and say if they have concerns especially safety ones. Thanks guys.
Hi Max
Thanks for the technical info which mostly went straight over my head. Thats why I rely on my own experience i.e. feel, and where I don't understand something then speak to people who fully understand the technical side.
Regarding the Ultima the callipers and discs are the same size all round hence one of the reasons for the discussion on the master cylinders.
Thanks for the technical info which mostly went straight over my head. Thats why I rely on my own experience i.e. feel, and where I don't understand something then speak to people who fully understand the technical side.
Regarding the Ultima the callipers and discs are the same size all round hence one of the reasons for the discussion on the master cylinders.
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