I have exchanged a couple of e-mails with a helpful chap at AP Racing.
They supply TVR Power with front pad # CP6600D55-DS2500 and rear pad # CP3915-42-DS25HP .
So the front is a Ferodo DS2500 branded as AP, and the rear DS25HP is a “comfort version (low compressibility) of the DS2500 but fairly similar in performance”.
To quote AP:
“Comfort basically means road pad with no noise issues; although not always the case with performance pads but that also depends on the installation.
So where DS2500 may produce squeal on certain installations 25HP may cure it and on a rear end light load pad that’s also required as a park brake then 25HP would be the best option i.e. works from cold but with good fade resistance.
Low Compressibility reduces pedal travel.
DS2500: – Mu 0.34 from cold to 600°C
DS25HP: – (similar to our APF404 compound)” – The chart below says 0.35
A link was provided to an AP Pad Characteristics chart.
Also from AP:
So you could fit CP6600D55-APF404 to the front. But don’t think it’s the pad compound causing the imbalance, these are both road car compounds so need to work from cold and I doubt you got top the point of fade for either yet?
The APR bias valve if plumbed in correctly will reduce rear line pressure, with a very slight delay as the valve comes into operation.
The rear brake being a single pot pin slider, must be fairly small regards piston area and disc diameter when compared to the front 4 pot set up, so I would expect front bias to be designed in.
Is actuation via a twin bore / tandem M/cylinder, if so is this in good condition?”
It looks like I could do a bit of work if I can find the piston areas to see what the brake force distribution is like in the static case. Not sure how to test the master cylinder other than to have it changed.
Very useful responses from AP. I knoe exactly what rear pads are fitted, but am not 100% sure about the fronts. They should be the D2500 compound, but I haven’t seen it for myself.
Having re-found this photo that I took of the rears after fitting, I at least know exactly what they are.