kmagvette

I have been truing up the radial taper on a sanding disk table. I was wondering if anyone has tried a cutting tool on a drill press with the pad in a cross vice, if so, what cutter are you using?

The very coarse sanding disk works alright but takes a while on bigger and harder pads like 7790 PFC-01's and makes a mess on what really is a woodworking tool.

RDnomorecobra

I don't. Just flip em to even out the wear.

kmagvette

Flipping will remedy longitudinal taper...I do that.

RDnomorecobra

Ah. Sorry. Gotta work on my vocab. Never had that issue I guess.

ErnieN85

I don't either its usually caused by caliper that have spread. so at that time I toss the calipers for something better.

flink

Member Sidney has had a bunch of pads from different manufacturers flattened by a shop using a surface grinder. I took my Hawk DTC70's to the guy and they destroyed two wheels without him finishing a single pad. So it depends.

I've tried various things and what works best is a belt sander using an Alumina Zirconia belt like http://www.woodworkingshop.com/product/pl84586/. It removes material at an astonishing rate when the belt is fresh - much too fast and you need to be careful. After a couple of minutes things settle down and you can get going.

If the pads are a bit thin you risk grinding your fingertips off so I hold them using the magnetic base off a dial indicator - it has a little on/off **** on it, which is convenient.

When the belt gets too blunt (3-4 pads?) you can flip it around to use the other side of the grain, get another couple of pads out of it.

Overall, it's pretty tricky and requires some technique and practice. But I can get them flat to within 0.2 - 0.3mm nowadays.

It all rather sucks. I should get better calipers.

kmagvette

Ugg, somehow I knew this was going to degenerate into a caliper discussion. I can assure you that caliper quality is not the issue.

As for the grinding, a 16" with 36 grit floor sander abrasive does work, it is just slow. Nothing tricky as the disk is at 90* to a steel table, so with a square push block (and heat resistant gloves) all it takes is time. A benefit to this approach is that the only taper it attacks is radial whereas a cutter would also address longitudinal taper. As noted above longitudinal taper is easily remedied by flipping pads.

Soloontario

So do any of you guys with BBKs get radial taper i.e the pad wears more the further it is from the centre of the hub?

I would have expected it due to the higher rotor speed the further you get from the centre of the rotor. Just not sure how important this speed differential is vs the potential for Caliper spread.

Bill Dearborn

Keith,
Why bother? The pads won't last any longer if you reduce the thickness down to the lowest point.

Surviving the winter? It was in the 60s the last two days and in the 50s today but raining most of the day and night. Expect some cold weather in the teens overnight and 40s in the day time by the weekend.

Ever think about trailering down to VIR?

Bill

kmagvette

Sunday we should make it up to 1 whole degree...and I have a ski race.

VIR is on the list of tracks I want to get to. Would love to do Road Atlanta to see if I learned anything since my first track day (Panoz).

After my experience with the pistons getting locked in the bores due to radial taper (cheaper Wilwoods, several occasions) I have been squaring up the pads and have had no issue since then.

My pads now start out at 25-28mm thick, so they have lots of time to build radial taper. I dumped a boat load of cash into the fronts and they are awesome, but a little radial taper is still there...I probably could ignore it if I weren't so damn ****.

After playing with stock brakes, Wilwoods, StopTech (briefly), and several AP setups, all get some degree of radial taper. The trend I have observed seems to be the smaller the rotor, the more radial taper; also observed on very high quality kits. The stock setup has serious issues, but I now discount "caliper spread" as the major contributing factor to radial taper...there probably is some spread.

I have theories on why various systems exhibit different degrees of radial taper...but that is not the purpose for this thread.

flink

Taper causes a long pedal due to piston cocking - when you release the pedal the piston straightens up in the bore, causing one side of the piston to spring back from the pad. I find that once that gap reaches about 0.006" the pedal travel is unacceptable.

It's worse for me (e36) because I have no brake assist. The pedal ratio and piston sizing have been modified so that I have 3x higher-than-stock mechanical advantage, which means that I have 3x less-than-stock piston travel.

(Wilwood SL6R calipers, 13" rotors. They get both radial and circumferential taper and most of the problem is due to the radial taper).

Soloontario

So on the stock sliding caliper, how much of the longitudinal taper is due to the play in the sliding pins in the pad abutment bracket allowing the caliper to shift relative to the bracket?