Which way to turn this brake bias adjuster?

[DK540]

Two part question... okay, maybe three, or more. I'm still sorta new at this (3 years) so bear with me.

Front brake pads barely worn; rear pads significantly worn. All new Spring of 2017. So, I need more front brake bias, right?

I don't have the dash-mount adjuster, but looking at the one sold by Pegasus, it asks for a counter-clockwise turn to add more front bias. Are they all like that? Does it attach to the threaded rod from drivers right? (gas pedal side?)

If I were little Kevin Harvick, standing next to the gas pedal, facing the bias adjustment rod, I would want to take the giant wrench (think Buster Keaton on the clock face if you're old enough) and turn that counter-clockwise, right?

If the dash mount is for micro adjustment, how much does the max adjustment from the dash turn that threaded rod? Quarter turn? More?

Thanks!
David

[jrh3]

You may want to check. wilwood.com. And possibly other manufacturers' tech pages. I believe they address adjustments.

[Dog Licked Racing]

Inside the tube portion of the brake pedal is a bearing that moves from side to sire within that tube when you turn the screw adjuster. The pressure increases in the master cylinder as the bearing moves toward it.

[problemchild]

The direction of rotation depends on what side you have each master cylinder on and which end of the bias bar you are turning. You are moving the fulcrum point of the bias bar away from the end that is locking up first.

You can read all you want, but until your driver pushes the brake pedal hard enough to start locking up some wheels, it is all theoretical and does not really matter. There are a lot of dynamics that go in to brake pad wear, and it is a factor, but not the major one in determining bias settings. Most old-timers can get the bias very close with the car on stands in the paddock, then have the driver fine tune in a few laps on track, at the the club level anyway. The serious racers can set it with the brake pressure sensor readings and some math.

[farrout]

In that picture, two other things are happening which may render any simple adjustments of the adjuster screw moot. First is that there is a large spacer on the "left" side (looking down). Second is that the two rods going in to the brake cylinders are significantly different in length. It looks like somebody attempted to adjust the brake bias by putting in that spacer and lengthening the rod on that side. If the left brake cylinder (looking down in your picture) is the rears, I suspect that may be the cause of the heavy rear bias. I doubt you will get much further adjustment without going back to a neutral baseline.

In order to get a real adjustment capability, suggest removing the spacer and equalizing the rod lengths. Would also suggest taking it apart and cleaning it all up. Then recenter the bias adjuster and start over. Tilton brake bias inst.pdf I tried to upload a Tilton document on how to adjust their bias adjuster.

[Earley Motorsports]

Looking at the picture, is the rear the one on the right next to the clutch pedal?

[Nardi]

You will also need to be aware of the master cylinder sizes and caliper sizes, not to mention making sure same pad compound front and rear. Disassembly, cleaning and lubing would be very wise as well. To check brake bias statically, put car on stands and use a large clamp or a strap to apply the necessary consistant force upon the brake pedal. I check by hand, fronts damn near impossible to turn, rears a tid bit easier.

[DK540]

From left to right it is gas pedal, rear master cylinder, front master cylinder, clutch. As you can see, the adjuster rod is already angled a bit toward the front brake master cylinder and it does indeed engage first, but maybe not quite enough.

Yes, to respond to an earlier note, I do see a spacer but I believe that was put on to ensure a direct push from the bias mechanism toward the rear brake master cylinder (seems it may have been at an angle otherwise). Yes, it could use a little more cleaning, but it has been vacuumed.

Looking at the picture, is the rear the one on the right next to the clutch pedal?

[DK540]

Yes, same pads front and rear. Properly shamed, twice now, I will do some more cleaning... especially before posting any photos to this white glove crowd! ;-)

You will also need to be aware of the master cylinder sizes and caliper sizes, not to mention making sure same pad compound front and rear. Disassembly, cleaning and lubing would be very wise as well. To check brake bias statically, put car on stands and use a large clamp or a strap to apply the necessary consistant force upon the brake pedal. I check by hand, fronts damn near impossible to turn, rears a tid bit easier.

[kea]

At rest, you want the push-rod going to the front master cylinder to be set longer then the rear push-rod.
In such a way that once the brakes are full on, the bias bar is parallel to the bulkhead.
This has nothing to do with brake bias, front to rear.

[BorkRacing]

Get a copy of Carroll Smith's Prepare to Win and read the brake section...twice or until you understand it. He also has a very good static method of setting front to rear bias. I have used it for 20 years, it works.

Robby

[DaveW]

...First is that there is a large spacer on the "left" side (looking down). Second is that the two rods going in to the brake cylinders are significantly different in length. It looks like somebody attempted to adjust the brake bias by putting in that spacer and lengthening the rod on that side. ...

It looks to me that the spacer was installed to get both master cylinder rods in line with the masters. This would reduce friction in the masters and make brake torque more linear with pedal pressure. It may or may not make the bias hard to adjust, depending on where the pivot point bearing is in the tube.

Having the 2 rods different in length does not directly affect the bias unless they are a LOT different and binding the mechanism. Binding would be more likely with no side clearance to the clevises, which looks like it is the case here. So I would make the rods equal length and leave more space between the clevises and tube.

After you do that, then bias should be set to make the car controllable under braking w/o excessive front lockup. Pad wear may be a result of LD19's in the rear and LD20's in the front or the rear pads are just older, or the rear caliper pistons are not retracting properly.

Here is a page I wrote about brake issues:

[mark elder]

Brakes are important.

If it was me, I would pull everything out and clean it up. The adjuster bar and bearing etc etc need to be a good fit, clean and well lubed (and everything should move easily). Chase every thread. I would rekit the master cylinders too.

I would buy the Wilwood cable adjuster kit and make sure it all fits and works on the bench.

I would then replace the seals in the calipers and check that the pistons are all free etc.

Only then do you know you have a brake system that will work properly on all 4 wheels

Then I would search up this site for the recent thread on setting the bias.With a friend or a clamp, have the rake pedal firm enough that you can just turn the front wheels; then check the rears, they should be just as hard to turn. If not, adjust the bias; you will soon work out which way is correct. The Wilwood kit has 2 stickers for the adjuster; choose the correct one...

Job done.

[DaveW]

Thanks, Mark. I often make the mistake of assuming people maintain things properly, so I only mentioned factors other than maintenance in a solution.

[sevenselans]

It was my impression from previous posts that one wanted the front to be locked and the rears just turning, with the brake pedal on. Easy to do with a C clamp. 1 person job.

chris

[DaveW]

It was my impression from previous posts that one wanted the front to be locked and the rears just turning, with the brake pedal on. Easy to do with a C clamp. 1 person job.

chris

That may be a usable place to start, but the only way to get the bias correct for a specific track on a specific day is to dial it in on the track. The in-the-shop method assumes you know exactly what ratio of front-to-rear brake torque you need, and that depends on weight distribution, suspension setup, tire diameter, tire compound, track configuration & abrasiveness, etc. So dialing it in as you run is, IMO, the only way to get it right.

[TimH]

That may be a usable place to start, but the only way to get the bias correct for a specific track on a specific day is to dial it in on the track. The in-the-shop method assumes you know exactly what ratio of front-to-rear brake torque you need, and that depends on weight distribution, suspension setup, tire diameter, tire compound, track abrasiveness, etc. So dialing it in as you run is, IMO, the only way to get it right.

Weight transfer is different for every corner...

[DaveW]

That may be a usable place to start, but the only way to get the bias correct for a specific track on a specific day is to dial it in on the track. The in-the-shop method assumes you know exactly what ratio of front-to-rear brake torque you need, and that depends on weight distribution, suspension setup, tire diameter, tire compound, track abrasiveness, etc. So dialing it in as you run is, IMO, the only way to get it right.

Weight transfer is different for every corner...

Obviously, another reason you need to adjust at the track...

[Steve Davis]

In my earlier years with a bias adjuster, I placed too little clearance between the center cup and the pivots on each end. It is CRITICAL to make certain that there is NO binding on that sliding ball inside the cup. If you have a little too much clearance, everything still works and bias is adjustable. Too little clearance that there is NO TELLING what you will get. Since I opened up my clearances, I have had excellent results with bias adjustment. Also .. VACUUMING is not "CLEANING".. As said above, take it all apart, clean everything and reassemble. Lube is questionable.. the more you put on, the more it attracts dirt. I put a very small amount of silicone spray and make sure it has plenty of time to DRY COMPLETELY before getting on the track with it. Dirt is your enemy of moving parts. NO LUBE is way preferable to TOO MUCH lube. And.. as also mentioned above, the angles of the adjustment bar are only important at FULL BRAKE APPLIED. The rest position (as in your picture) is almost irrelevant.

[BorkRacing]

In my earlier years with a bias adjuster, I placed too little clearance between the center cup and the pivots on each end. It is CRITICAL to make certain that there is NO binding on that sliding ball inside the cup. If you have a little too much clearance, everything still works and bias is adjustable. Too little clearance that there is NO TELLING what you will get. Since I opened up my clearances, I have had excellent results with bias adjustment. Also .. VACUUMING is not "CLEANING".. As said above, take it all apart, clean everything and reassemble. Lube is questionable.. the more you put on, the more it attracts dirt. I put a very small amount of silicone spray and make sure it has plenty of time to DRY COMPLETELY before getting on the track with it. Dirt is your enemy of moving parts. NO LUBE is way preferable to TOO MUCH lube. And.. as also mentioned above, the angles of the adjustment bar are only important at FULL BRAKE APPLIED. The rest position (as in your picture) is almost irrelevant.

Carroll Smith once told me cleanliness is next to 1st place. He also said in SCCA if your car can last to the end of the race (as in proper prep) you will get at least 3rd place!

Robby

[Earley Motorsports]

Ever see a dirty Indy or F1 car before a race? I haven't. Personally I clean my car whenever I can. In doing this I am also checking for loose bolts etc. Good practice to get into. Plus they look nicer clean and dirt is weight. Off topic, I know.

[Neil_Roberts]

There is a good way to set your brake bias during a warmup lap, if you have a cockpit adjuster cable that actually works and you have a finely tuned ability to feel what the car is doing. Here is the procedure:

Do this when you are almost done with the left-right-left-right "conga line" tire warming. Set the car in a constant speed, constant throttle, hard cornering condition, then brush the brake pedal with your left foot and pay very close attention to how the car responds. If adding braking adds understeer, you have too much front bias. If adding braking adds oversteer, you have too much rear bias. Adjust the bias bar, try it again, and adjust again. This sets the bias for the exact conditions of the moment, without risking a flat-spotted tire.

[DaveW]

There is a good way to set your brake bias during a warmup lap, if you have a cockpit adjuster cable that actually works and you have a finely tuned ability to feel what the car is doing. Here is the procedure:

Do this when you are almost done with the left-right-left-right "conga line" tire warming. Set the car in a constant speed, constant throttle, hard cornering condition, then brush the brake pedal with your left foot and pay very close attention to how the car responds. If adding braking adds understeer, you have too much front bias. If adding braking adds oversteer, you have too much rear bias. Adjust the bias bar, try it again, and adjust again. This sets the bias for the exact conditions of the moment, without risking a flat-spotted tire.

This procedure, IMO, ignores the effect of chassis pitch angle change on braking stability. When you are braking hard, the chassis rear and the rear roll center rise, and the front roll center falls, the resulting pitch-angle change creating oversteer by itself if you are braking while cornering. You will not see that in a slight brake application as suggested above. So if you adjust as Neil suggests, the first time you brake hard while cornering, you likely will have way too much oversteer. That will not be what you want.

So, IMO, the only way to adjust bias for actual race conditions is to do it under actual race conditions.

[TimH]

So, IMO, the only way to adjust bias for actual race conditions is to do it under actual race conditions.

You're right of course. But Neil's suggestion is perhaps a good supplement to the standard static Carroll Smith technique for getting a first approximation. Again, the exact right proportion will change with every corner and few of us make that adjustment every lap.

Though I hear the pros will fiddle the sway bars between corners...

[DK540]

I do appreciate all the good advice, though some of it is waaay beyond my current abilities, time limits and pockebook to accomplish. However, for the cleanliness nuts out there (and I do clean the car frequently!) I did remove, disassemble, clean, lube, reassemble and reinstall the brake pedal assembly over the weekend. So, I will sleep better and brake more smoothly. And, yes, I have properly bled the brakes. I still don't know which way to turn the adjusting screw to add more front bias but I will figure that out next weekend, though it's a bit more tedious with only one person.. and a cold garage. ;-)
On a related note, I replaced the worn rear pads with new, blue ones from Keith (yes, I have LD-19s and blue pads all around) and there is some mild scrap when I turn the wheels. This will disappear after a lap or two, right? Or, hopefully, after the bed-in process.

David

[alangbaker]

I do appreciate all the good advice, though some of it is waaay beyond my current abilities, time limits and pockebook to accomplish. However, for the cleanliness nuts out there (and I do clean the car frequently!) I did remove, disassemble, clean, lube, reassemble and reinstall the brake pedal assembly over the weekend. So, I will sleep better and brake more smoothly. And, yes, I have properly bled the brakes. I still don't know which way to turn the adjusting screw to add more front bias but I will figure that out next weekend, though it's a bit more tedious with only one person.. and a cold garage. ;-)
On a related note, I replaced the worn rear pads with new, blue ones from Keith (yes, I have LD-19s and blue pads all around) and there is some mild scrap when I turn the wheels. This will disappear after a lap or two, right? Or, hopefully, after the bed-in process

If you know which master cylinder is which, then you know which way to turn the adjuster to change the bias:

Turn the adjuster to move the bearing in the middle closer to whichever master cylinder you want to give more bias to.

For example, assuming the master cylinder for the fronts is on the right, and that the thread of the adjuster is a standard right-hand thread, then you would turn the adjust counter-clockwise to move the bearing more to the right.

[DK540]

Exactly what I was thinking, Alan, and makes sense when you look at the dashmount adjuster sold by Pegasus.. showing front to be a counter-clockwise turn. Once I get the wheels back on this weekend I will test that out along with the static method, however, since I installed new rear pads and they need to bed-in and wear down a thousandth or two, I will wait 'til after the first practice at Wild Hare to set it properly. Thanks!

DK

If you know which master cylinder is which, then you know which way to turn the adjuster to change the bias:

Turn the adjuster to move the bearing in the middle closer to whichever master cylinder you want to give more bias to.

For example, assuming the master cylinder for the fronts is on the right, and that the thread of the adjuster is a standard right-hand thread, then you would turn the adjust counter-clockwise to move the bearing more to the right.

[Fred Michael]

The picture in the Pegasus catalog is generic. The knob turns both directions and which way is front is entirely dictated by which side the front master cylinder is mounted on. The knobs come with multiple stickers that point opposite directions.