Brake install help

I bled my brakes (Wilwoods) today - no leaks anywhere, no air left in the lines, and a rock solid pedal. However, it left me with 3 mysteries

1 - I can spin the tires by hand, however I can feel/hear a slight drag. I think this is okay since everything is brand new and has to bed in? (if I recall when I did my Cobra's Wilwoods, I had the same thing - initially a slight drag that went away after a few miles of driving)

2 - I've only got like 1'' of travel on my brake pedal after being fully bled. It's rock hard and holds pressure perfectly, and if I open a bleeder screw, the pedal sinks all the way down (with no air coming out), so I know that's good. But it feels more like an off/on switch because of the limited travel (about an inch worth of travel). Any thoughts on what could be causing this? I don't want the pedal to sink all the way down, but i would like some travel on it. I'm thinking the residual valves, but don't I need them since the master cylinders are below the calipers? Other than that, I don't know what could be restricting travel? For what it's worth, at the end of teh travel (e.g., 1'') the brakes are locked solid, but it's more like an off/on switch right now (no brake or full brake)

edit: the only thing I can possibly think of is this is how the manual brakes work in this car (as any googling references to no pedal travel indicate a failed pump, but not pumps here), but I'm not certain I buy that because my cobra is 6piston Wilwood manual brakes and the pedal has 'normal' amount of travel.

3 - Other than driving it, how can I tell if i have the balance bar setup to be 50/50?

Your pedal sounds correct...if you want more travel and softer initial feel then change out to smaller master cylinders...

To gauge brake balance you can purchase a pair of pressure gauges that screw into the caliper bleeders and then you can actually see the line pressure ....you should start withy a 60/40 split biased towards the front...and work from there...

1- That's normal.
2- My SLR also has the Wilwoods. The feel is exactly the way you describe it.
3- What Fran said.


Edit: (Fran answered the questions, but I just threw these up so you'd here a second opinion.)

gt40fran said:

Your pedal sounds correct...if you want more travel and softer initial feel then change out to smaller master cylinders...

To gauge brake balance you can purchase a pair of pressure gauges that screw into the caliper bleeders and then you can actually see the line pressure ....you should start withy a 60/40 split biased towards the front...and work from there...

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Didn't know about the screw-in pressure gauges, thanks.

Like only 1'' of travel on the pedal seems really weird to me - I would have thought others would have made a comment along the way about pedal travel, but I've never read anything on here. Although smaller m/cs does make sense as an explanation on how to get more travel. What was supplied with the kit - 5/8 I believe?

Confirm that your brakes seam correct to me. My GT40 has Wilwoods all the way around and just about 1 inch of travel at brake peddle. By the way I like them that way. I want the peddle to feel firm as soon as I begin to brake in the brake zone. I don't like to wait on them. This will result in a little more foot pressure required by again I like it like that.

The main thing is going to be balance. This is what Fran is talking about. The pressure gauges really make this easy. But it can be done without them if you are willing to take your time and be careful. When you drive the car. Start slowly and try and get a feel if everything is basically correct. What I mean by this is the car stops straight without any pulling to one side or the other, loss of firmness at the peddle, or anything that feels weird.

Do this in a nice big open space where if you pitch it sideways you can't hit anything, and at less than 30 MPH to start. Then once you feel that the brakes work as expected take it up to about 40 or so and do a couple of harder stops. It helps if you have someone watch you do this from the side and try and get an idea which end of the car locks first. Don't run them over! It should be the fronts. Until you have the fronts locking up first don't take it out and drive it anywhere else unless you like driving backwards.

What you are going for is under very hard braking the front tires reach their limit of adhesion just before the rear tires do. This will get you nice controlled, straight stops.

Brake balance is the first performance tuning that should be done after you have all the systems working such a shift linkage, electrical, no leaks, and cooling.

EFNFAST said:

Like only 1'' of travel on the pedal seems really weird to me

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It varies a lot between cars in general - driving a hire car for a couple of weeks makes my normal car feel weird. It doesn't take too long to get used to the differences though.

I wouldn't worry about it now - it's (relatively) easily changed later if you decide that you can't live with it. Besides, don't brakes only have on and off?

I been down this road a few times. The friction on the wheels as you turn them is caused by pressure in the line created by the residual pressure valve. The same is true with the limited travel on the pedal. I had only an inch of travel and I thought the same thing but what I found was as I drove, the pedal would move further. Maybe because of the adrenalin from racing but it felt fine.

I pulled the residual valves out on my GT40 because I wanted some more pedal feel, not so on or off and it worked good. It was just different. You don't need the valve, it is your choice. The position of the master cylinder isn't relevant, it is the position of the reservoirs which should be higher than the calipers.

Hope that helps.

I'm going to buy a pressure gauge after and take a reading - no guessing for me, I suck at that, haha. Beyond that I guess i just have to wait and see how it drives - it just seems really fricken weird to me to have an off/on switch as a brake pedal almost.

rnixon said:

I wouldn't worry about it now - it's (relatively) easily changed later if you decide that you can't live with it. Besides, don't brakes only have on and off?

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Easy is relative, haha

Alex, you should have an adjustment on the plunger rod for the brake MC - if you're feeling some drag on the brake calipers with no pressure on the pedal you may need to put a bit of slack into the adjustment to take out any line pressure. If the adjustment is too tight (ie. no slack) the brakes will heat up as you're driving and eventually lock up on you. Ask me how I know.

Putting a bit of slack into the adjustment will also give you a bit more travel on the pedal. If it's still too much of an on/off switch then go to a smaller MC as Fran suggested.

The drag is very slight though - I recall this similar in my cobra; after a few miles of driving everything wore in and it was all good.

But it couldn't hurt to play with the pushrods a bit to see if I can see any difference.