surging brakes

[Mondo]

Can something other than warped discs cause this? Seemed I was coming to a stop, lightly applying the brakes, and this started but a few stops later it was gone.... weird.

The brakes don't pump up like you get normally when there's air in the lines.

[slngsht]

what do you mean by surging? do you mean the pedal was pulsing under your foot?

[JohnK]

The Ultralites I know of are fitted with steel disks/rotors. Talking to Wilwood a while back, and noting that they list their steel rotors for use in drag racers, I was told that street use of steel rotors causes the rotors to become bell shaped over time (as in Bellville washers). Exactly what symptoms this produces I don't know, but I doubt that it's desirable. If I remember correctly the word "spongy" was used by Wilwood tech. Cast iron has very favorable properties for the kind of circumstances faced by rotors in street or road racing usage. Re-fitting with such would take some work.

Bedding in new pads is a little involved (mostly from the problem of finding suitable space in which to do it) and I haven't read of many people going through the procedure, but AFAIK improperly bedded pads only give less-than-optimal stopping. Check out the Wilwood site for instructions. I seem to recall that going over the rotors with garnet paper gets rid of glazing so you can start over.

[MHKflyer52]

Can something other than warped discs cause this? Seemed I was coming to a stop, lightly applying the brakes, and this started but a few stops later it was gone.... weird.

The brakes don't pump up like you get normally when there's air in the lines.

 

Hi Mondo,

 

Sometimes the rotors will get a little oxidation / corrosion on the when the car is stored or has been sitting for a couple of days. (Rotor turns gray to a rust color especially after the car has been washed then stored especially if a wheel cleaner has been used to clean the rims as they usually remove all oils that are picked up on the rims from the road surfaces which help hold the brake dust and dirt to the wheels) The area under the brake pad usually dose not have as much of the oxidation under it so if you rotate the wheel and look at the rotor it is usually clean underneath of the brake pads especially on the rear rotors due to the parking brake being set. This can cause a very slight pulse that you described if you put very light pressure on the brakes and will usually go away with in a few yards of movement unless the rotors are very rusted or corroded badly. I do not know what type of rotors you have but as the other post has mentioned if you have steel rotors this will be more evident than if they are cast rotors. It also tells me that your brakes system is very well balanced if this is occurring and that your front to rear ratio is most likely very close to natural (front wheels lock at the sometime as the rear wheels). I have my car set up so that the rear wheels will lockup just a split second before my fronts in a full panic stop on public roads with street tires so that I have steering to the last instant (this changes with tire composition and road surface so it is something that one needs to adjust for different driving conditions).

Just my observation and belief and in no way am I an expert in this area so take what I say with a grain of salt and enjoy your car and be safe.

[DB6]

Hi Mondo,

 

Sometimes the rotors will get a little oxidation / corrosion on the when the car is stored or has been sitting for a couple of days. (Rotor turns gray to a rust color especially after the car has been washed then stored especially if a wheel cleaner has been used to clean the rims as they usually remove all oils that are picked up on the rims from the road surfaces which help hold the brake dust and dirt to the wheels) The area under the brake pad usually dose not have as much of the oxidation under it so if you rotate the wheel and look at the rotor it is usually clean underneath of the brake pads especially on the rear rotors due to the parking brake being set. This can cause a very slight pulse that you described if you put very light pressure on the brakes and will usually go away with in a few yards of movement unless the rotors are very rusted or corroded badly. I do not know what type of rotors you have but as the other post has mentioned if you have steel rotors this will be more evident than if they are cast rotors. It also tells me that your brakes system is very well balanced if this is occurring and that your front to rear ratio is most likely very close to natural (front wheels lock at the sometime as the rear wheels). I have my car set up so that the rear wheels will lockup just a split second before my fronts in a full panic stop on public roads with street tires so that I have steering to the last instant (this changes with tire composition and road surface so it is something that one needs to adjust for different driving conditions).

Just my observation and belief and in no way am I an expert in this area so take what I say with a grain of salt and enjoy your car and be safe.

 

Martin, how do you adjust front to rear bias ?

[MHKflyer52]

Martin, how do you adjust front to rear bias ?

 

Hi David,

 

I have an adjustable proportioning Valve in my brake system that I purchased from SpeedWay Motors.

Here is the link for the valve I have...

 

http://www.speedwaymotors.com/Compact-Adjustable-Proportioning-Valve,1979.html

 

Here is another link for a fancier one from SpeedWay Motors.....

 

http://www.speedwaymotors.com/Wilwood-Proportioning-Valve-Knob-Style,6494.html

 

I like the one that I have as I can also use it as a brake lock by applying the brakes then closing the valve all the way and it will keep the brakes locked and no one can tell if I want to due that.

You can also buy pedal setups that have an adjuster (balance bar) built into the assembly that lets the amount of force applied to the master cylinders when the pedal is depressed.

Wilwood makes a good setup but they are a little expensive and have to be looked after all the time plus some states do not allow balance bar adjusters in street cars for oblivious reasons.

Hope this info helps.

[WestTexasS2K]

Rotors on the Ultralite should last you for years of track and street driving. My car had a little bit of a surging at times as well I never did figure out exactly why it did it. If I applied just a little more pressure it would quit.

[Mondo]

Thanks, I think that's it.

It was only noticable with light pressure and the last 20ft coming to a stop. I still need to do some hard braking and check the balance bar as well.

 

I'm realizing this is more race car than street car and getting used to what noises are ok and what's not... may pull the carpet and tank out in the trunk area (if you can call it that) and add some sound deadening to help with rattles... made a big difference in my 67 truck. Of course once you get up to speed all that goes away with the wind noise

Edited March 28, 2009 by Mondo