Spitfire Spit Does Not Want To Stop

[doates]

Hi,

My 70 Spit has a new brake system; rebuilt MC, new rotors, rebuilt calipers, new wheel cylinders, pads, shoes, etc. Using DOT 5, flushed all the lines. But is has been barely driven since all this went in a couple of years ago.

I have bled the brakes 3 times in the last month. The pedal seems fine; I feel pressure, it is not too hard and does not fade but the car doesn't stop well. I tried adjusting the rear brakes today and even left them a little tight but no change. I have to really stand on it to make it stop.

Any ideas?

Thanks in advance

Dennis

 

[AltaKnight]

Vacuum servo leak?

 

[tdskip]

Does it improve if you pump the pedal? Doesn't sound like it, but classic starting point for diagnosis....

 

[LarryK]

Are the rubber hoses new? Did you pre-bleed the MC before installing? Check differential valve to make sure it is not clogged. Is the MC rod/plunger to pedal the right length?

 

[Andrew Mace]

Dennis, how long have you had the car? In other words, do you know if it used to stop better? I've never had a complaint about any Spitfire's ability to stop well and quickly. Maybe pads need to bed in, or maybe they're glazed or just cr*ppy pads, or any/all of the above suggestions from others. Or maybe you just need to develop more leg muscle.

Don't bother leaving the rear brakes dragging, as they add at most about 30% of the braking.

 

[rikiwho123]

try putting on emergency brake and then start car to see if it moves foward and what type of brake pads did you on the car ones for the street i hope and not racing.My spit stops on a dime with stock pads and shoes; but i remember the 1st time getting behind those brakes after years of driving cars with power brakes big difference.

 

[tdskip]

How are you getting on Dennis?

 

[doates]

Wow! Thanks for all the responses.

I have had the car for 6 years but only drove it for about a month before I took it apart; I don't remember any braking difficulties. The new brake stuff was installed 2 or 3 years ago as a kit from either VB or SpitBits (don't remember)and the car has been outside under a cover until a couple of months ago when I finally got it into the garage.

I wrote the above after putting it away for the evening so haven't been back to it yet. It goes today for new tires and windshield so hopefully the brakes will work well enough to get me there safely. Actually that is what is funny about it; it stops but just not quick enough.

Thanks....Dennis

 

[tdskip]

While the tires are off ask them to check for any leaks or contamination on the disc/pads.

Keep us posted.

 

[doates]

I left out that it has been driven a total of about 6 miles; slow test drives around the neighborhood, since the brake rebuild so maybe it is the pads/shoes bedding in.

 

[TR3driver]

Just a thought, were the rotors and drums cleaned thoroughly, and surfaces scuffed when all the work was done? New rotors frequently come with a thin film of preservative that must be cleaned off with solvent.

Kind of drastic, but might help : try driving for a bit at low speed (1st gear) with heavy throttle and using the brakes to control your speed. Sometimes getting the brakes good and hot will improve operation even after they cool off later. (This was actually recommended "bedding-in" procedure for my Audi.) But do it away from traffic and other obstacles, so you've got room to coast to a stop if necessary. Afterward you can hold your hand near (don't touch!) to see which wheels are working and which are not.

 

[billspit]

Did you bleed the brakes by using the pedal or using a vacuum pump? A vacuum pump may not get all the bubbles out because it isn't a positive seal.

Also, someone asked if you bench bled the master cylinder before installing it. I didn't see a response.

 

[doates]

Bled the system using speed bleeders and peddle. Can't remember if I bench bled MC.