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-   -   Tom classics disc brake conversation (http://squarebirds.org/vbulletin/showthread.php?t=20601)

booalou 06-11-2016 05:20 PM

Tom classics disc brake conversation
 
Looking for everyone thoughts.

I bought and installed the tom classics disc brake retrofit kit from eBay. After the installation was completed I've tried to bleed this system and have not been able to get anything but a spongy pedal. Now I've put at least 180oz of fluid through the system bleeding and have started over from bench bleeding the MC more then once. Have bread it with the two men manually bleed and a one man vacuum bleed with no luck same results. I've sent an email to tom classics asking for a new MC since I can't find any other problems.

Note I've added a residual pressure valve for the rear brakes and use a prop valve bleeder tool. Still nothing but a sponge.

Help

simplyconnected 06-12-2016 10:48 AM

Air in the system is not the only cause for a spongy pedal but it is a major cause.

Go over the train of hardware from your brake pedal to your master. If any of the steel components flex, it will feel like a spongy pedal.

The idea is like standing in a bucket and lifting yourself up by the bail wire. Your brake pedal pivots from the brake pedal support. The brake pedal support has firewall bolts that continue through to the booster/firewall bracket. This 'sandwich' needs to be tight and all four bolts need to be there. From the bracket to the booster, same story. Get someone to mash the brake pedal hard and repeatedly while you inspect. If anything moves, even slightly, fix it. The hydraulics are an extension of this mechanical train. Since brake fluid cannot compress, the only other culprit can be air, anywhere in your system.

The residual valve is ok but I prefer to use self adjusters on my rear shoes. I stay out of deep water so the adjusting ratchet (star wheel) doesn't rust.

The residual valve keeps the shoes spread out so the pedal remains up. Eventually after the shoes wear, a pistons will pop out of a cylinder. In that scenario, your pedal won't go down but your fluid level will.

Self adjusters spread the bottom of the shoes to keep them close to the drums but the cylinders always return home. The pedal will not go down and the fluid level will remain full. More importantly, the brakes will squeal before a wheel cylinder piston gets close to coming out.

If you're happy with the residual valve, it is important you stay on top of your brake adjustment schedule. Again, you will not get a warning if the shoes are too far out. Ford Tempo cars had this problem. Thousands of them were towed into dealerships with a rear wheel dripping with brake fluid long after warranty expired. - Dave

booalou 06-12-2016 02:32 PM

Flexing
 
I will check it out to make sure nothing is moving

simplyconnected 06-12-2016 04:06 PM

At the factory, we vacuum bleed. If the system doesn't hold a vacuum, we won't fill. This holds true for the radiator, A/C, etc. Vacuum filling is the grand daddy. There is no such thing as empty pockets or trapped air.

I forgot to mention, the brake pedal support is bolted to your dash AND your firewall. There is no way the firewall will flex when you mash the pedal hard. Loose or missing bolts will make the firewall bracket & booster flex because you're trying to push the booster out the other end.

A good bench bleed is really all you need. What method are you using? I screw two old brake lines into the side ports and bend the open ends back into the reservoirs below the fluid level. At first, use short strokes. After ~20 pumps on a level surface the air should stop. There is no reason to go through more than a cup of fluid. The transparent plastic 'bleed kit' works too.

When shoes and pads are not bedded-in, they tend to feel odd or maybe a bit spongy. Give it a few weeks and your system will get better. Apply the brakes as you would normally during this period. You won't notice the slow change until you need to stop fast.

Think about it, shoes are a different arc than the drums and pads don't wear flat. Old pads are normally worn on a slight angle, even though they still work well. Every component is always slightly different.

I would like to see a few pictures of your setup. - Dave

Yadkin 06-12-2016 05:08 PM

Tom has a quality control issue that may be affecting this. The calipers are from an S10 and have to be machined at two locations to clear his custom bracket. Make sure that the piston is able to make full contact against the rotor. Inadequate clearance can cause a problem in this area.

booalou 06-12-2016 09:02 PM

No pedal when the car is started
 
I have bench bleed the master cylinder several times with and without brake lines leading back into the wells. Today I removed the brake line and plug the mc while on the car. Had my son exercise the brake pedal so I could make sure we didn't have anymore air in the system. i didn't see a thing so I put the cover back on and checked with the mc isolated we have great pedal that holds.

Once I put the prop valve back in the system and bleed again I have the same spongy pedal and even worse when I start the car I have no pedal at all so I can't drive it like this.

I will post pictures of my set up

booalou 06-12-2016 09:06 PM

Pics
 
I can't figure out how to post my pics on here

booalou 06-12-2016 10:01 PM

Dave I sent you a private message

simplyconnected 06-13-2016 10:27 AM

Bob, I've seen videos of that 'blocked port' type of bleeding but I prefer using the 'recirculating tubes' type of bleeding because it has never failed me yet.

I have to ask a few questions because I have to believe the reason you kept adding more fluid was because the bubbles didn't stop coming...
  • Was your M/C 'running clear' when you installed it or was it still showing bubbles?
  • Your whole system only holds about a cup of brake fluid. Were you showing bubbles at every bleed valve?
  • Did you change your steel lines?
  • Did you change your hoses and are all connections right? (Notice I didn't ask if they are tight because a bad fitting or cross-threaded nut can still be tight, but leak.)

If you still aren't getting anywhere, call me (248) 544-8834. - Dave

GeoffInCarlsbad 06-22-2016 11:11 AM

I am going for it
 
Hi Folks:

I am going for it, and getting ready to order a front disc conversion kit from Tom's (eBay) store.

Here's the one line in his description I have a question about:

"You will have to make new brake lines to make this booster assembly work"

Who has done this work to "make new brake lines"? What can i expect? I have not worked with steel lines yet, so I need some education....any help?

Regards,

~g


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