Help: Front Brakes

[Dean Roberts]

Have you put in new fluid, different viscosity.?

 

Flushed system and used identical fluid and previous setup.

[Dean Roberts]

The fact both discs lock up completely after a short distance makes me think same as Steve and Florin. At the master cylinder or bias bar.

 

As when the brakes were done everything ran freely, now even after cooled down are tight to move and will easily overheat.

[steve in stockport]

Isn't there a specific procedure to bleed bias brakes, ie slacken bleed one side, slacken bleed other side then set the bias? Might be talking rubbish though.

[Dean Roberts]

New bigger discs, new bigger calipers, new bigger pads fitted. Dave fitted new braided hoses, new cylinders, new reservoirs and pedal box with bias.

 

Original setup worked but didn't stop car. New setup when brakes pressed work better when cold. But when overheating nose dips, both front wheels lock up to the extent rear wheels spin and fronts lock up leaving 2 nice black lines in the road.

 

In fact if this how good the brakes are supposed to be when you press them hard, then they are very good and the car won't budge.

 

Is heat causing the fluid to expand and because I have braiddd lines it's got no where to go except push out the new pistons?

 

Being both lock up at same time logic makes me think the same as you guys faulty master cylinder, but it's newish?

Or just the push rod not returning correctly due to bias bar?

 

Emptied brake fluid, removed wheels, calipers, discs, master cylinder and now checking everything Methodically and testing each part.

[Dean Roberts]

Isn't there a specific procedure to bleed bias brakes, ie slacken bleed one side, slacken bleed other side then set the bias? Might be talking rubbish though.

I will have a look around. Under the impression the bias is set up after bleeding system. I do remember you need to bleed servo brakes furthest first. Not sure about bias systems? Edited April 29, 2017 by Dino

[Bob Tucker]

I'm with 2 Bobs.......Ive had identical symptoms twice.

both times i had carpet wedged under the floor mounted pedal that stopped

the push rod coming right back.

i dont know how the twin cylinder has been set up but however, there MUST be free play in the rod.

when you push the pedal by hand, can you feel it take up some slack?

[steve in stockport]

Just found a PDF by AP Racing but can copy it into here.

It says with bias/balance bar systems that a front and a rear wheel should be bled simultaneously so that both cylinders stroke equally to avoid overloading one side of the balance bar.

So a three man job, one on pedal and one on the front wheel and one on the back.

Google bleeding brakes with balance bar for the full PDF and it's on page 5 of 6

[Dean Roberts]

Just found a PDF by AP Racing but can copy it into here.

It says with bias/balance bar systems that a front and a rear wheel should be bled simultaneously so that both cylinders stroke equally to avoid overloading one side of the balance bar.

So a three man job, one on pedal and one on the front wheel and one on the back.

Google bleeding brakes with balance bar for the full PDF and it's on page 5 of 6

 

Ha, ha , ha......

 

Me & Nikki have just discussed this over dinner whilst reading the Tilton bias braking bleeding document.

 

Time to start putting everything back together and look at bleeding the system in the morning b4 attempting a trip to Stoneleigh again....

 

Thanks everyone, time to go to work and will keep u posted on the outcome. Fingers crossed!

[Nicola Roberts]

How to party on a Sat night. Reading about to bleed brakes !!!! ( she will make it to Stoneleigh )

[raeautos]

Is the brake pedal free on the spindle?

I had mine tighten up once due to heat expanding every thing.

[Dean Roberts]

Ok after stripping down front brakes, flushing whole system front and back. Put everything back as piping, discs, calipers are functioning as intended.

 

I then removed braided pope from master cylinder and got Nikki to pump it hard (oooorrrr mrs)

Noticed every time pedal depressed very little fluid moved they the cylinder and the pedal didn't return correctly.

 

So reset bias bar to free, neutral position, reconnected everything and commenced with operation bleed everything. Bottles set up on front and back filled up reservoirs and got Nikki to gently and slowly push and pull until satisfied and no air was left in the system. Then repeated the same process again on opposite side front and back.

 

Plenty of air removed and finally Nikki was satisfied with the firmness.

 

Just taken it for a spin and it seems good and the brakes are warm ( not hot) as expected.

 

Only thing do do now is take it to Stoneleigh and setup bias bar at a later date.

 

So looks like bias bar, master cylinder and air still trapped in the system are the culprits. Proof will be when I attempt a drive to the show.

 

Wish me luck.

[Dean Roberts]

Cheers guys for the last minute support.

Edited April 30, 2017 by Dino

[Guest lotusPaul]

Not sure air in system is causing the locking, sounds more like the hydraulics sticking in the on position and not retracting. I would suggest its the bias bar. Be nice to see some pics tho.

[Guest lotusPaul]

Dino,

Just a quick question and not related to the problem but after your big disk conversion what size wheels are you using? And im guessing you stop in a cars length too.

[Dean Roberts]

16" fronts, 17" backs. Car stops much better now (like a normal car) and since the crash course on bleeding bias systems (front & back) at the same time and fixing the master cylinder (which wasn't returning to its correct position). I'm a lot more confident driving it.

 

In fact it flew to Stoneleigh and returned in the moonlit hours. Sunny open top trip there and trial by fire (night driving in the rain with covers on and new braking system returning home).

 

I will attempt to stick some pictures up of this setup and of the kit car show when I get chance.

 

Also had other issues I had to contend with 3 days before show....

 

Dead battery due due to electrical drain.

Fitted cutout switch and battery to bypass slow drain over SORN period.

Fuel leak from injectors, replacing custom o-rings instead of using standard (expensive Jags ones).

 

Next on the agenda get some mileage on the Kit and look at the backfiring when decelerating (spark plugs hopefully???)

Setup bias- bar for a more 60-40 ratio on fronts.

Replace leaking ball joint ready for MOT.

Edited May 1, 2017 by Dino