350I Brake Upgrade

[ouiseyg]

Ive just fitted the 2.8 Grany vented front discs and larger calipers and pads to my 87 350. The question I have is is the same master cylinder used on say a 400se with these brakes as standard as I seem to be experiancing more pedal travel. Or do I need to adjust the pedal up with the adjustment screw between the servo and master cylinder as the cylinder is now moving more fluid. Or do I still have s**t loads of air in the system still, because I didnt lose the head of fluid in the resevoir Ive only bled the front calipers!!!!

[adam quantrill]

You can tell if there's air in - try the pedal without the engine running, it should go rock hard.

[leorest]

ouiseyg
As I am sure you know already, the pedal will start off soft and pump up hard, if there is air in the system.

I think, your symptoms match what would be expected to happen if the total (caliper) piston area was increased. What calipers did you fit? maybe someone here has upgraded to the same calipers and can advise?
Leo

[ouiseyg]

The brake pedal is good and hard with the engine off but as soon as you start the engine it travels a lot further than before. The brakes work ok but its just a little un-nerving when youve been used to the pedal position for some time. It makes sense that with more fluid being moved to operate the larger caliper the master cylinder will lose some of its pressure and have to travel further. Or am I being silly!!!!

[djc1001]

ouiseyg said:

The brake pedal is good and hard with the engine off but as soon as you start the engine it travels a lot further than before. The brakes work ok but its just a little un-nerving when youve been used to the pedal position for some time. It makes sense that with more fluid being moved to operate the larger caliper the master cylinder will lose some of its pressure and have to travel further. Or am I being silly!!!!

Pressure will remain the same but extra piston area at the caliper needs more fluid therefore more pedal travel.
You might recover some pedal travel via the adjuster behind the brake booter.
One of the tests to check the brake booster is working is that you should feel the pedal go down a little when the engine is started.

>> Edited by djc1001 on Tuesday 19th July 09:22

[350matt]

As an aside to this has anyone tried increasing the pedal ratio on a wedge? In order to reduce the effort to stop, I know it'll increase the pedal travel, but I know the donor vehicle brakes ( Ford Mk II Granny) were quite reasonable as I used to have one. So its either down to a smaller bore master ( which might run out of fluid displacement - Bad thing) or increasing the leverage, I'll make some measurements, I vaguely remember that the ideal ratio should be in the region of 7:1

Waddya think?

Matt

[ouiseyg]

I will endeavour to take some of the travel out by adjusting the pushrod between the brake master cylinder and the servo tonight. Last time I did this it gave a superb pedal, I drove 5 miles fine! then the brakes started binding (first time I'd taken the Missus out! GREAT). A bit at a time ME THINKS !!

[badredwedge]

Fitted the same upgrade to my 350, Grany estate vented disks and larger calipers. also added braided hoses. had a small problem getting the air out and I did adj the travel slightly.
Also it took a few hundred miles to bed in the new set up but now the brakes are GREAT!! Need some green stuff pads now to keep me new wheels clean.
Keep at it, it is worth it

[ouiseyg]

Took a little while but just to wrap this one up. After fitting the larger brakes I had to do the adjustment bit between the servo and master cylinder to take out some of the peddle movement. After that the brakes worked but I would lose pedal pressure every now and again like air in the system!! Bled them again but still the same, so I purchased a Gunson Easy Bleed kit that pressurises the system from the top with air pressure from your wheel(use about 15psi or the cap will not seal). First thing I noticed was the kits fluid container was emptied by half even before Id bled a caliper.Cracked a bleed nipple and got a chunk of air out as well. The test drive went well with a pedal with a lot more feel and brakes that once bedded in will give some confidence compared with the brick on a piece of string that it was before. At this moment in time worth doing if not a bit of a faf bleeding the bleedin system!!!!

[islander]

Have you been able to bleed the back ones yet?

The pit is generally available on the basis of the supply of the calipers and discs! and may be some help with the final adjustments!

See you soon.

[ouiseyg]

No probs. Already have discs give us a call...
Fingers crossed backs wont need bleeding. YET!!