Brake Master Cylinder
Discussion
Has anyone changed their brake master cylinder from the Cortina one to the larger Jag one? If so is it a good improvement? Mine is knackered and i'm just investing in some 330 discs with AP 4 pots and thought the bigger cylinder would help out. Bore is up from 20.8mm to 23.6mm.
Cheers,
Mick
Cheers,
Mick
It is almost essential otherwise you will get excessive pedal travel but.... you need to be prepared to make up some additional pipework as the connections are not the same. The reservoir is also a bit of a swine as well because the angles are not ideal so that the amount of fluid is borderline or liable to spill.
The 520 went this route some time ago (not with a jag unit) but with a custom set up. Also fitted an adjustable brake bias (again highly recommended) and residual pressure valves to prevent front pad knockout that you will almost certainly experience with bigger discs. The front bearing moves slightly and this can knock the pads back a little so the pedal goes to the floor when pressed the first time. A bit disconcerting when approaching Paddock bend at Lydden at 100+ mph.
With 330 mm discs I take it you are not running standard 15 or 16 inch wheels?
The 520 went this route some time ago (not with a jag unit) but with a custom set up. Also fitted an adjustable brake bias (again highly recommended) and residual pressure valves to prevent front pad knockout that you will almost certainly experience with bigger discs. The front bearing moves slightly and this can knock the pads back a little so the pedal goes to the floor when pressed the first time. A bit disconcerting when approaching Paddock bend at Lydden at 100+ mph.
With 330 mm discs I take it you are not running standard 15 or 16 inch wheels?
Hi Steve,
I'm running Borbet 17" rims, which have 385mm clear inside the wheel, hence the 330 discs. Thanks for the advice about the discs knocking the pads back, is this going to be a big reality on the road?
In your experience was the Jag master cyl a good improvement over the standard one or is there a cheaper/easier/better alternative?
Cheers,
Mick
I'm running Borbet 17" rims, which have 385mm clear inside the wheel, hence the 330 discs. Thanks for the advice about the discs knocking the pads back, is this going to be a big reality on the road?
In your experience was the Jag master cyl a good improvement over the standard one or is there a cheaper/easier/better alternative?
Cheers,
Mick
Steve,
This front pad knock-out could occur on 300mm disks as well I assume.
Could you explain the solution you have, because I think I experience slight pad knock-out (peddle not to the floor, but a bit deeper - say half way -)first time. Tend to 'test' the brakes before the actual braking for the corner to have full feel during braking.
I thought it could be the mounting of the discs (hub surface not perfect, although I tried).
Rob (350i, 300mm in the standard 15" with 4-pot callipers)
This front pad knock-out could occur on 300mm disks as well I assume.
Could you explain the solution you have, because I think I experience slight pad knock-out (peddle not to the floor, but a bit deeper - say half way -)first time. Tend to 'test' the brakes before the actual braking for the corner to have full feel during braking.
I thought it could be the mounting of the discs (hub surface not perfect, although I tried).
Rob (350i, 300mm in the standard 15" with 4-pot callipers)
I have experienced it most on the track and it is extremely interesting because you have no idea if the brakes have failed or what. It has happened a couple of times on the road but the pressure valves have sorted the problem.
The residual pressure valves keep 2 lb of pressure in the front brake system to keep the pistons in contact. Cost about £30 each. I use Wilwood ones and a Wilwood brake pressure adjuster for the back. Don't use the ones intended for drum brakes.
I know how to spend £600 on a custom brake pedal system if that is any help. The jag ones are an improvement but are expensive to buy, have a reservoir system that is far from ideal for the wedge because of the angles and its size so I am not sure I would recommend them. The 520 uses a modified Rover SD1 unit. The pipework had to be reroted and replaced because the holes don't match in size, location or number. It is not a drop in replacement.
Personally I think a 330 is a bit too big as the brake balance will move heavily to the front and the rear brakes cannot be upgraded to help restore the balance. They can but you could buy a second wedge for the cost...
As for performance... the 520 is now braking at 1.3G on slicks.
The residual pressure valves keep 2 lb of pressure in the front brake system to keep the pistons in contact. Cost about £30 each. I use Wilwood ones and a Wilwood brake pressure adjuster for the back. Don't use the ones intended for drum brakes.
I know how to spend £600 on a custom brake pedal system if that is any help. The jag ones are an improvement but are expensive to buy, have a reservoir system that is far from ideal for the wedge because of the angles and its size so I am not sure I would recommend them. The 520 uses a modified Rover SD1 unit. The pipework had to be reroted and replaced because the holes don't match in size, location or number. It is not a drop in replacement.
Personally I think a 330 is a bit too big as the brake balance will move heavily to the front and the rear brakes cannot be upgraded to help restore the balance. They can but you could buy a second wedge for the cost...
As for performance... the 520 is now braking at 1.3G on slicks.
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