bigger master cylinder?

[MattKab]

....And Goodridge braided flexi-hoses are awesome! Forever guaranteed too.

If you're still running rubber hoses, grip them firmly, with both hands and get a buddy to pulse the brake pedal. You'll soon discover wasted fluid displacement and how much potential energy is winding up in the rubber.

The addition of these flexi-lines returned the stock feel to the brakes on my Bug. I wouldn't even risk trying the split bore m/c on my car.

MattKab over and out

[kdanie]

Matkab, I read a magazine article recently about brakes, I can't remember which mag. and can't find it back. It stated that the pivot point for the master cylinder rod on the brake pedal should never go past 90 deg. over center or you will loose the mechanical advantage and pressure will drop. This information came from an aftermarket brake company (willwood, I think). Something to keep in mind when setting up your system.
I have a good book on performance brakes with a formula to take the guess work out of selecting a MC. I will try and remember to dig it out tonight.
ken

[Steve C]

Hi

Our registration people the Roads & Trafiic Authority will not allow braided lines to be fitted on street cars. They have a problem if used in dirty or dusty conditions, the dust will get in between the braid and the tube an the braid will wear awy the tubing. I took my braided hoses off because my car needs to be inspected by the RTA soon to cover mods I hace already done, I didn't really feel any difference, but I changes other things at the same time.

Steve C

[MdR]

Our MOT doesn't allow braided hoses either, but I ran my 914/4 with them without it failing the test.

[MattKab]

I had no idea they're not MOT approved. It didn't say so on the box and BBT didn't say anything. I'll look this week and quote what the MOT Inspectorate guidlines say. Thanks for raising the point! I'll find out where we all (UK) stand.

I may try sealing mine with some clear silicon. Interesting comment about the ingress of dirt causing wear under the braid.

[ricola]

For road use, I read a really nat trick for braided brake hoses.
Buy some clear heatshrink tubing from somewhere like RS, or even colour coded to your brakes! This will stop grit getting trapped in the weave and abrading the rubber core.

Rich

[ricola]

I was having a nose around my local VW breakers yard yesterday and had a look at a Bay window master cylinder. It looks like it is 20mm bore for both circuits which could prove ideal for my early 944 set-up. Just a bit more fluid than stock but should give a nice feel.

Has anyone tried this before? It looks like it will fit OK, there is a brake switch on it. The onlt difference will be that there is only one output for each circuit so a T piece will have to be used for the front circuit...

I have also been told that later model VW/Audis have compatible m/c s of bigger diameter: 20.65 and 21.65 mm

Rich

[kdanie]

I finally got a chance to dig out my brake book (burried under a pile of my wifes junk in the garage!). The book is HP books "Brake Handbook" by Fred Puhn. Selecting a M/C is not all that easy, chapter 9 is filled with math equations to figure everyting from center of gravity or your car, kinetic energy at speed, brake torque, maximum pressure to get max deceleration and finally M/C size to achieve the correct pressure.

Every one of our cars are different, weight, C/G, tire friction, caliper piston size/number. I recomend the book, it is filled with good tech info and will certainly broaden your knowlege and understanding of high performance brake systems.

I think the best bet for most of us is an accurate article in the tech section covering what people have used that works. If forum members want to email me a discription of what they are using, M/C size/application and caliper type/application and any other info on your brake system, such as how the pedal feel/travel is, I will sift through the info and write a tech article for the website so all the info is in one place.

ken