early 944 brakes, stock MC....dosent feel right

[speedy]

Jeza, when i did the calculations i did them converting everything into lbpsi, i read that artical earlier, it is what got me thinking , if you aplly the theory that 100lb from the driver is absolute pressure , this translates into 155psi from the front piston because the piston is less than 1inch squared in area and exerts more pressure because the input pressure is not in psi ,therefore the rear piston because it is less area but pressure is now applied as hydraulic pressure in psi ,it is dependent on the reduction ratioo of the the area,s 444 and 228 which is 1.9 so 79lb of pressure is aplied to the rear circuit ,say we had two pistons on the calipers that were 23mm front and rear the resultant pressure at the front piston would be 23-23 which isa 1-1 ratio so 155lbpsi or 100lb the rear would be 19-23 19mm area=228mm, 23mm area =444mm in area gives a ratio of 1.93 -1 multiply this buy 79 and the answer is 155lb or 100lb absolute it may sound sound confusing but if hydralic pressure is dependant on area then the ratio theory must hold true weather going up or down i put all sorts of caliper piston numbers in and the answers the same, connect the calipers front or back and apart from different pedal pressure it does not matter
what do you think

[Sunroof53]

I have been reading this with much interest as i am converting my 66 bug to early 944 na brakes all round. I have done all the mods and machining etc .So to clarify before i do this :1.Swapping the front connections with the rear will make no difference with the 23/19 MC.2.you must use the 23/19 MC if using NA brakes all round.3.No solution for bias issues as it depends on tyres/weight etc.I still have not read any reviews about peoples experiences which i find strange as so many people are doing it .I am looking forward to fitting the brakes but hope all this work will be worth it .

[Sunroof53]

I have been reading this with much interest as i am converting my 66 bug to early 944 na brakes all round. I have done all the mods and machining etc .So to clarify before i do this :1.Swapping the front connections with the rear will make no difference with the 23/19 MC.2.you must use the 23/19 MC if using NA brakes all round.3.No solution for bias issues as it depends on tyres/weight etc.I still have not read any reviews about peoples experiences which i find strange as so many people are doing it .I am looking forward to fitting the brakes but hope all this work will be worth it .

[Eliasson]

Hello
I m about to fill my brake system with brake fluid and start testing how the braking system is performing.
Whats important for me is two questions.
1. I dont want the M/C to bottom.
2. The rear brakes should never lock before the front ones.

The first ones is quite simple to calculate, if you know how much the pistons retard in the calipers, the amount of oil to puch them back should decide wath to use. And then I use some safty factor. I have 944 T calipers front and rear and I decided to use the original beetle M/C to start with.

The second question is more difficult. Every car on this forum is unique in some way. Ride hight, tire size, spring stiffnes, weight...... So my conclusion is what is right for one car is not right for every car. There could only be guidlines where to start testing.
If you continue the calculationes and find out how much possible braking torque that is produceed at brakedisc. If I have made the calculations right the 944 have a bit more braking torque at the font/rear (55/45%), 911 have around (60/40%) front/rear. That is what the manufacturers decide for thier modells, it could be some kind of guidline to follow?
Then its up to myself to set up the car so the maximum of force could be used for stopping my car. Inceasing or decreasing front and rear bias. Speedy and Super VW have mention some ways to do that in this tread. super vw for example put some weight in the front and then he increased the rear bias.

Anders

[speedy]

putting more weight in the front does increase rear bias by default, this is a good solution to improve beetle braking by shifting a little weight over the front wheels improves grip therefore increasing the braking torque that can be applied ,many people place batterys in the front to accomplish this without adding weight to the car .
A bias valve will only work if the car is rear biased to start with !
Like you said each car is individual , wether you have a spoiler on the front or back, oilcooler up front , tyre size ratio and compound full tank of fuel etc
I think it is down to trial and error to get the balance you are happy with .

[super vw]

I already have a Optina Dry cell battery up from (right hand side of car in the corner by the fuel tank and above the spare tire well).
I really should have added a heavy battery (60 lbs or so) to facilitate weight shift better. but then i would have had to give up cargo space.

This week i al going to raise the rear end of the car up about 1/2- 3/4 of an inch to give me some more weight transfer to the front. at the moment i have a perfectly level car with NO rake to speak of, adding a rake will help with the front a bit. I alreay have the front end up on the adjust- a struts max setting (about 1/2 inch fender gap in the front). and i have no fender gap in the rear.
I raised the front to tame down the bump steering issue i had when it was "dumped", much better.... but still the steering tierods are not PERFECTLY level at a settled rest (best for no bump steer).

Although this kind of fine tuning is not going to make the brakes pefect, but it helps to get the car bananced so the brakes can work as well as they can.

The only time i have bias issues is if im not doing controled HARD braking at SPEED (60+) such as autocross events and sudden emergency stops at lower speeds.... and thats related to weight transfer and not having optinum bias). although if i transfer the weight smoothly and with more time i can really bite hard and stop no probelms with very litle tendency to lock up (although it will lock the front still, and thats fine)

So really i should be looking for ways to make the rear brakes work better, thats with hydro, friction changes like pads or mechanical changes such as tires..ect

Ramble....

[1303R]

what i'd really like is anti lock brakes. has anyone fitted them on here? can't be that hard can it? i think some later 944's used it

[jrinlv]

Sorry I'm too lazy to go look at what you want to do with your car but most "pro" drivers hate anti lock brakes, they say it takes the control away from the driver, but for the street no problem. Just a thought, take care and good luck. JR