Bus master cylinder conversion

[albert]

hi,ray,, very long and good tech.information, yes you have reason for the rebuilt kit,, in many rebuilt shop they sale the scrap,, but my oppignion is if we can find brand new from ,,fag,or ate ,, we do the job for long term ,and for me i vote for a new master ( brake or cluth ,, ) and i thing some brand new parts from mercedez can make a good job on the 412 if we can adap this part ,, if you look in importparts (message before ) they sale for merc.73 new cluth master cylinder ,with the same 412 look ,,i d,t know if he can fit on the 412 but by the picture he look appx. the same ,,we never know if we d,t have that in the hand , and they are expensive 120.$ but if he doo the good job , forget the price , we have the best ,,and in my hand i have for spare parts ,, brake master cylinder ,from ,,napa,,pn,,39060,, it was buy by the first horner of my car and pay 150.$ in 2003 and garatie for life time ( ??? life time ,???years is life time ) it was made by ,,ate,,no.79 new ,, not rebuilt or if it is rebuilt it is made with quality i d,t can see any scrath on the frame ,, for me i thing we can find the cluth master too ,in new ,,but were ,, good question ,look in my first message for this merc. pn.000-295-77-06 ,, master cluth cylinder for merc.73 ,,albert

[albert]

oh ray i have one question,,do you know if the piston for the master cylinder brake with the booster is the same or différent with the standar or ( non power brake ) thanks for the info..albert

[vwbill]

www.Partsamerica.com shows the same clutch master for the mercedes and the vw412 $104 part # 0720060

http://www.partsamerica.com/ProductDeta ... er=0720060

Napaonline shows a rebuild brake master for the vw412 as TS 111648

http://www.napaonline.com/masterpages/N ... 0-%20Remfd

p.s.What is the best material for the cylinders of the Hydralics? Stainless steel, steel, aluminum? Can a cylinder be resleeved? bill

[albert]

hi, bill, you are very good ,, my first suggestion for merc. was not too bad ,, if partsamérica show the same ,,pn,,for the 412 too,,wow ,, you are a good ,,colombo,, and i look in your napa ,, yes for what they show ,this pn, is rebuilt ,, they d,t geeve the pressure swith ,, plus i look the end cap and it is différent on my new ,,master,, but this info.. help many guy ,,

[albert]

oh, bill for your ,,ps,,, for sure the stan.steel,, is very rust proof ,, allum, is very soft and not rust proof,, ( the rust on the all, is différent but there too ) the pore of allu, can be destroy by the brake oil ,, that need spécial oil ,,but for me, my oppignion is if we have very good quality of the steel , it is betther of the rest ,,but in the brake systhem , many piston are in stanles steell and the core is with only the steell,, wy?? the price ,, ???who know,,

[albert]

you see bill , in my dailay job,, i work with différent kind of matérial ,, allu, stanles,, cup,and steell,, and , to the end the steell keep the time ,, the problem with the stanlens,, we never know the% of the carbone in the construction of the stanles,, and with the chimic product that geeve bizard réaction ,, samething with the cup,,,and allum.,, chimic réaction,,i am not spécialist in the chimic réaction but i know that exist,,

[SureFit Travis]

To follow up with the re-sleeving discussion, wouldn't a brass sleeve be a better option?

By the way, this is good info guys. Thanks.


Travis

[vwbill]

Hey Guys, I ordered a Napa reman brake master cylinder so if or when I get it I will open it up and take pics of the parts and try to get a pic of the inside or describe what I find! I just wonder if you could find a sleeve tubing to put in a old master core and if you could hone it to spec.? Brass does sound good for the cutting but I have no idea of chemically and hydralics! bill

[Wally]

The Napa reman. cylinder doesn't show a price. That makes me suspicious. We have had so many 'wild geese hunts' with brake master cylinders... It never showed or the wrong part showed IIRC. You sure they could deliver when you ordered it?

[vwbill]

Hey Wally, I think that is just a link issue for price and entering the vehicle will refresh a price. It was 43.73 with shipping! Don't know if the sale will be completed like you said but I have a order number! Bill

[albert]

oh,bill to this price , the remain job ,is not a quality job,i thing,,, for my sécurity , remaining the cluth master ,slave or galipper is correct but the brake master ,i prefair the new ,,or remain from fag or ate samething ray said befor

[raygreenwood]

Albert...VWbill....thanks for the very good info.
Wally...nice term and is very descriptive. I too have suspicions when I see things like....no price. No manufacturer list (ATE, FAG, Wagner, etc).
I have been on many, many "wild geese" hunts for master cylinders....and ball joints.
Many of the parts manuals from the big conglomerate warehouses are written by people who are just translating collections of parts manuals and part # lists....not automotive experts.
To this day...I still find parts books that list brake master cylinders to fit types 1,2,3,4...under one collection of part #'s based around years...(wtf?). And...I still find parts books listing type 3/4 ball joints as one #(?).....and upper and lower ball joints for type 4 (?).

Also a great many of the parts sites with search engines...hundred have popped up....seem to show parts for every make and model. Some have all correct photos (an acheivement in its own right)....but suspiciously never seem to have all that much in stock. Many of these universal parts sites are simply licensed clearing houses....all pulling from the same warehouse network.

The pistons for powerbrake versions and manual versions...are totally different.
The four things that are MUST haves...when swapping pistons from cylinder to cylinder:
(1) Stroke length of each circuit must be identical
(2) piston diameter of course
(3) The tail stop pin for the bottom of the bore on the secondary circuit piston and the depth of the bore for the pushrod in the primary piston must be identical
(4) Most critical...the distance between each "flange" or piston heads on both pistons, and the thickness of each piston head, the volume between each piston head and the diameter of the compensation port holes on each piston head....MUST be identical. You will need a caliper to compare this.
The reason for this last item...is the most important. In each make of cylinder casting (FAG, ATE etc).....the ports...where the fluid enters from the reservoir are in different locations by very small amounts .
This means....that the small holes you see in those ports under the rubber grommet (there are two...a larger feed and a very small relief hole)......are in different locations ...in relation to the pistons in the bore. In some cases....the use of the wrong pistons will block the relief ports....causing fluid not to replenish and in some cases cause the brakes no not "rebound" after you put your foot on the pedal so they lock. Ray

[Bill K.]

Bill K has the correct cylinder in his pictures. My brain is slipping. Could have sworn it was 21mm. That is the correct cylinder though (the one in the top picture). You could use either, but if you use the one with twin seconadry circuit ports...you would plug one to remain with a single brake line to the rear. Ray

After reading these two articles from PelicanParts.com, I'm leaning toward converting to the 19mm 914-6 master cylinder as the -6 had 48mm front pistons and 38mm rear pistons just like I'm planning. Using the 22mm bus master cylinder with 48/38mm calipers will result in lower brake forces than stock 412 (42mm fronts). With the 19mm m/c, the front brake pad force will increase over stock while minimizing increased pedal travel caused by the larger 48mm pistons. The rotor diameter and pad area changes appear to be minimal.

http://www.pelicanparts.com/techarticle ... _calc2.htm
http://www.pelicanparts.com/techarticle ... lipers.htm

Make sense?

Bill

[raygreenwood]

Bill....no....that article is a bit incomplete. They do not take into account that the 411/412 had (stock) about the same diameter and stroke as the 914-6. That would be a 19mm cylinder (not a 17 like the 914-4). So teh 411/412 cylinder is about equal to the 914-6 .
Now......using the stock 42mm pistons, the 22mm bus cylinder is a huge improvement in volume over the stock 19mm or the 914-6.
Going to 48's....not only do you not require the same amount of pressure due to the larger piston surface area and the larger pad area (as mentioned in the article)...which together create a lot more friction and clamping pressure than the smaller piston diameter caliper.......they are also not taking into account.....that volume = pressure.

Bear with me now. This is NOT a 914 we are talking about. The pedal cluster arrangment is totall different. First, the ratio of the pedal fulcrum is higher in a 411/412 due to the way it is mounted. You will generate more leverage with the same 20 pounds of driver foot force in the 411/412 than the 914.
Also...and this is not poking at who wrote that article....but 20 pounds of driver foot force is nothing. In reality its about double. It also depends....as I noted ...at what angle your foot must be in order to drive the pedal. The 914 pedal...is mounted opposite of the 411/412.

In reality....it is not a lot more volume requirement to drive a 48mm cylinder the same distance as a 42mm.
Since liquids cannot compress (much)....that extra volume from the larger cylinder will QUICKLY generate much higher pressures not shown in further calculations in that arcticle.

For example. If we are still just talking about those three cylinders in a 914....at only 20 psi of foot force...then the article is correct.

What their formulas do not...and cannot show......is that once the pads are in contact with the rotor......and the fluid is "locked up"......and no more volume can escape either cylinder (because there is no more real distance available to move the caliper pistons....only pressure gain through compression can occour).

So in reality...it may require 20 foot pounds to move the volume of fluid needed to move the pistons into contact with the pads...to generate the numbers stated........but.....after that.........even 1 foot pound of pedal pressure in the higher volume cylinder ....will create an exponentially higher level of pressure at the caliper piston ...because there is no more room for movement.....only pressure rise.
Get it?

Also...bear in mind this. When you install a bus master cylinder in a 411/412....you are going to have o build the fulcrum linkage and pushrod yourself.

Since you will be converting from a rearward facing cylinder (stock 411/412) to a forward facing cylinder (bus conversion)..... you have to build the exchange fulcrum.
In the stock 411/412 master cylinder.....for the sake of discussion....lets call it a 1:1 ratio of pedal movement to piston stroke even though it is actually a higher ratio of pedal movement to piston movement ratio...........which results in more pressure generated on the piston and fluid....than you put on the pedal......because of leverage. But for a "benchmark" in this discussion we will call the stock ratio ....1:1.

When you install the bus msater cylinder....or for that matter any trunk mounted master cylinder in the 411/412....you can adjust the pedal to piston ratio...to almost anything you want. This is because there has to be a pivot.....to convert rearward movement of the stock pedal pushrod...to forward movement for the new trunk mounted cylinder.
This pivot can be either bar stock or a steel disc with an axle put through the middle.. The pushrod from the pedal might mount....say 50mm from the center axle.....which is larger than stock....increasing the leverage pressure per pound of pedal pressure exerted..........and the piston pushrod might mount at say 75mm from the center pivot.....giving a ratio of 1:1.5 pedal to piston movement.
It will take much less mm of pedal travel to create pressure. In other words..you will have a much shorter pedal stroke if you want it. And...because of the higher leverage ratio....20 pounds of pedal pressure can easily create....40 pounds of pressure or more at the piston.

Sorry for the length.....but is this clear? Ray

[Bill K.]

Thanks for clarification Ray. I was thinking 412 m/c was 17mm... I see how the fulcrum linkage will act as a "booster".

Did you mount yours in the firewall recess above or below the trunk spring bar? Mounting in the top recess appears to require a direct mount reservoir as the 412 reservoir is at the same height. What reservoir did you use?