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Marvel
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PostPosted: Mon May 03, 2021 7:07 am    Post subject: Master Cylinder Diameter Reply with quote

The brake pedal travel on my early 65 Type 34 is halfway to the floor before the brakes come on. The fronts are drums with 22.2mm cylinders and rears are Beetle short axles so I assume 19.05mm cylinders. As the rears are smaller diameter than standard should I use a 17.46, 19.05 or 20.64mm master cylinder?
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Erik G
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PostPosted: Mon May 03, 2021 3:19 pm    Post subject: Re: Master Cylinder Diameter Reply with quote

there should be nothing wrong with the stock sized master. Have you adjusted your brakes at the wheel cylinders?
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PostPosted: Mon May 03, 2021 5:40 pm    Post subject: Re: Master Cylinder Diameter Reply with quote

Agree with Erik, the stock sized 19mm master cylinder in the Type 3 should give you a nice high pedal when all the brake shoes front and rear are adjusted correctly.

Naturally as the shoes wear the pedal travel will gradually increase until you adjust the brake shoes again.

I would think with smaller diameter wheel cylinders in the rear you should actually have less pedal travel than stock with a stock master cylinder, if I’m thinking about that relationship correctly (and I might not be since I just had a martini).

I would suspect either poor brake adjustment or air in the system somewhere.
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Marvel
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PostPosted: Mon May 03, 2021 10:33 pm    Post subject: Re: Master Cylinder Diameter Reply with quote

The brakes are adjusted so they are one click off rubbing and the system is bled. There is about 1mm clearance on the pushrod. I’m not entirely sure if it’s got an original master cylinder but as the pedal travel is so long I assume/hope it’s a 17mm. I’ve got a 19mm Beetle one coming. I think I need to drill the threaded holes clearance and extend the pushrod. Correct?
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Erik G
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PostPosted: Tue May 04, 2021 10:11 am    Post subject: Re: Master Cylinder Diameter Reply with quote

why not just use the correct part? or at least an upgraded dual circuit type 3 master?
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PostPosted: Tue May 04, 2021 11:15 am    Post subject: Re: Master Cylinder Diameter Reply with quote

Measure the distance between the pedal tip and the bulkhead at the point where you first take up the 1mm play in the pushrod.
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PostPosted: Tue May 04, 2021 3:26 pm    Post subject: Re: Master Cylinder Diameter Reply with quote

I believe according to the parts book all the Type 3 master cylinders (both single and dual circuit, drum and disc brake versions) were 19mm bore diameter.

The stock pedal ratio is about 6:1, so to verify your 1mm clearance where the pushrod hits the m/c piston, you should 5-7mm movement at the top of the pedal before you feel the pushrod contact the piston.

The master cylinder should have the bore size stamped or cast into the housing but I can’t guarantee it. The one I just took out (a Type 3 dual circuit disc brake m/c) did have the bore size (19mm) cast into the housing.

If you change the master cylinder, you may not have to do anything to the push rod. Install the m/c first and then see where your push rod clearance is. Then if you need to make an adjustment you can do so.

It’s generally preferable to make the adjustment using the pedal stop rather than changing the push rod if possible, and if the required adjustment is minor that’s the way to do it.

But if going with a different type of m/c you may be forced to adjust the push rod, but you won’t know til you get it in there.

Another factor to keep in mind when messing with this stuff is that the brake pedal, at rest, needs to be a certain minimum distance from the bulkhead to ensure that there is enough pedal travel to allow for braking if one of the hydraulic circuits fails. I think the spec is close to 8” but check the Bentley to be sure.

I think some of the Beetle master cylinders were 17mm as the Beetle front drums only had a single wheel cylinder each so it’s not impossible that over the years somebody put the wrong one in. I hope that’s all it is.
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Marvel
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PostPosted: Sat May 22, 2021 6:39 am    Post subject: Re: Master Cylinder Diameter Reply with quote

I've fitted a new 19.05mm diameter Beetle master cylinder and the pedal feel is much better. The previous one must have been a 17.46mm Beetle one as the pushrod was already the correct length. The car now pulls up in a straight line too. But, and there is always a but, it feels like the left front brake is being applied when turning left and something tugs the steering when hitting a bump in the left hand side. The wheel bearings are adjusted with approximately 1/8" movement at the rim. Any ideas? It's drums all round by the way.
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PostPosted: Sat May 22, 2021 11:40 am    Post subject: Re: Master Cylinder Diameter Reply with quote

Marvel wrote:
I've fitted a new 19.05mm diameter Beetle master cylinder and the pedal feel is much better. The previous one must have been a 17.46mm Beetle one as the pushrod was already the correct length. The car now pulls up in a straight line too. But, and there is always a but, it feels like the left front brake is being applied when turning left and something tugs the steering when hitting a bump in the left hand side. The wheel bearings are adjusted with approximately 1/8" movement at the rim. Any ideas? It's drums all round by the way.



Your wheel bearing adjustment sounds suspect...."1/8" movement at the rim"...rim of what?

Wheel bearings can be adjusted a couple of different ways....all slightly different but close enough.

The most common is to tighten the spindle nut while spinning the drum or rotor...until the tightness stops the rotation in about 1/2 rotation...then back off about 1/3 to 1/2 turn.

An alternate is a version of this but checking that the machined washer under the spindle nut can be shifted lightly with force from a screwdriver tip. Not ideal....but very similar to the first method in result.

Or....use a dial indicator in the hub center to measure deflection/play while using some variant from above.

Measuring 1/8" of play at the tire rim...means a lot of slack in the bearings. That will cause the drum to misalign in turns and drag the brake show...and will me an short life for the bearings.

Ray
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PostPosted: Sat May 22, 2021 4:04 pm    Post subject: Re: Master Cylinder Diameter Reply with quote

raygreenwood wrote:
Marvel wrote:
I've fitted a new 19.05mm diameter Beetle master cylinder and the pedal feel is much better. The previous one must have been a 17.46mm Beetle one as the pushrod was already the correct length. The car now pulls up in a straight line too. But, and there is always a but, it feels like the left front brake is being applied when turning left and something tugs the steering when hitting a bump in the left hand side. The wheel bearings are adjusted with approximately 1/8" movement at the rim. Any ideas? It's drums all round by the way.



Your wheel bearing adjustment sounds suspect...."1/8" movement at the rim"...rim of what?

Wheel bearings can be adjusted a couple of different ways....all slightly different but close enough.

The most common is to tighten the spindle nut while spinning the drum or rotor...until the tightness stops the rotation in about 1/2 rotation...then back off about 1/3 to 1/2 turn.

An alternate is a version of this but checking that the machined washer under the spindle nut can be shifted lightly with force from a screwdriver tip. Not ideal....but very similar to the first method in result.

Or....use a dial indicator in the hub center to measure deflection/play while using some variant from above.

Measuring 1/8" of play at the tire rim...means a lot of slack in the bearings. That will cause the drum to misalign in turns and drag the brake show...and will me an short life for the bearings.

Ray


Keep in mind that some of that 1/8th inch of play can come from other places besides the wheel bearings. By that I mean some of that can be ball joint wear (uppers/lowers or a combination of both, along with excess upper torsion bar end play (lacking an adjustment of the upper torsion bar).
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Marvel
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PostPosted: Mon May 24, 2021 12:33 am    Post subject: Re: Master Cylinder Diameter Reply with quote

raygreenwood wrote:
Marvel wrote:
I've fitted a new 19.05mm diameter Beetle master cylinder and the pedal feel is much better. The previous one must have been a 17.46mm Beetle one as the pushrod was already the correct length. The car now pulls up in a straight line too. But, and there is always a but, it feels like the left front brake is being applied when turning left and something tugs the steering when hitting a bump in the left hand side. The wheel bearings are adjusted with approximately 1/8" movement at the rim. Any ideas? It's drums all round by the way.



Your wheel bearing adjustment sounds suspect...."1/8" movement at the rim"...rim of what?

Wheel bearings can be adjusted a couple of different ways....all slightly different but close enough.

The most common is to tighten the spindle nut while spinning the drum or rotor...until the tightness stops the rotation in about 1/2 rotation...then back off about 1/3 to 1/2 turn.

An alternate is a version of this but checking that the machined washer under the spindle nut can be shifted lightly with force from a screwdriver tip. Not ideal....but very similar to the first method in result.

Or....use a dial indicator in the hub center to measure deflection/play while using some variant from above.

Measuring 1/8" of play at the tire rim...means a lot of slack in the bearings. That will cause the drum to misalign in turns and drag the brake show...and will me an short life for the bearings.

Ray


1/8" movement is at the wheel rim

To adjust I tighten the lock nut while rotating the drum until it is snug but not impeding the rotation of the drum then back it off half a flat.

On closer inspection it looks like the back plate is bent so will correct this. I also note that there is no steering damper. It looks like the threaded insert in the beam for the fixed end is missing. I guess its had a RHD beam fitted to a LHD car.
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PostPosted: Mon May 24, 2021 9:46 am    Post subject: Re: Master Cylinder Diameter Reply with quote

Marvel wrote:
raygreenwood wrote:
Marvel wrote:
I've fitted a new 19.05mm diameter Beetle master cylinder and the pedal feel is much better. The previous one must have been a 17.46mm Beetle one as the pushrod was already the correct length. The car now pulls up in a straight line too. But, and there is always a but, it feels like the left front brake is being applied when turning left and something tugs the steering when hitting a bump in the left hand side. The wheel bearings are adjusted with approximately 1/8" movement at the rim. Any ideas? It's drums all round by the way.



Your wheel bearing adjustment sounds suspect...."1/8" movement at the rim"...rim of what?

Wheel bearings can be adjusted a couple of different ways....all slightly different but close enough.

The most common is to tighten the spindle nut while spinning the drum or rotor...until the tightness stops the rotation in about 1/2 rotation...then back off about 1/3 to 1/2 turn.

An alternate is a version of this but checking that the machined washer under the spindle nut can be shifted lightly with force from a screwdriver tip. Not ideal....but very similar to the first method in result.

Or....use a dial indicator in the hub center to measure deflection/play while using some variant from above.

Measuring 1/8" of play at the tire rim...means a lot of slack in the bearings. That will cause the drum to misalign in turns and drag the brake show...and will me an short life for the bearings.

Ray


1/8" movement is at the wheel rim

To adjust I tighten the lock nut while rotating the drum until it is snug but not impeding the rotation of the drum then back it off half a flat.

On closer inspection it looks like the back plate is bent so will correct this. I also note that there is no steering damper. It looks like the threaded insert in the beam for the fixed end is missing. I guess its had a RHD beam fitted to a LHD car.


You need to tighten just a hair more when setting up your bearings. Then back off so they roll properly.

One thing I started doing many years ago....when I ran into a rash of bearings that just could not seem to have a useful lifespan no matter how they were adjusted.....is to adjust as we have talked about here...and then use a dial gauge to check the play at the center hub.

What I found was bearings whose overall combined center hub and inner race tolerances...were way off. They were just crappy bearings. By the time you hit factory specs for wheel bearing play...they would have to be far too tight.

It got me seriously looking at bearing quality. This was about 1996/97. It was the beginning of the "China" bearing invasion. A lot of these at the time were sold under the "BOC" name....many were unmarked for country or origin.

Ray
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PostPosted: Mon May 24, 2021 11:32 am    Post subject: Re: Master Cylinder Diameter Reply with quote

raygreenwood wrote:


You need to tighten just a hair more when setting up your bearings. Then back off so they roll properly.

One thing I started doing many years ago....when I ran into a rash of bearings that just could not seem to have a useful lifespan no matter how they were adjusted.....is to adjust as we have talked about here...and then use a dial gauge to check the play at the center hub.

What I found was bearings whose overall combined center hub and inner race tolerances...were way off. They were just crappy bearings. By the time you hit factory specs for wheel bearing play...they would have to be far too tight.

It got me seriously looking at bearing quality. This was about 1996/97. It was the beginning of the "China" bearing invasion. A lot of these at the time were sold under the "BOC" name....many were unmarked for country or origin.

Ray


Yup, I ran into that around the same time frame. I just requested Timken bearings and races when I needed bearings. Trying to find a dealer that carried FAG bearings was harder, even though there's a big Fag plant on I-44 in Missouri.
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71 Notch ...aka Krunchy; build pics here;
http://www.thesamba.com/vw/forum/viewtopic.php?t=249390 -been busy working
64 T-34 Ghia...aka Wolfie, under construction... http://www.thesamba.com/vw/forum/viewtopic.php?t=412120
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Marvel
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PostPosted: Wed May 26, 2021 8:59 am    Post subject: Re: Master Cylinder Diameter Reply with quote

I thought I'd found the problem. The inner wheel bearing was the wrong diameter so the inner race was locating on the radius not the spindle. I got four new FAG bearing from the local bearing factor and fitted them. They adjusted up perfectly. Went for a drive and it still pulls to the left. It's ok with gentle braking and gradually increasing the pressure but stamp on the pedal and it snatches the wheel. What else can be wrong with it?
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PostPosted: Wed May 26, 2021 9:14 am    Post subject: Re: Master Cylinder Diameter Reply with quote

What condition are your soft lines in?
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PostPosted: Wed May 26, 2021 9:57 am    Post subject: Re: Master Cylinder Diameter Reply with quote

They look ok from the outside but that is my next thing the replace.
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PostPosted: Wed May 26, 2021 10:14 am    Post subject: Re: Master Cylinder Diameter Reply with quote

Marvel wrote:
I thought I'd found the problem. The inner wheel bearing was the wrong diameter so the inner race was locating on the radius not the spindle. I got four new FAG bearing from the local bearing factor and fitted them. They adjusted up perfectly. Went for a drive and it still pulls to the left. It's ok with gentle braking and gradually increasing the pressure but stamp on the pedal and it snatches the wheel. What else can be wrong with it?


Ok...you are doing the good diagnostics!

I would stay on track and replace the soft hoses. Bleed it again....and then check.

If I were to say from your description what could still be the issue....one of two things. You note that braking seems even at slow speeds/low level braking...and pulls at high speeds/harder braking.

1. Yes...it could be a hose choking off the higher flow braking on one side. This will cause it to pull to the opposite side. Or,,,just as easily.... selling and losing pressure on one side....so causing the opposite side to pull.

2. This can also be air still in the system. Just small amounts will do this. So at low braking pressure its decent. At higher pressures the air bubble compress down small relieving pressure. Ray
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PostPosted: Tue Jun 01, 2021 5:14 am    Post subject: Re: Master Cylinder Diameter Reply with quote

Not only are the master cylnder and wheel bearing the wrong diameter the hub seals are too. The ones fitted are 40 x 50 8.5. I think they should be 38 x 50 x 6.5 Does this sound right for an early '65 drum braked car?
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