Putting larger brake wheel cylinders in the rear

[74 Thing]

I know there has been common practice or putting larger brake wheel cylinders in the back (eg, replace the stock rear 17mm brake rear brake cylinders with 22mm brake cylinders) to help with braking when running Cal-Look with larger rear tires (talking about 4 wheel drums).

By doing this will it effect brake pedal throw before a solid pedal is felt?

With the stock set up I got a firm brake pedal some 1" in, but with larger brake wheel cylinders in the back the pedal throw is like half way to the floor before I feel anything.

I have done the pressure bleeding as well.

Thanks

[FreeBug]

This is serious stuff not to be approached haphazardly. I have ever improved rear braking without at least some improvement in front, like disks or twin leading shoe. It is more interesting to increase breaking surface area rather than cylinder size alone. Remember:

Front brakes break loose: no biggie

Rear brakes break loose: spin city

[modok]

The pedal travel should be 34% more than it was before.

[UK Luke 72]

I did mine recently.

Yes the pedal moves more but is not an issue.
I have braided lines to go on but not got round to it yet. I fitted drilled front discs and performance pads with new stock hardware at the rear and love how the car has reacted. Braking hard with a bit of steering angle suddenly doesn't try to kill me.
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[Vanapplebomb]

It’s a good idea to change up the wheel cylinders when changing sizes of tires, or disrupting the weight bias of the car.

Example, on rail buggies. I put the small 17mm rear wheel cylinders up front because with no body work or gas tank, the front is so light that I can pick it up myself. My buggy has 33” tires in the rear, and a heavy Vanagon transmission, gas tank, and Type 4 engine in the back. I actually modified the backing plates so I could use Super Beetle 23.6mm front cylinders in the rear, even larger than the standard bug 22mm front cylinders. It was a pretty easy swap. The bolt hole for the cylinder has to be slotted due to the different mounting boss to bolt hole spacing, and it needed a shim between the cylinder and backing plate. By doing these mods, it brakes beautifully, just like a stock car. Having the standard wheel cylinder arrangement like a full bodied car is just downright dangerous in a buggy. Way to much braking up front if you don’t swap things around.

So, in a cal-look, if you got bigger meatier tiers at the back, it may be work beefing up the rear cylinders a bit to keep brake balance the same.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[74 Thing]

I jacked up the rear of the car since I replace the rear wheel cylinders to take a crack at bleeding again. Sure enough there was still some air in the lines.

The pedal is much much better now. I am going to run it for a while and see how the larger rear wheel brake cylinders feel.

Thanks

[BFB]

i looked into wheel cylinders a while back with my local guy that sells empi and most of there's used the same wheel cylinders. he knew they were different from factory but looked like aftermarket just used a one size fits all approach.
so even if u go to the local parts store , and you buy a front wheel cylinder thinking its a larger wheel cylinder is it really? obviously if you have to modify your backing plate its some how different. but otherwise maybe its just the same part? something to think about is all
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[j-dub]

[modok]

[Wreck]

[oprn]

[74 Thing]

I have to say the braking is much better with the larger front brake cylinders in the back as well. I have 22mm ATE brake cylinders on the front and the rear, with steel braided flex lines, and semi metallic shoes all around. I used syli glide brake grease on the friction points on all of the backing plates and shoes.

I will probably try to bleed one more time to make sure I got all the air out. The pedal travel is just a little more than it was before with the 17mm cylinders in the back.

Mine are all late model backing plates with the 3 contact spots and the larger groove in the cylinders.

A question is how often should wheel cylinders be replaced? I bleed/flush every two years since I know brake fluid attracts water, and use Castrol LMA fluid, but to be honest I have never paid close attention to the cylinders. They are very simple with boots on the ends then pistons and seals and a spring, but they live in a harsh environment and crap can get under the boot and start to pit the pistons and cylinder walls and effect performance.

I hate bleeding brakes!

[sjbartnik]

[modok]

A larger master would get the pedal back up, but so would using
using the 17mm cylinders front and rear. Or maybe you would prefer all 19mm then it would be near same as stock?
It's just leverage, you can't have it both ways.

[74 Thing]

I like it the way it is with 22mm cylinders all the way around.

Mostly the pedal was due to more air in the system that came out the next morning when I jacked up the rear in the air so that the cylinders were as high as the reservoir.

[Alstrup]

Beware that if you swop to a larger master cylinder the pedal pressure needed increases too.
I wrote a novel about the subject on another forum some years back. If it still exists I will paste to here.
Although I must admit that I have never done the 22/22 mm set up on drum brakes. We would have swopped to front discs way before that point. But I see the idea if the car does some off roading.
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https://www.thesamba.com/vw/forum/viewtopic.php?t=435993

[74 Thing]

Hi Torben,

Please post the link to the post you made if you can find it.

I read a post by you using 944 wheel cylinders in the back at cal-look.no.

I had a new set of front ATE 22mm wheel cylinders so I tried them in the back of the Thing to see the outcome. So far so good-the Thing has larger/heavier tires on the back and the 181 rear brake drums are so much heavier than the front too so the larger wheel cylinders seem to be helping a lot.

I am keeping my master as is-its a volume and pressure compromise.