steve m
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| posted on 2/12/16 at 07:23 PM |
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Which wheel cylinders 20.6 or 17.8 ?
Think ive got a leak on the offside rear cylinder, so need to buy some new cylinders, and just wondered which size will be better for my non servo 7
however I do run a twin system, and do have adj bias
I believe they come in 20.6 and 17.8 id
Why the difference ? and why, as in why different sizes are available
steve
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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gremlin1234
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| posted on 2/12/16 at 07:40 PM |
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quote:
Why the difference ? and why, as in why different sizes are available
you can think of it as hydrolic leverage,
most of the sizes increase to piston/bore size in eighths of an inch (even the 'metric' ones)
edit: eighths not sixteenths
[Edited on 2/12/16 by gremlin1234]
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JAG
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| posted on 2/12/16 at 10:35 PM |
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They come in different bore diameters because the same drumbrake used to be fitted to several different vehicles.
If the wheelbase or the height of the Centre-of-Gravity of the car changed then the wheel cylinder diameter would be changed to modify the output of
the brake. This way you make sure that the front wheels always lock before the back wheels and you can meet the legal requirements when you come to
homologate the car.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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Bluemoon
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| posted on 3/12/16 at 09:21 AM |
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As you have adj bias, so long as the adjustment is not all-one way and your happy with the brake balance then you might as well replace like for
like..
Dan
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ianhurley20
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| posted on 3/12/16 at 09:30 AM |
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20.6 is fitted to the heavy Sierra rear brakes where the smaller 17.8 fits the ford ka. Both cylinders are the same externally. I used the smaller
cylinder with Sierra drums to ensure there was no rear brake locking under braking problems for IVA on my Haynes. As yours is a 7 ish car I would go
for the smaller piston dia
[Edited on 3/12/16 by ianhurley20]
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rusty nuts
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| posted on 3/12/16 at 10:05 AM |
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If you don't have any problems with the braking system why not replace with the same size you already have?
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steve m
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| posted on 3/12/16 at 11:05 AM |
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Rusty, you are right, but I will probably replace both at the same time, as they have been on the car 17 years
but wondered, which one to go for,
steve
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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rusty nuts
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| posted on 3/12/16 at 11:55 AM |
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Measure the diameter of your existing cylinders and replace like for like. Changing the cylinder size may cause problems with brake locking or effort.
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