1200ts
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- USA - Riverside CA
I have just put four pot calipers on my RGS. I was rebuilding the master cylinder and I see it is a 14mm. Is this OK or should I use a 15mm?
Four pot calipers on a RGS. Master cylinder size?
- Thread starter 1200ts
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Laverdalothar
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- Germany
I use a 16mm one as on the Ducatis and Zanes of that time. But why don't you try first and see if you like the feeling and braking power?
However, there might be a reason why Ducati and Laverda and Moto Guzzi used 16mm brake masters on their bikes with the 2 4-pots. I just went with what was used on other bikes, never tested it with 14mm master. Might cause long lever travel to engage fully, potentially even to a point where it isn't fully engaging. I just have no experience, it's just guessing over here. So...:
-Safe road: go with 16mm
-fun road: try the 14mm first and see how you like it (and please report back)
However, there might be a reason why Ducati and Laverda and Moto Guzzi used 16mm brake masters on their bikes with the 2 4-pots. I just went with what was used on other bikes, never tested it with 14mm master. Might cause long lever travel to engage fully, potentially even to a point where it isn't fully engaging. I just have no experience, it's just guessing over here. So...:
-Safe road: go with 16mm
-fun road: try the 14mm first and see how you like it (and please report back)
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14mm will result in a rather soft lever with long travel, but possibly awesome stopping power with little effort. Check that the lever doesn't bottom out!! Possibly not suitable for track riding where the pressure point can shift due to temperature differences.
Can't go wrong with 15 (actually 15.8mm with Brembo) or 16mm-5/8".
piet
Can't go wrong with 15 (actually 15.8mm with Brembo) or 16mm-5/8".
piet
Normski
Senior member
- Location
- Devon, England
I’m just about to change from 14mm to 5/8” on a double disc set up for the reasons mentioned above. Too much lever travel and fierce braking effect, manageable but not ideal.
Ian Short
Full member
- Location
- Cambridge Ontario
A proper way to evaluate would be to calculate the area of all 8 of the caliper pistons and then calculate the area of the master cylinder you want to use. Then divide the area of the master cyclinder into the total area of all 8 pistons....... if you are in the 22:1 ratio range you should be happy. Off the cuff I would say a 17mm or even a 19mm will work if you are using 4 piston brembos with 32mm pistons.
I run dual six piston beringer's on a couple of my bikes and use a 21.4mm master cylinder piston and it works out to a 21:1 ratio.
FYI
14mm master cylinder piston area = 154mm sq'd
15mm master cylinder piston area = 177mm sq'd
16mm master cylinder piston area = 201mm sq'd
17mm master cylinder piston area = 227mm sq'd
19mm master cylinder piston area = 283mm sq'd
4 piston Brembo with 32mm pistons x 2 calipers
16 x 16 x 3.14 = 804mm sq'd per piston
8 pistons x 804 per piston = 6432mm sq'd
6432 / 227 = 28:1 ratio for 17mm master cylinder
6432 / 283 = 22.7:1 ratio for a 19mm master cylinder
I run dual six piston beringer's on a couple of my bikes and use a 21.4mm master cylinder piston and it works out to a 21:1 ratio.
FYI
14mm master cylinder piston area = 154mm sq'd
15mm master cylinder piston area = 177mm sq'd
16mm master cylinder piston area = 201mm sq'd
17mm master cylinder piston area = 227mm sq'd
19mm master cylinder piston area = 283mm sq'd
4 piston Brembo with 32mm pistons x 2 calipers
16 x 16 x 3.14 = 804mm sq'd per piston
8 pistons x 804 per piston = 6432mm sq'd
6432 / 227 = 28:1 ratio for 17mm master cylinder
6432 / 283 = 22.7:1 ratio for a 19mm master cylinder
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Ian Short
Full member
- Location
- Cambridge Ontario
Phillipe Dahn at Frog Specialties is the North American distributor for Beringer brakes and is located in California as is Steve Allen at Bevel Heaven. Both are great guys and I'm sure would help ensure that you have the correct setup.
Cheers
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CDHE
Full member
- Location
- Boulder, Co
Good info here: https://www.vintagebrake.com/mastercylinder.htm
That's all correct...
By far the most popular 4-pot mods for the Laverdas are Brembo P4-32/32 or 30/34 or the Beemer OE 30/34 by Brembo. In these cases at least, generic 15.8/16mm/ 5/8" AXIAL MCs are the best options. Radial MCs are a different matter, lever geometry takes up a lot more of the equation.
Up to the RGS, all Laverda triples had PS15 MCs fitted, these have a 15.8mm piston diametre which pretty much equals 5/8" in accordance to the standard practice of using imperial units in hydraulics. The RGS received PS14 units, 14mm or 9/16", these greatly enhanced braking performance with the stock P08 calipers.
piet
v2ventiler
Senior member
CLEMTOG
Hero member
I firstly used the stock Brembo master cylinder when I converted to 4 pots and 320mm discs, (with 27mm offset, no adapter for the normal 7mm type, which as well as wrong offset has differring PCD, plus the speedo gearbox does not clash) it was OK. Next I used an 80's Triumph master cylinder which worked a little better (I also used the clutch master for a big improvement in effort) next I used a Ducati 916 master cylinderand it was/is now perfect, dead easy, no sums, just a bit costly, I then used the 916 master for the clutch and IT IS SUPER LIGHT. its not jsut the piston size that changes but the geometry of the perch, I wont try to go any further.
CLEM
CLEM
chrisk
Hero member
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- Brisbane, Australia
Sounds like something is amiss if they are binding that badly
Ian Short
Full member
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- Cambridge Ontario
That's an excellent observation that I failed to highlight........ I run radial master cylinders on all of my bikes....... both of the dual six piston Beringer's run 21.4mm radial master cylinders and I run a 14mm Brembo radial on my supermoto with a four pot Beringer (fyi all the pistons in my Beringer's are 27mm).
I am a huge Beringer fan and they have an impressive build quality but they are pricey. My Brembo is at a much more accesible price point and works great.
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1200ts
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- USA - Riverside CA
A dilemma indeed. I have both 14mm (9/16") and 15mm (5/8") master cylinders and can't decide which one to try?
The calipers are 30/34 Brembo gold line and are new.
The calipers are 30/34 Brembo gold line and are new.
Go for the 5/8", can't go wrong.
Gold, black, purple... makes no difference, hydraulics are colour blind.
piet
Laverdalothar
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- Location
- Germany
Have the same on my two bikes since I changed to 4-Pots. Simply took what others (including Laverda Zane's....) used and never looked back. That's I think 20 years or so ago.
No need to overcomplicate things. Simply use what other bike manufacturers pair with these calipers and off you go. No need to re-invent the wheel.
Ian Short
Full member
- Location
- Cambridge Ontario
For what it's worth, this is from the '95 Guzzi 1100 Sport workshop manual. They run the 30/34mm 4 pot pistons (which is close enough to the area of the 32mm piston when 8 pistons are evaluated).
They run the 5/8" (16mm for this discussion) master cyclinder.
A good friend of mine loves the brakes on that Guzzi...... I think it's the same set up that they used on the Ducati 916's of that era.
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1200ts
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- Location
- USA - Riverside CA
I tried the 14mm and it worked OK but a little too much lever travel.
Put on a 15mm and it feels better.
So either size would work but the 15mm is a better choice.
Put on a 15mm and it feels better.
So either size would work but the 15mm is a better choice.