Twin Piston Calipers on a '78 GL

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Don R
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Re: Twin Piston Calipers on a '78 GL

#61

Post by Don R »

Old Fogey wrote:Not to argue against Bob's long knowledge, but some more explanation of why the change works.

The GL1000 (all models) use twin 38.10mm diameter single piston calipers giving a total piston area of 2280mm²

The GL1100 ('82) uses twin double 30.1mm diameter piston caliper giving a total piston area of 2846mm²

That's a difference of 25%, quite significant in view of the small amount of fluid transferred by the master cylinder even if you still use the GL1000 17.5mm (11/16”) diameter master (240mm² area)

It means that the ratio goes from 9.47:1 to 11.83:1, giving more lever travel and less lever effort for the same braking level.

It gets even better if you change the master cylinder as well for the 15.8mm (5/8”) diameter (196mm² area) version from the '82 GL1100 or many of the Hondas from the 80
The ration then goes from 11.83:1 to 14.56:1. This is right in the ideal ration band for single sided calipers.

Now we can start talking about some real braking with much less effort. Yes, the lever travel is more, but that's a good thing as you are far more able to modulate your braking.

This is the setup I have on my own bike. Combined with the stainless lines and drilled discs, I have no worries about stopping now, whereas the standard setup is little short of lethal in today's traffic especially in the rain!

Randakk has a great article on this in the ad for the upgraded Randakk Master Cylinder
https://www.randakks.com/upgraded-front ... iston.html
And the 32mm pistons are approx. 3215 sq mm
78 GL 1000, 70 CB750 sandcast, 70 CB836 hot rod, 1124cc 750 dragbike resto project.
You don't need a weatherman to know which way the wind blows.
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Re: Twin Piston Calipers on a '78 GL

#62

Post by Sidecar Bob »

Assuming the numbers in post #61 are correct you would need to use the GL1000's 17.5mm master cylinder with the 32mm dual piston calipers to retain close to the same ratio as you would have with the 15.8mm master and 30mm calipers.
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Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
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Re: Twin Piston Calipers on a '78 GL

#63

Post by SnoBrdr »

Sidecar Bob wrote:Assuming the numbers in post #61 are correct you would need to use the GL1000's 17.5mm master cylinder with the 32mm dual piston calipers to retain close to the same ratio as you would have with the 15.8mm master and 30mm calipers.
What would happen if you don't?

I ask as I switched and kept the original m/c.

Stops much, much better.
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Re: Twin Piston Calipers on a '78 GL

#64

Post by Sidecar Bob »

Which bike's original m/c?

If you used the 1000's master with 32mm dual piston calipers you should have pretty close to the ratio John recommended That should have a lot more lever movement before you lock the brakes, which should let you modulate them better.

If you used an early (pre-linked) 1100's original master with 32mm calipers it will still work but there will be less lever movement which, while less optimal should still be acceptable.
Mr. Honda ('83 GL1100/Dnepr) summer How a motorcycle evolves thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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Re: Twin Piston Calipers on a '78 GL

#65

Post by SnoBrdr »

Sidecar Bob wrote:Which bike's original m/c?

If you used the 1000's master with 32mm dual piston calipers you should have pretty close to the ratio John recommended That should have a lot more lever movement before you lock the brakes, which should let you modulate them better.

If you used an early (pre-linked) 1100's original master with 32mm calipers it will still work but there will be less lever movement which, while less optimal should still be acceptable.
78 m/c.

So you're saying it will be even better using another m/c?
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Re: Twin Piston Calipers on a '78 GL

#66

Post by Sidecar Bob »

I'm saying that, according to John's numbers, the '78 m/c with 32mm dual piston calipers should be pretty close to optimum.
Mr. Honda ('83 GL1100/Dnepr) summer How a motorcycle evolves thread
The Famous Eccles ('84 CX650EI/VeloUral) winter Never Ending Build (CX500forum)
Click: Colour schematics for all GL1000 & GL1100 and GL1200 standard models plus instructions on how to download the full size version
"A guy with two sidecars can't be all bad." - Cookie
Another guy with two sidecars..... Hmmmm... must be something to that....
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Re: Twin Piston Calipers on a '78 GL

#67

Post by SnoBrdr »

Sidecar Bob wrote:I'm saying that, according to John's numbers, the '78 m/c with 32mm dual piston calipers should be pretty close to optimum.
Thanks, all his numbers threw me.
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Don R
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Re: Twin Piston Calipers on a '78 GL

#68

Post by Don R »

Good, that's what I was thinking, I just wanted to calculate the 32mm calipers area for anyone wondering.
78 GL 1000, 70 CB750 sandcast, 70 CB836 hot rod, 1124cc 750 dragbike resto project.
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Re: Twin Piston Calipers on a '78 GL

#69

Post by Bear151556a »

Well, to add a little to the conversation, my RH front caliper on my 1985 Aspy developed a pretty bad leak, so I was without a bike while I am waiting for parts. My buddy pulled the rh front caliper of of my 1983 aspy parts bike and swapped it out. Tho it is smaller, it bolted right on and bled out perfectly. He said the only problem was snaking the 1985 caliper out, guess it was tight with the 16 inch rim. This leads me to believe that the larger 1200 calipers might fit on the 1100s.
1977 Gl1000 Standard---Ran last year, Just needs a battery,carbs might be dirty(yeah right) sold
1983 Gl1100 Interstate--In need of beautification, runs like a dream
1983 Gl1100 Aspencade-Parts for above
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Re: Twin Piston Calipers on a '78 GL

#70

Post by Damferg »

action1 t
Wingersparty wrote:
Don R wrote:In case you want to know:
45210-445-632 = BRACKET, Right Front.
45110-445-632 = BRACKET, Left Front.
Thanks, this is very useful. I used http://www.cmsnl.com to track the models that uses the same part. You just have to insert part number and it shows what models the part fits. For example 45210445632:

DESCRIPTION
fits:
Honda product number:45210445632
CMS product number:HO0065.2860

FITS MODELS
CB1100F 1983 (D) ITALY
CB700SC NIGHTHAWK S 1984 (E) USA
CB700SC NIGHTHAWK S 1985 (F) USA
CB700SC NIGHTHAWK S 1986 (G) USA
CB750F 1981 (B) JAPAN RC04-102
CB750F 1982 (C) AUSTRALIA
CB750F 1982 (C) ENGLAND
CB750F 1982 (C) EUROPEAN DIRECT SALES
CB750F 1982 (C) FRANCE
CB750F 1982 (C) GENERAL EXPORT KPH
CB750F 1982 (C) GENERAL EXPORT MPH
CB750F 1982 (C) GERMANY
CB750F 1982 (C) SOUTH AFRICA
CB750F 1983 (D) AUSTRALIA
CB750F 1983 (D) ENGLAND
CB750F 1983 (D) EUROPEAN DIRECT SALES
CB750F 1983 (D) ITALY
CB750F 1983 (D) SOUTH AFRICA
CB750F 750 SUPER SPORT 1981 (B) USA
CB750F 750 SUPER SPORT 1982 (C) USA
CB750F2 1982 (C) AUSTRALIA
CB750F2 1982 (C) ENGLAND
CB750F2 1982 (C) EUROPEAN DIRECT SALES
CB750F2 1982 (C) FRANCE
CB750F2 1982 (C) GENERAL EXPORT KPH
CB750F2 1982 (C) GENERAL EXPORT MPH
CB750F2 1982 (C) GERMANY
CB750F2 1982 (C) SOUTH AFRICA
CB750F2 1983 (D) AUSTRALIA
CB750F2 1983 (D) EUROPEAN DIRECT SALES
CB750F2 1983 (D) SOUTH AFRICA
CB750FB BOLD'OR 2 1981 (B) JAPAN RC04-102
CB750SC 1984 (E)
CB750SC 1985 (F)
CB900F 1981 (B)
CB900F 900 SUPER SPORT 1981 (B) USA
CB900F 900 SUPER SPORT 1982 (C) USA
CB900F TYPE2 1981 (B)
CB900F2B BOL D'OR
CB900FB BOL D'OR
CX400E 1982 (C)
CX500E 1982 (C)
CX650E 1983 (D) AUSTRALIA
CX650E 1983 (D) AUSTRIA
CX650E 1983 (D) BELGIUM
CX650E 1983 (D) CANADA
CX650E 1983 (D) ENGLAND
CX650E 1983 (D) EUROPEAN DIRECT SALES
CX650E 1983 (D) FRANCE
CX650E 1983 (D) GERMANY
CX650E 1983 (D) GERMANY / TYPE 2
CX650E 1983 (D) ITALY
CX650E 1983 (D) NORTH EUROPE
CX650E 1983 (D) SOUTH AFRICA
CX650E 1983 (D) SWEDEN
CX650E 1983 (D) SWITZERLAND
GL1100 1982 (C)
GL1100 GOLDWING 1982 (C) USA
GL1100D 1982 (C)
GL1100I 1982 (C)
GL1100I GOLDWING INTERSTATE 1982 (C) USA
GL650 SILVERWING 1983 (D) USA
GL650I SILVERWING INTERSTATE 1983 (D) USA
GL700I 1983 (D) JAPAN
VF700F INTERCEPTOR 1984 (E) USA CALIFORNIA
VF700S SABRE 1984 (E) USA CALIFORNIA
VF700S SABRE 1985 (F) USA CALIFORNIA
VF750F INTERCEPTOR 1983 (D)
VF750F INTERCEPTOR 1983 (D) USA
VF750F INTERCEPTOR 1984 (E)
VF750F INTERCEPTOR 1984 (E) USA CALIFORNIA
VF750S SABRE 1982 (C) USA
VF750S SABRE 1983 (D) USA
VF750S SABRE 1985 (F)
VF750S SABRE1984 (E)
VT1100C SHADOW 1100 1985 (F) USA CALIFORNIA
VT1100C SHADOW 1100 1986 (G) USA CALIFORNIA
This product fits to 77 models.
Amazing information, thank you!
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Re: Twin Piston Calipers on a '78 GL

#71

Post by pidjones »

I have a couple of the CB750C dual piston calipers, but not the brackets that will mount them to a GL1000. Tonight, I'll be giving them to a club member to take to the Barber swap meet.
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Re: Twin Piston Calipers on a '78 GL

#72

Post by desertrefugee »

Been sort of half-heartedly looking for a pair of early 1100 twin pot calipers for the CBX. Easy swap. Brakes are fine, but you know how the custom bug can be...
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Re: Twin Piston Calipers on a '78 GL

#73

Post by tomk1960 »

desertrefugee wrote:Been sort of half-heartedly looking for a pair of early 1100 twin pot calipers for the CBX. Easy swap. Brakes are fine, but you know how the custom bug can be...
'

I have a set that are powder coated and fully rebuilt with all new components, ready to go. I'll work a deal with ya. ;)
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Re: Twin Piston Calipers on a '78 GL

#74

Post by desertrefugee »

Uh oh. PM sent.
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Re: Twin Piston Calipers on a '78 GL

#75

Post by flyday58 »

tomk1960 wrote:
desertrefugee wrote:Been sort of half-heartedly looking for a pair of early 1100 twin pot calipers for the CBX. Easy swap. Brakes are fine, but you know how the custom bug can be...
'

I have a set that are powder coated and fully rebuilt with all new components, ready to go. I'll work a deal with ya. ;)
I also have a set if anyone else is looking.
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