single to dual discs

[Ronkom]

Years ago when I restored my Eldo, I mounted the second disc/caliper on the front wheel w/out changing the front brake master cylinder on the handlebar. I'm sure the feel would be better and the lever would require less effort with a change out to a larger master cylinder, but the brake has worked fine.
Question: I have an EV front wheel w/the extra caliper to mount on a Stone. Is it absolutely necessary to change the master cylinder, or, can I expect the same type of performance I have on the Eldo? Anybody done this?
Thanks,
Ronkom

[Rich A]

I put a second disc on my Jackal (w sidecar attached), and didn't change the MC. I know other people will say that it is essential to change the MC, but I'm fine with the set-up as it is. The lever action is softer now, of course, but I can still lock up the front. My suggestion would be to try the smaller one, and change it out if you don't like the feel.

Rich A

[Orange Guzzi]

Visit this web site for clarifications: http://vintagebrake.com/mastercylinder.htm

Your life may depend on it.

[Rich A]

More info on MC/brake ratios:

http://www.customfighters.com/forums/showthread.php?t=56704

Disclaimer--sounds reasonable to me, but I can't vouch for accuracy.

Rich A

[cruzziguzzi]

I certainly don't know beyond my experience with 4 wheeler upgrades but I think at a minimum, to cope with expected (only possible?) higher applied pressures - I'd be certain to use braided steel lines. This, based upon others telling me they have needed to "grab" harder when going from 1 -2 discs on the same MC. No science there of course, just set of the pantsiness.

Todd.

[Ronkom]

As usual it seems I've stepped into a pile. I was at a Piaggio/Guzzi/Triumph shop in Richmond Va. recently & saw 2 Triumph models fitted w/dual front discs w/straightforward Master Cylinders w/attached reservoirs. They appeared to be Brembo units. My thought at the time was if I did need to change from the single disc MC to check into the price of the MC assembly used on those bikes as it might be a "bolt on" for the Stone (w/ teflon/SSmesh brake hoses). BUt from what I read now, there's more to it. The disc & wheel diameters have to be factored in. The EV wheel going on the Stone is 18" with discs about 12.5" in diameter. My memory of the Triumphs is that the front wheels looked smaller than 18" & I didn't look closely at the discs. I'm going to email the dealer & ask for the dimensions (& verify that they are Brembo brakes). I'll post back to this thread when I get the info.
Ronkom

[rodekyll]

If M/c's were readlily available in 0.5mm increments the diameters of the wheels and brakes and such might make a difference in your purchase choice.  But in reality, there are only about three choices 'in range' for the pump ratio you want.  In axial m/cs they are 13, 15, and 17mm.  In radial they are 19 and 21mm.  That's one reason folks add or subtract a caliper without changing m/c -- you just can't tune to the optimal sweet spot on the bell curve.  So it's safe to toss the detail values and just concentrate on the basic relationship between master and slave volumes.

Sizing choices are a girl-dog for a lot of things.  We did the math for my differential gear ratio here last year.  After sorting out he final drive ratio on the Convert and looking around, I decided that 4.88 gearing was optimal.  My choices for the 7.5" punkin were 4.66 and 5.12.  So a lot of the nuance figures we arrived at for wheel height and tire ratio were wasted -- no way to dial in the reality to the numbers.  With nothing available in the sweet spot, I erred to the lower gearing.  We should find out if it works or not sometime next week.

[Orange Guzzi]

Two other factors to consider if you are changing calipers and/or master cylinder.  The surface area of the brake pads and the length of the lever on the master cylinder.

[krglorioso]

Several years ago I converted both my Hydro Stones to dual front discs.  Best upgrade possible!  I cannot praise too highly the substantial increase in stopping power.  I always felt that the single front disc was very marginal for stopping safely, especially with two up and a hard stop coming.  Not any more!

The OEM master cylinder is 13mm bore size and does not flow enough brake fluid for an additional caliper.  I wanted a 16mm and sourced two used mid-2000s Suzuki V-Strom master cylinders (either 650 or 1000cc variants) on e-bay for about $70 each.  They work fine and can use the mirror mount clamp from the OEM Guzzi master cylinder so your mirrors will remain at the same height. 

I did not run dual hoses, but rather ran a crossover line (19.5" with 30 degree offset banjos) made for me by Russell, tho any maker of braided stainless hoses can make this.  To do this you will need one double length banjo bolt from MG Supply and a few extra copper washers.  I had to buy OEM rubber blocks and the chrome plate for for the second cable guide on the other side of the front fender at a dealer's but not the chromed wire cable guide, which the dealer priced at $29!  I made one out of stainless 1/8" rod and it looks and works fine.

Ralph

[Ronkom]

Wow, quick response from Chelsea (owner of the Piaggio/Guzzi/Triumph shop.

 Hey there Ron! Let's see if I can answer all of these questions effectively for you.

1. There are Brembo brakes dual front discs used on two models.

2. Those models are the Daytona 675 R and the Speed Triple (and Speed Triple R).

3 and 4. The Daytona specs:
310mm disc brake rotor
120/70 x 17 front tire
Master cylinder with lever: T2025931 $204.65

The Speed Triple specs:
320mm disc on the front brake rotor
120/70 x 17 front tire
Master cylinder with lever: T2024850 $197.91

I hope this helps with your search! :)
Chelsea

OK, 17" to 18" wheels, not all that much difference. The 320mm disc is, I think, the same size as the EV ones I'm putting on the Stone. And that MC is less $$. What d'yall think? Buy one, make up some teflon/ss brake hoses w/a splitter (4 way, w/a hydraulic brake light switch) Bolt it up, fill it up, bleed & go?
Ronkom, yea....I know....it's NEVER that easy!

[jetmechmarty]

I certainly don't know beyond my experience with 4 wheeler upgrades but I think at a minimum, to cope with expected (only possible?) higher applied pressures - I'd be certain to use braided steel lines. This, based upon others telling me they have needed to "grab" harder when going from 1 -2 discs on the same MC. No science there of course, just set of the pantsiness.

Todd.

It sounds to me like you understand it backwards.  If adding a caliper without changing the master, stopping actually takes less effort.  Yes, the stainless lines are a good idea.

The master cylinder bore is too small if the lever comes back to the grip and you don't stop.  It's too large if it takes a great deal of squeeze with little travel and feels wooden.

[Rich A]

The OEM master cylinder is 13mm bore size and does not flow enough brake fluid for an additional caliper. 

? Did you actually try the 2 caliper set-up with the 13 mm MC ?

I kept the stock MC and added a second disc. The lever travel is a bit longer, but stoppage is no problem. I think you only need to move the pucks something under a mm.

Rich A

[Triple Jim]

I added a 2nd front disk to my H2 about 35 years ago, and kept the 14mm master cylinder.  As long as the pads were square to the disks, it worked fine.  I eventually bored the master to 16mm and installed a 16mm rebuilt kit, and that's the way it is now.  I did that because when I changed pads, it was too mushy until they wore in to match the disks perfectly, and that took the better part of 1,000 miles.

So it might work OK with the stock master, especially since the Guzzi system has a Microswitch at the lever, and doesn't use the pressure switch in the fluid line that adds a little mushiness.  In the worst case, you won't like the excessive lever travel and can get a different master cylinder.  They are readily available and many options are inexpensive.

[Antietam Classic Cycle]

Wow, quick response from Chelsea (owner of the Piaggio/Guzzi/Triumph shop.

 Hey there Ron! Let's see if I can answer all of these questions effectively for you.

1. There are Brembo brakes dual front discs used on two models.

2. Those models are the Daytona 675 R and the Speed Triple (and Speed Triple R).

3 and 4. The Daytona specs:
310mm disc brake rotor
120/70 x 17 front tire
Master cylinder with lever: T2025931 $204.65

The Speed Triple specs:
320mm disc on the front brake rotor
120/70 x 17 front tire
Master cylinder with lever: T2024850 $197.91

I hope this helps with your search! :)
Chelsea

OK, 17" to 18" wheels, not all that much difference. The 320mm disc is, I think, the same size as the EV ones I'm putting on the Stone. And that MC is less $$. What d'yall think? Buy one, make up some teflon/ss brake hoses w/a splitter (4 way, w/a hydraulic brake light switch) Bolt it up, fill it up, bleed & go?
Ronkom, yea....I know....it's NEVER that easy!

I haven't done that conversion, but, wouldn't it be the same as a V11 Sport , as an example. Same calipers, discs same diameter. That bike uses a 16 mm master cylinder. MG Cycle offers a 16 mm Brembo master cylinder for $144:

http://www.mgcycle.com/index.php?main_page=product_info&cPath=110_112&products_id=2909

The description pretty much says it all:
Brembo hand brake master cylinder, 16mm. This master cylinder is used to operate two 4 piston calipers on motorcycles without integrated front/rear brakes. For example, Jackal with 2nd disk added.

[Don G]

Read Guzziology on this topic.  ;-T DonG

[Orange Guzzi]

The two websites reference in previous post (vintage brake and custom fighters) explain the relationship between master cylinder piston diameter and the "total" surface area of all the pistons in the caliper (s).  The ratio chart at vintage brake is a good source to get you started.  A caliper is not just a caliper.  They have one, two, three, four or more pistons.  They have various size pistons in one caliper.  Calculate the surface area of all the pistons in all the calipers attached to the master cylinder to determine the ratio.    Piston area (Pi x r squared x number of pistons) divided by the area of the master cylinder piston (Pi x r squared)  equal ratio.  

High ratio equal squishy and strong brakes  higher than 27:1
low ratio equal wooden and weak brakes  less than 23:1


As mentioned above, run one hose to the right caliper, use a double banjo bolt, three seal washers, run the second brake line from the right caliper over the fender to the left caliper using a single banjo bolt and two seal washers.  I use Goodridge brand hoses and fittings.  I have found that buying the fittings and installing them first and then measure the length of line you will need takes the guess work out.  

Brembo calipers use m10 x 1.0 banjo bolts  other brands us m10 x 1.25.   Some use 12 mm.   Be sure to check the thread size if mixing parts.  

I am not a big fan of brake light banjo bolts.  They add to the squish factor.  Not much, but something.  If you can get a master cylinder with a mechanical switch use it.


Goodridge parts and numbers  http://www.gotyournose.com/goodridge/usa/pdf/motorcycle/Goodridge_metric_full_mc.pdf

Stainless Steel Fittings you will need if using brembo
Part No.
Description
B592-03C
Straight 10mm Banjo  2 each, on for master cylinder, 1 for left caliper

B593-03C
15 Deg. 10mm Banjo one for right brake caliper hose to master cylinder (use another one on the master cylinder or a straight one, which ever works best)

B599-03C
90 Deg. 10mm Banjo

992-03-31C      2 each one on each end of the hose that runs from right to left caliper
10mm X 1.0 Banjo Bolt

993-03-31C
10mm X 1.0 Double Banjo Bolt  1 each use on right caliper with two hoses attached

single banjo bolt on master cylinder 1 each
l
ColorFlex Brakelines
Part No.
Description
83309
Universal Stainless Braided Brake Line (F to F) 9"
83311
Universal Stainless Braided Brake Line (F to F) 11"
83312
Universal Stainless Braided Brake Line (F to F) 12"
83315
Universal Stainless Braided Brake Line (F to F) 15"
83316
Universal Stainless Braided Brake Line (F to F) 16"
83317
Universal Stainless Braided Brake Line (F to F) 17"
83318
Universal Stainless Braided Brake Line (F to F) 18"
83319
Universal Stainless Braided Brake Line (F to F) 19"
83321
Universal Stainless Braided Brake Line (F to F) 21"
83323
Universal Stainless Braided Brake Line (F to F) 23"
83324
Universal Stainless Braided Brake Line (F to F) 24"
83325
Universal Stainless Braided Brake Line (F to F) 25"
83326
Universal Stainless Braided Brake Line (F to F) 26"
83328
Universal Stainless Braided Brake Line (F to F) 28"
83330
Universal Stainless Braided Brake Line (F to F) 30"
83332
Universal Stainless Braided Brake Line (F to F) 32"
83334
Universal Stainless Braided Brake Line (F to F) 34"
83336
Universal Stainless Braided Brake Line (F to F) 36"
83338
Universal Stainless Braided Brake Line (F to F) 38"
83340
Universal Stainless Braided Brake Line (F to F) 40"
83342
Universal Stainless Braided Brake Line (F to F) 42"
83343
Universal Stainless Braided Brake Line (F to F) 43"
83344
Universal Stainless Braided Brake Line (F to F) 44"
83346
Universal Stainless Braided Brake Line (F to F) 46"
83347
Universal Stainless Braided Brake Line (F to F) 47"
83350
Universal Stainless Braided Brake Line (F to F) 50"
83352
Universal Stainless Braided Brake Line (F to F) 52"
83354
Universal Stainless Braided Brake Line (F to F) 54"
83360
Universal Stainless Braided Brake Line (F to F) 60
  

[Rich A]

As mentioned above, run one hose to the right caliper, use a double banjo bolt, three seal washers, run the second brake line from the right caliper over the fender to the left caliper using a single banjo bolt and two seal washers.  

I used a double banjo on the MC and ran a second line to the add-on caliper. I fabricated a guide that attached to the fender for the new cable.

Rich A

[Triple Jim]

Calculate the surface area of all the pistons in all the calipers attached to the master cylinder to determine the ratio.    Piston area (Pi x r squared x number of pistons) divided by the area of the master cylinder piston (Pi x r squared)  equal ratio.

One other thing:  Two opposed pistons count the same as a single if it's the usual floating design, because piston travel is approximately double for the single piston that brings both pads to the disk.  One pad is moved directly by the piston, and the other is moved when the piston's cylinder is pushed away from the first side, causing twice the actual piston travel.

[charlie b]

Following along Rich's advice, and other's comments.

How far does your brake lever move now?  If you add another caliper it will move twice that much (almost exactly).

If your lever will not hit the grip, then you are good with the current m/c.

Why would putting both calipers on the hand lever make it stop faster?  If you use your foot and hand lever you are using all three disks to stop.  One of the things linked brakes has tought me is to use the foot as much (or more) than that hand for braking. 

[krglorioso]

Ron:  While you're doing the dual front brake conversion, why not also do the tubeless wheel conversion?  Two really fine upgrades, which I've done several years ago and am very satisfied with.

Ralph