Bonneville America Forums Forums Technical Forums Accessories Converting the America to twin disc

OK, so I now have all the major parts to get the project up and running. What I would like to know is, would it be better to run two single brake lines, one to each caliper from the master res or stick with the standard.

Parts accumulated

2007 Speedmaster wheels (complete)
2007 Speedmaster forks (complete)
Speedmaster fender/mudguard
extra brake line (cross over from left to right)
Matching pair of brake calipers off 1999 Tiger

Still want the clips to go on the mudguard and the bolts to attach the caliper to the forks, what size are these?

The clips Brent was selling to hold the break line and were discontinued are still available at J&P Cycles.

Hi Ian, you don't know the part numbers do you or a link would be nice...

Sorry man I had a heck of a time finding them again. the part number is 9700126.

But if you want a copy of the instructions...let me know

It doesn't have the part num,bers on..I looked.

And where's the pump?

For two calipers you need a pump with larger piston.

It's different between one disk or two disks setup.

The one from any TBS or Speedmaster will be ok.

pump? do you mean master cylinder? if so the america and speedmaster are the same

Frank

Yes the master cylinder into the pump on the right hand.

Commonly between one and two disks setup the cylinder pump is bigger or longer to achieve pressure for more pistons on the calipers.
With one disk/one caliper you need pressure for two pistons, for two calipers you need for four pistons.

The brake reservoir on the America is 11mm and the one on the Speedmaster which is the same as the one on the Rocket 3 is 1/2 which is a difference of 2mm.

I will run with the 11mm one and if necessary upgrade to the 1/2 if it is needed. Mert is running the 11mm and says she has no problems with the front brake, time will tell

The upgrade to the 1/2 Speedmaster/R3 second hand runs about £75.00 or $160.00 or you could buy new at a cost of £151.00 + VAT @ 17.5% + Delivery (ouch)

When I changed my speedmaster hoses to stainless, I changed to 2 separate hoses.

bsr aerotek provided all of mine and were very helpful with advice as well


Steve

The 2 master cyl. are definately different but I can't figure why. They should either put the 2mm larger one one the America too or the smaller one on all. I also know someone who is running the America cyl. on a dual caliper conversion and has had no problem in a couple years now.I think it's been 2 full seasons now but not sure.

my mistake

Frank

You can do, but your America will have the same braking power of an Harley.

Some Harley users, like the owners of the XL1200C or 883C/883stadard use to mount the XL1200R master cylinder maintaining the single disk together with braided line, better pads and floating disk to have more braking power.

Leaving stock master cylinder with two calipers on the America you'll need 4 fingers for strong stopping power, instead of 2.
Nothing bad because both TBA and SM braking systems are oversized expecially on the SM where I feel poor modularity on braking power delivery.

I've tried both and America has good braking power, SM has huge braking power, I tried to use 4 fingers like on my previous XL1200C and caused wheel blocking and tyre noise. I was falling.
Similar to my dual 6 pistons Tokico calipers with 310mm floating disks on my Kawa ZRX1200.

Birchr I am using 2 seperate lines(one to each caliper). I got rid of the crossover line so I could go to a larger tire.......ANGELIS

Gina and Mechano're right - it'll work with the America master cylinder but to get the benefit of the twin disks you need the right master. With the standard master the pressure supplied by the master is divided across two callipers, lowering the pressure on each set of pads. The piston in the speedy master has a 2mm longer throw which gives you greater hydraulic pressure at the callipers.

If you're only going to twin disks for appearance it probably won't make much difference until that day that you really need to throw the anchors on. I'm upgrading because I need more braking when I tow a trailer so I wouldn't even think of compromising my braking by using the smaller master.