Twinpot Brake upgrade on 78 Skunk

[oohsam]

Silly me.
I just did some research and found the answer. One side of the caliper pushes the pistons out, which force one side of the onto the disc. The force continues, and since the piston side is hard on the disc, this makes the entire caliper body slide along the rails which pulls the other side onto the disc...Sorry guys.

Here is the article I found which explains this.

The basic answer is that once the piston is extended to its max, the entire caliper body then slides equalizing the value on both sides.

http://enderw88.wordpress.com/automotive-theory/brake-system-theory/

"Why pressure from only one side?

This can be a little confusing and some very smart people have gotten caught. But it really isn’t that hard to understand if we shift our thinking a bit. First, ignore whether or not the caliper is fixed or floating; it doesn’t matter, and in a minute you’ll see why.

Imagine that you are holding a book between your two open hands. Now squeeze on the book. If your left hand is pushing with 25 pounds of force, then your right hand has to push back with that much force or the book will move across your chest. Each of your hands is a brake pad, and the book is the rotor. The force between the pad and the rotor is only 25 pounds, not 50. And it is the force between pad and rotor that determines the frictional force generated on the brake rotor.

In this respect there is no difference between floating and fixed calipers. The other side just acts to keep the rotor centered in the caliper, one moves the whole caliper, the other moves the other pistons.

But wait! There are still two pads, one on each side. If we replace one pad with a ball bearing surface the force on the rotor from the brake caliper would be reduce about half. So we have to count both pads, but using the force generated by one side of the pistons."

[salty_monk]

Pm'd you back but looks like you sorted it yourself.

Check clearances to the back of all those bolts between bolt tip and rotor carefully.

I consider 3mm absolute minimum Clearance and I have run one bike at that for a few thousand miles. prefer to have more.

[salty_monk]

Still got a couple of sets of brackets left in plain steel... Let me know if you need a set.

Debating getting some more sets made up.. Latter stages have been a bit slow (either due to saturation or economy or both I suspect).

Let me know if you are on the fence & likely to want a set in the coming 6 months. This could be the last time I run this.

[ndaugbjerg]

Salty Monk, Don't know if my memory is correct but I recall something about a brake upgrade for the gs450. 550 rotor and a brand H pot or something. I guess the two primary issues are rotor bolt pattern and caliper bracket. I have the facility to fab the bracket but it wouldn't take much to talk me into taking an easy way out. Just picked up an '82 450E. I have all the new parts to get it on the road but want to do ssome upgrades asap. Riding weather is just a few weeks away here on the Texas coast.
Thanks,
Niels

[salty_monk]

Niels,

It's untested on the 450. I do have an odd single bracket if you want to be the guinea pig though....

If it works then it would work with the GS550 rotor (296mm) or one of the Honda rotors from the CBR F3 (with an adapter which I also have).

[salty_monk]

Wow 12000 views...

Just bumping this up for the weekend. Come get the last couple of sets!

[jfman]

Have you experimented with SV650 front calipers using these brackets?

Reason I ask is that the guys over on the kawasaki concours forum bolt them directly to their bikes with no mods.

Would that mean that they work with you brackets?

[salty_monk]

I believe the SV ones are the same as the DL (vstrom) ones aren't they? Twinpot sliding pin design with 2 pistons same size.

If so then they don't work.... What year Concourse? The early ones I would think as they came with a single pot caliper like our bikes. The 2000-2005 ones use the Caliper these brackets were designed for which is also twinpot sliding pin the same so there would be no benefit.

[salty_monk]

Just bumping this up in case anyone is in need

[Assaf]

Hi Mr Monk et al

Been looking through this post, but being a bit of a novice I didn't really manage to work out what upgrade options exist for me.

Can someone help explain please, or point me towards the info I need?

I have a 1986 GS850G (same as 1983). I might need to replace the front callipers as the piston cavity is corroded. Replacement callipers are of course hard to find, so I was wondering whether I can broaden my options by considering the callipers from other models.

I came across this thread, but as I say I didn't really understand.

Can someone assist? Mr Monk, do you have something suitable for me?

Many thanks if you can help.
Assaf

[salty_monk]

Pm to you. If its the same as the US g bikes you can do this same mod.

[Assaf]

Thanks Mr Monk

If I could just ask a few questions please. I do apologise if the answers are within this thread, but it's a damn long thread and I didn't manage to keep track past a couple of pages.

You wrote in your PM to me "If its the same as the G bikes here you can fit the twinpot calipers from Kawasaki Ninja or concourse along with Honda CBR disks/rotors using the bracket and spacer sets that I sell."

Where can I find details and prices of the kits? *Are they in this 11 page thread somewhere?

Also, am i right in understanding that this upgrade does not require changes to the master cylinder, reservoir etc. *In other words, if i order the parts you mention and IF all other items on my bike are original and in good shape then that's all i'll need to perform the upgrade. *Is that right?

What part numbers or years of calliper and rotor do I need to find?

And lastly, does this setup provide improved breaking ability, or is it just an alternative given that original parts are hard to find?

Many thanks
Assaf

[greg78gs750]

stoked to do this mod this winter. not sure i can wait that long. hey saltymonk, i know most of the info is out there in the forum, but have ya thought about putting a write-up on cliff's site? really appreciate your pioneering efforts on this!

greg

[greg78gs750]

assaf, in resopnse to some of your questions, i hear it gives true 2 finger braking to our bikes. so, performance upgrade to say the least. i think all my stuff to do the switch came to about $350 or so, that includes the kit (that i got from another member who wasnt using them), some VERY NICE ebay calipers (2004) some pretty nice cbr rotors, new seals for the calipers, and some shiny new ss brake lines. so, not exactly "cheap", but i gotta spend my money somewheres.....

[salty_monk]

It really improves the braking. 2 finger braking really is possible & also give a lot more feel.

For you to Israel I'd have to work out postage but bank on $75 plus shipping for the bracket set.

You will be looking for late 80's Kawasaki Ninja Tokico calipers (or the same ones were on the 2000-2005 Kawasaki Concourse).
Honda CBR 600 F3 model rotors.

Other than a way to drill the new holes in the ROtors using the template (the spacer also acts as a drilling jig) & a hacksaw to cut 5mm off the speedo drive dust cover (required in 70% of cases) that's all you need. Stock Master Cyl works fine.

Dan