Topic: Dual disc on 550 help

[Greyhound]

To reverse calipers..You also have to grind out rivits and turn fender brace around if you run stock fender.
  How does it hold up?
 I had drilled stock rotors, duals , witn calipers turnec to back . Stock master cylinder and -3 braided lines .
 One day I had to panic brake at about 85 mph.. i backed off when the tire started chirping and hopping., and no Cal.. my forks did not fold up. Had quite good brakes...2 or3 finger braking most of the time.
 But i agree with Scottly, one good 300 or 320mm floater with  better caliper.... is far far lighter than the old duals.

You’re tire started chirping because the calipers were turned to back? And what do you mean the forks did not hold up? Are you saying running calipers in the back is not safe after all?

[754]

 No it worked fime, i backed off to avoid wheel lockup at 75 to 80  mph.
 I think brake pads then worked better than some of todays choices.
 Calipers turned back, no issues.. lighter steering.

[Greyhound]

Good to know, why don’t more people run the calipers in the back?

In any case, it looks like the twin piston calipers arrived to the 750 in 1978? And since they still used the same hub as the 550, should marry up to each other no prob, right?

Do the calipers differ if they originally came mounted to a Comstar wheel?

[flatlander]

my 550 came already with stock dual disks that a PO had installed. so i can't compare it with a single disk setup. definitely, it was front heavy like that - but the weight distribution of the bike is front heavy anyway so i can't comment on how big a difference it made for handling. i assume that steering was affected, but i'd still not call it sluggish.

i've replaced the disks with drilled and thinned ones from godffery. over the 2 disks, that shaved off ca. 1.7kg of weight.
at the same time i got also new rims which are a bit lighter and a lot stiffer than OEM. steering has noticeably improved with these changes, and i can brake with 2 fingers at any speed.

turning calipers to the back: i think that would make a real handling improvement but would yet have to try that. i've got a fork brace, and the OEM 550 forks with new progressive springs. of course newer forks would be stiffer and lighter.
the bike steers and handles well as it is now (for a 40+ year old bike), and does so a lot better than with the PO setup. so it's all relative.

generally i agree that a modern single disk setup will be lighter and still outbrake the OEM parts. it all depends what you want...

[bryanj]

Back in the 70's before the 550 came to UK i ran a 500 with one caliper in front and one behind

[flatlander]

Back in the 70's before the 550 came to UK i ran a 500 with one caliper in front and one behind

on the same fork leg? that would be quite a sight 

[754]

Only started reading this yesterday , so i been thinking on it..
 Do your current forks have  mounts on each leg for calipers.. if they do .. why change to 750 forks.  Difference for rotor size is in tge brake hanger and rotors and calipers....for 6 hole factory brakes.

[Greyhound]

Yes, both fork legs have mount holes for dual calipers. I was considering the later 750 fork legs to be able to run the twin piston calipers that started in 1978 (and before Comstars).

Or would those calipers/brackets mount up to the 550 fork legs too?

[RAFster122s]

550 fork legs support the swing arm style caliper like you have that was used on the cb750. The arm is a different length on the cb750. They do not support the calipers used on the 78 cb750.

[Greyhound]

Ah right. Do you know if I could just swap out the fork leg lowers (since they’re both 35mm) to use the newer twin pot calipers?

If so, would I use the 276mm 550 discs?

[754]

I think all twinpot caliper use the 5 bolt wheels.. 

[754]

If you have dual mounts  ? Do you ?
 Then..
 You can yse any of the 6 bolt rotors, BUT  to use 750 stuff you need swing bracket arms to go with 750 caipers.. which go with the larger rotors EBC make thinner floating 6 bolt rotors., 

[Greyhound]

Ah okay, so using six bolt (thinned) discs with the twin pot calipers just won’t work because if offset?

[desertrefugee]

Mother McCree and General Jackson.  I mentioned following with interest, but holy schiedt.   

A braking system is critical.  <check>
A misstep can be problematic <check>
There are options for upgrades <check>
OEM mix/match can be done  <check>
There are some subtleties <check>

But, it ain't rocket science.  I think much of the issue here is Greyhound needs to do this publicly and in a day.  If it weren't for that, I suspect this thread wouldn't have run nineteen (OK four) pages.

Gather parts, get the bike on the table and go after it.  Run into a fitment/clearance/function problem?  Address it and move on.  At the end of the day, it's just not a huge deal.  But, actual hands on is the best way to get it done.  Particularly since all the info (and more) needed to make it happen is already presented here. 

Even if you run into an issue that'll take more than a few hours to resolve, just put the thing back together and go at it when you're positioned to address the issue.

I believe I mentioned in one of the earlier nineteen pages about recently having upgraded my Vmax with Hayabusa front calipers.  No real weight difference (lighter calipers offset the higher rotor mass).  Other than the adapter, it was pretty much a non-event - until I rode the bike.   Nice to have real brakes. 

Dive in.  Make it happen.

[Greyhound]

Much of the info I’ve gathered on this mod, including many others, I’ve read on posts made as long as 10yrs ago, so one of the goals here is to find (if possible) a bolt-on solution that anyone who is reading this later on can source the parts and do it (ideally) without too much fabbing (as well as someone doing it in the street) because at the end of the day, anything is possible in a machine shop.

[754]

The simple solution .
 Get a 2nd 500 caliper and rotor , and long bolts. Longer banjo bolt and extra brake line. Some shims and bolts to mount 2nd caliper. A speedo eliminator or reworked spare speedo drive . If you eliminate speedo add bicycle speedo to rear wheel, it works.
 Now you will get done in an afternnoon.. worst case put it back to how you started.


I be back to check on this thread tonite.

[Greyhound]

Ya that’s really looking like the best option after all, second to just throwing on a bigger 42.8m caliper and 295mm rotor with SS lines and a phenolic piston, which I’m actually leaning toward simply because it will leave the front end light and still (marginally) increase breaking power.

[seanbarney41]

Super easy solution for single disc with dual piston caliper is 83 cb650c...slap the whole frontend on a 550 and go

[Alan F.]

Looked it up:
78 CB550
64 degrees 105mm trail

83 CB650SC
61.5 decrees 98mm trail

Sounds like it'd be fine, I wonder if fork length is close?

[Greyhound]

Hmm the CB650C fork diameter is also 35mm, so if I just slipped the fork tubes into the 550 triple, the trail wouldn’t even change (provided the length is the same).

However, the CB650C has Comstar wheels, meaning I’d need the wheel too.

What would it take to switch the rear wheel to Comstar on a 550? (and another can of worms opens  )

[seanbarney41]

Hmm the CB650C fork diameter is also 35mm, so if I just slipped the fork tubes into the 550 triple, the trail wouldn’t even change (provided the length is the same).

However, the CB650C has Comstar wheels, meaning I’d need the wheel too.

What would it take to switch the rear wheel to Comstar on a 550? (and another can of worms opens  )

not all of them...got one with 19"x1.85 chrome steel spoked D.I.D. goodness sitting right in front of me...actually would rather have the comstar lol

Maybe it's not a C?  I don't know my 650's very good yet

[Alan F.]

Oh sorry, you said 1983 so I looked up the DOHC 650 which was dual disk with a cast alloy wheel and leading axle forks. You can probably adapt the rear wheel from a late model CB1100 for a near match in the rear.

If you want Comstars go with a tubeless set to save weight over tube type Comstars.

[Greyhound]

Very interesting. I’ll save the Comstar considerations for another thread. At this point, just want to rebuild the old caliper and get on the road with formidable braking power.

[Greyhound]

I got a pretty good deal on the larger 750 calipers and brackets, I’m wondering if dual 42.8mm calipers would be overkill for the 550?

[bryanj]

I think you need the 750 sliders or complete forks as mountings are a different distance from wheel spindle