Topic: Dual disc question - in front or behind the fork leg?

[bikebitzofvt]

Well, I've read just about all I can find on here, and elsewhere, regarding the upcoming dual disc conversion on my 74 550K.  I have all the parts - the mechanics of it aren't really an issue.  It's more of an aesthetic question - should the calipers go in front (on top) of the rotors - stock position - or behind the fork legs by swapping fork legs left to right?  I'm leaning towards the behind the leg look myself - mostly 'cause it looks faster... 

Any downside to this? 

I think they might get a little better cooling in front of the leg, but that's about it.  The only other thing I can think of is the bleeder screw position - I'll likely bench bleed them before installation.

Any thoughts would be appreciated!  Once my caliper seals & rotor bolts come in I'll document the job here...

Oh, one other question - will the dust boots from say a 77 550F fit my forks in place of the stock accordion boots? 

Thanks!

[Retro Rocket]

Any downside to this? 

Never done it on a 550 but on a 750 the front guard mount ends up on the wrong side of the forks, you may have to mod the front guard or use an after market one...

Mick

[ev0lve]

I vote for behind the forks too  

Bleeder screws will be mirrored. If your model has bleeders in kind of a V then the second caliper will have its bleeder in the top position when reversed. Not a big deal really. Just kind of a pain.

Not familiar with the calipers on the 550 either but assuming they're close to the 750 the adjustment screw will need replacing with something that has a bolt head on it so you can actually adjust it. A little tough to get a screwdriver in there with the duals but a wrench just squeaks by.

Had to turn my fender around to fit the forks. More talented folks just re rivet the bracket in the right position.

Oh, you didn't ask but... if you do decide to turn the forks around run your brake lines straight to the calipers. I bought some stainless lines when I was going to have the calipers up front (and that would have fit right) but with them backwards the lines are a bit too long with the hardlines and look a little sloppy. Also you'll lose most of the hangers and guides so things like speedometer cables will rub your nice newly wrapped pipes if you don't zip tie them off pretty tight.



OK. That's all I can think of  

[bryanj]

Whatever you fancy but you will have to alter the fender, i even ran a 500 with one in front and one behind

[lordmoonpie]

I can't see much difference in the way of performance - surely it's all about aesthetics, so if you liek it one way, go with it. I left my 750 conversion in front purely because that's the way it was in 1969 and I wanted to echo that style, nothing more nothing less.

Oh - well I suppose it was easier to do the conversion that way too

[steam-powered man]

i've rear-mounted the front caliper on my 550k and the only small prob i noticed is that the fork brace is asymetric.  had to use a sfh to tweak it. 

some will say rear-mounted brakes are more "flickable" due to the weight of the caliper/mount/hardware behind the forks rather than in front.  doubly-so in your case.
bobp 

[lordmoonpie]

Wonder what they mean by flickable? It won't change sprung or unsprung weight so maybe it's just a perceived rather than real difference?

[voxonda]

The thing is that the weight of the calipers is closer to the centre of the "steering axle". So it needs less input to change direction. sorry for my limited technical english.

Rob

[fishhead]

some will say rear-mounted brakes are more "flickable" due to the weight of the caliper/mount/hardware behind the forks rather than in front.  doubly-so in your case.
bobp 

 It's more "flickable" because the weight of the caliper(s) is lower when they are mounted to the rear of the forks and gives the front end/steering a lower center of gravity(lighter feel).

 Mounted in the stock front location, when you are in a corner, the higher mounted weight will have a tendacy (SP?) to "fall" to the inside of the corner. With the calipers mounted to the rear of the forks (lower) this is reduced alot.

You can feel the difference that it makes with another front end. With the front mounted caliper and the wheel turned a little, the higher weight of the caliper will "push/fall" to the inside (of the imaginary corner). If you turn the forks around, the lower center of gravity of the rear mounted caliper wont "push/fall" like the front mounted caliper does.
  
 In theory it works, but the average street rider wont notice much of a difference. The racer may notice a difference at racing speeds.

 

[MCRider]

some will say rear-mounted brakes are more "flickable" due to the weight of the caliper/mount/hardware behind the forks rather than in front.  doubly-so in your case.
bobp 

 It's more "flickable" because the weight of the caliper(s) is lower when they are mounted to the rear of the forks and gives the front end/steering a lower center of gravity(lighter feel).

 Mounted in the stock front location, when you are in a corner, the higher mounted weight will have a tendacy (SP?) to "fall" to the inside of the corner. With the calipers mounted to the rear of the forks (lower) this is reduced alot.

You can feel the difference that it makes with another front end. With the front mounted caliper and the wheel turned a little, the higher weight of the caliper will "push/fall" to the inside (of the imaginary corner). If you turn the forks around, the lower center of gravity of the rear mounted caliper wont "push/fall" like the front mounted caliper does.
  
 In theory it works, but the average street rider wont notice much of a difference. The racer may notice a difference at racing speeds.

 

What he said.

All modern sportbikes have them on the back, so its more than cosmetic, its a very small thing to a street bike rider, a larger thing to a performance rider, but still small. Easy for the factory to do so why not?

[bwaller]

Like LMP says it is rarely noticable for street use, but the theory is sound. If you're using a stock fender then wheel removal/installation is a pain, but life is full of pain!

Here's a pic of one approach to bleeding, just zip-tie a spare disc and hang the caliper with the bleeder pointing north.

[fishhead]

Well, I'm not trying to insult any one, but I CRINGE every time I see a bleeder thats not pointing up.

  When someone puts in all the effort to dual disc their bike (modifying the speedo drive plate, getting the 2nd caliper mounted and correctly lined up, longer disc bolts,etc) and then get "befuddled" by trying to remove the conic inversor that is under the hard line (where it seals), I just shake my head. Out of all the things that need to be done to convert to dual disc, removing the pressed in conic inversor, isn't hard by comparison.

   If you have the caliper apart, put a shortened nail throught the conic inversor (I dont remember the size of the nail) and the head of the nail will pull the inversor out when it is pulled with vice grips. You can tap on the vice grips to help with removing the inversor.

 Didn't work? Still have the caliper apart ? Run a thread tap through the inversor and then put a bolt through a washer and tighten it up. It will pull the inversor out. Using a longer bolt and a socket (instead of a washer) works good too.

  Didn't pull your caliper apart? Run a wood screw into the inversor and use a chisel/screwdriver with a hammer(on the wood screw) to knock the inversor out.

Have to reuse the inversor to put the hard line back in the "other" hole?
 Put it in your drill and use a file to remove any burrs that may have happened.

Not using the hard line? Chuck the inversor in the trash as it is not needed when removing the hardline and going to a one peice line.

 Rant Over.
 

 
 

[ev0lve]

Well, I'm not trying to insult any one, but I CRINGE every time I see a bleeder thats not pointing up.

  When someone puts in all the effort to dual disc their bike (modifying the speedo drive plate, getting the 2nd caliper mounted and correctly lined up, longer disc bolts,etc) and then get "befuddled" by trying to remove the conic inversor that is under the hard line (where it seals), I just shake my head. Out of all the things that need to be done to convert to dual disc, removing the pressed in conic inversor, isn't hard by comparison.

   If you have the caliper apart, put a shortened nail throught the conic inversor (I dont remember the size of the nail) and the head of the nail will pull the inversor out when it is pulled with vice grips. You can tap on the vice grips to help with removing the inversor.

 Didn't work? Still have the caliper apart ? Run a thread tap through the inversor and then put a bolt through a washer and tighten it up. It will pull the inversor out. Using a longer bolt and a socket (instead of a washer) works good too.

  Didn't pull your caliper apart? Run a wood screw into the inversor and use a chisel/screwdriver with a hammer(on the wood screw) to knock the inversor out.

Have to reuse the inversor to put the hard line back in the "other" hole?
 Put it in your drill and use a file to remove any burrs that may have happened.

Not using the hard line? Chuck the inversor in the trash as it is not needed when removing the hardline and going to a one peice line.

 Rant Over.

Bring the rant Fishhead! I had no idea how to get it out, reversed and set up and didn't find anyone talking about it.

From the noob perspective my biggest worry was destroying things I didn't need to destroy from lack of knowledge. Even with the board and FAQs I killed a few things in the process.

If you could knock out some pics of the process and add them to the dual brake FAQ I (and more than a few others I'm sure) would be pretty thankful  

[bwaller]

Well Daniel,

Don't mean to make you cringe, #$%* I wish I hadn't posted that pic now!  It's a good point you make, fact is when I added #2- 35 years ago I didn't know it could be removed. Even switching the bleeder won't put the hole completely vertical on these things. As long as there is a means to bleed them.

The 500 calipers are a little different, with the calipers reversed the bleeder will never point north. Bleeding requires the bracket be removed to manipulate the caliper. One point for those folks using a banjo fitting where the hard line WAS, after removing the conic inversor run a blind tap to allow a few extra threads which then allows a banjo bolt to tighten safely. 

[Bill/BentON Racing]

You got a lot of good info in the reponses,I roadraced a 1972 500w/592cc Yosh 550 motor
that Pops ported the head on,I did mine,dual setup,you can feel the difference on the track
esp Road A,put the calipers in the rear for all the reasons listed,function first,looks second
you win both ways,The little 592 was highest placing Jap bike in Vintage 4 @the GNF finals
at Road A in 1988,H1s,H2s,and CB750s were all present,the 4 in front were all 850cc's or bigger!

[bwaller]

Welcome aboard bellcow, I don't mean to get this offtrack but did you have any trick transmission parts tucked away in the bottom end of your Yosh 592?

[Industrial Cafe]

just swap sides with the calipers (left to right)... wouldn't that fix all your bleeding woes?

[ev0lve]

just swap sides with the calipers (left to right)... wouldn't that fix all your bleeding woes?

Nope. Unfortunately.

[Industrial Cafe]

poop...

edit:   why not? the line faces up and thats where the air wants to go.

[ev0lve]

poop...

edit:   why not? the line faces up and thats where the air wants to go.

Hmm, I don't have a good picture of both but make a V with your fingers (inlet and bleeder) then turn your hand around. That's pretty much why. Basically all the calipers are left handers.

Swapping the fittings would make it right but I have the fear.

[bikebitzofvt]

Wow, I didn't expect to get two pages with my lil question!

Thanks for all the great thoughts.  I'll be using a fiberglass fender rivited to a reversed stock brace.  Running new lines suzuki style - down to right caliper, splitter in middle going to left.  No hard line.  They will end up behind the leg, I think. 

Steering response is one bonus I hadn't thought of - thats a great point.  Now to get that damper mounted while I'm at it...

Fish - thanks for the heads up on that little piece of steel inside there, I never knew it had a real name!  That's something I missed in all the threads I'd read!  I thought I was going to be cutting down banjo bolts...  I'm going to try to pull it out like the welch plugs on most cv carbs first, run a machine screw into it and pull.

Bwaller - your bike is incredible!!!  Those look like 81 GS550MZ Katana rotors on the front.  I have a set downstairs that still have the orange paint in the centers.  One might think it came straight from the Honda factory in 84 or so - they got on that black/silver kick with some of the V-45 Sabre's - I'll send a PM with some other questions... Or do you have a link to a build thread?

IC makes a valid point - bench bleed then zip tie the MC so the return port is open, any stray air bubbles should move up and out in a day or so...

Bellcow- You raced nationals in 72?  I've a great personal friend and mentor that was in the scene back then - from White Plains, New York - he campaigned a Suzy titan in green & white livery - He told many a great story about the On Any Sunday filming almost all of which he ended up on the cutting room floor!

Thanks again, everyone - this site is awesome in the knowledge that people are willing to share!

[Industrial Cafe]

poop...

edit:   why not? the line faces up and thats where the air wants to go.

Hmm, I don't have a good picture of both but make a V with your fingers (inlet and bleeder) then turn your hand around. That's pretty much why. Basically all the calipers are left handers.

Swapping the fittings would make it right but I have the fear.

oh God, DUH!  I wasn't thinking clearly. thanks

[Industrial Cafe]

Wow, I didn't expect to get two pages with my lil question!

Thanks for all the great thoughts.  I'll be using a fiberglass fender rivited to a reversed stock brace.  Running new lines suzuki style - down to right caliper, splitter in middle going to left.  No hard line.  They will end up behind the leg, I think. 

Steering response is one bonus I hadn't thought of - thats a great point.  Now to get that damper mounted while I'm at it...

Fish - thanks for the heads up on that little piece of steel inside there, I never knew it had a real name!  That's something I missed in all the threads I'd read!  I thought I was going to be cutting down banjo bolts...  I'm going to try to pull it out like the welch plugs on most cv carbs first, run a machine screw into it and pull.

Bwaller - your bike is incredible!!!  Those look like 81 GS550MZ Katana rotors on the front.  I have a set downstairs that still have the orange paint in the centers.  One might think it came straight from the Honda factory in 84 or so - they got on that black/silver kick with some of the V-45 Sabre's - I'll send a PM with some other questions... Or do you have a link to a build thread?

IC makes a valid point - bench bleed then zip tie the MC so the return port is open, any stray air bubbles should move up and out in a day or so...

Bellcow- You raced nationals in 72?  I've a great personal friend and mentor that was in the scene back then - from White Plains, New York - he campaigned a Suzy titan in green & white livery - He told many a great story about the On Any Sunday filming almost all of which he ended up on the cutting room floor!

Thanks again, everyone - this site is awesome in the knowledge that people are willing to share!

that wasn't me it was bwaller.
i was the one with the useless post of confusion.

[lordmoonpie]

Hmm, I like the theory about the caliper being closer to the spindle and lower so the centralised mass is lower but making a noticeable difference in riding terms, even to a track racer? Not sure about that. You must be talking fractions of a gram of real effect and offset against that is some wibbly wobbly human dangling all over the CofG in the middle. I agree that in pure physics it's a valid point, but noticeable to the rider I'm not signing up to

[MCRider]

Hmm, I like the theory about the caliper being closer to the spindle and lower so the centralised mass is lower but making a noticeable difference in riding terms, even to a track racer? Not sure about that. You must be talking fractions of a gram of real effect and offset against that is some wibbly wobbly human dangling all over the CofG in the middle. I agree that in pure physics it's a valid point, but noticeable to the rider I'm not signing up to

You need to experience it. The bike in my avatar had both in front. My next CB750 had both in back. Made a difference to me.

YMMV