Topic: Dual disc on 550 help

[Greyhound]

Ahh okay, so there is absolutely no way to distinguish which type is in there unless the wheel comes off?

For the sake of anyone else reading this in the future, would it be possible to show exactly how both need to get modified?

Also, this way I can prepare whatever tools I may need yo be able to tackle either option once the wheel comes off (since I’m doing this in the street, and would prefer as little time down as possible).

[RAFster122s]

For all the whinging you have been doing about this you could have already taken this apart days ago to determine what you needed and taken the pics. To reshape metal you are going to need to have a vice to hold it or good pair of gloves to hold it along with files or a hacksaw and the files.

Quit talking it to death and go find out what you need. BFD if you pull the wheel twice, first time gives you the practice you need to do it faster the second time.

How did you get the handle of Greyhound? You drive one /work for them or fancy yourself a quick footed dog?

Send your disc to a place that can true it and drill it for smooth braking and better wet weather performance. Pony up to have Jeff send you a speedo drive plate you need... Or send him your disc to get a thinned drilled pair back along with your drive plate to be modified.

Your vintage bike has sucky brakes compared to any modern car with ABS so don't be following close or they will outbrake you... If you haven't already figured this out....

[Greyhound]

Thanks for chiming in… Could you point out any instance of where I’ve whined about anything?

I’ll just assume you’re bitter about soiling your panties when you forgot to put your tampon in this month.

Anyway, taking the wheel off, modding the speedo drive isn’t the problem, I’ve fabbed up enough parts/frame hoops, etc to be able to handle it. I don’t need help figuring out how to do it, or what tools I’d need, as much as getting an idea of what is actually involved.

As I’ve stated… I’ll be doing this one in the street, which aside from being cumbersome due to the proximity of the shop/Vice/tools I’d use, is also not allowed. My neighbors call and report, the city of SF loves towing vehicles. They take no mercy. We also have weekly street sweeper/cleaner, which is preceded by an army of meter maids who cite cars in its path (and tow vehicles which are either unregistered or undrivable).

I’m willing to take the chance, and take the heat from neighbors, but have pretty much one shot at it at getting it done, so was hoping to know exactly what it entails, so I can plan accordingly, and get it done in a timely manner.

I’ve also already reached out to Jeff.

Is that more clear for you, Mrs. RAFster?

[scottly]

For the sake of anyone else reading this in the future, would it be possible to show exactly how both need to get modified?

The style of drive with the two flat tabs that fit into the cover you have can be used on a hub with or without flats. My preferred way is to machine recesses into the back side of the rotor, and trim away the drive plate to fit.
 

[Greyhound]

Perfect. Thank you. Yes. This is exactly what I needed. Thanks!

[Greyhound]

So I’m thinking the notches can be done with a carving bit, and the drive plate maybe with a cutting wheel on a dremel or grinder?

[bryanj]

The problem with that method is you need the disc in a lathe to open the centre hole out accurately.
Have you looked at the file i pointed you at to see the shape of the one modified drive plate? The other type needs to be flat and the correct diameter to foi inside the disc so you can drill it plus drill and tap the hub to fasten the plate to it with countersunk set screws.
I have neither time, parts nor facilities to produce drawings for you

[Greyhound]

I received the file. Thanks so much for sending it. I responded to the email, but somehow it bounced back as “undeliverable” ?

The center of the disc needs to be opened up? In the photos, it looks like the center hole is the same size, only the notches are carved in, no?

Either way, it sounds like it shouldn’t be too crazy once it gets opened up.

[bryanj]

How can the disc that is a tight fit on the hub fit over a steel dish that goes over the same hub?

[robvangulik]

How can the disc that is a tight fit on the hub fit over a steel dish that goes over the same hub?

By taking the sides off of that steel dish, as shown in the pic a few posts back (that you probably can't see on your ****phone )

[robvangulik]

For my 400 I did it the easy way, the disc simply with a file and the dish with a hacksaw from the side. 15 years later still works a treat.

[bryanj]

But if you take the sides off the dish you loose the two tangs so why machine the back of the carrier, its far mor simple to modify the drive plate but you have to know which hub you have in order to know what to do, and there is naff all wrong with my phone its the US servers the pics are posted on! And why should i lay out a fortune to look at your pics when you dont listen anyway

[robvangulik]

Because if you could see the pics you would see that the tangs are still on. And I don't blame you or your phone, I try to explain things so you understand without seeing. I have dual disced maybe 6 or 7 Honda's over the years, I could show you several pictures, but as you can't see my Dutch pictures either I won't. Believe me, I do respect your knowledge as a former motorcycle mechanic, it's something I would have liked to have been myself, deep in my heart!

[bryanj]

I may be dumb but have stripped lots of wheels the dive plate has a flat disc that is formed to turn over the hub protrusion and fully enclose it, the drive tangs are formed at the bottom of this side wall so if you remove the side wall the tangs fall off. If you go to my details you will find my direct email, i would love to see a pic of this impossible, to my mind, engineering

[scottly]

Look closely at the pics I posted, Bryan.

[bryanj]

I have recieved pics direct and now understand how the mods were done.
Personally as the op wants to do this in the street i honestly believe that method to be too complicated.
When you look at the modified drive if you had carried on with the cut all the way round you would have a flat disc with the drive bits sticking up, this could the be fixed to the round nub by drilling and tapping and using countersunk screws(all hand tools) or cut with a hacksaw and bits bent using vice and hammer.
I was in my garage totaday and hopefully attachef should be pics of both round hub and one with flats so you know what to look for

[desertrefugee]

To be honest, dual stock discs on stock forks is wasted. The 550 forks aren’t strong enough to deal with the added brake pressure, and the stock brakes already suck badly enough that a single, more modern will outperform it.

These bikes don’t go fast enough under most riders to warrant dual discs, and if they are needed, dual stockers can easily overwhelm the forks and crappy suspension that you really aren’t deriving the benefit you believe you are.

This is kind of a bummer because I've been following this thread quite closely. I have a nice project 750 K5 and an extra disc, caliper and bracket. At some point, I'd planned on doing this modification as well. I can't imagine that it'll be for nothing since two discs is certainly better than one.  Although this commentary is a bit of an eye opener, I intend to press ahead with my conversion.  Maybe with the 750, there's a little more justification.

[Greyhound]

Forks aren’t strong enough to deal with the added pressure?

Perhaps not as strong as modern upside down forks, but certainly strong enough to handle twin discs, especially if coupled with a fork brace and lightened/thinned discs (almost half the weight less, bring it down almost to same weight as one disc).

After all, the CB750, which is a heavier bike, came with twin discs, and same diameter fork tubes (35mm).

Granted, no match for modern calipers/discs, but to say that it’s a complete waste is a stretch. Most of us aren’t trying to win any races, nor push these bikes to the limit anyway, so a second disc for me I think will be worth it, and much less costly than throwing in a modern front end.

[seanbarney41]

Greyhound, I do agree with you on this...but having done dual disks on my 750F0, even with thinned and drilled lightened rotors, the weight penalty is a high price to pay.  And you will lose that light, precise steering that is so good on the 550...

[scottly]

To be honest, dual stock discs on stock forks is wasted. The 550 forks aren’t strong enough to deal with the added brake pressure, and the stock brakes already suck badly enough that a single, more modern will outperform it.

These bikes don’t go fast enough under most riders to warrant dual discs, and if they are needed, dual stockers can easily overwhelm the forks and crappy suspension that you really aren’t deriving the benefit you believe you are.

This is kind of a bummer because I've been following this thread quite closely. I have a nice project 750 K5 and an extra disc, caliper and bracket. At some point, I'd planned on doing this modification as well. I can't imagine that it'll be for nothing since two discs is certainly better than one.  Although this commentary is a bit of an eye opener, I intend to press ahead with my conversion.  Maybe with the 750, there's a little more justification.

Your '79 CBX with factory dual discs also has 35mm fork tubes.
As far as not going "fast enough to warrant dual discs", even 25 MPH is #$%*ing fast when a little kid runs out from behind a parked car right in front of you.

[Greyhound]

Wow, is it really that noticeable? To a point where single disc is ultimately better overall?

I wish I could test drive a 550 with a dual disc, especially drilled/thinned to experience it.

So, does a modern fork set up (i.e. CBR1000) also weigh less than stock single or dual disc setup?

[desertrefugee]

As far as not going "fast enough to warrant dual discs", even 25 MPH is #$%*ing fast when a little kid runs out from behind a parked car right in front of you.

Exactly my point. At 25mph, you’re not stressing the suspension beyond what braking pressure you’re applying. Do it at 70mph and watch those forks curl under severe pressure.

I'm not sure I'll ever be hammering the front brake hard enough to curl the forks if I'm clipping along at 70. I suspect I'd have bigger things to worry about if that situation were to arise. I'll be pressing ahead with dual disc conversion - especially if Honda designers thought it was okay on the CBX!

[robvangulik]

especially if Honda designers thought it was okay on the CBX!

Honda started it themselves with the CR750 at Daytona, and that certainly wasn't pure for show!

[bryanj]

The 550 leg is designed with mounts so it must have been in Hondas ideas as the 500 wasnt.
Just been reading a well respected buileds post on the UK sit and he had problems getting the 2nd caliper parallel to the disc and had to alter the bosses on the slider to do it

[desertrefugee]

My application will be on a 750K5.   In this case and again, if Honda felt that an additional disc was prudent on the later SOHC-F models, why would it be any less so, or ill advised, on a K?

Once again, my intent is to proceed with this “upgrade” (dare I call it that?), given that I just happened to have parts on hand and didn’t seek them out.