Topic: 750 dual disc vs. 550 dual disc

[DH]

As we all know, dual disc conversions are cool, and when done correctly, improve the braking ability of our bikes.
Thinking about this for a while before doing it to my 750 (K5). My question to those who have done it, is there any advantage or disadvantage (On a 750) to use 550 components from  the same time period?. Obviously there would not be the pad contact area that 750 rotors and pads
would provide. But using 550 calipers/rotors/pads would provide a fair amount of weight savings over the bigger 750 compo
nents. And the pad contact area total with dual 550 rotors is still more than a single 750 front brake (theoretically) yes?
My 750 has the 341 lower fork legs, which allows the use of either style front disc brake. What are you folks' thoughts?
I know the master cyl would need to be updated. If I went this route, I'd want to retain the stock look as much as possible.
Thanks for any suggestions.

[Powderman]

My personal opinion on weight and brakes is I would rather have the added benefit of the safety in braking performance than the loss of handling performance I may not even notice in the weight savings of a few parts.

[MiGhost]

Here is the problem. While the calipers, and rotors will bolt up. There is a difference in mounting location on the forks due to the size of the rotors. Not only will you lose contact area due to rotor size. This is compounded by the caliper being moved away from the rotor.

Check the axle to caliper distance.

[DH]

Here is the problem. While the calipers, and rotors will bolt up. There is a difference in mounting location on the forks due to the size of the rotors. Not only will you lose contact area due to rotor size. This is compounded by the caliper being moved away from the rotor.

Check the axle to caliper distance.

Axle and caliper distance should be the same as a 550 K0,1,2..as they use the same 750 lowers, but the caliper brackets are angled differently to accomodate the smaller diameter rotor. The front wheel on the 750 is the same as the 550 as well. Front fenders are the same. The fork lowers are stamped "341"on the wheel side (inner edge). I'm only considering this if it'll get me more brake than just a single disc would. If it does, the weight savings would be a bonus. I was wondering if anyone has done  or tried it, and was it worth it? or just a big waste of time..

[Puntas13]

Just save yourself the money and buy another 750 caliper and rotor. I kept my stock MC when i added a dual disk and it works great.

[scottly]

Thinned 750 rotors are lighter than stock 550 rotors, and lighter rotors from other bikes can be adapted as well. 1+ for using a stock MC with dual 38mm calipers.

[seanbarney41]

The difference in size and weight is too small to be of any significance.  I'd stick with the 750 stuff.  If you want light, go with thinned and drilled rotors as Scottly says, or different brakes altogether...

[SOHC4 Cafe Racer Fan]

The difference in size and weight is too small to be of any significance.  I'd stick with the 750 stuff.  If you want light, go with thinned and drilled rotors as Scottly says, or different brakes altogether...

++++1 says the brake lover

[Don R]

+2 it's hard to have too much brakes

[Oldtech]

Did it on my 550. Made a huge difference.

[DH]

I have most of the components to go either way, but seems like the consensus is the dual 750 route is the way to go.
One thing i forgot to factor in is the 750 rotor, by virtue of its larger diameter should stop the wheel easier.
It's not just ALL about pad area. Dual discs with 550 components would obviously be better on the smaller lighter 550.
Hmm.....I learned something.....I think?.....


(oldtech, that 550 set up is very nicely done)

Puntas13,  how does lever height/feel compare to the stock single set up?

And to anyone: How much do they typically take off the rotor when thinning? Does it affect lever feel and height?
Is it advantageous to go with a different master cyl? Or is every situation different?
Thanks to everyone for the input so far

[Powderman]

I have most of the components to go either way, but seems like the consensus is the dual 750 route is the way to go.
One thing i forgot to factor in is the 750 rotor, by virtue of its larger diameter should stop the wheel easier.
It's not just ALL about pad area. Dual discs with 550 components would obviously be better on the smaller lighter 550.
Hmm.....I learned something.....I think?.....

(oldtech, that 550 set up is very nicely done)

Puntas13,  how does lever height/feel compare to the stock single set up?

And to anyone: How much do they typically take off the rotor when thinning? Does it affect lever feel and height?
Is it advantageous to go with a different master cyl? Or is every situation different?
Thanks to everyone for the input so far

The thickness of the rotor should have no difference in lever feel or height/travel. Rotor thinning is the same effect as thinner pads. MC choice is personal but when going to a dual disc with a single disc the MC may not give enough pressure to adequately stop the bike.

[SOHC4 Cafe Racer Fan]

I thinned my rotors via Goddfrey and upgraded to a radial MC.

[scottly]

Is it advantageous to go with a different master cyl?

Hundreds, if not thousands, of dual disc conversions have been done with stock 14mm master cylinders. The larger the MC, the less hydraulic pressure for a given pressure applied to the hand-lever.

[DH]

 Anyone specific in the U.S. who does machine and drill service?

[DH]

Is it advantageous to go with a different master cyl?

Hundreds, if not thousands, of dual disc conversions have been done with stock 14mm master cylinders. The larger the MC, the less hydraulic pressure for a given pressure applied to the hand-lever.

Thanks scottly. I've heard all kinds of stuff regarding master cyl capicity. Still haven't wrapped my mind around it all yet,
but would like to keep my original master cyl if at all possible, so that's a good thing.

[SOHC4 Cafe Racer Fan]

Anyone specific in the U.S. who does machine and drill service?

Goddfrey - forums member.

[b5rider]

Anyone specific in the U.S. who does machine and drill service?

Goddfrey - forums member.

+1 on Goddfrey. I have his thinned and drilled rotor on my 550 and it works great with the added weight of a sidecar. It came that way, so I don't really have a reference except my other 550 without a sidecar with the stock rotor

[DH]

Thanks for the information folks. I'm gonna go the 750 route I think, and appreciate the useful information from both
perspectives.  One last thing tho, Are there any preferred type of bolts you all use for the rotors?

[Tetter]

I have used standard bolts, and cut these to the correct lenght, no problems yet 

I would be curious though how 550 stuff would have worked out, as mounting left 750 parts on the reight side already gave enough troubles to have this shimmed out correct in my case.

Looks pretty though, and braking really improved. Feels almost as good as a modern bike now.

[DH]

I have 5/16 diameter sae bolts,that seem to be nearly, if not identical to the 8 mm ones, just longer. I'm guessing they will work?
Not looking forward to shimming on the right side. But it is what it is. Nice lookin bike btw.

[Powderman]

You guys are using SAE bolts in holes that are threaded for metric, really?

[Powderman]

Thanks for the information folks. I'm gonna go the 750 route I think, and appreciate the useful information from both
perspectives.  One last thing tho, Are there any preferred type of bolts you all use for the rotors?

Find the correct factory bolts that go with the rotor. Yes the are a preferred type and designed for the application.

[flybox1]

DH
please read this thread, start to finish.  http://forums.sohc4.net/index.php/topic,53532.0.html
On pg 3, I've listed all the hardware needed for my conversion. 
Its K8 frame, but I used K1 front end components.

[seanbarney41]

You guys are using SAE bolts in holes that are threaded for metric, really?

the holes are not threaded, the rotor bolts are through bolts with nuts...still I would not want 5/16 sloppin' around in 8mm hole.  Might be able to source Gl1000 rotor bolts but I don't know if they are still available from Honda, maybe find 'em on ebay?  They would be the perfect fit.