Topic: cb550 front end swap questions

[squirley]

Ok, so here's a couple questions for you well rounded people.  I am putting together a cb550 cafe racer comprised of the following.  It has 19" rims front and back measuring 2.5" and 3" wide respectivley.  Cb 750 swingarm to compensate for the larger diamter rim.  For the fron, I have put a gsxr frontend on it from an 02 gixxer.  Everything went together very well; however, I left the tackling of the brakes for last.  I began looking into them recently as I need to get this project off the ground. 
The kicker is that I am retaining a spoked rim and need to find a way to attach  dual 320mm discs to the wheel.  Right now, the bike is fully functional and rolling, I just need to find a way to attach rotors before I tear it down for paint. 
As I said, the front end is a 2002 gsxr, holding a harley dual disc hub that I pressed in some 25mm I.D. bearings to match the gsxr axle.  You may ask why a harley hub? Well, I have aluminum excel rims for for a harley that I will be using front and rear, and everything fits great as the bearings were a straight swap and the width is nice.  But here in lies my problem.  I am doing this on a budget and am looking for the best option for the money, so here are my options. 

1)  Harley makes a full floating rotor that is 320mm diameter which would be a direct bolt up to a my harley hub.  You may say, well, go for that obviously...however, these discs are quite expensive, actually very expensive and a little too "bling" for my taste.  Also, I don't know how well the 6 pot gsxr calipers would adapt to them.  In the end, I would be paying big money for a bolt on rotor that has a chance of not working.

2)  I have heard that ducati snowflake rotors, which are 320mm, will bolt directly to some japanese hubs.  I think it is maybe an RD, but am not sure. If anyone knows, please let me know.  If I could find out which hub this pertains to, I would just bolt on the rotors and machine out the hub to accept some sealed bearings and go from there.  In the end, I don't know if I could lace up the harley excel wheel to this hub, and I don't know which exact hub is a direct bolt up to the snowflake rotor.

3)  I could machine some new rotor carriers with a harley lug pattern and then  re-rivet them to the suzuki outer rotor.  In the end, this will be very expensive and time consuming.  I am not against taking the time to machine the carriers, but the rivets would turn this into a high dolar option. 

4)  I could just run harley rotors that are 292mm in diameter, and then try to find a way to bring in the calipers to decrease the overall outside diameter to match.  The problem here is that as of now the calipers are very close the the spoked rim on each side, having no more than 5mm clearance each side.  The closer I bring them down, the closer they come to contacting the spokes.
 
The gsxr rotor is 5 lug, same as the harley. Unfortunatley, the bolt pattern is larger in diamter, and there is not enough material on the rotor to drill in some holes for the halrley pattern as the inside diamter of the bearing hole is just too large.
So here is where I sit, undecided.  If anyone has any info/input to add, as long as you don't tell me to just run a gixxer front rim, please feel free to chime in.  Any help is greatly appreciated.
Also, if anyone knows of a sport or super bike rotor that that has a small inside diamter, please let me know, a harley's measures around 2.25 inches, so anything withing range of here is great.  Thanks all, and I will do my best to post some pics, as I know this thread may sound worthless without pics.
Jens   

[bryanj]

Back in the 70's in UK you could buy cast irom replacement rotors and all you did was drill out the rivets and use small HT bolts with nylocks
Does away with the expense of rivets

[754]

Re #3,

Machine the disc carriers and forget the rivets.. bolt them on and use locktite.

Re #5, the one after #4,

Make spacers to fit the rotor ID and to fit close to the hub register lip (sometimes you need to leave a tiny rib or ledge on the spacer that fits within the small chamfer on the back of the ID of the rotor.. this prevents it from falling out) Then slot the holes or redrill(rotary table is best), get a good fit. This should work except if the rotor center used countersunk fasteners or similar.

I have been doing a lot of this for the last 19 yrs, I can usually tell you a way of getting through it.

[Jinxracing]

As 754 said, one option would be to machine new carriers since it sounds like you've already got a set of rotors in your hands. However, I would absolutely not use bolts in place of the rivets. The shear loading is pretty heavy on those puppies, and frankly, I wouldn't feel comfortable trusting my life to a bolt where a rivet was originally called for. I'm sure people have done it in the past and lived to tell the tale, but that's up to you. Rather than use rivets, would it be possible to machine up some plugs out of drill rod and then harden/temper them? Seems it wouldn't be too hard to then add a threaded fastener on each side to act as a "keeper". Still kind of complex though...

I think if I were in your shoes I'd head down to my local motorcycle dealer(s) and salvage yards with some calipers and start measuring rotors for a stock set that more closely fits your needs. Once you find a likely candidate, eBay's got tons of stock rotors for sale CHEAP by people upgrading to aftermarket racy rotors, (especially the Honda CBR 600 F series)

Good luck and keep us posted!

[squirley]

Thanks for the replies, it is much appreciated.
I did give a long hard look at replacing the rivets with bolts, and the plan was to make the nuts from magnets so I could run a speedo drive off them.  I have heard many people run bolts and never have a problem, but as of now, I am not totaly convinced I want to do this.
As for the discs, they are 320mm.  Gsxr 1000 used these big guys up to 2002. In 2003 they changed to radial mounted brakes, and reduced the size to 310mm. (Correct me if I am wrong)
I have also given thought to making an adaptor plate.  Right now, I machined off about .080" on each side of the harley hub; if I can find a way to mount the brakes now, they will match up perfectly with the calipers.  I can't really afford to go any narrower on the hub to machine a adaptor that way. My question is, could I do something like the following?  If I machine a donut shape that fits over the harley I.D. hole, and is maybe say .5"-1" larger than the I.D. of the gsxr rotor. This circle plate will be drilled for the harley lug pattern and will act like a big clamp to help retain the gsxr rotor. I could either slot the gsxr rotors or redrill a 5 bolt pattern in it with a smaller diamter and clamp it down between the harley hub and new plate.  Thus I get to keep the original, readily available rotor, and the correct spacing.  The whole point of the plate is becuase if I redrill the gsxr caliper, there will only be about .030" of material left between the lug pattern and the I.D. of the gsxr caliper, and maybe it would be sufficient if the rotor was "clamped" all the way around it's inner diameter.  I will draw this up on solidworks hopefully soon so I can give you guys a better idea.  Worse comes to worse, I could add some stainless steed press dowels into the plate and drill the rotor so it couldn'e spin.

[FunJimmy]

I was faced with a simular issue and solved it this way.

http://forums.sohc4.net/index.php?topic=27159.0

Good Luck
FJ

[dusterdude]

Harleys are mounted in the trans.

not since the early 70`s,especially on superglide and sporty front ends.

[754]

It hard to say without seeing the parts.

Sometimes if there is room you can mount a plate to the hub with original pattern using countersunk bolts then put the pattern of the new disc between those holes.. if you have room.

I dont think rivets are required, the disc will warp then rather than move a bit.. must be a reason they went to floaters.

Dont try to weld up the holes on an aluminum disc carrier to redrill the holes, I have a nice set of dished Kawi ones here! After the guy welded them the 4  or 5mm thick carrier had about 2 or 3mm of dish to it..!!

[squirley]

Yes dgfischer, this is what I am heading towards.  If I redrill the gsxr hub for a harley pattern, there will only be 30 thousandths of material between the new holes and the  inner diamter.  This, to me, is not enough, so the new adaptor will help secure the gsxr rotor by supporting it with an inner lip, and pressing it against the hub to help with stand the radial torque that may want to tear open the thin wall of the gsxr rotor.  Does this make sense?

754, I really don't have the room to make an adaptor, if I was using 5/16 allen bolts, I would have to counter bore down about .3 inches, the plate would probably have to be close to .45" thick.  I only have about another.15" that I could machine off each side.
As for the welding the holes, I wasn't going to as it would get me no where; I did, however, think about tiging in a inner plate inside the gsxr rotor that would match the harley hub diameter.

[754]

No need to TIG

 I tried to explain.. make a press fit insert but leave a small lip same angle as the back chamfer on the disc ID, then the small lip hidden by the chamfer will prevent it from pulling out. Increse back chamfer if need be.

If you have .03 meat left and you clamp with a washer or a ring it could work.. if the assembly is close fitting and clamped down it really has nowhere to go.  Think an XR Harley with Barnes or Kosman wheels.. only thing holding sprocket and disc is 4 allen bolt heads and the knockoff nut keeps the disc/sprocket from moving.

Or a car,  5.. 7/16 bolts holding how much weight and side loading on a rim that actually flexes??

[squirley]

The new style harley hubs have extruded slots on the hub, so redrilling it for another pattern is not an option.

The lip would be thin around the rotor, but only in locations of the holes, the rest of the rotor inner diameter perimeter would be as thick as usual

754, I understand what you are saying about a chamfered spacer, but am a little confused on what it would do for me.  Sure I could get it to support the larger inner diameter of the suzuki rotor, which itself would be supported by the harley hub.  The spacer would not be able to slip out because of the chamfer, correct, but how does this help me to obtain a different bolt pattern or remain with the harley pattern?

Ok, this thread has become officially confusing without any pics.  I drew it up in solidworks, but am trying to find away to attach a jpeg.

[squirley]

Ok do here is what a harley hub looks like, the reason why I can't just drill new holes

[squirley]

This is along the lines of the type of sandwhich adaptor that I have machined.

[squirley]

From the side, you can see that there is about 4mm clearnace between the two where the rotor would be sandwiched and bolted with the adaptor.  I did not have time to make the rotor, and I need to get measurements for it, so this is just for a temporary idea.