Topic: Alternative CR - style rear drum brakes?

[fang]

Hi all, long time no see.
I am buying a new wheel set for the SOHC CB750. Going with Sun rims and stainless spokes+nipples. About $900+ from Buchanans if I lace it up myself.... Since they are cutting custom spokes and drilling the rims to fit, I figured this is as good time as any to change out the rear drum brake.

So why change the drum on a CB? Namely, this one is a pseudo CR750 race replica build, and the CR bikes had a big 240mm 2ls rear drum brake. I think the stock CB is about 178mm (and it sucks). Anyway, I have been shopping off and on for a CR rear hub for many years without success. I am not willing to drop $3600 for 3M Racing's "authentic" magnesium reproduction. Besides, for daily drivability practicality, I would prefer a "CR Style" drum made out of aluminum.

All that had been all but forgotten until earlier today when I almost bought the wheel set, only to remember the whole rear drum thing as I entered my card info at checkout.... LOL. So the purchase went on hold until I can sort out what I need to do with the rear hub.

Questions:
1. Does anyone know of a reasonably priced 2ls rear drum that could be an alternative, one in aluminum not mag. In all honesty, I cant even think of a machine with an aluminum 2ls rear hub assembly.
2. Another option I've considered but not really looked into is finding a 2ls front drum articulating plate and shoes that fit the CB750's rear hub/drum -- hopefully one with the speedo drive on the drum side. Any suggestions there?

CB750 rear brakes dimensions:
Width 39mm
Diameter 178.5mm
Axle 20mm

Granted a rear disc remains an easy and often desired option; I even have a Super Sport's rear spoked disc setup sitting in the workshop. But in my opinion, while the stock drum was not enough brake, the disc was too much brake for the CB. In all honesty, a 2ls rear brake might just be the perfect compromise. Plus, this one is a CR replica, so the aesthetic of the idea especially appeal to me. If it was good enough for Dick Mann, it hopefully will be good enough for me.

Thanks for the feedback/suggestions.

Peace and grease,
- Steve

EDIT:  crap -- http://forums.sohc4.net/index.php?topic=80460.0
You're already discussing this! 

After reading that thread I suspect that the more linear onset of dual trailing brakes might be the way to go. I know I have little intention of trying to delicately listento my toes in riding boots as I apply the brake.
-steve

[MidnightLamp]

I'll post up some equations tonight, as a baseline for the expected braking performance of a rear twin trailing shoe.

Cheers

[voxonda]

Hi there,

If there would be enough (serious) interest I think can make it happen for the Honda 180 rear.


cheers, Rob

[fang]

Rob,
There is a difference between "serious" interest and ready to pay big bucks interest.  Can you share your thoughts -- I'm real interested.  However at this time I am looking for information with the intent to do my own machining.  Right now I am just trying to figure out what all is out there.

I think I would have no problem machining a 2ls brake plate to switch it left to right; to switch it from 'dual leading shoe' to 'dual trailing shoe,' or vise versa. 

Is the CB180 brake plate a correct fit for the stock CB rear hub?

-Steve

[voxonda]

Steve,

Like with the dry clutch that is under heavy development, I would want to know if and how much interest there is for a alternative to the very(!!!) expensive CR replica rear drum. Although I feel if you want to make a real replica, then go for it. I think there is a demand for something affordable. I found a CB450 rear drum, also 180 mm, which has the same type of rear sprocket mount as the CR drum. Only the dia of circlip and pitch circle of the 4 sprocket mounts are smaller. The brakeplate would not be milled or turned but cast like on the picture.

Cheers, Rob

[Ricky_Racer]

IMHO opinion, Rob, it's a good idea depending on the cost of casting and machining. Obviously the casting mold is already finished, as well as (I'm assuming) the milling/drilling jig; looks like the expensive development cost is already completed. So, it's gonna come down to the cost of production plus profit. I would think you could find a willing market for this good-looking brake plate, in our market, at a fair price.

I hope you do it. I'll be in for at least one, depending on the affordability. All the best. RR

[Ricky_Racer]

BTW, Rob, if I found someone who could cost-effectively make Ceriani lookalike side plates for a Suzuki 4LS brake, I'd be really stoked!  Hint, hint...   RR

[voxonda]

Still a far cry from that, Ted. The picture is of a 160 dia rear brakeplate for a Grimeca drum. Also a 200 mm for a Benelli drum. But no 180's.(yet) Just checking if there is interest. Casting mold has to be made also machining, but it could be done at a reasonable price but off course depending on numbers.

Cheers, Rob

[Ricky_Racer]

Well that bites, Rob! I figured you had a buddy who'd already spent the money and you could just knock these out. I guess I'm not as optimistic now since I know how much it costs (at least on this side of the Atlantic!) to make the wooden form for the sandcaster.

Any of us who consider manufacturing a product have to take a calculated risk, and I just don't see this one paying off if the development cost is significent.  And so it goes.... {sigh}    

Now on the other hand, those Ceriani/GT750 parts... well...    RR

[MidnightLamp]

What about utilizing the enfield TLS plate in a CB750 drum? The enfield brakes are $70, new with shoes...! 

http://forums.sohc4.net/index.php?topic=80460.0

[fang]

Do you have a good source for buying one of these Enfield brake plates for experimentation?

[Phil]

If there is sufficient interest, it is probably feasible to CNC mill a 2LS backplate to fit a stock CB750 drum, isn't it Voxonda? My problem with this is that the stock CB750 drum is so heavy.

[voxonda]

Hey Phil,

If sufficient interest even casting comes in play. Weight stays an issue if using the oem drum. But................it stays in one piece in contrast to some competitors.
If weight is real issue, the only way to go is disk.

Rob

[lordmoonpie]

Anyone who wants a similar brake to the CRs, I can get the following for £1250 plus postage. It's not cheap but it is a third of the price of a CR750 hub. This is a RC181 replica hub and it's pretty gorgeous. It's 200mm diameter, made of electron and has a 17mm spindle diameter. It takes 36 spokes and weighs 5kg. The hub is complete with brake shoes and arms as you see here.

I'm runnig one of these on my RC162 replica but could be a nice unique looking option for some CR builders who can't stratch tp the £3600 for a CR hub.

[fang]

My Lord,
Thanks for the heads up on your inside track on your source for hubs.  For blokes here in the states, our own KOS at M3 racing also sells new, reproduction rear brakes in Magnesium for $3500.00.





£1250 = about $2000 USD
£3600 = about $5787 UDS

M3's hub = $3500 = about £2177

I am hoping to spend something in the price range of less than $500 for whatever I end up doing with my rear hub.  But I just now pulled that dollar amount out of my arse.  I guess i might rise to the occasion for 'just the right thing', but all in all $500 is a lot of money to spend on eye candy, since when it is all said and done the rear does not need that kind of stopping power.  I mean, I have a "F" rear disc setup sitting in my workshop which I could use for free which would probably out perform all these discs.  And since I don't race, I have no constrictions requiring the use of a drum. 

For me, when I'm being honest, this is all about performance racing aesthetics.  Now it is just a question of what I am willing and capable of spending.  A $2000+ drum brake is more than most of our forum members have spent on their entire bikes.

peace and grease,
Fang