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Author Topic: Convert disc to drum brake  (Read 410 times)

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Offline Markagnew

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Convert disc to drum brake
« on: November 04, 2018, 09:19:49 am »
Maybe a strange question as I am fully aware disk is marginally better than drum, however I have a cb750 f1 supersport and love the drum brake look... how easy is the change over and what do I need? Thanks guys, first post so please be gentle 😂

Offline 69cb750

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Re: Convert disc to drum brake
« Reply #1 on: November 04, 2018, 10:58:13 am »
Quote
I am fully aware disk is marginally better than drum
Are you familiar with Darwin's theory of evolution ?
You are tempting fate and may be a victim if you do this, the disk has twice or more stooping power then a drum, that why it is there.

Offline 754

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Re: Convert disc to drum brake
« Reply #2 on: November 04, 2018, 11:05:33 am »
 :markagnew, do you mean front, back or both ?
 Not twice the power but it has advantages.
 Both can lock up the rear wheel , can the disc lock it up with half the effort ?
 I think big advantage is less fade with a disc.
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Offline jaytee-nz

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Re: Convert disc to drum brake
« Reply #3 on: November 04, 2018, 11:14:23 am »
"Are you familiar with Darwin's theory of evolution ?"
That's kind of rich coming from someone who rides without any protective gear as per your Route 66 post !


Offline madmtnmotors

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Re: Convert disc to drum brake
« Reply #4 on: November 04, 2018, 11:18:03 am »
Are you familiar with Darwin's theory of evolution ?

Careful now... the last time I made that reference the member got all bowed up and took his ball and left!  :o


It could probably be done, but there are a number of hurdles:
>The rear disk brake stay bracket is on top of the swingarm, while the drum stay bracket (K models) is on bottom. You could weld a bracket to the underside of the current swingarm or source a K swingarm. You'll need the drum brake hub (or the whole wheel) as well.
>The F disk brake lever is different than the K drum brake lever. I do not know if these are a direct swap.
>If you overcome the difference in the brake levers you'll also need the rear brake stay arm and the link arm from the brake lever to the arm on the rear brake plate. You made need the drum brake lever spring as well.

EZPZ  8)
TAMTF...


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Online seanbarney41

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Re: Convert disc to drum brake
« Reply #5 on: November 04, 2018, 11:31:22 am »
first, op never mentioned whether he was talking about front or rear...if rear, why not just get yourself a k instead of an f
If it works good, it looks good...

Offline madmtnmotors

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Re: Convert disc to drum brake
« Reply #6 on: November 04, 2018, 11:37:04 am »
first, op never mentioned whether he was talking about front or rear...if rear, why not just get yourself a k instead of an f

Since they all had front disk brakes I thought it was clearly implied  ;) that the rear brake was being referenced...
TAMTF...


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My most recent project "Evolution": http://forums.sohc4.net/index.php?topic=100352.0
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Clean up that nasty harness: http://forums.sohc4.net/index.php?topic=137351.msg1549191#msg1549191
                                           http://forums.sohc4.net/index.php/topic,148188.msg1688494.html#msg1688494
                                           http://forums.sohc4.net/index.php/topic,139544.msg1579364.html#msg1579364
                                           http://oldmanhonda.com/MC/wiring750K1.html
Charging system diagnosis: http://forums.sohc4.net/index.php?topic=1012.msg8345#msg8345
Get the manuals: http://manuals.sohc4.net/cb750k/
The Dragon: http://forums.sohc4.net/index.php?topic=45183.msg1571675#msg1571675
Headlight Switch: http://forums.sohc4.net/index.php?topic=113986.msg1283236#msg1283236
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Engine Lifting Made Easy: http://forums.sohc4.net/index.php/topic,58210.msg1684742.html#msg1684742
                                      http://forums.sohc4.net/index.php/topic,100352.msg1675840.html#msg1675840
Static and Dynamic Timing: http://www.hondachopper.com/garage/carb_info/timing/timing1.html
Airbox Gasket Replacement: http://forums.sohc4.net/index.php/topic,114485.msg1290000.html#msg1290000
"Café" : http://forums.sohc4.net/index.php/topic,84697.msg953814.html#msg953814
PD Carb Choke Linkage: http://forums.sohc4.net/index.php/topic,100352.msg1669248.html#msg1669248
                                    http://forums.sohc4.net/index.php/topic,110931.msg1248354.html#msg1248354
Follow up on your damn posts: http://forums.sohc4.net/index.php/topic,144305.msg1791605.html#msg1791605
Taiwanese Cam Chain Tensioners:  http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841
Gumtwo Seat Cover: http://forums.sohc4.net/index.php/topic,164440.msg1897366.html#msg1897366
Primary Drive: http://forums.sohc4.net/index.php/topic,166063.msg1919278.html#msg1919278
Tank Latch: http://forums.sohc4.net/index.php/topic,165975.msg1919495.html#msg1919495
Shorten your forks: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-shorten-forks-td4042465.html DO NOT CUT THE SPRINGS!
Clutch How To: http://vintage-and-classic-honda-s.456789.n3.nabble.com/How-to-change-and-adjust-a-clutch-SOHC-td4040391.html
Sent from my Tandy TRS-80!

Offline bryanj

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Re: Convert disc to drum brake
« Reply #7 on: November 04, 2018, 11:42:50 am »
If you insist on stopping slower and hitting things you need a 450 twin complete front end
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Offline Don R

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Re: Convert disc to drum brake
« Reply #8 on: November 04, 2018, 12:13:50 pm »
 Agreed, get an early K and a 450 drum brake front end.  Or an early drum brake 450 as a second bike.  A Black bomber is the best idea.
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Online seanbarney41

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Re: Convert disc to drum brake
« Reply #9 on: November 04, 2018, 01:08:54 pm »
If you insist on stopping slower and hitting things you need a 450 twin complete front end
that would do it...although imo, the stock disc brake set up is quite capable at stopping slow and hitting things already lol
If it works good, it looks good...

Offline Markagnew

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Re: Convert disc to drum brake
« Reply #10 on: November 04, 2018, 01:11:44 pm »
Sorry I am talking about the rear brake only! Main reason for not getting a K over my F is about £5000 difference!

Offline MikeSimon

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Re: Convert disc to drum brake
« Reply #11 on: November 04, 2018, 01:40:31 pm »
It shouldn't be too difficult to do the rear. You have to find the right parts. Wheel, brake, torque arm linkage and brake pedal.

I saw a guy one time at Vintage Days who had converted the front disc brake to drum on his 89 Honda GB500, because he liked the looks of a massive Fontana front brake...
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Offline 754

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Re: Convert disc to drum brake
« Reply #12 on: November 04, 2018, 08:12:12 pm »
Mark you can probably  do a wheel   swingarm, and other parts swap if you cant find parts for a reasonable price.
 Then you need to weld the bushing to your frame.
 Hope you don't want to run your alloy plates..
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My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

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Offline turkey4me

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Re: Convert disc to drum brake
« Reply #13 on: November 05, 2018, 05:08:58 am »
Once you source a K rear hub, you'll need a 10 mm off set sprocket for chain alignment.   You will not be able to run a chain guard. Then you will need to weld a new brake tab on the foot pedal cam to get any leverage. Stopping power is quite poor.   I would not recommend it unless you have dual brakes up front.  I never use my rear brake.  It's really just a last resort if the front ever fails.

Offline lrutt

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Re: Convert disc to drum brake
« Reply #14 on: November 05, 2018, 05:42:01 am »
A well setup 4LS front will put you on your nose. As for drum rear, no big deal as both disk and drum will easily lock the wheel. I'd love to have a 4LS front either from a Suz, Guzz, or Benelli. Or better yet, a rare Fontana 8LS.
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Offline 70CB750

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Re: Convert disc to drum brake
« Reply #15 on: November 05, 2018, 06:39:51 am »
I saw front wheel converted to drum on CB750 at Barber.

Offline slikwilli420

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Re: Convert disc to drum brake
« Reply #16 on: November 05, 2018, 06:48:06 am »
I never got the front drum conversion thing. Its such a quantum leap backwards. They are heavy and reduce the compliance of the suspension. You score points for looks, but a well set up front end with period iron discs and AP calipers looks even better and stops far better as well. In the day before there were good disc options, then OK, but now you can have better period stopping performance for similar money. Suzuki hubs aren't falling from the sky and the rest are far more expensive than that.

As to the rear, both the stock drum and disc were tremendously overpowered for the task, easily locking the rear wheel. The best rear brake is one you can all but stomp on and not lock the rear wheel. Realistically there is no reason to even use the rear brake, especially on the street unless you are a very aggressive rider and ride to the edge of the bikes ability.
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Offline Don R

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Re: Convert disc to drum brake
« Reply #17 on: November 05, 2018, 07:17:56 am »
 I'd think there are a few K owners that would happily swap out a drum setup for a disc setup. Look for that guy. You might even get a couple bucks to boot!
 My dream bike has triple discs but that's just me lol.
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Offline PeWe

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Re: Convert disc to drum brake
« Reply #18 on: November 05, 2018, 08:58:25 am »
Rear disc diameter usually really huge on the CB750 F bikes.

Rear brake useful when riding very slow before redlights and parking areas. High speed not much help, risk to lock the rear wheel.
I have only the old good drum!

My friend’s Honda Super Blackbird apply rear brake automatically when using hand brake.
« Last Edit: November 05, 2018, 09:58:09 am by PeWe »
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Offline robvangulik

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Re: Convert disc to drum brake
« Reply #19 on: November 05, 2018, 09:51:35 am »

My friend’s Honda Super Blackbird apply rear brake automatically when using hand brake.
That is to assist all those people who never learnt to ride their bikes the proper way, hairpins in the mountains wouldn't be rideable  without a rearbrake, going up as well as down, and like you wrote, in city traffic as well. If it wasn't useful, manufacturers would have deleted it long ago!

Offline PeWe

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Re: Convert disc to drum brake
« Reply #20 on: November 05, 2018, 10:06:47 am »
That bike have rear brake to be used separate too ;D
When you mention it....
I live in a flat area but I remember bike holidays thru Austria to Jugoslavia and Italy. Plus one holiday via France to Andorra for a week then the mountain roads passing Barcelona.
Some small steep roads had very sharp corners. Just got it thrown into my face! :) Yes, rear brake is useful when keeping the bike while twisting throttle, sliding clutch and rear brake at almost at the same time, hand brake not possible then.
« Last Edit: November 05, 2018, 10:08:18 am by PeWe »
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Offline MikeSimon

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Re: Convert disc to drum brake
« Reply #21 on: November 05, 2018, 12:58:54 pm »
Friend of mine who is used to ride Harleys, visited from out of State and I had him ride my R1100RT. he pointed out that I must have a problem with the rear brake, because he thought it didn't work properly. I checked it and it was fine.
Rear brake comes in handy when you stop at a light at an incline and you want to keep the bike from rolling back.
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Offline robvangulik

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Re: Convert disc to drum brake
« Reply #22 on: November 05, 2018, 05:05:32 pm »
Friend of mine who is used to ride Harleys, visited from out of State and I had him ride my R1100RT. he pointed out that I must have a problem with the rear brake, because he thought it didn't work properly. I checked it and it was fine.
Rear brake comes in handy when you stop at a light at an incline and you want to keep the bike from rolling back.
Simply difference in weight distribution! :D

Offline BomberMann650

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Re: Convert disc to drum brake
« Reply #23 on: November 06, 2018, 01:41:56 am »
No use for the rear brake?  :o

You guys been sippin the macallan no.4 tonight?

Proportional braking is a good thing. 
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Offline 754

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Re: Convert disc to drum brake
« Reply #24 on: November 06, 2018, 07:20:20 pm »
How about one of these ?
 A bit over the top perhaps....
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline blacksmith1

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Re: Convert disc to drum brake
« Reply #25 on: November 07, 2018, 01:36:50 am »
love drums,old world thing,fontana,tz350 four leaders ,just put a 71 bsa on the front of mine,certainly wont pull up as quick but this is not going on the road,do what you feel

 

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