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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: twowheeledgator on November 09, 2018, 02:31:04 PM
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I imagine it is as simple as finding a rear end with disk and swapping?
Has anyone tried this? Suggestions?
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Much more involved than that. You will need: brake pedal, master cylinder, brake fluid reservoir, caliper, brake pads, brake lines, and a rear wheel. This is just off the top of my head. A closer look at the parts fiche is warranted.
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I would think if you could find a donor bike it would be a matter of swapping parts. Ebay has a huge selection or rear ends and such, but I'd hate to sift through all that to find a good one. The drum is actually pretty effective when set up right, not sure it's worth the trouble to swap everything out.
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In normal riding I very rarely use the rear brake. Mostly I only use the rear for emergency braking and in gravel or sand.
Regards Martin.
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I imagine it is as simple as finding a rear end with disk and swapping? Suggestions?
Imagination lets us down again. :giggles
As Chaos implies, if the drum is within spec, renew the shoes and the cable. Check for worn linkage. Otherwise, you'll need to be gathering the parts mentioned by Chaos and mw074 for conversion to disc brakes.
I suggest restoring what you have. Parts are still available. As Martin suggests, you'll be ok. Think of your forebears navigating the Alps before the advent of disc brakes. Most of them lived, probably. :2thumbup:
From the Haynes K75/K100 manual:
(http://www.motobrick.com/gallery/1/1601-101118151658.png)
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This is my sons bike and he has never ridden with drums. He is also young and has more energy and time than he knows what to do with. When we were talking about disk I know some models sold with disk. So I was wondering if it was even possible to replace the rear shaft housing and back of a disk. I am pretty sure I have enough other things to do than take on a project like this but now I am curious. Curious if can even bolt up.
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I am pretty sure I have enough other things to do than take on a project like this but now I am curious. Curious if can even bolt up.
Riding with a drum brake isn't going to matter to the average rider, especially in Florida, unless it involves a speed record descent of Broward's Mount Trashmore.
As far as disc assembly bolt up to a drum brake final drive is concerned—not happening. The first image shows a drum brake final drive housing. The second image shows a disc brake final drive housing with caliper mounts as part of the case, indicated by arrows.
(http://www.motobrick.com/gallery/1/1601-101118162525.jpeg)
(http://www.motobrick.com/gallery/1/1601-101118162701.png)
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So it looks like the disk FD will theoretically bolt right up to my shaft housing?
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Housing, wheel, calipers, disc, rear master and pedal, switch, I'm sure there's some more miscellaneous parts. You may be able to recoup some cost by selling the drum wheel, they are rare and getting rarer. But that money could be better spent on new front brake lines, fuel lines, tires, beer, fishing gear.........
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Did someone say Beer?
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Did someone say Beer?
I heard Succinylcholine.
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My happy place is rum. Have a bottle of 7 year from Cuba I just need an occasion to crack open.
My son takes after his old man. When I was his age I had a Plymouth Duster with a slant six and all I wanted to do was turn wrenches on it every night. Thank heavens a Bronco II crashed into it before I could locate a 340.
He is also at Motorce Mechanics Institute in Orlando so EVERY Motorcycle is a project waiting to happen.
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I tell my wife worse things could happen, he could be on crack.
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My happy place is rum. Have a bottle of 7 year from Cuba I just need an occasion to crack open.
The fact that you have it is reason enough to crack it open.
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I went through two bottles with that reasoning.
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To return to the topic. A few years ago, I was seriously converting my K75RT from rear disc to drum because of the problems I was having with the rear master cylinder. My personal experience with three bricks is that the rear master cylinder is a piece of crap and if I had a drum brake on the rear I wouldn't think of changing it.
Although I have never ridden a brick with a rear drum, I really can't see where the braking is that much better with a rear disc.
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Although the drum brake is adequate, I have found the disc brake to be superior.
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No big difference. The rear brake shouldn't need be used below 20 MPH (30 KPH), IMHO anyway. Maybe some will expound about trail-braking in corners but that's a whole different soapbox discussion. :popcorm
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greetings...
gotts to trailbrake for maximum yeeeeehaaaaa... gotts to enter hawt... trailbrake to the apex... whack the throttle on exit...
the brain is engaged when on the throttle.. and the moto will go where you gotts your nose pointing... thats the reason you gotts to ride eyes open nose up looking far ahead and on the throttle... ease on the back brake and ease it off to navigate the twistys...
and breathe mang... breathe...
maximum yeeeehaaaaa...
j o
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No big difference. The rear brake shouldn't need be used below 20 MPH (30 KPH), IMHO anyway.
I use the rear brake when maneuvering at very low speed, when heading downhill on loose gravel and sometimes to supplement threshold braking but it wouldn't matter to me whether the rear was a drum or disc. Some riders don't use the rear brake at all and assert they get along just fine. The braking technique umbrella is a large one. :giggles
:popcorm
If twowheelgator's son undertakes this project, maybe photos of it will be posted as it progresses.
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That's the way I see it too, Laitch.
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But if you REALLY want to stop suddenly, some of our comrades insist "layin 'er down" is the most pragmatic approach. The rear brake works quite well for this trick. This belief may stem from their insistence that using the front brake will toss you over the handlebars.
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Johnny: you're my kind of dork and I mean that in the best possible way.
Laitch: I do the same, and living in a heavily congested area there is a lot of low speed maneuvering between lights. A lot of time I try to not put a foot down until the last minute so I end up playing the "go slow" game waiting for the light to change.
I normally use front and rear during normal braking and that is how I taught my son.
His biggest reason for thinking it does not have enough stopping power is that it will never lock up no matter how much pressure you apply to the peddle. His experience with rear disc is easily locking them up.
The shoes have a lot of pad left. The pads are not glazed. The drums could use a little sanding but are not too bad. It is in proper adjustment.
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Why would you want to lock it up? that;s what they invented ABS to avoid.
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I think his thinking is That The fact that it can’t be locked up with full force indicates to him that it does not have the same stopping power as a disk.
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I think his thinking is That The fact that it can’t be locked up with full force indicates to him that it does not have the same stopping power as a disk.
I'm thinking your thinking and his thinking are correct regarding the drum brake not being as powerful—at least as it is currently configured, if not altogether.
That's one of the reasons disc brakes supplanted drum brakes. It's likely he could lock up the rear drum brake if it were hydraulically actuated or perhaps if the brake lever were differently configured for greater leverage. Maybe the current system on his moto just needs more fine tuning; however, trying to demonstrate one of those other drum brake operation options might be an interesting project for a student to undertake.
Locking up the rear brake would seem to be mainly important to stunters, and bulked-up riders carrying full loads of touring gear in San Francisco waiting at stoplights to travel uphill. :giggles The ability of the rear brake to shed heat might be important to all riders. Front brakes seem to be universally considered as the best sources for braking power. I'm fairly certain riders were low-siding by skidding long before rear disc brakes became common.
Your son is attending motorcycle technician school and, if he hasn't already, should pose this question concerning the importance of lock-up capability in rear brakes—and why his drum brake won't lock-up—to his instructors. Opinions generated by that discussion should be shared.
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it could be a matter of conforming the machine to the man rather than the man conforming to the machine. If the former, I'd go the paralever route and thoroughly modernize the back end.
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Initially BMW supplied different pads for the front and rear brakes. The rear pads supplied had less bite to avoid the issue of brakes locking.
Regards Martin.
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Of course! Disk is 100% always superior braking power over drum, looks cooler, chicks dig it. Went non abs 87s to 94s this year and when driving hard it allowed me to learn to push the unit to its limit. I use rear always as a practice.. my form of unified braking . So much time spent growing up hot riding beetles, all I generally
want to know is does it have rear disk brakes? If not, how do I get em. If I had been infected by a c I’d have found an s. And yes for every day tooling around drums are fine obviously right?🧐😬
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Thanks for the interesting discussion.
The next question is: Is the rear brake on my 86 K750 providing the same stopping power as other 86 k75s with a rear drum brake?
Who has a K75 with a rear drum brake that is willing to do some parking lot tests? This weekend I will try to sand my drum to ensure it has a good surface then measure some stopping distances using only the rear brake at different speeds on flat ground. I will also measure ambient air temp and the amount of time I warm the bike up and include my body weight. Any other variables I need to think about?
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abs1 or other...
final drive oil weight...
single finger pull or 5 finger death pull...
last brake fluid change...
tior rotation arrow direction...
22l or bare bung...
how much air in lines...
rubber steel almuinum lines...
barometric pressure...
spoke or snowflake wheel...
replace air with nitrogen...
fairing and windscresn drag...
full tank of gas...
brake pad temperature before and after...
brake pad thickness...
concrete or assphalt...
parking lot temperature...
altitude...
direction of travel...
bias ply or radial...
tiror size...
single or multi rubber compound...
boot size... hard or soft sole...
sunny or cloudy...
dew point...
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metallic, sintered or organic?
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New or old cable?
Lubricated or dry cam?
Popeye or Wimpy forearms?
Paper or plastic?
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... the 'S' model has a disc ...
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LOLOLOLOL. It has been a miserable week at work and I needed this tonight.
The testing is scheduled to begin tomorrow afternoon. I will keep you posted so all you drummers out there get ready.
I will also make sure i make passes in both directions to compensate for wind.
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I will also make sure i make passes in both directions to compensate for wind.
That's right. Farting skews the data.
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Speaking of passing air ...