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Dmaster 01-28-2013 05:22 AM

Final drive weigth reduction
I've searched the internet and this forum but couldn't find any info I'm looking for.
Did anyone ever tryed to get some weigth out of the final drive?
Does anyone know of someone doing it? Any picturs available?
What could you take away, drill/machine/whatever?

JonnyCash 01-28-2013 05:35 AM

I've seen people put holes in the aluminum housing, but i think that's more for the look than anything else. I'd imagine that one could pare some weight from the ring gear, like you would with a flywheel. That said, when I pick up a BMW final drive, I feel like it is pretty light, for what it is. Go pick up one from a Guzzi, it's much heavier, and then you'll be happier with the weight of the BMW part!

Big Bamboo 01-28-2013 11:29 AM

Jim Roche aka "Dr. Curve" did some lightening of his White Dog racer. Not a huge weight savings, but it is some...

Dmaster 01-28-2013 02:02 PM

The housing (is that the right name?) isn't the heavy part its the "gears"
why not cut the red parts?:
this isn't gonna help much but why is it here anyway?

I'm sure I can get some material of the small gearing but how much will it be. :evil

Someone must have tried this before.
I know about "lightweight gearboxes" (drilled holes in anything) why not the final drive :ear

chasbmw 01-29-2013 02:42 AM

The later final drives look lighter.

Just think of what would happen if your final drive locked up......declutching won't help.....

chollo9 01-29-2013 04:52 AM

Like chasbmw says, transmissions are risky places to lighten.

Weight savings is always about the sum of little bits (bites?), but in some places reliability and maintenance aren't good tradeoffs. I would want to talk to a rear end specialist prior to removing any metal.

There's weight to be saved in the hub, I think.

Airhead Wrangler 01-29-2013 05:34 AM

The gears are heavy, but out of a total weight of 17 pounds they only account fo about 6 pounds, so theres a lot of metal just in the housing.

disston 01-29-2013 04:41 PM

Leave off every other nut, bolt or stud.

Leave out the rear brake shoes and other parts of the brakes.

Leave off every other spoke on the rear wheel.

Buy a skinny tire.

Of course you could also buy a Honda? :lol3

RonZacapa 01-30-2013 09:43 AM

The sum of parts is all in the unsprung weight. When I went from a tubed tyre to tubeless and junked the heavy duty tube on the rear wheel on my 1985 R80 monolever I threw away 3.65 lbs of weight. I would rather look at weight savings elsewhere on the bike, it can be done.
R80 Monolever roadbike = 175kg dry with an empty tank (385lbs for you imperial guys) I got another 6kg to go - 169kg no fuel. However I will not be reverse engineering important mechanical bits & pieces I know not much about. If you are obsessed with weight reduction (so am I) lets start with the easy bits.

Airhead Wrangler 01-30-2013 10:16 AM

The point here though is that it's not JUST weight reduction, but suspension performance as well.

Prutser 01-30-2013 01:11 PM


Originally Posted by Airhead Wrangler (Post 20610271)
The point here though is that it's not JUST weight reduction, but suspension performance as well.

I know that the suspension performance is his main purpose.

supershaft 01-30-2013 02:13 PM

I believe the later FD's are heavier. Dr. Curve's modification is about all you can do. The gears are too hard to work with. I would leave the internal oil baffling alone. If I know Dr. Curve, that's a magnesium wheel. THAT's the solution. I wish it wasn't such a pricey solution!

Dmaster 02-12-2013 01:39 PM


Originally Posted by supershaft (Post 20612203)
I believe the later FD's are heavier.....

Later? twin shocks vs mono arms vs para levers?
Tell me more, i wanna know all :evil

Originally Posted by supershaft (Post 20612203)
....that's a magnesium wheel. THAT's the solution. I wish it wasn't such a pricey solution!

I'm into offroad,. somehow I want spoke wheels in a offroad. Don't know why either.

AliBaba 02-12-2013 02:09 PM

Gjendem's bike has a lighter final drive and gearbox (and loads more). There are some pics here but they don't show the details:

HPN has also done the same thing, there is a crappy picture of a modified gearbox somewhere at

jackass dave 02-12-2013 03:03 PM

how about the rider going on a diet ,that would lighten the overall weight !!!

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