BMW R80 Rear Drive Gear change

bernardofeio

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hello

I want to change the rear drive ratio on a R80 G/S. Originally it's 37/11 and I want to change it to 32/10

I already have all the necessary parts... I hope

did anyone already pressed out the gear from the central hub? any recommendations? :rob:bow

(would be so nice to put a picture where!!)
 
Haynes says it is not DIY , and he is correct, you need special tools to do the job.
Clymer lists out the tools and procedure , and the factory manual adds a bit more.
Every U-tube Vid on final drives I have seen has been absolute tosh, worst of all the spoof vids put out by Boxer Two Valve or summat.
 
my manual does not refer nothing related to that... what manual are you checking? thks
 
I thought people just put the whole different bevel box on as a unit when they did a gearing change?
 
BMW issued a factory workshop manual. It sets out how to repair every facet of the bike ,often using special factory tools.
Haynes gets a copy of the factory manual then strip a bike and rebuilds it , as far as possible using standard tools, photographs the process and essentially rewrite the manual in laymans language. And makes himself a very rich man.
When he approached the final drive he realized there wee no standard tools which replace the factory special ones, and the cost of the specials make working on them not a DIY job.
Clymer in the USA does much the same as Haynes, but he listed out all the special tools by part number just in case anyone had no alternative but to buy them and do the work themselves. And then did a poor job of stripping and rebuilding one missing out some vital steps.
But as you have already bought the parts you may as well pull it apart and have a go,you can't do any worse than the guys who have posted on Utube.
But ignore Boxer Two Valve, his are spoof vids smocking those who believe everything they see on Utube!
 
A lot easier to do that, I'd have thought! :thumb2

but you you have a G/S (3 studs) bevel box with 32/10 ratio to sell? Honestly I did not find many. They appear in the part catalogue as an option but i guess that there are not too many around
 
In theory,it’s straightforward enough,
The reality though is a bit more complicated.
IF,
You damage the alloy bearing support pressing it apart and back together or cannot get the crownwheel running absolutely true,
You will have scrapped your bevel.
3 stud bevels in good condition are extremely difficult to get hold of,
For this reason I would leave the bevel well alone or get another crownwheel out of a damaged unit to pinch the alloy bearing support.
 
Hiya, just swapping my 31/9 to a 37/11 final drive (complete unit). Inspection and seals replacement, plus pinion bearing that had the (outer) inner race on a shelf for years that is rusty. Gears and all other bearings are in good condition.

Since buying the bike 3 years ago, I've done quite a bit of replacement and Youtube has been very handy. The shouty guy who swears a lot, another chap in Finland I think and the very personable Boxer2Valve. I just watched his vid on rebuilding a final drive as I am doing that now. His process, method and measurement for bearing change in a final drive assembly is quite satisfactory. Likewise what he's done with Bing rebuilds, front wheel bearings etc.

The internet is obviously open to abuse and alternative or just misinformed advice and information. I don't believe that is the case here.

I think if assembling a new (or new to this box) gear set in a particular box would need more setup to be correct (blueing the gears and checking the mesh etc) but for a worn set in the box it came in and was originally set up for - that seems to be going a bit far. Gears with 30,000, 60,000, 100,000? miles on them are not going to set-up in the same way as a new set and by definition are not going to last as long. A good approximation IS going to be good enough.


What exactly is he doing incorrectly? (before I nail the FD cover back on :) )


[Apologies, this is a diferent (and technically much easier) question to the OP, but on the same theme. I'm using all the same internals apart from the input ball bearing and have a conventional (full axle, dual shock) all-steel crownwheel assembly].
 
Wouldn't it be easier to fit a higher top gear in the gearbox ?

done that

Overall gear ratio of the R80 G/S is very low. I get 5000rpm@120 km/h and 6000rpm@140km/h even with I high 5th rear installed. With 140/80 x18 tire this speed is matching the GPS real speed. Even for off-roading increasing the ratio to 32/10 will probably be ok but time will say
 
Yes. I'm only getting 2.4%

It sounds more effective quoting RPM at 70MPH:
dogshome 4592 to 4486
bernardofeio 4486 to 4273
(his high gear making both numbers 5 or 8% better still).

Ref bmwmotorcycletech.info
 
I have done lots of Guzzi rear drives, if you are a competent mechanic it’s not to bad a job.
It’s not the disassembly that’s difficult. It’s getting the shimming correct for the crown wheel and pinion.
Honestly if your not happy pay someone that has lots of experience Moorespeed, Jim Cray Andy Sexton
Etc
 
Yes. I'm only getting 2.4%

It sounds more effective quoting RPM at 70MPH:
dogshome 4592 to 4486
bernardofeio 4486 to 4273
(his high gear making both numbers 5 or 8% better still).

Ref bmwmotorcycletech.info

the change is 5 % => I will gain 7.5km/h at the same engine 5500 RPM

in fact if I change the final ratio to 32/10 I get the same final ratio as in the R100GS (that uses 17 rear wheel and 34/11 rear drive ratio)
 
Yes. I am only going to get 2.4% :(
[you will get 5% :) PLUS your exchanged 5th gear :) :) ]

The time-warp effect of 860 on 650 gearing is fun at the traffic light grand prix, but the buzzing at 120KPH up-hill, down-dale, up-quite-steep hill is now unnecessary. The engine will lift the bike's nose a little without pinking in 5th on quite steep hills, so will easily accept higher gearing. The 2.4% I will get is a little help. Your 5% + higher 5th gear would be better!
 
I understand that the g/s final drive is unique to the g/s with its 3 studs vs 4 studs. Is it not possible to use a 4 stud final drive and wheel from another mono shock, re-lace the drum to the g/s rim?
 
I understand that the g/s final drive is unique to the g/s with its 3 studs vs 4 studs. Is it not possible to use a 4 stud final drive and wheel from another mono shock, re-lace the drum to the g/s rim?

Afaik,
BMW never made a 4stud/bolt fixing spoked wheel.(mono)
Apart from a paralever one,which needs a fair amount of modifications to fit a mono bevel
 


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