Long Wheel Base and the R65

[Jon_P]

I have heard of the short wheel base models and then the they where changed to the long wheel base models. What is the R65? I am guessing it was made a long wheel base from the start? So swingarms, final drives and rear wheels all interchange correct on the long wheel base units?

[scottyintex]

The wheel base on the R65 was 54.72 inches till 1981 when it jumped to 55.11.   I don’t think the overall length changed. The LS has the 55.11 wheel base. My R65 has a custom triple tree to accommodate the sidecar which stretched everything three inches. I know the R75/5's have a short and long wheel base....54.5 jumped to 56.5 and think the R75/6 jumped another inch.  I do know they recommend the longer wheel base R75's for sidecars over the short one.  Some of the other models may have different sizes. Somebody help me out there.

[NC Steve]

To my knowledge, the only real choice in wheelbases was in the 1973 /5 bikes, when BMW came out with a long wheelbase model in the 2nd half of '73 and the buyer had a choice between the traditional "short" wheelbase and the new "long" model. These are sometimes referred to as 1973 1/2 models.
Beginning with the /6 series in 1974 and on up, there was never any specific designation as short or long, although the bikes were/are generally considered to be long wheelbase models, and therefore to possess more stable handling characteristics.

[Jon_P]

so are all the swing arms, drive shafts, final drives and rear wheels interchangeable?

[NC Steve]

Uhh, no, they're not interchangeable: as usual there are exceptions, and the R65 is one, as they had a newly designed frame, engine, etc, as well as 18" wheels vs. the 19s on the larger bikes. There's a few parts shared with the R80ST and G/S, also new models at the time, but not many.
The later '85 & up Mono R65s had a good bit of interchangeability with the R80s and R100s, but the '79 - '84 twin shock R65s stood alone for the most part.

[Jon_P]

so the wheels i am looking at getting wont work? i'm confused now. the transmissions are the same? the swingarms are different? what about final drives? and if swingarms are different then i would guess so are the drive shafts.

[NC Steve]

I'm gonna defer to someone more knowledgeable after this (Rev Eddie?), but the wheels, frame, driveshafts, final drives, swingarms, and I think the transmissions too are unique to the R65s. That's why it's sometimes a pita to find the right parts, 'cause generic Airhead stuff is everywhere.
Remember searching for those R65-unique Brown's sidestands?
That's not to say other parts can't be made to work, but it won't be a strictly bolt-on affair.

[Rob Valdez 79 R65]

Yes, driveshaft length is most likely different.  For one thing, the '79 ('78 in EU) R65 was the first to feature the spring-loaded cush drive in the shaft.

The final drive housings are interchangable with those of the era, but the larger bikes will have different gear ratios.

I was not aware of a change in wheelbase in the 80/81 updates, but I am too lazy right now to research it.

There were many changes made to the swingarms over years, but I think the length stayed the same, except for, of course, the early /5 and the R45/65.  Which, BTW, are said to have a similar wheelbase.  But I think improvements in chassis technology between 1969 and 1978 really helped the R65 achieve what the /5 could not.

Jon:  here is Duane's page on SWB/LWB: http://w6rec.com/duane/bmw/whbase/index.htm

[nhmaf]

The only differences in the transmissions are between model years, as when changing from the 4 to 5 speed in the 70s,
and changing to the lighter clutch assembly in 1981, changing the input shaft spring/ears, etc.   A transmission from an R65, R80, or R100 should all be
the same unit for a given year, IMHO.

[steve hawkins]

Jon,

Any rear wire wheel will fit an 65, from any twin shock model.  All rear wheels ar 18 inch whatever model.

It is the front wheel you need to be careful with.  It has to be the slim hub as fitted to early GS and ST models.  The hub that is used with ATE swinging caliper setup will not work....You would be better going for a drum front wheel and forks from a /5 but sticking with the triple tree of the R65 - if you can get it to fit, for that period cafe racer look.

You can fit a 19 inch wheel to an R65 but it will make it steer like one of Orange Counties best choppers - I.e. crap!  

The fix is simple, lift the fork legs through the trip tree by half an inch.  It really is as easy as that.

You will have to check the clearances of the front fender though if your is a standard one.

I have one fitted to mine, honest.

Steve

[steve hawkins]

I was also under the impression that you could also retrofit an unsprung drive shaft in place of the sprung one fitted to the twin shock R65.  

Why you would want to do so is beyond me - except for racing purpose perhaps?  

But I assumed that the drive shaft lengths were the same for all models of a similar period....but I could be wrong.

Even though my drive shaft could do with an overhaul (its clunking a bit on take up), I would not fit an unsprung one.  My gearbox has 100,000 miles on it, and the last thng I would want to do would be to increase the shock loading up from the rear wheel.  The mod was introduced for a purpose, one of those was to increase the life of your gearbox.  Second hand R65 gearboxes are good news to any other boxer owner wishing to replace thier knackered gearboxes.....

Steve

[bpw]

My r65 has a stock rear wheel with r90 rear end to give it longer legs.  I didnt do the conversion so cant help with specifics though.