Drive Ratios for the RS.

[Deleted User 287]

Yep...the 33:11 on my R100RS allows close to 3750rpm at 60mph/100kph.
The 32:11 should be less rpm at the same speeds, but 3000 seems low. That's why I thought 'beem's FD might be a 32:11.

I agree that 3000 RPM sound slow for 5th gear, and I don't know why you would be looking for another gear.
These bikes don't like to be lugged (so I've been told).

Granted the R65 engine is a totally different animal, but I have a 31/9 and it is turning 4500 RPM in 5th at 60 MPH on the GPSr.

[Deleted User 287]

There is no stamping on the final drive? (Even though the gears could have been changed).

[Sunbeem]

I'll hose the cowmuck off the F/D and have a gander Rob.
Thanks 2valve, you've reminded me that the speedo was changed, sorry not to have mentioned that earlier, my thoughts were all transmission related.
I'll look for numbers on the dial as well.
I'm enjoying the erudition, thanks all.

Sunbeem.

[Sunbeem]

http://img98.imageshack.us/img98/6307/p1010393q.jpg

The pic is 90 degrees rotated for global equality.

So, on the F/D we have 33/11
On the speedo face W - 1,112

On the wheel rim, there's eleven thirty-seconds of an inch (18 mm) of play between wheel and universal joint,
three and one thirty-second inches or 77mm more in the gearbox.

Driveshaft to wheel ratio seems 1 : 3 or a fraction less.

Sunbeem.

[Jean]

A speedo with 1,112 should be mated with a "3.00" rear end...you have a 33/11 so both items are matched.
A higher speed rear end came on USA RS's according to my ancient Auxilliary Catalogue: a 2,91 which needed a speedo with numbers of 1,078.
To further confuse you, I note that the R100/7 came with a 33/11 up to serial number 6 147 574 and after that, with a 34/11 for a rear end ratio of 3.09...much "lower" that would mean higher RPM at 60 mph. I suspect this was during the 55 mph time.
Depending on your serial numbers, (1) someone changed your bike's parts. (2) *It is not a US delivery. (3) You are running a BIG rear tire that influences things to not make good sense...[* further inspection in my book shows the Canadian delivery bike came with a 33/11 gear set: a 3,00 ratio, which needs a 1,112 speedo. Is your speedo labeled both in KM and MPH?

[Jean]

I hit send too quick.
The other item is, your rev counter is not feeling well. What does it read as your hot-idle rpm?

[Deleted User 287]

I hit send too quick.
The other item is, your rev counter is not feeling well. What does it read as your hot-idle rpm?

Ah - a mechanical rev counter - I hadn't thought of that.

Yes, it could be a weak spring or magnet in the instrument.*

(* from a fellow on R65 forum that repairs speedometers: http://www.bmwr65.org/cgi-bin/yabb2/YaB ... 7318/13#13 )

[Sunbeem]

Greetings Jean, and thanks for the info: when idling, the revs seems a bit fast at 1100, and the red light glows around 950, the needle shows no signs of uncertainty in use, so I am assuming (!) all is well.

6089494 puts it in the 33/11 bracket to be sure, and identifies it as an English import I believe. The face shows a large mph scale and an inner, smaller kph.

So, it seems all the markings agree, which would seem to indicate that if the revs don't match expectations, my F/D doesn't match the markings ?
Or that my speedo should be in Canada ?

Sunbeem.

PS.Rev counter's electronic Rob.

[2valve]

hi to all, wonder if a PO (of the instruments) has had it calibrated for another diff ratio ? it can be done, no matter what the face number reads. jean i also didnt think of the wrong profile tyre fitted , yep been there wrong tyre profile fitted and speedo was out.

[vanzen]

The discussion has certainly been entertaining ...

The RS was usually fitted with a 33:11 ...
but the only way to know for sure what you got at this late date –
will be to look at the stamping on the FD.
The ratio of the speedo fitted will be clearly indicated on the face below the center of the needle.

Do not expect accuracy –
If you need that, attach a GPS.