Final drive Q...

[DiabloADV]

The two airheads I have (R60/5 in parts, and R90/6 "dirtbike" being restored) both came with 37/11 final drives. Am I right in thinking this ratio is not ideal for highway miles (ie, dualsport) on the R90/6 (which is actually 1000cc)?

What ratio drive should I look for for all-round riding (ride the highway to the trails, and then ride on the trails)? I can always keep one of these for a genuine offroad trip.

And...anybody want to trade me a higher ratio drive for one of these low ones?

[bmwhacker]

	ratio	ring/pinion teeth	rpm @55mph	rpm @70mph	speed @7200rpm	speedometer ratio	usual model
	2.91	32/11	3050	3881	130	1.078	R100
	3	33/11	3147	4005	126	1.112	R90S-R100
	3.09	34/11	3241	4125	122	1.144	R90-R100/7
	3.2	32/10	3357	4273	118	1.186	R75-R80
	3.36	37/11	3525	4486	112	1.244	R60-R75
	3.44	31/9	3608	4592	110	1.259
	3.56	32/9	3734	4752	106	1.318	R60-R65
	2.62	34/13	This was for racing, /5 and later

[pommie john]

The normal drive on the 900s is a 33/11 some had a 32/11 but if you find one of them, sell it on ebay they're quite rare.

[DaveBall]

pommie john, Which one are you saying is rare? All the RTs and RSs came with the 32/11, which in the day were called the Autobahn rear end as with it you got the highest top speed. The 33/11 was also very commonly found on a lot of other bikes, including some R90s and R100s. It was also a factory option for the R80s of 1978. I know of at least 3 R80s near by with the 33/11 and a lot more with the 32/10 and 2 that have the 37/11 which was called the Alpine rear end due to it being very popular with those that did a lot of mountain riding. In the mid 70s thru early 80s, you could order different rear ends on the bikes, if you were willing to wait for it to get shipped.

But, you could also pick your bike up at the factory or one of the dealers in Germany, back then as well. You just had to make the arrangements thru you local dealer and pay up front for it. I did just that in 1979 for a brand new R100RT, I got to ride it all over Europe with my wife, then take it back to them and they packed it up and arranged the shipping to Montreal where I picked it up again and road across Canada to home. They don't do that anymore, which is too bad. It was a great arrangement for a minimal extra cost. I think it was an additional $250 back then. Would probably be around $5000 now.

[DiabloADV]

So...sounds like I should be looking for a 33:11 for highway and backroad riding, and keep one of my 37:11 drives for offroad/mountain trips.

[Zodiac]

I have a stock 33/11 on my 88 R100 RS - and although it won't have the top speed on the highway that the 32/11 would, it'll still ride all day at 80 mph plus and hit over 100 without any complaints.

I think the 33/11 is better in real world back-road/country or urban anyway - torquier off the line, better low end usability.

[supershaft]

I would think the 37/11 would be about right for the R60. My '83 LS would cosistanly pull its 7650rpm redline in top gear and sometimes then some with its 32/9 but I guarantee you that a '81 on R65 runs a lot stronger than your R60. Hell, my R69S ran a lot stronger than any R60 I ever rode with. I don't think your R60 will pull a 37/11 but most people don't really care about that anyway. I like 32/10's on 900's. If your 1000cc 900 is running real strong, you'll like a 33/11. A 32/11 is faster than a 33/11? Just because a bike has taller gearing does not mean it will pull the taller gearing. There are a lot of airheads out there that would pull a faster top speed with a higher gear ratio than a 32/11! It would take one long down hill and a strong tail wind for many an airhead to pull redline with a 32/11. IMO, your wasting good engine if you can't pull at least redline in top gear but a lot of people love to gear them to the moon although they are never going to get out of orbit!

[ME 109]

Originally Posted by Zodiac

I have a stock 33/11 on my 88 R100 RS - and although it won't have the top speed on the highway that the 32/11 would, it'll still ride all day at 80 mph plus and hit over 100 without any complaints.

I think the 33/11 is better in real world back-road/country or urban anyway - torquier off the line, better low end usability.

Another vote for the 33/11
Road, dirt, trail.

[Beater]

Out of curiousity, what size is the rear wheel? If it's a 18" then I wouldn't go taller than the 34/11 ... if it's the 17" then the 33/11 is fine. The stock FD on my '91 R100GS is a 33/11 with the 17" wheel. The Dobber (R100) currently has a 18" rear wheel, and the 37/11 ... and it's too short. On loose dirt, it's difficult to not spin the tire. I'll put a 32/10 on it (I have one on the shelf), and I think it will be a fine medium for road and dirt.

I have to say though, the 18" wheel + the 37/11 ... I can go 80mph @ 5,000rpm. That really is a sweet spot.

[DiabloADV]

I have 17 for road and 18 for offload.

[Beater]

Originally Posted by DiabloADV

I have 17 for road and 18 for offload.

If you plan on swapping wheels for the specific purposes you described above, I'd get the 33/11 or the 34/11. You'll be very happy with both. Taller all around, and if you put the 17" on for dirt, you'll have plenty of room within the gear for off road fun.

[pommie john]

Originally Posted by DaveBall

pommie john, Which one are you saying is rare? All the RTs and RSs came with the 32/11, which in the day were called the Autobahn rear end as with it you got the highest top speed. The 33/11 was also very commonly found on a lot of other bikes, including some R90s and R100s. It was also a factory option for the R80s of 1978. I know of at least 3 R80s near by with the 33/11 and a lot more with the 32/10 and 2 that have the 37/11 which was called the Alpine rear end due to it being very popular with those that did a lot of mountain riding. In the mid 70s thru early 80s, you could order different rear ends on the bikes, if you were willing to wait for it to get shipped.

But, you could also pick your bike up at the factory or one of the dealers in Germany, back then as well. You just had to make the arrangements thru you local dealer and pay up front for it. I did just that in 1979 for a brand new R100RT, I got to ride it all over Europe with my wife, then take it back to them and they packed it up and arranged the shipping to Montreal where I picked it up again and road across Canada to home. They don't do that anymore, which is too bad. It was a great arrangement for a minimal extra cost. I think it was an additional $250 back then. Would probably be around $5000 now.

Maybe they're more common on your side of the pond, but when I was looking for ratios for my race bike the wreckers were full of 32/10, fewer 33/11 and 32/11 were hard to find in the UK.

[Beater]

Originally Posted by pommie john

Maybe they're more common on your side of the pond, but when I was looking for ratios for my race bike the wreckers were full of 32/10, fewer 33/11 and 32/11 were hard to find in the UK.

The 32/10 is 5% (or so) taller than the 37/11. I'm going to put that on my dirt bike. That with an 17" wheel is perfect for dirt ... put an 18" wheel on it for road, and you'll cruise at 80 mph all day at 4500rpm.

[supershaft]

Originally Posted by pommie john

Maybe they're more common on your side of the pond, but when I was looking for ratios for my race bike the wreckers were full of 32/10, fewer 33/11 and 32/11 were hard to find in the UK.

32/11's are the shit here in the states and are the most sought after ratio although I think they are too tall for most airheads. In my experience, 34/11's are the rarest. I have never even looked into the taller than 32/11 situation. I will never have a bike that could use it!