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Old 08-01-2013, 06:44 PM   #16
adrenal
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Quote:
Originally Posted by Jim K in PA View Post
Kicking this (great, informative) older thread to the top to get some feedback on low speed technical riding (picking a line through rough stuff, etc). My '79 R100T has its original 32/11 final. With a 120/90-18 rear tire, I feel I have to slip the clutch too much to keep it from stalling on some steeper, rocky hills. And that was with no extra gear (weight) on the bike.

I just replaced the 120/90 rear tire with a 4.00-18, which is narrower, but even taller. Should I look for a 32/10 or a 37/11 final to keep the revs a bit higher at low speed? Or is the difference between the two (only 5%) not worth worrying about?

I am not an 80mph highway kind of rider (no faring). If I have to slab it, I prefer 65-70 max unless I am passing someone. Overall I prefer back roads at 50-60 and dirt roads & trails at a lot less!

Thanks for any more detailed BTDT input.
.

Gearing can be subjective thats for sure - need to suck-it-&-see. Shame that you're on other side of planet, I have a spare 37/11 that I could have loaned you to try. Though I reckon the 37/11 may be going too far the other way - maybe 34/11 or 32/10??

Difference between 32/11 and 34/11 is 7%
Difference beween 32/11 and 32/10 is 10 %
Difference between 32/11 and 37/11 is 15 %

When you look at it in these terms, 5% is a noticeable amount

Don't forget that your speedo will read wrong with a different bevel ratio.
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adrenal screwed with this post 08-01-2013 at 07:15 PM
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Old 08-01-2013, 07:07 PM   #17
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If it were me, I'd look for the 32/10, because it sounds like I like to go a bit faster than you . But the 37/11 was the 'most common' final drive made for the dual shock ... you can find one of those really easily. Just make sure you get one with good splines. For the sort of riding you describe, either would be fine. A 37/11 with the R100 engine you would see a HUGE response off the line ... and depending on the balance of your flywheel, should be very smooth all the way to 80 or so.

Play around with this page: http://www.largiader.com/articles/gearing/

This is Anton's gem ... and because all of BMW airhead transmissions are the same, we can compare final drives. I think if you realize that giving up top end will increase your bottom end ... you can figure out what you want.


Quote:
Originally Posted by Jim K in PA View Post
Kicking this (great, informative) older thread to the top to get some feedback on low speed technical riding (picking a line through rough stuff, etc). My '79 R100T has its original 32/11 final. With a 120/90-18 rear tire, I feel I have to slip the clutch too much to keep it from stalling on some steeper, rocky hills. And that was with no extra gear (weight) on the bike.

I just replaced the 120/90 rear tire with a 4.00-18, which is narrower, but even taller. Should I look for a 32/10 or a 37/11 final to keep the revs a bit higher at low speed? Or is the difference between the two (only 5%) not worth worrying about?

I am not an 80mph highway kind of rider (no faring). If I have to slab it, I prefer 65-70 max unless I am passing someone. Overall I prefer back roads at 50-60 and dirt roads & trails at a lot less!

Thanks for any more detailed BTDT input.
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Old 08-01-2013, 08:08 PM   #18
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Originally Posted by supershaft View Post
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!
I built a 2.75 for a guy who was going to Bonneville with a hot-rodded R75. To no ones surprise (except his, I suppose), it was way too tall.
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Old 08-01-2013, 08:23 PM   #19
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Quote:
Originally Posted by bmwrench View Post
I built a 2.75 for a guy who was going to Bonneville with a hot-rodded R75. To no ones surprise (except his, I suppose), it was way too tall.
Hey wrench, so you built one with new crown and pinion..
Is there a source for longer than 32/11 gear sets?
(apologies for threadjack Jim)
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Old 08-02-2013, 07:49 AM   #20
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Great info and feedback. Thanks.

Adrian - no 'jack, no worries. This is a final drive thread, and I didn't even start it! it looks like you can build a final down to 2.54 according to Anton's site (linked above in Fred's response). But they are listed for later R and K series bikes. Perhaps the 'wrench can offer insight into gearing that low on an older R bike. Thanks for the offer of a loaner to test, but we are a good ride apart.

Fred - thanks for the input. I think I will look for a 37/11 in good nick and give it a try. If it turns out to not be what I want, I'll sell it on and get a 32/10. If the 37/11 works out, I can change out my stock 5th gear for the slightly taller version to get some top end back, if I feel the need for speed. Stock 5th is so close to 4th as to be almost pointless, IMO.
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Old 08-02-2013, 10:04 AM   #21
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Quote:
Originally Posted by Jim K in PA View Post
Stock 5th is so close to 4th as to be almost pointless, IMO.
I totally agree. I'd love to keep the lower gearing for ~0 to ~65 and then have 5th take me to 80 and the engine is still at 4,500. Right with you.
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Old 08-02-2013, 10:29 AM   #22
Jim K in PA
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And Vern just listed his 31/9 in the FM. That is 18% higher than my 2.91. I would really need to do the taller 5th with that gear set.

Have to look up how much taller the higher 5th gear is.
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Old 08-02-2013, 01:47 PM   #23
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Higher fifth gears are 5% taller according to info in the ads.
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Old 08-03-2013, 02:32 AM   #24
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When I get my bikes together... I have a 37:11 and a 32:10... I will try both with a few gear boxes... one with lowered 1st and higher 5th, another with higher fifth and the rest standard and another with a completely standard box. For my use (60dirt/40 road) I'm thinking the 37:11 with the higher fifth will be a good selection... the 32:10 with the lowered first and high should also work out well for my intended uses. I see lots of talk about gearing but no real mention of what people intend to use them for. I want good slow speed work for tight off road bits... but a higher 5th for getting there in the first place! For bimbling around I certainly see nothing wrong with the 37:11.
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Old 08-03-2013, 03:58 AM   #25
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Originally Posted by adrenal View Post
Hey wrench, so you built one with new crown and pinion..
Is there a source for longer than 32/11 gear sets?
(apologies for threadjack Jim)
anyone?
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Old 08-03-2013, 05:11 AM   #26
Jim K in PA
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Quote:
Originally Posted by Clay Spinner View Post
When I get my bikes together... I have a 37:11 and a 32:10... I will try both with a few gear boxes... one with lowered 1st and higher 5th, another with higher fifth and the rest standard and another with a completely standard box. For my use (60dirt/40 road) I'm thinking the 37:11 with the higher fifth will be a good selection... the 32:10 with the lowered first and high should also work out well for my intended uses. I see lots of talk about gearing but no real mention of what people intend to use them for. I want good slow speed work for tight off road bits... but a higher 5th for getting there in the first place! For bimbling around I certainly see nothing wrong with the 37:11.
Clay - what you describe above is exactly what I am looking to do with my bike. Although the ratio between dirt and road is going to flip back and forth depending on the trip and opportunities. I want to take my bike on the TAT, up to James Bay, Labrador, etc. I also have local trails and dirt roads to play on. However, highway use will still be a necessary part of my riding profile at times.

I wish I had access to a variety of ratios to try out, but alas, do not. I will probably wind up buying and then selling different finals until I find the combo I want.

My transmission works fine, and only has about 35k miles on it, so am reluctant to tear it apart. But, I really like the idea of the 32/10 with the lower first and higher fifth. Bah, it's only money, right?

Thanks for the input.
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Old 08-03-2013, 11:08 AM   #27
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Jim, how about rocking labrador and newfoundland next year? Ill be in nova scotia and you meet you in northern new brunswick or ontario depending on how you cross the border.
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Old 08-03-2013, 11:50 AM   #28
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Jim, how about rocking labrador and newfoundland next year? Ill be in nova scotia and you meet you in northern new brunswick or ontario depending on how you cross the border.
I don't have any plans, but that sounds tempting. Shoot me a PM with your expected schedule. I could not commit to anything just now, but nothing would necessarily prevent me from taking a trip up.
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Old 08-03-2013, 12:32 PM   #29
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A friend of mine made a 33:13 set from an R1200C fit into his mono final drive. But he is using a 17" rear wheel with a 180/55 tire. So there are some options although you need to lose the drum brake too.

On my ST I was using a 32:10 with the taller 5th, but I didn't like it for my use.
After my last trip I changed it back to my stock 37:11 which is fine with the shorter first and taller 5th gear.(I.M.H.O)
I would even consider to use a 20Kw R65GS 31:9 final drive for the real off-road stuff. You could still do 160 km/h with that set-up.
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Old 08-03-2013, 04:11 PM   #30
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Originally Posted by Prutser View Post
A friend of mine made a 33:13 set from an R1200C fit into his mono final drive. But he is using a 17" rear wheel with a 180/55 tire. So there are some options although you need to loose the drum brake too.

On my ST I was using a 32:10 with the taller 5th, but I didn't like it for my use.
After my last trip I changed it back to my stock 37:11 which is fine with the shorter first and taller 5th gear.(I.M.H.O)
I would even consider to use a 20Kw R65GS 31:9 final drive for the real off-road stuff. You could still do 160 km/h with that set-up.
what do you mean "loose" the drum brake?

Do you mean, lose?
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