R1150GS Gearing

[Marc]

I've heard that one of our own has modified his R1150GS gearing to be somewhat lower (cRAsH, you listening?). Perhaps we could coax a few words out of him on this subject. I personally would be interested in knowing 1). How much lower first gear is post modification, 2). What parts / operations were involved, 3). Is the hassle / expense worthwhile, and 4). Any words of wisdom to those seeking to follow in your footsteps.

I'd be happy to reduce the entire final drive ratio by 10% - 20%, but any change would be welcome. It kills me having to slip the clutch so much getting started on a slippery hill because 1st is so damn tall.

[cRAsH]

Ok, here's the skinny.
I took the final drive from an 1100GS and mounted it on my 1150.
That changed the final to a 33/11 - a 3.0 ratio.
The stock 1150 final is a 31/11.

That means, in laymans terms, the shaft turns 3 times for the
wheel to turn once.


My take is that the marketing department told Hans to make a 6 speed
because the 1100 needed more top end and they needed to sell
the idea so folks would upgrade.
Hans made a very nice 6 speed, but the difference in top-end wasn't
enough to justify the cost for the bean-counters.
Since the tranny mod was probably already in the works when
this was discovered, the obvious solution was to change the ring
gear for more "top end".
On a faired bike, that works to a point. On the GS, you typically run
out of ponies before you run out of gear because the GS is streamlined much
like a brick.
I think it was a last second knee-jerk reaction, because the 1150 RT has
a 32/11 final. Why would it be geared lower than the GS????

Anyway, whatever the reason, we all know it's a joke.
The gear ratios in the tranny are pretty well spaced to me, but I
have a bias towards this bike.
If you change 1st, you then have to change 2nd, then 3rd,
somewhere the Piper has to be paid.
Plus, digging in your trannies guts is not a job for the squemish,
and is not an afternoon job.
Changing the final drive ratio is, if you buy the drive as a unit.
I got mine from the web for $300 - and it had many less miles than mine.
Here's the write up I sent to the list:

************************************************

It all started out so well, then I realized I didn't HAVE
a 12mm hex OR a 30 mm socket.
Off to Sears. They were out. Orchard Supply, nada.
3 autoparts stores and an hour later, I find one.
Cool, I head back home.
Oh yeah, the thread lock has to be heated to 280 degrees.
Crap, back to the store for a torch.
Now we're cookin'...
Get it put back together, hmmm, sure feels loose.
Look at the old drive, I forgot to put the U joint in!
DUH!
Take it all apart, put the U joint in, now its dark and cold.
... to be continued tomorrow -- I need a beer.

DON'T HIRE THIS MECHANIC!
Ok, this morning things went a little smoother.
The install went fairly smoothly, the most difficult part for me
was getting the splines to match up. Reminded me of the hours I've
spent laying under car tranmissions.
You almost need three hands for this bit, the drive is awkward to hold,
and the bearing races kept falling out when I forgot to hold them as I was
fiddling with the spline alignment.
Plop.
Dang.
Put it down, clean the race, put it back, start again.
Plop.
DAMMIT!.
Repeat.
Once I got it, though, it seemed so easy.
I think I could do it again in much less time.
Clean up the tools, don't forget to add the lube.
Ok, here we go - my driveway is steep and rough dirt and gravel - I've crashed
in my driveway twice, so this should be a good test. (Biff-boy, ya see....)
Wow.
It tractored right up. COOL! No more stalling, now I can lug it and get this:
It'll do 5 mph!!!!
Right off idle, no bucking, surging, just good, low-down grunt.
Man, this should be fun.
10 mph, which used to be the threshold to clutch fanning, now has the engine
running at 1500 rpm.
I like it already.

Time to suit up, and see what I lost on the top end.
WAHOO!!! It works!
80 mph = 4k rpm in 6th
80 mph = 5k rpm in 5th

Roll on (in 6th) from 90 - 120 = 10 seconds.

Not bad atall. Seems like I didn't lose any top-end. I'm sure in a wind-free
environment, or faired, it would be apparent, but not today.
Today, I was very happy. My biggest complaint about the 1150 seems to
have been fixed.

Big sigh of relief.

One unexpected treat - it's almost like I added 10 horsepower.
It feels like it pulls stronger in every gear, the front wheel was hopping up
easily on acceleration (no, I didn't wheelie for a half mile... or did I...?)

All in all, an A+ upgrade.

Summary:

What I did:
Buy a used final drive from an 1100GS to install on my 1150GS
(It actually had less miles than mine - go figure)

Why I did it:
As we who ride them know, BMW screwed up royally on the gearing
for the 1150GS. I was tired of stalling, and most importantly, fanning the clutch
in order to go slow.
This bike will do 125-ish in stock trim, but try to go 5mph without fanning the
clutch.
I need to do 5 MUCH more often than 125.
Changing the tranny gearing was out of the question - nothing available, and if it
was,
too much $$ - and what if I didn't like it? 'Sides, I can't do that myself.
And - my buddy on his 1100GS could pull away from me in any gear.
That chapped my ass.
He thinks it's hilarious.

Details:
Lauren Bish took the time to chart out all the gear ratios/final ratios for all the
GS's, (thanks Lauren) and concluded (as Chris at SJBMW did as well) that the 2.82
final
on the 1150 was just too low. The 1100GS (and RS I think) uses a 3.0 final.
Based on his calculations, we're talking about roughly a 6% difference.
To me, that sounded about right. I am really happy with the tranny ratios - the
gears seem to be spaced well.
6th falls on it's nose into a headwind or at less than 85 mph, but it's an overdrive,
and to be expected.
I could live with that.
What I couldn't live with was the difficulty this hoss has getting off the line -
I know the dealers always have a good chuckle at the new 1150 owners who
stall getting out of the parking lot, I've seen it.
So, the logical solution was to do like the old hotrodders did - change the rear-end.
Next question: which one will fit, and will it work?
After poking around, asking questions, hemming and hawing, I decided to give it
a try.
I found a used final on the 'net, bought it for $300 (including shipping - thanks
Jim).

The rest, as they say, is history....

************* Lauren's Chart and comments ********
Transmission ratios (all ratios are to One - omitted to save space)

Gear R100GS R100GS R1100GS R1150GS
5 speed Guenther 5 speed 6 speed
6 speed

1 4.40/4.66 4.25 4.16 3.86
2 2.86 3.16 2.91 3.02
3 2.07 2.44 2.13 2.39
4 1.67 1.92 1.74 1.96
5 1.50/1.41 1.62 1.45 1.70
6 ---- 1.42/1.34 ---- 1.32

The numbers after a slash are what I calculate to be a 6% overdrive or
underdrive.

Notice that the Guenther 6 speed with overdrive is fairly close to the
R1150GS six speed with the exception of first gear which is probably more
appropriately geared than the R1150GS first gear. A 6% percent underdrive
would give the Oilhead six speed a first gear ratio of 4.09:1, and a 10%
underdrive
would be about 4.25:1 - which would probably be better since the R1150GS
has a 2.82:1 final drive, which brings me to the next chart. To get the
big
picture on gearing a person should really know the overall gearing; the
combination of transmission gearing and final drive. One of the reasons
people notice the tall first gear in the new GS is that is has such a tall
final drive (2.82:1 compared to the 3.0:1 of the R1100GS and 3.09:1 of the
R100GS).

Gear R100GS R100GS R1100GS R1150GS
5 speed Guenther 5 speed 6 speed
3.09 final 6 speed 3.0 final 2.82 final
3.09 final

1 13.6/14.4 13.13 12.48 10.89
2 8.84 9.76 8.73 8.52
3 6.4 7.54 6.39 6.74
4 5.16 5.93 5.22 5.53
5 4.64/4.36 5.01 4.35 4.8
6 ---- 4.39/4.14 ---- 3.72

For the Airhead GS owners, you can see that the Guenther six speed without
the
taller sixth (he calls it an overdrive, but it would have to be less than
a
1:1 ratio to be a true overdrive), is about equivalent to the standard
five speed with a 6% taller fifth. The advantage would be that the gears
are
closer together, especially in the lower gears where I find second gear
too
high off-road. If the Guenther six speed were had with the 6% "overdrive"
then the jump from fifth to sixth would be just about the the same as the
jump from fourth to fifth on the five speed with the taller 6%
"overdrive" -
a jump I would not find objectionable as there is very little gap
between the standard fourth and fifth now.

For the Oilhead GS owners - you can now see why people complain about the
tall first gear; the tall final gearing exacerbates the problem. My
opinion is that the tall final gearing *is* the problem - not the tall
first. This is a good close ratio box; except for the jump from fifth
to sixth the ratios are even closer than the Guenther six speed - and
I think the larger gap between fifth and sixth is about right, even
better than the Guenther as I like my top gears to be tall and I think
the 1150 can pull the gearing. I think BMW made a good choice of ratios
in the box, but screwed up when they chose such a tall final drive.

Notice what happens if they had left the final gearing at 3.0:


Gear R100GS R100GS R1100GS R1150GS
5 speed Guenther 5 speed 6 speed
3.09 final 6 speed 3.0 final 3.0 final
3.09 final

1 13.6/14.4 13.13 12.48 11.58
2 8.84 9.76 8.73 9.06
3 6.4 7.54 6.39 7.17
4 5.16 5.93 5.22 5.88
5 4.64/4.36 5.01 4.35 5.1
6 ---- 4.39/4.14 ---- 3.96

Now notice that first gear is about 6% lower as are all the other
gears since that is the difference between the 2.82:1 and 3.0:1
final drives. You lose a little bit of top end but you still have
a top gear that is 9% higher than the five speed on the R1100GS.
The difference in the first gears drops from 13% to 7% - still
a little taller, but probably manageable and maybe the best
compromise that can be had. I guess what I am getting at is that
it might be more worth your while to check out whether you
can put 3.0:1 final gearing your 1150 than it would to pay
someone like Guenther to make a custom gear set (as much as I
want to keep Guenther in business - at least until I get my
six speed ;-).

Some more numbers I ran to see what I could expect for
different rations with the Guenther six speed on my bike.
All other remain the same and are shown for comparison.


Gear R100GS R100GS R1100GS R1150GS
5 speed Guenther 5 speed 6 speed
3.09 final 6 speed 3.0 final 3.0 final
3.0 final

1 13.6/14.4 12.75 12.48 11.58
2 8.84 9.48 8.73 9.06
3 6.4 7.32 6.39 7.17
4 5.16 5.76 5.22 5.88
5 4.64/4.36 4.86 4.35 5.1
6 ---- 4.26/4.02 ---- 3.96


Gear R100GS R100GS R1100GS R1150GS
5 speed Guenther 5 speed 6 speed
3.09 final 6 speed 3.0 final 3.0 final
2.82 final

1 13.6/14.4 11.99 12.48 11.58
2 8.84 8.91 8.73 9.06
3 6.4 6.88 6.39 7.17
4 5.16 5.41 5.22 5.88
5 4.64/4.36 4.57 4.35 5.1
6 ---- 4.00/3.77 ---- 3.96

Given these numbers I think I would choose the 3.0 final drive
over the 2.82 final drive for even a well breathed on Airhead.


Personally, after looking at the numbers, I think I would have dropped
first
gear down to nearer to 4.00:1 or left it at the 4.16:1 of the R1100GS and
then used the 2.82:1 or 3.00:1 final drive. But that is not what they did,
so people who have an R1150GS have three choices as I see it:

1) If they can, go with a 3.00:1 final drive - which I think would be the
cheapest and easiest route.
2) Go ask Guenther what he can do - I would only do this if I wanted to
keep
the 2.82:1 final because I liked the way the bike performed in top gear
with
regards to RPM (I think dropping down to 3.00:1 may actually improve
performance in sixth with regards to acceleration and top speed).
3) Leave it alone and learn to live with it.


I have two six speed bikes - both dirt bikes (a DRS350 and a TLR200) - and
I
think the optimal spread is to have a first gear that is good for
off-road,
second gear that is spaced fairly close to first, and a third that is not
spaced too far from second. Fourth, fifth, and sixth can be spread out
more
as I almost never ride in those gears off-road. Fifth and sixth should be
spread out fairly good as those I use for cruising down the highway.


One little note to make sure there is not confusion; as noted in my posts,
a
lot of bikes have a "primary gear reduction". The R1150GS has this primary
reduction gear, as does my DRS350.

This means that the transmission has a certain set of gear ratios
internally, but the effective reduction ratios *coming out of the
transmission* is not the ratio quoted; the ratio is that gear ratio
multiplied by the *primary reduction ratio*. This is why you will often
see
two different sets of ratios quoted for a given bike - as there are for
the
R1150GS six speed. The difference between the two sets of ratios is the
primary reduction - in the case of the R1150GS the primary reduction is
approximately 1.9:1, and you must multiply all of the ratios by that that
reduction to compare those ratios to the R1100GS ratios (unless you are
very
good at juggling ratios in your head) or you will be rather confused.

To get the "big picture" I usually look at the "overall ratios" which are
the *effective* transmission ratios, multiplied by the final drive
reduction
ratio. You could go even further and factor in tire size if you were
comparing bikes/cars that had differenct sized wheels/tires, but for our
purposes that is not needed.

[Baldy]

Great stuff, cRAsH. I have permanently enshrined it in the Hall of Wisdom with 5 stars.

Baldy

[RockyRaccoon]

I was out bashing around in the woods on my 1100 today. In a couple of fallen-log detours up the bank and through he duff it was so lugged down it was coughing to an untimely death.

My first gear is about 15-17% lower than a stock 1150, and probably still 6-10% lower than Crash's modified Pyg, bless her soul.

The 1150's first gear mocks the notion that it is anything but a street bike suitable for flat terrain. Even on pavement, if it's steep and loaded, the stock 1150 has to be a bitch to get rolling.

The bike is too big to ride fast (Enduro style) in the dirt, but the gearing is too high to ride slowly. So what the hell you gonna do?

I'd love to have an 1150, but I ride in the mountains and on dirt logging/fire roads a lot, and until they offer the bike with a decent 1st gear, I'm sticking with my 1100. It's marginal, but it's a damn site better when I'm loaded down, nose up a hill and have to get rolling.

[Baldy]

I spoke to Chris at San Jose' BMW who said they do these mods on quite a few 1150GS's. They recommend just installing a rear end from another model, which runs around $800, the benefit being it's quick, easy, and you can always change back easily if you need to.

The alternative is a $350-400 gearset yada yada. I think I'm gonna take the lazy way out and just roll it into them and say new gearset please, and where's the loaner bikes?



Baldy

[fish]

Originally posted by Baldy
I think I'm gonna take the lazy way out and just roll it into them and say new gearset please, and where's the loaner bikes?

um, boss...don't you need to buy a GS first?

[Baldy]

What is it about this message forum?

[fish]

I can just picture it. Baldy's gonna have an Adventure Rider party, where he's gonna invite all 380 of us, and he'll make his grand entrance wearing brand-new spotless Kalahari boots *with* the toe plates still attached and the accessory heel taps he will have added, take them off, toss them on the table by the keg of Sierra Nevada Pale Ale (inadvertantly showing everyone his pink anklet socks), reach under the table yank out his regeared final drive (with fingerless-gloved hands) and toss it on the table next to the boots.
When asked when he's gonna get a GS to attach to the low-geared final drive, he'll announce that he still hasn't decided among a GS, LC8, Tiger, KLR, F650GS, Gran Canyon, or C1, but that he's got all the brochures (with pages stuck together) under his bed.

or not.

[Baldy]

Too funny! Actually, I'm going for a 2002.5 mandarin GS. Why wait for the .5 release? Because I want brakes on steroids. I take sweetness & light on the back. The Colonel gave me religion on that one.

(And waiting a half year gives me time to hedge and get a look at the LC8 first, the MV Agusta of dual-sports.)

(And anyway, I can run away from y'all on my K1200RS on the streets or my KLR650 in the dirt.)

That's my story and I'm stickin' to it.

(Oh yeah and sweetness is gonna kill me for a third bike in the garage an' I need time to butter her up.)

Baldy

[cRAsH]

3.0 Rear Drive Unit Swap (Generously Submitted By Rod Depperschmidt)

TOOLS AND SUCH:
12mm Hex (Allen) Wrench
30mm socket (or box end wrench)
torch or heat gun
Loctite (Hi-strength/RED)
2 large tie-wraps (for rubber boot on rear drive)
Gear Oil (as needed)
Cheater bar (pipe)
3.0 Rear Drive Unit from R1100GSA (Note the "A" - must be ABS mode, assuming your 1150 is also ABS.
Also, I have been told that on some years, there is a slight difference in the shape/size of the front portion of
the 1100 unit, making it necessary to grind a small amount off to fit - nothing major, just a slight amount).
Assorted other "common" tools, normally used for wrenching your GS.
The GS manual is VERY handy, but not required.

SEQUENCE OF STEPS:
1) Place the bike on center stand.
2) Remove rear fender (plastic splash guard).
3) Remove rear brake caliper and ABS sensor (be careful to keep track of the spacers for the sensor). Use a
wire to tie the caliper up and out of the way.
4) Remove the rear wheel.
5) Loosen the bolt that attaches the reaction link to the rear drive unit.
6) Cut the tie-wraps from the rubber boot. Fold the boot back onto itself to open up the space between the
drive shaft housing and the rear drive unit.
7) Using the 30mm socket, remove the large nut on the floating bearing stud (on the IN side of the drive shat
housing).
8) Heat the floating bearing stud (this may take a while) until you are able to loosen it with the 12mm Hex
Allen wrench. You may have to use a cheater bar. Back it out most of the way, but do not remove it yet.
9) Heat the fixed bearing stud, located on the OUT side of the drive shaft housing (again, this may take a
while) until you are able to loosen it with the 12mm Hex Allen wrench. You WILL have to use a cheater bar -
trust me!!
10) Remove the bolt that attaches the reaction link to the rear drive unit (loosened in step 5).
11) Remove the floating and fixed bearing studs (IN side and OUT side of drive shaft housing).
12) Carefully remove the rear drive unit from the drive shaft by sliding rearward. The bearing races are
loose, so avoid tipping the unit either way as they will drop out.
13) Set the unit on a surface (DO NOT TIP ON IT'S SIDE). Using 2 flat-blade screw drivers, pry the spline/u-
joint from the front of the unit. It will simply pop loose.
14) Now, on the Rear Drive Unit from a R1100GSA, repeat step 13. The splines that mate to the drive shaft
are different between the 1100 and the 1150 - thus the switch of this item.
15) Remove the rubber boot from the 1150 unit and place it on the 1100 unit.
16) Install the spline/u-joint from the 1150 into the 1100 drive. I used a block of wood and a hammer to
"pop" it back into place.
17) Coat the splines and the bearing races with a good moly type grease and carefully slide it back into the
drive shaft housing. This can be a bit tricky as you have to get the spline on the u-joint lined up with the
drive shaft - both or flopping. You may have to reach in through one of the bearing stud holes with a long
screwdriver to line both up. Also, be careful that neither of the races fall out.
18) Start both the floating and fixed bearing studs and loosely attach the hardware for the reaction link to the
drive unit.
19) Apply hi-strength loctite to the fixed bearing stud and torque to 160Nm.
20) Apply hi-strength loctite to the floating bearing stud and torque to 7Nm. (This is the torque from the
manual - seems light to me, so I snugged it a bit more).
21) Install 30mm nut on the floating bearing stud and torque to 160Nm.
22) Tighten the hardware for the reaction link to the drive unit.
22) Position rubber boot and install new tie-wraps.
23) If necessary, fill rear drive unit with correct Gear Oil.
24) Re-install the rear wheel.
25) Re-install the rear caliper and ABS sensor. Check for proper clearance (gap) between sensor and ring
on rear wheel.
26) Re-install the rear fender (plastic splash guard).
27) Check your work and GO RIDE!!!!

[Hoppy]

That last quote regarding J-L was brutal. Did J-L slug the dude?

-Mike