1150 gearing - 850 final drive or not?

[Womble]

I'm probably going to have to pull off the final drive soon and I'm wondering if now is the time to play about with my 1150's gearing.

On my 1150, first gear is too tall and, because I have the overdrive gearbox, there is an annoying gap between 5th and E. Out of the two issues, the lower first gear is the more important, because I intend to use the bike on the trails more regularly.

Initially, I would have gone for trying to change the ratios in the gearbox or swapping out for an Adventure gearbox, but it sounds like a really good and simple alternative is to use an R850GS final drive. The problem is that R850GSs are as rare as rocking horse poo, so the chances of picking up a secondhand final drive are pretty low.

Has anyone swapped out the 1150GS final drive for an 850GSs? If so, I would be interested to hear how well it worked, and what the effect was on general tractability and fuel consumption because I don't want to ruin a great bike.

Out of interest, has anyone got a spare 850 FD or an Adventure gearbox, or can someone suggest how much it would be to swap the ratios?

 

[Grizzly]

850R??

Hi Womble,
Can't comment on the sense of you plan - but regarding availability of donor final drives because "850GS's are as rare as rocking horse poo" - I am sure the final drive from an R850R is exactly the same ratio as one from a R850GS - because they are exactly the same on a1150R/1150GS - any difference in part numbers is due to both parts of the case on the GS version having mountings/holes for the plastic crud catcher. So if you could live without a crud catcher then that would maybe give more options.

Cheers......................Grizzly

 

[davegs]

Bevel boxes

850 is a no no, much too low you'll end up doing wheelies in top! and a max of 70 at about a million revs!!. I have done it and it don't work, 1100 box the the way to go 11-33 gives a lower bottom gear an not too much diifference in top, over drive is a bit less but I've had mine in now for over 45'000 and would not go back. Originally started experimenting for the trip from Alalska to Arhgentina in 2007 which included a lot of dirt roads 850 was recomended on the ad venture site but I found it much too low so DON't go there. PM me if you want a chat and I'll give you my phone No but it is lovely in traffic, really brilliant and also for hair pin bends if doing the alps. I put the opriginal back on returning home from my little poodle changed it back soon after as thwe lower was so much better.
Dave (low geared) GS

 

[Womble]

Very useful comments, thanks guys.

Looking at the Haynes Manual of Confusion, the 1150 FD is 2.82:1 and the 850 FD is 3.2:1. With a ratio of 3:1 for the 1100GS, that sounds like an interesting compromise and a lot easier to find secondhand. In fact, it'll be even easier for me because I don't need to worry about any ABS gubbins.

Did the change in final drives affect your fuel consumption much?

 

[Vern]

On my 1100 I've got a bevel box off a 1100 RS, 31/11. Best compromise I've found so far, good all round with no down side that I can find

 

[davegs]

FUEL CONSUMPTION

Never noticed any difference apart from it seems to be better when TT panniers attatched (air brakes!).

 

[Packer]

On my 1100 I've got a bevel box off a 1100 RS, 31/11. Best compromise I've found so far, good all round with no down side that I can find

That is a 2.82 reduction, the same as Womble quotes for the standard GS.

 

[Paul Young]

HERE is a really useful site for experimenting on the different gearboxes & FD ratios available.

My problem was almost the opposite of the OP's, in that I found 5th slightly too low (hitting the rev limiter ) & the step to 6th too much for when I go to the IOMTT. I opted for an R1100S FD & geared it up a little. 1st gear is still manageable as the other performance mods (powercommander/filter & alloy wheels) allow it to be used to trickle along on tickover w/o too much clutch work.

Hope the link is useful...

 

[Trullion]

While I love my 850GS the one thing that I don't like is the low gearing. I would gladly sacrifice a bit of acceleration and top gear flexibility for a more relaxed feel at normal cruising speed - usually an indicated 80mph but a more accurate 73 ish. Don't know about an 1150 with 6 speeds but I wouldn't want one that revs as high in top as my 850. 1100GS gearing would probably be best, or maybe an 1100RS if you want something a little higher geared than the 1100GS - though you'd have to do without the muck catcher. Just my opinion.