KR100RS mirrors and 1100GS bevel box on 1150

[raginmund]

Dug out a couple of 1150 'buyers guides' from RiDE and T.W.O. last night. These mentioned two mods I hadn't heard of before:

1. K100RS mirrors to cut down on the blindspot.

2. Fitting the bevel box from an 1100 to shorten the gearing.

Anyone done these?

 

[Paul Young]

I think the mirrors you mean are these, from a K1200RS... Very effective & look nice, but a slight modification is required to allow the fast idle lever to function.

I know that plenty of riders have done the swap to a lower ratio 1100GS FD, but I found the 1150GS FD to be an issue, as I would run into the rev limiter in 5th gear. If I geared it down with an 1100GS FD, it would have been worse so I went the other way & fitted an R1100S FD instead. I used Anton Largiader's site to run simulations of the different options before dropping £100 on a low mileage FD & have been chuffed with the result. The only downside I've found is a limited amount of clutch feathering in really slow traffic (5mph or less).

 

[essjay]

I wasn't mad about the K1200RS mirrors. Found them to vibrate a fair bit.

 

[davegs]

Bevel box

The 1100 is the way to go, nop need to "feasther clutxch at all gives aration of 33-11 drops it jus a bit but the difference is amazing. Done alot of off raodding on it on returning from a long trip put the origianl back for a week soon put the 1100 back as it's so much better. Dunno what ratio 1100s is but think the 1100 is the way to go having tried others.

 

[Colban]

The 1100S FD runs at 33:12,which is 2.75,a higher ratio than the GSs 2.82.
It also looks like a different ABS sensor arrangement.Would that work on another model?.
Nice little graph from ADVrider showing road speed V engine revs for the GS Vs GSA.

 

[Paul Young]

The 1100S FD runs at 33:12,which is 2.75,a higher ratio than the GSs 2.82.
It also looks like a different ABS sensor arrangement.Would that work on another model?.
Nice little graph from ADVrider showing road speed V engine revs for the GS Vs GSA.

ABS sensor was a straight swap with the one on my 1150GS, but there's a speedo pick-up on the 1100S, so I just cable tied the lead from this out of the way.

1150GS FD ratio is 2.82
1100GS FD ratio is 3.0 (Gears the 1150 down. Makes it revvier but better off-road)
1100S FD ratio is 2.75 (Gears the 1150 up. Makes all gears "longer" meaning less frequent gear changing & "E" becomes even better for touring - 80mph = 4k rpm) This worked really well for me as my GS has alloys fitted, which has already had the effect of gearing down due to the smaller rolling circumference of the sports tyre.

 

[dancata]

ABS sensor was a straight swap with the one on my 1150GS, but there's a speedo pick-up on the 1100S, so I just cable tied the lead from this out of the way.

1150GS FD ratio is 2.82
1100GS FD ratio is 3.0 (Gears the 1150 down. Makes it revvier but better off-road)
1100S FD ratio is 2.75 (Gears the 1150 up. Makes all gears "longer" meaning less frequent gear changing & "E" becomes even better for touring - 80mph = 4k rpm) This worked really well for me as my GS has alloys fitted, which has already had the effect of gearing down due to the smaller rolling circumference of the sports tyre.

I think your speed is the same, no matter what diameter the front wheel has. I is only displayed wrong, but it's the same

 

[Paul Young]

I think your speed is the same, no matter what diameter the front wheel has. I is only displayed wrong, but it's the same

I used to be fairly sure that 80mph was 80mph whether I had a 21" wheel or a 17" wheel. Now I'm not so sure...

 

[sproggy]

The rolling diameter of a standard rear with a 150 dual purpose tyre and an alloy with a 170/180 sports tyre is nearly identical, depending on exactly which tyre brand/model you use. So the gearing of the bike will be unaffected by that change.

Changing from a 19" front to a 17" front will change the speedo reading and you need an RT (from memory?) speedo drive to correct this. You will appear (from the speedo) to be going faster with a 17" front than with a 19" because the wheel takes less time/distance to do a full rotation. As for a 21" that may have been a typo but the same principle applies of course.

Only on a bike with a speedo drive off the gearbox or rear wheel would the front wheel diameter not affect the speedo reading.

 

[Paul Young]

This is a bit of a thread hijack, so my apologies, but here's part of a post I made on this subject in Oct 2003. Hopefully this clears up some of the confusion & demonstrates the degree of research I did on the whole subject.

Ok, so std rear is 150/80/17 so the profile height is 80% of 150mm = 120mm. Wheel & tyre diameter in mm = 17x25.4mm = 431.8mm (wheel) plus 2x120mm (tyre) = 671.8mm.
Circumference = "Pi"x 671.8 = 2110mm

Alloy rear is 180/60/17 so the profile height is 60% of 180mm = 108mm. Wheel & tyre diameter in mm = 17x25.4 = 431.8mm (wheel) plus 2x108mm (tyre) = 647.8mm.
Circumference as above =2035mm

Difference is approx 3.5% downward. Probably not that noticeable, really, but the above calc for the alloy assumes you've got the 5.5" rear & not the 5" with a 170/60/17 tyre.

If you ever see a GS with alloys that's retained the crud-catcher on the FD, there's quite a difference in the clearance between it & the tyre... It's even more noticeable on the more current 180/55-17 tyre size & 190/55-17 falls about halfway between.