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Taller 5TH. gear
- Thread starter LCampbell
- Start date
I found a few threads, some old and some newer:
https://forums.bmwmoa.org/showthread.php?48013-Kayser-Tall-5th-Gear [ OK not Siebenrock but it's a tall fifth gear!]
https://forums.bmwmoa.org/showthread.php?96674-Long-5th-Gear
https://forums.bmwmoa.org/showthread.php?3536-Taller-5th-gear-A-OK-for-GS-s
https://forums.bmwmoa.org/showthread.php?48013-Kayser-Tall-5th-Gear [ OK not Siebenrock but it's a tall fifth gear!]
https://forums.bmwmoa.org/showthread.php?96674-Long-5th-Gear
https://forums.bmwmoa.org/showthread.php?3536-Taller-5th-gear-A-OK-for-GS-s
chasmrider
not lost til out of gas
I had Ted Porter install a taller 5th gear, when he rebuilt my trans, a couple of years ago. ( 1990 R100 GSPD ) It took me from 65 mph @4000 rpm to 70 mph @4000 rpm. I am very happy with the new gear, it makes a big difference when rolling through the wide open spaces, out here in the west. I didn't notice a big change in mileage, I get about 40mpg loaded and traveling.
stevenrankin
Active member
Maybe
I am very interested in this post for the reason that I have been considering my next engine rebuild on my 84 R80RT to go to a 1000cc jug with 40mm carb heads. Some of the posts regarding this change mention vibration and negative issues one being the R80RT final drive gearing is lower and the engine RPM is higher than would exist on a R100RT or RS. While this may or may not be an issue, only my conversion and time will tell, this changing the 5th gear to a higher gear may just address any issues which may crop up while still leaving the other gears alone with the final drive to give quickness along with better cruising.
The other alternative would be to do a full change of the final drive gearing and that would be more work as well as the additional pain of having to find a correct number speedometer to match the final drive. Added to the final drive issue is the R80RT has a drum brake rear end where the RT and RS have disc brakes. So, the cost would be either a rebuild with just the final drive and speedo in the drum brake system (if parts are available) or a swap out for final drive, conversion to disc brake. This means sourcing and paying for a good final disc brake drive, the disk, caliper, master cylinder, brackets and speedometer.
Ah yes, I am always fiddling either to keep the bike running or to make minor improvements in performance or handling but not to the extent of breaking the bank. St.
I am very interested in this post for the reason that I have been considering my next engine rebuild on my 84 R80RT to go to a 1000cc jug with 40mm carb heads. Some of the posts regarding this change mention vibration and negative issues one being the R80RT final drive gearing is lower and the engine RPM is higher than would exist on a R100RT or RS. While this may or may not be an issue, only my conversion and time will tell, this changing the 5th gear to a higher gear may just address any issues which may crop up while still leaving the other gears alone with the final drive to give quickness along with better cruising.
The other alternative would be to do a full change of the final drive gearing and that would be more work as well as the additional pain of having to find a correct number speedometer to match the final drive. Added to the final drive issue is the R80RT has a drum brake rear end where the RT and RS have disc brakes. So, the cost would be either a rebuild with just the final drive and speedo in the drum brake system (if parts are available) or a swap out for final drive, conversion to disc brake. This means sourcing and paying for a good final disc brake drive, the disk, caliper, master cylinder, brackets and speedometer.
Ah yes, I am always fiddling either to keep the bike running or to make minor improvements in performance or handling but not to the extent of breaking the bank. St.
LCampbell
New member
Thanks Kurt for looking up what information is available on this issue. I have considered changing the final drive & even tried finding one but never had any luck. Talked to Mike the mechanic at Ozzies BMW. He will be doing the conversion to the taller 5th. for me. Says he can do the work in one day if I bring in the transmission first thing in the AM
Visian
look out!!!
Part of the upgrades that were put on my 86 R80G/SPD+ was a Wüdo 5th gear, making it 6% higher. My rear drive is a 33/11, which is probably lower than your RT. I could really feel the difference while touring on the highway with the taller 5th, but I bet you'll get a fairly serious speeding ticket before you can feel the difference on your RT!
Siebenrock is an excellent supplier, though
