ADVrider

Go Back   ADVrider > Bikes > GSpot > Parallel Universe
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 05-19-2012, 09:01 PM   #1
Singletrack_mind OP
Cave Man
 
Joined: Aug 2008
Location: Northern New Mexico
Oddometer: 364
gearing for 18" rim

I'm thinking about building up a set of dirt rims for my GS800 so I can quickly swap from street-appropriate tires on the OEM wheels to full knobbies on an 18" rear and a 21" but narrower front. My question here is about gearing. The 18" rim with a knobby on it will be a bit bigger in diameter than the OEM setup, so I would need to lower the gear ratio via a larger rear sprocket or smaller countershaft sprocket just to maintain status quo. Ideally though, I'd want even lower gearing for the dirt so I could use 2nd gear more of the time; the stock gearing is a bit too tall in the dirt even with a 17" wheel.

I want to do this without exceeding the adjustment range on the chain tensioners so that swapping wheels is hopefully just a case of swapping wheels that have different sprockets. If I need to though, I could swap countershaft sprockets at the same time.

The stock gearing is 16/42. I'm wondering about leaving it that way for the street, and going to something like 15/43 for the dirt.

Has anyone else done this? Can you comment on what gearing choices you made?

Thanks!
Singletrack_mind is offline   Reply With Quote
Old 05-21-2012, 05:27 AM   #2
ebrabaek
Beastly Adventurer
 
Joined: Jan 2010
Location: El Paso,NM
Oddometer: 4,617
Here is what I did......
http://www.advrider.com/forums/showt...=759024&page=5

In summery.... the 45 was too much of a difference to me, and the bike although great in first.... were running too high rpm in 6'th....So I went back to a 42....still a tall first...but either sprocket would work within the stock tensioner, and chain on the bike....
__________________


Erling
ebrabaek is offline   Reply With Quote
Old 05-21-2012, 06:02 AM   #3
Singletrack_mind OP
Cave Man
 
Joined: Aug 2008
Location: Northern New Mexico
Oddometer: 364
Thanks E; I'd found that other thread before, and followed the links Wooody provided too. What I haven't seen is anyone else swapping back and forth from the 17" on the street to the 18" in the dirt and I've been wondering if it would be possible to pick good gearing for both without running out of adjustment room.

From your post though it sounds like I could put a 45T on the 18" wheel for dirt and revert to the 42T on the 17" for street and be happy. I don't care if I loose out on top speed when I have knobbies on.
Singletrack_mind is offline   Reply With Quote
Old 05-21-2012, 06:35 AM   #4
ebrabaek
Beastly Adventurer
 
Joined: Jan 2010
Location: El Paso,NM
Oddometer: 4,617
Quote:
Originally Posted by Singletrack_mind View Post
Thanks E; I'd found that other thread before, and followed the links Wooody provided too. What I haven't seen is anyone else swapping back and forth from the 17" on the street to the 18" in the dirt and I've been wondering if it would be possible to pick good gearing for both without running out of adjustment room.

From your post though it sounds like I could put a 45T on the 18" wheel for dirt and revert to the 42T on the 17" for street and be happy. I don't care if I loose out on top speed when I have knobbies on.
Yeppers.... You can.... at least with the stock chain on it..... I am an all mountain rider on a 7 inch 29'er, and share your like for single tracks...., and in my opinion.... the 18inch/45 combo makes for a great balance between average dirt road straights....and up and over's. If your unskilled in riding up and overs..... I would think two higher at 47 would be perfect....But I would have no fear at anything the bike could do with the 45...
__________________


Erling
ebrabaek is offline   Reply With Quote
Old 05-22-2012, 05:41 AM   #5
bodhizafa
How hard can it be?
 
bodhizafa's Avatar
 
Joined: Jan 2010
Location: Louisville, Co.
Oddometer: 631
I have a stock chain on with 15 front and 45 rear sprockets. 18 inch wheel too.
__________________
I'll have one if you do.....
bodhizafa is offline   Reply With Quote
Old 05-22-2012, 07:36 AM   #6
mousitsas
Beastly Adventurer
 
mousitsas's Avatar
 
Joined: Oct 2008
Location: Athens, Greece
Oddometer: 2,672
The difference between a 18 and a 17 rear, is 1 tooth on the front sprocket exactly.
mousitsas is online now   Reply With Quote
Old 05-22-2012, 07:35 PM   #7
Singletrack_mind OP
Cave Man
 
Joined: Aug 2008
Location: Northern New Mexico
Oddometer: 364
Quote:
Originally Posted by mousitsas View Post
The difference between a 18 and a 17 rear, is 1 tooth on the front sprocket exactly.


Good to know. That is virtually the same as adding 3 teeth on the rear: stock gear ratio with 16/42 sprockets is 2.625; running 15/42 yields 2.8, and running 16/45 = 2.813.

This would be great if I wanted to retain the stock effective ratio in the dirt, but I don't. I want it to be shorter. The OEM ratio is OK on the street, but too tall in the dirt. So, I might have to do something like this: stock 16/42 for the road; 15/45 dirt (3.0 ratio). That's a two tooth difference between the two set-ups, I'll have to go see if there is room in the chain adjusters for that.

Singletrack_mind screwed with this post 05-22-2012 at 07:53 PM
Singletrack_mind is offline   Reply With Quote
Old 05-22-2012, 10:03 PM   #8
mousitsas
Beastly Adventurer
 
mousitsas's Avatar
 
Joined: Oct 2008
Location: Athens, Greece
Oddometer: 2,672
Quote:
Originally Posted by Singletrack_mind View Post

Good to know. That is virtually the same as adding 3 teeth on the rear: stock gear ratio with 16/42 sprockets is 2.625; running 15/42 yields 2.8, and running 16/45 = 2.813.

This would be great if I wanted to retain the stock effective ratio in the dirt, but I don't. I want it to be shorter. The OEM ratio is OK on the street, but too tall in the dirt. So, I might have to do something like this: stock 16/42 for the road; 15/45 dirt (3.0 ratio). That's a two tooth difference between the two set-ups, I'll have to go see if there is room in the chain adjusters for that.
Check this site out
www.gearingcommander.com

You can play with sprocket sizes and check the resulting chain lengths
mousitsas is online now   Reply With Quote
Old 06-07-2012, 05:35 AM   #9
Singletrack_mind OP
Cave Man
 
Joined: Aug 2008
Location: Northern New Mexico
Oddometer: 364
Thanks for the input folks. As I was totaling the bill for this project and finding that it was going to push $2500 by the time I was done (including a new shock to help the back end work like it should off road), a used KTM 690 came my way and it just seemed like a better way to go. Even with great tires and suspension, the GS would still weigh 150lbs more than the KTM & that's huge.

I almost feel bad about backing away from pushing the 800 to it's limits, it is such a great bike and can be pushed amazingly far. I have had wonderful trips on it in the back country. In fact, it is BETTER than the 690 a lot of the time on a dual sport trip, but in those situations where it is too big, heavy and soft, the 690 just rocks.
Singletrack_mind is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 09:54 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014