4” Stretched gearing?

[Klutch556]

Alright guys, I’ve searched and searched but can’t find an answer I can wrap my dense lil skull around.
im adding a 4” over swingarm to the bird and am trying to figure out if I need to drop my ratio or leave it alone.
I guess my question is after I stretch it what ratio do I need to keep “feeling” like the stock ratio.

 

[Mr Brown]

Longer wheelbase will let you accelerate harder without coming up. Go -1/+2

 

[Klutch556]

Longer wheelbase will let you accelerate harder without coming up. Go -1/+2

So is that down one in the front AND up 2 in the rear or is it down one OR up two?
Would goin down one and not go up two reduce the wheelies?

 

[SSGT_B]

The gear don’t reduce the wheelies, the longer wheelbase does. The gearing makes up for the increased load by reducing the final drive. Hence faster acceleration. Also makes it easier to low the tire off at the line if you are not using a sticky tire

 

[busakiller]

Details on bike and rider weight? You looking to do roll racing or street dig? Or just fun riding?

 

[Klutch556]

Details on bike and rider weight? You looking to do roll racing or street dig? Or just fun riding?

260lb mostly roll ons and long rides across state lines.

The gear don’t reduce the wheelies, the longer wheelbase does. The gearing makes up for the increased load by reducing the final drive. Hence faster acceleration. Also makes it easier to low the tire off at the line if you are not using a sticky tire

Gotcha, does one changing one sprocket or the other apply power differently? I feel like I read somewhere before that goin up in the rear adds more torque than down one in the front? But I can’t find where I read that now.

 

[Kevin Jones]

For rolls, I don't know that its all that important. Your enemy is spin. There is no difference between power other than i think i heard 1 down up front is the same as 2 or 3 up in the rear. Why not just leave the front and go up 2 in the rear. It will be fine for the longer rides.

 

[Mr Brown]

260lb mostly roll ons and long rides across state lines.

Gotcha, does one changing one sprocket or the other apply power differently? I feel like I read somewhere before that goin up in the rear adds more torque than down one in the front? But I can’t find where I read that now.

Going down in the front more than one puts the chain in a bind. That's the only functional difference. If you're 260 you should have geared it a long time ago!

 

[Johnnie Phatt]

first just adding a longer swing arm does not require a gearing change. Other than some weight there is no real difference to the bike. But you can certainly get benefits from making one
_1 +2 mean one tooth lower on the front sprocket up 2 on the rear sprocket Rule of thumb its this will raise your rpm about 700 rpm compared to going the same MPH with stock gearing
You can do just the front or just the back or both. Each individual change will raise the rpm in different amounts Both at once will give you the most of change of the three combinations Also you should be able to keep your stock chain length.
Gearing changes and lengthening the swing arm do not change the torque That is a function of the engine
However
It does improve the leverage that the engine has to use the torque. ie goes faster upon acceleration
Not that the bird is lacking acceleration but it will move the rpm that much further up in to the power zone for quicker response on roll ons and standing starts. if you are going to do roll on racing it is a highly desirable improvement
Depending on how far you go on a regular days riding you may or may not like the change The engine will be raving higher which my or may not bother you Sound and possibly vibration through the hands and feet may be more pronounced Although the Bird is pretty vibe free in my experience
The longer swing arm will help keep the from wheel on the ground or at least closer to it, unless you really light it up.
However 4 inches is not really all that far so there is a good chance it will come up some so be careful until you get use to how it affects your particular bike . The rear may spin unexpectedly from the lighter weight load on it. You will need to get use to the results through experimenting with throttle response. I would recommend caution as you discover how your bike reacts to the changes
You may notice a nicer ride with the longer chassis You may notice slower steering in the corners You will probably need to get stronger rear shock spring since the swing arm will now have more leverage than the stock springs were designed for. this can lead to the rear tire hitting the rear fender
4 inch extension is a nice mod. You get a lot of the benefits and less of the problems that a much longer arm can bring about
With out knowing a lot more about your current set up it is hard to predict exactly how the bike will respond Over all most people enjoy the small gearing change but you must be careful until you know for sure what your bike will do in various situations with what is basically now a faster accelerating bike. It will not replace a nitrous or a turbo system but it willl go faster
Hope this helps
JP

 

[Mr Brown]

For rolls, I don't know that its all that important. Your enemy is spin. There is no difference between power other than i think i heard 1 down up front is the same as 2 or 3 up in the rear. Why not just leave the front and go up 2 in the rear. It will be fine for the longer rides.

With a stock motor and 4 inch arm it ain't gonna spin. Adding gear still accelerates quicker, even from a roll. All other things being equal, if you and and go from a fifty roll, you in fifth gear and me in second what's gonna happen?

 

[Mr Brown]

By -1/+2 I meant go down one in the front, up 2 in the rear.

 

[Klutch556]

I really appreciate the info and advice here fellas. I think for now I’m gonna keep my front stock and go up +2 on the rear.
like I said, I’m a big boy and as such I'm focusing on droppin weight. Figure I’ll get more horsepower from the bike by droppin belt size lol.
also as I said before, it’s my first bike and has plenty of power for my skill level with my heavy ass on it. So I’m not looking to change anything too dramatically.
my next purchase is a ohlins suspension front/rear for my weight/stretch/ 1” lowering.

 

[Mr Brown]

I really appreciate the info and advice here fellas. I think for now I’m gonna keep my front stock and go up +2 on the rear.
like I said, I’m a big boy and as such I'm focusing on droppin weight. Figure I’ll get more horsepower from the bike by droppin belt size lol.
also as I said before, it’s my first bike and has plenty of power for my skill level with my heavy ass on it. So I’m not looking to change anything too dramatically.
my next purchase is a ohlins suspension front/rear for my weight/stretch/ 1” lowering.

I'm a big guy also. +2 is a good place to start, and weight loss is free.....
Excellent plan for the suspension. Couple of really good threads on it around here.

 

[busakiller]

did that come in a kit or did you buy it separately and what did you end up spending?

260lb mostly roll ons and long rides across state lines.

Gotcha, does one changing one sprocket or the other apply power differently? I feel like I read somewhere before that goin up in the rear adds more torque than down one in the front? But I can’t find where I read that now.

1 down and 2 up will be a good gear set up for your weight. If you were a lighter person I would say stock is best for roll racing.

 

[Kevin Jones]

Agree, he is a big man. I overlooked that aspect and im much smaller. Everything I have spins in rolls. Everything. I don't have anything only +4" tho. Anything I only went +4 with still came up annoyingly.

 

[Mr Brown]

When I weighed 260 the bike was 6 over, -1/+2, stock motor, prepped track, leaving at 6500 all but throwing the clutch, it would carry the front a little, set it down, pop it up and right back down on the 1-2 shift and that was it.

 

[Johnnie Phatt]

The rule of thumb is for every 7 pounds lost you have gained the Equivalent of 1 horse power
So If you can get from 260 to 239 you have given your bike 3 more horses because now it does not have to move your 21 extra pounds
as a bonus you have given your self a few more years of enjoying life
Now get down to 190 and you will have gained the equivalent of ten HP and women will be flocking to you