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myballfro
05-01-2016, 8:20 AM
Is there a mathematical equasion for figuring out the right gearing for going to a bigger rear tire with a 77 ironhead motor?

Sky
05-01-2016, 12:22 PM
http://www.bakerdrivetrain.com/oldgearratios/rpmCalc.htm

http://www.nightrider.com/biketech/calc_gearratios.htm

myballfro
05-01-2016, 3:15 PM
Thanks
That will really help

Tattooo
05-01-2016, 4:20 PM
Gearing really depends on how and where you ride..... A calculator is for a bike that sits on it's kick stand......

farmall
05-01-2016, 4:59 PM
A calculator is for a bike that sits on it's kick stand......

Yep. The appeal of an HD is their crude, agricultural simplicity. They aren't some 50cc road racer with a tiny powerband.

Formula? Install tire. Ride motorcycle. In the unlikely event a gearing change from a tire swap is noticeable, change the sprocket of your choice. Stock gearing is low as fuck anyway to please test riders who want torqueful sensations.

bobscogin
05-01-2016, 5:04 PM
Gearing really depends on how and where you ride..... A calculator is for a bike that sits on it's kick stand......

That's true, but you can use math to arrive at gearing adjustments when tire diameter changes even for bikes that remain on the kick stand. I think that's where the calculators come in handy.

Bob

Tattooo
05-01-2016, 5:14 PM
That's true, but you can use math to arrive at gearing adjustments when tire diameter changes even for bikes that remain on the kick stand. I think that's where the calculators come in handy.

Bob

Do you really think 1 inch in tire size changes that much???? I bet in the real world of riding you can't really tell any difference......

Sky
05-01-2016, 5:25 PM
That's not what your girlfriend said, she loved that extra inch.

What if the dude went from a 130/80-16 to a 4.00 X 18 or even a 3.5 X 19 ?

Some people want to know the numbers before they spend money on such things. Not all of us have a hoard of used parts/tires to "slap" on and see what happens.

bobscogin
05-01-2016, 6:09 PM
Do you really think 1 inch in tire size changes that much???? I bet in the real world of riding you can't really tell any difference......

1" on a 26" tall tire, for example, is a 4% change. Some may not notice it, but I've made changes that equate to that and did notice. My point, in response to the original question, is that yes, the gearing adjustments can be calculated mathematically relative to the change in tire diameter. That's all he was asking.

Bob

Tattooo
05-01-2016, 7:17 PM
My point, in response to the original question, is that yes, the gearing adjustments can be calculated mathematically relative to the change in tire diameter. That's all he was asking.

Bob

But.... You know everyone has a but..... You highlighted what I said..... So your response was directed at me.... A 4% change would be less than one tooth...... I still say you will NEVER know that in the real world.....

Tattooo
05-01-2016, 7:21 PM
That's not what your girlfriend said, she loved that extra inch.

What if the dude went from a 130/80-16 to a 4.00 X 18 or even a 3.5 X 19 ?

Some people want to know the numbers before they spend money on such things. Not all of us have a hoard of used parts/tires to "slap" on and see what happens.

Yea that's why you give her two more.... LOL

Yea I guess it's nice having extra gears lying around...... But knowing what gears to run from years of riding is priceless....... But that comes with age I guess?????

Good luck with your gear search.......

FeHead
05-02-2016, 9:40 AM
Stroke it and tire size won't matter.

47str8leg
05-03-2016, 2:54 PM
But.... You know everyone has a but..... You highlighted what I said..... So your response was directed at me.... A 4% change would be less than one tooth...... I still say you will NEVER know that in the real world.....
I would beg to differ. I was running a 49 T sprocket on my pan-shovel. When installing a new chain I cut it 1 link short. Fuck me . Well I'll just change it out w/ the 48T sprocket I had lying around. I was surprised to find how much it changed my riding style . I always felt like the bike was never in the right rpm level in traffic. After a couple of months I bought another chain and put the 49 T back on my bike. Everything back to normal. Ahhhhhh......