Didn't someone here have a rake/trail calculator or formula?
#1
09-19-2008, 06:42 PM
Didn't someone here have a rake/trail calculator or formula?
I thought I remember someone performing some calculations before on changes...
I have the 03 fxdl shown below. I bought 3 degree trees with +2" fork tubes. I am planning on running a 160 tire in the rear on a 16 inch wheel.
The front will have a 21inch wheel and a 100(?) tire. (this isn't set in stone as I haven't checked to see what's typical for this size wheel)
Can anyone run this through the system and see how things will work out? I also have a set of 11" progressives for the back I'd like to use if it doesn't throw things too far out of whack.
Any help is appreciated!
I have the 03 fxdl shown below. I bought 3 degree trees with +2" fork tubes. I am planning on running a 160 tire in the rear on a 16 inch wheel.
The front will have a 21inch wheel and a 100(?) tire. (this isn't set in stone as I haven't checked to see what's typical for this size wheel)
Can anyone run this through the system and see how things will work out? I also have a set of 11" progressives for the back I'd like to use if it doesn't throw things too far out of whack.
Any help is appreciated!
Last edited by timberwolfz28; 09-19-2008 at 06:44 PM.
#3
09-19-2008, 07:27 PM
Thanks, using that calculator, and figureing a 90/90-21 tire, I will be down to 3.46" trail.
But there is no provision for adjusting the rear suspension in the calculations. That being said, a shorter rear shock (11") should increase the trail.
Is that correct?
Also, what tire size is typical for a 21" front wheel?
But there is no provision for adjusting the rear suspension in the calculations. That being said, a shorter rear shock (11") should increase the trail.
Is that correct?
Also, what tire size is typical for a 21" front wheel?
#4
09-19-2008, 07:55 PM
Now I am even more confused. Upon rereading that site, it shows raked trees as bringing the tire back toward the bike instead of pushing it away.
For example, a 3 rake would subtract 3 degrees from the head tube angle.
This doesn't make sense to me. Is their site incorrect?
If I rerun the calculator and use -3 for the tree rake (effectively moving the front tire AWAY from the bike by adding 3 degrees to the head tube angle), it changes my trail to 7.89
For example, a 3 rake would subtract 3 degrees from the head tube angle.
This doesn't make sense to me. Is their site incorrect?
If I rerun the calculator and use -3 for the tree rake (effectively moving the front tire AWAY from the bike by adding 3 degrees to the head tube angle), it changes my trail to 7.89
Last edited by timberwolfz28; 09-19-2008 at 07:59 PM.
#6
09-20-2008, 12:28 AM
Now I am even more confused. Upon rereading that site, it shows raked trees as bringing the tire back toward the bike instead of pushing it away.
For example, a 3 rake would subtract 3 degrees from the head tube angle.
This doesn't make sense to me. Is their site incorrect?
If I rerun the calculator and use -3 for the tree rake (effectively moving the front tire AWAY from the bike by adding 3 degrees to the head tube angle), it changes my trail to 7.89
For example, a 3 rake would subtract 3 degrees from the head tube angle.
This doesn't make sense to me. Is their site incorrect?
If I rerun the calculator and use -3 for the tree rake (effectively moving the front tire AWAY from the bike by adding 3 degrees to the head tube angle), it changes my trail to 7.89
#7
09-20-2008, 07:57 AM
The site is correct and the calculation works. I have no idea were you are seeing or getting that positive raked triple trees move the tire closer. The rear suspension drop will in effect change the neck angle, and so does shortening and lengthening the front end. You will have to measure all this set up and done or frame mocked up as a done set up to get correct measurements for calculations.
the 'raked' tree (red line) measurement line is shorter then the standard (black) line measurement. In the text, they say a raked tree is used to bring the trail back in line when an excessively raked head tube is used.
For chassis that have been raked to 40 degrees or more and too much trail is present, Raked Triple Trees are necessary.
all that being said, I think even using -3 to trick their calculator still has an inherent math flaw.
doing some research, I found the DWG has a 3 degree raked tree with 2" over fork tubes. same setup as I am using. So I am not worried about it.
Last edited by timberwolfz28; 09-20-2008 at 08:00 AM.
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#8
09-20-2008, 08:11 AM
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go to my site
To understand rake and trail you may go HERE as I work it up on a FL.
You can download your own rake and trail calculator HERE and you can get all tire measurements HERE . This is all you need. You may also change the numbers to see what effects alterations make.
You may also go to my Do-IT-YOURSELF page for all including more information you may need.
You can download your own rake and trail calculator HERE and you can get all tire measurements HERE . This is all you need. You may also change the numbers to see what effects alterations make.
You may also go to my Do-IT-YOURSELF page for all including more information you may need.
#9
09-20-2008, 10:46 AM
pretty simple actually. look at the picture they show...
the 'raked' tree (red line) measurement line is shorter then the standard (black) line measurement. In the text, they say a raked tree is used to bring the trail back in line when an excessively raked head tube is used.
Finally, USE the calculator... try it first with a zero degree triple tree, then again with a 3 degree. you'll see it shortens the trail calculation when you 'add' rake.
all that being said, I think even using -3 to trick their calculator still has an inherent math flaw.
doing some research, I found the DWG has a 3 degree raked tree with 2" over fork tubes. same setup as I am using. So I am not worried about it.
the 'raked' tree (red line) measurement line is shorter then the standard (black) line measurement. In the text, they say a raked tree is used to bring the trail back in line when an excessively raked head tube is used.
Finally, USE the calculator... try it first with a zero degree triple tree, then again with a 3 degree. you'll see it shortens the trail calculation when you 'add' rake.
all that being said, I think even using -3 to trick their calculator still has an inherent math flaw.
doing some research, I found the DWG has a 3 degree raked tree with 2" over fork tubes. same setup as I am using. So I am not worried about it.
the fork is the raked tree line...
#10
09-20-2008, 12:38 PM
you and I must be seeing two different things. readin what's written on the bottom of the pictures, the shorter dimension line specifically says raked triple trees. The black line is indicated as the neck rake, as shown on the left side of the picture ans shown simply as 'trail' at the bottom of the picture.