School Me on Rake and Ride Height

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discussion starter · #1 · jun 13, 2012

first i have an 08 1800f stock. please help me become better informed about changing the triple tree angle and rear shock length. i see 6,7, and 8 deg trees. i understand that it pushes out the front tire and will lower the bike some. the 6deg tree says it lowers about 2.5″. how much does the 7 and 8 deg trees lower the bike? explain to me how this affects the ride. if i lower the rear end with shorter shocks will it cancel out any ride changes. how low is too low, to where i could drag the bike? layman version welcome but i am an engineer so specifics and technical stuff is welcome too. links to other technical documents is cool as well. basically i need some schooling on how each change will affect the bike and by how much. thanks guys.

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i can’t help you with the info but there is a member here known as stump that is a master at the info you are seeking. he has a website: stumpwerx.com which may help or at least give you another way to contact him.

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discussion starter · #3 · jun 13, 2012

it looks to me the more deg angle or rake i add at the trees the smaller my trail gets which makes the bike more “squirrely”. can someone provide me with actual numbers. stock trail, 6deg trees = ? trail, 7&8 deg trees= ? trail. and if shorter rear shocks makes any difference. also how does fork extenders chagne any of this?

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rake and trail is definitely a science. by lowering the front end without lowering the rear can add significant instability to your ride. you can go as low as you want as long as that you properly configure the entire chassis. wheel size rear end height, fork length etc… all have an affect on the geometry of the ride.

here is a great rake and trail calculator that will assist you in determining those numbers, but with the vtx there is alot of tribal knowledge that will help you. doing just the math gets complicated.

rake and trail calculator

pm or email me if you have specific questions.

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discussion starter · #5 · jun 13, 2012

do you have the stock numbers for the 1800f for that calculator?

what i’m thinking is one of the raked trees (6,7,8) with no spacers and a shorter rear shock to lower the bike over all while still keeping basically stock riding characteristics.

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i do not know the stock numbers but for each one of the rakes it is different:

6* will only require you to lower the rear 11″ or more – 1-2″ extensions highly recommended.

7* i do not know

8* will require lower rear (11″) and a 21″ front wheel with extensions is required. since the “f” is a dual rotor wheel – wheels come at a cost.

the easiest setup for you is the 6* tree, shorter shocks and i recommend the extensions

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discussion starter · #7 · jun 13, 2012

why do you recommend extensions? what does it accomplish?

i want a low fat muscle look, less chopper.

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to level the look! not required but recommended

adds more stability in turns – especially if only going with 11″ shocks.

if you go with 10.5″ shocks it will be better!

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i have a 06 1800c with 6* trees, 21″ front wheel and 11.5″ rear shocks and the bike handles and corners awesome. i’m plannng on adding 2″ fork extensions though because my pegs are dragging in the corners. just want to add some hight in the front and it will also give a better overall look.

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i have a 06 1800c with 6* trees, 21″ front wheel and 11.5″ rear shocks and the bike handles and corners awesome. i’m plannng on adding 2″ fork extensions though because my pegs are dragging in the corners. just want to add some hight in the front and it will also give a better overall look.

adding the 21″ wheel to this setup is perfect and you did it all the way correct!!! you can get away without it but your rake number are probably;y very close to stock!

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let me see if i’ve got this right. i’m no expert, but i don’t mind pretending like i know what i’m talking about.

important thing to remember is that all measurements are based on the rear axle rotation point for hard tail bikes, and the rotation point for the swing arm on our soft tails. this means that everything starts with your rear shock length.

your personal weight will determine how short your rear shock can be. stock is 12.25″ on my bike.

shortening the rear shock will increase rake and trail.

rake is the angle between a vertical line dropped from the head of the neck to the ground and a line going through the head to the axle.

false trail is the distance on the ground between a vertical line from the axle to the neck/axle line extended to the ground.

true trail is the same measurement, but instead of on the ground it is to a point on the extended neck/axle line where the intersection angle is 90 degrees. this one is kind of hard to explain, so google true trail and read up on it.

near as i can figure the owner’s manual lists false trail, not true trail.

stock trail on the vtx is 6.4″ according to my manual.

increasing trail above stock makes the bike more stable at high speed, but harder to turn at low speed.

decreasing trail below stock makes the bike more shakey–kind of like a shopping cart wheel.

from what i’ve read you’ve actually got a 2″ window above and below the 6.4″ trail which is safe to be in.

cutting and welding a neck so it’s angle is increased beyond stock causes the trail to increase.

raked triple trees are designed to shorten the trail caused by increasing the neck angle on a front end.

using a raked triple tree without cutting the neck to increase the rake angle results in a reduced trail.

fork extensions are for the purpose of leveling the frame. they result in an increased trail and an increased rake.

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rule of thumb. there is a difference of 3/8″ of rise or fall in 1 degree per linear foot. or 1/32″ per linear inch at 1 degree of rise or fall.

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let me see if i’ve got this right. i’m no expert, but i don’t mind pretending like i know what i’m talking about.

important thing to remember is that all measurements are based on the rear axle rotation point for hard tail bikes, and the rotation point for the swing arm on our soft tails. this means that everything starts with your rear shock length.

your personal weight will determine how short your rear shock can be. stock is 12.25″ on my bike.

shortening the rear shock will increase rake and trail.

rake is the angle between a vertical line dropped from the head of the neck to the ground and a line going through the head to the axle.

false trail is the distance on the ground between a vertical line from the axle to the neck/axle line extended to the ground.

true trail is the same measurement, but instead of on the ground it is to a point on the extended neck/axle line where the intersection angle is 90 degrees. this one is kind of hard to explain, so google true trail and read up on it.

near as i can figure the owner’s manual lists false trail, not true trail.

stock trail on the vtx is 6.4″ according to my manual.

increasing trail above stock makes the bike more stable at high speed, but harder to turn at low speed.

decreasing trail below stock makes the bike more shakey–kind of like a shopping cart wheel.

from what i’ve read you’ve actually got a 2″ window above and below the 6.4″ trail which is safe to be in.

cutting and welding a neck so it’s angle is increased beyond stock causes the trail to increase.

raked triple trees are designed to shorten the trail caused by increasing the neck angle on a front end.

using a raked triple tree without cutting the neck to increase the rake angle results in a reduced trail.

fork extensions are for the purpose of leveling the frame. they result in an increased trail and an increased rake.

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wow – you really did your home work! lol!

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wow – you really did your home work! lol!

yea, i know, overkill. i had to drag out my old trig textbook to work out the numbers, and had to fight excel to make it all work. in the end i learned a lot about the engineering dynamics, but i never could get the spreadsheet to match the rake and trail calculator at rb racing. it would come close on some numbers, but not on others.

i did work out what i thought was an interesting bit of engineering. i figured out what the impact would be with a 10.5″ rear shock, a six inch raked triple tree (with zero neck change), a two inch fork extension, and both a 21″ and a 23″ front wheel. this was the configuration big-x recommended i buy. i posted the resulting rake and trail on his forum, then he cut me off. i can’t even read the posting–if it’s still there. seems to me that it ended up being a 42 degree rake with a 2-3″ trail, but i can’t remember.

i have the worksheet, but i didn’t label the cells so i can’t figure out what each cell does. one of these days i’ll step through the process again and document it more clearly.

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i figured out what the impact would be with a 10.5″ rear shock, a six inch raked triple tree (with zero neck change), a two inch fork extension, and both a 21″ and a 23″ front wheel. this was the configuration big-x recommended i buy. i posted the resulting rake and trail on his forum, then he cut me off. i can’t even read the posting–if it’s still there. seems to me that it ended up being a 42 degree rake with a 2-3″ trail, but i can’t remember.

i have the worksheet, but i didn’t label the cells so i can’t figure out what each cell does. one of these days i’ll step through the process again and document it more clearly.

i’m tryin to work out the numbers on a similar setup. i already have the numbers run for a 23″ or 26″ front wheel with different combinations of raked trees and extensions. unfortunately, they are based on stock numbers for the rear and i already have 10.5″ shocks. i’m trying to figure out how to adjust the numbers to reflect that.

can you email me that worksheet? even of you didn’t label the cells, i might be able to reverse engineer it to figure it out.

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tho some will disagree, what works on a 1300 does not directly apply to a 1800. very different animals. personally i would not go more than 6* with a 1800 and that is with the lowered rear, 21″ front wheel and extensions. when you are talking about being able to easily go well over 125 mph you will need all the trail you can get on the 1800. the 1300 can not go over that speed (yea i know some you think it can) and the weight distribution is very different than the 1800. the 1300 is better suited for more rake without cutting the neck. not to mention it costs way less to rake a 1300. hell just the extended braided brake lines for a 1800 cost more than most of the overall cost of raking a 1300.

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hey capt, have you ever ran the trail numbers for your bike with a 23 or 26 front wheel?

on a side note, do you have a link to a thread that discusses how you adapted the fork covers to work with your extensions?

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hey capt, have you ever ran the trail numbers for your bike with a 23 or 26 front wheel?

on a side note, do you have a link to a thread that discusses how you adapted the fork covers to work with your extensions?

never really considered a 23″ or 26″, but might be worth looking into if and when i go with different wheels. would have to go with a different front fender too, or i guess i mod mine to work with the big wheel.

as for my fork tins there is info in this thread. basically i made new lower tins.

http://www.vtxcafe.com/showthread.php/31931-face-lift-for-my-x

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