BTS How to ??

[Bobby Buggs]

I don’t feel as if I’m technically challenged but I really don’t know the how and why of adjusting the BTS.

Can we make this thread about why and how you adjust your BTS, like what does Preloading actually do to the way you ride and if you really want forward lean how do you get it ect

Thanks,

[kjl]

I think it's actually pretty simple to adjust, even if you are an anal nerd like me. You only have two things that you need to keep in mind:

1) Adjusting the neutral position (i.e. where the boot wants to be if you are not actively flexing it). I believe most people tuned this to be where they kept their old boots locked with the old 5-position adjuster.

2) Making sure that, at the most forward lean you would expect the boot to flex as you ride, the bottom spring is still under at least a little bit of compression.

In practice, I think you just do these steps:

1) apply BTS with nuts all the way out (i.e. top nut as high as it goes and bottom nut as low as it goes)

2) if you want more forward lean, tighten (raise) bottom nut. If you want less forward lean, tighten (lower) the top nut.

3) If the nuts are still really far away and you worry that the bottom spring may uncompress completely and go loose during a lot of forward flex, then you can tighten both nuts a little bit, and repeat step 2.

Nerdy note for the nerdy nerds out there: It's been a while since my engineering classes, but I believe:

Springs apply force linearly proportionally to the distance from its equilibrium length. As long as both springs are compressed, the force to return to neutral with the BTS is just (k1+k2)*X (where k1 and k2 are the spring constants of spring 1 and 2, and X is the distance from the neutral position). This means that:

1) Preloading your springs more or less will not affect the response of the BTS - if you want a stiffer spring response you actually have to switch springs.

2) if you have one blue spring and one yellow spring, it doesn't actually matter which one you have on top and which you have on the bottom - the BTS response is the same. Unintuitive, and interesting! But it means that if you wanted a stiffness somewhere between the yellow and blue springs on both your boots, you can buy only one blue set and only one yellow set, and have one boot have yellow on top and the other have blue on top, and both boots should behave the same (although the positions of the BTS nuts will be quite different to achieve the same neutral position).

[martyagt4]

Don't forget about coil bind. If it's preloaded enough, you'll just shoot the rate to infinity, then you are relying on the flex of the boot cuff.

[Bobby Buggs]

So yellow on top and blue on the bottom with the nuts in the same position as blue and blue will = the same result?

I felt yellow on top and blue on the bottom would allow easier forward flex but keep the rear flex a bit more firm:o

[kjl]

So yellow on top and blue on the bottom with the nuts in the same position as blue and blue will = the same result?

I felt yellow on top and blue on the bottom would allow easier forward flex but keep the rear flex a bit more firm:o

No, you'd have to put the nuts in different places, but once you've tuned the nuts so that the neutral position is the same, a blue/yellow is the same as yellow/blue. Weird, but the math is straightforward.

[KingCrimson]

Wouldn't the linearity of the flex change in some situations?

Assuming you have an extremely soft toeside spring,

Errrr....

Interrupting myself here..

It all make sense. Haha thanks Ken. BTS is definitely a blast to play with and use!

[RCrobar]

Interesting post Ken, I enjoyed reading the nerd information!

It never ceases to amaze me how riders come to different conclusions when setting up carving gear to best meet their needs; a lot of ways to skin a cat comes to mind and/or highly biased opinions.

Case and point:

3) If the nuts are still really far away and you worry that the bottom spring may uncompress completely and go loose during a lot of forward flex, then you can tighten both nuts a little bit, and repeat step 2.

When reading this part of your post it surprised me that you were trying to eliminate a space in the spring set up. I have gone out of my way to create a space between the upper and lower springs and have tried to determine the size of the space that felt best for me.

I personally do not want the lower spring affecting the upper spring; I want very different spring resistance for a heel side vs. a toe side turn. So, for me which spring is placed on the top vs. the bottom is very important and does make a difference.

Thanks for your post; it got the gray matter going!

Rob

[Hans]

I personally do not want the lower spring affecting the upper spring; I want very different spring resistance for a heel side vs. a toe side turn. So, for me which spring is placed on the top vs. the bottom is very important and does make a difference

Hi, Rob

I am supposed to think you are talking here about your Northwave spring setup? If that's the case you can't make an equal comparison with the BTS system;) With the Northwave system there is a stick divider in between the two spring setup (or even three springs) with the Northwaves. The BTS system doesn't have this: the springs are just on top of each other without any (internal) divider.

[RCrobar]

Hi Hans

I am supposed to think you are talking here about your Northwave spring setup? If that's the case you can't make an equal comparison with the BTS system With the Northwave system there is a stick divider in between the two spring setup (or even three springs) with the Northwaves. The BTS system doesn't have this: the springs are just on top of each other without any (internal) divider.

1000 apologies as I have been comparing the Northwave spring system to the BTS system, I should have stated this! I have only seen web pictures of the BTS and was convinced the two systems were a very similar design. Please excuse this error! I guess if I owned a BTS the next modification I would be experimenting with would be an internal divider in the BTS housing ... this in turn would lead to more highly biased opinions;)

I found this old thread, it has A LOT of different spring pictures for anyone interested:

http://www.extremecarving.com/forum/viewtopic.php?t=3631&start=0

Cheers

Rob

[Steve Prokopiw]

I think it's actually pretty simple to adjust, even if you are an anal nerd like me. You only have two things that you need to keep in mind:

1) Adjusting the neutral position (i.e. where the boot wants to be if you are not actively flexing it). I believe most people tuned this to be where they kept their old boots locked with the old 5-position adjuster.

2) Making sure that, at the most forward lean you would expect the boot to flex as you ride, the bottom spring is still under at least a little bit of compression.

In practice, I think you just do these steps:

1) apply BTS with nuts all the way out (i.e. top nut as high as it goes and bottom nut as low as it goes)

2) if you want more forward lean, tighten (raise) bottom nut. If you want less forward lean, tighten (lower) the top nut.

3) If the nuts are still really far away and you worry that the bottom spring may uncompress completely and go loose during a lot of forward flex, then you can tighten both nuts a little bit, and repeat step 2.

Nerdy note for the nerdy nerds out there: It's been a while since my engineering classes, but I believe:

Springs apply force linearly proportionally to the distance from its equilibrium length. As long as both springs are compressed, the force to return to neutral with the BTS is just (k1+k2)*X (where k1 and k2 are the spring constants of spring 1 and 2, and X is the distance from the neutral position). This means that:

1) Preloading your springs more or less will not affect the response of the BTS - if you want a stiffer spring response you actually have to switch springs.

2) if you have one blue spring and one yellow spring, it doesn't actually matter which one you have on top and which you have on the bottom - the BTS response is the same. Unintuitive, and interesting! But it means that if you wanted a stiffness somewhere between the yellow and blue springs on both your boots, you can buy only one blue set and only one yellow set, and have one boot have yellow on top and the other have blue on top, and both boots should behave the same (although the positions of the BTS nuts will be quite different to achieve the same neutral position).

#2 would negate the feature of being able to have different spring siffnesses all together.Why even have dfferent springs? I have found that my front and rear boots act significantly different with a softer blue spring on the lower on the front boot and a stiffer red on the rear boot.They also behave differently with a softer blue upper on the rear boot and a stiffer red upper on the front boot.I have ridden this combo several days now and it is different than it was with the opposite positions for front and rear with a similar amount of preload and forward lean.I have since settled on more forward lean on the rear boot.

[RCrobar]

The BTS system doesn't have this: the springs are just on top of each other without any (internal) divider.

Is anyone able to post a picture(s) of a BTS that has been disassembled?

Fin, could you help out here?

Thanks in advance for doing this.

Rob

[KingCrimson]

Hi, Rob

I am supposed to think you are talking here about your Northwave spring setup? If that's the case you can't make an equal comparison with the BTS system;) With the Northwave system there is a stick divider in between the two spring setup (or even three springs) with the Northwaves. The BTS system doesn't have this: the springs are just on top of each other without any (internal) divider.

Are you sure? I don't think that the springs would do anything without an internal divider. Also, Ken's posts would not make any sense if there was no divider.

[Hans]

Now, I am mistaken, there is a divider in the BTS I just got the top spring out.

[KingCrimson]

So I'm not crazy..good. That Northwave picture is exactly how the BTS looks then.

[RCrobar]

No problem at all Hans.

Thanks for taking your BTS apart and checking, I thought I was loosing my mind as it generally is the first thing to go:)

Merry Christmas

Rob

[KingCrimson]

How do you take the BTS apart anyway? I pulled the preload nut off the top and the spring didn't want to move.

Do you remove the threaded rod, or just fight the spring?

[Hans]

How do you take the BTS apart anyway? I pulled the preload nut off the top and the spring didn't want to move.

Do you remove the threaded rod, or just fight the spring?

Don't get it. If you take of the topnut, you can simply take out the topspring.

If you want to take out the lower spring, you have to disassembly the whole thing.

[KingCrimson]

Haven't tried taking it apart really, just noticed that the spring didn't want to come out. I bet it would get pushed out if I flexed the boot..

[fin]

Great thread idea Bobby! We do get some questions on the BTS now and then so maybe we can get them answered here.

Set-up:

One thing we recommend is to mark on your boots the "home" position you currently like BEFORE you remove the stock locking mechanism. I usually do this with a Sharpie pen on the lower part of boot and draw a line along the line of the upper cuff.

Then install the BTS and move the Nuts up and down until you have the Cuff lined up with this mark. Now at least you are starting at the same spot as the stock set-up.

Two rules on the Nuts:

1) move them BOTH up and down to effect forward lean position

B) move the Nuts TOWARDS or AWAY from each other to effect preload

Preload = the amount the spring is loaded in its static position

Preload is good and we recommend have at least a small amount to have tension on the Nuts at all time.

If you have so much pre-load as the springs are almost compressed to a solid then you need to move up to the stiffer spring.

You guys are correct, the Forward lean position WILL change as you mover one of the nuts. But keep in mind the springs are apposing each other but they are at very different spring rates. So if you move the Top Nut down say 1/2" (12.7mm for our Euro friends) then the lower spring may only compress 1/4" (6.35mm). This happens because the lower Spring (heel side) is approximately twice (if the same color) the stiffness as the top spring (toe side). This effect is compounded when you mix colored springs. Absolutely not a big deal but you do need to be aware of this.

Kjl: not totally correct. A Blue(top)/Yellow(bottom) will NOT feel the same as a Yellow(top)/ Blue(bottom). When you are actually in the turn and compressing one or the other spring the not compressed spring is no longer in in effect after it goes to free length.

KingCrimson: Once you remove the Top Nuts the top spring will just slip off the shaft. However, to remove the lower spring you do need to remove the Top Pin that holds the Upper Case into the boot. Let me know if you still have an issue with it.

Below is a diagram of the BTS to help understand what is going on with it. Sometimes it is hard to see what is going on especially if you have the same color springs, they look like on big long spring! There is a divider in the Upper Case.

[RCrobar]

Hey Fin

Preload is good and we recommend have at least a small amount to have tension on the Nuts at all time.

Why?

Is the pre-load to keep the upper and lower nut from moving, due to vibrations etc., while riding?

Thanks for posting the BTS pictures.

Rob

[jp1]

I ordered the BTS but have not received them yet. I ordered all Blues because they are the 'mid' range springs. Can anyone measure the ID, OD and wire thickness of either of their springs and post ? I have access to some die springs and would like to get a assortment of springs with different rates for trial when the BTS arrive. Thanks in Advance-jp.

[Ladia]

I am using die springs with OD .625" and IN about .4". Also I am also using much softer springs. If you put than on Head boots do not forget boots modification per Arnaud or I wrote something about how to install them on TahoeCarvers.com. Leaving in 30 minutes for Kirkwood.

[jp1]

RCrobar, Preload

Hey Fin

Quote:

Preload is good and we recommend have at least a small amount to have tension on the Nuts at all time.

Why?

Is the pre-load to keep the upper and lower nut from moving, due to vibrations etc., while riding?

Rob, I can't answer for Fin, but I do know that compressioin springs are designed to have a certain amount of preload on them to keep them within their 'working range'.

As you stated, I think an added bonus of the preload would be to help keep the nuts form backing off.

[Bobby Buggs]

Great stuff:biggthump, any more???

[fin]

Rob,

Main reason for having a bit of pre-load on the springs is to just keep the top and bottom nuts from turning. Preload keeps them in their place. Not to mention a spring rattling like a spur as you walk around ;)

Also, (just my opinion) to get a move linear feel from the set-up you would not want the "dead zone" or no feeling from the BTS when the spring was not yet engaged as you took up the slack.

You see preload in most compression spring application for just these reasons: a cars struts and engine valve springs for example. Preload makes the spring linear and predictable.