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adjustable triple clamps for motocross..

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not sure if this was supposed to go here or in suspension forum, but given the fact that these parts change the complete geometry of the bike, i thought it would be better suited for here.

So. I see that alot (if not all) of the superbike guys are running adjustable triple clamps. When i say adjustable i mean that they can adjust rake angle, offsets, and pretty much any other geometry numbers associated with the front end of the bike just by making triple clamp adjustments. A good video toe explain what i mean is here..

my question is, are there any MX guys using these parts out there? I actuall have a set of these for my supermoto bike, and by looking at them im not sure if, just by the way they are designed, that they would withstand the forces involved with landing mx bikes that are not involved in superbike racing.

So, anyone know if MX guys are using this stuff or not??

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When i say adjustable i mean that they can adjust rake angle, offsets, and pretty much any other geometry numbers associated with the front end of the bike just by making triple clamp adjustments.
And when you say that, you are in error. Go back to 3:30 in the video and listen to what he says: "This changes trail, and nothing else."

If one sets the offset of the upper clamp differently than the lower, you can change the angle of the fork tubes, but that has no different effect on steering geometry than setting both clamps at the same number; it changes the trail. "Rake" (more accurately "steering axis angle", or steering head angle, or simply head angle) is not affected by such a change. In order to do that, you have to either raise or lower one end of the bike, or use steering head bearings with outer races ground off center.

frame.gif

But to answer your question, there are some adjustable offset clamps made (some KTM's came with clamps that could be set at either of two offsets), but not very many. Riders do often buy clamps built at alternative offsets. The results depend on the bike and how it's used.

Rekluse used to offer the "E-Axle", which is built with a 2mm eccentric offset, allowing the axle offset, and therefore the trail, to be moved within a range of +2 to -2 mm from normal.

Edited by grayracer513
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And when you say that, you are in error. Go back to 3:30 in the video and listen to what he says: "This changes trail, and nothing else."

If one sets the offset of the upper clamp differently than the lower, you can change the angle of the fork tubes, but that has no different effect on steering geometry than setting both clamps at the same number; it changes the trail. "Rake" (more accurately "steering axis angle", or steering head angle, or simply head angle) is not affected by such a change. In order to do that, you have to either raise or lower one end of the bike, or use steering head bearings with outer races ground off center.

frame.gif

But to answer your question, there are some adjustable offset clamps made (some KTM's came with clamps that could be set at either of two offsets), but not very many. Riders do often buy clamps built at alternative offsets. The results depend on the bike and how it's used.

Rekluse used to offer the "E-Axle", which is built with a 2mm eccentric offset, allowing the axle offset, and therefore the trail, to be moved within a range of +2 to -2 mm from normal.

hmmm...im not sure that i agree completely, but you have a good argument so correct me again if im wrong...

The rake angle of the bike is defined as the axis through the steering head. Most generally this is the exact same angle that the forks are at, because they are parallel.

If you offset the top triple clamp, from the bottom triple clamp, you change the angle of the forks, but you do not change the angle of the steering head.

Now the question becomes, is the correct rake angle now equal to the steering head axis angle, or the fork angle? Because rake is one of the most major factors in motorcycle design and tuning, I would say that the correct rake angle is now whatever angle the forks are at. This is because now that you have changed the angle of the forks, you are manipulated the steering geometry in a way that is going to affect the way the bike handles.

The steering head axis is always stationary, so if your saying that offsetting the top and bottom triple clamps forward and aft doesn't change rake angle, then your also saying that the rake angle of the bike can never be changed?

Constructive criticism is welcomed.

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We recently had this discussion in some detail:

http://www.thumpertalk.com/forum/showthread.php?p=10755198&highlight=rake#post10755198

"Rake" is a very old term, originally referring to the amount the front fork is bent forward, that is popularly misused in reference to motorcycles as synonymous with head angle, although in the truest sense, that is not the case. Changing fork rake independently of the head angle changes only the trail values, not the steering axis angles.

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The steering head axis is always stationary, so if your saying that offsetting the top and bottom triple clamps forward and aft doesn't change rake angle, then your also saying that the rake angle of the bike can never be changed?

Constructive criticism is welcomed.

Not rake, but steering head angle. They are not exactly one and the same - and for most intents and purposes we just assume head angle is a given constant associated with the frame of any model of bike.

That said though, as Gray already mentioned: the factory bikes use offset head bearings/races, which DO change the steering head angle. Additionally, race sag has a direct effect and, sliding the forks up and down in the triple clamps, or changing the preload on the forks also alters the working head angle.

The other factor is that under hard braking, or when you slide up right to the gas cap, the forks settle and the shock extends which naturally decreases head angle as you come into a corner, and vice versa as you accelerate out. It's possible to help a bike with geometry problems, by tuning the suspension to complement it's strengths. Lots of people have made the best of the new Honda frames by stiffening the forks and running a longer link on the back.

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The other factor is that under hard braking, or when you slide up right to the gas cap, the forks settle and the shock extends which naturally decreases head angle as you come into a corner, and vice versa as you accelerate out. It's possible to help a bike with geometry problems, by tuning the suspension to complement it's strengths.

And brake dive at the front can change the effective head angle in operation at that moment by a considerable amount, as much as 3-4 degrees or more, and can in fact do so to a fault, causing the steering to "tuck under" or "knife in" from entry to mid-turn.

Head angle can be changed without modifying the frame only by altering the front/rear ride heights, or by using offset bearings. No other method will actually change the axis on which the steering stem rotates.

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I would hate to be the poor sucker who has to install (offset bearings)! :bonk:

They do create an installation problem, no doubt. They have to be as precisely indexed as possible, with the eccentricity of the offset placed as near to zero degrees fore or aft as can be done. Otherwise, the steering axis becomes tilted off of the XY plane (to the left or right as viewed from the front).

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I'm no expert, but I have some experience working with setting up race bikes.

I'm personally not a fan of offset bearings as they don't really do enough. If you can get 1/2 a degree out of them, that's pretty darn good. Usually you would want a full degree of adjustment in the rake department to really make a difference that you can't make through changing other geometry.

One tip/trick is to put in a small race that the bearing can slip into, so it doesn't naturally turn when you install it. If you mess it up by as little as 1mm, it can effect the whole bikes geometry so getting it right on the bench is critical.

I use to race Ducati's a few years ago and due to homologation reasons, the 749R had adjustable rake and trail. There was a double eccentric steering tube which allowed a 23.5-24.5 degree rake change and a 36mm - 30mm offset (trail) change. It was a clever, very simplistic way of allowing the bike to be setup for the street and have the front raked out (24.5 degree/36mm offset) or be adjusted for quicker steering at high speed (23.5 degree/30mm offset). The rake change obviously made a difference as well since when you change the rake you also effect the trail.

Needless to say, when I moved over to dirt bikes, the first thing I did was research the manufacturers and what they are using for rake and trail. What I found is, everyone kinda does their own thing. The range is between 25 degree's and 30 degree's with everything in the middle, obviously purpose of bike depending. Dirt bikes don't have every much space around the steering stem to accomplish very much adjusting as I pointed out earlier. Putting the rake adjustment into the triple clamps can be done. Attack Performance makes superbike triple clamps that use blocks that mount inside the clamps themselves that the steering stem goes through. Those blocks can be machined with different rake and trail in mind. Its a pretty basic process, but nobody seems to have moved it over to dirt bikes and my guess is, the cost is just too high. Because of that cost element, it seems to me, keeping the rake where it is and focusing on the trail (offset) is what most everyone has been doing. As pointed out earlier, you can adjust rake through ride height as well, so its not like your completely stuck. Most aftermarket manufactures offer offset triple clamps, but very few are adjustable.

The last few years of KTM SX bikes come with 18/20mm offset triple clamps and the KTM "factory" clamps are 19/22 which lets me believe (guessing), KTM has figured out that 19 is what works good in supercross (quicker steering) and 22 works good on the outdoors (more stability) on their bikes with the stock rake. Every manufacturer seems to have a different rake, so when looking at aftermarket clamp's its good to probably buy one from somebody who has tested it in professional race applications.

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hmmm...im not sure that i agree completely, but you have a good argument so correct me again if im wrong...

The rake angle of the bike is defined as the axis through the steering head. Most generally this is the exact same angle that the forks are at, because they are parallel.

If you offset the top triple clamp, from the bottom triple clamp, you change the angle of the forks, but you do not change the angle of the steering head.

Now the question becomes, is the correct rake angle now equal to the steering head axis angle, or the fork angle? Because rake is one of the most major factors in motorcycle design and tuning, I would say that the correct rake angle is now whatever angle the forks are at. This is because now that you have changed the angle of the forks, you are manipulated the steering geometry in a way that is going to affect the way the bike handles.

The steering head axis is always stationary, so if your saying that offsetting the top and bottom triple clamps forward and aft doesn't change rake angle, then your also saying that the rake angle of the bike can never be changed?

Constructive criticism is welcomed.

I'm no expert, but I have some experience working with setting up race bikes.

I'm personally not a fan of offset bearings as they don't really do enough. If you can get 1/2 a degree out of them, that's pretty darn good. Usually you would want a full degree of adjustment in the rake department to really make a difference that you can't make through changing other geometry.

One tip/trick is to put in a small race that the bearing can slip into, so it doesn't naturally turn when you install it. If you mess it up by as little as 1mm, it can effect the whole bikes geometry so getting it right on the bench is critical.

I use to race Ducati's a few years ago and due to homologation reasons, the 749R had adjustable rake and trail. There was a double eccentric steering tube which allowed a 23.5-24.5 degree rake change and a 36mm - 30mm offset (trail) change. It was a clever, very simplistic way of allowing the bike to be setup for the street and have the front raked out (24.5 degree/36mm offset) or be adjusted for quicker steering at high speed (23.5 degree/30mm offset). The rake change obviously made a difference as well since when you change the rake you also effect the trail.

Needless to say, when I moved over to dirt bikes, the first thing I did was research the manufacturers and what they are using for rake and trail. What I found is, everyone kinda does their own thing. The range is between 25 degree's and 30 degree's with everything in the middle, obviously purpose of bike depending. Dirt bikes don't have every much space around the steering stem to accomplish very much adjusting as I pointed out earlier. Putting the rake adjustment into the triple clamps can be done. Attack Performance makes superbike triple clamps that use blocks that mount inside the clamps themselves that the steering stem goes through. Those blocks can be machined with different rake and trail in mind. Its a pretty basic process, but nobody seems to have moved it over to dirt bikes and my guess is, the cost is just too high. Because of that cost element, it seems to me, keeping the rake where it is and focusing on the trail (offset) is what most everyone has been doing. As pointed out earlier, you can adjust rake through ride height as well, so its not like your completely stuck. Most aftermarket manufactures offer offset triple clamps, but very few are adjustable.

The last few years of KTM SX bikes come with 18/20mm offset triple clamps and the KTM "factory" clamps are 19/22 which lets me believe (guessing), KTM has figured out that 19 is what works good in supercross (quicker steering) and 22 works good on the outdoors (more stability) on their bikes with the stock rake. Every manufacturer seems to have a different rake, so when looking at aftermarket clamp's its good to probably buy one from somebody who has tested it in professional race applications.

alright so now everyone has me thinking..somebody try and chime in and clear this up for me...

For chassis adjustments you have rake, steering axis angle, trail, ride height, and a plethora of other things like swing arm angle, rear shock angle, etc, etc...but my assumption here is that steering axis, rake, ride height, trail, and maybe wheel diameter are the meat and potatoes of chassis tuning.

So which ones are the most important and why. For example, is your fork angle (rake) something you want to tune, or do you just adjust it in order to adjust trail?

Same question for steering head axis. Do you adjust steering head axis just for rider preference, or is there more to it?

I really need either a book, or a project that can break down all of the different chassis geometry values for me and teach me what each one effects positively, negatively, and how they all interact with one another...any good ideas are welcomed.

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Most people wouldn't change rake and steering head angle independently. Not that you can't, it's just less than common.

Typically you use trail to affect weight bias, as well as steering response. Less trail puts the tire further out (less weight on the front), and swings the contact patch through a smaller arc, so you generally expect less trail = more stable / more trail = more responsive... though other chassis issues can definitely make this untrue. The normal parts for tuning this are triple clamps, fork lugs, offset axles... it's also affected by all of the other chassis changes.

Ride height, both static and in motion, is really the only way to tune steering head angle that is readily available to non-factory riders.

Steering head angle is also used to tune the F/R weight bias, but with steering head angle less angle means MORE weight on the front, AND a the contact patch swings through a smaller arc. Usually more steering head angle is equated to a more stable feel at speed, and tendency to wash out in corners, but just recently someone suggested that possibly I've gone too far in that direction with my ride height - and the resulting light front tire is actually making my bike less stable in small chop at speed. The normal Methods for tuning steering angle are with sag (front and rear), slipping the forks up and down, and compression/rebound balance - not to mention rider position!

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alright so now everyone has me thinking..somebody try and chime in and clear this up for me...

For chassis adjustments you have rake, steering axis angle, trail, ride height, and a plethora of other things like swing arm angle, rear shock angle, etc, etc...but my assumption here is that steering axis, rake, ride height, trail, and maybe wheel diameter are the meat and potatoes of chassis tuning.

So which ones are the most important and why. For example, is your fork angle (rake) something you want to tune, or do you just adjust it in order to adjust trail?

Same question for steering head axis. Do you adjust steering head axis just for rider preference, or is there more to it?

I really need either a book, or a project that can break down all of the different chassis geometry values for me and teach me what each one effects positively, negatively, and how they all interact with one another...any good ideas are welcomed.

Read this entire discussion and see if it helps:

http://www.thumpertalk.com/forum/showthread.php?p=10754539#post10754539

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For chassis adjustments you have rake, steering axis angle, trail, ride height, and a plethora of other things like swing arm angle, rear shock angle, etc, etc...but my assumption here is that steering axis, rake, ride height, trail, and maybe wheel diameter are the meat and potatoes of chassis tuning.

Well thats a pretty complicated list, lets make that easier to read and understand.

Rake/Trail/Wheelbase are all connected. When you adjust one, you will effect the other. These are also the three basic geometry tools that are used by tuners to alter how the bike handles. These are the "meat" of chassis tuning and everything else like ride height are only done to alter one of those three basic geometry parameters.

So which ones are the most important and why. For example, is your fork angle (rake) something you want to tune, or do you just adjust it in order to adjust trail?

Most tuners tread a fine line between stability and quick steering. You want the bike to steer quickly which equates to less trail and sometimes a steeper rake angle, but by doing those two things, you shorten the wheelbase AND the consequences is; the front end becomes twitchy. That twitchiness is compounded by the stiff suspension which most professionals have to run in order to get the right amount of boost off the big obstacles they deal with. To remedy these issues, tuners add devices like steering dampeners, which help to alleviate the twitchiness.

Rake angle can be changed by raising or lowering the rear end. You will notice "lowering links" which are available through many suspension houses and most SX/MX pro's use them. When you lower the rear, it gives you a few degree's of rake in the front, and that helps make the bike more stable. This way, the tuners don't necessarily need to change the rake on the steering stem, they can just lower the rear and it gives them a similar effect.

A lot of people don't understand the benefit of "squat" not just for rear tire grip (which is the most common thing people talk about) but also for raking out the front. Just riding the bike and the rear end squatting, gives you MORE rake angle since the forks are so stiff. On a street bike, the forks are so plush and the suspension so stiff since it has less travel, that you don't get that same effect. In the world of motocross, especially in supercross where most people use extremely stiff front springs and sometimes unusually soft rear springs, the rake is in constant flux as they ride.

I really need either a book, or a project that can break down all of the different chassis geometry values for me and teach me what each one effects positively, negatively, and how they all interact with one another...any good ideas are welcomed.

I have never found a decent geometry book that pertains directly to motocross/supercross. There are many books and web sites that go over geometry, but most of them are science books and not about practical knowledge. In the world of racing and building a better machine, practical knowledge is important, how each element effects and reacts to each other on dirt is completely different then how that same element effects or reacts on pavement. A twitchy front end in motocross/supercross can put the rider at great risk, where in roadracing for instance, won't effect them at all.

There is a whole lot more to learn as well, how sag, spring rates and the riders input effect geometry. How to change the weight bias of the machine through wheelbase, etc... The net result in all of this can be cloudy, just because you understand geometry and suspension, doesn't mean you can put everything together and make a bike which is amazing to ride. There is some black magic that the best tuners in the world have, mostly because they're so experienced and well verse in what works. This is why there are only a hand-full of professional tuners floating around the world. Sadly, a lot of them are sitting home these days due to budget cuts.

Anyway, I hope that helps ya. As I said earlier, I'm no expert, a lot of my verbiage is simplistic because the topic at hand is already pretty complex, so I try to push away the complexity and focus on the basics. Once you understand the basic's, you can get into frame harmonic's and flex characteristics, thats where the REAL fun begins! LOL :bonk:

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