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What is the proper rake & trail range for the SV650-S? Is there an ideal rake & trail? I would like to quicken the turn-in. Oh, and it's a track bike so no street application if that matters.
 

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What is the proper rake & trail range for the SV650-S? Is there an ideal rake & trail? I would like to quicken the turn-in. Oh, and it's a track bike so no street application if that matters.
Most people don't measure rake and trail, too hard to do consistently and accurately. They work instead with rear shock length, fork height relative to the top triple and/or height of a fixed point on the front of the frame to the ground.
 

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Stock rake is 25 degrees, stock trail is 100mm. Change one and you change the other. Like RichDesmond said, not easy to measure accurately. Again, like Rich said, work with the relative ride height front and rear. Raising the rear relative to the front and/or lowering the front relative to the rear will speed turn in at some cost to straight-line stability. Lowering the rear relative to the front and/or raising the front relative to the rear will slow turn in while increasing straight-line stability.

In the first case you are decreasing both rake and trail. In the second case you are increasing rake and trail. Relatively small changes make relatively large differences in feel. 3 to 5mm steps are usually recommended until you zero in on what works for you.

Folks have different likes and dislikes. You've got to try it out and see what fits you best.
 

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don't listen to this straight line stability crap some throw around.
you riding on track, your bike will be more stable with lowered front or raised rear or both. tank slappers and twitching actually comes from front been to high or rear squatting to much. it will also push wide in corners and front will lose traction sooner.
see what most racers use and take it for base set up. tune from there where you feel comfortable and bike does what you wanted it to do.
 

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You asked if there was an ideal setup, the answer is no. If you're asking that question it sort of implies that you may need some set-up help.

Per Veee's comment, it is true that on the track straight line stability is not as critical as it is on the street. Still, you want to avoid true tankslappers. A little head shake is a different matter, tolerable on the track.

The shorter the trail the more likely a two-wheeled vehicle will exhibit head shake or tank slappers. The higher the rear relative to the front, the steeper the rake gets and the shorter the trail gets. Less caster. (You also shorten the wheelbase when you raise the forks and/or lower the swingarm, but the change is very small).

Veee is half right. The lower the rear relative to the front the slower the bike will turn in ("push"). That's because as you lower the rear relative to the front the shallower the rake gets and the longer the trail gets.

http://en.wikipedia.org/wiki/Motorcycle_dynamics

There's a section on trail in that article.
 

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don't listen to this straight line stability crap some throw around.
you riding on track, your bike will be more stable with lowered front or raised rear or both. tank slappers and twitching actually comes from front been to high or rear squatting to much. it will also push wide in corners and front will lose traction sooner.
i think you are mixing up the effects of geometry change.

You can only reduce the rake so much. at some point the gyroscopic affect of the spinning front wheel will destabilize the bike making it unridable at higher speeds.

a bit of advice on motorcycle control. the most important performance portion of the bike are the tires because they are the first interface between the bike and the road. Next comes the suspension, then the chasis (geometry mods fall into this category), and finally the engine. If you want to improve the handling of your track bike:
1) put on GOOD tires
2) get a professional to set up your suspension
3) then futz around with the geometry.
 

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My experience is different.

In general, small changes in geometry make big changes in handling. Lowering the front just 5mm makes a difference you can immediately feel.

There's a toss up between tires and suspension, as long as the tires are not too old, worn out or worn oddly (e.g., flat spotted or flat around the circumference from running too many straight miles). The worse the road or track surface, the more important suspension becomes. The better the road or track surface the more important tires become.
 

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I bought this sv 4 months ago, its my first suzuki, i have been racing an f3 cbr and 05 ninja500 for a couple years. I have raised the rear end of each bike about an inch, transforming both bikes into cornering machines. I've been futzing around with the sv trying to get it set up right for me: a couple days ago i dropped the forks 3/4 inch: Holy $H*T did it dive, but the headshake was intolerable. i got back to the garage and measured the rake with my weight on it (i originally made the mistake of checking the rake while it was unloaded) it was at 17 degrees. STORY TIME IS OVER

Anyway i totally agree with you andy. The suspension become even more important the more difficult the surface. Also, as you said, it is necessary to have decent tires.

This is just from my track experience (some setups work well for some people and poorly for others) but let me explain my thoughts. Tires go through more changes in a shorter period of time (that effects handling) than any other portion of the bike. They are slaves to Air Pressure, Air Temperature, Surface Conditions, raw BHP, hard Braking. They have the short end of the stick; they take hard abuse. The basic Racers have to take into account Track Conditions and Personal preference when choosing tires. Hot tracks demand harder tires, otherwise the tires get slippery; Cooler tracks need softer tires or the tire wont be able to grip the surface as well. Twisty tracks usually want more air pressure in the tires so there is more sidewall tension and grip at lean angles. In contrast tracks with lots of straightaways use slightly less air pressure in the rear tire so there is a larger contact patch when it is upright allowing better straight acceleration. Less air pressure in the front tire helps braking for the same reason, but it is a bit of a disadvantage on twisty tracks because the front end moves a bit at hard lean. Finally, many track-worthy tires have heat cycles where their chemical composition changes after being exposed to the heat from racing then cooling from lack of use and repeating. The tires get harder and have less grip. The grip and shape of the tire can also be deformed by tire slides/spins, hard acceleration, hard braking, and extreme leans. My Michelin Pilowers (which work well on the track but dont go through heat cycles) take more wear in one racing season than my street tires do the entire year.

For the professionals (a status i am far from claiming) they have teams that set up a suspension to work with the tires for the conditions.

I can offer no guidance on this front. I dont understand Gold Valves, Damping Rods, or the effects of different weight oil viscosity on the front end. Its well worth the $50 at a track to get suspension guys to do this right.

I apologize for rambling. But its important to find what works for you.
 

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What is the proper rake & trail range for the SV650-S? Is there an ideal rake & trail? I would like to quicken the turn-in. Oh, and it's a track bike so no street application if that matters.
less than stock :)
the only way is to try, there are too many parameters affecting trail. first one to consider is sag: sv has 100-102 mm with stock sag numbers. if you put harder front springs usually trail increases: stock sag is about 40mm with a lightweight japanese rider on the saddle but 40mm are not a common sag with many aftermarket springs.....

i think it's a personal choice too. last month i was in front of a really fast sv ( team won italian supertwins championship ....) and measured the fork: it was more than an inch shorter than stock one + raising dogbones + longer shock !!!
probably riding that bike i wouln't be able to stay on the saddle for more than 2 bends :)
 

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i think you are mixing up the effects of geometry change.
no, I am not. try riding stock geometry at track at good pace and than try less stable one (theoretically) and you tell me which one is more stable.
you don't get tank slappers on brakes or in middle of corner, you get it when accelerating hard when front is fully extended and you just hitting bumps or road imperfections. second or actually first reason is rider giving input on bars that induce tank slappers.
if you go to far you can get same but in case of sv you can not go to far, at least not with stock front end. you can go to far with rear ride height which will create another problem, mostly on brakes and grip at rear.
theory is fine but in practice what you get on track is another story.
there is no stability issues with sv rear jacked up and front lowered. those that may have problem need riding lessons.
 

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Quote from Keith Code's Twist of the Wrist: “the process of head shake (which can be the beginnings of a tank slapper) begins when the tire hits a ripple and, along with the suspension, compresses. This throws the wheel slightly off-center. When the suspension and tire release, the wheel is light and flicks back toward a centered position, but again, slightly off-center. Still off-center when it loads again from the next ripple; again it is flicked past its centered position. The cycle of flicking back and forth repeats as the front-end seeks to stabilize through this automatic and necessary self- correcting process. Any bike will do it, and what most riders fail to realize is that this shake is a necessary part of the bike’s suspension system.” The wheel flicks at more extreme angles in relation to the road on bikes with small rakes than bikes with huge rakes (choppers). Example: MV Augusta uses steering dampers, OCC does not :)
 

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Quote from Keith Code's Twist of the Wrist: “the process of head shake (which can be the beginnings of a tank slapper) begins when the tire hits a ripple and, along with the suspension, compresses. This throws the wheel slightly off-center. When the suspension and tire release, the wheel is light and flicks back toward a centered position, but again, slightly off-center. Still off-center when it loads again from the next ripple; again it is flicked past its centered position. The cycle of flicking back and forth repeats as the front-end seeks to stabilize through this automatic and necessary self- correcting process. Any bike will do it, and what most riders fail to realize is that this shake is a necessary part of the bike’s suspension system.” The wheel flicks at more extreme angles in relation to the road on bikes with small rakes than bikes with huge rakes (choppers). Example: MV Augusta uses steering dampers, OCC does not :)
and what is there different than what I said?
reason it does on acceleration is because fork is extended and can not fall in hole behind bump. your wheel is in air.
 

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notice how it compares cruisers to sport bikes, not one sport bike to another, it is just in general. buel tank slaps less than sv and it has rake and trail much less.
 

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the general principle of chassis geometry is what he was going for.

the comparison between sport bikes and choppers was mine (not in quotes). 01 buell blast advertises 25 degree rake, wikipedia says the sv650 also has a 25 degree rake. however when they measure the rake, they measure it UNLOADED. once the rider gets on and the suspension compresses, the bike with the weaker front suspension drops more thus reducing the rake making it more prone to headshake and tank slappers - less stable.
 

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the general principle of chassis geometry is what he was going for.

the comparison between sport bikes and choppers was mine (not in quotes). 01 buell blast advertises 25 degree rake, wikipedia says the sv650 also has a 25 degree rake. however when they measure the rake, they measure it UNLOADED. once the rider gets on and the suspension compresses, the bike with the weaker front suspension drops more thus reducing the rake making it more prone to headshake and tank slappers - less stable.
buel blast :rolleyes:
check new buel 1125 with rake 21 degree and trail 84mm. older one was in same range. according to your book it would be headshake machine.
SV works great with rake around 23.5-24 and trail in mid 90's.
this thread is about sv taken to the track, in case you missed.
I have never read twist of the wrist and don't plan to. there is nothing in there that would be of interest to me.
 

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Keith Code's books and California Superbike offer great insight into how to properly ride and how all parts of the bikes interact. Its definitely worth checking out; it's a huge help to novices offering insight into the workings of the bike, thus producing a better rider with a better understanding of the sport and bikes.

(Kieth Code instructed Wayne Rainey... everyone has something to learn)
 

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Headshake and tankslappers are both resonant phenomena, and the dynamics can be different with the same results. Rake is not as important as trail in this particular case. They both can occur on perfectly smooth surfaces.

What happens is that some force (can be gyroscopic precession on the front wheel or a bump or the rider bumping the bars, etc.) pushes the front tire right or left. Trail (caster) tries to pull the front end back straight. Instead of going back straight the front end may "overshoot", swinging to the other side. Now it tries to straighten again. The process may be slight and taper off, or it may be self-reinforcing, overshooting farther with each oscillation. The "stiffness" of the system (everything on the front end, including the rider's arms that can resist turning), the masses and their locations (early radial calipers on MotoGP bikes were really bad for this), front/rear weight distribution, all affect what happens.

One way to kill headshake (if it isn't too strong) is simply to brace yourself on the bike and stiffen your arms (pretty much what a damper does). This changes the natural resonant frequency of the front end left-to-right and can stop headshake immediately. Another way is to hit the front brakes. Again, changes left-to-right "stiffness" and natural frequency.

It's not simple. I've seen cases where adding a damper to a relatively stable bike made headshake worse, but that's pretty rare.
 
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