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Discussion Starter · #1 ·
I remember someone telling me like that taller tire (190/60) and raising the rear with ride height is two completey different things. In my mine it sounds like the same thing at first taller tire is like raising the rear.....is this rite :banghead
 

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No.... raising the rear with a taller tire, raises the axle height ONLY. The swingarm to frame angle stays the same.

adding a shim to the shock (or cranking on the adjustable rear shock you have) does it by changing the swingarm angle, thus changing the rear ride height and the rear geometry as well.
 

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Your close but not quite there. Sure a tire does make the bike stand taller. But that doesn't change the "Ride Height" in reguards to the suspension. What I am saying is that every suspension component has a sweet spot. Thats where the bike and rider weight just start to move through the stroke of the suspension that can be dampend by rebound and compression gradually until fully compressed without any harsh spikes. So the initial part of travel/stroke can be plush enough to absorb small bumps without transmitting then directly to the rider. Racing and street have totaly differnt setups. But basicaly you don't want the initial stroke to be taken up by rider/bike weight leaving the suspension to only try not to bottom. Gotta run
 

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Just for clarification YES tire height does alter the geometry of the bike just like raising the rear ride height of the bike with a shim or shock adjustment does (just not as much change as making the adjustments at the shock mount). many times with a 190-60 or 190-55 tire RC riders actually back the ride height all the way down on their shock adjustment to help compensate for the increased rear ride height that the tire gives
 

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EvilTwin-05 said:
Your close but not quite there. Sure a tire does make the bike stand taller. But that doesn't change the "Ride Height" in reguards to the suspension. What I am saying is that every suspension component has a sweet spot. Thats where the bike and rider weight just start to move through the stroke of the suspension that can be dampend by rebound and compression gradually until fully compressed without any harsh spikes. So the initial part of travel/stroke can be plush enough to absorb small bumps without transmitting then directly to the rider. Racing and street have totaly differnt setups. But basicaly you don't want the initial stroke to be taken up by rider/bike weight leaving the suspension to only try not to bottom. Gotta run
Well that was just about the most confusing and completely inaccurate discription of "ride Height I have ever heard:p


Ride Height is the distance the bike sits off the ground, yep that is it,...pretty simple huh?

Spring rates control Sag. Sag is not used to determine ride height.

Now if you want to know about increasing ride height from the stock settings,...well then we have a different set of variables

Variable one increasing ride height via shock length. This only effects rear suspension however it does change front geometry. Extending shock length will increase swingarm angle which in turn effects rear tire grip as well as chain reaction(Packing) to the rear suspension. It also effects braking action (jacking)

Variable two; increasing ride height via taller tire Diam. This will also change front geometry but with out the swing arm angle change thus leaving the rear to act in a stock or standard manner. (not a good thing)


In Variable one, you can tune in or out the amount of forward grip as well as the amount of side bite you generate with the rebound and compression circuits. You can also control the amount of weight transfer that the chassis recieves from throttle inputs (anti wheelie)

If at all interested I can explain the detractors to too much/too little front ride height :woot:
 

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"Well that was just about the most confusing and completely inaccurate discription of "ride Height I have ever heard
" SP2Pilot.

First let me say thanks for taking my back on a previos thread. Now being two "A" type personalities (Racers) I am sure we are going to strongly disagree on some topic at some time. Maybe not today though.

SP2, I think we aren't far off from eachothers reply. Let me explain why. You say ride height is the distance the bike sits off the ground and sag has nothing to do with that. Not sure if your deffention is to the axel or frame doesn't really matter. OK thats cool, but I say what you call "ride Hieght" is ground clearance. Which I refer to as the hieght from the ground including static sag to the lowest point between the wheels unloaded. I refer to "ride height" as the height from the ground to this point loaded with rider and whatever gear/load. However not sure if we agree here but I use "my definition of ride height" to adjust dampening charactaristics for intial suspension travel. I also agree with everyother senario you mentioned.
I wonder if this is geographical differance in terminology.
 

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Discussion Starter · #7 · (Edited)
sp2pilot said:
Variable two; increasing ride height via taller tire Diam. This will also change front geometry but with out the swing arm angle change thus leaving the rear to act in a stock or standard manner. (not a good thing)
Ok I am starting to understand, so how does this sound I am running 190/60 with ride height increase by 4mm in the rear and raised forks by 5mm :confused:

Robert are you saying that if you go with a taller tire must increase swing arm angle too, to do something I have no idea about..................:confused:
 

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To start off with raising the rear by increasing the tire Dia. only decreases rake on the front. Thereby offering a sharper turn in, thus you "feel" the difference as soon as you do this change, however it is a band aid type of correction to alleviate a poor turn in characteristic the RC has. By lowering the front over the triple clamps (raising fork tubes 5mm) you are losing ground clearance with little gain. Let me explain that. By having a lower front end the bike is more likely to ground while trail braking.

Ultimately the target that a tuner is striving to hit is a bike that offers maximum feedback with as much grip as the rider desires.

Swing arm angle is achieved with a modification to the shock and or linkage length.



Ride height is based on how one measures the bike + or - from a given starting point. (In the RC's case the point that the bike is delivered after the correct spring rates are installed and proper sag is adjusted into the chassis)


Starting point for the RC would be:

REAR
Standard length shock no link sag at 25 mm

FRONT
first line showing sag at 37 mm (including top out circuit)

Tires Standard rear 190/50/17 front 120/70/17

from this point the bike will benefit from a much higher angle of attack on the rear swing arm. street; up to 15 mm increase in height measured at the rear axle, Track; up to 18 mm

None of these changes in the stock settings are suggested with out the installation of a quality steering dampner as well as a competent, experienced operator to do the riding chores.

In some cases a track prepared bike may require as much as 20 mm of added rear ride height. However this would be a very extreme setup and it would place a tremendous obligation on the rider to ride around the unstable nature this radical of a set up brings to the table.
 

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Discussion Starter · #9 · (Edited)
WOW :rockon that was a ear full, ok so 18mm increase in the rear is how much at the shock....because the link has a raising rate I am sure is not a one to one I think it might be closer to 4 or 5 mm :confused:

Second you are also saying raising the forks don't do all that much??? So keep it at stock height ???

Third, why am I doing this is because after my track day at Fountana I found that the Fat Girl didn't want to turn at some of the tight stuff. So I am trying to set it up for my next track day at Buttonwillow...............

Thanks a Million.......
 

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I just did my first track day at beaver run.. I ran a 190/60 set up and was a little nervous because I had no dampner(its on order just waiting).. However I found the bike to be extremly stable, I also found that it turned in much quicker than the stock set up... SP2 is right and I am sure I will benefit from shimming the rear and going back to 190/50 or 190/55 but I need to become a little better track rider before I will need things set up that precise... Thanks again SP2 for the baseline track settings for the RC it works like a charm... Take note as well when you do this set up for buttonwillow the bike has more of a tendency to stoppie or lift the rear wheel under hard braking due to the taller rear
 

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hmm...

i have found that if your not sure what you should do.... take it to a good shop and have them set it up for you. i took mine to a local aprilia dealer that I had met at the track before and had them do a good hard street/ mid range track set-up on the suspention while watching and taking down figures as we went. there was an immediate difference in the way the bike handled with stock suspention/stock size tires. $35 bucks.
 

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TUTZO51 said:
i have found that if your not sure what you should do.... take it to a good shop and have them set it up for you. i took mine to a local aprilia dealer that I had met at the track before and had them do a good hard street/ mid range track set-up on the suspention while watching and taking down figures as we went. there was an immediate difference in the way the bike handled with stock suspention/stock size tires. $35 bucks.

That's a really good way to waste $35 & end up on your ass in the process...
 

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Discussion Starter · #15 ·
Knowledge is forever, if I learn it the info is mine 4Life............
 

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LDH said:
That's a really good way to waste $35 & end up on your ass in the process...
well i havent been down on this bike yet and the bike does handle much better than the set-up i was using. it was my :twocents, not a solid gold brick of information. it worked for me, not to say it will work all the time.
 
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