Ride height tool - MVAgusta.net
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post #1 of 28 (permalink) Old 01-07-2010, 11:27 AM Thread Starter
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Ride height tool

Been swatting up on the workshop manual, i am puzzled with this workshop tool for setting ride height/static sag, it's exactly the same method for setting the sag on any bike. All you need to do is get the rear wheel of the ground, on my Aprilia i just pull it over on the sidestand to get the rear fully extended, then stick a bit of masking tape on the tail unit and mark it with a pen, then measure from a given point on the swingarm or spindle etc to the pen mark whilst the rear is unloaded, write it down as say M.
Write that figure down, then sit the bike upright on a level floor and push the rear end up so it is at it's max extension then let it go.
Take a measurement using same pen mark and point on the bike, write it down as say M1, then compress the rear end and let it go and do the same again to give another measurement M2, you will probaly fine a difference between them (this is stiction) add both figures together and then divide by two, then deduct this from your very first measurement M to give the static sag.

What i am saying here is why do we need this tool to do this simple job, or am i missing something

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post #2 of 28 (permalink) Old 01-07-2010, 12:18 PM
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The ride height tool is to set the distance between the rear axle and the mark on the tool. The figure is 222mm. You can set it anywhere you want to vary the rake/trail but I prefer to follow the book. At least in the beginning and then tweak from there.
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post #3 of 28 (permalink) Old 01-07-2010, 02:44 PM
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If you need a ride height tool, give Chris at X Bikes a call, if he has no stock I have a spare I can sell you.

Brian
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post #4 of 28 (permalink) Old 01-07-2010, 03:42 PM Thread Starter
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Thanks Brian.

I fail to see the need for the tool, if you take a measurement from the centre of the spindle to a mark on the tailpiece and then perform the operation as per the manual to give you 22mm, does the same thing.

Also the 22mm is the difference of stiction between topped out and released and compressed and released, your sag setting should be the mean figure which is 11mm.

Why adjust the ride height adjuster to set your sag? is this normally not done by adjusting the spring preload, it states in the manual that if you can't achieve the 22mm then adjust the spring preload to obtain the correct figure.

I would normally set both front and rear static sag and ride the bike, stop and take notes and adjust damping then adjust ride height to alter the weight over the front or rear to what i want it to do.

I may be missing something here but from what i see in the manual where it shows using the ride height tool, all you are doing is setting static sag as per this article from Sport Rider

Rear end

Step 1: Extend the suspension completely by getting the wheel off the ground. It helps to have a few friends around. On bikes with sidestands the bike can usually be carefully rocked up on the stand to unload the suspension. Most race stands will not work because the suspension will still be loaded by resting on the swingarm rather than the wheel. Measure the distance from the axle vertically to some point on the chassis (metric figures are easiest and more precise; Figure 1). Mark this reference point because you'll need to refer to it again. This measurement is L1. If the measurement is not exactly vertical the sag numbers will be inaccurate (too low).

Step 2: Take the bike off the stand and put the rider on board in riding position. Have a third person balance the bike from the front. If accuracy is important to you, you must take friction of the linkage into account. This is where our procedure is different: We take two additional measurements. First, push down on the rear end about 25mm (1") and let it extend very slowly. Where it stops, measure the distance between the axle and the mark on the chassis again. If there were no drag in the linkage the bike would come up a little further. It's important that you do not bounce! This measurement is L2. Step 3: Have your assistant lift up on the rear of the bike about 25mm and let it down very slowly. Where it stops, measure it. If there were no drag it would drop a little further. Remember, don't bounce! This measurement is L3.

Step 4: The spring sag is in the middle of these two measurements. In fact, if there were no drag in the linkage, L2 and L3 would be the same. To get the actual sag figure you find the midpoint by averaging the two numbers and subtracting them from the fully extended measurement L1: static spring sag = L1 - [(L2 + L3) / 2]. Step 5: Adjust the preload with whatever method applies to your bike. Spring collars are common, and some benefit from the use of special tools. In a pinch you can use a blunt chisel to unlock the collars and turn the main adjusting collar. If you have too much sag you need more preload; if you have too little sag you need less preload. For roadrace bikes, rear sag is typically 25 to 30mm. Street riders usually use 30 to 35mm. Bikes set up for the track are a compromise when ridden on the street. The firmer settings commonly used on the track are generally not recommended (or desirable) for road work.

You might notice the Sag Master measuring tool (available from Race Tech) in the pictures. It's a special tool made to assist you in measuring sag by allowing you to read sag directly without subtracting. It can also be used as a standard tape measure. Measuring front-end sag is very similar to the rear. However, it's much more critical to take seal drag into account on the front end because it is more pronounced.


In the manual it shows for the Tamburini 25mm and all you do is adjust the spring preload to obtain the 25mm difference (again to me this would give a mean sag figure of 12.5mm).

I run my 2006 Aprilia Factory at 28mm static front and 13mm rear, my Aprilia Factory track bike with less sag due to the nature of what you are asking of it, tracks are not as bumpy and full of potholes etc. for the suspension to cope with.

If you measure the MV to 22mm like the manual says, then to me that would in normal sag setting routines give a rear sag of 11mm.

Agree or disagree......................

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post #5 of 28 (permalink) Old 01-07-2010, 04:31 PM
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Disagree. Ride height has absolutely nothing to do with sag. What it does do, among other things, is alter the trail of the front wheel- Higher rear ride height=less trail=quicker turning and less stability at speed. Lower rear ride height gives the opposites. I believe the 222mm figure is given as a compromise between the two and can be varied to suit the individual rider's taste which requires alot of tweaking and riding to find the sweet spot.

I also happen to disagree with the 22mm and 25mm static sag figures given in the book. I feel they're too much.

Eraldo Ferracci recommends a distance of 243mm from the tool to C/L of the axle on the Tambo for static sag which equates to 6mm of static not 25mm as it says in the book. Personally I have set my Tambo static at 11mm and rider at 32mm for the street. Including allowing for stiction.
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post #6 of 28 (permalink) Old 01-07-2010, 04:56 PM Thread Starter
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That's what i am saying Lee, why alter the ride height adjuster to set your sag, i know ride height is not sag, there are a lot of ways to skin a cat, more sag on the front will give quicker steering as well as lowering the ride height, and vice versa, same on the rear, more sag will slow steering, less sag will quicken it. Too much weight on the front will cause rear traction problems as well as instability, i have a reasonable understanding of suspension, but by no means a guru, i can set my own bike up by feel and not settings from manuals etc., suspension is a very personal thing too, what i like does not mean another rider my weight will like it, so setting up for your riding style is the important thing, not to a manual.

Those figures of 22mm and 25mm would IMO equate to sags of 11mm and 12.5mm if you use the normal equation for setting sag, your bike sounds pretty close at 11 and 32, 6mm is more like a track setting for sag on the rear.

I just fail to see the need to buy a tool to do this simple task.

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post #7 of 28 (permalink) Old 01-07-2010, 10:29 PM
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I am waiting on Noel to get a replica of the factory tool available so I can get one...Noel? have you got some made yet?

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post #8 of 28 (permalink) Old 01-07-2010, 11:29 PM
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Ed;
got to drill and tap them..... first ones will be done tomorrow....don't worry i didn't lose my list, i'll PM you

Badger;
you are forgetting the eccentric chain adjustment.....look in the manual
if you adjust the chain and reset the sag.....the bike will handle the same except for the small wheelbase change
they use the shock strut to adjust the height and the hydraulic preload adjuster to correct the load on the shock because of the longer swingarm

Noel-theknurl

Last edited by theknurl; 01-07-2010 at 11:32 PM.
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post #9 of 28 (permalink) Old 01-08-2010, 02:18 AM
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The tool gives you a fixed refference point to set the ride height.
As has been pointed out, when you adjust the chain, because the adjuster is eccentric, it messes up the ride height.
This adjustment should be made every time you tension the chain.
I have ridden bikes that the ride height very wrong & it does make a noticeable difference.

Sag is a different thing altogether.
When you adjust the ride height, the sag is not effected. Once it is set to suit you, just forget about it.

Brian

Last edited by moto-tech; 01-08-2010 at 02:21 AM. Reason: Spelling
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post #10 of 28 (permalink) Old 01-08-2010, 03:04 AM
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Quote:
Originally Posted by esq'z me View Post
I am waiting on Noel to get a replica of the factory tool available so I can get one...Noel? have you got some made yet?

You do know that i've made my own and they are available?

check out my thread on the performance section, last few posts show the tool
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