Suspension help

Suspension is not my forte', my limited knowledge of suspension physics was picked up while playing Gran Turismo 3, so not very bike related anyway. hwell:
So I'm looking to tinker with teh suspension setup on my '99. I bought it as is, it came with Eibach rear suspension, and stock fronts. The previous owner had both from and rear adjustments up tight. I found that the bike would lose the road when going over speed humps and potholes. I've given both front and rear a few twists with the screwdriver and and eventually found a mediocre harmony, but currently the handling is slow, and the bike still gets a little upset when hittinh speedhumps and poor road surface, naturally most predominant when in mid corner.

I've read some of the articles here and I gather the first step is to set the sag.
So my first question is:
-When measuring the suspension length, should the bike be on the centre stand or sitting nauturaly under its own weight?

-I assume the sag adjustments are made by the little screw on the rear shock, and the screw on the top of the front struts?

-I understand that you can adjust the rear spring, on visual inspection, there doesnt seem to be any obvious way of doing this on my bike, so how can you do this and what will the affect be?

-What other adjustments can I make to customise the suspension settings?

Thx.

Rob

 

Your bike's a lot more recent and operates on probably more complex mechanics, but my bike, front suspension is done with air pressure via shrader valve and Anti-dive selector, rear suspension is done with air pressure and 1-4 rebound rate adjustment knob.

 

Dang, wish you weren't so far away, I'd have you talk with my friend Dave. I'm no expert but the sag is set in two ways, static sag, bike be it's elf not on the center stand, then again when you are on it. For the most part its simple, but takes a lot of hands, at the least 3 folks. Yes start with the sag. On the front you only have pre-load and it should show only 2 rings for a taught and sportier ride. I'm no help with the rear set up you have, but sag is set with pre-load so more than likely you will need to be able to turn a spring ring to get that set. Sorry not much help, it's also a touchy feelly thing too. If you have the chance, hit a a track day and ask for a suspension tuner, over here they like to help. I'd like to believe it wouldn't be any different were your at.

 

Oh thats the other thing, you mention on the front there should be 2 rings showing...where are these rings? Btw I have heli bars so no doubt that makes a difference.

 

There is a simple worksheet you can use to help when adjusting suspension. So let's start with that.

Front Suspension

F1. Bike on Stand with Suspension Fully Extended

F2. Bike on Ground Without the Rider

F3. Bike on Ground with Rider and Gear

Rear Suspension

R1. Bike on Stand with Suspension Fully Extended

R2. Bike on Ground Without the Rider

R3. Bike on Ground with Rider and Gear



OK Now that you know what F1-3 and R1-3 mean we'll proceed....

A. Place your bike on the centerstand

B. Raise the the bike so that the tires, front and rear, are off the ground and the suspension is fully extended.

C. Measure the distance from a chosen point immediately above the rear axle ( I mark the location on the rear cowl with a piece of tape) to the rear wheel axle nut. Make sure the wheel is off the ground. (This is R1)

D. Do the same thing on the front measuring from the lower triple clamp to the front axle. Make sure the wheel is off the ground. (This is F1)

E. Take the bike off the center stand and allow the bike's weight only to apply load to the springs, front and rear. (This is F2 and R2)
Retake the measurements at the exact locations as you did in step C & D

F. Now take a third measurement with you on the bike with all of your gear, sitting in the position you normally sit when riding. It is best to have a couple folks to steady the bike and to take the measurements when you're on the bike. (This is F3 and R3)

The spring preload should be adjusted, front and rear, so that you achieve the following:

Without Rider - Static Sag

Rear (R1-R2) should be between 10-20mm
Front (F1-F2) should be between 15-30mm

With Rider - (Ride Height)

Rear (R1-R3) should be between 25-40mm
Front (F1-F2) should be between 35-50mm

You adjust the rear spring preload via the collar located at the top of the spring. This will require a spanner wrench to be adjusted. If the preload cannot be adjusted to hit these parameters, you have the wrong spring(s) for your weight.

You adjust the front spring preload via the flathead screw at the top of the fork.

The only other damping adjustments available on the stock VFR components is the rebound adjustment at the shock. The harshness you are feeling during initial compression is due to shitty factory valving that has too much high speed compression damping and cannot be fixed by turning screws. The forks and shock will have to be revalved to eliminate this problem.

For rebound the standard rule of thumb is:

Increase Rebound for:

Unstableness
Looseness
Bouncy action

Decrease Rebound for

Shock action feels hard
Ride is bumpy

This adjustment is done via the screw located at the bottom of the shock on the chain side. Remember clockwise increases the damping and counter clockwise decreases the damping. I hope this help.

 

That makes no difference having Heli Bars........The rings are machined into the side of the preload screw....

 

Cheers Norcal, thats a great summary. I'll try all that out and see what happens.

 

Damn Norcal! Nice job!

Also goggle "Dave Moss"

He is guru at this stuff and his articles and DVD's have helped me get a better understanding on suspentions!

BZ

 

And yet a few more links for continued education;

http://www.feelthetrack.com/tuning_guide.htm

http://www.gostar-racing.com/information/motorcycle_suspension_set-up.htm#SET UP BIKE TO YOUR WEIGHT

NorCal called it; set the sag first and see if the springs will work. No amount of damping adjustment can compensate for the incorrect spring rate. You can make it more livable, but it will never be as good as it could be. Properly tuned suspension is amazing, and it will spoil you for life.

What worked the best for me was googling "motorcycle suspension setup", "setting sag motorcycle", etc. You will also get a lot of hits about bicycle suspension... Anyway, I read everything I could for about a month before I started serious tweaking and investing in aftermarket purchases. Very worthwhile endeavor.

 

NorCalBoy's got you dialed...that's an excellent summary. We should maybe upload that to the suspension forum.

 

Ok, got my bike back from the mechanics time to get this suspension tuned. I checked the front preload screws and I'm unsire if they are correct. Should there be 2 threads showing, and the heli's lined up with the edge of the 3rd? Or should they be lined up on the 2nd?

Also, had a look at the read shock, the preload spring seems to be fully extended (soft). I'm guessing the previous owner knew nothing about suspension and just left it to the default setting *shrugs*

 

Don't worry about the clip ons, stock or otherwise, the bar lines that are used for reference are visible on the pre-load adjustment screw itselft. If you have an owners manual refere to page 136. I find it easier to count screw turns anyway as not all bikes have these lines.

So just do this, screw in the front pre-load adjuster all the way clockwise to it's maximum preload setting on both shocks. If it is still in the factory standard setting then it should be about 6 full turns, but don't really worry about that just turn until it stops. This is the maximum setting.

Now note the position of each flat head screw slot as related to the hands on a clock, mine was about 11 o'clock. Now turn the pre-load adjuster counter-clockwise counting 6 full turns ( I do it 1/2 turn at a time, so 1/2, 1, 1/2, 2, 1/2, 3, etc. ). Once you are at 6 full turns you should see two "rings" around the pre-load adjuster screw as it has traveled out of the shock the second one is bearly visible. This according to the owners manual is the standard stock position.

On the rear preload the standard position is #2. The #7 position is the maximum setting. See page 138.

On the rear dampening the standard position is 1 and 1/4 turns counter-clockwise from maximum, so turn the dampening screw clockwise until it stops. This is the maximum damping setting. Now turn the screw counterclockwise 1 and 1/4 turn. At this setting a little dot on the screw should be aligned with a little dot on the shock just below the "H" for Hard. See page 140.

Now you have the suspension back in standard stock factory settings and you can get into the ball park by adjusting from there. Unfortunatley Honda's Owners manual doesn't help very much, other than telling you what direction to make adjustments from here based on your weight, load, and road conditions. Remember to factor in your weight, passenger, and luggage, oh and don't forget 6 lbs per gallon of gas ;-(=) just kidding about the gas, I adjust my suspension based on my weight alone and don't bother re-adjusting it for luggage or passengers as for a general rule of thumb I'm usually not hitting the twisties or riding very hard fully loaded with a passenger or luggage and want a softer ride (less preload) while in touring mode. I may adjust it a click or two if I have 500 miles of interstate in front of me.

My Buell's owner manual actually has a table that tells you how many turns from the min or max you should make based on your weight and load so you can at least get into a ball park tune on your suspension, but the buell's suspension is completely adjustable ( preload, damping, and compression both front and rear ).

If you have an owners manual read it, if you don't, get one, you'd be suprised how much information is in it. Hope this helps...