Shocks and Springs (longish)

["Tom Brown" <tbrown@xxxxxxxxxxx>]

Gregory:

In my experience, there are approximately three kinds of riders:

The first is what I'll call the basic rider, (full touring and cruiser 
riders sometimes fit into this catagory too) He or she rides a motorcycle on 
the same roads and at the same speeds as a family car, takes the interstate 
if he wants to go somewhere and doesn't ride much over the limit unless he's 
riding in a straight line.   This is the type of rider is always trying to 
get the last mile out of his tires and doesn't really understand what the 
deal is with shocks.   Some of these riders are high mileage guys, some are 
just occasional riders.  Most Harley and Cruiser riders fit into this 
catagory because ground clearance is so limited on this type of bike.

Second is the BMW (And other Euro and some Japanese bike) Touring/Sport 
Touring sort of rider.   This is the guy who takes a lot of back roads, 
enjoys a road with good, tight, curvy "technical" sections.  He may pack a 
weeks worth of gear on his bike, he may camp, he may not.  He appreciates 
great handling on his bike and knows what a bike feels like with a working 
suspension and good tires.

Third is the racer/Track Day junkie.   This guy is looking for lap times, 
brake points, apexes and lean angles.  His bike may be trailered to the 
track and used for that purpose only.   He's not concerned about road-worthy 
comfort because he's not riding very far.  He changes tires often, uses low 
track inflation pressures and makes a science out of setting up his bike.

The seminar recommended on the link in the last digest seems to be oriented 
toward the third type of rider.

I have done track schools and even have a sport bike, but I'm definitely in 
the second group as far as the riding I do the most and like the most. 
I've talked with a lot of guys in the #3 catagory and I don't generally 
agree with them about suspensions and how to set them because I'm looking 
for a different sort of balance between ride and road dynamics than they 
are, so take what I say with a grain of salt.

If you are a #1 rider, chances are that you won't really care much one way 
or the other about your shocks.   If you're happy with your bike the way it 
is, don't spend any more money on it.  Just ride.

If you have a BMW Oilhead suspension with more than 30K miles, you  ought to 
have a look at the rear shock damping setting.  Chances are, you're getting 
almost zero rebound damping.   Look on the bottom of the rear shock on the 
right side of the bike.   There is an adjustment screw there.  Clockwise is 
more damping, CCW is less.   Turn this screw clockwise until it's snug. 
Don't overtighten.   Ride your bike around.   Does it feel better?   Is it 
harsh?

If it feels better, as in more controlled, you've got some rebound damping 
left and it's not so much that it's overpowering the spring.  That's good.

If the ride suddenly gets very bumpy, try increasing the rear spring preload 
one full turn and see if things get a little better.  If you notice 
improvement, keep tightening in increments until something bad happens, then 
back off half a turn.   This is probably as good as it's gonna get for you 
without buying new shocks.

The front end is not adjustable on RTs or Rs.  I think you can adjust the GS 
front end rebound damping, but I'm not sure.

Some symptoms I've had of really bad shocks are harshness on bumps, a 
feeling that the bike is out of control on bumps, especially in turns and 
finally, the bike seems to sort of porpose up and down in the back when you 
hit a dip.   Kind of like an old Buick, if you know what I mean.  Many 
people own old Buicks and are perfectly happy with the 130,000 mile shocks 
on them that were too soft when they were new.   I say, let them drive slow 
and be happy with their motion sickness.   I am not among them.

When I bought my set of Ohlins, I noticed 1. That the ride was more plush. 
The bike floated over small bumps.  It was never harsh even over bigger 
bumps.   I used to count on getting at least one compression "zing" in my 
back on every ride in spite of my efforts to find expansion joints and stand 
up a little on the bike when I ran over them...I'd always miss a bad one and 
get that dull aching pain once or twice.   With the Ohlins, I could sit 
straight up on the bike (an RT) over almost any bump without getting this. 
2. The tires stayed connected to the road better.   If I hit some little 
bumps on a curve, the bike didn't move around.   After I became accustomed 
to this new benefit, I found I was much more confident in the curves.   I 
could keep my eye on the line and just go without worrying so much about 
every little pavement undulation.   3.  The rear of the bike would compress 
once and recover from a big dip in the road.  It never porposed up and 
down...like the above mentioned old Buick.

I've since changed from an 1100RT to and 1150, which has a completely 
different suspension setup.   I found an Ohlins tech that was able to order 
up some parts and convert my shocks/springs to the 1150 spec.   This was 
great as it saved me a lot of money and hassle selling and then buying new 
ones.   Now I have a 1200RT...different setup again.   I was not able to 
upgrade the Ohlins this time, so I sold them.   I now have a set of Wilbers 
for the 1200.  This time, I got the full setup with high and low speed 
compression damping and ride height adjustment.   I'm very happy with the 
Wilbers although it took me a while to get them set the way I like them.

Being a rider who does long distance as well as back road carving on many 
sorts of road surfaces, I found that the Sport Touring settings that came 
with my Wilbers shocks were too strongly damped for me.   I started by 
leaving the front at the stock settings and setting the rear spring so it 
sagged about 2 inches or a little less from full extension with me on the 
bike.  Then, I rode it with the suspension fully soft, then I stiffened the 
rebound just enough to take the porposing out of the ride.  I worked on the 
compression damping last.  I moved both the low and high speed compression 
screws together at first, just increasing two clicks at a time until the 
ride started to feel stiff and backing it off two clicks from there. Then, I 
went back to the rebound damping and tweaked it a little more...one or two 
clicks.   I want the softest ride I can get without chassis control. 
That's what I like best for a BMW.

I rode it that way for quite a while, making spring adjustment and maybe a 
two clicks of rebound adjustment only, for a loaded bike.  One day I got 
tired of the front feeling so much stiffer than the rear, so I backed off 
the rebound damping about 3 clicks and the bike was transformed.  It now 
feels like the front and rear of the bike work together.  It's very comfy 
and it has all the control I need.

I then worked on increasing the low speed compression a bit more than the 
high speed.  This gives the bike less squat on aceleration, but it also 
deteriorates the ride a little bit.  More than 4 clicks difference is 
probably a waste.  In fact, I think both are now within 2 clicks of each 
other.   It's perfect for me.

The trick is to remember the goal of keeping the bike as soft as possible 
with controlled ride motions.   Always start with the spring preload and get 
that set right first.   Next do the rebound, next the compression.  Then 
look at the preload again and possibly back it down a click or two...no 
more.

There's an obvious point on each damping adjustment where the ride starts to 
cross the line into "firm" as you increase damping.  When you hit that, just 
back off a bit.

Another interesting thing is that the spring rate affects how the damping 
works.   A lot of people think tightening down on the spring always makes 
the ride stiffer, but sometimes just the opposite happens.

The most uncomfortable ride is when you have more shock damping than spring 
strength.  If the ride feels harsh and you don't have a damping adjustment, 
try tightening the spring preload a little and see if the ride gets better 
or worse.   If rebound damping is too strong, the supension hits a bump and 
compresses, the compression damping doesn't allow it to recover.  You hit 
another series of bumps and the suspension compresses a little more each 
time and each time doesn't fully recover.   Pretty soon the suspension is 
riding on the bottom of the stroke and you get VERY uncomfortable.  Tighten 
the spring in this situation and the recovery is faster and the bike will 
ride in the center of the suspension's travel where it's supposed to be.

>My bike is a 2002 R1150R with 31K on it.

>I've heard and read in different places that the factor shocks and
>springs wear out around 30K. What would be the signs that your shocks
>and springs are starting to go bad and need to be replaced?

My '99 RT's shocks were shagged at about that mileage.   I think I suffered 
for another 10K miles or so.  The bike wasn't horrible, really.  I'd never 
ridden a bike with really great shocks on it, so I didn't know what I was 
missing.  When I put on the Ohlins, well, it's a whole different 
thing...better than new.

If your bike isn't turning in correctly, it's more likely that you've put 
too many straight-line miles on the tires, both front and rear, but 
especially the rear, and they have changed shape.   The rear, because it has 
to deal with engine torque against the street as the bike moves down the 
road, is the most vulnerable.  The tire gets flat in the middle with near 
square corners on the sides instead of a smooth radius to the sidewalls. 
The front does the braking, so front tires can get the same problem, but 
fronts usually last longer unless you do a lot of stop and go.  When you 
ride straight with squared off tires, you can let go of the handlebars and 
the bike stays straight...kind of fun, really.   Lean the bike, however, and 
it resists until you get over this sharp corner on the edge of the tires, 
then the bike seems to fall into the turn.   When you turn with these tires, 
you're either riding "uphill" onto the square corner, on the square corner, 
which can be a very small contact patch or "downhill" off the square corner, 
where the bike feels like it's falling into the turn.  Handling is weird in 
any of these scenarios and fighting it becomes a nuisance.

Your bike can still be turned and the tires are still safe for most things, 
but handling is a lot less intuitive and more of a chore.  I've found that 
Metzler's have stiffer sidewalls than Bridgestones and they are more 
disagreeable when they get this squared condition.  Although Metz Z6s are 
about the stickiest and best tires around for riding hard in the twisties, 
when they get squared off on the interstates, they really don't work the 
same at all.   Getting new shocks will not fix this.   Just get some new 
tires.

If you're not ready for new tires, lowering air pressure down to what BMW 
recommends helps the situation sometimes.

For what it's worth,

- -TB

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