Preload = Ride Height?

I can only go on what information I had for my 748R. In the RS workshop manual it gave a recommended ride height for long sweeping tracks and a second ride height for tight twisty tracks. It required adjusting the length of of the fork leg through the triple clamp measured from the underside of the lower triple clamp to the bottom of the upside down fork leg and adjusting the ride height rod on the rear shock. It also gave a setting if you used the steeper head angle. On my old ST4S, a Ducati WSBK technician told me to adjust the rear ride height so the back wheel was just off the ground when the bike was on the centre stand. Transformed the turn in for the better. Andy

 

Be like a chopper.

Dan Kyle recommends lifting not lowering the bike, front and rear, as increased COG makes turning easier (may affect straight-line stability). Others, lifter rear and dropping front.

If you drop the rear. Drop the front to the same level to keep balance imo

 

Be careful of radiator clearance and anything on the rear that may foul becuse the stroke is going to be closer to the ground (if that makes sense)

 

IMO. If it ain't broke, don't fuck with it. IMO.

 

What you need is a day at a favourite road (as you don’t do trackdays) and pay someone like Paul goodhall to make the changes for you.

 

When were your forks and shock serviced last?

 

Ok, we need to break this down a little..

ride height
In its truest sense of the term in racing is the attitude of the bike or the racecar - look at it as how high all the critical points are from the floor - CoG, riding position etc.

What Griff was probably talking about in the context of ride height and suspension tuning was the unloaded compression of the suspension just under its own weight without a rider.

Basically - how the bike sits.

We motorcyclists are lucky. We know the difference between spring preload and ride height - you'll find modified car people are clueless and just don't get the concept.

Sag
Is how much the suspension compresses (sags) when loaded with the static bike and bike+rider weights. if you took both wheels off the ground and measured, then you would have full extension sometimes known as free sag.

Free Sag - both wheels off the floor and the suspension fully extended - very important as it gives you your baseline. These figures should be found in your bikes' data as fork travel and rear shock travel.

Static sag is the above - no rider, wet bike - (although this isn't common to set up this way now days unless you're in a parc ferme' situation where your vehicle is measured to ensure race legality)

Rider sag is with the rider on, fully kitted and in the common riding position.

This is important because if he's a guy who likes loading the front end by sitting forward int he seat and leaning across the tank, then you need to compensate for the extra weight bias.

Your ball park parameter is that you ideally want to look for about 20-30% of the suspension travel to be taken up when all loaded up - so a 120mm travel fork for instance will be 30-40mm of rider sag depending on riding style and use - road, track etc. 25% is probably where the factory currently set their baseline.

So yes, you get your Sag set up and in doing so 'ride height' within the parameters of your suspension. Spring preload is not a parachute to compensate for the wrong spring. the more you preload the spring the more compliance you're removing, as the spring is designed to work within a certain window of forces acting on it.

Now you mention heights...

In dropping bars through yokes you're steeping the steering and shifting the centre of gravity.
Your benefit is steering quickness - Your trade off is stability as the rake/trail figures will change accordingly. Look at these two as quickness and stability and the zen harmony that is the holy trinity of quickness/stability and rider confidence is why people make a living out of this stuff.

Ducati's have traditionally had quite slow, heavy steering - but freight train stability. Go, the the other way and you have a bike which seems to twitch and have a mind of its own even in a straight line.

Play with it for sure, but please do it in 1 or 2mm increments, as even 1 or 2mm will have big impacts. You might not notice it going round the block, but at speed it's a different matter.
Look at a rough 4mm of fork drop equates to 1mm of trail.

Dropping forks in big increments has other ramifications such as clearance issues if you bottom out on the suspension - a good way to check if you have clearance is to make a template of the wheel radius and lift it the fork travel distance along the direction of the fork tube. Admittedly, you're talking about bottoming out - so the choice is yours.

Dropping forks : lower front end , decreased rake and thus trail for more aggressive geometry.
Lifting forks : higher front, increased rake / trail, more relaxed geometry.

Raising the back end however is not the same as dropping the forks.
If clearance is your enemy with dropping the front, be aware that the linkage is your enemy at the back if its rising rate. ( you won't have the travel in the shock to allow you to get to that stage)

As has been mentioned, you could actually go the other way, counter intuitive I know, and lift the forks through the yokes, bringing the CoG higher and allowing the bike to be more flickable if the centre of gravity is higher - there's a reason why commuter / trailies etc are like this, and also the ZX10R uses this very principle - its forks are 740mm long with a 130mm travel.

You mention mid corner stability - it's a function of two things - suspension geometry and you. Lowering the CoG won't necessarily make it more stable mid corner - but it will affect how it tips in and behaves once mid corner.

Ride a 500gp bike that Kevin Schwantz said was 'stable' and you might find that for you its the most nervous thing on the planet.

 

so the free sag is literally the bike hanging off the ground. with no weight on the wheels.
That's the same for everyone, but it's the RIDER SAG which will be different for all, as that's the one with the rider parked on top of it.

The free sag measurement is kind of academic as you really are interested in you on the bike.

As I said above it really isn't used that much anymore to do setups, but it's still very useful to keep as a figure in the background. If you're on your own doing this then the method below should get you somewhere close. If you've got two people, then its better as they can support the bike when you're on it.

lift the wheels off the ground - pair or individually doesn't really matter.

Rear:
Find a point you're happy with from the axle directly up to the bodywork or subframe. This will be the point where you take your measurement from.

Measure the distance, then drop the bike onto the ground and measure again. This will give you two measurements.
Free sag - uncompressed, and static sag - bike weight only.

The Ducati rear suspension measurement tool is great as it gives you a fixed point.

Front:
same as above but at the front you have the luxury of putting a cable tie on the fork leg in order to give you your numbers.

I measure from the bottom of the stanchion to the top of the fork lower, for the initial measurements, or if you're using a cable tie then to the cable tie.


Now gently compress the forks and rear end to settle the suspension, and reset your cable tie against the dust seal.

With you on the bike, at your heaviest condition (leathers etc) simulated or otherwise, sit on the bike and assume your comfortable position as you would when riding.

Measure the same points as before front and back.

This gives you your rider sag.

You're looking at the difference between the static and rider sag, if you add the free sag to this, you'll probably be coming up with a figure of around 25 - 45mm and if you know your free sag and suspension travel you can see how much of the range it's using.

You can then use preload to adjust from there. if you've got to the point where you're meeting a rider sag of say 30mm at the front by winding the preload all the way in a the front and used all your rings up a the back, then you need a higher weight spring.

As a starting point if you're not sure, take everything back to factory baseline, or in the case of your TTX, the ohlins base setup guideline settings - then you can see how the changes are affecting things.

Patience is key here, there's no silver bullet of suspension setup. Once you've got a base setup you're confident with, then you can start tuning it accordingly for the way you yourself ride.

 

this is a video I've used many times and found quite helpful

 

It should be the same for everyone. Only variable being use: road or track. IMO.

 

Only time I would have static different would be track, when I’d want it to sit higher as standard. Eg I used to run my 848 at 20mm road but would run 10-15mm track.

Worth noting how many run less than 10mm then complain and puss about with stuff because the rear is skipping. Not realising they are always going to skip because it’s topping out!!