Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 1198 / 1098 / 848 > forks bottoming out - help

[khushy]

Originally Posted by bradders

have been out today and the cable tie I fitted is right at the bottom. I know its not sliding down, you can see where the slider is going to, I am just using all the travel!!

so how do I sort this? bike seems to ride well, and is super planted even on the bumpiest roads, but need to get some travel back, so is it up the preload, or stiffen compression, or both?

there is too much sag, so I will be upping the PL anyway, just want to know if I need to do more

thanks

ohlins - 8.5nm and 9.5nm springs for sale - send me a pm or make me an offer - they need to goooooooooo!

khushy

[skidlids]

The main thing about spring rate is that it is a measure of how much the spring is compressed by a given weight. which is why the amount of suspension travel is oh so important.

Then you have to look at what is going to use up your suspension travel and spring accordingly.
For road riding I would pick a shock with 65mm of travel over one with 60mm of travel any day, same goes for the front forks and a good match/balance between the two is also a factor as both wheels will encounter the same size of bumps at the same speed although the rear wheel normally has more mass so needs the shock to be sprung a bit stiffer so nowing your linkage ratio helps, although playing with the Nitrogen pressure in the shock can have a similar effect to playing with your front fork air gap.

the more travel you have the lighter spring you can use and the less force the rebound damping has to deal with

But as Paul is talking about his standard 848 forks and wanting to get more of the travel back I would try increasing the preload and worry more about remaining suspension travel followed by loaded sag and not worry about unloaded sag.

I have ridden a lot of miles with Paul, seen him ride my DD bike and know how hard he rides and if he keeps bottoming those forks it wont be long before he makes a dent in the scenery somewhere

[Dementor]

Originally Posted by skidlids

I have ridden a lot of miles with Paul, seen him ride my DD bike and know how hard he rides and if he keeps bottoming those forks it wont be long before he makes a dent in the scenery somewhere

Let's get it sorted then, we don't want that

[skidlids]

Do not confuse Fork travel with the overall travel of a progressive spring

A progressive spring could go from 0.6kg/mm to 1.2kg/mm over a distance of 180mm

So has an average spring rate of 0.9kg/mm

Lets assume the rate of change of the spring is linear (gets more complicated if its non linear)
Now if your fork only has 120mm of travel, without any pre-load the travel will use the 0.6kg/mm up to the 1.0kg/mm part of the spring, giving you an average of 0.8kg/mm, so softer than the spring average.
Now if you pre-load the spring by 30mm you end up using the 0.7kg/mm to 1.1kg/mm part of the spring giving you an average of 0.9kg/mm the same as the spring average.
Now if you pre-load the same spring by 60mm you use the part of the spring that is in the 0.8kg/mm to 1.2kg/mm giving an average spring rate of 1.0kg/mm resulting in stiffer than the total spring average.

[bradders]

up the preload then

job for Tuesday

[skidlids]

Originally Posted by bradders

up the preload then

job for Tuesday

Just like people did when they had bikes with twin rear shocks and wanted to carry a passenger, they just wound the stepped preload collar round a notch or two to stop the backend bottoming over the bumps

[bradders]

anyone know the std rate? just found the calculator on racetech and it says I should have 1.067kg springs, but only lists 1.0kg as max, so want to know the difference between that and standard as it says standard is 0.960 anyway!!