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Old 09-Jun-2005, 07:23 PM
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DSC Member Shazaam! Shazaam! is offline
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Suspension Ramblings

If thereís one aspect of motorcycling thatís a mystery to most, itís suspension. Just like with anything else in our lives we have three ways to deal with it: We can ignore it, we can pay someone to help, or we can learn a little about it.


Ignore It

Modern motorcycles are delivered with a thoroughly-developed handling package that will meet the street performance needs of the majority of us. If not, there are a range of suspension adjustments that will allow us to fine tune it to our needs, but most of us are happy with the stock settings and never touch them.


Pay Someone

Like any consumer product, a motorcycle will incorporate different components for different models in order to meet a target price point. The after-market equipment industry then addresses the service, special performance, customization and consumables market.

Suspension specialists provide an integrated suspension parts and adjustment service to meet the suspension performance need of a rider with a particular riding style, or the demands of a particular track. Further, after-market parts are sometimes more durable and are often designed to provide a different, or extended range of adjustment. However, even the best specialists are a for-profit business, so when owners go to them to make their bike ďhandle betterĒ they should at least have an idea of what to expect for their money. Most donít.


The Basics

Information about suspension can be broken down into basics, experience with certain combinations of equipment and settings, and opinion. You need to be able to separate-out which-is-which. In particular, be skeptical when the argument is presented that you should use a particular set-up that was used on a winning race bike, because youíre not that rider on that track, and using that set-up wonít make you so. For this reason, using suspension settings preferred by magazine test riders on a test track are often not best for a reasonably-skilled rider on the street, either from a handling or comfort point-of-view.

Also, buying equipment used by race teams ignores issues like equipment sponsorship money. It also buys-into the marketing concept that, if itís more expensive - itís better. Keep in mind that thereís a lot of product loyalty and opinion generated by someone who has just spent several thousand dollars on a set of high-end forks or dampers.

Damper re-valve kits for stock dampers or full damper replacements are commonly touted as the way to improve on stock components to get better handling. Such equipment can accomplish three things:

It increases the total range (maximum to minimum) of damping that can be selected

It moves the center of the range-of-values that can be selected to give a more usable range

It increases the number of damping values within a range to allow smaller steps (finer adjustments) between settings.

These can be modified separately for rebound damping and compression damping so an suspension specialistís experience and advice here will often be useful.

When you ride on the street you encounter a wide range of road surfaces, so a fairly-wide factory range of settings is provided in the stock set-up to allow you to accommodate the conditions on your favorite route.

On the track itís different. Suspension settings refinement will tend to put you into a narrow range of useful damping values so re-valving for this range is often beneficial.

Of course, before you even touch damper settings you need to make sure that the stock front and rear spring rates are correct for your body-weight. You donít need a suspension specialist for this, your dealer can provide replacement springs and properly adjust sag if required.


So tell me your thoughts on this.
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Old 09-Jun-2005, 07:32 PM
Felix Felix is offline
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One thing to remember is that most handling problems for road bikes are not due to incorrect compression and rebound damping, yet those are the "screws" that fiddled with the most, probably because it's easy. Getting the basics right, i.e. static sag, spring rates, etc. is definitely the first step. Don't touch anything until you are certain they are correct.
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Old 09-Jun-2005, 07:34 PM
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DSC Member Gaz 748 Gaz 748 is offline
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I have been fiddling with the suspension on my bikes for years and thought I was quite good, had it set - up by a ohlins dealer last week, it`SO much better if in doubt, let the experts sort it out.
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Old 09-Jun-2005, 07:58 PM
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Interesting thoughts Shazaam...................

Over the last couple of years, i've tried to understand the basics. I'm pretty comfortable with this now. After setting up the sag for a customer, and adjusting the damping somewhere close, I suggest it's time to take it to the experts.

The biggest thing i notice is that often, "a little knowledge gets pretty dangerous"......................
The main problem i find is with peoples understanding of preload. I see quite a few bikes with the preload turned right up in the belief that it makes the suspension firmer, or it's backed right off to make it softer. No attention is paid to the damping settings. Just whack the preload up or turn it all the way out.
The other is the adjustment of the compression damping. More often than not, it's set so low that with the aid of a zip tie, it's clearly visible the suspension is bottoming out.

I have a simple setup routine that i was told by one of the experts I use for the difficult bits like revalves etc.
Set the preload up so, under the bikes own weight, you get about 10-15mm sag front and rear.
With the rider on the bike, it wants to be 30mm-50mm at the rear and about 40mm at the front.
Adjust the front compression damping so that after a quick ride with some heavy braking, the zip tie is about 10mm-15mm from the bottom of the fork leg.
Adjust the rear so it "feels" the same as the front whilst bouncing the front and rear of the bike.
The rebound damping needs to be set so the suspension recovers fairly quickly, but without bouncing back. Just nicely damped. Again, get the front and rear feeling the same.
That's as far as i go. It's a starting point, but after that, i leave it to the experts.
If it's a struggle to get both sag measurements, within the parameters mentioned, then the spring rates are probably wrong for the rider's weight.
ie, if you get the 10mm under the bikes weight alone, but get 60mm sag on the rear, then the spring is too soft for the rider. you can try and tweak it out, but keep an eye on the two measurements.
The other thing i've learnt, is that if you are going to play with the suspension, note down all the stock settings, check that's what they are set to and then adjust one thing at a time. If it get worse, put it back and try something else. Stock suspension is also pretty coarse in it's adjustment. One click won't make any noticable difference. try three and feel what happens. It'll help you understand what happens and will help you to make a more educated guess at what to do next.................

i was also told that 80% of percieved problems with the front end are actually caused by the rear........ some off the CSS teachings go along with this I think????

It can get as complicated as you want to make it I guess. But the golden rule is, if you don't think you understand what's going off, or what you do doesn't seem o be working, leave it alone and take the "expert" route and pay someone to sort it for you. It'll hurt if yo get it wrong.
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Old 09-Jun-2005, 10:35 PM
Gizmo Gizmo is offline
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Get geometry, spring, preload and sag sorted and the adjustors aren't so critcal. As has already been said a little knowldege can be dangerous so learn the basics of geometry and springs first, to do so might involve a trip to a suspension tuner but try and take note, if you are not sure ask and dont be scared to ask again until you do understand. Road setups are tricky and occasionally it might mean you have a setting which technically isn't correct but the rider feels comfortable with it and unless they are prepared to adapt their riding style might be best for them, and then gradually move towards a better setup.

I like playing with suspension but I'm fortunate in that my job involves a lot of work with mountain bike forks and rear shocks so have had 7 years of pretty technical experience to use.

I'm moving away from the section8 settings now, tried them and i'm going to more rear sag (35 - 37mm) to improve feel at rear but running about 288 on the ride height, moving forks back to 3 lines showing as well. front felt floppy under power as though head angle was too shallow which is weird in the current setup and the opposite of how it should be. Also now got 3 springs to mess with, 64, 70 and 75 so can run varying preload /sag to see which i prefer, 64 with more preload is my favourite at the mo but my riding is all road, involves different surfaces and conditions and i'm not pushing hard. A track setting for me would be vastly different.

DCR your bike was as it left the factory, no preload 50mm of rear sag and no alteration to geometry. All i did was correct those things and put it into a mid point on everything then added a little bit of adjustment to balance front and rear. you can tweak it over time to a more personal feel. Once you get your new tyres it'll need adjusting, the grip and profile will make a difference to the feel now even more so because rear was getting square edges after the m way hacking.

Does anyone have a dwg file of the chassis/fork on the 999 or 749?? i'd like to stick it in computer and work out angle changes before i alter things.
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Old 09-Jun-2005, 11:15 PM
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YMFB YMFB is offline
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I just left a message on the ST section and have now come across this, which sounds like someone here maybe able to advise. I ride an ST4, after a while with a pillion it seemed to me that more pre-load was needed so I turned the big nut a couple of clicks, then we went off to IOM TT where the roads are fairly crap but even at very low speeds we bottomed out. Rushjob on the last page has suggested changing the rear suspension to an Ohlins as fitted on the ST4S, do you have any experience of this, should I be able (or maybe an expert be able) to adjust the stock suspension so that I can tour two up with luggage at one setting then re-adjust for normal riding.
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Old 09-Jun-2005, 11:31 PM
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Im well confused with all this suspension tech talk, my head is pounding!

Time to take it to someone who knows
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Old 09-Jun-2005, 11:44 PM
Gizmo Gizmo is offline
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Quote:
Originally posted by khu996
Im well confused with all this suspension tech talk, my head is pounding!

Time to take it to someone who knows

mine does every year when the fork and shock maker introduce new technology but i have to learn it. I do our new product presentation so have to be able to present how the shocks improve the package. Hardest bit is to make it simple so our dealers can understand. Once you get a shock without a spring on its actually quite easy to see what compresion and rebound damping do, a bit harder to work out what overall effect it has on handling though.

The ohlins site is a good one to start from if you want to start learning ,their set up guides are easy to follow and explain things well. Or just go to a good suspension company like K tech and let them do it for you.
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