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| MarJay |
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MarJay
But it's British!
Joined: 15 Sep 2003
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 Posted: 18:20 - 19 Jan 2004  Post subject: Suspenders! Mmmm! |
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No, I'm not writing a post meant for the porn usergroup. 
Hopefully This will be deemed good enough to get into the faqs section 
About a year ago I applied for a job at BiKE magazine as a staff writer (before I got my current job). I was asked to submit a few short articles (around 200 words) on different subjects. Needless to say I didn't get the job, but I did get a letter saying that the editor was impressed with my submissions. (maybe they all get that ) I figured now that the BCF mark II has been initiated I might bring one of my old short articles out of mothballs. The particular one I am going to post is a short explanation of the technical terms and function of your bikes suspension. The next paragraph is my original submission and please bear in mind that it was supposed to be a 200 word explanation of the complex subject of suspension. I have decided to follow it up with a more in depth look at the boingy bits on your bike.
| Mark's Job Application wrote: | Motorcycle Suspension
The primary job of motorcycle suspension is purely and simply to ensure the tyres maintain contact with the road surface. Ride quality is often a factor but this depends on what type of bike the suspension is to be fitted – it is more important for example to give a smooth ride on a tourer than a race replica. The springs are the key to how the motorcycle behaves. Too soft and the bike will bottom out. Too hard and the tyres will leave the road over bumps. The damping only exists to prevent the spring from moving too quickly. Fully adjustable motorcycle suspension has three types of adjustment, spring preload, compression damping and rebound damping. Preload does not make the spring stiffer, but rather sets the static sag of the suspension so that the dampers work in their optimal range. The compression damping slows the spring when the wheel moves upward after hitting a bump, and the rebound slows the wheel when it returns from the upward movement. The wide range of adjustment in sports bike suspension is important because of the wide range of shapes and sizes of people that might ride the machine; the standard set-ups are designed for Mr. average. The style of riding is also important. |
OK so that was probably the article that confirmed my career path as an engineer and not a writer!
Despite the obvious deficiencies in my writing career I shall endeavor to add some detail to my 200 words. I have spent most of my time as a biker looking for the ultimate handling solution. Suspension it seemed at first was the holy grail. If I bought wsb spec ohlins, I figured, then I would be a riding god! I have learned in a short period that this isn't the case and ninety nine times out of a hundred its my riding that makes the bike work better or worse, not the funny springy things at both ends of my bike. However, how you ride also depends on how the bike "feels". If you can improve the "feel" of the bike then your riding may just improve. Lots of bikes have fantastic super gizmos and doodads that change the operation of your suspension. These might help your riding or they might not. It all depends on your attitude. If you want to adjust your riding as well as your bike then you might just get faster.
Personally I always aim to improve my riding before my setup, but I might well be a hopeless case! You might have to resign yourself to not being Valentino Rossi too!
Even so, if you want to play with those tempting looking screws and adjusters on your bike then I'm not going to stop you .
Here's my input from my knowledge of suspension into the world of BCF.
What is suspension for?
Well, you might think you know, but I would take a guess that the ultimate point of suspension might elude you (although by now you've probably read the above paragraph - so you know ) Apologies to those who had the answer already. Basically Suspension isn't there to make the rider comfortable, or to stop components of the bike from flying off when you hit a pothole. It is purely to keep the sticky bits of rubber that are stuck to your wheels on the road. Just imagine if you will a bike without suspension. If you ride over a small bump then the wheel leaves the ground for a split second. If you try to steer or brake during this split second then the best case is that nothing will happen. The worst case of course is that you'll crash .
Suspension also, as a by product of holding the tyres on the road, has a marked effect on how your bike behaves when cornering. A GoldWing for example will not be able to corner as well as an NSR Because the Goldwing will be set up for comfort and an NSR for sporty riding.
Might I need to adjust my suspension?
The answer to this one is maybe. The main factor in adjusting your suspension is your style of riding and wether or not its suited to the bike you ride. If you like to ride fast and have an R6 on stock settings, the chances are this might be a good setup for you for the road. You might tweak it a bit - but you could make things worse. If you are larger than average size, or have a bike that is renown for being a bit squishy then you might want to stiffen things up a little. Conversely a lot of riders over stiffen the suspension and the bike feels harsh and uncooperative. Personally I would say that unless you do loads of trackdays or are a very fast road rider, you shouldn't need to.
What is Damping?
If suspension only had springs then riding your bike would be like riding one of those springy seesaw things you see in parks! Damping keeps the springs in check so they don't resonate. The dampers consist of a piston in oil. The oil provides resistance that prevents the spring from moving as fast as it wants to.
What is Compression Damping?
Compression is the wheel moving upwards after hitting a bump. The suspension also compresses when you brake or shift the weight forward. Compression damping slows this movement. Ideally you want separate high and low speed damping so that you can isolate the braking and weight shifting movement from the bump hitting movement.
What is Rebound Damping?
Rebound is when the suspension re extends after it hits a bump or when weight is shifted rearward when accelerating. Rebound damping puts a check on this movement.
What is Preload?
Preload is the amount the spring is compressed in order that the suspension works within its optimal range. Remember that if you hit a bump the suspension needs to move upwards to keep the wheel from skipping off of the road, but also you need the suspension to be able to move downwards if you ride over a pothole. The amount of downward movement the suspension has available is known as sag.
Preload is adjustable so that you can set the static sag which changes depending on how heavy the load on top of the bike is. The load on top of the bike is generally the rider
This tells us that we need to set the static sag on the bike up so that the sag with a rider is within the specified range. This usually needs to be about 30mm of sag with a rider.
A good rule of thumb is if you are quite a bit over average weight the static sag needs to be about 10mm, so you compress the springs by 20mm. If you are a short skinny type ( like me) you need to set 20mm static sag so you compress the bike by 10mm. If you are of average weight (bear in mind that Japanese bikes have japanese test riders, IE about 10st average) then you need to set the static sag about 15mm. If you are an inbetweeny then set the sag appropriately.
How do I set the damping up?
If you have a bike with multi adjustable suspension you might want to have a play at setting it up. I'll try to give a rough guide to getting your suspension working in the right way. This isn't an easy fix and won't make you break the lap record at Donningtion, but it might help customise your bike to you and your riding.
Once you have set the static sag for your weight (or for you and pillion) then you need to set up the damping. If your bike handles oddly and you've got to the point where you want to adjust the suspension then I recommend that beforehand you check the following:
A) That your tyres are in good nick and set to the correct pressures
B)That your wheels are in line
C) that your suspension is in good order (no leaks etc) and that it is set to factory settings.
OK You still want to fiddle? Then start with the rebound damping.
Well the rebound damping is fairly easy to set up. Sit on the bike with the front brake on and push down on the bars sharply. Let the bike bounce back. The forks should bounce back once and the return to their normal position. Any extra bounce has to be dialled out. The compression damping on adjustable bikes is usually a screw at the top of the fork leg.  Remember to make sure both legs have identical settings if you don't do this you and your pride and joy might end up in a ditch!
Generally the screw moves in for a slower rebound and out for faster IE less damping.
Also remember to write down the stock settings so that you can go back if you cock it up .
On the back end push down through your bum and watch how fast the bike returns. Lifting yourself off of the seat by standing up, the seat should follow you at the same sort of speed (You have to do it fairly quickly!) If it falls away or pushes you up then the rear rebound needs some adjustment. More damping if it pushes, less if it falls away.
Compression damping is a little bit more complex, but more fun too! To set it up correctly, you need to ride your bike on the kind of road where you want it to handle best. Compression damping is the part of the suspension action most affected by riding style and weight. You want to make the bike absorb small bumps yet doesn't jerk forward or backward under acceleration or braking.
Its probably best to pick a traffic free route that you can do again and again. Experiment by making your adjustments a few clicks more or a few clicks less. Adjust it one end at a time. For the forks, does a click less, say, of compression improve comfort over bumps? what about when you brake hard? Is the extra see-sawing worth the extra comfort?
At the rear, does an extra click harder, say, than standard make the bike more comfortable over bumps or less so. What about squatting under hard acceleration out of a bend? again look for a compromise between the two.
Yeah... so why does this bother me - I've tried adjusting it before? - Or My bike doesn't have adjustable suspension! wtf?
Remember that if you think your bike isn't handling, it could well be just that you *think* the bike isn't handling very well. Have a go at riding around the problem first. If the bike pitches forward under hard braking, try not to brake as if every traffic light is an emergency stop.
If you really think there is a problem you might ask somebody else to ride your bike and give an opinion. Remember this depends on what they are used to too! If they ride an aprilia RS250, they are bound to say that your harley fat boy handles badly and vice versa!!
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another. |
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Dark
World Chat Champion
Joined: 02 Jun 2004
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Posted: 17:24 - 21 Apr 2006  Post subject: |
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Thats a pretty good effort MarJay 
However, it sounds like your emphasis is on ride quality and comfort rather than actual handling.
I tend to sacrifice some ride quality for braking, accelerating and cornering stability and also recommend putting tie wraps around your fork tubes to measure the amount your suspension is compressing under heavy braking.
____________________
My Bikes in order:- Yamaha RXS100 / Suzuki X7 250 / Yamaha RD350LC / Kawasaki
KR1S 250 / Kawasaki ZXR750 H2 / Honda C50 / Kawasaki ZX7R P5 / Kawasaki ZX10R / Suzuki GSXR 400 / Honda CBR1100 Blackbird & Yamaha FZR 600 |
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MarJay
But it's British!
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EuropeanNC30R...
Gay Hairdresser
Joined: 20 Jun 2002
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| Posted: 19:17 - 21 Apr 2006 Post subject: |
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G
The Voice of Reason
Joined: 02 Feb 2002
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| coolfox1 |
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coolfox1
Scooby Slapper
Joined: 14 Apr 2004
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| Posted: 22:56 - 03 Jul 2006 Post subject: |
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oh I'm confused ... 
not had adjustable suspension before, not dared touch it so far but I keep finding the front of the bike is loose mainly when I brake the thing falls forward too much, I want to adjust it but dont know if it's spring pre-load or compression damping force.
I get the rebound thing that makes sense, but the other two sound the same, can some one tell me in real simple terms what the other two do (like I'm a two year old pref !) |
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| MarJay |
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MarJay
But it's British!
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Old Thread Alert!
The last post was made 19 years, 52 days ago. Instead of replying here, would creating a new thread be more useful? |
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