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Why Adjust Suspension Set Up?


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Maybe this sounds like a stupid question. But considering I have never done a track day I don't understand what benefit adjusting springs and suspension has. In my view, the bike manufacturers build the bike so that every thing works the way it's designed to. So why mess with it? i can understand heavier riders needing to stiffen their springs and shocks, but apart from that if the suspensions sweet spot is in the mid range, why mess with it?

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No such thing as a silly question. :)

 

Basically, as the rider's skill and pace ratchet up on the street or track, the forces that act upon the suspension get stronger and have more of an effect. So adjustments may be needed to keep the suspension operating in the mid-stroke range. The rider's personal preferences and riding surface also play major roles the suspension setup for a given bike and rider combo.

 

For example on my r6; at my current height, weight, I fall within the range of the stock suspension/ergo settings for preload/damping(high & low)/rebound for street applications and it honestly don't feel too bad. However, if I take this bike to the track, it feels too soft for liking. The front nosedives hard, due to the increased braking forces (much harder than street) and the rear feels lethargic and unresponsive while on the gas (more aggressive than street). On the flip side, my preload/damping settings make the track suspension settings a bit on the rough side for casual street riding. Ya know... something a bit more forgiving for street use.

 

I hope that makes sense. Are you considering a track day soon?

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Well said csmith. I might add that production bikes are made with cost considerations as much as (if not more than) performance considerations, for instance my stock S1000RR had Brembo brake calipers but a Nissin master cylinder (I corrected that – an upgrade I would not have done for the street). So while manufacturing dollars spent squeezing out additional horsepower or torque may add to a retail price, many consumers of a street bike do not need (nor would want to pay for) SBK-spec suspension internals in their street bike. But if you are riding that bike on the track you just might end up getting fast enough that those factory internals don’t meet your performance needs as csmith pointed out.

 

To me, suspension work is the dark arts of motorcycle performance. I would recommend some reading like Andrew Trevitt’s book “Sportbike Suspension Tuning” or maybe Race Tech’s Suspension Bible by Lee Parks (haven’t read this one but it was recommended to me so YMMV).

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Another thing to consider. Suspension components age over time. Fork seals loose their flexibility, the oil gets old and parts get dirty with use on the road and on the track. All of these factors over time limit the suspension's ability to function as it was designed.

 

I took my one of my bikes to just get it setup for my weight and while they were doing the bounce test to set the compression and rebound the bike wallowed around regardless of where the adjusters were set. After the rebuild with fresh oil, seals and a good cleaning it completely transformed the way the bike handled. A bike that I had accepted as twitchy and easily upset because it was an exotic became amazingly more forgiving and planted. Wish I had done it years sooner! :)

 

As others have said the reason why the suspensions are adjustable is to account for different rider weights and to adjust for different track situations. Regular service of forks and shocks and correct adjustment gives you the best possible handling for your specific situation.

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When I started track riding I just rode around at whatever my suspension guy (he was a provider at the track) set up for my bike and I thought it was fine. But, after going through Keith Code's suspension drill, which is a detailed process of adjusting clickers to get the feel of all of the available adjustments in front and rear suspension, I got a much better understanding of how suspension adjustments can change the handling.

 

Now that I am comfortable making adjustments, I DO change the settings for various tracks. For example, Fontana needs more compression damping in front because it has some very hard braking zones and a particularly rough high speed bump coming down off the banking, which can cause excessive dive in front or even bottom out the forks. It also requires a lot of rear rebound damping (at least on my bike) to keep the back end from wagging around at high speeds riding through turn 2 and next to the wall on the main straight, and to stabilize it better under hard braking.

 

But when I take the same bike to Streets of Willow, I set the rear rebound to be very quick (less damping) because that track is lower speed, bumpier, and more technical so it needs a much quicker response from the rear - and softer on compression in front, because there is not much hard braking at that track and the softer settings make it easier to get a quick turn-in through the tighter turns and make the bike feel more compliant overall.

 

Tires can make a difference, too; a tire that has a very stiff carcass can make your suspension feel harsh, and suspension settings that are wrong for a certain type of tire can wear out the tire prematurely. For example, cupping in a rear tire can indicate too-stiff rear suspension settings. Dave Moss has some great videos about that, look for them on YouTube.

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Thanks for the replies. I guess I can just wont fully understand until I ride track. Csmith, I really want to do ... neigh... NEED to do a track day. It's an experience I think I'm lacking and while I don't believe for a moment I have learned all I can on the street, I strongly feel that track riding is a skill on its own that I need to acquire to improve on the street.

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Darth,

 

A simple suspension setup is around $80 if you don't need springs. It's transformed SEVERAL of my bikes and the difference is even noticeable on the street. It's like getting a new bike. Just a word of caution though. Most bikes from the factory come with very light springs. If your are on the heavier side of the spectrum be prepared for new springs. Three springs and adjustment on a street going R6 that I have ran me around $330.

 

About feeling strongly that track riding will improve your street riding. That was part of the motivation that got me out on the track as well. It's amazing the confidence it builds. Knowing that you have taken sharper turns at higher speeds makes even unfamiliar roads seem much less intimidating. :)

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Although there is some great info here, I'm not sure the original question as to WHY you should mess with your suspension and get it set up correctly has been answered.

 

When I quiz riders on what qualities they most want from their motorcycle when they're riding, the most frequent answers are stability and good traction. Suspension plays a key role in both. The main purpose of the suspension is to keep the tire's contact patch firmly in contact with the road surface (it's not there for comfort). The more contact it makes, the more traction you will have. If your suspension isn't set up correctly, it won't do as good a job in keeping that contact patch on the ground, thus reducing your available traction.

 

As for stability, your suspension should only move as much as it needs to to keep you contact patch on the ground. Any more movement and it will feel bouncy and affect the bike's stability. As the suspension moves up and down over bumps, your wheelbase changes a bit, primarrily because your fork is at an angle. When your fork compresses, you wheelbase gets shorter (think of a chopper). When leaned over in a corner your steering head must change it's angle to stay on your line as the wheel base changes (longer wheel base requires the steering head to turn in more to maintain the same radius. Think of a Limo vs. a Fiesta on the same tight circle and how far you have to turn the wheels). More suspension movement (bouncing) causes more steering head movement. If you get tight on the bars you will transmit the bar instability through to the entire bike causing it to wallow around and feel really bad (hence the "Relax" drill in CSS level 1). This is a very simplified and incomplete stability lesson but it serves to make the primary point that suspension affects stability..

 

Even if your suspension isn't ideal, good throttle control as taught in Twist of the Wrist II and at CSS is the key to getting the most traction and stability out of it that it can possibly deliver (it's the key to getting the most out of great suspensions too). You can have a MotoGP bike set up by specialists but if your throttle control is bad it will never feel good. You could spend a lot of money chasing problems that you yourself are causing. So, my advice is to get your stock suspension adjusted for you by someone who knows what they're doing and it will be good enough for a very long time. If you want to make any upgrades, do it to your training so you can learn to get the best out of whatever suspension you have.

 

Benny

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Thanks Benny that was a very detailed and very thought out answer, I really appreciate you taking the time, as I do you hotfoot.

 

I still think you guys might have the wrong impression from this post though. I'm not asking because I'm thinking about modding my bike or changing my set up, I'm just trying to understand why people do it. Your answer Benny, covers that very well though. I fully understand the concept of the wheel base getting shorter and how the suspensions job is to keep the contact patch the right size and in contact with the ground.

 

Sometimes I think people make unnecessary mods to their bike just to make it look cool or for bragging rights or what ever. Prime example is quick shifters, they are a complete waste on road bikes. But that was pretty much the thought process behind the question, it's just understanding is the adjustable suspension and pre-load a necessary feature on modern bikes or a vanity accessory?

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It's completely needed. Even on the street in my opinion.

 

I own an older Yamaha FZR400 that was made before adjustable front forks were common place. In order to prepare my bike for the track I had to open up the front forks and use metal shims to set the preload for my weight. I don't have any dampening settings at all at the moment.

 

I'll agree with you for a moment with your sentiment of "vanity accessories". One just has to look at some owners with Carbon Fibre parts that save a few fractions of a gram in weight to see that. This is not one of those.

 

Preload adjusters help set the bike so the forks are in the center of the travel range and that gives you the "maximum" amount of suspension travel both up and down by keeping the forks and shocks in their sweet spot. Compression settings help make the bike more stable in different track situations.

 

If you want a quick demo of how important the adjustments are do this. Set the bike at max preload and go for a careful ride. Come back and set it at minimum preload and do the same. Then get a tape measure and correctly adjust the sag at 30mm for the track (watch Keith's video on how to do the adjustments). You will notice the difference instantly each time. At max preload the bike will be VERY harsh and bumpy and you will be bottoming out the suspension. At minimum preload the bike will be topping out the suspension and will occasionally skip over the ground. Setting it at 30mm will put you in the center of the travel range and the suspension will operate as designed. You can play the same game with your compression settings as well. Just keep accurate notes of the original settings if you want to play around and be a bit cautious at first when riding with any new settings (a suspension bottoming out or topping out will make the bike loose traction in the right situation). As Hotfoot mentioned in one of Keith's books there's a suspension setting drill that steps you through setting the suspension in a more controlled way so you can feel the differences in settings. This is something I plan on doing in the future. At the moment I accept the default settings that my suspension guy sets for my body weight and the track I'm riding.

 

These settings are not just for racers and tinkerers. They were put on these bikes to adjust for different rider weights and different conditions that these bikes were designed to be used in. Just to give you an idea of how important these are. Harley Davidson has adjustable suspension on a few of their models such as the Sportster XR1200.

 

Speaking of Harleys. I'm VERY much considering taking my 800# Harley Fatboy up to Traxxion Dynamics for new springs and some upgrades. Even a big cruiser like a this can benefit by correctly setup suspension.

 

IMG_20120422_152249.jpg

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I think getting your settings right on any motorcycle's suspension is important. With only two wheels, traction is critical. I met a guy who was complaining about how much the rear of his gixxer liked to slide. He was then purely a street rider & not terribly aggressive so it shouldn't have been a problem. I checked his suspension & it was way too stiff (pre-load, compression damping & rebound damping), especially in the rear so I set it up for him properly. I've since gotten him addicted to the track but even though he's much faster now, the rear of his bike stays planted on those same settings. Previously, the tire was just skipping over bumps & holes and not being allowed to follow the road.

 

Basic suspension setup isn't vanity but there are plenty of posers who claim to be suspension experts. You can usually spot them because they'll have a full race Ohlins setup on a bike that's never been to the track. Find a reputable shop in your area to get it done to ensure it's done right. Post your area & someone here will probably make a recommendation.

 

Benny

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