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ERGONOMICS: Making Your Bike Fit You - Part Two


MXEditor

er·go·nom·ics: a science that deals with designing and arranging things so that people can use them easily and safely: the parts or qualities of something's design that make it easy to use (Webster).

 

In our previous installment, we talked about how to improve the ergonomics of your machine in a number of different ways, including some simple yet effective methods of changing the dynamics of the rider to bike interface. These included products like longer/shorter brake and shift levers, bar risers, larger/offset footpegs, seat modifications and handlebar options.

 

In the world of riding off-road motorcycles, the ability to “get your feet down” so they can support you when unstable is paramount. Without it, riding in off-road conditions is extremely difficult as well as unsafe. Because of the serious nature of this issue, we’ll focus on items like lowering links and the associated family of products because this is the “last stop” for shorter riders looking to modify their machines for optimum control.

 

The geometry of a motorcycle is a precise thing. Modern manufacturers use sophisticated computer testing algorithms coupled with CAD/CAM modeling and human interface testing to arrive at a product that offers maximum safety and stability. Frame specifications like rake and trail become of paramount importance and trying to preserve these ratios and setups is important when modifying a motorcycle to be lower to the ground.

 

When modifying the rear suspension for a shorter seat height, it’s common to use a lowering link. Simply put, this is a replacement for part of the stock linkage that allows the motorcycle to sit lower and offer a shorter seat height. But these linkage modifications don’t come without drawbacks…behavior such as headshake and insufficient ground clearance can become problems if not addressed when adding lowering link.

 

Some more serious riders and off-road racers don’t like lowering links for a variety of reasons and some of them make sense. But the modifications they champion such as spacers and shortened forks and shock/springs also have their drawbacks like limited suspension travel, complexity and expense.

 

My personal feeling is that if you are an extremely fast amateur or professional racer, you may want to consider trying to keep your feet up and going faster as opposed to changing the geometry of your race machine, but if you are a weekend warrior, trail/enduro rider who needs help getting your feet down, this could be an answer for you. Keep in mind these lowering links normally cost under $200 and on some bikes the installation is under an hour!

 

Different manufacturers offer lowering links and also items such link guards, which can offer a slight bit of lowering coupled with added protection for exposed linkages and we’ll look at a few of these offerings.

 

Devol Racing has been offering lowering links for some time and is known as a leader in this segment, offering links for both motocross and enduro-style machines with up to 1.5” drop. Devol claims many features for these units, including being lightweight and stronger than stock as well as improving front end stability and rear end tracking.

 

Ride Engineering offers both lowering links as well as full linkage assemblies and they claim that the full assembly can improve the suspension action and handling entering corners (by holding the shock up in the stroke more) and is more plush on acceleration chop exiting the turn. By offering both components instead of just the outer or inner one, ride height remains unchanged (0-2mm drop depending on year).

 

ProMotoBillet offers the Fastway Linkage Guard, which is a different take on a lowering link and offers both linkage protection and a modicum of adjustability for riders. Fastway claims multiple suspension adjustments: stock, .6mm, 1.3mm and 2mm, potential for lower seat height, improvement in front end steering and cornering, protection for your expensive shock and linkage from damage all resulting in better over-obstacle traction.

 

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Photo: Fastway Link Guard

 


We took some time to ask around the business and see who would be a good resource for some of this information and one name kept coming up: Norman Kouba. Norm runs Kouba Link and offered a wealth of information on this subject. Let’s get a bit of his insight on lowering links and the associated benefits and drawbacks of using them.

 

ThumperTalk: What is a lowering link and what does it do?

 

Norm Kouba: A lowering link is a longer than stock link (or links) that lowers the rear of (your motorcycle) by changing the starting point of the swingarm arc. In most cases (lowering) links are used to connect the frame to the rear suspension and swingarm on linkage style rear suspension motorcycles. The advantage of the linkage style suspensions on most bikes is (that) you have a rising rate suspension that gets stiffer the farther you get into the travel.

 

TT: What happens to the bike's geometry when JUST the lowering link is used?

 

NK: Installing a lowering link only lowers the rear so if the same geometry is desired then the front requires some attention. Just keep in mind that lowering the rear more than the front slows the steering but also makes it more stable on the straights and vice versa.

 

TT: What can riders do to "equalize" their bike's suspension after installing a lowering link? Can riders get the rake/trail back close to stock if needed?

 

NK: In most cases the fork tubes can be slid up (in the triple clamps) enough (to compensate) as long as the OEM recommended race sag or less is maintained. Usually the longer links put more leverage on the rear spring so the spring requires more preload to maintain that amount of race sag.

 


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Photo: Kouba Link Installed

 


The best advice is set the bike up for the conditions you ride most as the stock geometry may not be the best for all riders and/or conditions. We usually recommend less race sag for the best performance but that does take away from the lowering amounts of the longer links.

 

Lessening the race sag will put the suspension in a less progressive part of the travel which is plusher over the small stuff, and also gives you more travel remaining for the bigger hits.

 

TT: What other things can be done to lower a motorcycle for shorter riders?

 

NK: Not a lot of things can be done economically other than cutting down the seat or lessening the race sag until the feet touch the ground. The problem with those two (solutions) are you either harm the riders bottom or you harm the bike's suspension. You can also slide the fork tubes up until they almost touch the underside of the handlebars but be careful going much more (by installing handle bar risers) as you may not know how far the fork tubes can be slid up without allowing the tire to hit the fender when bottomed out.

 

The other options are lowering links, shortening the shock and/or forks internally, cutting down the rear subframe Ricky Carmichael style, or going to smaller diameter tires. That is all that comes to mind other than built up boots!

 

Conclusion

 

In conclusion, although there are certain drawbacks such as decreased ground clearance and potential rake/trail issues when using these products, these can be compensated for with some due diligence. We believe that professional racers and faster amateur riders may not want to explore this option and could be better served with shortening the suspension components individually, but for the average rider, these lowering link solutions can offer an inexpensive and easy-to-install answer for providing a lower chassis for shorter and beginner riders.



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You state Devol lowering links lower a bike up to 1.5".  You state that the Ride Engineering link lowers the bike 0 - 2 mm.

Also that the ProMotoBillet product lowers the bike a certain MM.

Are you sure the last 2 should be also in inches and not mm?

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You state Devol lowering links lower a bike up to 1.5".  You state that the Ride Engineering link lowers the bike 0 - 2 mm.

Also that the ProMotoBillet product lowers the bike a certain MM.

Are you sure the last 2 should be also in inches and not mm?

 

The 0, .6, 1.3, and 2mm figures are the offset from the stock length of the link, not the amount of drop. If you look at the picture you can see the eccentric insert on the left of the link.

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Some folks I've discussed lowering with are really concerned about handling changes that lowering links might cause. I only have a 31-inch inseam and I've done it on several bikes that I use for brisk trail riding.  I find that as long as the front end is lowered about as much as the rear, there is not a problem -- other than the possible need for a stiffer spring on the rear shock to make up for the increased leverage that lowering links create.

 

I've found that if you can dial in the original sag amount, you are probably OK.

 

One alternative for lowering the rear not mentioned is the adjustable-length-style link. A firm named "Soupy's" is the leader in this technology.

 

The advantage of having adjustable links is simple: You can play around with ride height and its adjuncts until you get a height that works best for you and your riding style. There are real advantages over fixed-length links. If you don't need a full inch lower, you can dial adjustable links in to some height that is only half or three quarters of an inch lower than stock. I

 

Good article and a great myth-debunker for those who'd like a lower ride height.

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I put the lowest drop kouba link on my 2012 klx250s dropped the front forks and set sag at 4". Bike handles better than stock version, easily flat tracks washboard forest road corners and climbs rocky terrain better than my old KDX 200 with a professionally done suspension. Money well spent

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As he mentions briefly, a change in spring rate and probably valving should come with a lowering link. If you change the linkage ratio you need to adjust the valving to compensate for the different amount of travel in the actual shock using the new linkage ratio.

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