The longer your links are, the more they lower your seat, and the more they affect your suspension: The rear end gets too soft.
Lowering links increase the leverage, or compressive force, applied to the shock as it travels thru the stroke. The different components that make up the rear suspension linkage are very well engineered and balanced by the factories. Changing any one piece affects the overall function. The lowering link introduces a longer lever arm into the heart of the linkage mechanism, applying greater force to the spring and compression damping circuits. They make the ride more plush initially, and much softer near the end of the stroke.
The links that drop the seat more than 1” usually work good for someone who doesn't ride really hard, like a dual sported bike that sees dirt roads and trails at moderate speeds. But when you turn up the speed, or hit rougher trails, these links will soften the rear end too much. If you are frequently bottoming your suspension, you’ve got too long of a link for these conditions. Now the fun part begins: Tuning. The longer links are a fairly aggressive modification to your suspension’s design, you’ll have to spend some more time and money to make it ride right again. Although this is one of the easiest ways to get your feet closer to the ground, the suspension action is greatly compromised.
For more aggressive trail riders, the links that lower 1” or less will usually work OK, without softening your effective spring rate too much. With the links that lower more than that, the ride gets too soft for you: The bike will most likely bottom out hard on your bigger hits, especially when jumping, and in deep compression G-outs like crossing a wash. If you’re having these problems with one of the shorter links, the following suggestions should help get your butt bouncing back under control. Any lowering link for heavy riders, or race speeds, can easily overpower the shock and it will blow through the travel.
The rear end really needs to be stiffened up. The easy adjustments that you can make are somewhat limited:
Adding Preload to the spring doesn't change the overall strength of the spring, it only affects the initial stiffness, and can seriously affect steering. Preload is the “Race Sag” adjustment, and not the proper way to correct for the lowering link effects. And the “Free Sag” measurement, for determining proper spring rate, can’t be used with a link. It will measure out that you need a softer spring when you really need a stiffer one.
A Stiffer Spring may help, at least it sounds right in theory. But the increase in force applied to the spring isn’t necessarily linear, it varies with different bike models, and the force can increase through the compression stroke. As I said before, you’re messing with the heart of the design. While a new spring alone isn’t guaranteed to get your good ride back, it can help a lot. Another important point: Have you checked to make sure that you have the correct springs for your weight? Springs that are too soft initially will compound the link issues. Check out the RaceTech Spring Rate Calculator, and figure you will need to add at least a couple of steps heavier. (I tried a 1 1/4” lowering link on my Suzuki, went up from the stock 5.3kg to a 5.7kg, it wasn’t enough.) The link only affects the rear spring, you don’t need to get stiffer fork springs to match if they’re good now.
Adjusting your Compression Damping will help, but you are limited by the range of the adjusters, which might not be enough. Turn in your compression adjusters a lot, high and low speed if your shock has both. These adjusters really affect the ride, so you will probably need to play with them a few times until you find an adjustment that you like. If you need help understanding how to tune your suspension, the ThumperTalk store sells a good DVD on the subject. Too much compression damping and a weak spring will make your bike ride terrible.
Another option is to ship your shock off to a tuner, who will take it apart and change the internal damping shims to a stiffer moto or SX like ride. I've spoken with a couple of tuners about this, they didn’t like tuning for lowering links, they prefer to shorten the shock stroke to lower the seat height. That service is more expensive than a simple link modification, and you will lose some travel. Many riders that have tried both methods preferred shortening the shock and forks, and resold their links.
The factory designers aren’t idiots, they’ve designed a good working suspension, and the linkage components are balanced to each other. The real problem is just that they are all too tall. If they had short legs like us, we’d get a good fitting bike off the showroom floor. Anything we do to lower the seat height, afterwards, will have an effect on the quality of the ride. If you can’t make your bike ride right with the lowering link, you do have some other options you can try. Read this article about Lowering your seat height for more ideas.