Some people need to lower the bike to be able to get their feet on the ground. Others want to lower their bike to attain a certain look. Either way, lowering the bike causes 2 problems. First problem is the reduced cornering clearance. The second is limiting total travel. With limited travel, it becomes very important to set up all other aspects of suspension tuning correctly because there is little room for error.
Lowered bikes can be dangerous, especially if the rider pushes the limits of cornering or speeds. I read one report where a guy’s kick stand caught on a manhole cover and threw him off the bike.
Last year, I was following a $30,000 custom bike with lowered suspension. The guy was getting throw off the seat just going over normal size bumps. He hit a big bump while in a curve, almost lost control and almost ran off the road. This was at only 45 mph.
In order to get lowered suspensions to work, you must use stiffer shock springs. Stiffer springs provide a stiffer ride. Carrying a lot of weight, such as 2 up riding, generally means using a shock spring that is so stiff, solo comfort is severely compromised. Or, if you get a spring soft enough for a solo rider, it will probably bottom out too much when 2 up.
However, IF the spring has long transition zone, IF the initial and final spring rates match rider weight, and IF the rider goes slow enough and IF he avoids major bumpy roads, it is possible to get a reasonable ride. I guess I should add another IF. IF the rider has no clue what good suspension really is, anything is better than stock.
Sportytrace is a 140 lb rider who needed to keep her Nightster low so she could keep her feet on the ground. We accomplished this by using the 13.5” 1200 S shocks which have a light 54/78 lb/in spring. The spring matched her weight, but in order to get her feet to the ground, we had to use 1” lowering blocks. This proved a very good combination for her.
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Combining the 12-3/4” Road King air shocks with the 1” lower block is another good combination to carry a lot of weight while keeping the bike low. Be careful to not exceed the factory weight limitations of the bike itself.
There have been questions about how using lowering blocks affect the spring rate. The answer is it all depends on too many factors to predict accurately. I experimented with 1” lowering blocks. Some shocks smoothed out a little bit, others didn’t.
When you lower a bike, you must verify you have enough tire clearance. If you jack the bike up and take off both shocks, and then lower it very carefully, you can see how low it can go. Measure the shortest distance between the shock mounting bolts. The shocks bottom out and that limits how low the rear of the bike can go. If you take off one shock and lower the bike to bottom out the shock, you can verify you have enough clearance left over.
Early years of Rubbermounts had electrical wiring under the rear fender that the tire can rub on.
Nightsters have a reflector under the fender that will hit the belt guard. Early shocks from Progressive had too much travel and broke off the reflector. The newer shocks have less travel. So be careful if you buy older shocks for a Nightster.
If you lower the front end by lowering the triple clamps, it is possible the lower fork tubes will hit the lower triple clamp when the forks compress fully. The first 07 FI bikes had front fenders that hit the voltage regulator. Something you want to avoid.
Lowering, or raising, a bike may make it necessary for a kick stand of a different length.
There are 3 lowering kits for forks that I am aware of. Harley offers their own kit with a new spring and damper tube. This kit is not very common. I suppose because it is too expensive, especially if you have to pay the dealer to do the work.
Progressive offers 2 different lowering kits. The original 10-1560 kit uses the standard 11-1527 main spring, but includes extra 1’ springs called lowering springs. Harley calls them rebound springs. Others call them top out springs. These springs ride on the damper tube in between the upper and lower fork tube. Stock forks have only one rebound spring which softens the hit when the forks fully extend and the fork tubes hit against each other. Adding 1 or 2 extra lowering/rebound/top out springs pulls the upper fork tube farther down into the lower fork tube. The big disadvantage is you have to take the damper rod out to add the extra springs.
Progressive’s new kit is 10-200 “Drop In” kit. In this kit, the main fork spring is replaced with 2 different springs. You do not need to remove the damper tube to do this, just pull out the original spring and drop in the new springs. The long spring is the main spring which supports the bike’s weight and compresses and extends in response to road bumps. The other spring is very short and weak. It is so weak, just the weight of the bike will cause it to compress 2” until the coils hit each other. This is called coil binding. When the coils hit each other, the weak spring stops compressing and becomes a solid rod, leaving the other spring to do all the work. You can see pictures on Progressive’s web site.
I have no experience with either lowering kit. Neither offers the adjustability of the Works Dual Rate spring kit.