Progressive Springs or heavier oil

[Sabre-t]

I just changed the oil weight. Kept the stock amount (measured from the top) and no extra spacers. Did this on the Voyager and a Honda Sabre, too. Made a huge difference in the feel and handling. I also have Gary's fork brace on the Voyager. The forks flex too much otherwise. No brace needed on my old Sabre. For the Voyager, I think that combo will do more for the front end than spacers, etc. without the fork brace. If more is needed, then add spacers, emulators, whatever, but I think most folks would be happy without going that far. Just my opinion, though.

But back to the OP's question as to why his bike is bottoming out. It's almost certainly old fork oil and some loss of what is there, even though he doesn't see a leak. Just changing to the Kawi recommended oil (~10 wt) would be an improvement over factory oil that has seen 50K miles, but a higher weight oil would certainly improve his situation.

[danb]

I know this an old thread, but I'm thinking about putting in the progressive springs in the front forks of my 04 1500 Nomad. What part number are you guys putting in. Is it the one that comes up on Progressive's website for the early 1500 Nomad's before they went to the cartridge? When I plug in 04 1500 Nomad they don't show a front spring. Also is everyone using the instructions on Gadget's sight? Thanks for any help
Dan



2004 1500 Nomad

[GeorgeHouston]

I went with Belray 7w

[andyvh1959]

A common mod in the past was to go with a larger volume of lighter weight oil. Number of reasons to do this: the space above the oil and under the fork leg cap forms an "air spring". As the fork is compressed the air is also compressed which acts as a compression damper. The "rate" of that damping action is based on the volume of air, so if you decrease the air volume you increase the damping rate. To decrease the air volume, increase the oil volume. The increased air damper effects to quickly slow the compression of the forks over a big bump with little effect on small bumps. The lighter weight oil is able to move through the passages more easily making the forks more responsive over bumps. The typical method to add oil volume is to take the fork springs out, then fully compress the forks, then add whatever weight oil chosen to within 3" of the top of the fully compressed fork legs. Then let the forks extend and install the springs.

The other method was to use lower rate per inch progressive wound fork springs. Again, to make the fork more responsive to small sharp bumps like expansion joints. But the higher rate air spring effect of the increased oil volume insures the forks don't compress too much near full stroke. Also the increased air spring effect helps reduce fork dive during heavy braking.

The other part of fork setup is to get the proper "sag" when the bike is upright and loaded. The preload on the fork springs determines the sag, and it should be about 1/2" to 1" maximum. Prop your bike upright, and note the fork compression unloaded. Then use a zip-tie around the fork leg just snug enough to move easily but hold position. Put the zip-tie on the fork leg just touching the top of the lower slider. Sit on the bike as you normally would in your regular riding gear. Then get off the bike and note how much the zip-tie has moved up. If it moved more than an inch, you need to add pre-load to the fork springs by adding a spacer between the fork spring and the top cap. A piece of Schedule-40 plastic pipe cut to the right length makes a good spacer. Or, get a proper diameter valve spring of the right length from an engine and install that above the fork spring.

All sounds like a lot of work, but once set up properly your ride and control will improve significantly. Some may say you can't add more oil volume without blowing the fork seals. Nope, the seals easily handle the slight increase in pressure. I have trailered many bikes where the forks are compressed by strapping the bike down halfway into the fork travel, and never had a fork seal blowout issue. The amount of oil installed by the factory is the minimum to lube the inside of the fork legs for the least possible cost. Also, less oil in the fork legs means less production time on the assembly line. It has almost nothing to do with fork seal ability.

[danb]

Thanks for the advice. I'll experiment with the fluid level when I go thru the front shocks.
Dan
04 1500 Nomad