Inverted fork preload adjustment ??

[Bill Hilly]

I have a Brozz 250 on order, and it has the inverted forks. I saw an interesting post in the sticky from MegaDan ,in which he speaks of adjusting preload. I am pretty sure it was for convention ,non inverted forks. Do any of you heavier Brozz riders tweek your inverted forks ? Any advise ( besides the obvious, loose weight) for a 260 lb rider? I have been dieting since I decided to get a bike. I hope to be lighter by the time Spring weather gets here.

[franque]

PVC spacers on top of the fork springs, adding a bit of compression.

[Bill Hilly]

Originally Posted by franque

PVC spacers on top of the fork springs, adding a bit of compression.

Can this be done with the inverted forks from the top?

[tknj99]

That would be the only option, from the top.. do not, i repeat, do not make the mistake i did by unscrewing the retainer bolts at the bottom of the fork tubes...
You should be able to open each fork up from the top, remove the bolt and then spacer and spring and do this procedure.

[david3921]

Originally Posted by Bill Hilly

Can this be done with the inverted forks from the top?

Nope. This can only be done on standard forks like the ones on a Hawk.

[david3921]

The first step in improvement is finding out how much fluid is in each fork. This involves disconnecting each one and pouring out and measuring the oil in each fork. Some have found them to be different. They should be the same. My old bike required 330 ml in each fork. You'll probably want to to a heavier weight when replacing the oil. Do a search here or YouTube on replacing fork oil.

[Megadan]

Originally Posted by david3921

Nope. This can only be done on standard forks like the ones on a Hawk.

Preload can be added to any fork spring setup, even cartridge style forks can have the preload adjusted.

The difference is in how its done. The traditional forks are simply the easiest to do it with because of how they assemble. Inverted forks have a few different methods for how the springs are installed, but the idea behind it is no different - installing a spacer that reduces the installed length of the spring, adding additional spring tension when the fork is at full extension.

[david3921]

Originally Posted by Megadan

Preload can be added to any fork spring setup, even cartridge style forks can have the preload adjusted.

The difference is in how its done. The traditional forks are simply the easiest to do it with because of how they assemble. Inverted forks have a few different methods for how the springs are installed, but the idea behind it is no different - installing a spacer that reduces the installed length of the spring, adding additional spring tension when the fork is at full extension.

Agreed. I was replying to this; "Can this be done with the inverted forks from the top?"

Adding spacers would require a bit more disassembly on this style of inverted fork.

[old_airhead]

Any parts diagrams available for the inverted forks?

[david3921]

Originally Posted by old_airhead

Any parts diagrams available for the inverted forks?

Check out post #8 here;
http://chinariders.net/showthread.php?t=27687

When I get some time, I'll search for my pictures from my MCM post and get them to this site. This isn't the first time I've had to reference back to the post. Current forks should be pretty close to what was on the bike in 2009.

[david3921]

Originally Posted by david3921

Nope. This can only be done on standard forks like the ones on a Hawk.

I want revisit this. The actual answer is Yep....but not very easily. Referencing Dan's post, preload can be added after removing a certain number of parts on an inverted fork. The spacer needs to be located in one of 2 possible locations. The locations are either at the bottom of the fork, under the spring, or on top of the spring. Since a spacer on a conventional fork sits just under the top cap, it's pretty easy to cut a bunch of different lengths and swap them out in between test rides. Not so with an inverted fork. Also, while the spacer on a conventional fork can be solid, i.e. a steel or aluminum dowel, a spacer on an inverted fork needs to be a sleeve to allow for the cartridge the runs the length of the fork.

Apologies for the inaccurate post.
__________________

[old_airhead]

Since I had changing the fork oil on my list for winter maintenance for my 2020 Hawk DLX, I decided to take apart the forks, mainly because I've never worked on inverted forks before. I wasn't able to find any parts diagram of the internals. I did find 'AOK' embossed on the lower axle mounts. It looks like AOK makes mainly bicycle forks. I haven't found any source of parts for the forks. Here are some observations I found while taking these fork legs apart.

When I disassembled one of the fork legs I found that you can change the oil and add spring spacers without removing the bottom axle mount casting (held on with the bottom allen bolt) from the fork tube. Getting all of the oil out is a bit of a pain because of several places the oil sits. You'll need to hold the fork leg upside down and pump the 'cartridge' rod to get all of the oil out. I recommend that you don't remove the axle mounts to just change the oil or add spacers. If you do remove the axle mounts, which bolt to the cartridge, you need to be careful when reinstalling the bold through the axle mounts to the cartridge to insure that the flats on the cartridge engage properly with the bottom of the fork tube. Also, do not remove the slider from the fork tube unless you need to change the seals. If you remove the slider (the gold part) from the fork tube you will have to remove the axle mount to reinstall the slider - the slider must be installed by sliding the fork tube (bottom of the tube) into the slider from the top of the slider, or you will ruin the slider bearings. Not very clear, but you should look at the pictures.

I measured 260cc oil from each leg. Probably there was at least 5 cc of holdup in the leg.

[Shawnd84]

What size would a spacer need to be to adjust preload on these usd forks? Many say PVC but what diameter? I know the length would change based on the amount of preload desired...

[franque]

Nobody specified yet, but if you're going to be disassembling it anyway, it wouldn't be too hard to measure.