TT 250 USD fork damping mods?

[superjocko]

Hello all,

Sorry I haven't been very active lately. Life outside of China-biking has been taking its toll for the past couple months. Plus, it's been hotter than Hades lately, which doesn't get me too excited to ride or work on the bike.

Anyhow, I've got a new project in mind that relates to the quality of the fork damping, or lack thereof, on my bike. I've noticed from day one that the forks on this bike aren't very compliant on square-edged hits. I have pretty severe arthritis in my wrists and elbows so it makes this particularly noticeable and problematic for me. I understand going in that these forks only have 6 inches of travel, so I'm not expecting a miracle. I would like to get them to be more compliant on high-speed (suspension speed) hits though.

I've changed the fork oil to Maxima 85/150 5WT Zero Drag Formula High Performance Fork Fluid, which has a very low cSt (kinematic viscosity) rating. I also put Silkolene silicone formula suspension grease between the lips of the fork seals to help with stiction while I had them apart for the fork oil change. There was some improvement, but not nearly as much as I'm hoping for.

I've got considerable experience with rebuilding and tuning motorcycle suspension components on Japanese and European bikes, but so far I have next to zero familiarity with the internal damping components of these Chinese forks. The service information and exploded parts diagrams are pretty limited or just non-existent. Beyond instructions on changing the oil and replacing the fork seals, there just doesn't seem to be too much out there.

I'll be taking these forks completely apart, down to their innards and seeing what I can do to make the high-speed compression damping significantly lighter than it is currently. As they are now (stock aside from the lighter fork oil), the front fork goes into what feels like just short of hydraulic lock on high-speed hits (rocks and square-edged holes, etc.) I've even quantified this to a degree with a zip tie around the sliding lower leg. While I can use fairly near full travel on "g-out" type compression (low-speed), the fork typically won't go much past even half travel on high-speed hits. Knowing that resistance to flow through an orifice increases as a square in relation to speed, I'm suspecting the damping function of these forks is pretty primitive.

These forks do have rebound damping clicker adjustments, but their functionality and effectiveness is questionable at best and seems to have little if any affect on the compression damping, although (theoretically) they should unintentionally affect at least low-speed compression damping. Setting them either fully soft or fully hard, or anywhere in between, doesn't have enough effect to make them useful in any way relative to compression damping.

I'm hoping that I may be able to adapt some form of a tunable valve stack that increases the volume of flow in relation to the speed of the flow like most modern suspension valving systems do. Race Tech "emulators" come to mind as a possible solution, if they can be adapted to these forks.

So, with all that out there, my question is: Does anyone have any experience with the internals of these forks, and/or have you made any modifications along these lines? Additionally, if anyone has any service information or detailed exploded parts views (CSC doesn't) those could be of immense value in figuring out my plan.

I won't be starting in on this until we have some cooler weather as I don't feel like sweating in the afternoon sauna that is my West-facing garage. I'm more in the -formulating a plan- phase at the moment. When I do start though, I'll document my project with photos and share the results. In the meantime, any info or experience you might be able to share would be greatly appreciated.

For what it's worth, the rear suspension is just fine as-is after having set the preload on the shock spring and damping adjuster to suit me. No complaints from me on the action of the 6-1/2 inches of rear travel. The damping adjuster on the rear shock produces very noticeable changes and makes the rear suspension work great for my needs when set about halfway through its range of adjustment. Those forks though... Ugh!

Thanks in advance for any replies that may help me plan out my next steps.