How subtanks really work..

From that post on thumpertalk it looks like the whole bimba setup is cheap to copy and try out,someone posted all the part nos etc.

Ive have never rode with a set of tanks but want to try a set out, they will however interfer with my quick adjusters on the showas so i have held off at present.

Yeah, on the post you see some pictures of hand made projects that look more like hot water tanks. I'm pretty sure the volume must be way too big. The bad thing about those projects is that if you don't like it you are left with butchered fork caps. As soon as I can get the precise volume of the too-tech unit (supposedly around 50cc), I'm gonna start working on some spare renthal handlebars. Figuring out the wiring and finding the right clicker adjuster will be next. I hope I can find some trick aluminum couplers and adjuster. I'd hate to have to carry big industrial plumbing.

thats the thing that has put me off so far-the plumbing etc.Trouble is anything too small might be too weak for mx and woods riding.Those nylon tubes look to weak IMO.As for the caps i dont think they are that expensive to replace and you can get a new plug made the same thread as the adapter.

The thing that concerns me, even with the too tech or bimba is, from my understanding is that it is a single cylinder. As Marcus pointed out on the bars, how can you be assured that there will be equal disburstment back into the forks. It seems to me just leaning the bike in a turn could possibly allow more oil to drain back into one fork then the other. Now if there is separate chambers with in the tank, then I can see equal fork oil being returned to both sides.

Russ

Originally posted by Jeremy Wilkey


So guys work on something better... Not cheaper.....

BR,
Jer

Click to expand...

LMAO...The most awesome quote of the year!

Heres a laugh for you . the first chamber project I had was a woodsies 00 CR250 that he was running one summer . We were trying to get a real supple fork with good bottoming resistance . We took the CRs triple clamp off and sealed off the front of each frame spar and then plumbed the fork caps to the spars. We used firm plastic hospital type tubing . We purchased in line filters like the kind your dentist has on his air powered dental tools and thought that we could keep the oil out of the spars . We ran like 420ml oil or so and ended up with a really nice fork after we tried tuning the lines with ground down main jets pushed inside the tubing . We thought about using a check valve but never followed up. The forks seemed way plusher but seemed rather McGuyver in retrospect. I think the chamber was too big actually. I guess we also indirectly did it on a KTM (ZOKES)once to try and stop the seals leaking We plumbed the fork tops into the frame instead of adding bleeders on the caps. Those enduro bikes handlebars can be so busy that you cant find the bleeders very easily.We thought the forks were pumping up so bad We even tried a automotive PCV valve inline on the KTMS ,It actually worked really good in rocks and roots.The PCV valve was a good idea except that I though maybe The forks actually Sucked dirt in the seals upon rebounding. Actually those seals probably worked better with a bit of pressure on the pushing them against the tubes. I guess it was mainly dirt in the seals that was the worst thing . One Husky guy would get sprayed with oil when he rode a longer event and the seals blew out and sprayed oil all over his jersey. We were trying alot of things like double stacked seals. Double springs on the seals etc.First the blue seals then the black seals.Nobody really liked the looks of fork boots until they tried them and the forks stayed clean and didnt leak much. P.S. I know someone will read this post and say what a jackass, but at least I can say is I learned something. CHEERS DEAN

If you dont try, you dont learn-quote for today.

and just remember, the most important discovery known to man was found by growing some mould on a saucer and forgetting about it and leaving it on the window ledge for a few weeks- ive seen a couple of noble prizes get given from people messing up- one guy didnt bother doing his chemistry the right way (ie being lazy and not purifying things properply). something went wrong, he looked into it and opened up a whole new branch of science!

One time I had some science growing between my toes , does that count?

As far as I know, the bimba tanks come with a piston in them, people were discussing pulling out the rod and just jbwleding the piston in the center of the tank, which would create a 'perfect' seal inbetween your new individual fork based tank. You'd have to add two bleeders, and if I was going to try it I'd try adding a slight angle to the inside of the tanks(lose some cc's, gain possibly more oil coming back in?). I'd try it but I don't want to rape the fork caps on my xr4 just yet.

My system

The system I built uses a single bimba reservior/tank in the center. I cross plumbed the forks and ran them both into one side of the tank and mounted a bleeder in the other side.

For metering, I used the bimba flow control valves that do "freeflow" back.

Here is what you have to know about the bimba valve. While it does have a "check" in it, it doesnt "free" flow back. There is some resistance in the backflow because the check valve is an elastomer type, almost like fork seal, type seal.

When you take this into consideration, you have a static adjustment for the "rebound" airflow. Probably not ideal, but Im still experimenting.

As far as sizing of the tank goes; I had played with the oil voume trying to dial the bottoming and plushness. I found my best plushness at 350cc (03 CR450F) but the bit hit/bottoming resistance was almost zero. At 400cc the bottoming resistance was spectacular. So I figured I wanted to add roughly 50-60cc of air volume to each fork with a valve. My tank measures 106cc, then ya got the lines. So Ive probably got a total of 120cc of volume.

After riding my system which is basically a TooTech style setup, the only thing I encountered that I hadnt anticipated was it seems to work best with one extra click in the rebound.

I share the opinion of Mr. Wilkey on the plastic tubing aspect. It cant, and isnt very durable. Although, it does and can work. My first system used this, while I was still undecided on how I would plumb my set up. I rode it with the plastic tubing once, and it worked fine.

One thing I would like to address is oil migration or the lack of the tank setups on the Showa fork. I rode my plastic tubed set up for an entire day and had zero oil migration. I think this will be unique to the Showa because of the route the air has to take to get out of the outer chamber. It vents through the blowout holes in the inner damber which works like a baffle apparently. As most tuners will tell you, when you do the oil change on a Showa you dont get much out of the holes in the inner damper and the volume of air passing through those holes is significant when your changing the compression ratio, but not in terms of volume that could be carrying an oil mist.

I've got some experience with the Enzo setup. I had it on a 426 prior to me picking up the CRF. I didnt play with the Enzo set up as much as I should have. I also think that they may have gotten the oil level too high on mine simply because I couldn't tell the difference in the fork at all, or the valves were closed too far or something. I wasnt happy.

At any rate, the "damping spike" that I experienced on the CRF with the oil level at 400cc is gone. Bottoming is gone and it seems to work great.

Also much of the sub-tank hackery that NoHand is/was refering to is on Thumpertalk, and I'll agree there are some really ugly things happening over there :eek: