Dan, Thanks. That makes sense, I had my force converter out and wast trying to understand how to get the math right. Adding both forks, as you stated puts them right at 9N per spring.
This thread has ended up helping me alot. My front spring rate is where it needed to be. Still hate the front end feedback right now, even after putting a Power cup on.
Maybe the valving can be improved to get that front end working for me.
Yes, as stated maybe I need to see what else I can do instead of spring rate as 9N is what I would have bought for springs. yes removing the compression just made it worse.
Im struggling. but I do want to thank both you guys. This has been informative. Sorry to thread jack. Twentysixred posted some info that will help out the OP with setup.
Hmmm. First thing in your case is to check what the correct spring rate is for your full-gear weight. If the springs are close enough, THEN you move on to valving...
is correct, and the high speed damping is the problem here, then you're not going to solve your handling problems by changing springs, or adjusting Low Speed Comp. I don't have a lot of time to write a really good 'teaching' post on this, so forgive me if I don't make much sense...
There's many ways to cheaply achieve a handling characteristic for a stock bike. If the '15-'16 R1 is really track focused, and Yamaha are addressing high speed stability through a hardcore high speed compression approach, there's several ways they can do this:
1. Piston design. Port size + the number of ports + port shape all have an effect on oil flow. Oil flow is your damping. Maximum oil flow potential is your maximum damping ability. Hell you can actually control the maximum amount of compression/rebound JUST BY port size and shape! It's a cheap shitty way but a lot of manufacturers do it as it's simple, easy, and you really don't have to put anywhere near as much engineering time into shim stack configuration compromises.
2. Shim Stack design aka valving. Shims are basically really thin, springy flat washers that flex when oil pressure from the Comp/Ten ports hit them. Sitting over the exit of the Comp/Ten ports on either side of the piston is a stack of shims. Depending on the speed and force of the oil pressure, depends how much they flex. The shims seal the ports by default, and when the piston is on the Comp stroke in a fork/shock, the oil pressure is pressing against the Reb/Ten shims, sealing them over the Rebound ports, at the same time that it is flowing into the Comp port intakes. The Comp port intakes are on the edge of the piston, outside of the OD (outer diameter) of the Rebound shims, allowing oil to flow into the Comp ports, at which, the ports route the oil inwards, to the inner diameter of the Piston to force the oil against the Comp shims, pushing them open, breaking the seal the Comp shims are making on the other side of the piston face. During the Rebound stroke, the oil pushes on the Comp shim stack, flows into the Rebound ports, which is then directed inwards to force the Rebound shim stack open. Tuning your shim stack is actually not too hard when you know how they work. (Shim stack tuning is also called 'revalving')
right. So, if you're an engineer, you can control maximum compression through 2 basic ways: Maximum flow of the piston port, OR, maximum flow of the shim stack. Thing is, shims 'wear out' over time. After a while, shims don't seal cleanly on the piston face either. This is caused by 2 things:
1. Piston face wear - the shims 'slap' and 'flutter' on the piston face, beating tiny grooves into it.
2. Shim 'wear'. You bend metal enough times, with enough heat and repeated pressure, and the metal doesn't bend back perfectly after a while.
The shims slapping the shit out of the pistons and deforming their faces, and the shims also not bending back to perfectly flat, results in a degradation of damping over time. Because the oil leaks past the shim/piston seal, and more force is required to flex the shim stack and give you the desired damping curve.
So, what do you do?
- Replace shims and valves on a regular basis (MotoGP, WSBK) because 1/100th of a second actually does mean win or lose;
- Design the piston so the Comp & Rebound ports only ever flow a maximum value of x.
Now you see why Yamaha might have a really good reason to create the pistons in their latest R1 with small oil ports. It's a very simple way to ensure that the compression a fork gives will always have a maximum value close to the desired handling characteristic you've decided that chassis should have. It would also primarily affect the high speed compression circuit, which is typically where a track bike has the most restriction. Controlling High Speed comp through a shim stack on a bike designed for pure track is the best option for a race team, but not for an OEM. Controlling high speed comp through port design on a track bike, for an OEM, would be the best option - the shim stack can go to hell, it can be bent and warped and the piston can be slapped to shit, it doesn't matter too much because you'll get on the track and the maximum port flow takes care of it.
Point? If you've got the correct springs or close enough, and you've wound out the Comp as soft as you can and you still hate the high speed comp characteristics, then the option you must look at is:
- Revalve with a different shim stack + piston.
There's several places out there you can go to for a new valve stack, and they all do different approaches to get the same result. Ohlins will do the job, but I don't like the port sizes on their off-the-shelf valving kits. The NIX carts are great, but many riders take a while to adjust to the very different damping characteristics. Racetech have a kit, but, their solution is not elegant. It's like doing surgery with a hammer. There might be surgeons out there who are ****ing wizards with a hammer, but it's still a damn hammer and it's a really blunt and crude way. Penske IMO are great, but their off-the-shelf kits are not great; you need a very clued up suspension engineer who has asked you a lot of questions, to pick the right bits from their catalogue and build a valve stack. K Tech have a great marketing team and they've got a lot of data around Irish Road Racing & Isle of Man TT, but their standard stuff is a one-size-fits-all approach. They're better than Racetech but not as good as Ohlins fundamentally (wish I had more time, it's much more complicated than that - Ohlins fundamentals are much better, Ohlins solve some problems K Tech have not yet, but K Tech work around that by compensating in other areas creating their own unique problems)
GP Suspension made really, really good solutions when Dave Hodges ran the show, he understood road applications and could make something that actually directly solved *YOUR* needs. I'm not sure if Dave is still going @ GP, and how effectively he has passed on the baton. If he is still there and still designing things, give him your money. He can ship a valve stack out, or you can send him your forks / fork internals and he can ship them back. Jamie Daugherty @ Daugherty Motorsports is my preference if I really want the best solution, and don't want to spend too much, he will build you something that actually addresses your exact needs and he won't cost crazy amounts.
Andreani is way outside of anyone's price range except race teams, but if you had a spare 20K to spend on the best stuff that's where you'd spend it.
Back to you and your problem - you need a revalve. A proper revalve with a new piston and a stack that's designed to match the springs and your riding needs. Off the shelf Ohlins/Penske/Racetech/K Tech might get you closer, but for the same money or less you can get GP Suspension or Daugherty Motorsports and a much better solution.