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GHILL28

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About GHILL28

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    California
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    MX/trails, mountain biking, ice hockey, SCUBA, mechanical engineering.

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  1. GHILL28

    Purpose of rear suspension linkage

    Anyone have good linkage data from the modern 4 strokes? Curious about a few of them.
  2. 450f swingarm and linkage shock on an 06 aluminum frame.
  3. I have a Yamalink dog bone for the 09+ swingarm if you want to lower it. 146mm, black.
  4. Yamaha suggests different maps for different terrain (and consequently different drivetrain loading conditions) because AF ratio changes with respect to that. Anyone used to interpreting dyno data and O2 sensor data knows this. A dyno run is not a full characterization of an engine, but rather a control point. Got the bike on the stand with your rear wheel in the air and run it through the gears? You get one curve for AF ratio vs RPM. Got the bike axle deep in a sandy corner exit and run it through the gears short-shifting? You get an entirely different curve for AF ratio. Now do the same two scenarios with partial throttle openings vs. full throttle openings and guess what - different curves.
  5. You can get similar valving in there with a couple small adjustments for a 2-stroke. The fork will be the easy part since they're the same guts. Copy/paste the valving and maybe drop a springrate for the 2-stroke. Some different offset clamps will help the 2-stroke a bit too. The shock is a different size though. Believe your 250 has a 46mm body and the 16 450F has a 50mm body. They may have different rod diameters too. The compression adjusters are the same in the shock. The rebound bleed geometry has been changed quite a bit from the YZ250 shock to the newer shock. I believe the linkage rate is also different. The newer linkage (more progressive - not necessarily a good thing) can be swapped onto the YZ250 with a newer swingarm and newer hub. Depends how much money you want to spend....
  6. SKF oil seals are lower friction than NOK. The dust wipers are much higher however. If you want a lower friction dust wiper, pop the wiper down and give a spray of Dupot Teflon Silicone lubricant once every few rides when cleaning the bike. Costs $5 and will outlast the goofy coating.
  7. The bushings DO wear really fast, but not in an area that supports that argument. The PTFE glide surface isn't what wears out, except in cases of extreme neglect, it's the bit of liner on the other side that is either riding in the slot of the slider, or is pressed in to the upper, and they wear out from rocking. The discussion was about friction coefficient of surface treatments other than OEM. Your contention is that under oil, the results should be the same as in a dry situation, because there are instances where the oil can't provide the lubrication necessary?
  8. Nobody here has argued that the effort of reducing friction is a negative. Only that it generally doesn't turn out that way when people try to achieve it. Arguing that reducing friction is a negative is more of a system level and dynamics issue (and there IS an argument for it), irrespective of whether the coatings are doing what is advertised.
  9. Show me test data that proves: 1) Your coating of choice on top of hard chrome vs a PTFE lined bushing submerged in oil has a measurable and statistically significant difference. The coating must not provide a dimensional change significant to the bushing gap which is typically around .003" on a proper build. 2um is ~.0001". 2) Your coating of choice on a surface that has had hard anodize chemically stripped (aggressive as hell and roughs up the surface of the substrate since anodize impregnates the first few .001" of aluminum) and replaced with the coating vs a PTFE lined bushing submerged in oil has a measurable and statistically significant difference. I'm going to spoil it for you - neither of these situations are improved with the addition of PTFE or MoS2. Once the bushings and seals are under oil, and dimensionally correct in the diameters and cylindricity, surface finish (roughness) is the game to play. Not coatings. That's not ignoring basic physics and engineering - that IS the basics. The best thing a coating can do is increase the hardness and the durability for someone who is putting a LOT of hours and heavy strike loads into the sliding surfaces.
  10. Mtb community is equally as full of hype and non-engineering. Arguably worse. The friction case for a mtb fork is a whole lot different too. Lack of lubrication in most cases of modern forks, and an ever-changing sprung mass relative to springrates.
  11. GHILL28

    DS Sphere updates

    That's good. Having flashbacks of the Ohlins cartridges that would bend rods every 50h or so. Sometimes less.
  12. GHILL28

    DS Sphere updates

    Wait, so these $1600 cartridges also were having durability/failure issues? Is this a joke?
  13. Most coatings offer no perceivable benefit in hysteresis under oil or durability over really good stock stuff. If you feel a noticeable difference, 90% of the time it's from the added thickness reducing the heel-toe striking when the tubes bend from a tall square edge. You'd probably feel the exact same thing by shimming your bushings by the same amount as the coating thickness.
  14. GHILL28

    How much is Savatgy's cut?

    24 motos for outdoors Minimum 34 motos for Supercross if you have a heat and a main. Maybe more if he had to do a semi here and there. 3 at MEC. A couple at MXDN. Didn't watch that and I don't know the format. Straight Rhythm if he shows up to that, not sure if/how that counts. So, I'd say that any full time American racer does race about the same, or maybe more. Not drastically different either way.
  15. GHILL28

    All New 2019 Yamaha WR450F Announced

    I'm not sure I'd call a redundant start button a solution for a 100% dead battery...
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