Oil and Shifting "Feel"

[TucsonDon]

Many people here speak of the "feel" of shifting and use that as a measure of how well a bike "likes" a particular oil. I use that measure as well. But, truth be told, I have no idea why one oil would produce better shifting and another not.

So, that's my question -- what quality of an oil would produce "better shifting?" Is it strictly a function of the weight of the oil? Or is it a function of viscosity? Additives?

Second question -- from a purely mechanical point of view -- what is happening when a motorcycle transmission's shift "feels wrong?" Does the oil film break down and some metal-to-metal contact takes place? Or is it some different way the gears move around that causes the clunks and the notchy sounds? Why does one oil cause this and others not?

 

[Lorenzo]

I'm convinced that in most cases when someone reports how much better their new oil feels, they are simply experiencing the effect of replacing old worn out stuff with fresh. Same thing for tires, brake pads, etc.

 

[TucsonDon]

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I'm convinced that in most cases when someone reports how much better their new oil feels, they are simply experiencing the effect of replacing old worn out stuff with fresh. Same thing for tires, brake pads, etc.

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My guess is the most significant aspect of "worn out oil" is sheared viscosity. If I'm right about that, then what it seems you're suggesting is that "shifting feel" is related to an oil's ability to stay within grade.

But what about new oil X vs. new oil Y. Presumably they'd both still be in grade. Since "shifting feel" is a subjective thing, would differences reported there be more imaginary?

 

[Titan]

It's related to viscosity. I can tell when an oil has thinned by the way it shifts, and that's when I change it. I don't even bother getting a UOA any more...if it begins to have any issues shifting, I change it. Issues go away.

 

[TucsonDon]

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It's related to viscosity. I can tell when an oil has thinned by the way it shifts, and that's when I change it. I don't even bother getting a UOA any more...if it begins to have any issues shifting, I change it. Issues go away.

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Mechanically, what about the viscosity affects the shift capabilities of the transmission? Is it that oil in grade provides a kind of "hydraulic cushion" for shifting?

Honda calls for a 10W-30 in the Goldwing now. I use a 40 weight and the tranny is somewhat notchy ... I can't imagine what a 30 weight would sound/feel like.

 

[KernelK]

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It's related to viscosity. I can tell when an oil has thinned by the way it shifts, and that's when I change it. I don't even bother getting a UOA any more...if it begins to have any issues shifting, I change it. Issues go away.

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Are you saying that you only have shifting issues after you have traveled 8-10 miles and have warmed the oil to operating temperature and that you can feel the 2-3 centistoke difference @ 200 degrees that the oil has sheared?

 

[SLM]

I have noticed no difference in my bike-save for a little less noise on shifting into first after starting it up for the first time.

 

[Titan]

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It's related to viscosity. I can tell when an oil has thinned by the way it shifts, and that's when I change it. I don't even bother getting a UOA any more...if it begins to have any issues shifting, I change it. Issues go away.

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Are you saying that you only have shifting issues after you have traveled 8-10 miles and have warmed the oil to operating temperature and that you can feel the 2-3 centistoke difference @ 200 degrees that the oil has sheared?

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What I feel is a "double-click", or "clickity", instead of a single snap into gear. When I change the oil, the clickity goes back to snap. When I've tested the oils that go clickity, they are less viscous than the ones that I've tested before the clickity arrives. Am I feeling a couple of centistoke difference? Not directly. Does the clickity indicate a thinner lubricant, or something else? I'm guessing it is viscosity change.

 

[BillWilson]

On my wife's 2007 Yamaha Virago 250, it was hard to find neutral while sitting, cold or hot until Rotella T 15W40 was installed. Now it is easy to find neutral cold or hot. Yamalube 20W40 was the oil being used before the Rotella T. When Yamalube was used during the first 600 mile service, it was still hard to find neutral. When Rotella T was used at 4000 miles, we saw a positive difference during the first 25 miles that continues after several hundred miles. It has been discussed on the Virago 250 forum about neutral being hard to find with this model. I can only give the results between two different oils. My wife is interested in "results" of better shifting no matter what oil is used.

 

[mrsilv04]

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Honda calls for a 10W-30 in the Goldwing now. I use a 40 weight and the tranny is somewhat notchy ... I can't imagine what a 30 weight would sound/feel like.

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Try the Amsoil MCF 10w-40. Unless I find something better, I'll never use anything else. The shifting on my '02 GL1800 freed up right away, and it shifts nicely well past the 5,000 mile mark. Never got that out of any other oil.

 

[TucsonDon]

My original questions remains unanswered -- Why would one oil make shifting better? What is the mechanical property of one oil versus another that makes the transmission shift better? What mechanical elements of transmission work better and why based on the oil that's used?

 

[wileyE]

Good question Don. Since most the transmission in question are constant mesh, the only thing to "feel" would be the shift dogs and forks interface, also the clutch drag at the plates and it's effect on shifting. If it was purely viscosity there would be huge difference in perceived shift feel from cold morning to end of day (which isn't really that noticable) This difference would be much greater than the small effect of the oil shearing down a grade IMO. If it is additive level one would note a difference between a api sm oil and a hdeo? my trials don't prove this is the case either. The one thing that I have noticed, and it flys in the face of jaso-MA, is that oils with lower friction coefficient's shift better and make the clutch drag less. after ~1500 miles, these oils show some improvement in shift feel when changed out too, so the question still remains.

 

[XS650]

Don, the fork end of shift forks commonly run steel on steel in the grooves machined on the gears. The single end of the fork runs steel on steel in the shifter drum.

It feels like there is something besides just viscosity at play there.

I haven't been riding for about 5 years now, but when I was a good HDEO 15W-40 outasted (by shift feel) the boutiquey 10W-40 MC dino oil with a picture of a motorcycle on the can.

It was most noticeable when the engine got hot in traffic on a hot day.

 

[Trondos]

A thought crossed my mind. Todays CNC-controlled lathes and milling centres accelerate their carriages very fast, and a phenomenon called stick-slip has become more known.

Common slideway oils list as one of their features that they prevent stick-slip.

The more I think of it.....the shifting forks etc inside a motocycle gearbox may likely suffer from the same phenomenon?
And it`s likely that different MC oils offer slightly different properties regarding stick-slip?
I`m only speculating though.

 

[wileyE]

Sounds like good speculation to me? When Harley prototyped their counterbalanced motor they had trouble with the shifting which left them scratching their heads. What they hadn't considered was VIBRATION was a key player with the old motors being able to shift well (relatively speaking). The vibration helped prevent the stick-slip like mentioned. Harley went right into a modern gearbox from another manufacturer to learn how to machine the parts to cure the problem.

 

[Mackelroy]

Back in the early 90's I had a CR125 the I mainly rode on rock, with 10w40 you could hear the transmission gears banging against each other. I put straight 40 weight in it and [censored] what a noise difference, very quiet.

IMO between the best and worse shifting oil theres' only a 5% difference, but it can be a gate, no gate transition.

either ya like it or ya dont, thicker oil generally slides better when it has a load on it.

 

[tom slick]

Originally Posted By: Lorenzo
I'm convinced that in most cases when someone reports how much better their new oil feels, they are simply experiencing the effect of replacing old worn out stuff with fresh. Same thing for tires, brake pads, etc.


my bike's shifting gets "notchy" within 50 miles of off road riding. keep in mind that is varied high rpm and constant shifting. it must be something with the way the shift drum and forks interact.


I don't know if it is stick-slip. ways on a cnc machine are much closer tolerance and finer surface finish than anything in a MC engine.

 

[hi-miler]

Originally Posted By: TucsonDon
My original questions remains unanswered -- Why would one oil make shifting better? What is the mechanical property of one oil versus another that makes the transmission shift better? What mechanical elements of transmission work better and why based on the oil that's used?


I'm with you on not understanding this one. Regular dino oil 10w-40 (whether MC only or Automotive), and Mobil Gold Cap 15w-50 left me with hard first gear shifts when I initially started my Rebel 250. Amsoil 20w-50 made a huge difference. Smooth shifts right from the start. All gears are easy to shift into, and neutral is no longer a problem.
My guess is it's in the add pack.
Steve

 

[bmwtechguy]

add pack and viscosity retention. Is the Amsoil the MCV stuff or reg 20W-50?

 

[Gary in Sandy Eggo]

Originally Posted By: tom slick

my bike's shifting gets "notchy" within 50 miles of off road riding.

That notchy feel is evidence that your oil has "sheared" out of grade at operating temperatures. Run that bike on automobile SAE-40 or SAE-50, and I guarantee you your shifting will not degrade for several thousand miles.