Real world hwy P&G mpg for 250-650cc cycles?

[alvaro84]

Originally Posted by stillsearching

Well that's part of why i'm asking - even if P&G sucks is it still worth doing?

Well, it depends. When I didn't use coasting, it was rare to reach 3l/100km. When I started to do so, it became something basic, 'good' is well under that. Now 'good' is under 2.8l/100km. Very good is like 2.6-2.7. PR is 2.38 (I may not reach it again). But I need long trips and hills or mountains for the for 'very good' tanks, so I can't compare them directly.

Of course only a part of my coasting is P&G, but there are circumstances where P&G is a natural way to follow the terrain or the traffic, so I P&G there even when I don't do otherwise.

And I almost always P&G if I can't shift into at least 4th (topmost minus one).

And the main problem is that my bike doesn't have any kind of FCD.

Plus side of flat road P&G:
- A few percent FE gain over the bottom of highest gear. Sometimes more. Surely depends on the way you do.
- Presumably even more gain when in a lower gear (some FCD would help!).
- Keeps you awake after night shifts (no joking here ).
- The ability to choose which hand you want to rest (can really help when you ride all day long)
- Stronger grip in the long run

Minus side:
- Tiresome and takes a bit of your attention.
- Wears dropout bearing (though I really don't know how much - Teresa's lasted for ~111000km).
- Surely wears rear tire more than constant low speed riding.

[stillsearching]

Why would the rear tire and dropout bearing wear more, are the loads from extra bursts of acceleration that substantial? What's an FCD? (fuel use instrumentation?)

I'm willing to put in an ignition cut off and play around with streamlining the bike, within what my limited fabrication skills are capable of creating. Since it sounds like bikes are even worse than I thought aero-wise, even lower quality aero is probably a huge improvement. My goal would be 100mpg with a larger bike if I can reach it since that's when it starts to pay for itself, even with summer only commuting, in a fairly short period of time. I'd want to make the fairings easily removable so I don't have to always ride that way. (for instance if i got say some 400cc dual sport I could have it on to putter the highways yet remove it to actually go camping since the aero stuff might get in the way... of the riding experience if not other things) Really wish I had SFC figures so I could know what RPM range it would want to run in through, rather not change that if I can help it.

[alvaro84]

Originally Posted by stillsearching

Why would the rear tire and dropout bearing wear more, are the loads from extra bursts of acceleration that substantial?

The bearing is worn by the very act of holding the clutch. The rear tire - hm, it would be nice to do some math about it. Until someone competent does it, please don't take it as a fact, it's more like a theory of mine. But applying force to the road (accelerating or braking) wears the tire more than just rolling, and I suspect that wear is not linearly proportional with the applied force (like aero drag is calculated from the square of speed and road damage is proportional with the 4th power of weight per axle). So acceleration/glide cycles probably won't give the same average as the less force needed for keeping the same unchanged speed. Sorry, I don't know the necessary background

[stillsearching]

My guess would be the bearing shouldn't wear much more than you'd get in city traffic then since one is constantly pawing the clutch, and the tire should spend little enough time under extra power (just gliding) that the life difference should be negligible i'd think.

[alvaro84]

I hope so

It's still interesting how these Heidenau K73 rears wear now: it's a commonplace that a front tire serves twice the time a rear - but with these I've worn 3 rears for a single front. It's true, though, that my Metzeler Z6s wore at once, the front didn't last any longer than the rear.

You may be right about city traffic, that needs much more shifting than the way I'd use the bike if I didn't glide: most of my commute is out of the city and I only have to get out of 5th in the 2 villages before I reach the edge of the city.

And I try to avoid bigger cities/towns during touring too.

[sendler]

PnG works the same for a motorcycle as it does for a car. Just at a higher frequency because the bike weighs so much less. So there is little time between cycles to bother to shut the engine off with a bike. Only during down hills. Which may not be ideal for reasons of wear as there are some oil pressure lubed bearings in motorcycle trans. But they are roller bearings so they should survive unharmed on a residual oil film for quite a while. I only shut the engine off at stop lights and during competition.

[MPG_Plus]

My 4 week average is 108 MPG after changing to 16/33 sprockets and a non-oring chain. Typically may ride to work is mixed city driving with a 7 miles at 55 . Coming up to lights and down hills I P&G and the new non-oring chain glides at least twice as far. I have calculated top speed at about 93 MPH in 3rd gear but haven't tried it yet. My point being is that I have no problem keeping up with traffic you just have to pick the right gear. In slow traffic I am typically in sixth gear at 33 MPH. If I were to start again I would probably go with the new ninja 300 but it isn't exactly cheap. If I ever get into serious aero mods I would gear the 250 higher yet.

[renault_megane_dci]

Please, start a fuel log.

[MPG_Plus]

I have my own spreadsheet and do not use this site very often. I see several "fuel logs" that have the same look. Where do I find this fuel log?

[renault_megane_dci]

click garage in garage&tools, add a vehicle, make a fuel log entry (catch up with your older fuel log since there is nothing on TV anyway ;-) )