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[Crissa]

A 17" steel mag wheel is 40 lbs.

Groms are performance - they aren't cheap.  They're not fast, either, but that doesn't mean they cheap.

-Crissa

[caza]

how you really gonna say the literal cheapest motorcycle in honda's lineup isn't cheap?

What bike is that 17" steel mag wheel from? How much does the bike weigh, ready to ride? We need a  real example of an OEM wheel on an OEM bike weight to make any kind of comparison. Giving a random wheel example without the context of the bike doesn't tell us anything about its ratio of unsprung vs sprung. Heavier bikes tend to need heavier components, including heavier wheels, rotors, brake calipers, sprockets, chains, etc.

An 800lb Goldwing for instance, has a 35lb wheel. 

The effect unsprung weight has on handling is directly related to that ratio.

This video has a good explanation and simulation of the very real effect this has on suspension



Of course another important question to ask is how well the rear suspension on the sondors performs, and if it's even adjustable.

[Crissa]

how you really gonna say the literal cheapest motorcycle in honda's lineup isn't cheap?

How do you think that a motorcycle built as a plaything for the world's rich isn't the cheapest Honda?  What's the price of a Honda Shine?

Nice.  First you ignore most of the sprung weight in your comparison.  Then you forget the gear and chain weight.

C'mon.  It's certainly going to make it perform slightly different.  But it's not a massive change from cheap bikes of the past.  (You admit that a goldwing has a heavy wheel!  Geez.  What about the weight of the drive shaft, too?)

You might as well make a big deal about the change in rotational force from an engine.  "Oh no, they did that, too!"

-Crissa

[princec]

Er Crissa, you seem to be wilfully ignoring the ratio of the sprung to unsprung weight that is being highlighted here. A 40lb wheel is fine on an 800lb motorcycle (whether an 800lb motorcycle is fine on the other hand...)

Seriously - heavy wheels make awful handling, and I really mean awful. I don't know if you're old enough or not to remember what bikes used to handle like only 40 years ago but let me assure you, they were shit. I am amazed any of us survived. All of the little clever advances made over the last 40 years today give us bikes are are all fundamentally great handling. One of the big advances (of many) was the understanding that heavy wheels means terrible roadholding.

Cas

[Crissa]

Yeah, and I know that people are making a mountain out of a molehill.  It's only one wheel, it's just the drive wheel, and editing the comparative weight to the extremis - ignoring rider, sprocket, etc - is exaggerating the difference and ignoring precedence.

It's one of the reasons I talked my spouse into a new bike over the classic Hondas she was used to - bikes are lighter today and wear better.  All the hundred of tiny things.

But they're still tiny things.  The metacycle is never going to be a grom.  No one in their right mind commutes on a grom.  It's also not the cheapest bike Honda makes.

-Crissa

[Fran K]

Who is ignoring the rider.  Sure no one has discussed the rider standing on the pegs and sort of have a spring and shock between them (the massive upper body) and the pegs.  I should have mentioned the weight of a rear sprocket and half the weight of the chain suitable for this horsepower class, as well a half the weight of the swingarm assembly.  Don't loose sight that the motor weight is moved from the sprung to unsprung category.

If I recall the 80's two stroke 500cc and smaller bikes the whole rear wheel with the brake drum weighed 24 pouns.  There is a backing plate shoes and chain.  A drive shaft bike the wheel can be lighter but there is more stuff.  Now from what  I understand the design is mass centralization, some think the shocks with linkage help with placement on the bike as much as wheel control.  Which is another discussion.

Not sure how this applies here but in suspention there is a term called packing.  If the bumps come at a faster rate than the wheel can go down the suspention starts riding higher up in the stroke where the damping is different.

[Richard230]

Yeah, and I know that people are making a mountain out of a molehill.  It's only one wheel, it's just the drive wheel, and editing the comparative weight to the extremis - ignoring rider, sprocket, etc - is exaggerating the difference and ignoring precedence.

It's one of the reasons I talked my spouse into a new bike over the classic Hondas she was used to - bikes are lighter today and wear better.  All the hundred of tiny things.

But they're still tiny things.  The metacycle is never going to be a grom.  No one in their right mind commutes on a grom.  It's also not the cheapest bike Honda makes.

-Crissa

There is nothing cheap about the Groms that I have seen. They appear to be just a starting point for expensive modifications that include such things as big bore engines, wide wheels, extended swing-arms, nitrous injection and other crazy things that don't make any sense on that little motorcycle. 

[caza]

Yeah, and I know that people are making a mountain out of a molehill.  It's only one wheel, it's just the drive wheel, and editing the comparative weight to the extremis - ignoring rider, sprocket, etc - is exaggerating the difference and ignoring precedence.

It's one of the reasons I talked my spouse into a new bike over the classic Hondas she was used to - bikes are lighter today and wear better.  All the hundred of tiny things.

But they're still tiny things.  The metacycle is never going to be a grom.  No one in their right mind commutes on a grom.  It's also not the cheapest bike Honda makes.

-Crissa

Mountain out of a molehille? I literally said it will no doubt effect handling, it's 50lb! But also said it won't be a big deal for the average use case. Who's making a mountain? I think you're losing the nuance here.

Add all the other stuff in, it's still a big difference! 50lb is a lot of weight for a 200lb bike no matter how you look at it. Again, if you wanna pick a bike you have solid #'s for we can do a comparison, but the ratio of unsprung weight on the metacycle is pretty extreme compared to a gas bike or even any of the electric bikes we're used to.

I didn't add everything to my comparison not to "ignore" them, but because I simply don't have solid numbers in front of me for them. I was keeping the example simple because 50lb speaks for itself. A sprocket and chain doesn't make a dent in how big that difference is, and is effectively irrelevant unless we're going to do really precise calculations. I didn't see a point in doing anything precisely because again, 50lb on a 200lb bike is  a huge ratio by itself!

You talk about precedence, but show me another motorcycle that weights only 200lb with over 50 of it being in the rear wheel.

But sure, if you wanna ignore known physics about how unsprung weight effects suspension because of the negligible weight of a chain and sprocket, be my guest. 

The ratio is what's important. Are you suggesting that because the goldwing is fine with a 35lb wheel + ??lb drive shaft, you could transfer that heavy rear end to a smaller bike and it would handle just fine?

I dunno about if they're in their right mind, but I used to see a couple commute 2-up on a grom across the bay bridge every day. Looked a bit too dangerous for my taste. But I also see people commute around with them in my area.

And it is the cheapest motorcycle they sell, at least in the US. The only cheaper 2-wheelers they have are the 49cc scooters, as in, not motorcycles.

[Crissa]

Hey, caza, I missed that you already said that last week:  https://www.electricmotorcycleforum.com/boards/index.php?topic=10775.msg99954#msg99954

That storm took out power and internet for a tenth of my county including me so I missed a few things when trying to catch up.

And no, I'm not saying that the shaft drive wouldn't be heavy and less responsive (tho it's really nice in other ways, honestly) just that a few pounds this way and that are not significant and it's annoying to have ridden bikes much, much worse and hear people continue to harp on this as if it were impossibly unsafe.

-Crissa

[caza]

I definitely agree with you there, I think there's a middle ground where we can acknowledge the handling effects of unsprung weight without acting like every bike with a hub motor is going to be a huge safety concern and should never be ridden.

Inverted forks add unsprung weight, but we still do it because there are more factors at play, and fork stiffness is worth the hit in that case.

[princec]

Just musing but... would a grrt big heavy hub motor, attached to a particularly light motorcycle out the front, not make for an especially entertaining wheelie device?

Cas

[caza]

It could but it would ideally need to be the right hub motor tuned for higher torque instead of higher top speed. Since you can't play with your gear ratio the motor has to be made for the use case you want.

[JaimeC]

Inverted forks add unsprung weight, but we still do it because there are more factors at play, and fork stiffness is worth the hit in that case.

Not sure how you came up with that, as I see the opposite.  By putting the thicker, heavier part of the fork ABOVE the spring you are reducing unsprung weight.  Now it is the thinner, inner tube that is sprung.  It also increases stiffness as you said as your turning torque goes directly into the wider diameter tubes which would flex less than the thinner diameter tubes used on older motorcycles.

[princec]

I think the sprung part of an inverted fork is traditionally solid alloy/steel rather than a tube hence slightly greater mass than you'd expect.
This is only half the story though. The very worst sort of unsprung weight is unsprung weight that rotates at 300rpm.

Cas

[JaimeC]

I think the sprung part of an inverted fork is traditionally solid alloy/steel rather than a tube hence slightly greater mass than you'd expect.
This is only half the story though. The very worst sort of unsprung weight is unsprung weight that rotates at 300rpm.

Cas

That doesn't make sense.  I'm not saying it's not true (I need to do some research) but it doesn't make any sense.  From purely a materials perspective, I hollow tube would cost less than a solid rod.  Gotta hunt around for photos of an exploded, cartridge-style USD fork to verify.