Anybody see a measurable change in fuel mileage with larger diameter rear tire?

[safecracker]

I never noticed any difference in my riding.

 

[Knizar]

"Nope!"

 

[BobAnth1]

Here are the weights removed from the rear wheel of my second 2018 when the Kenda was removed. A General Altimax Rt45 was installed without balancing and has no issues. I have done 4 rear tire R&R now between my Spyders and friend's Spyders. Not the funnest job, however having the right tools including a BIG torque wrench helps.

My newest 2018 with only 4100 miles on it will get Vredesteins and a General when I get back to Washington in May and see it for the first time. My son up there handled the viewing, receiving, paper work, and storing of this one. I am debating on whether to put on 175/55R15 on slightly wider PPA Orb wheels or 165/60R15 on the OEM wheels.

View attachment 253900

These took the place of the Kenda front tire with no noticeable difference in height or width and a hell of a better tire.. Chinese tires are not known for their specs to be that true. I run 20lb. air.

 

[mecsw500]

Like Peter says the whole subject of grip depends on a large amount of real world factors. In fact it only depends upon real world factors.

From a purely theoretical perspective limiting friction very surprisingly does not depend upon contact patch size at all. It’s all those other real world factors that count because the tire is rubber and hence deformable and the road surface is not totally smooth, coupled with the environment.

It’s all down to what combination of those real world factors you find suits you personally best of all in combination with economic issues.

For instance Peter and Baja Ron are seemingly not terribly keen on the XPS branded Kendas even, if I read them right. I, on the other hand, quite like my particular samples on my ‘26 S2S. I understand both of their reasoning and in due course I may follow their experiences and fit something different as the miles rack up. But for now, for me, with my sample set size of one, I’m not unhappy with them.

I suspect we all have to compromise as to what we would like best due to the very limited tire options available in our fitment sizes. I suspect over time that limited set of options may decline even further as the cars that fitted R15 wheels age out and the major manufacturers leave it to the economy brands to service that market due to the economics of scale. Many R15 tire size options in general have faded away over recent years and I suspect sales to Spyder riders isn’t a sufficient sales volume in itself to keep our tire sizes available in perpetuity.

 

[BajaRon]

Though I am definitely not a fan of the original and subsequent OEM Kendas. I have not had enough experience with the new XPS Kendas to have a reliable opinion. I am currently running a set of Kanines, which I am liking. We have seen a tendency for less miles than the car tires we carry, and the rear does tend to wear in the middle, though not as badly as the OEM Kendas.

For traction, handling, and ride, the Kanines seem to be a worthy tire, depending on your preferences. It is the least expensive tire we carry. And it does come in OEM sizes.

 

[Jb74texan]

I've actually tested a lot of these different tire sizes, properly, on a track, over accurately measured distances with scientific and recently calibrated instruments, and really, any difference you might find with any lesser testing is likely going to be pretty small if not completely inconsequentially tiny AND potentially misleading; unless you REALLY get down into the minutiae/nitty gritty of it all, and absofreakinlutely start matching the tiniest bits of the vast range of potential variables before doing the comparison, like having your tires before & after set to exact fractions of air pressure at a specific ambient temperatures running on a specific road surface that's a defined temperature at exactly the same time of day, cloud cover, sun inclination, et al)... And if you don't do this, then you'll likely either get some fairly useless data &/or just rapidly confuse/upset yourself and everybody around you, and you'll still probably only get results that aren't really valid enough to have any significant impact beyond your personal 'for interests' sake, but are also very likely going to different if not the opposite of what you might expect, and besides, because of the limitations in how you can measure/rationalise and include allowances for all the potential variables in your calcs, nothing's really 'exactly the same' &/or even 'correct' per se, let alone 'accurate' anyway...

Consider this - a taller tire that turns fewer revs per mile should theoretically give you better fuel economy, shouldn't it - travelling a further distance each rev? Yeah, but how did you measure how far you travelled in total &/or how much fuel you truly used?? If you used the speedo/odometer/trip meter on the Spyder to measure your speed &/or distance travelled, then because of the larger dia tire travelling further with each revolution than what it was doing with the OEM tire, the distance shown on your odo/trip meter will also have been changed too, so you can't compare it to your before calcs - it'll be reporting shorter total distance travelled over the same number of revs, cos unless you've reset them, your Spyder's computers still think you're doing 'x revs per mile', only you're actually now doing 'x minus some' revs per mile. And even if you think you've run over a given measured distance at exactly the same indicated speed on your speedo &/or GPS, there's discrepancies built in there too (even your GPS isn't really exactly accurate, altho it's likely better than your odo/trip meter, but then there's also variables based upon how many satellites it's acquired and how high/far away they are etc...) And then there's the pressure you're running in the (new, old, whichever) tires - that will vary its effective rolling diameter too, so there's more variance; and the new tire's 'revs per mile' is going to be different to whatever that was with the OEM tire, even more so if the barometric pressure is different today to whatever it was last week; so effectively, it all boils down to whatever you might think gain/lose in the way of fuel economy on the teeter totter, you'll likely lose/gain that or more on the see saw, &/or vice versa... And really, there's only ever gonna be 2/5th's of 5/8th's of a bee's whisker in it anyway - IF you can rationalise &/or cater for all the potential variables!!

Yep, that truly is a 'big IF'!

This! There was a FB post last year that helped explain belt diameter and rollout. Good stuff, great stuff Peter!

Banana for Scale | It amazes me the number of people who misunderstand the behavior of a tire | Facebook

It amazes me the number of people who misunderstand the behavior of a tire. I noticed in a recent post that there were a significant number of people who believe wheel size to be a factor. Others...

www.facebook.com

 

[Snoking1127]

These took the place of the Kenda front tire with no noticeable difference in height or width and a hell of a better tire.. Chinese tires are not known for their specs to be that true. I run 20lb. air.

View attachment 255923

Those tires look very narrow for the rims they are mounted on.

Though I am definitely not a fan of the original and subsequent OEM Kendas. I have not had enough experience with the new XPS Kendas to have a reliable opinion. I am currently running a set of Kanines, which I am liking. We have seen a tendency for less miles than the car tires we carry, and the rear does tend to wear in the middle, though not as badly as the OEM Kendas.

For traction, handling, and ride, the Kanines seem to be a worthy tire, depending on your preferences. It is the least expensive tire we carry. And it does come in OEM sizes.

If the Kanines are working for you, I think possibly the XPS branded Kendas will be a subsequent improvement again.

For me, they seem to have a slightly different compound because I find they are not as greasy at the front when the ambient temperature gets above 100°F on black tarmac. I think they are better in the wet too, which might be down to the tread depth or the tread pattern of course. I find the very slightly stiffer construction on the fronts better matches the spring rate and damping on the front. Mine also have a very small set of balance weights which I think means their construction quality is better. I've settled on 20/30 psi for two up with luggage.

Of course, I've not yet done enough miles to see how the longevity holds up, especially on the rear. Will it wear the center out no matter what pressures you run? Very possibly. It's harder to feel what the rear is doing compared to the fronts too.

Having said all that, I have a sample set of one. You probably end up with a sample set of hundreds over time, so your findings will be much more relevant than my personal experience.

PS: I really like the quality of your Ultra sway bar. I have it sat in the garage waiting for the temperature in their to dip below the 95° to 105°F it's been for the past few weeks.

 

[Little Blue]

See post #19. More than any other options. I believe that Peter Aawen sums it all up my friend.

Ryde Safe and Enjoy your Time.

 

[BajaRon]

PS: I really like the quality of your Ultra sway bar. I have it sat in the garage waiting for the temperature in their to dip below the 95° to 105°F it's been for the past few weeks.

Sounds like you're letting it 'Cure' in the heat! I think you will find it actually does more good on the bike than it does in the box...

 

[mecsw500]

Sounds like you're letting it 'Cure' in the heat! I think you will find it actually does more good on the bike than it does in the box...

Oh I'm sure. But with my arthritis being bad, lying on my back in 100F heat underneath my Spyder whilst I cut the old sway bar with my angle grinder is not going to happen. I can't get the required height with the ramps I have.

With problems I have with my left hand now, does it matter if I push the bolts through from the rear and tighten the nuts on the front of the channel for the bushes and the channel spacers. It might be easier to do it that way than getting my hand up behind the channel on the left hand side to position nuts on the bolts? I'd do both sides the same way of course.

As the original sway bar doesn't bother me too much, I'm used to it allowing my Spyder to roll a bit to the outside so that doesn't phase me at all and it doesn't stop me from enjoying riding it.

I really want to fit it, of course, it's a very nice piece of engineering of which you should be very proud, but the very reasons I gave up two wheels 5 years ago are causing me issues now. I'm not as nimble as I used to be. The stupidity of youth has caught up with me, and some.

If the weather doesn't break soon, I'll take it to the dealer to do, as they are only 4 miles away. It's a long way from Utah to your shop. Ever thought of starting a second pilot location out west somewhere?

 

[Snoking1127]

I don't know if I posted this earlier?
Best way to increase mpg is to slow down.