Larger rear tire: does it change speedo?

[Chris S]

In a previous post some members mentioned that they had mounted a 150/70-13 rear tire because of the lack of availability of the 140 size in North America. I just wondered if the increase of the circumference has changed their speedometer and/or odometer readings. I know that in the past I had changed to a larger profile rear tire on a Lambretta and the speedo decreased, but that was old technology. Ya I'm old too. Anyway any input would be appreciated. Thanks.

[iceman]

Someone posted about this is another thread the past weeks, saying the meters are slightly out with different size tyres due to more road covered per spin of the wheel.

[gn2]

Fitting the wrong size tyre will affect both the speedo and the ABS.
The correct size tyre should be available from official Honda dealers.

[Mgalutia88]

I installed a 140/70-14 on my pcx and the speedo rea slower than real speed by 1.5-2 mph but I lost 10mpg and 5mph in top speed AND performance. The wider tire is nice I you ride below 60mph. If you ride above that don't change sizes.

[Chris S]

thank you. will try the dealership for replacement.

[sean]

I replaced the standard Honda dealer rear tire with the same tire. But I'm dis-satisfied with the first one. I only got 4500 miles. I'm waiting to hear about how those other tires perform after a few thousand miles.

[gn2]

The original rear Scootsmart on my Forza lasted 7000 miles.
It was made in Indonesia, replacement Scootsmart made in Slovenia.

[BRed]

This thread made me curious, so I checked several Honda OEM parts suppliers......
all list the Dunlop ScootSmart as "on backorder"....
that doesn't bode well for a one year old scooter, especially if you chose the ABS model and are forced to stick to matched tires sets, that are "on backorder"?

I like Dunlop tires.....they make well-balance, high traction tires, but not notably long-lived tires.....
given the choice of tread life or traction, I'll take traction any day.

on motorcycle tires, high mileage and excellent road traction are usually mutually exclusive.
The most grippy high traction tires use soft pliable rubber and it wears FAST!
High mileage touring type tires use much harder compounds for extended wear and these tires "get loose" in corners sooner and usually require you to drop more speed in rain than do soft grippy performance tires.


think of it as a sliding scale with Maximum Traction on one end and Maximum Tread Life on the other end.....
then pick your poison!

The ScootSmart sounds like a reasonable tire, giving 7000 miles with conservative use and 4500 miles with more aggressive use....
that actually sounds about right to me.

I mount my own tires and with 70000+ miles on my scoots, I've chewed through a lot of rubber....
in highway use, 3500-4500 miles on a rear scooter tire is fairly good mileage (for me?)

The Michelin Power Pure is the first scooter composite tread tire, with a 2-3" hard rubber centerline and soft grippy shoulders

[iceman]

Michelin Power Pure sounds good. Most highly rate the city grip, and it seems the stock tyre and michelin city grip do not quite align themselves with the grip vs life equation you give, although that makes %100 sense i.e. stock tyre - not so great grip, poor life compared to city grip which people say has much more grip!

[BRed]

I tried set of the City Grips when they first came out (they replaced the Michelin Gold Standard scooter tire line)....
as the name implies, a very grippy tire, but the rear one on my BR developed a bald spot (12" strip with almost no tread!) on one side after 2300 miles.

That may have just been one individual tire, but I've never been motivated to try a second one, since the Power Pure was released a year later.
I got 6600 miles on the first Power Pure I tried and have almost worn out the second one at just under 7000 miles....
most of those are 70mph highway miles.

[forza300]

I installed a 140/70-14 on my pcx and the speedo rea slower than real speed by 1.5-2 mph but I lost 10mpg and 5mph in top speed AND performance. The wider tire is nice I you ride below 60mph. If you ride above that don't change sizes.

I know this is an old thread but.... you just nailed this debate for me. Thanks!

I think I'll be sticking to the standard tyres as I do occasional short stints in 80-100kph zones (try to avoid them though).

[Forza 300]

I put a city grip on my sh 150 and it's the best tire I ever rode on , long lasting and above average grip and smoother ride, I have installed a city grip one size larger then factory and I do have abs on my forza I don't think there will be any problem as manufactures have to allow for the rear tire to wear faster then front tire therefore different speeds usually + or minus 4% is allowed .

Don

[TechFrog]

I changed my stock rear from the 140/70/13 to a 150/70/13. This will change the speedo and the odometer and the fuel calculation slightly. Here are the numbers:

140/70/13... Diameter: 20.7" Circumference: 65" Revs/Mile: 974
150/70/13... Diameter: 21.3" Circumference: 66.8" Revs/Mile: 949


The Forza speedo is optimistic, and the tire increase actually brought it down to reality (as verified by my GPS) That being said, let's say for conversion sake that the stock Forza was spot on. Here is the conversion:

Speedometer reading 35. Actual speed with larger tire is 35.93
Speedometer reading 55. Actual speed with larger tire is 56.46
Speedometer reading 75. Actual speed with larger tire is 77.

If you fill your tank at about 190 miles, you'll have actually gone slightly over 5 miles (8 kilometers) farther on that tank than indicated.

Now because the variator keeps you in the optimal powerband in the city, fuel economy will likely not change in the city.
As for the freeway (or hwy) cruising at a lower RPM typically helps fuel economy but not always if you're not in the optimal torque band. With many engines, there are times being in too tall of a gear hurts more than helps. In the case of the Forza, for me, my highway actual mileage has improved because I'm still going about the same indicated 190-200 miles between filling up, meaning I'm consistently going about 5 miles further per tank of fuel.

Since no gain comes free, two things that are technically compromised are:
1. Power off the line. The taller tire will technically have a higher gear to overcome the first few seconds or so before reaching optimal torque since variators do not start you in the torque band, but it's not noticeable.

2. Passing power from about 65 and up since the variator won't really come out of "top gear" in that range too often. But trust me, you really don't notice this either.

Happy scooting

[fish]

I chose to go with the one size larger tire when i had my flat, to get me back on the road ASAP.
I will say this - the speedo was now absolutely dead accurate with the larger tire installed!
Checked it through 3 speed traps.
I noticed no other difference in the scooter....but then I didn't ride highways or GP it through corners.
Not my style.
Sorry, can't remember what tire it was - Pirelli, or Continental?
Dealer had it in stock and fitted the same afternoon.
Fish

[homie]

Fitting the wrong size tyre will affect the ABS.

Going to need to produce proof of this statement GN, I have no issues with ABS on my over sized truck tires and I want nothing to do with ABS on any bike if it restricts tire choices... ever! That would be a serious mistake by makers if true. You must be referring to tire height and not width on bikes and that still does not explain how cars and trucks do fine with ABS and height changes in tires.

[gn2]

Going to need to produce proof of this statement GN

How about a pretty girl instead?

[homie]

I wouldn't mess with Spidermans woman even if she is Irish

[davenowherejones]

I have the Michelin CityGrip 150 on my 2014 Forza 300. The Scootsmart lasted until 9800 km. At 8000 the Scootsmart was getting thin and I picked up a small staple. I had the tire plugged until I could get the Michelin, delivery took a while.

Sidecar Willie in Hope put on the CityGrip and I now have 10,000 km on the rear and it still looks almost new. My front is looking wonky so I ordered a Michelin front yesterday.

I have taken the scooter to a parking lot and tested the ABS. It seems to work just fine. I jammed on the front and it stopped with no problems. I did the same with the rear. Both together stops the scooter almost faster than I can think. No problems. The loose gravel did not affect the abs either. It just works.

[fish]

Dave,
A question.
In your stopping tests with oversized tire.....did you stop hard enough for the ABS chatter to be felt? In other words. ..was your scooter just stopping very quickly. ..or could you feel the ABS actually being deployed?
Thanks
curious Fish

[davenowherejones]

Dave,
A question.
In your stopping tests with oversized tire.....did you stop hard enough for the ABS chatter to be felt? In other words. ..was your scooter just stopping very quickly. ..or could you feel the ABS actually being deployed?
Thanks
curious Fish

I definitely felt the chatter. I accelerated as hard as I could and then just jammed on the brakes until I stopped. With the G-forces involved I had to react quickly to get a foot down when I stopped so suddenly.

There was some gravel in the parking lot from when I spilled some oil while changing it in my lawnmower. The gravel got dragged along under the tire while the ABS did its thing.

One of the reasons I was in the parking lot was because I wanted to develop a little muscle memory as to what working ABS felt like. Some people feel the chatter and get real scared so they do dumb things. It happens a lot in cars, they feel the brake pedal shudder so they let off the brakes and crash into things.

The ABS works almost too good. I miss the out of control fishtailing and skillful recovery.