Tire change

[mrmike]

  I have a '23 People S150i ABS. When I put it back on the road this spring, I'm going to upgrade to Michelin City Grip 2 tires for the better wet weather traction and handling. On the '12 GTI 300 I had, I did the same thing and upsized the front tire to a 120/80-16 replacing the factory 100/80-16 to improve the handling and correct the factory speedometer. I plan on doing the same thing this time. Are there any negative reasons for doing this change?


P. S.   Where is the best place to buy the City Grip 2's?

[Stig / Major Tom]

I get my Michelins from revzilla. Fresh dates on the tires every time.

My parts guy told me that increasing the width of the tire - without increasing the width of the rim - leads to a smaller contact patch.

Stig

[Iahawk]

I think it's more accurate to say that changing the width of a tire changes the shape of the contact patch, not so much the size. Wider isn't always better, either.  Do an online search of this issue if you want to go down the endless rabbit hole.

[Stig / Major Tom]

I think it's more accurate to say that changing the width of a tire changes the shape of the contact patch, not so much the size. Wider isn't always better, either.  Do an online search of this issue if you want to go down the endless rabbit hole.

Hawk, I know this is debated forever....
One sad day I was at my selling dealer for a repair as they unloaded my Forza, with its destroyed rear tire.
Here I learned from the old gent at the parts counter,  that Honda had sold this scooter in the USA with no correct sized replacement tire available in the USA!*
IBD'd!
He said he could go one size up - in stock.
I said, "well, that'd be great. I'll get better grip..." referring to the road contact.
He said, "one size up would not be a serious problem at all, if it clears fender, etc. - but no, you won't be gaining better grip."

I said, "why not?"

 He went back and came out with a new tire. He put it up on the counter top and demonstrated for me. He took the tire, held it by its inner rim....and pinched it in to show me that the shoulders of the contact patch lifted away from contact with his counter top. "This is what happens when you increase the width of a tire, but not the width of the rim. It's usually only a small difference in road contact - but it's not an increase!"

In short he said - buy the correct size tire for your rim, as decided by the manufacturer.

It sure made sense to me....
the defense rests.....

Stig
* and no, he wasn't fibbing to me. At that time there was not a correct size replacement for that rear Dunlop....in this country!

[Stig / Major Tom]

Hawk, I know this is debated forever....
One sad day I was at my selling dealer for a repair as they unloaded my Forza, with its destroyed rear tire.
Here I learned from the old gent at the parts counter,  that Honda had sold this scooter in the USA with no correct sized replacement tire available in the USA!*
IBD'd!
He said he could go one size up - in stock.
I said, "well, that'd be great. I'll get better grip..." referring to the road contact.
He said, "one size up would not be a serious problem at all, if it clears fender, etc. - but no, you won't be gaining better grip."

I said, "why not?"

 He went back and came out with a new tire. He put it up on the counter top and demonstrated for me. He took the tire, held it by its inner rim....and pinched it in to show me that the shoulders of the contact patch lifted away from contact with his counter top. "This is what happens when you increase the width of a tire, but not the width of the rim. It's usually only a small difference in road contact - but it's not an increase!"

In short he said - buy the correct size tire for your rim, as decided by the manufacturer.

It sure made sense to me....
the defense rests.....

Stig
* and no, he wasn't fibbing to me. At that time there was not a correct size replacement for that rear Dunlop....in this country!

Next, until it stops snowing, let's talk using that tractor oil (SHELL Rotella) in scooters!

Stig

[scooterfan]

 He went back and came out with a new tire. He put it up on the counter top and demonstrated for me. He took the tire, held it by its inner rim....and pinched it in to show me that the shoulders of the contact patch lifted away from contact with his counter top. "This is what happens when you increase the width of a tire, but not the width of the rim. It's usually only a small difference in road contact - but it's not an increase!"

Stig
* and no, he wasn't fibbing to me. At that time there was not a correct size replacement for that rear Dunlop....in this country!

I actually don't want to go down the rabbit hole but I am quite convinced a slightly bigger tire - mounted on an original rim, and inflated to tire specs will "act" different from a loose (uninflated) tire on a counter top.

A couple of years ago I've actually mounted a slightly bigger than standard tire (City Grip) at the rear of my previous Agility. At the time I was quite convinced that the bigger tire indeed had a slight bigger contact to the road.

Having said that - different same size tires from different brands do not always have the same size contacr areas to the road.
For examle - when I bought my Silverwing it came with a front tyre with a vey narrow contact area at the center of the tire. Due to this tire the Silverwing was quite unstable when I was riding on roads with rain grooves. Spesically during a combination of rain grooves and  windy conditions handling the Silverwing became quite a nightmare. Mounting a similar size tire from another brand has caused a major improvement.

As far as getting a more correct speed reading with a bigger tire - I think a bigger tire on a standard rim might only cause a small correction (if any) - because if a bigger tire gets mounted to a standard rim the angle of the sidewall will be different, therefore probably causing the tire to be slighty lower than usual.

I wouldn't be too bothered about the contact area becoming "smaller" on a bigger tire.As time goes by any given tire wears by time. Specially on a motorcycle or scooter tire the center part of the tire normally wears faster and sooner or later the tire will have a wider contact area anyway.

[Ruffus]

.....upsized the front tire to a 120/80-16 replacing the factory 100/80-16 to improve the handling and correct the factory speedometer. ...

 This would be interesting to know details, for our Kymcos (other brands too) are way to optimistic in showing speed.

[mrmike]

.....upsized the front tire to a 120/80-16 replacing the factory 100/80-16 to improve the handling and correct the factory speedometer. ...

 This would be interesting to know details, for our Kymcos (other brands too) are way to optimistic in showing speed.

I've had 4 new Kymco scooters so far. They were all about 2MPH fast. I put the bigger size City Grip on my '12 GTI300i. I saw a thread in this forum that made me do it. I didn't have a GPS then, so I couldn't tell if it helped correct the speedometer. When I go to my new tires in the spring, I'll let the forum know if it made any difference.