Wrong Tire Size: Is this a big deal?

[OlGeezer]

I picked up a new front tire yesterday and just realized it's the wrong size. It's a Michelin Road Pilot 2, front tire, size 120/60 ZR 17 instead of 120/70.

 

What are the consequences if I mount it instead of returning it?

 

Tks.

[Deadboy]

With the mileage you ride it will be ready for replacement before you can ship it back and get another one....

 

I wouldn't worry about it!

[OlGeezer]

I haven't been putting on the miles like I used to. The tire I'm taking off is over a year old. Seriously. I'll be ready when this recession is over.

[cruisin]

the only real difference will be the tire sidewall height. The 120/70 measures 84mm on the side wall while the 120/60 measures 72mm. It will throw you speedometer off slightly if it is going on the RT as it's speed/odo read off the front wheel.

[OlGeezer]

the only real difference will be the tire sidewall height. The 120/70 measures 84mm on the side wall while the 120/60 measures 72mm. It will throw you speedometer off slightly if it is going on the RT as it's speed/odo read off the front wheel.

 

That's what I figured. The difference is 4% (23.61 in OD vs. 22.67 in.). It's already off 3%, but I use GPS as my speedo. Maybe this will help me get to 200k a little quicker!

[Mike T]

This happened on my R1200RT with a set of Dunlap Roadsmarts. The front wore out in about 4K miles while the rear was good for about 7K. I didn't realize that the local shop had put the wrong size (same size as yours) on until I went to order a new tire. I cannot say for certain that the smaller outer diameter caused the premature wear. I ran 40psi in the front at the time (I now run 36psi). I now change my own tires to avoid these mistakes.

[StuGotz]

This happened on my R1200RT with a set of Dunlap Roadsmarts. The front wore out in about 4K miles while the rear was good for about 7K. I didn't realize that the local shop had put the wrong size (same size as yours) on until I went to order a new tire. I cannot say for certain that the smaller outer diameter caused the premature wear. I ran 40psi in the front at the time (I now run 36psi). I now change my own tires to avoid these mistakes.

 

Your front wore out faster than the rear due to different construction, not tire size.

 

Dunlop Roadsmart rear is of dual compound, front is single.

 

MB>

[OlGeezer]

Your front wore out faster than the rear due to different construction, not tire size.

 

Dunlop Roadsmart rear is of dual compound, front is single.

 

MB>

This fact alone convinces me that I picked the right tire if not the right size. Since my mileage has decreased, I'm switching from ME 880s to get a tire that, hopefully, will give me some grip on wet pavement.

[StuGotz]

Your front wore out faster than the rear due to different construction, not tire size.

 

Dunlop Roadsmart rear is of dual compound, front is single.

 

MB>

This fact alone convinces me that I picked the right tire if not the right size. Since my mileage has decreased, I'm switching from ME 880s to get a tire that, hopefully, will give me some grip on wet pavement.

 

Then you'll like the PR2...last year came back from DVD in torrential downpour. Year before that snow, hail, rain, wind.

 

I'm convinced I'm on the right tire for my RT, at least until I find one better...

 

MB>

[OlGeezer]

This happened on my R1200RT with a set of Dunlap Roadsmarts. The front wore out in about 4K miles while the rear was good for about 7K. I didn't realize that the local shop had put the wrong size (same size as yours) on until I went to order a new tire. I cannot say for certain that the smaller outer diameter caused the premature wear. I ran 40psi in the front at the time (I now run 36psi). I now change my own tires to avoid these mistakes.

 

The difference is 4%. So, instead of getting 10k miles, I should get 9.6k. The tire size wouldn't account for the difference you report. Just curious, but how did you arrive at the reason to change air pressure?

 

 

[Peter Parts]

There will be "faster" handling. Depending on the sensitivity of your butt-gauge. The difference is kind of like half of what people do when doing rear reaction-strut switheroos... on other models.

 

You might well like the change because it shifts the bike in the "sporty" direction.

 

You might notice the lowered seat height too. Every little bit is detectable.

 

Try it.

 

Ben

[Mike T]

 

Your front wore out faster than the rear due to different construction, not tire size.

 

Dunlop Roadsmart rear is of dual compound, front is single.

 

MB>

 

Actually, the Roadsmart front tire is a dual compound. You could see the different wear characteristics on the sidewalls vs the center of the tire.

[Mike T]

 

 

The difference is 4%. So, instead of getting 10k miles, I should get 9.6k. The tire size wouldn't account for the difference you report. Just curious, but how did you arrive at the reason to change air pressure?

 

 

I reduced my tire pressure to 36psi to comply closer to what the BMW manual recommends. I was wondering if the increased pressure that I had been using may have contributed to the premature/uneven wear of the Roadsmart front tire (counter intuitive I realize). I also found that the front of the bike feels more secure at highway speeds when you get caught in the backwash of a truck in front of you. I now run RP 2's and really like the way they perform on the bike.

[kmac]

I only have 1 idea that could make this a problem. Overall i dont think the mileage is an issue, very minimal change, and the handleing may change a bit, but that also will only be minimal. If you really ride the twisties aggressively, you may like the new size better.

 

My potential issue would be with the speed sensors on the wheels for yje anti-lock brakes. If the front wheel is turning faster than the system is programmed to run it could cause an issue under panic braking? Not sure of exactly how the system works, maybe it will not affect it. It work simply off of rapid change in rotation speeds which would not be affected by a slight diameter difference.

Just something to think about and maybe research. I think the may be an issue on a bike with traction control possibly.

[StuGotz]

 

Your front wore out faster than the rear due to different construction, not tire size.

 

Dunlop Roadsmart rear is of dual compound, front is single.

 

MB>

 

Actually, the Roadsmart front tire is a dual compound. You could see the different wear characteristics on the sidewalls vs the center of the tire.

 

And where does your info come from? As of last summer, all info from Dunlop that discussed dual compound was only related to the rear tires.

 

If they've changed, I'll stand to be corrected.

 

Nonetheless, you WILL experience shorter life with the front tire.

 

MB>

[CoarsegoldKid]

kmac, may be right but I don't believe a shorter profile will effect the ABS effectiveness. IF the system uses both the rear and front sensors together to trigger ABS during an impending lockup and one wheel is 4% slower or faster than the other I suppose it could be something to think about. I suspect the computer learns and compensates. On the other hand if a worn front tire produces a different speed than a new rear that would have the same effect as a low profile tire. Again the computer does it's magic. I hope.

[OlGeezer]

I've solved the conundrum. I swapped the tire out for the correct size today. This happened right before I was going to pose the question "Will I age 4% faster with the lower profile tire?"

[cali_beemer]

 

Your front wore out faster than the rear due to different construction, not tire size.

 

Dunlop Roadsmart rear is of dual compound, front is single.

 

MB>

 

Actually, the Roadsmart front tire is a dual compound. You could see the different wear characteristics on the sidewalls vs the center of the tire.

 

And where does your info come from? As of last summer, all info from Dunlop that discussed dual compound was only related to the rear tires.

 

If they've changed, I'll stand to be corrected.

 

Nonetheless, you WILL experience shorter life with the front tire.

 

MB>

 

The Roadsmart rear is a dual compound, the front isnt. The PR2's use a dual compund front and rear. When I had a roadsmart front tire on my 1200RT it ore very fast like 4-5k miles.

[jfremder]

I'm switching from ME 880s to get a tire that, hopefully, will give me some grip on wet pavement.

 

ANYTHING is better than ME880's in the wet....

[cruisin]

I'm switching from ME 880s to get a tire that, hopefully, will give me some grip on wet pavement.

 

ANYTHING is better than ME880's in the wet....

 

that's odd, I have used the ME880s over the past 7 years and ~190K miles and have never had a problem with their wet-road performance. Of course I tend to slow down on wet roads.

[Paul Mihalka]

"that's odd, I have used the ME880s over the past 7 years and ~190K miles and have never had a problem with their wet-road performance. Of course I tend to slow down on wet roads."

 

Ditto... last 125K on R1100RT, 70K on R1150R, 100K on R1200GS front (no good size for rear)

[g_frey]

Other than a greater risk of rim dents from a wicked pothole I don't believe it will make much difference. Sometimes over the last 30 years I have not been able to find the right tire so I have made do with no bad results that I could tell. Quite frankly, looking back, some of the choices were very poor but they worked.

[Mike T]

 

Your front wore out faster than the rear due to different construction, not tire size.

 

Dunlop Roadsmart rear is of dual compound, front is single.

 

MB>

 

Actually, the Roadsmart front tire is a dual compound. You could see the different wear characteristics on the sidewalls vs the center of the tire.

 

And where does your info come from? As of last summer, all info from Dunlop that discussed dual compound was only related to the rear tires.

 

If they've changed, I'll stand to be corrected.

 

Nonetheless, you WILL experience shorter life with the front tire.

 

MB>

 

Sorry MB. I stand corrected. It is only the rear that has the dual compound not the front. Amazingly the front wore more on the sides of the tire leaving a big hump (not flat spot) in the center. I mistakenly thought it was due to a harder compound being used in the center (wrong conclusion).