180/55 R17 Tire Size?

beemerphile said:
I am speaking of tire size and construction rather than brand, cost, or quality. The dimensions of the tires affect the suspension geometry (rake, trail, etc.) . The height of the rear tire affects gearing as well as the rake angle of the front suspension. It also affects little attributes such as whether the centerstand still works. Ask someone with a 170/60 tire (the ST13 size) on the rear of an ST11 how much more fun it is to hoist the bike onto the centerstand. As a simple example, I once bought a 120/60-17 front tire by accident for a BMW K1100RS instead of a 120/70-17. I didn't even notice the error until after I had mounted the tire. It steered horribly. Meanwhile, a 1999 Kawasaki ZX6R comes stock with the 120/60-17. Put a 120/70 on the front of that bike and it's steering becomes squirrelly. Neither tire size is "better". But using the specified tire for both bikes lets the bike engineer remain the bike engineer. The tire width / rim width match-up affects the both the rolling diameter and the profile of a given tire. Using another BMW example, BMW had a R1150R Roadster that used a 170/60-17 rear tire on a 5 inch rear wheel. There was a sister model called the R1150R Rockster that had a 180/55-17 rear tire, but BMW installed it on a 5.5 inch rim. If they could just spoon a 180 onto the 5 inch wheel (it will "fit"), then why would they go to the expense of tooling a 5.5 inch wheel. After all, a half-inch isn't much, is it? They did it because it allows the 180 tire to assume the designed profile and operate as intended by the tire designer. Put the 170 on the Rockster or the 180 on the Roadster without changing the wheels and you will screw them both up. But I know of people who run 180's on the Roadster 5 inch wheels and they say it handles better. I do not believe them. I had both wheels and a tire machine in my shop and wasn't even curious enough to try it because I don't think I am smarter than either the tire engineer or the motorcycle engineer.

If you could find a Honda engineer, you could ask them why the went from the 4.5" rear wheel on the ST11 to a 5" rear wheel on the ST13 when they upped the tire size from 160/70 to 170/60, or why they increased the ST11 front wheel from 3" to 3.5" when they fitted the 120/70-18 tire on the ABSII model in place of the 110/80-18.
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bigger is better ... all the super bikes like the bmw s1000r or the ducati monster use 190/55 tires , more rubber on the pavement means better traction and I think they handle really, really well:thumb:
 
Just placed my next tires order this morning. Don't worry about the pricing,, as those are cdn$$$'s, free shipping included. This is my 3rd Z8 front tire, and will change in mid-summer. This has been the best front tire model that I have had on my ST13. I will see if the Z8 rear performs up to the level of the Pirelli GT A-spec and the Metz Roadtec-01 HWM-spec.,, cheers, Cat'

Metzeler Roadtec Z8 Interact Sport Touring Front TireTire Size120/70ZR18 (M Spec)​
CM1032521​
1​
$155.99​
Metzeler Roadtec Z8 Interact Sport Touring Rear TireTire Size180/55ZR17 (O Spec)​
P310327​
1​
$200.99​
 
Al st1100 said:
bigger is better ... all the super bikes like the bmw s1000r or the ducati monster use 190/55 tires , more rubber on the pavement means better traction and I think they handle really, really well:thumb:
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And both of them have 6 inch wide rear wheels. They don't handle "really, really well" because the manufacturers stuffed 190 tires onto 5 inch rims, nor does it follow that if you stuff 190 tires onto your ST13 that it will handle like a BMW S1000R or a Ducati Monster.. You can't get to there from here.
 
Jjonahjamison said:
I was on a long road trip and needed a new tire in eastern Oregon. The nearest (and only available) bike shop didn't have a Michelin Pilot Road 5 GT in stock size, but did have one in 180/55 R17, and they said it would be fine. They mounted it up and over the life of that tire I noticed zero difference in handling, tire life, etc.

I drive "spiritedly" pretty much all the time as virtually all of my riding is on long road trips. Based on my experience if you can't easily get the stock size, running the 180 is just fine. I think its a more commonly used size as well, so if you run out of tire in a smaller or remote town, they might be more likely to have this one.
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This is exactly the same scenario I experienced only in Colorado rather than Oregon. Over the life of the 180/55 I could notice no significant difference from the 170/60. Maybe the 180 did not initiate a turn as easy as the 170 but once they both get squared off a little bit, I doubt anyone but an expert could tell in a blind "taste test". If you look at the chart above, the difference is about what it would be between a brand new 170 and a 170 at the end of its life given the tread depth is about 1/4".
 
drrod said:
If you look at the chart above, the difference is about what it would be between a brand new 170 and a 170 at the end of its life given the tread depth is about 1/4".
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If you think about it, the difference is actually half that amount or 1/8" because radius is what determines ride height, not diameter. Or stated another way, your worn out 170 is about 1/2" less in diameter than a new tire. Don't have any opinion on whether you should or shouldn't mount a 180, just keeping the math honest. That said, the rolling diameter/circumference is only one variable, the way the tire profile changes when its wedged onto a rim that it wasn't intended for is also another variable.

And, back in the day when I went through a few tires per year I used to keep a database on the circumference of different tires and different sizes. The variation between different brands/models of tires of the same nominal size was at least as significant as the difference between the theoretical 170/60 and 180/55 sizes in that online chart. So even if you constantly run 170/60 you're going to see differences in circumference and width from one brand/model to another.
 
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That is a good tire calculator that Whooska provided. I have been using it forever, on both bikes and sportscars. Before choosing to run my 180/55 tires, I checked the difference in diameter/circumference and found that the 1% would be less error than speedo/odo was already showing when running the oem tire spec's (that's an old Honda issue). I have long time used a digital speedo for the sake of accuracy. Anyway,, the 180/55 tire brands and models that I mentioned in earlier posts on this thread are considerably better in every way than the 170/60 Dunlop rear tire that my bike came with. My experience so far is that the dimensional differences between those two sizes are imperceptible, imho. This forum is great for doing your homework on just about any issue,,, isn't it,, cheers, Cat'
 
"....difference is actually half that amount or 1/8" because radius is what determines ride height, not diameter. ......"
Actually the difference in diameter is 1/2" (1/4" tread depth on full circumference) so the radius is reduced by 1/4" from full tread to wore out.

"... the rolling diameter/circumference is only one variable, the way the tire profile changes when its wedged onto a rim ....."
The whole tread face/profile changes as the tire is wore. How it changes depends on how much is wore off and where it is wore off. eg. wide chicken strips or no chicken strips.

The point I was trying to make is that the tire's characteristics/shape/profile change as soon as there is any wear on it and the difference between a 180/55 and a 170/60 is not significant over the life of the tire.

Granted, the "wedge" profile changes depending on rim width but the wedge profile varies significantly from one brand to another anyway.

Taking the "engineer designed" logic to the extreme, you should not fit anything other than a Bridgestone 020F since that is the OEM tire.
 
drrod said:
"....difference is actually half that amount or 1/8" because radius is what determines ride height, not diameter. ......"
Actually the difference in diameter is 1/2" (1/4" tread depth on full circumference) so the radius is reduced by 1/4" from full tread to wore out.
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referencing post #25 it says "0.24 inches smaller in diameter" comparing the two different tire sizes, your italicized text above was my comment on that difference.

referencing a new vs. worn tire I already stated that is about a 1/2" difference in diameter in my previous post.
 
beemerphile said:
And both of them have 6 inch wide rear wheels. They don't handle "really, really well" because the manufacturers stuffed 190 tires onto 5 inch rims, nor does it follow that if you stuff 190 tires onto your ST13 that it will handle like a BMW S1000R or a Ducati Monster.. You can't get to there from here.
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no but it will have better traction ... more rubber on the ground equals better traction , fact of life
 
Al st1100 said:
no but it will have better traction ... more rubber on the ground equals better traction , fact of life
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Except in the wet. More area for a given weight results in less weight per a given area. That means lower pressure to break through the layer of water on the pavement.
 
Larry Fine said:
Except in the wet. More area for a given weight results in less weight per a given area. That means lower pressure to break through the layer of water on the pavement.
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motogp doesn't seem to have a problem racing in the rain with lighter bikes and huge tires...except, yea there are lots of variables but we are talking just a lightly larger tire;)
 
Pointless discussion; in spite of what is said, some try things outside the box and it works well for them or it doesn't. :)

I’ve mixed brands, bias and radial, and tried different sizes (width and profile), some I liked, some I didn’t. I never felt it was unsafe or even disliked handling enough to dismount ANY tire once I mounted it. Any new tire experiment always felt better in the handling department than the worn tire I had just removed.

Tom
 
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TPadden said:
Pointless discussion
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^ Something we can agree on. ^

Some people undertake things in a rigorous manner and others go seat-of-the-pants. Doesn't matter the topic, the two factions will never agree and neither will ever convince the other of the error of their ways. When the "discussion" goes on long enough it usually descends into personal insults. So, yeah, pointless discussion. I'm trying to learn to shut up, but I'm not doing so well at it. To help me I"ve put a label on my computer monitor that says "I have no opinion on that." Maybe that will help.
 
TPadden said:
Of course pointless doesn't necessarily mean it isn't entertaining. Once I'm entertained by any discussion here that usually means it's on Joe's short list for locking or deletion. :thumb:

Tom
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oooohhh.. I heard my name!!.... what's going on here... better take a look if Padden is entertained, that's never a good thing... ding ding ding..
 
Thanks for all the discussion. I went with the Michelin PR4 GT, 170/60 R17. Considering 40% of my riding is in rain and cooler temperatures. The reviews say these are designed for these conditions. I guess time will tell.
 
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I just put 1039 miles on a 180/55/17 Pirelli Angel GT2 A-Spec last week. Handled just fine. Couldn't even detect any difference from the 170/60.

Did I mention that GT2 was awesome?
 
Ok,, time for me to fess up regarding the rear Metzeler Z8 180/55r17 O-spec that I recently installed. Prior to the Z8 I had excellent results from the same tire size, in both the Pirelli Angel GT A-spec,, and the Metzeler Roadtec-01 HWM-spec, both which ran very well for 20k kms and 21.5kms respectively. I was very optomistic that the Z8 would rival those performances,, but it was not to be. Immediately after a perfect (no weights required) installation, I hit the open road and a harmonic vibration presented at 85kph while in 5th gear only. This was the first time I have experienced such a resonating vibe, like ####,,,,,,####,,,,,,####. Pull in the clutch no vibe. Speed up above 90kph, no vibe. Slow to 80kph, no vibe. Drive 85kph in 4th gear, no vibe. After googling for "metzeler Z8 harmonic vibration",, I found reports of this phenomena for Z8's on various sport touring riders forums,, FJR, BMW, Concours,, and even ST's. Now this is not a severe vibration,,, and it occurs in a narrow speed range that I don't spend much time traveling at. But I am an ST pilot,, dog gone it,,, so a new Roadtec-01 replacement tire arrived today from my new tire supplier. My old tire supplier is no longer getting my tire business,, because they essentially laughed at my warranty claim. btw,,, the new price for the Roadtec is %24 less than my old suppliers price was. Anyway,, because I had earlier expressed optimism about the performance I expected from the Z8 I felt I should warn others about what I have experienced. All I can say is that I believe some Z8 rears will exhibit a resonant harmonic vibration (which is a combination of engine and tire vibrations). I would hate for others to find out the hard way, as I did,, because I kept quiet. Oh,, the overall final results of my 3 tire tests are,,, imho,,, an A score for the Pirelli GT,, an A+ for the Roadtec-01,, and a C for my vibro Z8. Cheers,, Cat'
 
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