180/55 R17 Tire Size?

Daytek

Joined
May 5, 2019
Messages
25
Age
48
Location
Canada
Bike
2003 st1300A
Hi Folks

I have searched the forums for tire sizes but cant see anything to really answer my question. I need a new back tire for my ST 13, the bike is new to me and I am wondering if anyone has mounted a 180/55 R17? I am looking at the Metzler Z8.

Cheers
Colin
 
Shawn K said:
Why not mount the correct size? The Z8 is available in 170/60-17 from revzilla.com
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I like the "O" rating on the Metzler Z8. Fortnite only has the "M" rating in the 170. The M Spec is for lighter bikes and the O Spec is for heavier touring bikes. The O Spec has an additional ply in the construction to give it more stability when a bike is fully loaded with luggage and a passenger.
 
Its been years since I ran those sizes on my sportbike, but one thing I noticed back then was the 170/60 had a more rounded profile than the 180/55. For cornering I liked the way the bike rolled over better with the 170/60. I know there's a big difference between riding a sportbike one up and a touring bike two up, but thought I'd mention it anyway and see if anybody here has compared those sizes and noticed any differences in handling.
 
dwalby said:
Its been years since I ran those sizes on my sportbike, but one thing I noticed back then was the 170/60 had a more rounded profile than the 180/55. For cornering I liked the way the bike rolled over better with the 170/60. I know there's a big difference between riding a sportbike one up and a touring bike two up, but thought I'd mention it anyway and see if anybody here has compared those sizes and noticed any differences in handling.
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I agree, back in my sport bike days I loved an aggressive profile.
 
Daytek said:
Hi Folks

I have searched the forums for tire sizes but cant see anything to really answer my question. I need a new back tire for my ST 13, the bike is new to me and I am wondering if anyone has mounted a 180/55 R17? I am looking at the Metzler Z8.

Cheers
Colin
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Go with the another brand that has the O rating in the right size.
 
Hello Colin:

There is only a tiny difference in weight rating between the specified size of tire (170/60, with a load index of 72) and what you are considering (180/55, with a load index of 73). I kind of suspect the difference in handling and longevity between the two would be rather small, though I can't back that thought up with any evidence.

I run Metzeler Z8 tires on my ST 1100, and Michelin PR4 GT tires on my 1300. I really like the Metzelers, they have amazing grip, but the Michelins last twice as long (no exaggeration, exactly twice as many miles) under the same load conditions. So, if longevity of the tire is important to you, you might want to consider the Michelen PR4 GT, which is available in 170/60.

Michael
 
CYYJ said:
Hello Colin:

There is only a tiny difference in weight rating between the specified size of tire (170/60, with a load index of 72) and what you are considering (180/55, with a load index of 73). I kind of suspect the difference in handling and longevity between the two would be rather small, though I can't back that thought up with any evidence.

I run Metzeler Z8 tires on my ST 1100, and Michelin PR4 GT tires on my 1300. I really like the Metzelers, they have amazing grip, but the Michelins last twice as long (no exaggeration, exactly twice as many miles) under the same load conditions. So, if longevity of the tire is important to you, you might want to consider the Michelen PR4 GT, which is available in 170/60.

Michael
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Thank you for your advice. I will look into that tire.
 
CYYJ said:
There is only a tiny difference in weight rating between the specified size of tire (170/60, with a load index of 72) and what you are considering (180/55, with a load index of 73).
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its about 22lb/10kg difference, which is a fair amount of cargo even though its still a small percentage of the overall weight.
 
dwalby said:
its about 22lb/10kg difference, which is a fair amount of cargo even though its still a small percentage of the overall weight.
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Yes for sure. I am really liking what I see with the Michelen PR4 GT. I'm living in Newfoundland and much of my riding is in wet, cooler conditions.
 
Daytek said:
I have searched the forums for tire sizes but cant see anything to really answer my question. I need a new back tire for my ST 13, the bike is new to me and I am wondering if anyone has mounted a 180/55 R17? I am looking at the Metzler Z8.
Click to expand...

My last two rears have been 180/55zr17's,,, always with the 2-ply heavy duty carcass. First was Pirelli,, next was Metz roadtec-01, next will be the Z8 Interact HWM spec. They run long and handle great. I would have changed in the Z8 by now,, but I am still trying to wear the rt-01 out and determine the total mileage life of rt-01 tire first. Cheers, Cat'
 
Does "fit" mean it goes on the wheel and doesn't rub anything, or that it works properly? Tires are made to be run with a specific range of wheel widths. if you go outside that range, the tire profile is distorted vs. what was intended. By the books a 180 tire should have a minimum 5.5" wide wheel. The ST13 wheel is, I believe, 5 inches. No-one would say it wouldn't work, but it may not work as well as the tire that the wheel was designed to use.

When I changed the rear tire on a BMW R1150 from 170/60-17 to 180/55-17, I changed the rear wheel from 5 in. to 5.5 in, seen here.

DSC03331-M.jpg


Bikes are engineered from the tires up. As soon as you change the tire size, congratulations, you are now the engineer. Now you have to hope that you are better at it than the team of engineers who did it originally with all of the resources that they had at their disposal. If wider is always better, then a 3 ft. wide tire ought to handle really well. Frankly, between the two tire widths on my R1150, other than looks, I preferred the narrower one. Whether or not this experience translates to ST's, I don't know - but I think it would.
 
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Beemerphile, I have always thought this too.....That after a lot of engineering of the bike next comes the engineering of the best tire for the model. But alas there may be two school of thoughts here. School #1 a lot of testing and specs went into that tire during the CAD design of that bike. School #2 The manufacturers will put out bids for the cheapest tire they can get away with. I'm a fan of #1 school of thought.
 
Here in Spain the tyre sizes are specified on the Ficha Tecnica, which is a document issued with every vehicle by provisional governments. If any other tyre size is fitted, the vehicle will not pass the periodical inspections.
The tyre sizes specified on my Ficha Tecnica are Front 120/70ZR18 51W Rear 170/60ZR17 70W. I am therefore limited to those sizes.
 
red one said:
Beemerphile, I have always thought this too.....That after a lot of engineering of the bike next comes the engineering of the best tire for the model. But alas there may be two school of thoughts here. School #1 a lot of testing and specs went into that tire during the CAD design of that bike. School #2 The manufacturers will put out bids for the cheapest tire they can get away with. I'm a fan of #1 school of thought.
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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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beemerphile said:
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.
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FWIW, a 5.5 inch rim is considered acceptable for either the 170/60 or 180/55, but the 5.0 inch rim is not considered acceptable for the 180/55.
 
Daytek said:
Hi Folks

I have searched the forums for tire sizes but cant see anything to really answer my question. I need a new back tire for my ST 13, the bike is new to me and I am wondering if anyone has mounted a 180/55 R17? I am looking at the Metzler Z8.

Cheers
Colin
Click to expand...

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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