Michelin PR3 on ST1100 Rear - smaller size OK?

Outlaws · Dec 29, 2013

ArTravlR said:
Going east on I-40 with a heavy load, a 160/60 Dunlop on the rear, strong wind blowing from the left and an oversized windshield, I found my front handlebar would oscillate left & right while tracking straight down the road. Frightening is an understatement. The weight bias was to the rear and the smaller tire affected the geometry of the bike in this extreme instance. ****** I am mildly surprised at the resistive comments on this vital safety issue and will not comment any further.

I'm sorry, I was going to stay out of this one but this is too funny...

All of the other stuff noted going on and the smaller tire size affected the geometry causing the handlebar oscillating problem, seriously???

I ride low with a short shield, have a fork tube brace and custom belly pan but when there is a 40+ mile an hour cross wind it gets a little twitchy...
Best investment is keeping the fork oil fresh and a quality rear shock, Progressive Suspension 465-1128 in my case.

Have had 3 different brand 160/60ZR17s on the rear of my '91 over the years and the only concern I've ever had was the kickstand angle.
Currently have a PR2 and expect to replace with a PR3 when it's shot in the spring.

And I only use factory oil...

Uncle Phil · Dec 29, 2013

I noticed that you said 160/60 not 170/60 - just curious as to which one it was? IIRC, the overall dimension differences between a 160/70 and 170/60 are pretty small. The PR3s I run are the same tires that fit an ST1300 - the front is an exact match , the rear is 170/60 versus 160/70. But then I don't ride much either ... ;-)

Just for grins - the math is here -

http://www.tacomaworld.com/forum/tirecalc.php?tires=170-60r17-160-70r17

**EDITED TO CORRECT - THANKS BROC!!!***
Looks like on the 170/60 vs 160/70 you gain 10 mm in width and lose 10 mm in sidewall height which is .39 inch difference. On the 160/60 vs 160/70, width is the same but you lose 16 mm in sidewall height which is .63 inch difference. So to me the 170/60 is a close fit than the 160/60.

Outlaws · Dec 29, 2013

Uncle Phil said:
I noticed that you said 160/60 not 170/60 - just curious as to which one it was? IIRC, the overall dimension differences between a 160/70 and 170/60 are pretty small. The PR3s I run are the same tires that fit an ST1300 - the front is an exact match , the rear is 170/60 versus 160/70. But then I don't ride much either ... ;-)

160/60ZR17 on mine.

Have to allow a little extra for the speedo difference.
Rely on the GPS reading when I'm out on the road...

Kevin_56 · Dec 29, 2013

Outlaws said:
Have to allow a little extra for the speedo difference.

Is not the ST1100 speedo front wheel, cable driven. If so, a small rear tire should not effect the speedo, like the 1300.

Uncle Phil · Dec 29, 2013

The next you know we'll be talking about oil and factory air in the tires ... ;-)

Doodaa · Dec 29, 2013

Uncle Phil said:
The next you know we'll be talking about oil and factory air in the tires ... ;-)

Got a spare can of factory air, can't seem to locate any around here

Outlaws · Dec 29, 2013

Kevin_56 said:
Is not the ST1100 speedo front wheel, cable driven. If so, a small rear tire should not effect the speedo, like the 1300.

Right you are...

Busted, was thinking of one of the other bikes when I typed that.

Nitrogen in all of mine, trouble maker that I am.

Uncle Phil · Dec 29, 2013

Nitrogen? You outlaw, you ...

broc11 · Dec 30, 2013

Uncle Phil said:
Looks like on the 170/60 vs 160/70 you gain .39 mm in width and lose .39 mm in sidewall height which is .015 inch difference. On the 160/60 vs 160/70, width is the same but you lose .63 mm in sidewall height which is .024 inch difference.

I think you lose 10mm in sidewall height and gain 10 mm in width Phil? maybe I'm wrong,has been known to happen LOL.

Uncle Phil · Dec 30, 2013

Broc - Here's what I saw -

170/60-17 160/70-17 Difference
Diameter inches (mm) 25.03 (635.8) 25.82 (655.8) 0.79 (20) 3.1%
Width inches (mm) 6.69 (170) 6.3 (160) -0.39 (-10) -5.9%
Circum. inches (mm) 78.64 (1997.42) 81.11 (2060.26) 2.47 (62.83) 3.1%
Sidewall Height inches (mm) 4.02 (102) 4.41 (112) 0.39 (10) 9.8%
Revolutions per mile (km) 805.71 (500.64) 781.14 (485.38) -24.57 (-15.27) -3%

That's assuming their measurements and calculations are correct. But you are right as I got my MM and Inches crossed up! But I said it on the internet so it's got to be right ... ;-) If they are correct, then the 170/60 vs 160/70 difference is very little in reality and experience has shown me not very noticeable after 4,000+ miles of some pretty hard cooking on some major technical stuff (and the ABSII has not uttered a peep).

The PR3s have excellent grip in wet and dry and the sidestand lean and center stand deployment has not been problematic for me at all.

Bigmak96 · Dec 30, 2013

Uncle Phil said:
(and the ABSII has not uttered a peep).

The ABSII system will tolerate a pretty big difference in comparative tire size before it acts up. At least that's what I found when I ran a CT on the ABSII.
I agree with U.P. 100%,,"to each their own". I do feel however that the "specifications" they put in the book are merely the tires they personally had experience with, and they are not willing to imply others will work without issue. That does not say to me that all others are not going to work, and work well while being just as safe as the narrow batch of tires the tested. We couldn't expect them to test all tires that would fit the wheel.

Outlaws · Jan 1, 2014

Uncle Phil said:
Broc - Here's what I saw -

170/60-17 160/70-17 Difference
Diameter inches (mm) 25.03 (635.8) 25.82 (655.8) 0.79 (20) 3.1%
Width inches (mm) 6.69 (170) 6.3 (160) -0.39 (-10) -5.9%
Circum. inches (mm) 78.64 (1997.42) 81.11 (2060.26) 2.47 (62.83) 3.1%
Sidewall Height inches (mm) 4.02 (102) 4.41 (112) 0.39 (10) 9.8%
Revolutions per mile (km) 805.71 (500.64) 781.14 (485.38) -24.57 (-15.27) -3%

That's assuming their measurements and calculations are correct. But you are right as I got my MM and Inches crossed up! But I said it on the internet so it's got to be right ... ;-) If they are correct, then the 170/60 vs 160/70 difference is very little in reality and experience has shown me not very noticeable after 4,000+ miles of some pretty hard cooking on some major technical stuff (and the ABSII has not uttered a peep). The PR3s have excellent grip in wet and dry and the sidestand lean and center stand deployment has not been problematic for me at all.

Learned something new and have been convinced.

My next rear will be a MICHELIN PILOT ROAD 3 170/60ZR17

Love these forums and appreciate all who contribute.

Happy New Year!

Donald St 2012 · Jan 1, 2014

I was looking for new tires......
Thank for helping me choose the Michelin Pilot Road 3

JPKalishek · Jan 1, 2014

I ran the 150/70 rear on my ST1100 as the tires ran real close to the swingarm on the TwoTone. It runs no chicken strip if you ride like I do, and I got 9300 miles from it rotationally it is closer than the 160/60.. I have had a 160/60 on the same bike (The PR2s it had when I bought it) and it rode fine, but when I ran the same size in a Shinko it swam like a fish, so I moved them over to the Nekkid one (it rides fine there) went to the 150/70 705 rear Kenda front (work great in winter, too heavy and overheated in summer), then the PR3s and currently I have the stock sizes in Metzlers on it.
I have a bearing set to put in the rear and will try for getting a hair more clearance (the other wheel gives more than enough space) so I might can try the 170/60 PR4 GT. I ran those sizes on the other bike twice before with no issues, well, the Avon front would shake its head in certain situations, but I avoid them after Raven's adventure in Roswell.

Michelin PR3 on ST1100 Rear - smaller size OK?

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