Michelin Tires

[Vard]

I am purchasing a 1992 st1100. It has an almost new Michelin on the rear but the sizing quoted to me by the owner seems out of line with sizing I see on this forum. the rear ties is a 160/60 ZR17 when other information seems to be that the tire is a 160/70. Is this a misread by the owner or is this a good tire for the bike. I'd like to know as I want to match the front tire.

Thanks,
Vard

 

[Superzuki]

Run it. That's only 10 mm narrower, when it's time to replace it use the other size. I doubt you'll notice a difference.

 

[Bush]

You can use some "off" sizes on your ST, such as that 160/60, although, you might find the bike is harder to centre stand than with the proper sized tire. The reason off sizes are used by some 1100 owners is because some manufacturers do not make the size that OEM calls for. Michelin and Bridgestone don't. Also, on the front wheel, the standard is a 110/80-18 and you can run a 120/70 instead, but that will cause your speedo to read about 10 kmh too fast.

I see you are in Gravenhurst. Would that be Ontario Canada? If so, you may want to check out Canada's Motorcycle web site and take a look at the Metzeler Z6 Roadtec. They still make the proper sizes for our 1100's.

 

[Andrew Shadow]

only 10 mm narrower

Are they not the same width but just a little smaller diameter?
From memory on how the sizing works a 160/60 tire has a 160 MM wide tread and is 96 MM tall (60% of the 160 MM width). A 160/70 tire also has a 160 MM wide tread and is 112 MM tall (70% of the 160 MM width). The 160/60 is a little smaller diameter tire (16 MM on the radius or 32 MM, {1 1/4 inches} overall diameter) which will affect your RPM's, gas mileage and speedo/odometer by a rather insignificant amount but other than that I don't think that you need to be overly concerned about it. If it were me I would run it until it is worn and then install the correct size.

 

[JPKalishek]

I prefer to go the 150/70 route when a off size is needed(10 mm narrower), the 160/60 (aprox. the same width but far shorter) is a bit buzzy and mileage suffers (especially in Texas where even back roads are 70-75 mph limits) 150/70 also is a tad taller than 170/60, and one of my bikes (the Two Tone) would rub if I run its rim with that size, the Black fits one fine, though ymmv. Several of the preferred tires come in GT weight spec with the 170/60 size for the ST1300 so if it fits, you might want that, but I'd wear that one out before springing for a new rubber band. With a 150/70 Michelin PR3, I used the tire right to the edge and that touched the pegs to the ground. The Shinko 705 I run is slightly taller (taller than some 170/60 street tires when new) so I use less and touch the pegs less often.

 

[Vard]

Thanks for the info regarding off-size tires. Since the riding style will be very different I didn't want surprises with the tires. Since the rear tire is new I'll match the front and then decide later whether to return to OEM sizes. Good to know about the change in speedo - don't need any speeding tickets.

Great forum,
Vard

 

[Andrew Shadow]

don't need any speeding tickets.

The speedometer will indicate about 3 MPH faster at 60 MPH so not much to worry about- well within the normal inaccuracies of the speedos anyway.

 

[Bush]

The speedometer will indicate about 3 MPH faster at 60 MPH so not much to worry about- well within the normal inaccuracies of the speedos anyway.

We are talking about a ST1100 here, not a 1300. The OP didn't say whether he was in Ontario, or not, so what I quoted him about the 10 KPH difference applies to the front tire size when using a 120/70 -18 size and not the standard 110/80 -18.

And just to clear that up for the OP - that means if you see 100 KPH on the speedo you are really doing 90 KPH, so even less chance of a speeding ticket.

 

[Vard]

Thanks for clearing that up Bush. As you can see having tires different than OEM is totally new for me - never realized that the speedo would be slower. Also, as for KPH or MPH I have a different situation. I am in Canada (Gravenhurst Ontario) so our speed limits are in KPH but the bike I purchased originally came from the states so the speedo is in MPH. Another thing to get accustomed to.

Rick

 

[Andrew Shadow]

We are talking about a ST1100 here, not a 1300.

I realize that it is an 1100- I just wrote my reply poorly and wasn't very clear as to what I was referring to- my bad. You seem to have experience with off size tires. I would like to know if the below makes sense to you since I have only done it with one tire.

I went to a tire size calculator this morning out of curiosity and the actual difference in speedometer readings between the two tire sizes according to the calculator is only 0.7 MPH (1.24 km/h). A speedometer reading of 60 mph (96.56 km/h) with a 120/70 18 tire would yield a speedometer reading of 60.77 mph (97.8 km/h) with a 110/80 18 tire. Does this make sense to you? Your experience was a 10 KPH difference. I saw a 3 MPH (5 km/h) difference when I did it as I stated earlier. I am just wondering why the different results. Is there that much of a difference in overall diameter of tires between different manufacturers to account for this discrepancy? Speedometers may be inaccurate but I would think that they would be fairly precise when comparing a before and after result against themselves. Just curious what your experience was.

https://www.tacomaworld.com/tirecalc?tires=120-70r18-110-80r18

 

[Grabcon]

I have run the 160/60/17 and the 110/70/18 and it cause more grief than anything. Side stand issues so parking is a real pain. Cornering, easier to scrape pegs and they only lasted 3000 miles. The sides of the rear wore out not the center. They were properly inflated. But at the time I want to say that we may have over loaded the bike. Two people with gear for several days.

For you geeks out here is a tire height calculator formula.

D=Rim Diameter in inches
A=Aspect Ratio...enter as decimal
S=Section Width

Formula D+[(2*A*S)/25.4]=Tire Height

Here are a couple of examples

160/70/17 = 25.82 inches tall ............... 17+[2*0.7*160)/25.4]

160/60/17 = 24.56 inches tall................ 17+[2*0.6*160)/25.4]

 

[Bush]

I realize that it is an 1100- I just wrote my reply poorly and wasn't very clear as to what I was referring to- my bad. You seem to have experience with off size tires. I would like to know if the below makes sense to you since I have only done it with one tire.

I went to a tire size calculator this morning out of curiosity and the actual difference in speedometer readings between the two tire sizes according to the calculator is only 0.7 MPH (1.24 km/h). A speedometer reading of 60 mph (96.56 km/h) with a 120/70 18 tire would yield a speedometer reading of 60.77 mph (97.8 km/h) with a 110/80 18 tire. Does this make sense to you? Your experience was a 10 KPH difference. I saw a 3 MPH (5 km/h) difference when I did it as I stated earlier. I am just wondering why the different results. Is there that much of a difference in overall diameter of tires between different manufacturers to account for this discrepancy? Speedometers may be inaccurate but I would think that they would be fairly precise when comparing a before and after result against themselves. Just curious what your experience was.

https://www.tacomaworld.com/tirecalc?tires=120-70r18-110-80r18

Without getting into the math of this, since math was never a strong suit of mine anyway, my conclusions have been gained by comparing a 120 front to a 110 front while riding the bike past one of those roadside, post mounted, radar speed checkers, the type that warn you of excessive speed, without any consequences if you ignore them. There are a few not far from where I live, so I have done speedo checks often.

I have used the different fronts (Metzelers) a few times over the years, depending on availability of the 110 size, which I prefer and I have consistently seen a 10 kph difference between what my speedo says and what the radar reader says, with the 120 size on. With a 110, my speedo is very close to the radar, or as close as can be said to be observed without a larger, more incremental gauge. So, in passing one of these things, it is not an exact science, as I look and glance at both radar and speedo quickly to compare, so it may be that the difference is actually 8 kph, or 7, or 9. It is rather hard to tell, at speed on the road, but it has appeared, to me, to be about a 10 kph difference.

Another consideration that I would think could make a difference in comparing readings would be the amount of wear on the two comparing tires.

Since I am currently running a 120 Bridgestone BT-023 on the front (came with the bike bought last summer), I will do another comparo with the 110 Metzeler that I have in stock, once I wear out the BS.

 

[STripper]

never realized that the speedo would be slower.

The speedometer will indicate a speed that is faster than actual speed.

 

[Bush]

Since we all love to compare tire mileages too I thought I would report, for the OP's benefit in his future tire purchases, that the BT-023 rear (a 160/60-17 since Bridgestone doesn't make the 160/70), only went a measly 15,000 kms, whereas every Metzeler Z4 and Z6 I have had, over 20 years on my previous 1100 and in the proper size, went at least 25,000 kms.


And I replace mine just at, or very near to the wear bar point.

 

[Bush]

The speedometer will indicate a speed that is faster than actual speed.

You should have added "regardless of what tire you use", since manufacturer error will always err on the side of avoiding an under actual speed reading.

 

[DeanR]

the BT-023 rear (a 160/60-17 since Bridgestone doesn't make the 160/70)

I'm on my second 160/70 BT023 and have a 160/70 T30 ready.

 

[Bush]

I'm on my second 160/70 BT023 and have a 160/70 T30 ready.

Thank you Dean. i stand corrected on the sizing thing. Having never bought the BS tires myself, I assumed that since the previous owner had a 160/60 size mounted, that the proper size was not available. He had a Honda dealer do the work, so WHY would the dealer order the wrong size?? Probably one he had in stock and passed it off as okay to use. Another reason to bolster my opinion that many, if not all dealers are not to be trusted with my machine.

Still don't like the mileage that BS gave though.

 

[STripper]

You should have added "regardless of what tire you use", since manufacturer error will always err on the side of avoiding an under actual speed reading.

Fair enough. My use of the word "actual" was intended to mean the nominal speed reading with OEM tires. When fitted with OEM tires, my speedometer reads ~7% greater than my GPS.

 

[Bush]

Did a ride past two radar readers today, just to add my findings here. Not that it is a big deal, but for the enquiring minds, it might be interesting. This is with a 2/3 worn BT-023 120/70-18 on the front.

The first radar I passed twice, trying to maintain a steady 50 kph and on a slight downhill incline. One radar reading was 43 kph and the second was 42 kph - so 7 and 8 kph fast on the speedo. The other radar clocked me at 60 kph while I was doing as best I could to maintain 70 kph, again, a bit of a downhill road. Of course, this doesn't say anything about possible built in speedo error, so, later this year once I have a 110/80 on the front, I'll compare again.

 

[Brant]

Since we all love to compare tire mileages too I thought I would report, for the OP's benefit in his future tire purchases, that the BT-023 rear (a 160/60-17 since Bridgestone doesn't make the 160/70), only went a measly 15,000 kms, whereas every Metzeler Z4 and Z6 I have had, over 20 years on my previous 1100 and in the proper size, went at least 25,000 kms.


And I replace mine just at, or very near to the wear bar point.

No offense, but beg to differ. My 92 is setting on a 160/70-17 BT-23, with 2K on it(them.

Just saw the later post........disregard.