Need new tires = NEED HELP

I have read just about every thread on tires. I have a few questions that still remain. I have a 1991 ST1100.
Stock tire
F 110/80/18
R 160/70/17
I know everyone knows that and it is posted over and over, but i am having a difficult time finding a Matched set of tires.
I also have read that for the rear it is ok to go 170/60/17, but there is not a tire made that works front and rear.
Looking at Bstone T30 GT Rear = 170/60/17, but what front tire? Bstone T30 None GT? are they 2 different of tires to run together?
Mich. PR4 ... same story, what front tire ?

Can I go 120/70/18 on the front to run PR4 or T30 GT?
Is there a big difference in the T30 GT and standard T30 ( which comes in stock sizes )
Sorry for so many questions. 1st year with the bike. Love riding again.

No need for a matched set... people run mixed all the time. Tires are like oil... opinions vary wildly. FWIW, I'm running a Bridgestone Exedra G547 on the front and a Michelin Commander II on the rear of my '01 ST11. I got the Exedra at a good price and bought the Commander for long life. I run beads in both.

I also have a '91. For the better part of 21 years and 178K I have been very happy with matched sets of tires that Honda spec'd for our STs: the Bridgestone Exedra G547/G548s. I get mine from my Honda dealer. Honda part numbers. The Honda warehouse is 4 miles away and I've never had a Honda stocked tire that was more than a year old. I recommend them to you... Good handling throughout the life of the tires. I get ~10K on a rear and twice that on a front. YMMV FWIW

Edit: for ST1100 related questions/threads poSTed in forums other than the ST1100 specific ones, it's always a good idea (and courteous) to put 'ST1100' in the subject line.

John
via iPhone 6

I've run quite a variety of tires over the years between my three ST1100s. You will be fine with the 170/60 on the rears - I've used them on my 2 ABSII models and my standard. I have never done it, but the 120 will fit on the 110 rims without a problem. Since my ABSIIs already take the 120 width, I put an 120 ABSII rim on my standard so I have the same across the board and the same size takeoffs. I have no clearance issues at all with the 120 on the standard. My rule of thumb - bias for mileage, radials for handling. I'm running the BT020 bias BMW model on the rears of two of my STs now with the BT30GT radial on the front. Then I've got one of them with BT30GTs front and rear. Pull the trigger on what you want and go ride!

Thanks for the help. I called a couple dealers and they gave me warnings " oh, you can't run that size and You can't have different tires, if the tread is even a little different, you will have wobble etc... etc.... Thanks again. It was my first post, i will be sure to add type of bike.

John, my 91 only has 34K on it. I am glad to hear i have a long ways to go. I have wanted this bike for 25 years, and i found it.

Not gettin' into tire choice, there is MANY in set pairs for our ole' 11's still available, bias and radial.........MotorcycleSuperStore IS your friend, availability AND cost. Not a supplier left to beat their prices. RockyMountainATV comes close, but option availability, they can'rt even hold a candle to MSS..........2-3days FREE shipping for both the above mentioned, and alot others on-line. Any of your local dealers can no longer touch these prices, as they don't order in 'bulk' large numbers. Been that way for 8+yrs. now.
BTW, stick to the original sizes on these ole' 11's.

I just put on a 130/70zr18 exedra max on the front of my 97st1100 and love it and running a t30 in the rear -stay away from the 170/60 for the rear it is smaller and will increase rpm's a bit at hi-way speeds

No problems running different sizes and different brands on all of the bikes that I have owned.

I have a 1991 and I always run match tires. I am on my third set of t30s and running 110/70/18 and 160/70/17. Not the GT. I have been get around 9k miles out of them.

Al st1100 said:

I just put on a 130/70zr18 exedra max on the front of my 97st1100 and love it and running a t30 in the rear -stay away from the 170/60 for the rear it is smaller and will increase rpm's a bit at hi-way speeds

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Really? I've run several of them and have not noticed the difference to be significant at all. YEMV. Good site to reference for the size differences -

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

It appears the circumference difference is .1 inches, the sidewall height difference is .02 inches. ;-)

Al st1100 said:

stay away from the 170/60 for the rear it is smaller and will increase rpm's a bit at hi-way speeds

Click to expand...

On an 1100 running the 170/60/17 may also cause issues with the kick stand. The 170/60/17 is 3/4" shorter in height than a 160/70/17.

John OoSTerhuis said:

...Bridgestone Exedra G547/G548s...

Click to expand...

Another satisfied long time user of the Exedras, despite being being a bias-ply construct (or maybe just because of that...) is that the combo with the least troubles on a ST1100 model/year with the narrow, 3" front rim...
Superior quality, smooth & comfy ride, excellent handling, brilliantly precise steering (the bike is literally "carving"), exceptional mileage...
They do need to be broken in though, the practice of taking it easy for the first 300 miles shall be maintained (a brief speciale on a piece of unpaved road shortens this...), but once roughened just great, all situation, all weather tires...

Grabcon said:

On an 1100 running the 170/60/17 may also cause issues with the kick stand. The 170/60/17 is 3/4" shorter in height than a 160/70/17.

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Did you measure the 3/4" (.75")? Just curious because it appears the circumference difference is .1 inches, the sidewall height difference is .02 inches if the calculator is correct. I've not had any sidestand issues at all with the 170/60 and I have ran several of them on my ST1100s. I did have issues with the 160/60 rear. Look at this calculator and see if I've got my data wrong -

https://www.tacomaworld.com/tirecalc...0r17-170-60r17

Another thumbs up for the Bridgestone Exedras.

wgelhar said:

.... John, my 91 only has 34K on it. I am glad to hear i have a long ways to go. I have wanted this bike for 25 years, and i found it.

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Congratulations, [care to share a first name with us, pls?]

Is your 1991 a Sparkling Silver Metallic (SSMST) or a black one?

John [Keper of the unofficial SSMST RegiSTry]

Uncle Phil said:

Did you measure the 3/4" (.75")? Just curious because it appears the circumference difference is .1 inches

Click to expand...

I have a calculator in a spreadsheet that came up with the numbers. Formula: Diameter in Inches = Rim Diam Inches + [ (2 x Aspect Ratio x Section Width) / 25.4]

160/70/17 is 25.82 diameter

170/60/17 is 25.03 diameter

Grabcon said:

I have a calculator in a spreadsheet that came up with the numbers. Formula: Diameter in Inches = Rim Diam Inches + [ (2 x Aspect Ratio x Section Width) / 25.4]

160/70/17 is 25.82 diameter

170/60/17 is 25.03 diameter

Click to expand...

I'll have to take an 'actual' measurement since I've got both sizes on the back of my ST1100s - the 160/60 on two and the 170/60 on another. That should be interesting!

I forgot to add the when doing the calculation make sure the aspect ratio is a decimal value.

The other thing I do not know is this the a deflated value or inflated value.

I would assume (and that is an 'assumption' -) that the calculator online takes all of that into consideration since you can 'overlay' one tire over the other one to see a 'visual'. It is a pretty nice tool to have bookmarked if the tire size question pops up. My 'experience' with running the difference tire sizes tends to line up the dimensional differences it shows. As I said, the sidestand/centerstand issue is just not there on any three of my ST1100s when I run the 170/60 versus the 160/70, but YEMV. BTW, I was recently at FerrySToc where the parking area is sloped gravel (high in the middle) and I had no problem at all using the sidestand - even packing up which including lashing a heavy duffel bag on the backseat.

Phil, My comment on the side stand was a cautionary statement. It is fairly well known that if you run a 160/60/17 there will be issues as the is a significant difference in tire height. The 3/4" difference here may not impact as you are stating. But you are right I think all of those considering a tire size change should look at tire height and other things for overall impact, i.g. side stand issues, center stand, cornering, loaded and loaded with a pillion, etc.