Front Tire size - 120/60/17 instead of 120/70/17

[vsark]

Just noticed today that I have a screw stuck in my front tire, though there is no drop in pressure. I am afraid if I pull it out, the tire will go flat.

Anyways, I have to change the front tire now. I have the stock Dunlop Sportmax D220F ST 120/70 ZR17. I a wondering if there will be a proble if I put on a 120/60 ZR17 instead of the same brand/tread pattern?

Also wondering if these tires can be repaired once the screw is out.

thx

 

[hoston1765]

Too bad about the tire. The front and rear tire work together in flex, traction and profile. All of these will be different with a mis-matched set and the front tire will be doing one thing while the rear is doing something else. For example, if the rear tire has a pointed profile and your front tire a flatter profile the rear will lean more readily than the front and flexing (via different bias designs) at a different rate, mixing tires is not safe. I read once where badly mismatched tires can set up a resonance wobble at certain speeds. Yamaha did a lot of testing to come up with recommended tire sizes and inflation pressures. Your aspect ratio is different at 60 so you will have a different profile and sidewall flex from the rear tire. It will be guesswork as to the correct pressure. Plugged tires void the speed rating and no one can tell you accurately what the new safe speed will be. Your patch may hold at room temperature but on the road tires get much hotter, pressures go up and the forces of spinning add to the stress. Motorcycle tires have very small contact patches, imagine running over a pebble on the repair spot with 350 lbs of weight behind it. There is an old trick question: "How many molecules in a tire?". The answer is of course, one because in the vulcanizing process everything gets cross-linked. A puncture disrupts the integrity of the tire and no patch can duplicate the original structure, to say nothing of the possible damaged cords. New tires are expensive which is one reason I avoid the center of the lane, hope this helps. Good luck!

 

[RJ2112]

Just noticed today that I have a screw stuck in my front tire, though there is no drop in pressure. I am afraid if I pull it out, the tire will go flat.

Anyways, I have to change the front tire now. I have the stock Dunlop Sportmax D220F ST 120/70 ZR17. I a wondering if there will be a proble if I put on a 120/60 ZR17 instead of the same brand/tread pattern?

Also wondering if these tires can be repaired once the screw is out.

thx

I'm more liberal, when it comes to mix and match of tires. The difference between a 120/70 and a 120/60 is the height of the side wall with respect to the tire's width. The /60 will result in a slightly shorter outer wheel diameter, so the tire may steer quicker. It could affect the tire profile, as well, as the shorter sidewall will result in the tread pattern being slightly more 'peaked'.

But this is all theoretical..... as we don't know how close to the ideal the tire that is currently on your bike is, or how close the replacement is to it's ideal.

60% of 120 = 72
70% of 120 = 84

The outer wheel diameter would be reduced 12 mm providing both are exactly on their spec'd dimensions.

But..... what if the tires are simply within a 10% tolerance of the ideal? You could very easily have tires from different mfgs that are physically exactly the same size, but identified as different on the side wall. Note that in the example above, the 10% difference happens to be 12 mm, as well. The opposite is of course possible. A max differential, one being 10% low, and the other being 10% high, would result in significant difference.

Me personally.... I don't like plugs in front tires. A blow out on the front is a much bigger deal than losing the rear. Neither is fun; one is much more likely to be catastrophic.

Knowing a plugged tire is (in my opinion) an unacceptable risk, I rate a 'mix' of tire brands front to rear far more acceptable than a plugged 'like' brand.

Swap the tire, and take it easy until you know how it handles.

 

[vsark]

Thanks for all the useful info.

The /60 tire I am looking at is exacty the same tread pattern and brand as the /70. Only difference is the profile.

The problem is that Dunlop doesnt make the D220F any more so I will have to go with the new pattern (Dunlop Roadsmart) they have now, which is a new tread pattern, which means that now I have to change both front and rear tire.

I found a D220F on ebay but its a /60, so I am checking if that can work.

 

[RJ2112]

I have not ever experienced a handling issue I could attribute to tread pattern, as a result of mixing patterns.

If you have put XXXX miles on your tires and feel that the back is worn sufficiently to warrant replacement, do them as a pair. If not, just swap out the one that took the hazard, and be cautious until you are comfortable with any changes you may experience.

 

[jbwaterman84]

I put a 60 on my front when I did the r6 swap. Haven't had any problems with it in 3k miles, it does turn in faster which to me isn't a bad thing. I do have the same type on front and rear though

 

[vsark]

I put a 60 on my front when I did the r6 swap. Haven't had any problems with it in 3k miles, it does turn in faster which to me isn't a bad thing. I do have the same type on front and rear though

I am using 180/55-ZR17 on the rear. Is that what you are using with the /60 on the front?

 

[jbwaterman84]

I am using 180/55-ZR17 on the rear. Is that what you are using with the /60 on the front?

That's right, didnt see any need to change out the back to anything different.

 

[vsark]

Too bad about the tire. The front and rear tire work together in flex, traction and profile. All of these will be different with a mis-matched set and the front tire will be doing one thing while the rear is doing something else. For example, if the rear tire has a pointed profile and your front tire a flatter profile the rear will lean more readily than the front and flexing (via different bias designs) at a different rate, mixing tires is not safe. I read once where badly mismatched tires can set up a resonance wobble at certain speeds. Yamaha did a lot of testing to come up with recommended tire sizes and inflation pressures. Your aspect ratio is different at 60 so you will have a different profile and sidewall flex from the rear tire. It will be guesswork as to the correct pressure. Plugged tires void the speed rating and no one can tell you accurately what the new safe speed will be. Your patch may hold at room temperature but on the road tires get much hotter, pressures go up and the forces of spinning add to the stress. Motorcycle tires have very small contact patches, imagine running over a pebble on the repair spot with 350 lbs of weight behind it. There is an old trick question: "How many molecules in a tire?". The answer is of course, one because in the vulcanizing process everything gets cross-linked. A puncture disrupts the integrity of the tire and no patch can duplicate the original structure, to say nothing of the possible damaged cords. New tires are expensive which is one reason I avoid the center of the lane, hope this helps. Good luck!

when you say mis-matched set, do you mean mis-matched recommended sizes or patterns as well?