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I was told by the dealer that the stock sizes are

Front - 130 70 17
Rear - 170 60 17


I currently run (but need changing)

Front - 130-70-17
Rear - 180-55-17

The dealer said the bigger tire on the rear would "slow me down" .... I am not a mechanic, but I am curious how a wider tire would slow me down? Or was the parts person just handing me a line?
 

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Yes, these are the stock sizes:
Front - 130 70 17
Rear - 170 60 17

Wider rear changes handling.
Do a search on tires sizes, you can read until the end of time.

I'm running:
Front - 120-70-17
Rear - 180-55-17

Perfect for me, wouldn't go with anything else.
 

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The dealer said the bigger tire on the rear would "slow me down" .... I am not a mechanic, but I am curious how a wider tire would slow me down? Or was the parts person just handing me a line?
I'm running 200/55/17 rear and stock front.
I'm definitely not slowed down... :glassesti
 

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180/55-17
and
120/70-17

I reduced the diameters the same front and back and went wider on the back. So me likey. ;)
 

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A heavier tire will take more power to spin and a taller tire will effectively reduce your gear ratio thus slowing you down also. A 180/55 (height=99mm)and a 170/60 (height=102mm) are quite close to the same height. Technically the 180 is a bit smaller so would give you a greater ratio. Any difference would then come down to weight which you need to get from the manufacturer.

If he means in a turn then yes a wider tire makes it a bit tougher to turn. It wouldn't necessarily slow you down but would require more effort on your part to get an equal reaction from the bike. I went to a 180 and haven't noticed increased effort but it does take more input to hold a line in the curve.
 

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The dealer said the bigger tire on the rear would "slow me down" .... I am not a mechanic, but I am curious how a wider tire would slow me down? Or was the parts person just handing me a line?
The wider tire does weigh more (added weight can slow you down).
The wider tire does have more surface contact (more surface contact can equal more resistance to the ground, which can slow you down).

But with that being said - this is MINIMAL at best. You will not notice anything unless you are racing and a .01 of a second means the world to you.
 

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Currently running 130/180, will either go to 130/170, or 130/"the darkside" soon. I've got 12K miles on the front and 8K miles on the rear.

Jon
 

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130 70 17 on the front
200 55 17 on the rear

what he may have meant is that w/ certain sizes, it corrects the speedo error. He probably meant that it would slow you down in the twisties/curves. I have a 200 on the rear and still drag peg, and I noticed very little difference. Definitely has not slowed me down.
 

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No, changing the height of the tire changes your final drive ratio CAN slow you down. It all depends on the width and ratio. So it can slow you down OR speed you up depending on if you go up or down in height relative to stock while maintaining an equal weight.
 

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So it can slow you down OR speed you up depending on if you go up or down in height relative to stock while maintaining an equal weight.
Doesn't that also depend on if we're talking acceleration or top speed?
But as mentioned, either way it has to be a minimal change we're talking about...
 

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Doesn't that also depend on if we're talking acceleration or top speed?
But as mentioned, either way it has to be a minimal change we're talking about...
It would take more power before it would matter on a meanie. Yes you could achieve a greater top speed with a taller gear but it would be slower getting there and the meanie would run out of steam anyways due to wind drag and lack of power.

I was just trying to answer the "does it make me slower" question for 99.99% of us. I see no point in trying to achieve max speed on this bike and bouncing off the rev limiter. Call me old fashioned but I want to be on a crotch rocket if I'm going triple digits, not a cruiser. They have better brakes, lower weight, and greatly improved aerodynamics. You're also laying on the tank instead of being upright and having your chest act like a sail wanting to pull you out of your seat.

Even if you went to the drags the added torque of a lower ratio would be more beneficial than maybe squeezing out an extra 2-3mph of a higher max speed as it'd take you longer to get there. You want to hit the finish line as you hit the rev limiter to maximize the power.

Most of the tires we're talking about is only a +/-2% max difference, not a big deal. Thats why I said weight would likely be a bigger consideration. 1lb of unsprung weight is equal to 4lbs of sprung weight. So a 5lb heavier tire would be like you gaining 20lbs, it'd slow you down and make the suspension/brakes/engine work harder for the same level of performance
This link explains it:
http://en.wikipedia.org/wiki/Unsprung_mass
The 4 to 1 ratio is a drag/road racing factoid.
 

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180/55-17
and
120/70-17

I reduced the diameters the same front and back and went wider on the back. So me likey. ;)
Plus 1:agree: Conti road attacks good and sticky.
 

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http://www.ehow.com/facts_5750698_effect-wide-tires-motorcycle-handling_.html said:
What Effect Do Wide Tires Have on Motorcycle Handling?
By Richard Rowe, eHow Contributor

Motorcycles differ from cars in at least one crucial aspect: Cars ride on the flat portions of their tires, and motorcycles do not. Though some of the big-tire vs. small-tire arguments still apply, there are a few very important differences.

Wide Rear
A wide rear tire means more tread on the road, making the motorcycle want to push through turns instead of go around them. This can lead to a dangerous understeer condition.
Wide Front
Wider front tires will have the opposite effect of a wide rear, and can make the bike more responsive in the corners (oversteer). Caution is advised, however, since a wide front tire combined with a motorcycle's short wheelbase can make for a twitchy and dangerous ride.
Both Narrow
Some people prefer a narrower tire on both the front and back, because the tread of the tire is more pointed and handling is a little more crisp. This can, however, lead to serious instability problems at high speed.
Both Wide
The best solution is to go wide on both ends, since overall grip will be increased and the handling balance retained.
Manufacturer Recommendations
In general, a rim can only use tires that are ten millimeters wider or narrower than the stock tire. Exceeding this window can result in pinch flats, increased tire wear or blowouts.
Front: 140/75VR17
Rear: 195/40R17 DS
 

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The parts guy was handing you a lie, because he didn't know. When I had my M109, it came stock with a 240/40R18 rear. I swapped it out for a 260/40R18 Metz and it handled every bit as good as before. It is the arc in the tire that makes it handle, and the shorter sidewall. A 180/55R17 will fit the meanie rear rim perfectly and will handle superbly still, with better grip because of 5 mm more tread reaching out each side in the twisties. When my 170/60r17 wears out, it will get a dunnie sportmax 180 for sure. Good stiff sidewall, more beef, and superb handling. I will stake my 40 years of riding experience on it.
 
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