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OK, I know there are many threads on tyre sizes and I have read them. I specifically wanted to ask the guys who have gone to a larger rear tyre circumference on a 900, either 200/70 or 170/80, about effects on acceleration. I know there will be some, but how noticeable is it? Did it become an issue for anyone? Did anyone change back to stock? I noticed from the Gear Commander site that the drop in rpm is bigger in the lower gears. Does it feel like this is where most acceleration is lost? don't want to change pulleys as I feel that would be a waste of money if I don't like the change. Thanks in advance and sorry if I'm going over old ground...
 

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OK, I know there are many threads on tyre sizes and I have read them. I specifically wanted to ask the guys who have gone to a larger rear tyre circumference on a 900, either 200/70 or 170/80, about effects on acceleration. I know there will be some, but how noticeable is it? Did it become an issue for anyone? Did anyone change back to stock? I noticed from the Gear Commander site that the drop in rpm is bigger in the lower gears. Does it feel like this is where most acceleration is lost? don't want to change pulleys as I feel that would be a waste of money if I don't like the change. Thanks in advance and sorry if I'm going over old ground...
75% of my riding is either 2 up or pulling a trailer, around town i use 1 thru 3 gears vs 1 thru 4 before the change .. much nicer to ride, not a noticable difference in accelaration. ... you can still smoke any cager from the lights. I would never go back to the stock size. Touring is even better at speed ...btw ...... loaded, 2 up with the trailer iam 1260 lbs rolling down the road and thru 13000 ft mountains. ... go for it.
 

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i put a 200/70/15 metzeler tire on mine with a barons big air kit/dynojet 5 power comander and cobra pipes and the accleration is great /crisp/and very responsive
 

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I would be hard pressed to believe anyone who said they noticed a difference in acceleration after changing from the 180/70-15 to the 200/70-15. It's all in the mind!
 

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I didn't notice an acceleration difference; I noticed that I had to change my take off a little. I had to add a little more throttle and a touch more clutch slip is all compared to what I was doing with the stock rear size.

To me, I am able to attain more speed in each gear. With the stocker, I was shifting every 10 mph or so, and I was in 5th at 50 mph. To me, this is where the bike was comfortable. 70 mph felt like she was reving too hard (slight vibration).

About 2500 miles later, rear tire change. After figuring out why something seemed wrong on take off compared to what I was used to, I now shift into 5th between 60 mph and 65 mph, and she will run 80 mph before that same vibration creeps in.

Seems the gear spread is better than before; I can downshift to 4th to pass on a rural two-laner and not feel like I am winding out the bike too hard, yet acceleration in top gear is still as strong as with the stocker. Also, taking two-lane mountain passes two-up allows 2nd to be used a lot more than before. The 170 was cheaper than the 200 and I noticed no degradation in handling; the Kendas have 4000 miles on them and still handle great and look a lot better than the D404s at the same mileage.

Two downsides I have noticed are: top speed with the stocker, 105 mph, with the 170, 98 mph; pulling three local superslab passes now require 4th two-up, where before they didn't, but no change solo.

I'm happy with just the tire change. I have no desire at this time to go to the 200 or change pulleys, nor do I whine like I used to about needing a 6th gear. I don't find myself checking all the time for 6th like I did with the stocker.
 

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King43, What model Kenda did you go to? I've been considering trying the K671 Cruiser. It's got a similar tread pattern to my ME880 that I'll be replacing soon. I'll be interested in the final mileage you get with the Kenda. I'm at 15k miles on my Metzler right now. I paid $210 for that; mounted and balanced on the wheel. I'm wondering if the miles/dollar are better for the Kenda. My MC budget is fading fast this year and I'd like to spend less on the tire this time if it makes sense.
 

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Plus one . ..... I find it hard to believe that you could not notice the difference.
Sorry, just saw this. Frankly, I find it hard to believe you could notice the difference. I would guess in a blind test that most people couldn't tell the difference. For instance, while not knowing all the science, I know that there is a 10% difference in the circumference of the two tires. If that were to translate all the way through and a bike with the 180 did 0 to 60 in 15 seconds then the 200 could possibly do it in 13.5 seconds if it could maintain the torque (even though I'm guessing it might lose a slight bit). So, all in all, we're talking about 14 versus 15 seconds. Not a whole lot of difference in my mind.

BTW, this is just a little diversion to get my mind off the heat:).
 

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SteveJB, I use the Kenda Kruz K673; I like the tread pattern better than the Cruiser. Paid $220 for both installed (have a buddy who is a really good bike mechanic who was able to mount them for $60). I only have 4000 or so miles on them, so it might be a while before I find how long they last. This was one of the least expensive tires I could find, so on the short MC budget myself I gave them a try. I had used Kenda before in 1990 on my CB550 and they worked just fine.
 

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Sorry, just saw this. Frankly, I find it hard to believe you could notice the difference. I would guess in a blind test that most people couldn't tell the difference. For instance, while not knowing all the science, I know that there is a 10% difference in the circumference of the two tires. If that were to translate all the way through and a bike with the 180 did 0 to 60 in 15 seconds then the 200 could possibly do it in 13.5 seconds if it could maintain the torque (even though I'm guessing it might lose a slight bit). So, all in all, we're talking about 14 versus 15 seconds. Not a whole lot of difference in my mind.

BTW, this is just a little diversion to get my mind off the heat:).
Some people can tell the difference between Coke and Pepsi with the first sip. Some can hear one bad note in a guitar riff.

Let's say I have a highly calibrated ass-dyno. ;)

I have a need to be the first one off the line at a stop light. Vehicle doesn't matter. After 8600 miles on the stockers, I had a solid feel for the acceleration. The INSTANT the tires were changed to the 200/70, I noticed the difference. And yes, it is slight, but it's there. With our little engines, it's noticeable. To me.

I prefer not to go into the physics, but simply put, as the tire diameter increases, so does the amount of energy it takes to rotate that tire. The more energy it takes to rotate, the more time it takes to build that amount of energy. Thus, slower acceleration. Again, by a fraction.

EDIT: The guys I know that drag race their street cars put smaller diameter tires on for the strip to get a little extra ooomph out of the hole. Just sayin'.
 

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Sorry, just saw this. Frankly, I find it hard to believe you could notice the difference. I would guess in a blind test that most people couldn't tell the difference. For instance, while not knowing all the science, I know that there is a 10% difference in the circumference of the two tires. If that were to translate all the way through and a bike with the 180 did 0 to 60 in 15 seconds then the 200 could possibly do it in 13.5 seconds if it could maintain the torque (even though I'm guessing it might lose a slight bit). So, all in all, we're talking about 14 versus 15 seconds. Not a whole lot of difference in my mind.

BTW, this is just a little diversion to get my mind off the heat:).
I don't believe we are referring to acceleration., more the difference in rpm, tractorbility.,performance, shift pattens, less vibration, and overall ride performance. While i do not believe it increases speed performance, i think the OP was whether it was detrimental to it.
 

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For someone new, looking at tires. What do the numbers mean? 200/70/15
Guess the bigger the number the larger the reference is.
 

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For someone new, looking at tires. What do the numbers mean? 200/70/15
Guess the bigger the number the larger the reference is.
200/70-15

First number, 200, is tire width in millimeters. So this is an actual measurement.
Second number, 70, is tire side wall height as a % of tire width. So, 70% of 200mm. This is a calculated measurement.
15 is the rim diameter in inches.
 

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Ok, I need new tires and you guys convinced me. So which tire should we buy:
200/70-15 or 170/80-15?

Do you need to change the inner tube also?
 
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