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Discussion Starter #1
I am about to do my spring maintenance on my 2000 RC51. I am changing the sprockets/chain, rear tire, spark plugs and checking the valve clearances. It has 16,8XX miles. As the title suggests, I am changing the gearing and rear tire size. I know the stock chain is 104 links. And I have read somewhere on the net that a stock length chain will work with -1/+2 gearing. But will it work with a 190/55 tire? Will I need to go with a 106 link chain? I found a sweet deal on an RK 104 link x-ring chain. I already have my sprockets (Renthal with the hard anodized rear). I also have the 190/55 tire, but I work at a tire shop and ordered it through there from one of our suppliers. So a return and exchange for a 190/50 would be no problem if that's what it would take to be able to use the 104 link chain. I have no complaints with the handling with the 50 series tire. Just saw alot of RC riders on the board switch to the 55. I can save myself around $120 if I can use the 104.
 

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I have that set-up. 15/42 & 190/55. My chain and sprocket are afam, so I don't know if the chain is the same length as the stock one was, but I'll count tommorow.
 

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I mounted my new Q2's today. 190/55/17. turns out I got about 3/16" clearance between tire and chain. Seems plenty adequate. And I counted 52 of the outer links, so I'm assuming that means 104 links. with the 15/42 gears, I have about 1" adjustment travel left to the back of the swingarm adjustment. Made me wonder, how would the bike handle differently if it were lengthend out?

I should add, I'm running a 520 chain.You didn't mention what size you have/or gonna get.
 

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Discussion Starter #4
I'm running a 530 chain. But from my understanding of chain sizes, a 520 chain is 1/8 inch narrower than a 530. Link "length" is the same. If you have 52 outer links, that should be 104 total links. How much clearance do you have between the center of the tire and swingarm? My only concern was the tire rubbing the swingarm at speed. Because the tire will expand some in circumfrence with speed. I think that 8-10mm is the recommended space. But if you have run this setup with no rubbing issues already, then I should be okay with 104.
 

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Ok, I thought about that too, clearance getting tighter under certain loads, like you described. So I was checking my swingarm clearance too. I have the same amount of clearance Just about 3/16". How many ml is that? I noticed that when I was measuring the chain to tire clearance.

Also, these measurements may change a little for a different brand of tire. With a 530 chain, you're going to have 1/8" clearance at the most. Maybe a hair less...

I had a 180/55 sportmax on there before. Some time ago in a couple previous posts, I said I had 190's. I didn't look at them close enough, i was wrong. So this is a new size for me, and although they're mounted, I haven't ridden them yet.
 

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Discussion Starter #6
3/16" is around 4.75mm. Seems a little tight. I may go ahead and order the 104 link chain. Put the chain & sprockets on with my old tire still on and measure the clearance with the 190/50. Or go ahead and mount the new sprockets with the stock chain now and measure. I know I would like to have a little more clearance than that between the center of the tread and the swingarm. Running Michelin Pilot Powers.
 

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My bike came with that 520 setup already on it. And I could tell it was pretty new cause wear was nil. But sounds like you already got your gears? If not, consider a high quality 520 set. A few months ago I searched it on this forum and got lots of info.
Also, in a couple hundred miles of riding my RC since I got it done, I might try a 41 sprocket and add a link. I'd like just a little more kick, at least in the present stock form.

I just eyeballed clearance of middle of tire to swingarm. I need to re-check that. You said 8-10 mm clearance. Gonna be close for my bike.
 

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Discussion Starter #8
Decided to stick with the 190/50 tire. I have no complaints on the handling with it. Plus with the price I got on the 104 link RK X-ring chain, I couldn't pass it up. Plus didn't like the idea of adding links to the chain. One master link seems like enough. Maybe next time, I'll try the 190/55.
 

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I checked my swingarm/tire clearance today. Using an allen wrench like a feeler gauge, I can pass a 6mm allen wrench thru, but not an 8 mm. If I add 2 more links to my chain, clearance would no longer be an issue. 106 link chain, and a long wheelbase. hmmm...

Any other SP1's out there with 15/42 sprocket and a 190/55 tire on stock swingarm? 104 links or 106?
 

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Did you check actual specs for the difference in diameter of 190/50 vs. 190/55? I'm thinking they're the same height, and circumfrence. Cause technically, 190 is the height of the tire, from the bead to the crown of the tread. 50 or 55 only designates sidewall depth. 50% as wide as it is tall, or 55% wide as tall. In theory, both tires should have the same swingarm clearance.
 

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Discussion Starter #11
The 190 is the section width of the tire. Then the 50 or 55 is the aspect ratio. Sidewall height to section width. So the 50 series tire will be shorter and generally slightly wider. Michelin's website is useless in this regard, because it contains no tire data or specs. But from the other tire manufacturer websites I checked, the difference is 16-18 mm. Which should give me plenty of clearance. But every tire manufacturer is different and hopefully Michelin doesn't make their tires oversized.
 

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Did you check actual specs for the difference in diameter of 190/50 vs. 190/55? I'm thinking they're the same height, and circumfrence. Cause technically, 190 is the height of the tire, from the bead to the crown of the tread. 50 or 55 only designates sidewall depth. 50% as wide as it is tall, or 55% wide as tall. In theory, both tires should have the same swingarm clearance.
I'm afraid you have this wrong.
The first number is the section width of the tire (190) in millimeters.
the second number is called the aspect ratio and is the percentage of section width that makes up the height from the wheel to the outer circumference.
50 would be 45mm 55 would be 49.5mm
The third I'm sure you are aware is the diameter of the wheel.
So the standard 190/50r17 would be 24.48in in diameter while the 190/55r17 would be 25.23in in diameter. About 3% taller.
Hope this helps.
 

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Following up on this thread. To summerize this is my setup. I have the sp1 swingarm, a Dunlop Q2 190/55-17, 15/42 520 chain, with 104 links,. My clearance between tire and swingarm was only 5-6 mm. Cold tire, 38psi. Brand new tire and tire size for me, so I was realy careful, but I rode for about 100 mi. yesterday. I took it pretty easy the first 50 mi., then started getting a little deeper in turns and accelerating out of them. I pulled over several times and checked for signs of rubbing and there are none. The fastest I ever peaked was only 95-100.

I still think I better add 2 links tom my chain and go 106. My axle is within the front 10% of the adjustment range, so I'm thinking plenty of room for that extra 2 links? Cause the axle only slides back the distance of one link, is that right?
 
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