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Sportster Motorcycle Tires, Wheels, and Brakes Discuss issues with Sportster motorcycle tires, wheels and brakes.

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  #11  
Old 5th June 2012
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I've found that running @ 10% less than the max indicated on the sidewall works best for handling & longevity. I run a 110x90x19 on the front. I'm no longer a "racer", but I like the twisties & touring & I put 15-17k miles on my ride every year. I get 10-12k on a rear & 20-25k on a front with those pressures & have not managed to scare myself too badly in a fast curve. Stuff drags before the tires let go. Even on the Dumflops, which get replaced as soon as the OEMs wear out. They're like rocks compared to Metz or Avons, as far as ride quality goes. Works for car tires also.
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  #12  
Old 5th June 2012
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I have no experience with motorcycle tires but with bicycle tires, the wider the tire on a given rim width and pressure, the pointier (as previously mentioned) the tread section gets and also, the tire will have a higher tendency to roll flex. It may be a non-issue with motorcycles but it's something I've thought about before when people mention getting wider tires.
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  #13  
Old 5th June 2012
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Originally Posted by Jimmy_Hoffa View Post
I went and looked last night (with a flashlight) and the Shinko sidewall says max. inflation is 42psi WOW! So I put 42 in it. We'll see how it handles now. Unfortunately it's supposed to be raining here through the weekend :-(
Prolly handle like chit...42psi is too high, your reducing the contact patch and setting yourself up for a get off by reducing the overall traction...overall the 10% rule is a good practice..

BTW- running a 80/90 versus 90/90-21 is not much difference or very noticeable at all, been running both tires for years with no issue at all, not like it's a 130 series tire up front, then yeah you'd prolly notice a huge difference between the two depending on your riding style?
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  #14  
Old 7th June 2012
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Quote:
Originally Posted by norseXL View Post
Using a to wide tire on a narrow rim will make the tires profile more pointy and give a more nervouse feel.
BINGO! That's exactly how I'd describe the feeling. It did get worse when I went from 20 to 30psi. Haven't tried 42 yet. The indy who mounted it only put 20psi in it.
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  #15  
Old 7th June 2012
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I guess we all know that 20psi is too low: I'd start at 30psi at least. I had the same problem you are having: Felt like my front tire was following every crack in the road. Had 40 psi in the front based on a friends opinion. Dropped it to 36 and it got much better. Good luck brother.
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  #16  
Old 7th June 2012
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Too low a tire pressure, 30 psi, may allow the side wall to squiggle and follow rain grooves in the road. Too low a pressure will also allow the rim to bottom out against the tire when you hit a sharp bump like a big pot hole or the concrete driveway transition. Too low a pressure is also dangerous because of excessive heat build up.

Too high a pressure reduces contact patch because the tire gets pointy in the center, that can cause reduction in braking.

Cheap tires with weak sidewalls, like the stock Dunlop, need 40 psi just to get the side wall stiff enough to not wander all over the place.

Better tires like Metzler ME 880's and Avon Venom X, can use lower pressure than the stock Dunlops and still not wander around.

The psi rating on the side wall is for maximum weight. If you are not running the maximum weight, you probably don't need max psi if you are using good tires.

Bigger tires, such as on the rear, or on the 48 (I think the 48 has the big front tire) need less pressure than skinny tires.

Harley's recommendation of 30 psi on the front is best ignored. Total BS, and I have no idea how they figured that.

Bottom line, try pressures from 30 to 40 psi and see what works best for you.

If you put a tire size not recommended for the rim size, you are on your own.
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  #17  
Old 22nd July 2012
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I wanted to update, I'm running 41~ PSI, sidewall says 42psi. It handles great now. From VERY sketchy to steady as a rock. The indy who mounted these shinkos told me how they have such weak sidewalls and he won't even order them for people because they cheaply made imported tires, but I wrote it off as him just being a dick, he's been like that before. But this info may help others, if you run 90/90-21 shinkos 77s, or others maybe, run full pressure.
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  #18  
Old 22nd July 2012
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Quote:
From VERY sketchy to steady as a rock.
Good to hear....of course it won't help you going over an open grated bridge....talk about unsettling.
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  #19  
Old 18th September 2013
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Quote:
Originally Posted by Jimmy_Hoffa View Post
I wanted to update, I'm running 41~ PSI, sidewall says 42psi. It handles great now. From VERY sketchy to steady as a rock. The indy who mounted these shinkos told me how they have such weak sidewalls and he won't even order them for people because they cheaply made imported tires, but I wrote it off as him just being a dick, he's been like that before. But this info may help others, if you run 90/90-21 shinkos 77s, or others maybe, run full pressure.
i get that same nervous feeling i just mounted them this weekend and it seems like they have a weird handling on them im running 36 PSI now i weight 250 LBS i will bump it up to 40 and see what happens..
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  #20  
Old 18th September 2013
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Originally Posted by MaNickles View Post
i get that same nervous feeling i just mounted them this weekend and it seems like they have a weird handling on them im running 36 PSI now i weight 250 LBS i will bump it up to 40 and see what happens..
Run whatever the sidewall says. My last post was over a year ago, I'm still on the same tires and my bike is steady as a rock now. Besides upping the pressure, I feel like these tires must have needed to be broken in or something.
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