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2017 500 RR-S lowest rear tire pressure

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I know this has probably been beaten to death, but wanted some opinions from you other 500 RR-S riders. Going to Colorado in the next few days for a week of long rides. Was wondering what you folks think is an OK minimum pressure to run the rear tire at (using HD tube only. Brand new Dunlop AT81 120/90) for increased traction, but with little risk of a pinch flat (which I really don't want on the trail).

I have been running at 15 psi rear which seems to work pretty well for me in the mountains of NM. But I have to say I probably haven't done any truly gnarly loose rock hills. Maybe I need to do the tubliss thing on the rear. Don't know why I am avoiding it.

Anyhoo, appreciate your thoughts on this.

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I've been at 9-10 psi.  Has been working well both on and off-road.  I have an HD tube in the rear. 

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17 psi when I raced desert with ultra HD tubes, 15 when trail riding.  Always did my own tires with lots of baby powder on tubes.  I hate flats!

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Define " HD Tube ", because most people think an plain old HD tube actually makes a difference.

2mm, 3mm, 4mm ?

An HD tube (2mm) merely prolongs the enevitable, the pinch flat.  It will not stop a pinch flat, unless you run unreasonable air pressure (like 15)

You have to run at least 3mm and prefferably 4mm tubes if you want to 'eliminate' pinch flats.

I run 6psi (cold!) in the rear with AT81 (regular) and 3mm Michelin tubes. Once hot at the same elevation, that's about 8psi. Go up 1000 ft, and it's nearly 11 psi.

(with Tubliss I run 3psi cold....)

Get used to the feel and look of your tire,  watching your boot pushing down on the rear rim and watching the tire deflect. Once you find the pressure you like, do the boot test to see what it looks like, and use that as a visual guage of tire pressure. Hot tire ONLY.

You can judge your air pressure without a gauge, once you get good at it.

http://www.motosport.com/product/?adpos=1o2&cc=us&creative=188670675724&device=c&gclid=CjwKCAjw6ZLOBRALEiwAxzyCWy_RRyyoHhIFtR6-Y3mssAks63e-W7mBGugQxmMXcj59fmU5VGvJaxoCjYgQAvD_BwE&key=Michelin-Ultra-Heavy-Duty-Inner-Tube&matchtype=&network=g&product_id=MT-IT-027&psreferrer=https%3A%2F%2Fwww.google.com%2F&pssource=true&segment=badger

Edited by THE KRAN
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Thanks for the comments folks. Much appreciated. I will consider them all. The Kran your comments are very interesting as always. Since I think I will be running AT81's now exclusively, hopefully I will be able to get the feel of them like you can. I like the idea of that approach.

The tubes I currently have installed are 3mm.

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do you have anypics of how it looks on your bike. 

I struggling trying to find something in a 140 for mine.

I'm thinking of an irc m5b evo, but the at81 is being considered along with a desert it.

On the stock setup I ran 12 last time I rode with my bald stock michelin.

 

Screen Shot 2017-09-23 at 11.02.51 AM.png

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Sure. Here are a few of the 120/90/18. AT81. 

I find the different manufacturer sizes to not always relate to each other. For example, I think the 120/90 AT81 is very similar in height and width as the 140/80 OEM tire. 

image.jpg

image.jpg

image.jpg

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One other observation. I find that since I put on the AT81, that I notice a more plush feel from the rear when I hit rocks and sharp outcroppings.

I guess Dunlop's advertising regarding this characteristic is true....

 

From their website:  Dunlop’s “plush pad” recess design between tread blocks enhances compliance for bump absorption and ride comfort.

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4 hours ago, mferring1 said:

Sure. Here are a few of the 120/90/18. AT81. 

I find the different manufacturer sizes to not always relate to each other. For example, I think the 120/90 AT81 is very similar in height and width as the 140/80 OEM tire. 

image.jpg

image.jpg

image.jpg

Glad that that it's working for you. When I mounted the 120/90-18 RC81 it made my Beta handle really strange. I also tried the 110/90-18 on my KTM and also really strange handling. Both bikes steered slow and wanted to tuck into the corners. It may very well be because I'm so used to the standard sizes. 

 

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22 minutes ago, ballisticexchris said:

Glad that that it's working for you. When I mounted the 120/90-18 RC81 it made my Beta handle really strange. I also tried the 110/90-18 on my KTM and also really strange handling. Both bikes steered slow and wanted to tuck into the corners. It may very well be because I'm so used to the standard sizes. 

 

The AT-81 and the AT-81RC are completely different tires. Just look at the weight difference for the same size tires....

The RC is for very high speed riding over unknown terrain, aka, South West open desert.  It is not for single track or closed course.  You need more 'room' to turn with this tire.

If you are not riding that kind of terrain, you will have a 'dead' feel in the rear, and have to pull in the clutch more often to eliminate 'push'.

 

The tires pictured above are not the RC type.

Edited by THE KRAN

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2 hours ago, THE KRAN said:

The AT-81 and the AT-81RC are completely different tires. Just look at the weight difference for the same size tires....

The RC is for very high speed riding over unknown terrain, aka, South West open desert.  It is not for single track or closed course.  You need more 'room' to turn with this tire.

If you are not riding that kind of terrain, you will have a 'dead' feel in the rear, and have to pull in the clutch more often to eliminate 'push'.

 

The tires pictured above are not the RC type.

I've tried both. Same exact tire except for the stiff sidewall and added weight on the RC. The point I was making is the strange sizing. Once I swapped out the 110/90 to the 110/100 I was much happier. Front one I could never get used to. 

 

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