Author Topic: MT21 Tire Warning  (Read 2202 times)

Rusty Shovel

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MT21 Tire Warning
« on: February 26, 2014, 10:39:42 am »
Hey all,

A quick word of warning concerning the MT21 tire.  It's a good tire, but make sure you are running at least 26 PSI if you plan to ride a freeway speeds.  If you don't, this'll happen:



See that crazy wear pattern?  That's from a single trip in which I ran the bike at 20 PSI on the freeway for about 100 miles.  More importantly, when under inflated at highway speeds, the MT21 will cause crazy head shake.  If you notice that your front tire is shaking, pull over and check your tire pressure.  I just soldiered on and destroyed my front tire.  Don't be me.
D==[#)
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truck11

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Re: MT21 Tire Warning
« Reply #1 on: February 26, 2014, 12:33:37 pm »
good to know.   Are your wheels balanced?  I balanced my DRZ and it helped so much when riding street.  Just picked up some reusable weights ready for the new bike.
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coarsegoldkid

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Re: MT21 Tire Warning
« Reply #2 on: February 26, 2014, 02:05:49 pm »
Yeah, low psi could be the culprit.  The manual states over 20psi if I remember correctly.  But I usually run 16psi on the dirty parts as a compromise.  My MT21 front did the same thing.  For some reason that single knob doesn't wear much.  D606s wear a bit smoother.  However pavement screws up knobs for sure.  I also ripped bits of knobs off a MT21 rear in Death Valley.  That place has lots of rocks and I managed to get bogged down in deep loose rocks a time or two.  Riding out of them was a futile experience.  I think that's what did in the tire.

Dogfarm

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Re: MT21 Tire Warning
« Reply #3 on: April 25, 2014, 08:09:28 pm »
I just got a new MT-21 and had a couple questions. What kind of pressure are you running off road? Also, do you think their is a need for a rimlock in front? That is have you had the need to air them down so much you needed rimlocks?
2009 KTM 690r
2009 KLR 650
2008 WR250R

Rusty Shovel

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Re: MT21 Tire Warning
« Reply #4 on: April 25, 2014, 09:28:46 pm »
I just got a new MT-21 and had a couple questions. What kind of pressure are you running off road? Also, do you think their is a need for a rimlock in front? That is have you had the need to air them down so much you needed rimlocks?

Everyone has an opinion on this one...and I'm no exception.  I've long since decided that the downsides of low tire pressure are not worth the performance gain.  I may go down as far as 20 lbs if I know I'm gonna be strictly off road.  Otherwise, I stay around 26-29 lbs.  Unless you're riding less than 16 lbs, I don't think you'll need a rim lock.  Just my $.02. 
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mcrider

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Re: MT21 Tire Warning
« Reply #5 on: April 26, 2014, 09:21:41 am »
I'm a believer in rim locks. Picked a pair of Motion Pro yesterday.  I generally run 22 front & 20 rear with slime in both.  If I pickup a thorn & get a slow leak the tire will not slip on the rim.  The wheel will need to be balanced.
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Rusty Shovel

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Re: MT21 Tire Warning
« Reply #6 on: April 26, 2014, 11:10:17 am »
If I pickup a thorn & get a slow leak the tire will not slip on the rim.

That's a good point.
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DaveKubler

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Re: MT21 Tire Warning
« Reply #7 on: July 13, 2014, 04:18:07 pm »
Everyone has their own 'logic' and what works for them re: pressures and all that.   

MY logic has always been as far as a dual sport (not a motorcross bike)..... I run the most aggressive DOT knobbies I can. (for the most part) and I ALWAYS keep em aired up to the manufacture MAX psi.    I get the best , most predictable wear this way.... NEVER get pinch flats, dont need nor care about rim locks.    Yes, you may get better sand/mud traction airing way down, but I don't like the risk/reward factor.   And with this bike, and decent skill set.....   you aint getting stuck ;)   

Rusty Shovel

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Re: MT21 Tire Warning
« Reply #8 on: July 15, 2014, 01:29:00 am »
Just over 3k miles on the MT21's.  They're great times while thay lasted. but the rear is toast and the front is uselessly scalloped.  I'm gonna have looking for an alternate.  Dr Blackbird suggested the MotoZ.  I'll have to check that out.
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ChipStevens

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Re: MT21 Tire Warning
« Reply #9 on: July 15, 2014, 09:30:30 am »
Rusty,  What bike was the picture you posted from? The color of the rim makes me think it isn't your 690. could the suspension have something to do with the wear pattern.  Haven't had the problem on my 2013 690 running 21#. chip

SDMF_Reaps

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Re: MT21 Tire Warning
« Reply #10 on: July 15, 2014, 05:24:17 pm »
Rusty,

If you want to ruin another one  ;D I just removed mine with 2300 miles on it.

You pay freight and I can get it to you.

Rusty Shovel

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Re: MT21 Tire Warning
« Reply #11 on: July 16, 2014, 10:20:30 pm »
Rusty,  What bike was the picture you posted from? The color of the rim makes me think it isn't your 690. could the suspension have something to do with the wear pattern.  Haven't had the problem on my 2013 690 running 21#. chip

Good eye.  This was the MT21 on my WR250R. 

My MT21 on my 690 looks the same after 3k miles.  They actually lasted longer on my KTM than my Yamaha.  I kept the pressure higher this time.  3k isn't bad, but I'm gonna try out the MotoZ's--if only to see whether my loyalty the MT21 is warranted.
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truck11

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Re: MT21 Tire Warning
« Reply #12 on: July 17, 2014, 07:58:16 am »
Not sure why you would run knobbies in the dirt at MAX pressure.   I would rather spend $84 on a tire, run it at 13-16psi and  get better traction and handling.... and lesson the risk of crashing (sliding out, bouncing off the trail etc) ....... which then might end up costing you more than the $84 to replace a tire more often.   Don't ask me how I know this :-)
Putting the knobbies on the street, different story.  Put those pressures up to 20-25psi and ride on.
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Rusty Shovel

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Re: MT21 Tire Warning
« Reply #13 on: July 17, 2014, 09:48:28 am »
Not sure why you would run knobbies in the dirt at MAX pressure.   I would rather spend $84 on a tire, run it at 13-16psi and  get better traction and handling.... and lesson the risk of crashing (sliding out, bouncing off the trail etc) ....... which then might end up costing you more than the $84 to replace a tire more often..

You're absolutely right.  I usually don't deflate out of laziness. :D  If I have a long off-road section I'll air down to 16 in front and 18 out back.  I never run less than 15.  I snake-bit a tire once...I've been leary of running too low a pressure ever since.
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Guymcfly

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Re: MT21 Tire Warning
« Reply #14 on: August 08, 2014, 08:06:15 am »
Usually I find that you get less traction going too low pressure wise on tires with the 690. I think it's because the heavier weight of the bike over say a 500 is causing the tire to flex sideways on the rim. I tried running my tires down around 14 thru rock gardens (on my 525) having been told that over that pressure gave no benefit. I **** two rims over the course of a week!
I don't think a real street legal knobbie is gonna give much mileage or confidence on the tar full stop. There not made for it.