Running a 110 rear tire on 125 ok?

ecmx274
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ecmx274
So I have always ran a 100/90/19 on the rear of my 125s. Even with a 2.15 rim I still ran the smaller tire. Would it hurt to run the wider tire? The dealer I buy my tires from said don’t do it. He even gave me a reason why I can’t remember exactly what he said but it was something like it will mushroom out and cause problems in turns. The most recent mxa yz125 build they suggest to run the wide tire. So what is it no don’t do it or yea it’s a improvement?
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SoCalMX70
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SoCalMX70 8/12/2020 1:39pm
8/12/2020 1:39pm
ecmx274 wrote:
So I have always ran a 100/90/19 on the rear of my 125s. Even with a 2.15 rim I still ran the smaller tire. Would it...
So I have always ran a 100/90/19 on the rear of my 125s. Even with a 2.15 rim I still ran the smaller tire. Would it hurt to run the wider tire? The dealer I buy my tires from said don’t do it. He even gave me a reason why I can’t remember exactly what he said but it was something like it will mushroom out and cause problems in turns. The most recent mxa yz125 build they suggest to run the wide tire. So what is it no don’t do it or yea it’s a improvement?
Is that mxa YZ the same one where they gained 5hp on the dyno? For a bike that built I could see running a 110. On anything else I think you're losing power by adding more weight/drag to the bike... I realize that is an overly simplified explanation, but I believe that is the main reason for the standard 100 size on 125s.
Falcon
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Falcon 8/12/2020 2:45pm
8/12/2020 2:45pm
Damon Huffman used to run a 110 on his '94 RM125, and that was a Suzuki. GrinningGrinning

You can do it, but like mentioned above, the lighter weight of the 100/90 will spin more easily. If you can tell the difference between the two in the corners, you are far more sensitive than I.
AJ565
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AJ565 8/12/2020 2:54pm
8/12/2020 2:54pm
The Hoosier 110 is not much wider then the 100 and weighs less so thats an option too.
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gkelm
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gkelm 12/27/2021 6:01am
12/27/2021 6:01am
I’m interested in this as well. When my son moved up to his used KTM 125sx, it had a 110 and that’s what I replaced it with. Decision time again, and I lack the experience. A couple of techs said stick with 110, but I can see a good argument for a 100.

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Mr. Robinson 12/27/2021 4:55pm
12/27/2021 4:55pm Edited Date/Time 12/27/2021 4:56pm
My buddy runs one all the time. Probably because I run a 120 on my 250.
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murph783
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murph783 12/28/2021 9:21am
12/28/2021 9:21am
It’ll effect handling and you may feel a power delivery difference. That said it’s not gonna hurt anything. Who has a 2.15 rim on a 125 though?
GingerSnapRacing 12/28/2021 10:37am
12/28/2021 10:37am
murph783 wrote:
It’ll effect handling and you may feel a power delivery difference. That said it’s not gonna hurt anything. Who has a 2.15 rim on a 125...
It’ll effect handling and you may feel a power delivery difference. That said it’s not gonna hurt anything. Who has a 2.15 rim on a 125 though?
A lot of the off the shelf (readily built) after market wheel sets only come with 2.15 rears.
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murph783 12/28/2021 1:48pm
12/28/2021 1:48pm
murph783 wrote:
It’ll effect handling and you may feel a power delivery difference. That said it’s not gonna hurt anything. Who has a 2.15 rim on a 125...
It’ll effect handling and you may feel a power delivery difference. That said it’s not gonna hurt anything. Who has a 2.15 rim on a 125 though?
GingerSnapRacing wrote:
A lot of the off the shelf (readily built) after market wheel sets only come with 2.15 rears.
Yeah now that you mention it I know I’ve gotten them for a 250f when I ordered aftermarket stuff so makes sense
Bruce372
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Bruce372 12/29/2021 7:25am
12/29/2021 7:25am
murph783 wrote:
It’ll effect handling and you may feel a power delivery difference. That said it’s not gonna hurt anything. Who has a 2.15 rim on a 125...
It’ll effect handling and you may feel a power delivery difference. That said it’s not gonna hurt anything. Who has a 2.15 rim on a 125 though?
All the ktm mx bikes come with 2.15 back rim from 125, 150, 250, 250f , 350, 450.

Pretty cool so you can swap wheels across any bike.

The 125s have so much power stock, it can run a 110 no problem and handling won't change much because the chassis is pretty much the same through the bikes.
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gkelm
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gkelm 12/29/2021 8:23am
12/29/2021 8:23am Edited Date/Time 1/7/2022 8:47pm
Right on, Bruce372, appreciate that. Some say the 100 turns easier, but my local shop guy also said so many run 110s that the ruts are all 110 size. Either way, we’re sticking with the 110.

And yes, between my son and I we have 4 orange bikes, so makes it nice on the parts overlap. That said, just bought him a new Tusk/MX33 set to keep aside for race days.
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ericgst
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ericgst 1/7/2022 8:44pm
1/7/2022 8:44pm
On the smaller 1.85" rim width, the 110 tire will be rounder as the beads are pulled closer together. This will effect the handling a little but people do it all the time. On a 2.15" rim the 110 tire will fit properly and a 100 will actually be misshaped.

This is actually pretty minor and people run 110 tires in 1.85" rims all the time. Most people will not be able to tell a difference.

I would recommend a 100 in a 1.85" rim and a 110 in a 2.15" rim, but it really is not a big deal either way.
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