18" rear wheel for off road YZ125-yea, it's worth it.

[rpt50]

Well I have now tried my 18" wheel on both my 03 and 06 "woods duty only" YZ 125s, and I've come to the conclusion that it is a worthwhile mod.   The bigger tire seems to help with bump compliance and traction on rooty corners and uphills (two areas where the 19" kicks around a lot), and I don't really notice any significant penalty due to drive line mass.  A few things that might be of interest:

1. I did the Tusk rim/spoke kit for $127.  IMO a great deal.  High quality and easy to assemble.  I am done messing with seized spokes and truing wheels on used bikes.  I'm just buying the tusk kit.

2. I have used Artrax and IRC vulcanduro 100/100 18 tires.  Both are light, but I the IRC feels lighter (I don't have anything at the house to accurately weigh a tire).  I also use a standard tube.  With the standard tube and 1 rimlock, the 18" assembly is about 1 - 1.5 pounds heavier than the 19" as best that I can tell with the super scientific apparatus I have at home (me holding the wheels while standing on a bathroom scale).

3. When I say it is worth it, I mean it's somewhere on the list after getting your suspension re-valved, getting appropriate bike protection for your conditions, and keeping fresh tires on your bike.  It's not the first thing I would rush out and do for a YZ125 that is going to see off road duty.

Edited February 11, 2019 by rpt50

[YAMAHA NICK]

I’ve got the rim kits in my cart on rocky mtn. However I got side tracked with a LHRB on the 250x. Rekluse thinks their master cylinder sleeve is made from gold or titanium.
I’ve since had the rear shock revalved for woods and I’m still running the 525 in 19”. The bike tracked straight over some bad chop and up some slick rock infested climbs. I’m wondering how much better the 18” would improve the handling with what I’ve got done so far?

[YZPauly]

Well I have now tried my 18" wheel on both my 03 and 06 "woods duty only" YZ 125s, and I've come to the conclusion that it is a worthwhile mod.   The bigger tire seems to help with bump compliance and traction on rooty corners and uphills (two areas where the 19" kicks around a lot), and I don't really notice any significant penalty due to drive line mass.  A few things that might be of interest:
1. I did the Tusk rim/spoke kit for $127.  IMO a great deal.  High quality and easy to assemble.  I am done messing with seized spokes and truing wheels on used bikes.  I'm just buying the tusk kit.
2. I have used Artrax and IRC vulcanduro 100/100 18 tires.  Both are light, but I the IRC feels lighter (I don't have anything at the house to accurately weigh a tire).  I also use a standard tube.  With the standard tube and 1 rimlock, the 18" assembly is about 1 - 1.5 pounds heavier than the 19" as best that I can tell with the super scientific apparatus I have at home (me holding the wheels while standing on a bathroom scale).
3. When I say it is worth it, I mean it's somewhere on the list after getting your suspension re-valved, getting appropriate bike protection for your conditions, and keeping fresh tires on your bike.  It's not the first thing I would rush out and do for a YZ125 that is going to see off road duty.

I just posted a thread asking about this. Thank you for this info it is much appreciated.

[YZPauly]

Well I have now tried my 18" wheel on both my 03 and 06 "woods duty only" YZ 125s, and I've come to the conclusion that it is a worthwhile mod.   The bigger tire seems to help with bump compliance and traction on rooty corners and uphills (two areas where the 19" kicks around a lot), and I don't really notice any significant penalty due to drive line mass.  A few things that might be of interest:
1. I did the Tusk rim/spoke kit for $127.  IMO a great deal.  High quality and easy to assemble.  I am done messing with seized spokes and truing wheels on used bikes.  I'm just buying the tusk kit.
2. I have used Artrax and IRC vulcanduro 100/100 18 tires.  Both are light, but I the IRC feels lighter (I don't have anything at the house to accurately weigh a tire).  I also use a standard tube.  With the standard tube and 1 rimlock, the 18" assembly is about 1 - 1.5 pounds heavier than the 19" as best that I can tell with the super scientific apparatus I have at home (me holding the wheels while standing on a bathroom scale).
3. When I say it is worth it, I mean it's somewhere on the list after getting your suspension re-valved, getting appropriate bike protection for your conditions, and keeping fresh tires on your bike.  It's not the first thing I would rush out and do for a YZ125 that is going to see off road duty.

Also were did you find your tusk kit ?

[YAMAHA NICK]

Also were did you find your tusk kit ?

Rocky Mountain atv. Com

[Familyman6000]

2. I have used Artrax and IRC vulcanduro 100/100 18 tires.  Both are light, but I the IRC feels lighter (I don't have anything at the house to accurately weigh a tire).  I also use a standard tube.  With the standard tube and 1 rimlock, the 18" assembly is about 1 - 1.5 pounds heavier than the 19" as best that I can tell with the super scientific apparatus I have at home (me holding the wheels while standing on a bathroom scale).

I tried a set of Artrax tires. Couldn’t get rid of them fast enough. In my opinion one of the worst tires as far as traction. Cheap, but poor performers.

[fowler175]

Just curious, which 19" tires did you use as comparison? I have considered running 18" on my yz250, but not quite there yet...

[rpt50]

2 hours ago, fowler175 said:

Just curious, which 19" tires did you use as comparison? I have considered running 18" on my yz250, but not quite there yet...

I've burned through so many tires on that 125 I could not even tell you all the different types I have tried.  One that I did like a lot however was the Sedona mx907 in the 100/90 19 size.  Very skinny with a rounded profile that really makes the bike turn well.  The tire seem to provide decent traction in the usual woods conditions I see.  

[YZPauly]

Well I have now tried my 18" wheel on both my 03 and 06 "woods duty only" YZ 125s, and I've come to the conclusion that it is a worthwhile mod.   The bigger tire seems to help with bump compliance and traction on rooty corners and uphills (two areas where the 19" kicks around a lot), and I don't really notice any significant penalty due to drive line mass.  A few things that might be of interest:
1. I did the Tusk rim/spoke kit for $127.  IMO a great deal.  High quality and easy to assemble.  I am done messing with seized spokes and truing wheels on used bikes.  I'm just buying the tusk kit.
2. I have used Artrax and IRC vulcanduro 100/100 18 tires.  Both are light, but I the IRC feels lighter (I don't have anything at the house to accurately weigh a tire).  I also use a standard tube.  With the standard tube and 1 rimlock, the 18" assembly is about 1 - 1.5 pounds heavier than the 19" as best that I can tell with the super scientific apparatus I have at home (me holding the wheels while standing on a bathroom scale).
3. When I say it is worth it, I mean it's somewhere on the list after getting your suspension re-valved, getting appropriate bike protection for your conditions, and keeping fresh tires on your bike.  It's not the first thing I would rush out and do for a YZ125 that is going to see off road duty.

Hey do you have any pics of your Yz125 with the 18in set ???

[rpt50]

58 minutes ago, Dirtbikepaulito said:

Hey do you have any pics of your Yz125 with the 18in set ???

Not at the moment.  The 18" is currently leaning against my shop wall. My 03 is down with mechanical issues, and the 06 is going to get prettied up to sell, and currently is resting on the stock wheel.  Once I get the 03 back in business I will take a pic.  I will say though that you would need a really sharp eye to even notice the difference between an 18" 100/100 and a 19" 100/90 wheel/tire on a YZ125.  

[YZDOC]

1 hour ago, Dirtbikepaulito said:

Hey do you have any pics of your Yz125 with the 18in set ???

This bike was built with a 1.85 x 18

[YZPauly]

Thank you !

[rpt50]

In the last couple of months I've gotten some serious seat time (race and general woods riding) on the YZ125s, and I would like to modify my conclusions about the 18" wheel/tire combo above.  For the latest generation YZ 125 (aluminum frame), I still think the 18" wheel is a worthwhile mod if you are a woods rider.  Like I said above, it's not the first thing I would do to the bike (suspension is first!), but it is worth doing. 

With more seat time on my 03 however, I think it the 18 may just be a little too much for the earlier engine (perhaps because it has a weaker mid range than the later engine, or only a 5 speed?).  It's just so much more responsive with a 19" wheel and that skinny Sedona MX907 tire on the rear, so I'm willing to put up with the lower compliance of the 19 wheel/tire.  So if you're still rockin' the steel frame YZ125 (greatest bike ever made!), perhaps the 19 is the way to go even if you ride in the woods.  

Edited November 4, 2019 by rpt50

[k.g]

After riding a horrible Ironman GNCC last week, I can say that every bike I'll own from now on will be getting an 18" rear makeover. I did the tusk kit and added a Tubliss and Starcross 5 110/100-18 (which is almost the same height as a 19). Ran 3psi and even though I still suck at mud riding, I had absolutely zero issue getting up any hill. The rear was planted. 

[Armbarn sailor]

I race lots of mx as well as hs and use 18s. I didnt like it when they switched. 18s do whoops, trail junk and mud better every time. Thinking back, most people hated when they did this.

[rpt50]

Hey if you are running an 18" on your 125, here is another thing to try.  I've been experimenting again with the Shinko F255 trials tire (110/90 18).  With a little more than usual trials tire pressure (I've been running 10-13 lbs) it works really well as long as you are not in real mud.  With the higher pressure, it seems to allow the 125 to spin up the way we love, and the cornering is great.  Why bother you ask?  Trials tires last forever, and don't really lose traction like a knobby does when the knobs wear down.  If you ride a lot, trials tires can save you from buying and installing a ton of tires.  I'm so happy with how this tire is working that I'm going to lace up a second 18" wheel from a spare 19, so I can keep a trials tire ready for non mud general riding, and a knobby for racing and mud.  

[shrubitup]

Had a 19" Tusk Recon earlier this year on my RMZ450 (sold). Just picked up a 03 YZ125 and I will be putting on the Tusk Recon 19" rear tire. I found it to work great on the RMZ and expect similar results on the YZ125. Slow trails only.

[rpt50]

3 hours ago, shrubitup said:

Had a 19" Tusk Recon earlier this year on my RMZ450 (sold). Just picked up a 03 YZ125 and I will be putting on the Tusk Recon 19" rear tire. I found it to work great on the RMZ and expect similar results on the YZ125. Slow trails only.

I just put a Tusk recon 18" on my 200.  Unbelievably good traction but man is that a big and heavy tire!  Very happy with the traction but I think I will try something skinnier and lighter when it wears out.  

[shrubitup]

21 minutes ago, rpt50 said:

I just put a Tusk recon 18" on my 200.  Unbelievably good traction but man is that a big and heavy tire!  Very happy with the traction but I think I will try something skinnier and lighter when it wears out.  

So you're saying I may notice the weight some on the 125 and that there's no way to feel it on the 450?