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AndreB

Using 19" Rear Wheel over standard 18"

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Hi New around here so not sure if I've this in the wrong place, apologies if so.

I've recently bought a 2019 Husqvarna FX350, my first enduro/XC bike as I've always had MX'rs and wondering since it has an 18 rear ( not sure why they have 18 over 19, maybe someone can educate me ) can I use a 19" wheel when wanting to do some MX races and keep the 18" for XC, reason being the better variety of rear tyres available for 19". I have the stock gearing of 14/50 what should I have on a 19" wheel if I can do this.

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Just keep the 18. No need to waste money. MX bikes used to have 18" rear wheels until some time in the 90's. Then they switched to 19".

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Ya I went 19 to 18 on my CRF250R cus I don't ride MX tracks etc and IMO more options for 18 tires for single track/enduro etc which is what I ride.

rear wheel size does not effect chain length and not 100% sure of how 19 vs 18 effects gearing but IMO I didn't notice any effect with my 13/51 when I went to a 18"

I believe @Fatt_Tones went to a 19" rear on his Husky and might have full rear setups for both?

Edited by filterx
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They have an 18 because you get a larger footprint when aired down. But yes you can switch to a 19 if you want better tire selection. As far as what size, that depends on the manufacturer. For instance, the irc m5b 110/90/19 is 5/8s wider than the 120/80/18. I know, it doesn't make sense but that's what it is. As far as overall diameter, I don't think you would notice it in the gearing as much as a one tooth rear sprocket change.

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1 hour ago, AndreB said:

 

Hi New around here so not sure if I've this in the wrong place, apologies if so.

I've recently bought a 2019 Husqvarna FX350, my first enduro/XC bike as I've always had MX'rs and wondering since it has an 18 rear ( not sure why they have 18 over 19, maybe someone can educate me ) can I use a 19" wheel when wanting to do some MX races and keep the 18" for XC, reason being the better variety of rear tyres available for 19". I have the stock gearing of 14/50 what should I have on a 19" wheel if I can do this.

 

 

18" is less resistant to pinch flats.  19" is a lighter set-up (unsprung weight) and less "wallowing" effect of the sidewall when cornering hard or landing jumps with a little side pressure on the bike.  People who trail ride will say you won't feel the difference or it is negligible at best and I agree.  I like the fellow's comment about a bigger footprint with the 18" at lower psi.  However, if you ride MX you will definitely feel (or at least I did) the difference when in the air over jumps as to how sensitive your bike is to corrective inputs.  Maybe my 18" was slightly out of true (which it isn't) then combine a heavy rimlock on one side of the wheel and get that thing spinning around in the air with the centrifugal force of the speed of 3rd/4th gear and you will definitely feel it.  I experienced more vibration with the 18" and more resistance to subtle inputs when airborn.  I put one of those 2oz composite rimlocks on my 19" set-up for MX and I will tell you right now the bike feels a lot smoother and more responsive in the air than it did with the 18" on there....especially before I ditched the 4-1/2lb ultra HD tube.  It also seems to have a more planted feel in corners....but that is to a much lesser degree than the mid air stuff I mentioned.  ....and as you mention it's nice to have more MX tire options.

 

It is also nice to have two set-ups for various terrain.  For example I ride mostly sand and hardpack, so after my 18" tire is worn I will be installing a sand tire onto my 18".  As far as gearing goes, I don't know about the 2019 transmission, but the 2018 FX (350) is geared a fair bit taller/broader than it's FC brother.  I can clear some pretty big jumps, and I mean jumps that most of the 250's are using 4th gear with my FX350 in 2nd gear with 14/50 gearing.  It's a little sketchy in 2nd and I typically use 3rd, but easily doable in 2nd.   Some people hate it, but I love it when you never seem to run out of gear and the bike just pulls and pulls.  It is deceptively fast where you think the motor is signing off and based on your experiences with other bikes, your mind will tell you it's time to shift, but if you don't shift, and just hold it open, it is insane how long the motor pulls.  Yet the motor still makes enough grunt to pull the lower part of the next gear.  There have been many instances now on the track where I'm coming up to a jump and realize I'm a gear too low, but it's too late to shift, I realize I am carrying the speed, so I just pin 2nd and make it over no problem.......conversely there are other instances where I come out of the corner and realize I'm still in 3rd, but rather than downshifting, just grab a handful and the thing just pulls all the way up on through....slight bog feel....but it is still pulling......very deceiving power curve.   I personally love it's forgiveness with the 14/50 gearing but most people don't like it.  Not sure what kind of XC riding you do, but if it isn't desert or wide open stuff, I would consider 13/50.  Even for moto (for my tracks) I would maybe consider a 51 rear when replacing my sprocket.  The FX is just a stupid fast motorcycle with stock gearing.

 

I'm certainly no pro and what I've written is just what my experiences have been.  No, switching to a 19" is certainly not a necessity.  A bike equipped with an 18" on an MX track will certainly outperform my abilities as a rider, but if you have the resources it is nice to have the 19" for the track and the bonus of an 18" as an easy swap for offroad or different terrain. 

 

Wheels.jpg.7bf28a9497f5f3506b0abd9871e95a71.jpg

 

 

 

Next on deck for the 18"

 

IMG_6049.thumb.jpg.cd4ee0e9368c3a406cf4178e4fe8b9a2.jpg

IMG_6050.thumb.jpg.cb42f23fb14b6ef2dd8b3864fcb1df08.jpg

 

 

 

 

47 minutes ago, filterx said:

Ya I went 19 to 18 on my CRF250R cus I don't ride MX tracks etc and IMO more options for 18 tires for single track/enduro etc which is what I ride.

rear wheel size does not effect chain length and not 100% sure of how 19 vs 18 effects gearing but IMO I didn't notice any effect with my 13/51 when I went to a 18"

I believe @Fatt_Tones went to a 19" rear on his Husky and might have full rear setups for both?

 

 

 

 

.

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The outside diameter of 18" and 19" is virtually the same, no gearing change needed. I have a crf450rx that comes with 18" and I use 19" rims off my crf450r for spares, or when I want to run a different tire.

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18" has a bigger profile. More tyre - more air - makes it easier to change pressures to improve traction and conform to different trail conditions. Tyre can flex around roots and rocks not found on MX tracks with less chance of a pinch flat.

 

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.
Thanks for the detailed response! Much appreciated to get feedback like that from someone. It's made my decision easier now to have 2 setups like yourself, I'm gonna try just with the standard gearing for both the 18 and 19 first, see how I get on with it then see if I should change up the front or rear sprockets
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2 hours ago, AndreB said:
On 8/12/2019 at 2:04 PM, Fatt_Tones said:
 
 
 
 
.

Read more  

Thanks for the detailed response! Much appreciated to get feedback like that from someone. It's made my decision easier now to have 2 setups like yourself, I'm gonna try just with the standard gearing for both the 18 and 19 first, see how I get on with it then see if I should change up the front or rear sprockets

 

Definitely try the stock gearing for a reasonable amount of time before dismissing it.  The 350 is a different animal.  Honestly my 2018 is approaching 70 hours and I am only now really learning to exploit it's power.   Both your 18" and 19" tire should have the same outside diameter, so each should not require different gearing based on that, but rather for the intended application of your 18" vs your 19".

 

Glad to be of help :thumbsup:

 

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On 8/12/2019 at 2:38 PM, Clutch44 said:

As far as what size, that depends on the manufacturer. For instance, the irc m5b 110/90/19 is 5/8s wider than the 120/80/18. I know, it doesn't make sense but that's what it is.

Yeah, tire sizing is weird and totally varies by brand. The sizes can be 1/2" in width or more different between brands while going from brand to brand. Makes no sense at all. I don't know if there is even a method to how they label sizes

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Posted (edited)

Unfortunately there seems to be no industry standards for dirt bike tire measurements.

Apart from the rim diameter, each tire manufacturer uses whichever method they choose to size the width and profile ratio.

 

In the past Michelin was especially bad at making things even more complicated by sizing some of their models differently than others.

Overall width measured at the carcass for some or, at the edge of the outer knobs for others.  (the S12XC and M12XC come to mind)

Even advertised at the same size, many of their current Starcross 5 tires are lower in profile than the previous generation Starcross 3 (MS3 & MH3)

but that seems to be a new trend in motocross race tires having seen a few Bridgestone X-- tires also lower in profile versus the previous M403/M404.

 

It's a gamble each time you buy a new tire from a different brand,

you may be getting a smaller/larger tire than your old one despite both having the same advertised size. 

Edited by mlatour
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