ARO suspension setup thread

Apr 22, 2019
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Hello all,

I would like to discuss suspension setup of the Timbersled ARO platform:

This is my first year snowbiking...but have been riding dirt bikes for over 50 years...I started riding when I was 6. I also have 2 years of snowmobile riding under my belt.

I have a 2020 ktm 500 xcf-w with most of the power-up goodies, and an 2019 ARO 137 kit, along with a Trio and TSS.

I weigh 245 lbs, and am 5-6" tall...short and stocky (used to power lift in college).

I will start off by saying that I love my snowbike.

I started off with the kit being all stock, with the TSS needle pointing straight down, and 50 lbs in the secondary chamber, and 25 lbs in the secondary chamber of the Trio. In this configuration, I felt like there was a lot of ski pressure, and turning was done mostly by leaning. (Learning curve.) Slow going was difficult because it was really hard to turn.

I played with both rising and lowering the forks in the tripple clamps, and settled on having it at the third line from the top.

My next move was to shorten the TSS about 1/4 inch (5 turns), and that helped somewhat as well with the ski pressure. Studying showed me that the fixed strut recommended length from Timbersled is 1/4 inch shorter than the TSS.

After that I started to look at spring rates, and discovered that my setup came with a 150# spring in the front, and a 175# spring in the rear...which seems to me to be the reason the ski feels so planted. I played with increasing pre-load on the front, and reducing the preload on the rear with little success...but this spring setup seems counter intelligent to lightening the front end and making it easier to steer. I ended up replacing the front spring with a 200# spring, and things started to come into focus. When I finally had about 1" of pre-load on the front spring, and only 1 turn on the rear to keep the spring in place it finally felt what I considered to be ridable. I could go over most things easily...would lean forward to climb, and back to bring up the front end as desired. Because I had reached the max pre-load on the front spring (I could coil bind it on landings) I switched to a 225# spring on the front, and things got even better. (3/8" pre-load on my final ride of the year) I also discovered during my studying that the TSS we are using for the ARO is the same one used on the previous models, but the ARO has more of a leverage advantage. Looks like the TSS definitively needs some valving and/or air chamber modifications. I will try the x-tune over the summer, along with shortening the TSS yet some more.

I also swapped the upper and lower secondary gears on the kit to get some more snap to lighten the front end...and liked the results. Because the 500 xcf-w has a wide ration gearbox, I was thinking about trying to find a 17 tooth sprocket for the top of the secondary sprocket set to lower the gearing down again...anyone know a source for these? And your thoughts?

I am writing this because I would like others experiences with setup on suspension, and recommendations.

Thank you in advance,

Chris
 
Apr 22, 2019
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Adding to this topic...I have tried three different skegs on the stock TS ski that came with my 2019 ARO kit. The stock one, the Duse Boy, and the Tri-Point. They seem to work about the same in powder, but for overall riding on a variety of snow conditions, as well as ease of steering, my nod goes to the Tri-Point, with the Duse Boy being my least favorite.

Chris
 
Dec 20, 2007
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Sounds like your getting close. I've been riding a riot all season and was always thinking you could probably make the aro pretty close with a stiff center spring. The riot center spring is 3 times stiffer than the rear from the factory.

Only thing I might add is now that you have the stiffer center spring and shorter strut you might want to try softening or removing the trio. If it helps the ski pressure feel but starts to bottom the fork then just add more fork oil. (Alot more if necessary)
 
Apr 22, 2019
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Sounds like your getting close. I've been riding a riot all season and was always thinking you could probably make the aro pretty close with a stiff center spring. The riot center spring is 3 times stiffer than the rear from the factory.

Only thing I might add is now that you have the stiffer center spring and shorter strut you might want to try softening or removing the trio. If it helps the ski pressure feel but starts to bottom the fork then just add more fork oil. (Alot more if necessary)
I was thinking about removing the Trio and trying the oil thing and/or adding an air-pro.

Chris
 
Dec 14, 2009
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I spent the season chasing my tail attempting to get the thing to climb on top of the snow without having too much ski pressure. Next season I'll be ditching the TSS and going to a solid strut or a custom 3rd shock. With the TSS length as spec'd by Timbersled the kit would trench like crazy until I loosened the rear spring up and cranked the front. After that I shortened the TSS and things improved but I was never happy with deep snow performance. I started out with 205lb springs and later went to 250lb springs because I was bottoming too much and my experience with the Mtn horse was that stiffer springs with less preload rode better and climbed on top of the snow easier.
 
Apr 22, 2019
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I spent the season chasing my tail attempting to get the thing to climb on top of the snow without having too much ski pressure. Next season I'll be ditching the TSS and going to a solid strut or a custom 3rd shock. With the TSS length as spec'd by Timbersled the kit would trench like crazy until I loosened the rear spring up and cranked the front. After that I shortened the TSS and things improved but I was never happy with deep snow performance. I started out with 205lb springs and later went to 250lb springs because I was bottoming too much and my experience with the Mtn horse was that stiffer springs with less preload rode better and climbed on top of the snow easier.
What kit were you working with? ...I have had several people say to shorten the TSS between 1/4" and 1/2". I went with 1/4" shorter, but am planning on shortening some more to try.
 
Dec 20, 2007
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Go analagy on the boat. When I was young my dad got an old junker from the 60s that didn't have enough power to plane out with 3 people in it so we always had to shuffle stuff around and sit in the middle to get it to plane. We never cared about speed but it used way less fuel when it planned.

The difference on a snow bike is that the ski is not as big as the track surface area and there is no "hull" at all between the ski and track but half the weight of the bike is on it. That's why moving the gas back pegs back bars back and rider back makes such a huge difference. Also juggling sprockets to get the chain adjuster as short as possible moves the track more under the load.

One thing I learned this year is how much easier it is to plane with less front weight and at the same time it's easier to plane it becomes easier to wheelie too with much less effort to steer. Win win.
 
Apr 22, 2019
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Go analagy on the boat. When I was young my dad got an old junker from the 60s that didn't have enough power to plane out with 3 people in it so we always had to shuffle stuff around and sit in the middle to get it to plane. We never cared about speed but it used way less fuel when it planned.

The difference on a snow bike is that the ski is not as big as the track surface area and there is no "hull" at all between the ski and track but half the weight of the bike is on it. That's why moving the gas back pegs back bars back and rider back makes such a huge difference. Also juggling sprockets to get the chain adjuster as short as possible moves the track more under the load.

One thing I learned this year is how much easier it is to plane with less front weight and at the same time it's easier to plane it becomes easier to wheelie too with much less effort to steer. Win win.
I wanted to play with moving the track forward as well...where do you get the timbersled sprockets?

Also...what do you feel is the best way to move the handlebars back...I am short...and would love to move the handlebars rearward.

Chris
 
Dec 20, 2007
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timbersled.com has sprockets from 17 to 19 tooth. I have also found that KTM countershaft sprockets kind of fit. I'm running a 16 tooth from a ktm lc4 Dual Sport on my Drive axle and it slides right on but on the jackshaft it's pretty tight and I have to hammer it on so results May Vary.

To move the bars back I use a 2in Rox riser at a 45° angle rearward.I'm selling these for 50 bucks if you're interested they have the rubber anti-vibration mounts so they twist pretty easy if you crash but the solid version is available on eBay.
 

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Apr 22, 2019
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timbersled.com has sprockets from 17 to 19 tooth. I have also found that KTM countershaft sprockets kind of fit. I'm running a 16 tooth from a ktm lc4 Dual Sport on my Drive axle and it slides right on but on the jackshaft it's pretty tight and I have to hammer it on so results May Vary.

To move the bars back I use a 2in Rox riser at a 45° angle rearward.I'm selling these for 50 bucks if you're interested they have the rubber anti-vibration mounts so they twist pretty easy if you crash but the solid version is available on eBay.
Thank you for the info...I was guessing that you probably used the 2" Rox risers...and had already ordered a set of solid ones a week ago...(LOL... thinking that the dampened ones might bend when I crash).

I am also having my rear shocks shortened, and will be buying the shorter front assembly off of the new S models in order to lower my bike 3". The downside to the S models is that because of the shorter assembly...my trio won't work...so I am going to need to re-valve my front forks. Do you know anyone locally that you would recommend?

Thank you for your suggestions,

Chris
 
Apr 22, 2019
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I was mistaken in my writing of my original secondary gear ratio up above. Stock secondary gearing is a 18 driving a 17 sprocket...and I reversed the two sprockets to a 17 driving an 18..a gear reduction of aprox. 11% which I really liked.

My primary gearing as recommended from Timbersled is a 13 tooth countershaft sprocket driving a 17 tooth sprocket on the kit. From eric's info above...I think I am going to order a 18 tooth driven sprocket, which will not only reduce my gearing aprox 8% again, but will require me to move the track/kit forward towards the bike for proper chain tension. Seems like a win/win situation. First gear will become almost useless...but this thing (2020 ktm 500 xcf-w) has a 6 speed...and I find myself mostly in 3rd. Moving the track forward should help somewhat with lightening the ski.

Chris
 
Jan 28, 2011
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I recently bought a 2017 rmx450z w a 2018 aro-20le. I noticed the previous owner drilled new holes in the tunnel to mount the rear suspension about an inch higher. What effect would this cause to the suspension characteristics? Should i put it back to stock?
 
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