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2017 KTM 350 XC-F shock spring rates - Who is right?

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Background:

200lb (no gear) novice rider, ride MX and trails

The stock spring rate on the bike is 4.3kg/mm.  The KTM manual states that for a 187-209 lb. rider that the spring should be 45N/mm (approx. 4.6kg/mm)

On the suspension websites, when I put it in my information, the recommendation is consistently for a 4.9kg/mm spring.

Does the KTM manual perhaps use rider weight, with gear, as opposed to the suspension websites that use without gear?  I'm trying to figure out which is right, although my spidey senses suggest I should be going with the 4.9 spring.

Any thoughts would be appreciated.

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38 minutes ago, mog said:

I think the 4.9might be a tad stiff my chart says4.6

Sent from my XT1650 using ThumperTalk mobile app
 

MOG, thank you for the feedback.  Which chart are you looking at?  I couldn't find anywhere other than the KTM manual that said 4.6.   Bear in mind, I'm +/- 200 nekkid, so probably 225 with gear on.

I have a 4.3 on there now and I'm running a ton of preload to get the sag.  I kind of have one shot to get this "right" to avoid the wife agro that I will suffer if she sees me buying more parts for this bike.  :cry:

Edited by Juman5

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My Husky manual assumes rider + gear in the spring rate tables.  You can extrapolate the tables in your owners manual.  For instance, my FE501 came with a rear spring that was 48N/mm for a rider/gear that is 165-187lbs.  In the table, they only showed one spring rate below stock, and one above stock.  Weight range changes in 22 lb increments, and springs rates change in 3 N/mm increments.  Geared up, I'm 245 lbs, say 60-70 lbs over the stock spring rate.  Since each spring rate change adds 22 lbs of rider/gear rate, I needed to go up 3 sizes.  Again, each size changes by 3 N/MM, so 3 size changes meant I swap to a 57N/mm spring rate (9N/mm larger than stock).

You can do the same thing from the tables in your manual.  

If you need to convert from N/MM to KG/mm, just divide the N/MM by 9.8 (gravity).  So my spring would also be a 5.8KG/mm rate.

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MX tech has a spring chart. I have found it to be right on for me. It's on the website, Click  tech info ..then spring chart ..then link shock .. looks like 4.7 kg to 4.8 if you're on the taller side. They specifically don't list a 350 but you can get a solid idea, I go 1kg less than the spring 450 line.

mogs suggestion of a 4.6kg would be good as you mentioned trails. But if you are over 6'   I would go up a kg.. You may need a click or 2 of rebound for any of these stiffer rates

If you are going by the RT calculator It seem off a bit for KTM's anyway

I have ridden a 17 350xcf on a moto track hooked up great but with the stock springs it was a wallowing bottoming  mess for me at 200#

Try Diverse springs or factory connection between those 2 they will have nearly any rate you need .

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I think all these rates will work but with varying preload and static , a 5 imo will have no preload , a 4.8 will have a little preload and a ,4.7 or 4.6 a decent amount , i think a ,4.7 would be a safe bet

Sent from my XT1650 using ThumperTalk mobile app

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Just a follow up, in appreciation for all that replied.

I went with a Factory Connection 4.9kg/mm spring.  To dial in 105mm/35mm, I was almost at the end for any preload at all (I almost ran out of threads on the top of the shock).  This spring seemed great for bottoming resistance, but the bike did not hook up as well and something just seemed off. I wanted to give it a chance to settle and me to get used to it , so I rode for a few months including 9 races.  I can't really put my finger on it, but I just couldn't get comfortable with this setup.

I've ordered up a Factory Conncention 4.6kg/mm spring and I'll give that a try, but I think it'll be a little easier for me to get 105mm/35mm.  Hopefully I get my comfort level back.

Thanks to all for the advice.

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3 hours ago, Juman5 said:

Just a follow up, in appreciation for all that replied.

I went with a Factory Connection 4.9kg/mm spring.  To dial in 105mm/35mm, I was almost at the end for any preload at all (I almost ran out of threads on the top of the shock).  This spring seemed great for bottoming resistance, but the bike did not hook up as well and something just seemed off. I wanted to give it a chance to settle and me to get used to it , so I rode for a few months including 9 races.  I can't really put my finger on it, but I just couldn't get comfortable with this setup.

I've ordered up a Factory Conncention 4.6kg/mm spring and I'll give that a try, but I think it'll be a little easier for me to get 105mm/35mm.  Hopefully I get my comfort level back.

Thanks to all for the advice.

Probably too late but FC also sells used springs for a great savings and they are good as new. And they often give credit for your used FC spring in a swap deal.

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As you saw ktm recommendation are wrong , you end up with too little preload , I bought 3 springs before I learnt the book is wrong

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