DIY Suspension Build

AirRsq

New Member
Because this is 'supposed to' be somewhat of a budget bike and because I don't race it, I'm going to take advantage of the DIY upgrade to the forks and shock that some others have done instead of just throwing a trick suspension kit at it. This option is a bit out of line with my usual bike upgrades, and perhaps that's why I'm doing it. Don't get me wrong, I love spending money on premium upgrades and I am not discounting the value of doing so, but for me, this bike is a budget track day and occasional street toy. Should be fun...and cheap ;).

There's a fair bit of info spread around various threads about DIY suspension upgrades for the RC390, so I wanted to document my project here along with links to some of the other threads on the subject to hopefully give future DIY'ers a one-stop-shop thread.


http://www.rc390-forum.com/forum/ktm-rc-390-general-discussion-forum/1119-rear-shock-upgrade.html

http://www.rc390-forum.com/forum/wheels-tires-and-suspension/447-shock-swap-99-02-r6.html

2015 KTM RC 390 Suspension Notes


I went a bit nutso on eBay and actually bought three '99-'02 Yamaha R6 shocks :) - hoping to get at least one good candidate and a spare. For the price, why not? Two were $30 bucks and one was $50. The $50 shock is, for all intents and purposes, new. It has no indication of any use; the bumper appears brand new, the reservoir and body are clean and blemish free, the spring has no abrasion marks near the areas where it naturally coil-binds (extreme top and bottom where one coil starts to touch the other to create a flat base). The others are in great shape and will make excellent spares. I suspect '99-'02 R6 shocks will start to get more scarce on eBay as this RC upgrade gets more traction (pun intended) and the fact that these shocks are almost antiques (14-17 yrs old). So, having a couple spares might prove to be cheap insurance.


(Pics of the $50 shock. The spring was installed, I removed it)
IMG_6471.jpgIMG_6472.jpg


In addition to the shock, i'll also be upgrading the fork springs and replacing the oil with 7wt. From most of what I have gathered from other threads, the forks are not as badly in need of a major overhaul as the shock; some heavier oil and respringing for rider weight are a huge improvement and more than adequate for the non-racer.

I've sourced most of the parts from forum vendor, Formula390 - Matt at Formula 390 is a Race Tech dealer and a huge assist so far in this project. He has done a lot of the initial research, to include id'ing the r6 shock as a candidate for this swap.


Parts ordered:

-Race Tech 11.6kg/mm shock spring & adapter collar ($114.99 + $2.99)
-Race Tech 0.95kg/mm fork springs ($124.99)
-Race Tech Shock threaded preload adjuster ($69.99)
-McMaster-Carr bushings PN# 6679K15 - QTY: 2 ($12.10)

6679K15
Metric Steel-Backed PTFE-Coated Bronze Bearing, 12mm OD 10 mm ID 15 mm Length


Parts needed:

-7wt fork oil
-some 10mm ID washers as lateral shims for lower shock mount
-fork preload spacers (will use ABS or PVC pipe)


Total invested so far ~$380 (not including $60 for 2 spare shocks)


Cost comparison for premium drop in kits: ~$1600

Andreani Cartridges: $750 (~$800 w/tax & shipping)
Ohlins KT303 or JRi: $750 (~$800 w/tax & shipping)


Once the parts arrive, I'll update the thread...:D
 
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Formula390

Supporting Vendor
Vendor
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Wow you aren't kidding! That shock looks brand new! That was one heck of a deal even with the cost of all three shocks.
 

AirRsq

New Member
Wow you aren't kidding! That shock looks brand new! That was one heck of a deal even with the cost of all three shocks.

It was a great deal. The bumper still feels good, not dried out, so I'm hoping the internal seals are fresh enough for some abuse too.



As an aside, I put a zip tie on my forks and went for a hard ride yesterday to see how much travel I am using. Answer: ALL OF IT! I read that you get all but about 44mm of inner tube showing at full stroke. The top of my zip tie is at 44mm from the cast lowers after some intentionally hard braking. Haha! I guess that fork spring upgrade is clearly necessary.
 

Hekimpd

New Member
You are on the same budget as me. . I'll be watching your post intently. Thanks a ton for providing the info.
 

Treachery

Moderator
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Yeah, I'm subbing in for the fork info. Might be helpful for reference if you can list your geared-up weight, to let those of higher or lower tonnage know what springs to consider.
 

AirRsq

New Member
Yeah, I'm subbing in for the fork info. Might be helpful for reference if you can list your geared-up weight, to let those of higher or lower tonnage know what springs to consider.

Good point. I'm #200 w/o gear. ~#220 with.

Keep in mind that I have not confirmed that the 11.6 rear and 0.95 fronts are ideal yet, though others' research suggests so.
 

psych0hans

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I just paid up for a set of RC8 forks and Brembo Calipers. Will post updates when I get them. Jokerio has already done this mod with good results. Will post my opinion as soon as I get them.
 

Rexbo

Member
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Nice! I ask because over the course of playing with suspension settings, it may be beneficial to raise rear ride height when possible for clearance, but not too much so that the head angle (which is already steep) is changed too much.
 
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