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Stabilizing a Sur Ron X

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    Stabilizing a Sur Ron X

    I should say, the Sur Ron is probably some of the most fun I’ve ever had. But like any piece of machinery, you start to run into its limitations as time goes on. I love how nimble the bike is, but sometimes it feels like it's dancing on tiny ballerina's feet and it's getting to me.

    I’m a woods and trails rider. Mossy clay and roots, gravel, mud, hard pack, rocks, and a short stretch of road in between. I think I’m just shy of 200 miles on the bike so far. It was time to change out the back tire so I needed to do some considering about what my long term plans are.

    The stock tires just don’t roll over big maple roots or monster truck over rocks like I want them to. They’re also a bit harder than I’d prefer and get a bitch twitchy. Particularly for the clay and rocks of the uphill/downhill sections.

    I’d decided I wanted to try an 18/21 setup but no one had them in stock in the whole of the USA. Because of the 'rona presumably. So I ordered mine from Milk Racing and after fussing with FedEx about import paperwork for a week, got my parts.

    I bought the wheel set, a seat lift, and a peg drop kit. In the end, I modified the seat lift to be a seat extension. I like it much better that way. Except for the dead space and the battery lock support bracket I haven't made yet. ;)

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    I also found out that I had to have to trim off the outermost lug edges to get the 3” front included to stop rubbing on the RST forks. The rear is a 3.5” dished to the left by 4mm for chain clearance... as in no cutting necessary. Stinks I had to trim the front in the end...

    The good news is that it looks awesome and feels awesome. The bad news is that I can’t ride it until I get a new chain to match my 60T sprocket. Ordered a Niche branded one from Amazon and got an open box and dirty 106 linker in it, not my new 114.... ouch!!

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    All the best to you guys! I’ll check back in once this thing is ready to go! I have pegs, chain, rear fender, and a few other accessories in the mail.
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    Last edited by moarpower; 08-03-2021, 07:00 AM.

    Not a Sur-Ron owner here, but the 21/18 mod seems to be one of the most beneficial tweaks one can do on those once everything else is sorted out. I'm only a little bit leery of how the MTB DH forks will do long term. By that I mean even with the stock wheel sizes, I think even the best MTB DH forks are operating a little outside their envelope on a Sur-Ron if pushed by an aggressive, experienced dirt rider...especially someone used to sending it on a dirt motor.

    moarpower, I'm guessing you've measured your front tire clearance to the front fender/triple clamp. I mountain bike and dirt motor, and it was interesting to find that a normal 21" dirt motor, off road, tire/wheel setup is basically the same height as a 27.5 front MTB tire/wheel setup. The Killah fork accepts 27.5 MTB tires/wheels, so I'm guessing all should be OK.

    Good looking rig.


      I know bigger tires would make me feel a lot more secure in my footing as opposed to a 16" with a fatty like Charged Cycle Works sells. I've been feeling it out, learning the suspension, and testing how far I can push on occasion. It's top speed is a bit faster than it needs to be and I really have had no business going so fast in the woods. I'm looking for a mid to high 30 mph top speed with the 60T.

      As for the DH forks trying to do work above their pay grade... you're right. They are what keeps me from going faster or hitting harder. I've very much limited the amount of vertical air I've gotten. Horizontal is a whole different story lol.

      I didn't take any measurements because the guy was selling these as Sur Ron parts and 18/21's have been done before. He substituted a different front tire due to his own supply chain issues and it's just 1/8' too wide for the RST's on the outside edge of the outer lugs. I trimmed them this morning. The image just wouldn't upload from my phone because their system was too lazy to resize it.

      Thanks, it's a fun little thing. And a money pit. Lol
      Last edited by moarpower; 08-03-2021, 09:58 AM.


        Well, I'm at that stage where I'm considering living up to my username.

        I've put an additional 30 miles on it since doing all the upgrades. It handles like a larger motorcycle, no longer feeling like a fat 24" BMX on bath salts. Part of that change was giving up the top speed. And I do miss it. I think I top out around 30 mph now. Blah.

        At first I didn't like the Luna riser bars all that much. But I noticed that my wrists no longer hurt after longer rides so I've come around. A good amount of credit of dampening comes from the larger tires too. They just eat up all my stupidity where the stockies left little margin for error. And then the mountain-bike like bars battered my joints and tendons.

        I kind of miss the adrenaline of pushing a twitchy fast bike past its limits though...

        Soooooo I'm looking at a BAC4000 and Lite Speed battery. And wishing I had the cash to blow. ;)

        Edited: We are now about 50 miles into the upgrades. I retuned the suspension by repeatedly jumping as hard as I could on my regular trail, adjusting the forks to prevent bottoming out, and then retuning the rear to make it feel even. The compression and rebound are both turned pretty high/hard but it feels light on its feet again, especially with a full charge. I absolutely feel more comfortable wagging the tail when accelerating. With the lower pegs, rear-ward seat mounting, and wider, taller bars I feel more like I am in control of the bike, not just resting on top.
        Last edited by moarpower; 09-30-2021, 06:01 AM.