My rear suspension upgrade - Honda CTX700 Forum
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post #1 of 14 (permalink) Old 02-17-2019, 05:56 PM Thread Starter
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My rear suspension upgrade

Model 2014 CTX700D DCT
Bought used in the fall with ~8k miles
Rider weight with really really heavy gear, > 250 (my gear is really heavy)

Coming from a Majesty (400cc scooter), I was hoping for significantly improved suspension over the scooter style CVT mounted on the swing arm. As I quickly experienced, the suspension was way too soft, and even cranking preload to the max didn't change the harsh ride. I was considering the Gonzo mod, and luckily picked up what looked like almost a brand new 2016 shock, with linkage for about $60 on ebay. One thing I noticed right away was that the new shock had more threading, which would allow more preload out of the box.

But more reading on the topic slowly dissuaded me from this approach. I came to the conclusion that I would need a different spring, at the least. Much better mechanics than myself were able to change the spring, but it would require some fabrication that was well out of my abilities.

I looked around and found the penske and ohlins options, which were still out of my price range. But extending the search to overseas vendors and including shocks designed for the NC700S, dramatically increased available choices, including Mupo, Hyperpro, Hagon and YSS. The cheapest option was YSS. One thing that gave me some comfort with the YSS is that it is well documented online. This made it relatively easy to find all the models and specs and opened up some more choices. More importantly, I knew what kind of spring it would come with and it was pretty simple to buy drop in replacements with all sorts of different rates. Someone with more experience would know which spring they could drop in as a replacement and where to get them.

The shock itself was compression rebound and height adjustable out of the box. The height adjustment was important and allowed me to settle on the model that was designed for the NC750X which I could shorten by 5mm to 300mm at the shortest. That's less than 5mm longer than stock, which I figured wouldn't result in too high a seat heigh, or require a new kick stand. I found the YSS for $275 plus about $50 in shipping. That was an investment I was comfortable with.

I think I got this next part right. But here's the data I collected. The YSS springs are spec'd in N/mm and this shock came with a 150 n/mm spring. That translates to 856 lb/in. According to RaceTech, the OEM spring on the CTX are 18.98 kg/mm. That translates to 1063 lb/in. Since my "gear" is so heavy, I guesstimated I'd need a much heavier spring. I found another YSS spring with the same length and width with a 265 N/mm. According the online calc I found, that spring was approximately 1400 lb/in. That seemed right to me.

Now changing the spring seemed like it was potentially one of the more challenging aspects of the job. I won't delve into all the detail of attempting to use a spring compressor I found on amazon, or the ratchet method I had seen on some Youtube videos. What I realized after some trial and error was that all I needed to do was back off the preload until the spring cap came loose on its own. That's kind of big deal with regards to the design of the shock, and I'm a little surprised that its not marketed a little more clearly. Basically, you don't need anything special to change the spring, just unscrew the preload until the cap slides off.

Another selling point of the YSS is that the preload is adjusted with a better mechanism that the two nuts requiring a spanner. There's one nut, and you can insert the 8mm steel bar directly into the nut to tighten. It's much much easier than the pair of nuts that need to be whacked with a screwdriver.

Anyway, the result is that my static sag is approx 17mm, and my rider sag is about 37mm right now.

Next up are the forks.
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post #2 of 14 (permalink) Old 02-18-2019, 08:21 AM
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I'd really like to see some pics.
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post #3 of 14 (permalink) Old 02-18-2019, 12:24 PM
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Someone else went with a custom Penske but if your serious about keeping this bike I highly recommend changing the rear shock out, your spine will thank you and so will your pillion.

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post #4 of 14 (permalink) Old 02-18-2019, 05:36 PM Thread Starter
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Pictures

Apologies. I should have take some side by side photos but I get tunnel vision when I start working on things.

Something I forgot to mention about the YSS shock is that the free travel of the piston, before it hits the bushing is about 46mm. On the stock shock, I measured 28mm.

Some other numbers. I measure about 16mm of preload threads on the '14 shock while the '16 had about 19mm.
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File Type: jpg rearshock1.jpg (106.2 KB, 15 views)
File Type: jpg rearshock2.jpg (104.6 KB, 12 views)
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post #5 of 14 (permalink) Old 02-18-2019, 09:29 PM
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Josh..... i’m Coming back for a long term review around August..... I’m really interested in this......

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post #6 of 14 (permalink) Old 02-19-2019, 02:52 AM
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Josh?
Could you post part nos.?
Thanks.
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post #7 of 14 (permalink) Old 02-24-2019, 08:23 PM Thread Starter
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Quote:
Originally Posted by dyenfd View Post
Josh?
Could you post part nos.?
Thanks.
I ended up installing the MZ456-305TRL-34.

It's a drop in replacement except that its a little taller than the stock. This shock is adjustable between 300-310 mm. The stock is measured at 296-297 mm. The spring is rated at 150 N/mm.

After purchasing, I found this on the YSS site: MZ456-300TRL-48

It is height adjustable between 295-305mm and it comes with a 200 N/mm spring instead of the 150. But I didn't find a supplier for this model.
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post #8 of 14 (permalink) Old 06-01-2019, 09:08 PM
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Did these shocks improve your ride on the bike?

Would you purchase the ones that you ended up buying again?

If not, is there one that you would think to use now?
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post #9 of 14 (permalink) Old 06-20-2019, 06:01 PM
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Thank you Josh for the rear suspension post / idea back in February. Back in mid-May, I ordered the YSS MZ 456-300 TRL-48 myself. Finally got it in from UPS today.

Anyways, I figure I post a couple pictures of the shock out of the box so if someone is also interested they have close ups of the top / bottom of the shock assembly and adjustments.
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post #10 of 14 (permalink) Old 06-20-2019, 10:51 PM
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Quote:
Originally Posted by quotronsystems View Post
Thank you Josh for the rear suspension post / idea back in February. Back in mid-May, I ordered the YSS MZ 456-300 TRL-48 myself. Finally got it in from UPS today.

Anyways, I figure I post a couple pictures of the shock out of the box so if someone is also interested they have close ups of the top / bottom of the shock assembly and adjustments.
What supplier were you able to source this one from? Im having a heck of time finding this model.

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