Spring pre-load 13-18 rear shock? - ZX6R Forum
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post #1 of 18 Old 06-14-2019, 05:35 PM Thread Starter
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Spring pre-load 13-18 rear shock?

I bought a used shock off of eBay, and wanted to adjust it prior to going through the process of mounting it on my '09. At 62K miles, the '09 shock hasn't got a lot of damping left.

As I don't have the shop manual for the next gen on my PC, and would prefer not to have to download the whole thing for the one piece of info I want, I thought I would put it to the membership.

The numbers straight out of the '09 manual:

Spring Preload Setting
Standard: Spring length 179 mm (7.05 in.)
Usable Range: Spring length 179 ∼ 190 mm (7.05 ∼
7.48 in.)

This shock that I purchased was set out around 8.5 inches --- I need to know if the next gen shock is that much different than my '09. I have cranked on the spring preload, to get it down to 7.5", don't know if there are enough threads on the adjuster to get it to 7.05.

"Basic stuff fellas. Use your head for something other than to break your next fall."
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post #2 of 18 Old 06-14-2019, 06:02 PM
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The 13+ shocks have a longer spring compared to the 09-12 that had a spacer collar on the bottom.

Best way to properly set sag is with measurements on and off the bike (read more here and here) but stock length is 205mm with usable range of 199-209mm

Rebound is 1 and 1/2 turns out and compression is 2 and 1/2 turns out.

---

I also forgot to mention that the spring is softer so you might have to adjust accordingly.
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Last edited by jd41; 06-14-2019 at 06:07 PM. Reason: links
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post #3 of 18 Old 06-15-2019, 07:08 AM Thread Starter
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Originally Posted by jd41 View Post
The 13+ shocks have a longer spring compared to the 09-12 that had a spacer collar on the bottom.

Best way to properly set sag is with measurements on and off the bike (read more here and here) but stock length is 205mm with usable range of 199-209mm

Rebound is 1 and 1/2 turns out and compression is 2 and 1/2 turns out.

---

I also forgot to mention that the spring is softer so you might have to adjust accordingly.

Thanks. I figure I will start out at the OEM settings, and adjust from there.

Like everything I've done on this bike, it's turned into more of a cluster f*ck than I was expecting. I managed to lose my 3/8" metric sockets, in my own garage. All of them. On a stick. Had to buy another set from an autoparts store. Finally got them and set up top do this this weekend......

Then my wife had a medical issue at the dentist, which is 30 miles from the house. I had to leave the bike there overnight so I could drive her home. That's cascading into no time to work on the bike this weekend, unless I fight for the time.

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post #4 of 18 Old 06-16-2019, 04:29 PM Thread Starter
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So I managed to swap the shock today. Tank, seat, exhaust after the header, rear wheel, chain guard, left foot peg carrier...... THEN you can support the chassis so you can remove the dog bone, then the shock.

Did I mention it was 90+* in there?

The replacement is installed, I chose to retain the shim from my '09 shock in place of the much thinner part from the later model. Set the spring pre-load at 8" , rather than the 8.5" it was at when I received it. Haven't checked any of the other adjustments.... Presuming they're at the OEM settings for now.

I've had to stop and cool off multiple times in the process. Soaked multiple tee shirts through with sweat.

The only remaining task is to mount the seat and clean up the bike. Should be done with that this evening.

It looks like much of next week will be rainy. Hoping to get in a ride asap to assess.

"Basic stuff fellas. Use your head for something other than to break your next fall."
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post #5 of 18 Old 06-20-2019, 05:10 AM Thread Starter
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So I took the bike to work this morning..... definitely an improvement over the sacked out 60K mile, '09 unit. Less jitter, smoother flow to the whole bike. I may soften the spring preload some from what I decided to dial in before I installed it to see if that gets me even closer to where I would like to be.

Happy with the $57 purchase. Compliments all the time and effort on the fork well.
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post #6 of 18 Old 06-20-2019, 09:06 AM Thread Starter
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Follow on question relating settings....

What is the cross over point between high and low speed compression?

I think of it in terms of hitting a rock or pothole, compared to undulations in pavement.... that sudden sharp change in wheel position relative to the chassis would be a high speed change, where dips and bumps in pavement that cover many feet of road would take (relatively) a much longer time to cause a change in suspension position.

Do I have that right?

Do I want to set high speed to be more restrictive, or less? Looking to have the chassis remain stable as much as possible. If the high speed can stop movement altogether, I want less, so it moves freely on a big 'hit'...... if all it does is dampen out SOME of the motion, then I may want more to reduce the amount that big hit can move the swingarm. Turn the high speed part into heat, and let the low speed circuit deal with the remaining energy of the motion.

In my head, I envision the high speed compression valving being installed as part of the low speed assembly -- sort of a check valve riding on top of a check valve. The high speed part would have a smaller orfice and a stiffer spring assembly so that it simply rides on the low speed assembly until a sudden sharp pulse kicks it open and lets that energy bleed avway faster than the low speed circuit would allow. It can react faster, up to a point.

Jack it up hard/fast enough, and the small orfice can't allow all of the fluid through, and the low speed circuit will start to act on it as well. As soon as the low speed circuit opens, that high speed circuit shuts, and you carry it the rest of the way through on the low speed circuit.

Does this seem right?

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post #7 of 18 Old 06-20-2019, 10:15 AM
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Quote:
Originally Posted by RJ2112 View Post
Set the spring pre-load at 8" , rather than the 8.5" it was at when I received it. Haven't checked any of the other adjustments.... Presuming they're at the OEM settings for now.
Set sag and check the clickers first, you have no idea what a PO did with it.


Quote:
Originally Posted by RJ2112 View Post
What is the cross over point between high and low speed compression?

I think of it in terms of hitting a rock or pothole, compared to undulations in pavement.... that sudden sharp change in wheel position relative to the chassis would be a high speed change, where dips and bumps in pavement that cover many feet of road would take (relatively) a much longer time to cause a change in suspension position.

Do I have that right?
Yes, you have that correct. 'High speed' and 'low speed' refer to the shock shaft movement, not the road speed.

Low speed compression is feel, the stiffer it is the more road feel you get. Low speed also affects chassis attitude some by tending to keep the bike higher or letting it settle some depending on the setting. High speed is how it blows off over big hits. You want enough high speed damping to prevent bottoming but not so much that it really hammers you over bumps. Both are mostly rider preference as long as you aren't bottoming all the time or skittering over bumps with no compliance.

Because most of this is rider preference, the only way I know of to set them is to do some testing. Set both adjustments in the middle of the range and ride it to see how it feels. Then change one setting at a time and ride it to see how it changed. I would suggest making these exploratory changes fairly large to get a very noticeable effect. Once you have went harder and softer with both settings then return to the middle and work each one towards what feels good for you. Keep notes so you don't get lost and never, ever change two things at once.

Don't forget to also do this with the rebound damping as well. Overall I would say rebound has more profound effects on how the chassis works as it controls packing through bumps and traction over bumps (assuming your compression damping isn't cranked to the point where it skips over bumps).


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post #8 of 18 Old 06-20-2019, 11:07 AM Thread Starter
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Definitely a [email protected] shoot on the settings..... I know they could be anything at all; and can tell that they aren't far removed from 'normal', if at all. I will set them to factory, and work from there over time.

Spring pre-load, I took a chance on setting it harder than OEM. I weigh ~210 lbs before gear, and knew this spring is softer than the one from my '09 shock. Setting it harder than baseline didn't seem unreasonable. You're right, the correct approach would be to set the static sag and go from there.

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post #9 of 18 Old 06-20-2019, 11:42 AM
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Rebound is the most noticeable setting. I would start with that. Not enough and it'll feel twitchy, too much and you'll get understeer.

https://lifeatlean.com/teach-me-susp...g-adjustments/
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post #10 of 18 Old 06-20-2019, 01:38 PM
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Here's a good tuning resource from Penske: https://www.penskeshocks.com/wp-cont...ning-guide.pdf
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post #11 of 18 Old 06-21-2019, 03:01 AM
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I'm 160lbs with gear- the shock on my 15 I set preload with 6-7mm thread showing above collar ..... even then it's got too much rebound dampening at 1 1/2 turns out- spring is on the soft side. Rebound I run 2 to 2 1/2 turns out, compression at 1 3/4 out to get 27mm rider sag (stiction took into account). Idk about the 09-12 models, but for track use sport rider (I believe) recommended a 8mm shim above the shock on 13-18 models. Raises seat height 15mm. Note that is for track use. Not sure how that shock would balance well with those forks (assuming stock of course). Without a shim, where mine's set tail can lift maybe 3mm before the tires no longer touching pavement.... the more preload, the more top out decreases.
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post #12 of 18 Old 06-21-2019, 09:30 AM
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Here's another good resource: Suspension Guide

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post #13 of 18 Old 06-22-2019, 12:52 PM Thread Starter
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I've been adding a bit of compression, to go with the rebound adjustments on the fork; took another couple of clicks of spring preload out, as the very small remaining amount of jitter I was feeling seemed to be coming from the front.

Seems to be doing the trick, chassis is staying stable, but the suspension is erasing almost all of the minor bumps and stuff. No wallowing at all.

Every time I make the suspension behave more in the manner I want I have to re-calibrate my perception of speed. What the bike used to feel like at 45-60 it simply doesn't feel like any more. Somewhere around 80 or so, the engine vibration is similar enough that it's easy to tell when I am passing through that range; but the quality of the ride is considerably more in line with what I have wanted since I bought this bike.

I don't have to think about the suspension. I am not concerned with traction. I can concentrate on the ride, and the environment.

* on top of all that, my wife found my stick of sockets for me. A few months ago, we broke down the furniture our son had been using until he moved out and I had used my sockets to break down the bed frame. Seems I left them in the room when I carried out the parts of the bed frame. Nice to have those sockets back -- I bought those in 1984.
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post #14 of 18 Old 06-24-2019, 07:20 PM Thread Starter
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Quote:
Originally Posted by batcycle636 View Post
I'm 160lbs with gear- the shock on my 15 I set preload with 6-7mm thread showing above collar ..... even then it's got too much rebound dampening at 1 1/2 turns out- spring is on the soft side. Rebound I run 2 to 2 1/2 turns out, compression at 1 3/4 out to get 27mm rider sag (stiction took into account). Idk about the 09-12 models, but for track use sport rider (I believe) recommended a 8mm shim above the shock on 13-18 models. Raises seat height 15mm. Note that is for track use. Not sure how that shock would balance well with those forks (assuming stock of course). Without a shim, where mine's set tail can lift maybe 3mm before the tires no longer touching pavement.... the more preload, the more top out decreases.
I took a look at the shock I mounted up...... It doesn't seem to have a high speed compression adjuster. am I missing something?

My '09 OEM shock has a set screw for low speed centered in a bolt face which is the high speed compression adjuster. Both of which are within a larger cap which is ~13/16" .

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post #15 of 18 Old 06-30-2019, 07:41 PM
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No high speed compression adjuster on the 2013 through 18's. Less internals to drop weight although that's the one thing I wish they would've kept. I'll hopefully be seeing Ohlins in my near future.
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