Inquiry: RaceTech Rear Spring Length vs. Stock - Kawasaki ZX-10R.net
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post #1 of 14 Old 08-04-2007, 04:17 PM Thread Starter
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Inquiry: RaceTech Rear Spring Length vs. Stock

So after a few weeks of me forgetting to check, I finally remembered today. I measured the height of my bike vs. 2 others 07's in the showroom in several different ways and I consistently came up with my bike being an inch shorter.

I was wondering if anyone happens to know the difference in length between the stock and Racetech springs?

Some pointed out to me that my bike is awfully upright when on the kickstand and I didn't even realize it until they pointed out. Then it hit me that it did seem a bit "unstable" when parked and that's what got the ball rolling today.

I did buy the bike used so I checked the my bike, showroom bikes, and the Parts Diagrams and I can't see anything that would cause a drop in height? The only thing I think of that would cause this is a shorter spring? I did have to spin the pre-load adjuster to what seemed an abnormal amount just to take up the slack - which makes me think that it was indeed shorter but thanks to the ADD and lack of short term memory I can't remember how much shorter it was.

Should I just shim it and not worry about it?

Weird.

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post #2 of 14 Old 08-04-2007, 05:12 PM
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Was the spacer that came from the factory installed at the top of the shock?
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post #3 of 14 Old 08-04-2007, 05:20 PM Thread Starter
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Quote:
Originally Posted by brian0128 View Post
Was the spacer that came from the factory installed at the top of the shock?
Yup! Same as I saw on the 07's and the diagram.

I'm thinking the spring is definitely shorter... which surprised me a bit at first but Racetech tech support assured me it's normal.

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post #4 of 14 Old 08-04-2007, 07:18 PM
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So long as you have threads left on the shock body you should be able to wind the collar and spring up to get back to ride height, if you jack the bike up by the frame and not the swingarm you will probably find you have a lot of free droop and a loose spring.
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post #5 of 14 Old 08-04-2007, 08:57 PM Thread Starter
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Quote:
Originally Posted by FAF View Post
So long as you have threads left on the shock body you should be able to wind the collar and spring up to get back to ride height, if you jack the bike up by the frame and not the swingarm you will probably find you have a lot of free droop and a loose spring.
Interesting...

Yeah loose spring in the shock body was an initial problem I had which is why I'm sure the spring is shorter - just wasn't sure by how much. I had to thread down the preload nut almost 3/4" before the "slack" was taken up - and now with about 1.5" thread showing, I have the sag set to about 27mm. There's isn't much thread left to go before I run out of thread - maybe another 3/4" or so? (All the measurements are guesses by memory). I do have forks dropped about 4mm as well.

I guess I could give Racetech a call on Monday as well.

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post #6 of 14 Old 08-04-2007, 09:09 PM
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Once the spring is slightly pinched thats as far as you can go with the ride height adjustment as you have topped out the shock, if your sag is till low then you will have to start adding preload on the spring to bring the bike back up to static or a shim on top of the shock.

I presume you put put the spring on with the shock fully extended before you put it on the bike, if it wasnt fully extended then you will still have a loose spring under full droop.

It shouldnt make any difference if the spring is shorter as you will take up the slack with the adjuster, if the spring is softer then your sag will be lower.
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post #7 of 14 Old 08-04-2007, 11:03 PM Thread Starter
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Quote:
Originally Posted by FAF View Post
Once the spring is slightly pinched thats as far as you can go with the ride height adjustment as you have topped out the shock, if your sag is till low then you will have to start adding preload on the spring to bring the bike back up to static or a shim on top of the shock.
Didn't even think about that but it makes sense now. Fully extended is full extended.

Quote:
Originally Posted by FAF
I presume you put put the spring on with the shock fully extended before you put it on the bike, if it wasnt fully extended then you will still have a loose spring under full droop.
I'm pretty sure I fully extended the shock and pinched it down. But... Even if there was say and inch of slop with the spring being loose, wouldn't tightening down the pre-load that inch fully extend it? (Ignoring sag for the moment)

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post #8 of 14 Old 08-05-2007, 12:20 PM
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Yes it would extend it , what spring rate is your new spring ?

If I remember correctly the stock spring is 900 Lbs/inch and the motion ratio is about 3 to 1 , from wheel travel to shock travel , so basically with a 300lb load on the rear wheel the shock would compress 1 inch without any preload on the spring and your wheel would move 3 inches from droop.

If you added 1/2 inch of preload to the spring then you are adding 450lbs spring pressure or 150 at the back wheel and you would raise the bike 1.5 inches if the shock can extend that far.

Without knowing your spring rate it is hard to determine how much preload to add , obviously if you went with a softer spring then you would have to add more preload to get back to static ride height.

Nothing wrong with shorter springs , less weight.

Last edited by FAF; 08-05-2007 at 12:22 PM.
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post #9 of 14 Old 08-05-2007, 01:43 PM Thread Starter
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Quote:
Originally Posted by FAF View Post
Yes it would extend it , what spring rate is your new spring ?

If I remember correctly the stock spring is 900 Lbs/inch and the motion ratio is about 3 to 1 , from wheel travel to shock travel , so basically with a 300lb load on the rear wheel the shock would compress 1 inch without any preload on the spring and your wheel would move 3 inches from droop.

If you added 1/2 inch of preload to the spring then you are adding 450lbs spring pressure or 150 at the back wheel and you would raise the bike 1.5 inches if the shock can extend that far.

Without knowing your spring rate it is hard to determine how much preload to add , obviously if you went with a softer spring then you would have to add more preload to get back to static ride height.

Nothing wrong with shorter springs , less weight.
ADD kicking in again... I'm running Racetech's 58.2 x 178mm 10.7kg spring. I'm not exactly small in stature.

I just went out and measured it and I have 24mm of thread showing. I'll try and re-measure the sag sometime soon and see if I A) Did it properly and B) have some room to play. I may have carried a 1 and took the square root of something wrong along the way.

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post #10 of 14 Old 08-05-2007, 04:35 PM
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Sounds like you are on the right track and just need to add more preload until your sag numbers are correct.
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