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-   -   New fork spring rate recommendations (https://www.sv-portal.com/forums/5-tweaking-tuning-tricking/73667-new-fork-spring-rate-recommendations.html)

tzk321 9th September 2020 06:58 PM

New fork spring rate recommendations
 
My 2003 SV1000N has ~52,000 miles. The fork springs are still within spec but since I'm running out of things to tweak I thought I might change them anyway.

According to Race-Tech the stock spring rate is 0.98 kg/mm
Race-Tech recommends a rate of 0.86 kg/mm and the closest available is 0.90 kg/mm.

I currently have the preload at the max with the stock springs. If I use the springs that they recommend won't I have too much sag?

Masta' C 9th September 2020 07:48 PM

You can pretty much ignore the stock rate they are reporting. Because the stock springs are progressive, the rate they provide is not a good indicator of how the straight rate springs will compare. Basically, the stock springs start at a rate much lower than 0.98 and then increase to somewhere around 0.98 as the spring fully compresses.

You'll actually find it easier to set correct sag with a proper straight-rate spring.

In your case, 0.90 would probably be the way to go.

Missing Link 9th September 2020 10:39 PM

How hefty are you ?

If you have been honest on the calculator, then .90 will be fine.
They will be stiff at first, but will soften up nicely..

If you haven't done springs before, the new ones will be shorter....
Meaning you will have to make a spacer to make the new setup the same length as an orignal oem spring...
I made a alloy spacer washer to do the job, sat under the plastic spacer tube.....

schmidt314 10th September 2020 08:11 PM

Quote:

Originally Posted by Missing Link (Post 1852328877)
How hefty are you ?



If you have been honest on the calculator, then .90 will be fine.

They will be stiff at first, but will soften up nicely..



If you haven't done springs before, the new ones will be shorter....

Meaning you will have to make a spacer to make the new setup the same length as an orignal oem spring...

I made a alloy spacer washer to do the job, sat under the plastic spacer tube.....



Why will they be stiff at first then soften up?
If the spring is collapsing or changing rate significantly, that to me would be a poorly engineered/manufactured spring.

-ms

Missing Link 10th September 2020 10:12 PM

Quote:

Originally Posted by schmidt314 (Post 1852328885)
Why will they be stiff at first then soften up?
If the spring is collapsing or changing rate significantly, that to me would be a poorly engineered/manufactured spring.

-ms

Just from experience.....after the first few rides they seem to become more compliant.....seat of the pants thing i spose.......wait....maybe thats were i go wrong....i am sitting on the triples ?

tzk321 19th September 2020 08:02 PM

Quote:

Originally Posted by Missing Link (Post 1852328877)
If you haven't done springs before, the new ones will be shorter....
Meaning you will have to make a spacer to make the new setup the same length as an

Should the new spring + spacer combination be equal to the stock spring + spacer length?

schmidt314 20th September 2020 12:45 AM

Quote:

Originally Posted by tzk321 (Post 1852329017)
Should the new spring + spacer combination be equal to the stock spring + spacer length?



In some cases yes, and some cases no.
-ms

tzk321 20th September 2020 01:11 AM

OK. What about in my case?

schmidt314 20th September 2020 06:28 AM

Quote:

Originally Posted by tzk321 (Post 1852329027)
OK. What about in my case?



My numbers show that with a 0.9kgf/mm spring with the preload adjusters backed all the way out, you need 12mm preload onto the spring when the cap is installed.
-ms

RecoilRob 20th September 2020 10:42 PM

I have .90 RaceTech springs and the stock spacers needed to be cut about an inch IIRC. Easy way to do it: have front end lifted off of ground with forks fully extended. Place spacers and caps with preload adjusters fully wound out and see how far you must compress the stack to get them to thread in. Stock spacers were WAY out needing a really hard effort to compress and get threads started...which is no good. Cut spacer until maybe 1/4" needs to be compressed to get the threads started and this will be about right. If you can't get your sag set properly...either cut more of the spacer or add washers to suit. Not hard and no real measuring needed....if you can compress the spring a bit to get the cap on it's going to be really close.

Missing Link 20th September 2020 10:48 PM

Quote:

Originally Posted by schmidt314 (Post 1852329029)
My numbers show that with a 0.9kgf/mm spring with the preload adjusters backed all the way out, you need 12mm preload onto the spring when the cap is installed.
-ms

I have 1.0kg springs in mine..... (gixxer front end) what should i be using spacer wise ? I just matched the spring/spacer combo.....had to cut the spacer down to
get that figure...

schmidt314 20th September 2020 11:13 PM

Quote:

Originally Posted by Missing Link (Post 1852329045)
I have 1.0kg springs in mine..... (gixxer front end) what should i be using spacer wise ? I just matched the spring/spacer combo.....had to cut the spacer down to

get that figure...



It depends on what front end. In most cases though on those forks if you buy the exact right spring, you use the stock spacers.
-ms

Missing Link 21st September 2020 07:04 AM

Yeah...i had a look on Racetech, they have 10mm as the preload.....

So, i measure the free length of the spring....270mm from memory, then with the preload adjuter right out, the spring should be compressed 10mm ?
If more, then the spcer is too long, or less, i need more spacer.... me thinks thats right, ya ?

Missing Link 21st September 2020 11:09 PM

1 Attachment(s)
....revisited the Racetech page....says 2 things.... see attached

Recommended Preload - Actual 10mm

Recommended Preload - Relaxed 30mm (click for details doesn't work)

Now, me wonders what it means, as they show sag as 35mm elsewhere....

I would email them, but, previous experience has taught me that the one word answers they give
dont inspire confidence or assurance.....

So, can someone shed some light please ?

tzk321 22nd September 2020 01:44 AM

What do they mean by actual and relaxed preload???


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