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The cold is here, and I can finally afford some down time on my 1050 Sprint ST. I can finally deal with my over-sprung front-end.

I purchased the 1.0 kg/mm spring from racetech + 10W Kawasaki Fork Oil. No; I did not re-valve it. My weight is 180LB; and this spring is perfect for perfect pavement, and race track, or somebody weighing a bit over 220 LB. With a full tank of gas its a charm to ride on chapped pavement.

Do I buy the valve kit?
Do I bite it, and buy 0.90kg/mm springs plus or minus the valve kit?
Do I try to play with lover viscosity oil?
or, do I go back to stock and play with oil viscosity?

Oh, I have the 6piston TOKICO calipers, and 1 kg/mm really keeps the bike from nose diving. At least i fixed one problem.
 

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A shim kit will be needed in order to slow down the stronger spring. The stock shims are on the soft side. Both compression and rebound will need to have one to three large shims added. .15mm X 17mm. Note that you may find a .30mm x 17mm in the kit. Consider that as two.

The stock valves are fine and don't need replacing. You should have plenty of aluminum spacer tubing (supplied with springs)for preload to play with.

If you have more than 20,000 miles on it you should consider replacing the inner and outer fork bushing. It's copper with a teflon sleeve. Fork seals are also recommended. They are cheapest through Racetech.

The amount of shims added depends on how aggressive you ride. If you choose to add shims you will need a inch pound torque wrench, a 6mm x 4inch allen with 3/8 or 1/2 drive and a impact wrench.

Best of luck
 

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Before doing anything else I suggest that you take a more scientific approach to resolving your suspension issues.

Firstly, the fork springs should be using around 90% of their travel in your normal riding environment. From memory the front suspension travel is 120mm, therefore you should be using roughly 110mm of the available travel. You can determine this easily by fitting a cable tie around the fork leg.

Secondly, you need to define what your damping issues are. Have a read of this link http://www.ohlins.com/Motorcycle/Settingupyourbike/tabid/59/Default.aspx

Once you have determined if the spring rate is OK, and know what damping issues are, then you have a base to determine what direction you should take with springs, shims or different oils.

Good luck
 

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Katana, Tell me more about slowing down the springs. I just installed a set in my s3 and thought the shims were for preload if needed.
Thanks,Albert
 

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Sorry to be a pedantic pain in the butt, but there's a bit more to it than a rule of thumb which says that using 90% of the available travel will determine that the spring is right... Oil height will drastically affect this and so will damping to a lesser degree.

There's only one way that's universally recognised by almost all reputable suspension tuners and that's to get the sag right...

See this for the good oil.

And yes, Ralphus is spot on with the good old cable tie trick - probably most useful for fine tuning oil height once you get your spring rates right.

Damping / valving - that's a whole 'nother story but there's a good thread a while back here as well as some comments from Katana Boy...

For my money, unless you have lots of spare hours just pay someone to do the valving mods provided they have some sort of track record with the Sprint...

Good Luck,
Muz
 

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Sorry to be a pedantic pain in the butt, but there's a bit more to it than a rule of thumb which says that using 90% of the available travel will determine that the spring is right... Oil height will drastically affect this and so will damping to a lesser degree.

There's only one way that's universally recognised by almost all reputable suspension tuners and that's to get the sag right...
Muz

You are right, oil height can impact on travel particularly if the height is less than standard because of the air spring effect and potential for hydraulic lock up. Generally most manufacturers make the oil height the same as the fork travel.

You are also correct about the sag. That should be done first before messing around with any other setting. That is why I pointed Alfa toward the Ohlins set up page.

but

It is still possible to have the sag set correctly and have the forks bottom out if the spring rate is too soft. That is why rules of thumb such as the 90% concept are used. It is assumed that this rule of thumb is applied when the oil height is set to standard. Playing around oil heights will obviously impact on this.

Sonic Springs and Racetech both have fork spring rate calculators on their websites that will help get people in the ball park. These fork spring calculators are generally based on sports bikes that typically have 20mm less travel than a sports tourer such as the Sprint. This should be also be considered when selecting fork spring rates.

The main reason people reduce oil height is to increase the air spring effect because they don't have anymore travel to play with hence their only options are to change to a stiffer spring or reduce the oil height. Seals are also more prone to leaking where oil heights have been reduced because of the extra pressure exerted on them.
 

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astar,
The speed at which the forks compress and rebound is controlled by oil passing through slots and holes via flexible metal shims. They slow down the quick rebound of a spring. Remove the shims and you have a pogo stick. With a strong spring you will feel more of the roads imperfections and will tend to rebound quicker. Less prone to nose dive during hard braking.

The aluminum tubing that came with your springs is used for setting up preload. They are cut for spacers. Preload is used to adjust static sag.

Read the info from the links the others have suggested.
If you need more help, PM me and I'll fax you the shim data tables and other helpful info.

All of this really depends on what you want from your bike and your level of skill. If your cornering technique is consistent and you are sensitive to the changes that small adjustments make, then setup is much easier. A properly setup bike can improve your riding. It also depends on how much your willing to spend.
 

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Astar

I suspect the shims you are referring to are probably washers which are sometimes supplied with springs in case you cut the spacers too short and need a little more adjustment.

The shims Katana boy is referring to are flexible units for altering the damping characteristics.

Cheers

Ralph
 

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It is still possible to have the sag set correctly and have the forks bottom out if the spring rate is too soft. That is why rules of thumb such as the 90% concept are used. It is assumed that this rule of thumb is applied when the oil height is set to standard. Playing around oil heights will obviously impact on this.
I'll concede that it is possible but likely only in the case of an extremely aggressive rider. The two sag measurements (laden and unladen) take care of the rider and bike weight weights and will work superbly for 99.9% of us mere mortals.

Cheers & Beers,
Muz
 
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