bevie wrote:
Hi phuk72,
I finally got the springs they are a bit shorter than the standard springs do I need to fit another spacer
at the moment there is a top washer spacer tube and bottom washer "not a spring seat"I have to screw adjusters in fully to get correst sag ,is this right.
Cheers Ian.
Hi Bevie
The starting point is to place the old spring, top and bottom washers and spacer on your bench to measure the 'free' or 'uninstalled' length. Do the same for the new spring and all the above bits. Cut a completely new spacer from fresh tube, either thin wall metal or PVC pipe, to give yourself the same starting point. This means the old and new springs will have the same 'installed' length ( the spring needs to be compressed slightly to get the fork cap to fit). The difference between the free and installed length should give the correct preload for the 'free' sag, if the spring rate is correct. I am surprised the springs came without new spacer tube or installation instructions.
As far as sag goes there are two types to consider- and the terminology is flexible at this point in the english speaking world. To measure both types of sag you will need to take a measurement of the fork fully extended- I use the dust scraper to the bottom triple clamp. From this you need to subtract the average measure of the point where the forks settle under load. First measure from letting the forks settle from full extention, then have your mate push down on the top clamp and let the bike rise up and settle. Averaging the two removes the effect of friction within the fork.
Type 1 is free sag ie the amount the forks compress from fully extended supporting the weight of the bike only. If the installed length and spring rate is in the ball park then the forks should compress 10-15mm under the weight of the bike ALONE. If you cannot get this figure by adjusting the preload adjusters at this point then you need to consider the spring rate is wrong*
Type 2 is static sag.. also called loaded sag or "race" sag. If the spring rate is correct and the figure for type 1 is met then when you hop on the bike with your riding gear on the forks should compress between 30 and 40mm fron fully extended ( not the free sag point) using the same measuring system as above. If it does go for a ride, your finished. If it doesnt ...
.....if you need to add preload from the setting that works for the free sag then the spring is slightly soft, if you need to back the preload off then the spring is slightly too stiff. If you can adjust the preload adjusters to give 30 to 40 mm static sag head off for a ride, job done.
If you cannot get the magic 30 to 40mm by winding the preload in to the max then the spring rate is too soft and NO AMOUNT OF FUTZING ABOUT WILL FIX IT. It will be good to remember at this point that spring rate has NO EFFECT on ride quality. Ride is a function of damping curves and preload. For example a too soft spring will rider harsher than a stiffer spring if it is over preloaded to set sag.
The same goes for the reverse, if you wind the preload adjuster out and it still gives less than 30mm the the spring is too hard and no amount of futzing will fix it
*unfortunatly progressive springs, IMHO, are a lazy companies attempt to make a one-size-fits all spring, rather than stock a range of springs for each bike/rider combo. A TRX weighs 200kg with a full tank of fuel. TRX riders would range from 60kg to 130kg without difficulty. The theory is that lightweight rider with progressives correctly preloaded would only use the lighter end of the progressives, and the heavyweight only the heavier rate. But by definition each rider will only use part of the suspension travel. With the correct rate selected for the riders weight the spring rate is useable through all of its travel, with obvious benefits to ride quality.
Another thing to consider is that rebound damping is directly related to spring rate. Set the damping to control a progressive springs extension from fully compressed and by the time the spring reaches its mid point it is over damped. Run over a set of ripples and the front end will pack down, ride gets harsh and here comes a headshake.
Set the rebound to work in the middle or soft end of the springs stroke and the fork will rebound fast from deep in its stroke and feel unsettled. Getting rebound is crucial for stability, grip and comfort. Progressives do not help the cause.
Hope this helps.... if it were me I would sent the things back and get some correctly weighted straight weight springs from a professional supplier. When you phone them they should ask #1 for what bike?, #2 how heavy are you? If not hang up.
DFH
Now with 140,000 on the clocks, X-mas tree didn't kill it & I still love it.
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