Sonic Springs

[toobrie]

Im thinkin of upgrading the fork springs and found Sonic Springs (www.sonicsprings.com).  They have a nice little calculator to help you figure what spring rate you need.  What I was wondering is, has anyone used these springs or heard anything about them.

Thanks

[robinm1]

I have never heard of sonic springs, but I pulled my springs out today, found it hard to believe, 12" of soft, single wound spring and 8" of spacer, what a joke, well in the shed was a set of forks off a GSX550, so I thought I better have a look at those springs, wipped them out, same diamator, progressivly wound and a decent length, a couple of 1" spacers provided me with an acceptable sag of 30mm, and job done, had a quick squirt up the street and back, feels good, a fork fix at no cost, thats the price I like to pay. My whole K2 is proving to be a bargain budget bike, brought as an insurance write off for NZ$650, cost NZ$670 to repair, reregister and fit new sport demons , a Kerker muffler, a TCP fairing. Thats NZ$1320.00 total, equal to around US$800, a bargain in anybodies language.

[pwalo]

My whole K2 is proving to be a bargain budget bike, brought as an insurance write off for NZ$650, cost NZ$670 to repair, reregister and fit new sport demons , a Kerker muffler, a TCP fairing. Thats NZ$1320.00 total, equal to around US$800, a bargain in anybodies language.

Another Kiiw! Yes the replacement fork springs make a huge improvement. I've got a K1, which has a much better front end than my 97E had. I haven't touhed the front end yet, although I've replaced the rear shock with a Hagon. I'd like to have a look at perhaps trying a constant rate spring with cartridge emulators this time around. Just have to find the money.

Your K2 sound like a real bargain.

[galahs]

Sonic Springs Details


http://www.sonicsprings.com





Straight Rate Springs available for the GS500 (prices in US $'s)

GS500 0.80kg/mm Sonic Springs       $79.95     If you weigh 85kg or less (185.022 lbs)

GS500 0.85 kg/mm Sonic Springs      $79.95     If you weigh 100kg or less (220.264 lbs)

GS500 0.90kg/mm Sonic Springs      $79.95     If you weigh 115kg or less (253.304 lbs)

GS500 0.95kg/mm Sonic Springs      $79.95     If you weigh 130kg or less (286.344 lbs)

GS500 1.00kg/mm Sonic Springs      $79.95     If you weigh over 130kg (+ 286.344 lbs)




Here is a reply from an email I sent to SonicSpring on behalf of the members at GSTwins about postage.

Graeme,

Thanks for the interest in us.
We do have springs in stock for the GS500, and we ship anywhere in the
world. Shipping costs are:
In the USA, $9.00
To Canada and Mexico, $15.00
To the rest of the world, $25.00

For the international orders we use the post office, it's my understanding
that that results in fewer surcharges and brokerage fees for the purchaser
than using UPS or FedEx would.
The Candanian orders typically take 5-10 days, Austalian and European ones
1-2 weeks. Every once in a while though an international order takes 3
weeks or so, I guess due to delays in customs.

Please feel free to post this on a forum or message board if you feel it
would be interest, and let me know if you have any other questions.

Thanks again,
Rich Desmond

Another funny thing was the stock GS500's spring rate of 0.6kg/mm, is suitable for a rider weighing just 25kg's!!! (55 lbs.)   

[galahs]

I will also post these helpfull tech articles they have on their site http://www.sonicsprings.com

Changing Springs and Oil in Damper Rod Forks

This guide is intended to be a supplement to the factory manual, not a replacement for it. The factory manual is needed for proper torque specs and for any bike-specific procedures. When in doubt, please consult a qualified professional mechanic.

The first requirement is to have all the weight off the front wheel. If you have a centerstand, put the bike on it and jack up under the engine, so that the front wheel is off the ground. If your bike doesn't have a centerstand, use a rear stand in conjunction with the type of front end stand that lifts from under the steering head.

1)Remove the calipers, front wheel, fender and anything else that's attached to the forks.

2)If you have standard handlebars, unbolt them from the top triple clamp and move them forward. No need to remove any of the grips, cables or wires. If you have clip-on style bars loosen the clip-on pinch bolt(s) and any bolts that hold them to the upper triple. If they can be pulled off the fork tube, do so.

From here, do one side at a time, and the order of events is important.

3) Back the preload adjuster, if any, all the way out. If the forks have air caps, bleed the pressure.
4) Loosen the top triple bolt.
5) Remove the fork cap. Careful, there's going to be some force from the spring preload trying to pop the cap up.
6) Loosen the bottom triple clamp bolts and slide the fork leg out.
7) Remove the spring, spacer and any washers.
Dump the old oil, pumping the fork leg while it's inverted to make sure you've got all of it out. Refill, making sure you pump the fork through it's full stroke a few times to get all the air out of the bottom of the fork.
9) Cut the spacers. (see Note A)
10) Set the fork oil level.(Level is defined as the distance between the top of the fork tube and the top of the oil in the tube, and is set with the spring and spacer out, forks collapsed. Because of the way it's measured, a smaller number means more oil.) A handy item for this is a turkey baster. Measure the desired distance from the tip up and mark that spot with a Sharpie or a piece of tape. Make sure that there's a little more oil than needed in the tube, then align the mark with the top of the fork tube and suck any excess out. Put in the new spring, the washer that came with it, the spacer and the stock washer, if any. (see Note B.)
11) Re-install, reverse order as disassembly. Just be careful when putting the fork cap back on, they're easy to cross-thread.
12) Double check all bolts, and make sure to pump up the front brake before riding.


NOTE A: Cutting spacers

The purpose of the spacers is to provide the proper amount of pre-load on the springs. In general, street bikes need about ¾" of pre-load, assuming that the spring rate is correct for the weight of the bike and rider. So the question is, how do we determine the right length for the spacer?
Take the fork cap, and if it has a pre-load adjustment, set it in the middle. Now measure the depth of the cap from the bottom to the base of the portion that sits against the top of the fork tube. Include any stock washer that will sit on top of the spacer. Basically we're measuring the length of the portion that fits inside the fork tube.
Say for example that this length is 2". If we cut the spacer so that with the spring, washer and spacer installed it came up flush with the top of the fork tube, when we installed the fork cap the spring would be compressed 2". Too much. So we need to cut the spacer shorter to get the proper pre-load. In this case 1 ¼" shorter. Easiest way to measure this is to put the spring, washer and uncut spacer in the extended fork leg. Mark the spacer tube even with the top of the fork tube. Pull the spacer out and measure 1 ¼" down from the mark. Mark and cut from that point. Now, when you put the spring, washer and spacer in, the top of the spacer should be 1 ¼" below the top of the fork tube. When the fork cap is installed, the 2" section inside the fork tube will compress the spring ¾". Voila, correct pre-load!! Just make sure you use the right numbers for you, not the ones in this example. Also, back the adjuster all the way back out before re-installing the fork cap, to make it easier to get the threads started. Re-set the adjuster to the middle position after everything is bolted back up.


NOTE B: Oil level

Oil level is difficult to give blanket advice on. Some bikes work best with the stock level, some benefit from less, others are better with more. A general rule is to set it fairly close to the amount of travel that the forks have. Most street bikes have 4.5 - 5 inches of travel, (about 115 - 130mm) so an oil level in that range works for most bikes. Some are different though; For example, the Kawasaki Concours uses a level of 150mm with our springs. If you have a question about your specific application, please e-mail us.

Straight-Rate Springs vs. Progressive Rate Springs

Over the last 20 years, one of the biggest changes in the aftermarket motorcycle suspension world has been the virtually complete switch from progressive rate springs to straight rate ones. I think it's safe to say that there's not a single reputable suspension tuner who advocates progressive springs. The question is why? What's the problem with a progressive rate? Why are straight rate springs better?


One of the problems is that bikes, street bikes anyway, just don't have enough travel to take advantage of progressive rates. The soft initial portion gets blown right through, leaving a limited amount of travel for the stiffer portion to deal with. This results in less compliance, less traction and a harsher ride. Another issue is damping; Damping rates, particularly rebound damping, need to be matched to the spring rate. With a progressive (i.e. variable) rate, that's impossible. Damping is always a compromise and a progressive rate just makes the balancing act that much more difficult. Adding to the problem is that modern forks actually have 2 spring mediums, the steel coil and the air trapped inside. The air is intrinsically a highly progressive spring. Adding a progressively wound steel spring to the mix is just making a bad situation worse.

Setting Sag on Street Bikes

Setting the amount of sag your suspension has is an important step in optimizing both the handling and the comfort of your bike. Unfortunately, there's a lot of confusion on the subject, so we'll try to keep things as simple and straightforward as possible. First off, what is sag, and why does it matter? Sag is the amount of suspension travel that is used up with the bike sitting still, with the rider and any luggage or passenger on the bike also. It matters because it governs how much of the available travel is used for bump absorption and how much extension is there to "fill in" as the bike travels over dips or pot holes. Having the right balance between these two is critical to performance, safety and comfort.

To measure sag you'll need at least one assistant, preferably two. First, measure the exposed section of the fork tube with the suspension fully extended. For standard forks this is the distance between the top of the wiper or dust seal and the bottom of the lower triple clamp. For inverted forks, measure from the seal to a convenient point on the tube. Write this number down. Next take the bike off the stands (This is important!! Do not measure sag with the bike on the stands!) and get on it. If you have a second assistant have him hold the bike upright while you assume your normal riding position. If not, hold the bike as vertical as possible with one foot, keeping as much weight as you can on the bike. Have the first assistant push down on the front end a little and slooooowly let the bike rise until it stops. Measure the exposed fork tube length and write it down. Now have him extend the front a bit and let it settle back down slooooowly. Measure the exposed fork tube length and write it down. Now average last two numbers and subtract them from the first, this is your total sag. An example:

First measurement: 5 ½" Second measurement: 4" Third measurement: 4 ½"

Average of second and third is 4 ¼", subtracting that from 5 ½" gives 1 ¼", or approximately 32mm of total sag.

This is right in our recommended range of 30-35mm for street bikes.

If you have too much sag, add some pre-load. If too little, take some pre-load out.

Preload - What does it do?

Preload is perhaps the most misunderstood facet of suspension tuning. Many people think that by adjusting preload that they are stiffening or softening their suspension. Nothing could be further from the truth. Adjusting preload does nothing to your spring rate. (technical explanation below). All it does is change your ride height and your sag. So, given that, what should you do with those adjusters on the forks?? Basically, just use them to set your sag correctly.

For more info on the procedure for that go to Setting Sag On Your Street Bike
(http://www.sonicsprings.com/catalog/setting_sag_street_tech_article.php)

You can also use preload to make small changes to the ride height. Generally it's better to move the fork tubes up or down in the triple clamps to accomplish this, but on some bikes that's not possible. In those cases a little compromising between the perfect sag and the perfect ride height may in order. Sag is important though, so don't go any more than 10mm in either direction.

Tech Note:
A little thought experiment.

Let's assume that we have a pair of fork springs, each with a rate of 50 lbs/inch. The pair then have a combined rate of 100 lbs/inch. That means that it takes 100 lbs. to compress the fork the first inch, another 100 lbs. for the second inch, (total of 200) and so on. Also assume that the bike and rider together place a 300 lb load on the front end. If the fork is assembled with zero preload then the springs will compress 3 inches and the fork will compress 3 inches total. How much additional force does it take to compress the next inch?? 100lbs. Now say we add an inch of preload. The first 100 lbs of bike weight don't cause the forks to move, the next 200 lbs. make it compress 2 inches. The spring though is still compressed 3 inches and it still takes 100 lbs of force to compress the next inch. Well, what about progressively wound springs, wouldn't preload matter there?? Nope, same theory applies. The fundamental concept is that the spring has to compress a certain total amount in order to support the weight of the bike, and it doesn't matter whether or not some of that initial compression is from preload.

If you've really thought this through you may be thinking, "Hmmm, the steel spring's not the only thing holding the bike up, there's also the air pressure inside the forks." That's true, but air is just a progressive spring, and combining it with the steel straight-rate spring doesn't have any magical effect.

[galahs]

For people wanting to know the exchange rate, check this great tool out...

http://www.x-rates.com/calculator.html

[werase643]

as a general rule....
you will probably be happiest with the 0.90 or 0.95 springs
anything less will be a waste of $
unless you are a 100 # bike jockey

[galahs]

According to all spring weight calculators I have seen, what you recommend would be too stiff for riders like myself who weigh under 80kg.

I hate how soft the current sprins are, but I don't want to super rock hard ride either. If it was for track use the stiffer springs would be better?

Just as I was about to order the 0.80kg/mm springs you have me confused now 

[werase643]

ok, lets try again....
i raced for several yrs.
i like the FE a little stiff
almost all springs sold by the major shock/fork service centers....for fat rich MERICANS....
run 90- 95
on farking guy puts a .90 in one leg and a .95 on the other
and different VIS oil in each leg also.......

i have only ridden a gs with a stock FE....a few times....back in the mid 90's

new suggestion.....
figure what you want....then go up 1 size

or ignore me, i'm ok with that also....your buck...your choice

[Alphamazing]

ok, lets try again....
i raced for several yrs.
i like the FE a little stiff
almost all springs sold by the major shock/fork service centers....for fat rich MERICANS....
run 90- 95
on farking guy puts a .90 in one leg and a .95 on the other
and different VIS oil in each leg also.......

i have only ridden a gs with a stock FE....a few times....back in the mid 90's

new suggestion.....
figure what you want....then go up 1 size

or ignore me, i'm ok with that also....your buck...your choice

My reccomended spring rate was .72 or .74 or so. I got the .8 because I'm a 100lb flyweight! 

[galahs]

ok, lets try again....
i raced for several yrs.
i like the FE a little stiff
almost all springs sold by the major shock/fork service centers....for fat rich MERICANS....
run 90- 95
on farking guy puts a .90 in one leg and a .95 on the other
and different VIS oil in each leg also.......

i have only ridden a gs with a stock FE....a few times....back in the mid 90's

new suggestion.....
figure what you want....then go up 1 size

or ignore me, i'm ok with that also....your buck...your choice

Definately your advice is welcome! Cheers 

[Straymonolith]

I was looking into Sonic Springs, too and trying to decide on a spring rate.
Since I weight about 140 lbs, they reccomend .80, but depending on the sort of riding it could go up to .85 to .90.
I hit the twisties pretty often and I'd like to be able to take it to the track sometime. But I also ride in the city and freeway almost daily.
So I'm thinking .80 or .85; any suggestions?

[galahs]

I think .80's would be fine for your weight, but maybe .85's would be better for resale? (as not many people are as light as yourself)

I weigh 75kg's and am thinking that 0.85mm/kg (though 0.80kg/mm are recommended) would be the way to go as it wouldn't be too harsh as the bike is mostly used for communting but would stiffen the bike up enough for better handling with stiffness to spare for heavier riders.

[galahs]

I just ordered my 0.85kg/mm springs.

Expect a full write up when I get them.

[hmmmnz]

My whole K2 is proving to be a bargain budget bike, brought as an insurance write off for NZ$650, cost NZ$670 to repair, reregister and fit new sport demons , a Kerker muffler, a TCP fairing. Thats NZ$1320.00 total, equal to around US$800, a bargain in anybodies language.

Another Kiiw! Yes the replacement fork springs make a huge improvement. I've got a K1, which has a much better front end than my 97E had. I haven't touhed the front end yet, although I've replaced the rear shock with a Hagon. I'd like to have a look at perhaps trying a constant rate spring with cartridge emulators this time around. Just have to find the money.

Your K2 sound like a real bargain.

good to see another couple of kiwis on here, i was beguinning to get lonley,
$1300 is pritty good for the bike thats for sure, i paid £500 in scotland for mine (about $1300nz) but mines a 95 but still runs well, although its time to do those front springs and damn seals

[galahs]

I recommund, progressuve, sonuc or racetuck sprungs.

They wull sort out yur suspensun fastur than u can say fush an chups. 

[leo]

I do the occasional track day and hit the canyons when I can. Is it worth it to change from my progressives to these? I'm 195 with gear and the front does seem to dive alot under hard braking. I also have 15 weight oil in there.

For the calculator on that site do we pick sport bike or sport touring bike?

[galahs]

For pure track use I'd be inclined to go with 0.95mm/kg for your weight but if you'r mixing it up with street driving a better compomise might be 0.90mm/kg.

[galahs]

I recieved my Sonic Springs by post the other day.

Cost me $150 Australian delivered from the USA (only took a week to get them    )


I have a 2000km round trip journey to complete on Tuesday/Wednesday so I am putting off their installation until after that. (Don't want to bugger up anything yet)


The 2 Springs came with a PVC Spacer, two washers and an instruction sheet (suplementary not comprehensive).

[Alphamazing]

If you haven't seen it already, here's my write up on how to change the springs and fork oil out

http://gstwins.com/gsboard/index.php?topic=25706.0

Should take about 2 to 3 hours. PM me for necessary torque specs.