Sonic Springs Model 05-S100 dimensions for my '79 GS1000

[garyS-NJ]

I installed Sonic Springs model 05-S100 in my '79 GS1000 and the front end now seems very tall and very sprung. the front end is also now very harsh (highway bumps launch me) and sweeping highway turns with dips puts the bike into a snake weave.

I think I did preload correctly and I'm wondering if I received the wrong springs (too long). I must admit that I have old shocks on the rear and have not checked them disassembled but the sag in the rear seems right (good even on the lowest preload setting) and they seem to dampen when I bounce on them.

I'm planning to install the race tech emulators but Race Tech said these springs might be too long or might bind and also I'm just wondering if I would be putting good money on bad..

[Nessism]

How much preload did you put on the springs? Typically you want to cut the spacers so they are flush with the top of the stantions when the fork is fully extended.

[Steve]

Just as important, ... how much does the bike sag when you get on it? The amount of sag should equal about 20% of total spring travel. Most of our bikes have between 5 and 6 inches of travel, so you are looking for 1 to 1 1/4 inches of sag.

Another question, ... how much of what weight oil did you install? Did you measure oil height or simply drop in a given quantity?

.

[garyS-NJ]

Thanks for your response. I would think that I followed the instructions provided or on their website for preload.. But it was 2 years ago and the forks are assembled so I won't know until I open them up. I have a fairing on ther and getting a new headlight so plan to do the work in one fell swoop (buying race tech emulators and the headlight).

How much preload did you put on the springs? Typically you want to cut the spacers so they are flush with the top of the stantions when the fork is fully extended.

[garyS-NJ]

And thank you also Steve for responding.. right now I get zero sag when I sit on the bike which I now know sounds bizarre.. Thats' why something must be up. And as for the fork oil I believe I followed instructions to install the springs and with the forks fully extended add oil until a certain level. I used either 10 wt, or 15wt fork oil or might have mixed to get around 12 wt.

Just as important, ... how much does the bike sag when you get on it? The amount of sag should equal about 20% of total spring travel. Most of our bikes have between 5 and 6 inches of travel, so you are looking for 1 to 1 1/4 inches of sag.

Another question, ... how much of what weight oil did you install? Did you measure oil height or simply drop in a given quantity?

.

[salty_monk]

If you have no sag then you either have too much spring or too much preload.... In general the oil weight/height won't affect static sag much.

[garyS-NJ]

If you have no sag then you either have too much spring or too much preload.... In general the oil weight/height won't affect static sag much.

Thanks again on that, yes I know. I'm gonna pull the spacers and springs and hopefully Sonic responds with the free length perhaps they sent wrong springs. If they are long we on that might lock me into the race tech if i dont have room for an adapter with mikes emulator.

[Steve]

And as for the fork oil I believe I followed instructions to install the springs and with the forks fully extended add oil until a certain level. I used either 10 wt, or 15wt fork oil or might have mixed to get around 12 wt.

I don't know of anyone that specifies a fork level with the forks extended.
The Suzuki manual tells you to check the fluid level with the forks removed from the bike, spring removed, fork fully collapsed. There are some differences, but a level between 6 and 7 inches from the top of the tube usually works quite well.

Straight 10w oil should work quite well, no need to mix anything. However, more important than oil viscosity, what springs did you install? Spring choice would depend on your bike, your riding style and your personal gravitational attraction. The fact that you have a fairing on there might also affect your choice. The question would be: is it something small and light or a frame-mounted beast, like a Vetter Windjammer? A heavier fairing would justify a slightly stronger spring. As an example, for my 850, it was recommended to get a 0.9 or a 1.0 spring. My riding style is considerably less than "gung-ho", but my gravitational attraction is a bit above average, so the 1.0 was suggested. My bike also wears a fairing, but it's lighter than a Vetter, so I went with the 1.1 springs. I have NOT regretted that choice at all. I topped that off with the proper amount of 10w oil, my bike rides beautifully.

Thanks again on that, yes I know. I'm gonna pull the spacers and springs and hopefully Sonic responds with the free length perhaps they sent wrong springs. If they are long we on that might lock me into the race tech if i dont have room for an adapter with mikes emulator.

I have a suspicion that the springs are offered in different diameters for the different bikes, and there are different weights (strengths) available for each of those diameters, but they are all one length. Your ride height would be determined by the length of the spacer you install. As has been mentioned earlier in this thread, a good starting point for length selection is to hold the extended tube vertical, drop in the spring, then measure from the top of the spring to the top of the fork tube. Cut the spacer at that height.

I installed some emulators from Mike's XS, but you should be aware that they are only available in 35mm diameter, you have 37mm forks. I have some adapters that were made by another member of the forum. I don't know if he has geared up for any production runs, so I won't mention him by name, but I will contact him to have him check this thread.

I don't remember how much I had to cut from my spacers when I installed the emulators, but the process of determining spacer length is the same. Install emulators (with adapters), install spring, extend fork tube, measure to top.

.

[RichDesmond]

Gary, I forgot to put in the PM that the free length of the springs is 380mm. Really though that doesn’t matter if you cut the spacer correctly.
Concur that it sounds like too much preload.

[garyS-NJ]

fork oil measured with springs out and legs compressed

Thanks Rich and again Steve.

On the Sonic Spring length if the ones I pull out measure at 380 mm that should be way fine as the recommended racetech springs are 425mm long. So if the 425 mm springs can accommodate the approximate 35mm tall emulator and get not more then 1/2" preload with the fork caps then certainly the Sonic springs being shorter by 45mm should work fine.

As for my fork oil measurements, I read so much that I sometimes blur my memories.. I remember reading something about different springs having different sizes and volumes so they affect effective fork oil level.. But I found my sonic receipt paired with their instructions for fork oil measure which says collapsed no spring tubes out and vertical. I left my tubes in the trees so approximated the level for the tube angle.

And fairing now, I have a tiny chopped down ninja300 fairing on there like a futuristic café so no appreciable weight.. really seems like I preloaded too much spacer but i'd swear the spacer came out around 2".

hopefully the Mike's xs adapters are available else I'll get the race tech emulators and see about preload when I get them apart and verify that 380mm spring length...

[Tom R]

I’ve left the forks in the trees changing the oil in the past.... it’s much more important that they’re equal. The xs emulators certainly work, but I suspect the gold valves are higher quality.

[Grimly]

If you filled the forks with oil when extended, you've got a hydraulic lock.
Don't get any sag with one of them.

[RichDesmond]

...I left my tubes in the trees...

I always shudder when I see this. Chances of an error in the installation process go way up.
Shortcuts generally aren't...

[salty_monk]

Racetech Emulators are slightly taller than MikesXS ones from memory. With an adapter added the net is about the same. They work really well but it's really only a viable option if you have access to equipment or someone who can make you an adapter.....

I have had a few made over the years but it's not viable as a commercial exercise and as one or two off's it's very expensive, I'm still somewhat in a hole from the ones I made thus far to be honest.

I'm not sure why MikesXS doesn't offer an adapter themselves, it should be viable if you were controlling the supply of the base emulator. My worry is that to get the pricing right you'd need to lay out for too much volume & then if that emulator disappears or is changed you'd end up with a pile of scrap....

There was a member here who was going to try making them 3D printed but I never saw any more of it - my own thoughts are that most hobby machine materials probably won't stand up to the forces involved.

If we could get more than 25 members to sign up for a set I may be able to make it work but it's going to take time.

[Grimly]

If we could get more than 25 members to sign up for a set I may be able to make it work but it's going to take time.

Yes. Put my name down for a set.