Fork seal rebuild considering 1.2 Sonic springs are they worth it?

[ST Gui]

Or possibly use the stock springs and devise an air boost (much easier to adjust) with a crossover/balance tube. Gas is the perfect spring.

That would be interesting to see. I put a similar system on my '77 GL1000. It was two fork caps with a common valve stem in one with both caps connected by a crossover tube. It also came with a large syringe mated to an air gauge. I seem to have a memory of the second cap having a small air pressure gauge mated to it but that may be just a glitch in the gray cells.

I'd have to top off the air every few weeks but the difference in ride and handling was an obvious improvement. I could still bottom the forks if I tried. So I didn't.

 

[Lowndes]

I still have a '77 CB750F2 with that kit on the tubes. S&W air shocks on the rear. Never could part with the old girl. It was true love from the very start, now she just rests. Still have the syringe pump, saw it the other day.

 

[ST Gui]

Still have the syringe pump, saw it the other day.

Your pics don't resolve though that may just be me. The GL is long gone but I still have the syringe too! And I wish I had the GL.

 

[fnmag]

I still have a '77 CB750F2 with that kit on the tubes. S&W air shocks on the rear. Never could part with the old girl. It was true love from the very start, now she just rests. Still have the syringe pump, saw it the other day.

The pics showed earlier but now they're in the ether.

 

[Lowndes]

Aaterysk,

I'm OK with the 1,2 springs. It's not worth going back in and swapping them. It feels very good to me like it is but others might not like the "sport" suspension. I've been running 38 & 40 psi in the tires but yesterday I found the sticker under the seat that recommends 42 & 42 psi. I'll try the 42/42 and see how that feels.

If I had it to do again I'd get the 1,1. Or possibly use the stock springs and devise an air boost (much easier to adjust) with a crossover/balance tube. Gas is the perfect spring.

I put 42/42 in the tires yesterday morning and rode up to Suches the long way, 19 over Neals Gap, and 180 in to Suches. I also discovered the rear preload twist grip was stuck in the max position, got it unstuck, and backed off two turns. This and the 42/42 made another noticeable improvement to the handling, too. Very crisp and precise now. It might not be for everyone but I really like it. It drags footpegs on both sides easily and confidently. This bike's handling is now on par with my '99 R1100RS with Wilburs on both ends. I'll measure the sags again to compare.

I never used to think about suspension on any bike I ever had. If it had springs I was good to go. But once I found out what good suspension and handling feels like, can't go back. Kinda like good beer, bourbon, and wine.

 

[4INer]

I currently doing a fork rebuild using sonic 1.1 with 7.5 weight oil and the forum recommended 125 mm of air space and cutting the spacers to 130 mm (5 1/8 inch). Any way after reassembly (new bushings, new backup ring, new oil seal, new oil lock new sealing washer new bottom Allen bolt, fork damper installed, oil serviced to 125 mm from top with fork tube compressed). Then dropped in the new spring followed by 1 of the 4 sonic washers, then a spacer cut to 130 mm. When I raise the fork tube to the top to measure preload, I have negative preload. Does anybody have a length measurement on the sonic 1.1 springs for an ST 1300? If they are the correct springs and 130 mm is the correct spacer length, I have something wrong but cat for the life of me see where I did anything wrong....

 

[4INer]

I got the 1.2 Sonic Springs installed and tried them out with a 230-mile ride in the N GA mountains Sat. The handling is MUCH improved, and this mod puts more emphasis on the S in the ST. The front end is now not the overly soft, mushy, sometimes unnerving response in curves that it used to be. Much more balanced and definitely firmer, but not excessively firm or harsh (for my taste). I was VERY pleased with the new handling.

My '06 ST only has 27K on it and was box-stock. The rear unit seems to be OK for now and no fork seals were leaking. I had first intended to just install the "drain tube" spacers described in other threads here. I even made the spacers from the "sink-drain tailpipe" as recommended but they look too thin and fragile. I made another set of spacers from 1" sched 40 PVC and devised a "no sweat" method to install them with a 6" gear puller. But then the Sonic Springs arrived and I decided to go with them.

After reading the instructions several times and measuring to make the spacers from the PVC supplied with the springs, it was apparent that the stock steel spacers were the correct length without additional spacers, so I decided to do a quick and easy spring replacement. I just put the bike on the center stand and did one fork tube at a time, no engine support needed. Pulled out the stock, progressive spring and measured the depth of the oil, sucked out all of the oil possible, and replaced it with 7.5 wt Maxima fork oil to the same depth. Then I dropped the Sonic spring in with the stock "bushing" and the stock steel tube spacer and replaced the cap.

It was a simple R&R except for the partial (80-90% ??) fluid change. Didn't have to remove any tupperware, the front wheel, loosen the triple clamps, or purge the air. This would be a 1-hour job the next time. $120 for the springs, $20 for too much fork oil, a torque wrench, a couple of end wrenches and Allen wrenches, and an old spray bottle pump. EZPZ.

The specs show the forks' full travel at 116.8mm. The sag with bike and rider measured 22.2mm, or 19% if my math is right.

The rear specs say 121mm full travel and the sag with bike and rider was 41.3mm or 33%.

So, the front is a little stiff and the rear is a little too soft, but the rear preload can be adjusted. Doing the static "saddle bounce", the compression and rebound dampening were very close being equal and optimal.

For anyone not needing to replace the fork seals but wanting to upgrade the handling substantially and easily this method would be an option.

So were your sonic springs the same length as the stock springs (250mm)? It seems to me that if folks are replacing the stock spring collar (spacer) which is 200 mm long with a sched 40 spacer that’s 130 mm long, the sonic spring should be in the 320-330 mm long range? Yet the springs that sonic sent me are the same 250 mm long as the oem spring.

 

[sgio]

I just did the 1.1 Sonic springs yesterday. I came to the same conclusion, that they must be shorter than they used to be as the 130mm spacer is way too short now. They were very close in length to the stock springs. I re-used the stock spacers, which gave me a little more than the recommended pre-load (in the Sonic instructions 15mm). Probably around 20mm Pre-load, but I didn't measure it.

 

[4INer]

I just did the 1.1 Sonic springs yesterday. I came to the same conclusion, that they must be shorter than they used to be as the 130mm spacer is way too short now. They were very close in length to the stock springs. I re-used the stock spacers, which gave me a little more than the recommended pre-load (in the Sonic instructions 15mm). Probably around 20mm Pre-load, but I didn't measure it.

Thanks for the response, I’m trying to contact them to confirm. They sent me a length of sched 40 to cut my own spacers, but even if I would have just cut it in half the spacers would have been too small. BTW, I tried using the Honda spacer and mine was slightly larger in diameter than the supplied washer and slid down over the washer and part way down the spring.... and if they’ve changed the length of their springs for the ST13, I guess I can throw out all the advice on oil weights and amount, and have to get recommendations for amount of preload for my 275 lbs.....

 

[Lowndes]

I put 1.2 Sonic springs in my '06 ST and used the OEM bushings and spacers. From my measurements - IF I did it correctly - BIG IF - the steel tube spacer was exactly the correct length for the 1.2 springs. Sorry, I did not keep the lengths. After several brisk rides through the mountains in N GA and being very pleased with the VERY much improved handling, I decided to soften up the front to better match the OEM Showa rear suspender cranked up to max (yes, I refilled the adjuster).

Several ways to do this, 1) shorten the spacer on the Sonics, 2) increase the spacer on the OEM springs, 3) install softer Sonic springs, 4) install an air booster system in the front with the OEM springs. After measuring the static sag and doing the math decided to make an air boost system for the front because it is infinitely variable and very easily adjustable even while out riding. Also, gas is a perfect spring. I'm in the middle of that now working out the clearances around the triple clamp and tapping the caps for the crossover, gauge, and Schrader.

I'm "only" 220 lbs dressed. If you find the 1.1 springs too soft or too much sag, I'd be interested in swapping the Sonics with you.