New front fork springs...

[hikermikem]

So I finally replaced my Progressive fork springs with some Sonic straight rate ones on my Big Red...

Much, much improved!! The Progressive ones are no better than stock (IMO). The Sonics' give you more confidence in the corners; very planted feel - a bit stiff for sure, but prefered over the OEM squishee feel.

I also changed out the fork oil too when I made the switch - set the oil level to OEM spec with a 50/50 mix of 15/10 weight, so i guess that makes it a 12.5 weight oil.

Very pleased with the result, wish I changed it out sooner.

[Steve]

What rate did you get?

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[azr]

Good to know. I've got progressives in the 78' 1000 and have been wondering if Sonics are worth the upgrade.

[Phred]

I just put progressive springs on the front last weekend. A few years ago when rebuilding the bike I put progressive gas on the rear and liked them. But til I read this thread I had not heard of sonic as compared to progressive. Will have to look into this.

[hikermikem]

What rate did you get?

.

Followed the instructions on their site and it came out to: 1.0 kg/mm.

http://www.sonicsprings.com/catalog/calculate_spring_rate.php#calculate

That's what I bought - also followed the installation instructions in the box regarding spacer length for the preload & that seemed pretty much right on too. They even supply a length of sch 40 PVC pipe to cut for the spacers...

[mrbill5491]

Followed the instructions on their site and it came out to: 1.0 kg/mm.

http://www.sonicsprings.com/catalog/calculate_spring_rate.php#calculate

That's what I bought - also followed the installation instructions in the box regarding spacer length for the preload & that seemed pretty much right on too. They even supply a length of sch 40 PVC pipe to cut for the spacers...

You sure you got the 1.0 kg/mm? When I ordered my Sonic springs, mine came out as the 1.0 kg/mms as well and placed an order for those. Couple days later I got a call from Sonic, saying we don't make the 1.0 kg/mm for that bike 80/81 GS 1100E, only the .95 kg/mm, so I took those instead, been happy ever since.

[hikermikem]

You sure you got the 1.0 kg/mm? When I ordered my Sonic springs, mine came out as the 1.0 kg/mms as well and placed an order for those. Couple days later I got a call from Sonic, saying we don't make the 1.0 kg/mm for that bike 80/81 GS 1100E, only the .95 kg/mm, so I took those instead, been happy ever since.

I'll have to find the box and see if it haqs the spring rate on it... the packing slip I have says 1.0.

Either way, they work very well for me!

[bwringer]

If you're heavier than "average" (whatever "average" means to Progressive) straight rate springs with the correct rate will work a lot better.

Progressive springs are a big improvement over stock, but when I switched my GS from Progressive to Sonic straight rate springs, the difference was amazing. In everyday riding, the lack of brake dive is most noticeable, and the front end works so much better in the twisties now.