sonic or race tech

[5speed]

I'm planning on replacing / upgrading my front springs when I do the seals and bushings.
Is there any significant difference between sonic and race tech?
I can get race tech's from fortnine but they don't have sonic's listed for my bike.
Actually sonic doesn't have fj's listed on their website but folks here have mentioned them in the threads I've read.

[Pat Conlon]

I don't know about Sonic, but I know Race Tech very well and they are good.
Race tech's spring steel is superior to oem.  Your stock spring rate in your '86 is 0.65kg/mm which, by today's standards, is much too light for a 550lb motorcycle. Japanese spring steel was not the best, even when it left the Iwata assembly line, and now, 35 years later, they are totally sacked out. Well past due for replacement.
However be advised, if you put heavier straight rate springs in your forks, you will need the proper valves to control them, unless you like riding a pogo stick. We have found that the oem damper rod forks won't cut it with heavy springs, the rebound is severe, to put it mildly. (yes, we've tried different weight fork oils)
Race tech makes their Cartridge Emulators and RPM also makes a fine product for your forks.

If you can't afford the valves, and just want new springs, I suggest progressive rate springs. They are a step up from the soft oem springs and don't seem to overload the FJ's oem damper rod forks like straight rate springs will.

https://www.progressivesuspension.com/product/1465/fork-spring-kit

Cheers

Pat

[5speed]

thanks for the info Pat.
I used the calculator on the race tech site and they came up with 1.4kg/mm based on my weight and riding style.
I have no intentions of pushing the bike to it's limits or road racing it so I'm wondering if those might be a bit to much.
progressive's sound more suited to me.

[Pat Conlon]

1.4kg/mm is too stiff. The heaviest fork spring I've seen for the FJ is 1.05kg/mm.
Progressive springs are ok, just a step up from stock.

1) Stock springs = suck.
2) Progressive springs = ok
3) Race tech emulators and heavier straight rate springs = better
4) RPM valves and straight rate springs = even better
5) YZF600 cartridge forks = very good.
6) GSXR or YZF or FZR or R-1 USD fork conversion = the best.

Besides, as we all know, FJ's with the USD forks gets the chicks  

[5speed]

1.4kg/mm is too stiff. The heaviest fork spring I've seen for the FJ is 1.05kg/mm.
Progressive springs are ok, just a step up from stock.

1) Stock springs = suck.
2) Progressive springs = ok
3) Race tech emulators and heavier straight rate springs = better
4) RPM valves and straight rate springs = even better
5) YZF600 cartridge forks = very good.
6) GSXR or YZF or FZR or R-1 USD fork conversion = the best.

Besides, as we all know, FJ's with the USD forks gets the chicks