Need Help Figuring out What Rear Springs to Purchase - SOLVED

[RustyTank]

Hi guys. I have a 1979 GS850G. I'm looking at getting new rear shocks, I have two questions.

1. How do I figure out the correct spring rate?

2. I'm looking at maybe getting a set of Progressive shocks through Z1 Enterprises. On their site you have to order the shock and the spring separately. Entering in my particular bike it looks like there's only two options for black springs, a 105/150 and a 90/130. I have no idea what these numbers mean. Can someone help explain this to me?

[Nessism]

How much do you weigh and do you carry a passenger and/or luggage and if so, how much?

[RustyTank]

How much do you weigh and do you carry a passenger and/or luggage and if so, how much?

I weigh 185 lbs, I do not carry a passenger.

If I have saddlebags on my bike it's for two reasons:
#1. I'm making a local grocery run, in which case the weight can be anywhere from 5 lbs to 30 lbs.
#2. I'm going on a camping trip, full saddlebags, tent, sleeping bag, etc. In which case the weight could be up to gosh...I don't know? What does all that $hit weigh? An extra 70 lbs or 80 lbs?

I'm guessing you get what I'm sayin though.

Does that help?

[Gorminrider]

FIRST why not try
"

Don't hesitate to contact us with any questions or requests !

" bottom of the home page...


You will want to read up on "sag" and have something to inform them with.......otherwise, 70# is just a small passenger. and will be ok just turning up the preload if needed.
(...I do believe springs are generally touted as # per inch. (or kg/mm). These you mention are "progressive" springs so perhaps that explains the two values eg 105/150Versus straight coils which have a single value. But ask them.)

[RustyTank]

FIRST why not try
"" bottom of the home page...


You will want to read up on "sag" and have something to inform them with.......otherwise, 70# is just a small passenger. and will be ok just turning up the preload if needed.
(...I do believe springs are generally touted as # per inch. (or kg/mm). These you mention are "progressive" springs so perhaps that explains the two values eg 105/150Versus straight coils which have a single value. But ask them.)

I have gotten ahold of Z1, with the same questions. I very much respect the knowledge from folks on this forum so I decided to make this post as well as email the folks at Z1.

Thanks for bringing up "sag". I'll look into it.

[Nessism]

90/130 would most likely be fine at your weight.

[Steve]

Entering in my particular bike it looks like there's only two options for black springs, a 105/150 and a 90/130. I have no idea what these numbers mean.

I weigh 185 lbs, I do not carry a passenger.

I also have an 850G, but it's more of a G"K". You can click on the link in my signature to see it.

I outweigh you by almost four stone. Add that to the weight of the extra 'stuff' on the bike, you will see it's quite a bit heavier than yours.

I don't carry a passenger very often.

I have KONI shocks, and just replaced my springs. The ones that came off were 100/185. The ones that went on are 123/218. I have not yet ridden with a passenger with the new springs, but I really do like the new spring rate. Given your overall "gravitational attraction", you might be OK with the 90/130, as Nessism suggests. However, check with whoever you buy them from, they might allow you one rate change within the first 30 days or so. If you find that you are bottoming out too often, get the heavier springs.

.

[Gorminrider]

yes, It must be even worse than trying to fit a helmet or shoes off the internet...
I mention sag because it gives you some reference to the thickness of spring and coils of spring and length of spring you have now ...you can use what you have now to get a handle on which questions to ask.... I'm going to wing it, if only to illustrate the questions I would have...

simplistically assuming the center of gravity is in the middle of front and rear suspension (and that's important-I just am not bothering beyond simplicity)...and two shocks means each shock spring takes 1/4 of the total weight. ...the forks taking the other two 1/4s...

Soooo, 1/4 weight of (bike + you) divided by wanted sag in inches= (wanted sag equating to comfort+roadsurface-following) where it all goes to opinion! fun eh?

still, on a 12" shock on being collapsible to 7.5"(a guess! I don't have time to go look) =5 inches of travel...1/4 of this is 1.25", one third is about 1.666"...avg is a bit less than 1.5" sag wanted on a 12" shock....
assuming CG is central , 90/130 collapses 1" with a (bike+you) equalling 360#

SO! ...this hopefully means the same shock does a kind of comfy 1.5"sag to support 540 #...you+bike-185(you) leaves a motorcyle that weighs 355# ...until the "progressive" bit is used up. Then the spring gets harder...

This seems like springs suitable to a lighter bike. but it's just an exercise of simple assumptions

(the shock itself is important too. It must control acceleration of these springs on the rebound or it's all out the window as to "travel" when actually riding. ...)

[salty_monk]

I've used both of those & the old 140/95 they used to sell on my 1000 at some point. The lighter ones were best for me. I'm 20lb lighter than you. The 150's were like a rock....

[RustyTank]

I've used both of those & the old 140/95 they used to sell on my 1000 at some point. The lighter ones were best for me. I'm 20lb lighter than you. The 150's were like a rock....

I wish I was 20 lbs lighter than me too

[steve murdoch]

I had the 95/140 combo on a GS1000. Not sure if that rate is available anymore?
I weighed 175#, rode the bike aggressively and that spring rate was fine.

[Gorminrider]

so, I guess from the above recommendations that they are generally selling springs that are "Normal" or "Heavy Duty" (for the "normal" or larger Americans on larger bikes...) and not selected for smaller/larger bikes...

Your old springs may fit the shocks too...(it's been done before) This is one of the advantages of being able to just buy the shocks, as in a car, but you need know the diameters. The Progressives' have models with at least two spring diameters, i recall.

[RustyTank]

so, I guess from the above recommendations that they are generally selling springs that are "Normal" or "Heavy Duty" (for the "normal" or larger Americans on larger bikes...) and not selected for smaller/larger bikes...

Your old springs may fit the shocks too...(it's been done before) This is one of the advantages of being able to just buy the shocks, as in a car, but you need know the diameters. The Progressives' have models with at least two spring diameters, i recall.

It's a good idea Gorminrider, but I'm super interested in a black shock/spring combo. The shocks/springs currently on the bike are silver hagons that at some point got some black, high temp spray paint all over them due to someone spray painting nearby. Not sure how old they are as they came with the bike but I'm sure they're still good. I'll hold on to em and maybe use them on another bike. Just lookin for a different look.

And yea I noticed the "normal" vs. "heavy duty" options. I'm under the impression that the "normal" is what I'd want.

[Gorminrider]

Yes, it's nice to have new stuff properly done but...still -I paint my nasty, ugly springs with primer and "appliance epoxy" OR with a brush, black "rust paints"..in the latter I'll do "rust converter" too-

but absolutely, saddle bags will wear these enamels off...

I THINK I might have found the specs for your Progressive springs...from a pdf I saved from somewhere..I can't get the api to display things properly but if you sort out the bad copy/paste job...


Order No. Rate lbs/in Rate kg/mm Length-In Length-mm I.D.- Inch*** I.D.- mm*** Notes (Fits)

03-1370B/C 90/130 1.61/2.32 8.5 216 1.85 47 11.50”, 12.00”
03-1368B/C 105/150 1.88/2.68 9.37 238 1.85 47 12.50”, 13.00”, 13.50” & 14.25”
from this info, the 90/130s ("Notes-Fits" )seem to suit longer shocks so they probably just have an xtra coil?


and while nobody cares much about my "calculations" (least of all maybe me because I just use the originals until they leak, or no longer function) I didn't include the angle of the shock probably important...though our bikes do have near vertical shocks.

[RustyTank]

I just got off the phone with a rep at Progressive. I should've just given them a call at first. Sorry to have waisted anyone's time on here but I do appreciate the conversation. And, knowing myself, had I called Progressive first I'd still be skeptical and would've jumped on here to make sure. So with what you guys have told me and with what the folks at Progressive told me I feel pretty confident. Anyway, this is what I've learned...

1. The 90/130 springs are in fact going the best option for me
2. The 12 series shocks in black are only sold damper and spring separately, meaning the buyer needs to install the spring onto the damper so I'll need a spring compressor. DCC sells one for $35.
3. He also informed me that, once the shocks are installed on my bike, the shock length from eye to eye should be 11 1/4" in length, which is really great information.