Let's talk spring rate -FJR rear spring

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RenoJohn

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I'm hoping we can use this thread to discuss spring rates on the FJR.

Like many, I have been bit by an undersprung spring (Wilbur) and that has made me more cautious about just taking advice from a single source.

Yes, I realize spring rate is subjective and we all have different riding styles, I also realize that it is very complex and you can call many suspension guru's ..give them your stat's and get various opinions in reply.

So, perhaps on this thread we can just compare notes?

I'm about to throw on an Ohlins with a 170N/mm spring rate(not sure stiff enough?)

ME:

**220#w/gear typically ride with modest touring paraphenalia and usually with aux fuel.

**I ride like a little girl, or at least that is what what i've been told.

**I'm using RaceTech 1.2KG/MM in the front forks.

A very reputable source has told me this 170N/mm spring should be good for me .....but before I pull the trigger I want to do a little checking around.

I'm no rocket scientist on this stuff, so if you are, please make your replies so that us DUM (dumb) folks can understand.

So, anyone around my weight want to comment on your rear spring rate???

Anyone know how much the 170N/mm is above OEM??

 
Why not have the Wilber's resprung? Just sayin'............

I can't fault my shock and plan to have a better spring (correct for my heft) installed when the rebuild happens.

 
Why not have the Wilber's resprung? Just sayin'............
I can't fault my shock and plan to have a better spring (correct for my heft) installed when the rebuild happens.
Mike, Wilbur was on a different bike and Yep, have since replaced the spring ...with one that I had used before I went to Wilbur. I don't blame the wilbur shock per say, but I certainly blame me for not doing my homework and blindly going off of their recomendation. Last time I'll get one recomendation on spring rate ..and the last time I'll let a manuf ship me a spring before knowing the spring rate that they plan to put on my shock.

Hope to avoid that PIA by getting it right the first time with the FJR and Ohlin.

.... hoping to get some feedback from other fjr folk here to compare with both my math and the recomendation of the Ohlins' dealer.

 
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OK, so this might be the most circuitous datapoint so far, but maybe it will help.

I just pulled out my original Wilbers spring and it has "59/59-110-165" stamped on it. Does the latter number represent n/m? If so I also remember when GP Suspension pulled it they said it measured 619 pounds. They replaced with a 800 pound spring and it has served me very well at 265# with riding gear, full rally gear, a cell, and a Pelican case, but it's also 30% more than I had originally had on the Wilbers.

...not sure it helps or not, but in terms of pounds differential from 265 to 220 I would guess you'd be wanting a 650 or so. I don't know if it's interchangable or not, but I've got my Wilbers 619/650 sitting here to borrow if you want.

 
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I've got a penske on mine. 230lbs in the Bday suit so you can add weight from there.

I had an 800# spring from GP Suspensions and found it too soft. An 850# is just right.



**I ride like a little girl, or at least that is what what i've been told.

I don't (unless its raining :rolleyes: )

Given that you have a fuel cell, and an ohlins vs penske, we are similar with weight.

I would say an 800# would prob be fine for your style, no more than 850# though

 
I've got a penske on mine. 230lbs in the Bday suit so you can add weight from there.
I had an 800# spring from GP Suspensions and found it too soft. An 850# is just right.



**I ride like a little girl, or at least that is what what i've been told.

I don't (unless its raining :rolleyes: )

Given that you have a fuel cell, and an ohlins vs penske, we are similar with weight.

I would say an 800# would prob be fine for your style, no more than 850# though
hmm, so if I do the conversion; my 170N/mm converts to a 756lb spring??
*if* this is correct it confirms my guess that it might be a tad weaker than I'm looking for ...but pretty close.

I was not able to make any sense out of Iggy's numbers ...other than the 800 lb ...but it seems that I'm at least in the ballpark. Thanks iggy for the offer on the spring ...but I think I'm getting pretty close on this.

 
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N/mm * 5.710143 = lb/in

so 170N/mm = 970lbs WAYYYY to much

800 LB = 140.10 N/mm

850 LB = 148.85N/mm

I am Taking Igs # of 110 and comming up with a rate of 628lbs He said it measured 619 when It came off so it lost or never had 9 theoretical Lbs.

Don't worry, some Engineer will be along shortly to tell me my math formula is wrong Or maybe just harass Ig for compressing 9lbs out of a piece of coiled steel :p

 
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N/mm * 5.710143 = lb/in
so 170N/mm = 970lbs WAYYYY to much

800 LB = 140.10 N/mm

850 LB = 148.85N/mm

I am Taking Igs # of 110 and comming up with a rate of 628lbs He said it measured 619 when It came off so it lost or never had 9 theoretical Lbs.

Don't worry, some Engineer will be along shortly to tell me my math formula is wrong Or maybe just harass Ig for compressing 9lbs out of a piece of coiled steel :p
Thanks much. curious why the Ohlins folks would be wanting such a stiff spring? I was worried it was too soft, now i'm worried the other way. I need to investigate some more -thanks again for all of the help.
 
I am Taking Igs # of 110 and comming up with a rate of 628lbs He said it measured 619 when It came off so it lost or never had 9 theoretical Lbs.
Sounds plausible. Being a spring rated in N/m then they wouldn't be bound to 50 pound increments like Eibachs anyway.

N/mm * 5.710143 = lb/in
so 170N/mm = 970lbs WAYYYY to much
Hmmm....I'm trying to find the same figure and find one and two sites that convert and suggest 1 newton meter = 8.850745792 inch-pound....so 170 newton meters = 1504.626784572 inch-pounds....which doesn't make match and would be worse? :blink:

I think I'm confused of how to convert these units. They are energy conversions aren't they? Or maybe I can't find a converter for lb/in instead of in/lb?

 
I am Taking Igs # of 110 and comming up with a rate of 628lbs He said it measured 619 when It came off so it lost or never had 9 theoretical Lbs.
Sounds plausible. Being a spring rated in N/m then they wouldn't be bound to 50 pound increments like Eibachs anyway.

N/mm * 5.710143 = lb/in
so 170N/mm = 970lbs WAYYYY to much
Hmmm....I'm trying to find the same figure and find one and two sites that convert and suggest 1 newton meter = 8.850745792 inch-pound....so 170 newton meters = 1504.626784572 inch-pounds....which doesn't make match and would be worse? :blink:

I think I'm confused of how to convert these units. They are energy conversions aren't they? Or maybe I can't find a converter for lb/in instead of in/lb?
1 N/mm = 5.724 lb/in (springrate)

1 N-m(torque) = 8.85 lb-in (torque)

Maybe post this in the Bin -o Facts for future Ref.

1 newton meter = 8.850745792
Its not a Newton Meter (force) its a Newton / Millimeter (force per distance).

I'll stop now while I still sound smart :D

 
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Yeah, newtons/mm to lbs/in is two conversions. Convert Newtons to pounds, then convert millimeters to inches.

1 newton = .225 (more or less) pounds, so 170 N/mm is 38.25 pounds per millimeter. An inch has 25.4 millimeters, so multilply 38.25 by 25.4, and get 971.55 pounds per inch for the spring. Damn stiff spring!

To make a single conversion factor, multiply the .225 by the 25.4 and get the 5.715. Technically, that's 5.715 pound-millimeters per Newton-inch, which makes the units work out.

Isn't science fun? :glare:

By the way, my 5.715 is different from Fencer's 5.710143 because I rounded off the Newtons to pounds factor to .225. My math is easier. :p

 
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Someone has this above but just to be sure N/mm measures the stiffness of the spring That is how many Newtons (unit of force) it takes to compress or stretch the spring by 1mm. The spring will have one number describing the stiffness if the coils are equally spaced.

If the spring coils are not equally spaced then the spring stiffness varies as the coils are compressed. I don't how these are described but there must be some standard way of doing it.

You should ALWAYS specify the units you are using. Half the problem seems to be the mix of units people use. You have to make sure you are comparing like with like.

N.m is the unit of moment or torque which is very different to stiffness.

Lecture mode off.

 
If the spring coils are not equally spaced then the spring stiffness varies as the coils are compressed. I don't how these are described but there must be some standard way of doing it.
Reno,

He brings up a good point. Maybe the 970lb shock is a progressive rate shock. It may start real soft and the viagra kicks in to make it more firm under compression reaching a total of 970. Thats just a guess though.

When you check on the spring, ask them if it is a staight rate or progressive spring.

 
By the way, my 5.715 is different from Fencer's 5.710143 .....
I told you someone would be along to tell me my math was wrong :p

Now, who is gonna step up and give Iggy hell for compressing a steel coil? :assassin: :D

Also for The Bin O Facts

Copied from a post from Lee At Traxion on Gen 1 and 2 OEM Springs.

Lee Knows his stuff

There are two shock springs on the Gen1 and Gen2 FJR. I can only speak for the '05 (Gen1) and '06 (Gen2) models since those are the year/models I have tested at the shop.
The '05 had a short 1400 lb spring AND a longer 670 lb spring. On the soft setting, the two springs are used in series and provide a 440 lb/inch rating. On the hard setting, the short spring is locked out and the single 670 lb spring is used.

The '06 uses the same rate longer spring, but the short spring had a rate of 1800 lbs/inch. We didn't test them in series because it didn't seem necessary at the time.

What we learned from testing and measuring the '06 shock was the soft setting was upped to make it more useful to a wider range of riders while the hard setting was left unchanged. Physical dimensions were exactly the same on the '06 model shock when compared to the Gen1.
 
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What's the easy way to determine what spring rate the penske coil is?
Look at it :p

I just swapped springs on my Gixxer

The Penske Spring is written on the side generally a 7-# (it may be Eibach, I'm not sure if Penske actually does the spring)

meaning 7 inch spring with the rate following

On the Hypercoil spring I took off it was engraved on the end (flat spot on the coil) you have to unload the spring and possibly release the collar on the bottom (easy E-clip) to get enough room to look

I can Take Pics if you need

 
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He brings up a good point. Maybe the 970lb shock is a progressive rate shock.
I have never heard of progressive spring on rear shocks?????

....but I learn something everyday so maybe this is today's lesson.

The Ohlins folks are saying that the spring is likely OK for me ..but I have (had) reason to believe it may be a bit soft (same spring was recomended to a lighter rider).

After the dialogue on this thread, I'm wondering if it isn't too stiff??

Yes, easy enough to put on the bike and try it, measure static and dynamic sag etc .... but the bike is down getting some TLC ...This shock is new to me and I wanted to swap springs now (if necessary) as the timing to do so is good right now to have ready when put the bike back together.

Here is a pic of the shock, no indication that is is progressive, but I don't know how one would easily identify that on a short rear shock. Also, I'm assuming the 170 refers to the 170M/mm that the Ohlins folks have told me that this spring is.

OhlinFJRshock_01.JPG


Thanks again to all the good points and help here.

...renojohn

 
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