REAR spring rate: WHAT IS RIGHT!?!? - Stromtrooper Forum : Suzuki V-Strom Motorcycle Forums
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post #1 of 21 Old 09-06-2013, 01:49 PM Thread Starter
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REAR spring rate: WHAT IS RIGHT!?!?

I've researched threads on this issue 'til I'm crosseyed and my head is spinning...and I feel I have no choice but to contribute yet another thread to the topic. (Sorry!)

• I have a 2007 DL650A.
• The bike has 39K miles on the original shock.
• I weigh 225lbs.
• I mostly ride solo, but often ride 2-up with my wife, who weighs 140lbs.
• When riding 2-up, we're usually loaded with 3 hardcases' worth of gear.
• So on 2-up trips, we're looking at a total load of 365lbs + gear (so around 390-400lbs total load).

Based on the above, I decided (after reading a pile of threads on this) that I could benefit from a rear spring swap (replace the OEM spring with a stiffer one).

YES—I saw a dozen threads in which suspension experts said "a spring upgrade alone won't help because the damping will be off."

I ALSO saw a dozen threads where people who had only upgraded their rear spring said it was definitely an improvement.

Because I don't think anyone would lie about a stiffer rear spring (but not a whole new shock) being an improvement...I decided to go this route to save money.

NOW TO MY QUESTION: When ordering a new rear spring, I used RaceTech's spring rate calculator...which said at my weight (225lbs) I needed a spring with a rate of 13.312kg/mm. (The site says the stock rate is 8.2kg/mm.)

Great, I was all set! Except...

THEN I started reading threads with people saying RaceTech's calculator is messed-up...and that spring rates of 13-14kg/mm are way too high/stiff.

So now I have this new spring sitting on the kitchen counter...and I really have no clue whether I should install it or not???

Perhaps my biggest question is this:

If a spring rate of 13.4kg/mm is WAY too stiff...WHAT IS THE WORSE THAT CAN HAPPEN?

Will I be hurled off the bike and die?
Will I crash when the rear tire leaves the ground on the tiniest little bumps?
Will this spring destroy whatever is left of my stock shock?

Or is the worst that can happen that I'll just have a slightly harsher ride...but otherwise everything will be fine?

(And will the ride be too harsh when there are close to 400lbs of riders and gear on the bike?)

I'd be GRATEFUL if anyone can help me cut through all this conflicting information!

Thanks,
Scott
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post #2 of 21 Old 09-06-2013, 05:08 PM
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Did you look at the spring rate chart at penskeshocks.c ? You'll have to choose whether to get one for fully loaded or not, as one spring rate can't do both. But you probably know this already.
Find out how to set sag/sack so you know if the spring rate is correct. You'll want about 40% of the total travel when loaded up.
Running too stiff of a spring would mean there wouldn't be much travel available because the shock would be riding near full extension, not leaving enough to absorb the bumps. I don't think I'd choose the spring rate for a full load.
Sorry I couldn't be more helpful.

2007 DL 650 with assorted upgrades
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post #3 of 21 Old 09-06-2013, 05:51 PM Thread Starter
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That's somewhat helpful, thanks. I'm just surprised that this isn't more of a science. It seems more like reading tea leaves. :mrgreen:

I'm guessing my only choice will be to install the shock...and see how it feels? (And of course there's the other huge wild card...which is that if I don't know what GOOD suspension feels like, I'm likely to be blissfully ignorant---which is probably a good thing.)

Scott
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post #4 of 21 Old 09-06-2013, 08:32 PM
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RT Spring

I went through that whole song and dance too. I finally contacted RT and talked to a technician. The spring recommended was the same their online calculator predicted. After installation on my Vee the sag dialed in just as expected. That told me the RT calculator is correct.

My riding buddy is about your weight, rides a Wee and installed a 13.4 kg/mm rear and 1.0 kg/mm fronts. His sag dialed right in too. He is happy as a clam.

What I think you want is the spring rate that will give you correct sag with no preload when you are solo. You will then crank up preload when hauling mama and luggage. I was doing just the opposite. I wanted the spring rate that would allow me to crank preload to max and reduce it as I lost weight. Louie at RT hit it right on the money. I have 40mm of sag at max preload.

Call RT and ask for a recommendation. They aren't too good at keeping up with e-mail, so it's best to call.
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post #5 of 21 Old 09-06-2013, 09:43 PM
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13kg/mm would be too firm solo unless you are 2 up with all the suitcases. if i aim for solo weight, i go for 11-11.5kg/mm approx... with remote preload max out, u will be a little soft 2 up with all the gear, but just acceptable.


this is base on own experience my weight of 210lbs and 108nm spring.

good luck

L2 Glee;

K8 Wee ABS(SOLD);

SOLD: 06 FZ1; 04 Fireblade; 02 Fireblade; 97 CBR 600
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post #6 of 21 Old 09-08-2013, 12:20 PM
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Curious if anyone knows if the info on the RT site can be used for a 2012 Vee? I tryied looking up the recommended rates for my Vee, but noticed that the years listed only goes to 2009.

All this info is very helpful

Cheers

Nem
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post #7 of 21 Old 09-09-2013, 12:16 AM
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Quote:
Originally Posted by Nemisus View Post
Curious if anyone knows if the info on the RT site can be used for a 2012 Vee? I tryied looking up the recommended rates for my Vee, but noticed that the years listed only goes to 2009.

All this info is very helpful

Cheers

Nem

I'm wondering the same thing. Any info would be greatly appreciated.
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post #8 of 21 Old 09-09-2013, 11:38 AM Thread Starter
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Like so many things motorcycle-related...I have a feeling you'll get a wide variety of opinions.

Just in this thread, someone says 13kg/mm is too stiff for a spring (not calling you out AceRider...just pointing out that different opinions exist)...but I've seen posts from at least a few people who weighed well over 200lbs who all say the 13kg/mm spring was a "major" improvement in their rides.

On the flip side...in spite of everyone who says "changing the spring alone is pointless," I haven't heard one report (yet) of anyone who did this and said the results were NOT better. (In every case it resulted in an improvement.)

That's enough to convince me it's worthwhile, especially for the $100 I spent on the spring.

Some people say "If you spend $100 on the spring, you might as well just spend $400 on a new shock." Sure—if you HAVE the extra $300! (And I don't.)

Once I get my new spring on, I'll definitely post a review here. I'll be riding solo every day (commuting)...and I have a long 2-up trip in a couple weeks with my wife...so I'll get to check it out both ways.

Scott
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post #9 of 21 Old 09-09-2013, 12:36 PM
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A case of ymmv so sure... It's important to state the exact weight and type of bike. V 1000cc and someone "well" over 200lbs might like 13kg spring.

L2 Glee;

K8 Wee ABS(SOLD);

SOLD: 06 FZ1; 04 Fireblade; 02 Fireblade; 97 CBR 600
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post #10 of 21 Old 09-09-2013, 02:24 PM Thread Starter
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Well...and though getting it perfect would be wonderful, if my choice is between a spring that's too soft or too stiff, I'll take the too-stiff spring any day. (I can handle the bumps...and it'll be better riding 2-up.)
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