Rear Spring Upgrade
 

I'm having trouble with the rear suspension bottoming on moderate terrain. I've set the sag and increased compression settings. Looking for feedback on what rear spring to use. Been searching the forums but have found little info.
2009 KLX. I read that the bike is setup for a 150lb rider. I'm 185lbs. When I plug in my info into the Racetech calculator it comes back as the stock spring of 5.6kg/mm and recommends a 6.9 kg/mm.
Looking through other threads the highest spring rate I see mentioned is a 6.2 kg/mm.
Doing the simple math. The increase from 150 lb to 185 lb rider is 23%. The proposed Racetech increase (5.6 to 6.9) is 23%. So seems their recommendation seems right.
Appreciate any feedback and real world experience.

I just ordered a rear spring for mine and that was the same rate they gave me. Im bottoming out way to much and i don't like to increase preload. The front that they recommended was night and day difference so im guessing the back will be too.

Thanks for the response. Guess I'll give it a try.
As I always look for the best deal. It appears that the spring is a 2.5 diameter x 10" length spring. The 6.9kg/mm converts to a 386 lb/in spring. I can get a 375 lb (or 400 lb) spring from Summit Racing for $38. Link.

I ended up using a 7.5 from Procycle.
It was listed for a DR650. Fit fine.
I got the 6.4 from Race Tech and it was too soft for me,
220 Lbs.

im 180, so ill give the 6.4 a shot and see how that works out

I didn't think there was much difference in the spring requirements/dynamics between the '06/'07 and later models. I used a 6.0 Eibach spring on my '06, and it was perfect for my 190 pound weight with the addition of a heavy backpack and tailrack bag I use on my big rides...along with a 3.7 gal. Acerbis tank. I also tried a 6.2 or 6.3 Racetech spring, but it was too harsh. I'm a decent rider who pushes my KLX off road, and to me these 6.4, 6.9 area springs sound like 3/4 ton pickup springs. Maybe I'm missing something here on the ratings being listed, but I think a 180 pound guy isn't going to be happy with a 6.4 spring. I can't see you needing more than a 6.0.

Now...it's been awhile since I modded mine...also with Race Tech Goldvalves front and rear...so maybe I forgot or missed that '09 and later models require dramatically different spring rates. What say y'all? Anyone remember?

i have the preload increase beyond where it should be and the compression almost maxed out and i am bottoming out way to easy

Maybe you've lost the hydraulic fluid in your shock. Do you notice a difference when you change the compression damping adjustment?

Ride on
Brewster

I was wondering about that too. If his '09 KLX shock has never been serviced, who knows what's in there. Brewster, can you recall the normal spring rate upgrades that most of us used for real humans in the 180-210 range?...well...at least American humans.:D I was also curious as to whether the '09 and later models used dramatically different spring rates...I didn't think so from memory. The 6.0 Eibach for a KLX300 worked miracles for my '06.

It was "suppose" to be services last November, after i increased the preload it helped in the bottoming but decreased the ride quality

I don't know who the moderator is, but this thread should become a sticky so it would be easy to reference.

As for buying the spring from Summit or the like, makes total sense. A 10"x2.5 ID spring is a 10"x2.5 ID spring.

I did a bunch of looking when I got a spring for the DRz400 shock to be put on the 650, got a used spring from a sprint car driver who got a spring sponsorship and sold off his old stuff, $20. Seemed Eibach and the others use a common spring set up to suit most all quality shocks and the one length and ID was 10"x2.5", the closest to the DRz which used a 10.25"

I'd get the one from Summit, I doubt they are selling bad product to all those car guys.

I can only comment on the KLX300, which has a 280mm rear wheel travel. Stock shock spring was 5.8, good for 180 lb rider. I had to drop to 5.4 for my scrawny bod (155 lb), riding style, and terrain.
Another known problem with the KLX300 shock is that the rebound damping was too slow. The shock couldn't rebound quick enough over whoops and would pack up. Backing the rebound adjuster all the way out helped some. Don't know if Kawi changed any of the shims in the shock in the later model KLX 250 bikes.

Ride on
Brewster

That only means that it will fit on the shock. The diameter of the wire and the number of coils also affect the spring rate.
Compression Spring Constant Equation and Calculator | Engineers Edge

Ride on
Brewster

It seems the manufacturer tells you the spring rate, so the spring constant formula to calculate that is not necessary. Just buy the spring rate needed.

It is necessary to verify there is enough spring travel to exceed that of the shock to avoid coil bind, including preloading... I did that. Sprint car shock travel is longer than that of the KLX so I wasn't too worried, but did it anyway. The only negative for the DRz shock may be that it may require a spacer if there is not sufficient preload threading.

Sooooo.... are we saying that 38$ spring will work just as well as the 125$ "name brand" one of same spring rate?

I'm wondering the same as TNC- I use a 6.0 on my '12 and I'm right at 200#. If I had know about Summit I would have tried them. If the dimensions work and it won't coil bind then I'd think it should be OK.

When you get the spring from summit and give it a good testing, post up the results. That's why i love online forums, you get a lot of different view points towards the same goal.

I dunno, does a $40 cam chain tensioner work as good as a $100 one does? Mine versus a Tokyo Mods unit?

Eibach has a name and is banking on it, much like Cometic. Not too unusual in marketing, especially in high performance products.

In another example, I send two gaskets with the KLX kit. Kawasaki does not make since the OEM uses an O-ring and even if they did, the OEM runs around $2.70 each. I hand cut a bunch of them, but needed something easier and neater, so I contacted Cometic. Cometic said that paper gasket would cost me $6.00 each, whether I bought ten or a thousand. Now I had done laser engraving and knew a laser would cut gasket paper quite easily. I found my sticker guy also did laser engraving. I have them cut for me for $1.20 each getting a couple hundred made from a $4 piece of gasket material from a car parts store.

Will that $38 spring work as good as a $125 spring? You find out by knowing what you are looking for, looking at, and how it functions.

Of course then there is the case where the huge email company sees a market and does their own private brand part... in this case springs.

"CNC-machine coiled and preset for extra durability, Summit® coil-over springs offer great handling and budget-friendly strength! Coiled from high-strength chrome silicon steel alloy wire, Summit® springs are shot-peened to aerospace standards and given a powdercoated finish. Our coil-over springs deliver USA-made quality and performance. They offer responsive handling, a smooth ride, and firmly planted launches, plus the economical pricing of Summit Racing®. Choose the correct length and spring weight for your application and go racing with the high performance craftsmanship and value of Summit® coil-over springs."

I don't think Summit Racing will risk their business selling junk. I think they know they can make the product and sell a huge quantity of it for a good price, putting it in the "wheel house" of the average racer.

Kind of like what I did, make it very affordable. If you find you bought a bit too soft or stiff a $38 spring it isn't so prohibitive in price to just get another versus a $125 spring.

I'm betting Summit Racing is running their springs on their cars.

I also found if you want to pay more you can go with the $54 AFCO spring set, from Jeg's. AFCO is another automotive suspension performance parts company with about 30 years in the industry. So clearly price may not define quality in this case with wound wire springs.

Oh, and Summit sells the 10" Eibachs for around $60! Makes you wonder who's making that Summit Racing spring...

I see pending disaster with this Summit spring. The inner ID will probably be just a bit larger. The carnage will go as follows. Spring pops out around the preload collar under big g-out compression...spring breaks upper shock mount...spring continues launch through the plastic airbox and seat bottom...severe hemorroidectomy delivered to the rider.;)

I haven't checked my 250 to see what the top ID is, so I'd need to do the necessary measurement. Bigger collar for the top may be needed. But I'm thinking one can be made for less than $100.

I did some more digging and would say measurements should be taken. If it is near 63.5 which is the measure for the Summit springs, it's a bolt in. Otherwise maybe a new collar may be needed and could be a bit thicker for strength while compensating for the possibly shorter spring.

Like I said, some research is needed to be certain. I will do so whenever I do something with the suspension on the 250.

Aside from my joke about the Summit spring, the inner diameter issue can be a real one. My Eibach 6.0 spring was listed as a fit for my '06, and it came with either a top or bottom...can't recall exactly at the moment...spacer that slipped into the stock collar. It works great, but without that collar, you have to make something decently precision to insure retention and fit if the stock collars aren't an exact fit.

I think the 250 spring must taper slightly in ID at the top, the aftermarkets are a shade bigger. A machined collar would be in order and probably a breeze for a machine shop that would do specialty work... Heck, ought to do my shock and see what it would cost me to get the collars made if I get ten made. Make it easy to fit up a $40 spring. Maybe I could retire five years earlier... Trying to figure out what I can do in addition to tensioners to get to retire and screw around in the garage.

But Mark...abandon the educational welfare of America's youth, leaving us only with a dark future of ignorance and despair? What are you?...just another greedy capitalist? Maybe Bernie Sanders is right!:D:D:D

I ended up ordering a QA1 high travel spring. More info here. The claim is 28% lighter and 20% more travel. Here is the Summit Racing page with the high travel springs.

Two things...

Politicians and other administrative minions who keep dumping more mushroom fertilizer on the teaching profession to continue to foul the system of educating students. Most couldn't pass an eighth grade proficiency test and don't have a clue what common core actually is, so they screw with the testing and follow uninformed public opinion against actually trying to plot out what students should know at a given time on a nationwide basis. I didn't take anyone's word for what it was, I did the research to learn for myself and find it works in our school district. I guess some just want to have less knowledgeable students. Some of what makes me want to go at 65.

Knees and other joints holding up for another seven years, but some exercise and a walking/stairs regimen has been working to keep the problems at bay for the last couple years now.


No, wait... Three things... I'd like to be done and go do things in the garage... I'm the idiot administrator there!

LOL!...I'm with ya!:D

Wanted to report back on the results of the QA1 high travel spring. The stock spring has the top coil wound a bit smaller at 2"ID. Where the QA1 spring is 2.5" ID. That caused me to use another spring seat adapter on the shock.
Quite happy with the spring rate and cost of the upgrade. Went from the stock 5.6 kg/mm to a 6.2 kg/mm. Which is a 350 lb/in spring.

Awesome thanks!

Where did you get the adapter? And is there any clearance issues because of the wider top coil?

Got the adapter from my garage. I have lots of Triumph Spitfire parts. Turns out the spring seat from a stock spring was perfect with a slot cut in it.
Essentially a large washer with the right ID/OD would work. I think that's what THIS part is.

Need to watch out for the collar or ring rubbing the intake on straight springs, can be a problem unless the spring length and preload combine to keep it keep it away. The stock spring is beehive wound to gain clearance in that area. I doubt very much the stock spring is 5.8, even a new one.

It is not the spring that rubs against the intake, but the spring seat adjusters. They are a larger diameter than the spring. So the larger spring diameter isn't a problem.

I got the stock spring rate (5.6) off the Race Tech website. The 6.2 I installed is stiffer.

Yes it can be the length of the new spring, when the sag is set properly the adjuster and whatever washer or seat you use can be in a place where it can rub. It can seem like it clears but after a few rides you can see it. .49 , 6.4 F R, I'm 190.