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.