I don't know, but I guess once you get the stock spring out of the fork, the spacer should be as long as the difference between the stock spring (longer) and the RaceTech (shorter) spring. That way, you would keep the stock preload. If you want extra pre load, then make the spacer a bit longer, unless you have preload adjusters like SSR or similar.
Oh yeah for sure, I am looking for the outside diameter of the spacer. Ive read every thread I can find on this forum (and the 250 forum) about diy preload spacers and I cannot find the OD of the pvc pipe they used.
Worst case, when I take my forks apart I can measure the stock spacer and run to the hardware store to find something close.
I haven't done it yet, so I can't tell about accuracy.
What parameters did you enter in the estimator to get .8?
I weight 155 lbs without gear.
If I choose a Mid Group B level and mid stiffness, then I get a recommendation of .76kg/mm
If I push it a bit and choose Road Racing level and 'Prefer stiffer' option, then I get a .8kg/mm
Then I checked the Sonic Springs website EX/Ninja250, Sonic Springs (springs for EX250/EX300) Sonic Springs (rate calculator)
That website recommends
0.75 for under 140lbs
0.80 for 140-175 lbs,
0.85 for 175-215 lbs
So based on this, I think I'll get 0.8 springs, and 10wt oil.
I guess if you end up with too soft springs, you can compensate with heavier oil.
Someone recommended me Sonic Springs. He said they are cheaper, still good quality, and good customer service in case you need help. He told me they even make their own emulators, even though I didn't find the emulators in the website.
I will change the oil and the springs for the moment, and decide later if I go with emulators.
Nice, that sounds like a good deal! I ordered mine from Powersport Superstore on ebay and got .80 kg Racetech’s for $104 but I dont think they include spacers even though some ebay sellers photos show a long length of spacer tubing with the springs.
I’ll probably be lazy and just put the springs in for the summer and wait to take the forks off and change the oil this winter.
Let me know how you end up liking the sonic springs.
The spacers that came with the springs are nothing special, but I guess they do the job. The only thing I noticed is that the walls of the tube are quite thick. At least 2mm thick wall.
They don't fit too snug in the tube. They left about 1mm gap on each side.
The stock spacers are made of metal and fit more precisely, but they have some free play too.
Stock metal spacer on the left, and plastic tube on the right:
I don't have a front stand that raise the bike from the triple, so I used a ladder and a couple of ratchet tie downs to raise the front end of the bike.
I also used my regular front stand, which raise the bike from the bottom of the forks, to make it easier to go from "hanging" to 'sitting'. I started by raising the bike with the stand, then hook the tie downs to the upper triple and put just a bit of tension on them. Then, you remove the stand and the front end is in the air. You put the stand back on and the bike is sitting on the forks again.
At the time of re installing the forks caps, I found quite hard to push the springs down and install the retaining snap rings again by myself. So I used another tie down to compress the spring:
I put about 300 mls with the new springs, half street half track.
It feels very nice. Much more solid and got a better feeling on the front brake. I tried several hard brakes on the street and I was able to modulate more the braking to the point of making the front tire screech (my bike is non ABS and I have a CBR600 Nissin front caliper)
At the track it feels more precise entering the turn. With the softer springs and lighter oil it would move more. It gives me more confidence.
The .8 kg/mm sprigs give me 10mm of static sag and 10mm more when I get on the bike. After the hard braking I tried, the zip ties on the forks showed me 90mm of total travel, so it's leaving me 30mm of unused fork travel. There's no way I'll bottom out these springs. Maybe .75 km/mm would have been better. I weight 155lbs without gear.
Also, I may have left too much preload, as I'm only getting 20mm (actually a bit less) when I sit on the bike. I may pull the spacers out and cut them out a bit more.