I am looking to upgrade the forks and the Racetech calculator recommends a .46 spring rate and Moto-Pro recommends a .42 rate. Does the two measure spring rates different? I spoke with Moto-Pro and they confirm the .42 rate, have been unable to speak with anyone from Racetech.

I am 190lb suited up and the bike is a stock 06.

Ken

 

Spring rate is defined and measured in only one way.

"I spoke with Moto-Pro and they confirm the .42 rate, have been unable to speak with anyone from Racetech."
That right there tells you where you should buy the springs from.

--
Mikko

 

Some of these recommendations also depend on valving mods made to the fork. Moto Pro's are probably based on a stock valving setup. John at MP will confirm that the stock valving has a horrible compression spike based on a compression piston that won't flow enough oil no matter what else you do. Race Tech's setup sounds like it's based on a revalve, as the heavier springs would suit better oil flow a bit better. That said, I run the .44 Race Tech springs, and I'm your weight...probably more with all my gear. If you're getting a lot of air or doing high speed, desert type stuff, the .46 with a revalve would probably work fine. I did a full Race Tech Gold Valve revalve on my '06 and run .44 springs with excellent results. Without a revalve, I can't see you needing anything over .44.

The rear shock valving is also very marginal but better than the front. I highly recommend revalving the front, as it will always yield a very harsh spike.

 

Thanks for explaining the possible differences in the two, as it may relate to revalving. I'm about to do something to mine, and it makes sense to revalve...as too often, people simply through a stiffer spring at a too-slow-to respond unit, just to find out that all they've done is loose some traction while avoiding bottoming out as often. That's not good enough...good suspension work INCREASES traction because the tire stays on the ground more, while preventing bottoming out...and that requires fast-enough-flowing valve setups. Same with oil viscosity...oftentimes people only stiffen it up, by using thicker oil...and again lose traction for the "benefit" of not bottoming out as often.

Riding a correctly set up bike is like night and day compared to riding one that is simply stiffer. I like to do timed laps on a course to see what actually performs better. Sometimes, too stiff FEELS faster, because of the more jittery feedback through the handlebars and pegs...but, the stopwatch doesn't lie.

 

Thanks for all the info.

I was planning on going with Motot-Pro but was looking for a reason for the difference. Also I will be doing the valve with the springs, just getting my wish-list in order and prioritizing it.

Ken

 

If I were having someone do the work of revalving, I think John at Moto Pro is a good choice. If I were going with off-the-shelf components and doing it yourself, I'd go with Race Tech. I've spoken with John, and I think he knows what he's doing. He's already worked on some '06/'07 and '09 models, so he's familiar with the subtle differences in them. I think his work is as good as Race Tech's if you're paying someone to do it. That said, when I was doing the shock and fork revalve myself with RT components, twice I had to call them with a technical question that wasn't clear in the text. I got a real person both times and got good recommendations and info. It seems like when you have their Gold Valve and other kits in hand, the service number they give you accesses a good tech quickly.

It's also interesting that Cogent Dynamics in North Carolina who do tons of high end suspension work are looking into products for the KLX250/300. A fellow named Rick that I've known through another site recently bought a KLX250 and is pretty pleased with the bike. He's already modded the suspension on his. He's sending me a tweaked KLX shock with his mods to test, and I'm sending him mine to do a dyno test for comparison. Should be interesting. Cogent may be known to some for their Moab shock that goes on DR and KLR 650's and maybe some other bikes.

 

Hi TNC. Any chance you can post up the part numbers for the .44 Race Tech springs, rear spring (did you go for a 6.2, ) and the Race Tech Gold Valves.

I have some part numbers, can you confirm them, and are the Race Tech springs a direct fit to an 06/07 KLX?>>> (Race Tech springs) FRSP 3946(44) (.44kg/mm)
(Race Tech Gold Valve Kit) FMGV2040.

Mucho apprecio!

 

WOK, I'll have to look out in the shop tomorrow and see if I still have any documentation with the exact part numbers. I simply selected the stuff for the '06 KLX300 with the info of my weight, riding style, etc. that is asked by Race Tech when you order a fork or shock Gold Valve kit along with the online data for shim stack design you get by submitting your kit code number.

There was a difference in the fork spring length on my .44's for the 300...15mm shorter...but here's the odd part. The RT recommendation is from 0-10mm preload by preference. Oddly there's a tiny bit preload with these springs, so it's a moot point. I have to admit that I didn't putz with the OEM springs any, but there must be a hell of lot of preload on them.

I'm using a 6.0 Eibach rear spring for the '06 KLX300, and it's about 15mm longer. However, there's no interference or contact with anything on the bike, and I've run this spring long enough to find any if there was. RT recommended the OEM 5.8 spring for me, but the 6.0 has been ideal.

OK...I found the part number data. The fork kit is FMGV 2040. The shock kit is SMGV 4401. I can't find the RT fork spring number...just the Tucker/Rocky supplier's number. I saw the number painted on the springs just last week while I was changing a leaky MSR fork seal, but didn't realize there would be a test...LOL! They are whatever an '06 KLX300 uses in the .44 rate. RT recommended .46 for me, but I like the .44's.

 

Hey TNC, just for a reference (I might need to get a new rear spring myself...) how much do you weigh? You can PM me if you prefer, LMAO!!

--
Mikko

 

I'm 186 nekkid. Now spend the rest of your day with that pic in your mind. But seriously, when I'm on real epic ride like in Colorado, Utah, etc., I've got a fairly heavy backpack, a decent tool/parts pack on the luggage rack, and a fender tool pack. I've never weighed those items, but there's some extra weight for sure, so fully kitted out I'm way over 186.

On my rear spring being a 6.0 instead of the 5.8, I'm sure this is due to the fact that the calculator was for a KLX300. Our 250S is a bit heavier. I'm not as sure why the front fork works ideally in regards to sag, full travel, and bottom out characteristics with a one step lighter spring than the calculator recommended. However, the .44 springs are significantly heavier than the wimpy OEM versions, so maybe not a big mystery.