Advice on choosing spring rate

[Crash 142]

I have a 2004 RM250 and am going to start experimenting with different spring rates. I am 160 - 165 pounds, 5'10", and race vet intermediate motocross - no off road or desert, just tracks.

Stock my bike has Showa .44 front and 5.2 rear. I have had the suspension revalved for my riding style, which improved the suspension, but I feel like I'm oversprung now - like the bike will rock in braking bumps and 'bounce' through rolling whoops.

The race tech site suggested a 5.0 rear and .41 or .42 front. I am going to put on a 5.0 rear this week and try it out.

I would love advice on which springs are the best quality - Showa/OEM, race tech, eibach, factory connection... Do some test higher, some lower? Are some more accurate to their rate? Also, anyone expeimented with this bike? Am I going to be oversprung in the front if I only change the rear? It seems I'm using all of my forks travel right now, so I'm wondering if I have the correct springs in front. I might try .43's in the front.

And fyi - if I set my sag at 103-105mm with the stock springs, I have 50-53mm free sag - which tells me I'm oversprung in the back.

Any advice would be appreciated.

I also have a buddy who is the same size and speed as me with an 04 CRF450. Anyone have any springs for him? He's also at around 50mm free sag with his race sag at about 100mm.

Thanks.

 

[marcusgunby]

On my 04 rm125 i went from the std rear to a 4.5(i weigh 165lb)-the rear is oversprung std imo.
I use the mxtech spring rate generator but usually end up softer on the rear to get good sag numbers.Im thinking of trying 0.40 fronts instead of the 0.42s std.

I like showa springs and eibach seem good, alot of aftermarket are crap.Im not sure about RT and FC so cant comment on them.

 

[Crash 142]

I tried the bike with the stock front springs and the ligher rear and the bike felt totally out of balance. I have since put softer springs in the front, .42s, and the bike feels better. Last weekend I experimented with stiffening up the compression both front and back, (using the clickers), and I think this is helping alot. The bike seems much more stable. I mean stable when coming into corners with braking bumps, not high speed sections.

Are there two philosophies - soft springs and heavy valving and heavy springs and lighter valving?: For this bike, in my limited experimentation, it seems the lighter springs with stiffer valving work much better.