No, it's not feeling like it bottoms on every bump. It feels quite good. It's only if I ride hard enough to catch any kind of air that it bottoms.

Besides, the bike only has 3000 miles on it so unless the shock is leaking, I doubt the charge is bad.

I have quite a bit of preload on it, but not all the way.

Rob

 

Rob,



What are your free and race sag numbers?

 

150 psi is stock for the shock. My RT Gold Valve setup uses about 170-175. And shockingly...pun intended...I don't use nitrogen anymore. I use plain air by application with a mountainbike shock pump. And no, I'm not going to get into a debate over air vs. nitrogen. I've done plenty of that over on Thumper Talk with some folks way more knowledgeable than I am on the issue. There's some consensus that if you race or you honestly hammer your bike in very rough terrain for long periods, you get a benefit from nitrogen. However, even if you ride some very challenging terrain, but then slow down or even stop more occasionally, nitrogen doesn't gain an advantage. This is the way my rides are, so air works just fine. It's a time and heat combination where nitrogen has a benefit. As it stands now, I can periodically check my pressure and even manipulate it a bit if preferred.

Rob, the link here was provided to me by djchan, and it's probably the best and most understandable description about sag that I've seen.

kb1

Just cranking on the preload or not having enough preload causes some real performance issues due to the stored energy or lack thereof on the spring via preload. Follow his instructions about those amounts and measurements of preload issues to the letter, and you'll have about as perfect a setup as you can. That magic "1/2 inch" deal seems to be the real deal. Additionally, you can tell fairly quickly that if you can't get a combination setup of about 95-100mm sag with you on the bike and about 25-30mm of free sag...no weight on the bike by itself...you're probably already out of the ballpark for the given spring you're measuring. Still, pay close attention to that Bruce guy's warning about the amount of spring compression on the shock body. That stored energy concept is true.

 

If you don't mind disclosing your trade secrets, how would you do that?

 

No secret at all. MTB full suspension riders and some of the guys over on T'talk have been doing it for quite awhile. These pumps can be found between $20-$30 and range from 0-100psi and several other options all the way to 300 psi. The very high tech MTB shocks have been using tuneable air chambers for the main spring and adjustable IFP piggybacks for many years now. The main chambers and piggyback chambers on many MTB shocks get about as much cycle abuse as a moto shock and have the same or more tunability as our moto shocks.

Air normally has about 80% nitrogen already. And as far as moisture in the air and the effect on possible corrosion, many/most rear dirt bike shocks have a rubber bladder with an aluminum cap...little chance for corrosion. MTB shocks usually have a real floating piston IFP with much more exposure to components for rust/corrosion. Even after years of use, I've never seen any rust/corrosion in the main chamber body or IFP chamber. This issue has been highly exaggerated.

Still, if I were racing motocross, enduros, or other non-stop events, I'd use nitrogen because you can be hammering in very tough terrain putting a constant cycling stress on the shock for a very long time with no break at all. Heat at those extremes for that consistent, long period could indeed affect damping to a degree. I don't ride like that anymore. I may hammer really hard for a bit, but then I'll cruise for awhile or stop. It doesn't take much of a break from really aggressive cycling of the shock to bleed off excessive heat. Most of my trail riding, even in some terrain with big challenges, is not constant and unrelenting. Even when riding non-stop in some of these conditions, the suspension in not constantly under assault or doing something like 40-minute motos.

 

I believe that one of the concerns about using air in the shock is that the moisture in the air creates a much higher thermal coefficient of expansion over dry air or nitrogen. This would increase the pressure in the reservoir during hard use. Would any of us even notice it?........I doubt it.

Ride on
Brewster

 

Just started to look into getting a new rear spring. My chain roller can't take much more bottoming out. I'm 185 in my shorts. The Moto-Pro site has a nice tool to help set up the front and rear based on your weight and riding style. ( Moto-Pro Suspension ) The tool says that 2007 and older have a 5.8 stock rear spring and the 2009 and newer have a 5.5 stock rear spring.

The stock parts descriptions don't match up with that though.
2007 92145-1161-8V SPRING,SHOCK,K=54N/MM,I.SILVER

54N/MM = 5.5KG/MM according to my calculator.

The 2009 only shows the whole shock assembly. No breakout for the spring.

2009 45014-0246-23F SHOCKABSORBER,SPG WHT+BODY BLK

Not sure who or what to believe, but I can confirm my 2009 spring is indeed white and too light for me.

So if you play with the Moto-Pro tool, weights, riding style, and switch beween the 2007 and 2009 models you'll learn that the springs they list are the same for both model years.

MPS Part #: MPSP622856 = 5.6 spring
MPS Part #: MPSP622858 = 5.8 spring
MPS Part #: MPSP622860 = 6.0 spring
MPS Part #: MPSP622862 = 6.2 spring

The tool says I should go with a 5.8 spring (for up to 204lbs)... which is what you 2007 and older guys are pulling off your stock rides. I'd love to take one off your hands for test and comparison purposes for the good of the 2009 and newer owners to confirm fitment, but only if it's really a 5.8kg/mm spring.

Anyone have any insight?

 

I am the same weight as you and occasionally bottom my 09 rear.

I don't know about moto suspension shops, but mountain bike shops have a simple machine that checks lb rating on springs by compressing them and recording the resistance.

Spring rating can very from manufacture to manufacture.

Has anyone ever had a spring checked.

 

at 190 lbs dry, on my 06 id blow thru the 5.8 like it was 40, i use a 6.4 now. my 250x i went from 4.8 to 5.3 ,

 

I'm still entry level dirt... I think. No plans to redo the forks, just beef up the rear. I don't want it too mismatched, just want to stop the rear from bottoming out. I have 2" lowering links on it which are not helping. I may just put the stock links back on and see how it does. Still, at my weight I know I need a bigger rear spring.