Yamaha TRX850 Enthusiasts Forum

Hi all, I am currently trying to furnish my TRX with some Ohlins springs and YSS valves as the combo is cheaper than Racetech stuff and much more available here in the UK. The problem is that Ohlins don't supply any instructions, so hopefully someone here can help. Comparing my old setup on the left to Ohlins + valves on the right the new setup is 4-5mm shorter. This isn't normal because it's a 4NX setup with a shorter damper rod, I know normally the 08608 Ohlins are too long for this..





I also know that the valve should go at the bottom, I'm just comparing lengths here. If I use both of the washers that would've been at either end of the spacer then the difference would be more like 2mm and I could always use the preload adjuster to add more, but the question is how much more/less compressed should the Ohlins springs be compared to the original setup? Are they the exact same length as the Euro spec springs and spacer? Ta!

look up how to set sag and this will give you an idea on the preload needed. there is a small curclip holding the rebound adjuster rod in place and easily removed. Remove the rod and place the spring n emulator in place (no need for oil at this stage) and just find out if you have too much spring length(because you sag is under the minimum static sag length 25/30mm) when the cap is in place and preload wound right off.. Once you have an idea on how to set up sag and measurements you can work out if you need to wind the preload on or remove some spring length... or just take the springs back and have them replaced with shorter eibach or similar that you can utilise spacers n washes with..

So "dry" assemble the forks with new bits, then see what the length of stanchion is with no weight on it. Then put all your weight on it and see what the travel is?

I have no idea what you mean about the circlip holding the damper rod in place, do you mean the rebound adjustment malarkey? That's all removed already, just the rod on the cap is left to cut off.

sorry my mistake ..I meant to say the rebound adjuster rod.. I'll edit that now.. google.. setting up sag and that will give you an understanding of the measurements required to get you in the ballpark.. The first measurement being no weight at all on the front end ,the second being just the weight of the bike and third being the weight of yourself on the bike.. all these measurements and the proceess of how to do them correctly is fundermental in getting things right from the start..

Racetech's site doesn't mention taking a measurement of just having the bike's weight on the forks? In fact I can't seem to find anywhere that does use that measurement?

Either way I'll get the damper rods modified this week, and then once they're done and tightened back in place (a faff without the right tool, I don't want to do it too often) I'll see what I get and what I can do preload and air gap wise. If anyone else wants to pitch in all hints, tips and recommendations are very welcome, I have no real idea what I'm doing!

I am the point where the YSS valves and these springs are in, but I cannot tell if the valves are seated properly in the top of the damper rod. The springs + valves + washer are about 4mm shorter in total length than the original setup, should they be this far up the stanchion with the fork fully extended?



Basically, how far up the threads does the original spring+spacer+washers combo manage to get?

In case it's of some help, I've just posted an article in Tech Tips for setting up Static & Loaded sag.
http://www.trx850.com/phpBB_forum/viewt ... =36&t=9564

Thanks Brett, very helpful. I still don't see the point of measuring the static sag though, surely loaded sag is all that's important?

After some rattling, sloshing, poking and general messing I couldn't get the springs to sit any lower so I just put the fork tops back on. A quick test suggests 26mm of loaded sag with the preload adjusters as far out as they will go but it was not bounced up and down, so it may be about right. It was also not in a riding position, just sitting on the bike trying to put as little weight as possible on the floor - there were only two of us and someone had to measure the fork with a ruler! This was also without any gear being worn.

I'll try and put a guide together for these 4NX forks and test them some more, thanks for the help chaps!

You're welcome Snod. It's all important I'd say. My understanding of having the static sag set is that it determines another point or reference, enabling the suspension to be set in terms of its range of movement.

The reason for an unloaded sag by lifting the back of the bike up and taking all the weight off the spring then sitting the bike back down with its own weight helps to determine the spring rate of the shock and if the spring is heavy enough to start with ( around 10mm) for an average on the TRX. Once you then sit on the bike you can set the preload on the spring to get you within the requirements. If too much preload is needed this also indicates a spring rate too soft for your own personal weight. This also is critical as long as the shock valving is set for a TRX as you may find the R6 shock has a slightly shorter stroke and different linkage ratios and swingarm length...The YZF750 shock also has different valving because of different linkage ratios but the swing arm length is the same. I'm sure if you ask those who have had a YZF750 sp shock revalved to suit the Trx the differences straight away. All these factors have an influence on the spring used.