Quote:
Originally Posted by Link
Well one question I have is basic preload settings on the rear Ohlin shock. I've seen a number of posts here about starting with 8mm of preload. So I'm asumming that 8mm is the amount of therads showing above the adjuster nut? I come from a road racing background and we always start set-up with sag, static sag & sag with rider on bike so the riders weight plays a huge roll in that. I guess what I should do is measure the static sag & rider sag & then take it from there at least I'll know if the spring is correct. What would be the correct sag numbers static/without rider & rider sag/rider on bike with gear? Right now there is 16mm of thread showing above the adj. nut. I bought my bike used (it's an 06 ec250) from a great guy off this forum who has posted a lot about suspension settings he asked me my weight & said he will set up the bike but I'd like to know if it's correct or not. And in the front there is no preload adj. so is there a sag number for the front? Or how do you know if the correct springs are in there? From what I've read about the Marzocchi shiver is that the fork oil viscosity & amount is how you tune em along with the clickers so I'm a bit confused there also. So if theres a sag measurement for the front at least I'll have a starting point.
Thank-you
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Each Ohlins shock has a spring set up for an "average" weight rider. Typically this is 155-175# (dressed). Riders over 175# will benefit from a heavier spring. Riders under 155# will most likely need a softer spring rate. The preload adjuster rings on the shock will allow you to fine tune the sag to the rider. If you don't know the recommended preload for your shock/spring then 8mm is a good starting point. Start out by putting the bike up onto a stand so the suspension is hanging fully extended. Every shock spring has a "free" (or unloaded) length. Lets use an example of a spring that is 270mm free length for now. When you mount a spring onto a shock & thread the rings down until they just touch the top of the spring, this is zero (0) preload. As you start cranking the preload adjuster ring down into the spring it will start to compress the spring. You are now loading the spring or as it is called in the industry (preload). To get a starting point of "8mm preload" you will thread the rings down until the spring length is 262mm. You will then take the bike off the stand & measure the sag. Most motorcycle mfg's have a call-out for sag for each or their bikes. If there is absolutely no information from your mfg you can use the old rule of thumb: 1/3 of wheel travel should be sag with rider on bike (fully dressed in all gear) bike on ground. Each shock spring has a certain amount of 'travel' before all the coils touch each other. This is called coil binding & in extreme cases the spring will break from too much preload. If you have to crank in more than 15mm of preload the spring rate is not heavy enough & you need a new spring. If your forks do not have external preload adjusters you may still be able to adjust preload by installing washers between the fork spring & cap. Check your motorcycle service manual for information. Bottom line here: If you sit on the bike & it sags down to the tires, try adjusting the preload. If this does not work you need stiffer springs. Conversely, if you sit on the bike & it doesn't move, back off on preload. If this does not work you need softer springs. Easy right? Not really but don't get too caught up in it. It is only a spring. Get out & ride!