What should the rear suspension sag be on a dyna - Shock travel is about 54mm but wouldnt that mean suspension travel is longer (shocks on an angle)
or am i looking too much into this
I've done static sag on a few bikes, there isn't as much travel to play with on twin shock machines so aim for around 20-25mm (rather than the 25-30mm some sites recommend). I'm not a fan of shortened shocks because it's very difficult to get the static sag correct. The guide below explains it better than I could... 1) Static sag is a measure of how much your bike settles on its suspension with you on board. We generally recommend the Race-Tech method of measuring sag, which takes into account any stiction in the suspension components. With a couple of friends helping, fully extend the front suspension and measure from the fork seal to the bottom triple clamp (for conventional forks). This measurement is L1. 2) Put on your regular riding gear and hop on your bike, assuming your normal riding position. Have one friend hold the rear of the bike so that you can keep both feet on the pegs. Your second pal needs to take the same measurement as in step one-once after pushing down on the front end and slowly letting it settle up (L2), and again after gently lifting the front end and letting it settle down (L3). L2 and L3 would be identical in a perfect, frictionless world. 3) Static sag is calculated as: sag= L1-(L3+L2)/2. Averaging the two measurements with you sitting on the bike negates any stiction that may be present. Aim for approximately 30mm of static sag for street riding and 25mm for the track. If you have too much sag, tighten up the front preload. Too little, and you'll have to loosen the adjusters accordingly. One turn on the adjuster will usually change sag by about one millimeter. (NB bikes without pre-load adjusters will need pre-load blocks inserted into the suspension). 4) Moving to the rear of the bike, extend the suspension and measure from the axle to a solid point directly above. Try to avoid measuring to the bodywork, as it tends to move about when you lift the rear end or sit on the seat. Instead, measure to a point on the subframe (or something equally solid). As before, this measurement is L1. 5) Repeat steps two and three, with one person holding the front of the motorcycle while the other takes the two measurements at the rear. As with the front end, 30mm of sag is a good starting point for street riding, 25mm for the track. 6) Calculate the static sag and adjust the rear preload accordingly -one turn of preload usually equates to between two and three millimeters of sag. Here's a tip to check that your rear spring rate is in the ballpark. With your bike unladen, lift the rear end until the suspension tops out, then gently let it settle-how much it drops is the free sag, which should be approximately five millimeters. If the suspension doesn't drop at all, you've dialed in a lot of preload and should consider a stiffer spring. Too much free sag is a sign that a softer spring may be in order.
So if i have 53mm shock stroke about half is sag ??
If you've got a 53mm shock stroke then I'd aim for about 15-20mm of sag (about 1/3rd of travel of the shock). The 25-30mm that most guides say assumes 75-100mm of rear shock travel (which some twin shock bikes don't have). Standard length twin shocks do have about 75mm though. You have to lift the rear of the bike until the shocks won't droop any more to get a starting point. Most bikes (and shocks) will sag just from the weight of the bike a bit. That's what they're talking about measuring in With short travel shocks you need to minimize any sag that happens just from the bike weight so you maximize your suspension down stroke but without making the bike top out on rebound which with short travel shocks is going to need a shock that's got rebound dampening adjustment (many twin shocks only have pre-load). The other way is to get a shock built custom to suit your bike and your weight. But yeah, the shorter the shock travel the more difficult it is to get everything working without bottoming out or topping out. So a 4 inch travel shock is easier to set up than a 3 inch which is easier than a 2 inch. There are twin shocks with variable rebound dampening adjustment (and you don't have to buy Ohlins), the Ikon 7610 is just one example (they've got black shocks as well as chrome). http://www.ikonsuspension.com/product/7610-sp15-series-shock-absorbers/
Yes i brought some Ohlins in the book it states it has 66mm of stroke - So with those answers my sag is setup with 22mm of sag
That sounds like a good starting point but sometimes they actually work a bit better a little either side of what we might expect.
Generally that happens if the spring rate isn't quite right for the weight of the bike and rider (say with a fat bastard rider like me sitting on a twin shock with springs meant for someone lighter).
Shouldn't happen with a set of Ohlins because they can be ordered to match rider weight.
Does shock travel include the bump rubber ??
