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Suspension Settings

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by PatB, Jan 29, 2010.

  1. Here's one for any resident suspension gurus. I could probably work it out on paper, but I'm feeling idle so I'm hoping someone has the answer at their fingertips.

    As noted in the Chicken Strips thread, my K100 appears to be running out of tread on the front tyre before the rear. This is with max preload on the back and stock, non-adjustable forks on the front.

    If I raise the back of the bike (longer shock) or lower the front (drop yokes down forks, shorter springs) in search of less rake and trail for lighter handling and better turn in, will this make the problem better, worse or make no difference?

    Assume a matching pair of tyres, although the weird rear rim size on the K limits things a bit.


     
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  2. Try going faster and carrying more corner speed.. Don't need to touch suspension then
     
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  3. Think you have answered yourself here. More weight ova the front, more wear. If you dial in preload in the rear it raises the rear. On usd forks the more you dial in the lower they go.
    Do your static/rider sag.
     
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  4. What profiles are the tyres? It's rare for the front and rear of a bike to have equal gaps at the side, just due to the different profiles of the tyres. It's normally the front with the high profile, but it's a K100, so anything could be at play.

    Do you have adjustable ride height adjusters? If all you are doing it changing the preload, that changes where the shock sits in the stroke (for when you are on it). It should be adjusted to provide the correct sag, not change how the front or rear tyres wear on the side. A correctly set sag for your weight will allow the suspension to work within it's range and accommodate both extensions and compressions. For a road bike, typically people like the sag, with you on the bike, to be at around 30% of the total stroke. This gives the suspension somewhere to extend to AND allow compression on brakes and bumps.

    Chicken strips mean next to nothing, unless they're massively wide and the bike is a uber modern sports bike and even then it just means that it's spending a lot of its time in a city environment.
     
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  5. It's not that I'm worried about the strips as such. It's more that I'd prefer to go off the edge of the tread at the back first as gut feeling tells me that this is preferable at the limit. I realise that it's probably more to do with tyre profile than suspension settings, but am curious as to whether having the bike sitting more nose down will affect the width of the front strip relative to the rear and if so, in which direction.

    The K has the same height profile front tyre as rear (F 100/90-18, R 130/90-17), although the strip width discrepancy was noted with different brands front and rear, with the front newish and the rear at 50%.

    There's bugger all built in adjustment at either end, just preload on the rear Koni. My first move to get the thing to turn is going to be to drop the yokes down the forks a bit (probably 10 mm at a time). I'm going to do this anyway, but was interested to get a bit of feedback as whether it would have the incidental effect of giving me a set of chicken strips I'm slightly more comfortable with.
     
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  6. 10mm is an awful lot for a starting change. I could feel the change on the SV650 (race bike, race rear shock, modified front end) with 2mm. And I made an initial change of 5mm, backed off to 3mm. The difference was marked.

    I'd set the sag first, give me a theoretical best practice baseline. From there then drop the front a little, see if it enhances the turn in. I'd leave the preload at the sag settings until I was sure I wanted to raise the rear (though at the expense of travel).
     
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  7. Fair enough. I was basing it on the recommendation of a mate who races LCs so he's a mad bugger anyway. He used to crash quite a lot too.........

    That and the fact that the K has very lazy geometry as standard, being designed to cross continents in hours rather than be wrestled round the rather tight confines of Wanneroo and Collie. What I perhaps should have pointed out is that I'll be playing around with the empty, springless forks to ensure that I don't go so far that the trail can go negative under heavy braking. I don't think it's possible, given the conservative starting point, but I've sufficient self preservational instincts to check first.
     
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  8. Might be worthwhile pm'ing Macmanmike. He's got an old K he redid the suspension on and was very, very happy with it.
     
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