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What are preferred sag values for road use? I've just had my forks and rear shock serviced, re-valved and fitted with new springs to suit my 115kgs. The improvement is marked, but I am concerned that I still get 38mm of rider sag with full preload dialled in. The sag on the rear is 51mm, but I haven't yet tackled that.
 

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38/51 is not that great. The front end will run wide in turns with those numbers as you're dragging the rear end. Plus you need more weight on the front wheel for quick turning.

Try setting the rear shock preload at the same 38mm of total bike and rider sag. That way it will be matched. Use 1.5 turns out from full hard on the comp and rebound. Some riders prefer less sag in the rear than in the front as it quickens the steering at the expense of stability. With sport bikes, they like about 25mm but on the Speedy it will feel like a jack hammer. For the street, 38/38 sag numbers should make you really happy and balance well in turns. I run 35/35 and weighed 100kg when I set those numbers. The bike handled awesome and it was transformed. Before I was running about 45/55 from the factory and it was crap. Be sure not to bounce when you measure the sags...just rider weight with your gear on.
It is also personal preference so you may tweak it somewhat depending on your roads and riding style.
The sags make a tremendous difference and it's FREE. :)
 

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Discussion Starter #3
Thanks for the advice Skydogmatt (Matt?)

Thanks for the advice. I'll crank up the rear preload to 38mm tomorrow and see how we go. I'm not happy with being max'd out to achieve 38mm on the front, having just had the suspension professionally rebuilt; I might have to get Promecha to do some more work.
 

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... I'm not happy with being max'd out to achieve 38mm on the front, having just had the suspension professionally rebuilt..
They should have certainly taken your weight into account & matched the springs accordingly. 30 would be a better number.

I hated my OEM Triumph front end - hence the signature link - bike is transformed.
 

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Also keep in mind that if you change the rear preload by 13mm then that will put more of your weight on the front. So, the front preload number may change to a bit more. You might have to re-adjust both. Also, measure the front a few times and take the average to adjust for fork sticksion. Also, if you change compression settings, that will affect the sag too a small amount. To complicate more, the comp/rebound settings affect your turns too. You can google that.

On the Speedy, a range of 30-40 mm for both is really ideal.
It took me a few days of riding and trial and error to find what works well for me. My shop wanted to set everything at 45mm but that was too soft for my taste and the bike reacted slow and bouncy. I tried as tight as 28mm front and 25mm rear and that was a jackhammer in my opinion but the bike handled super. Differential F/R settings change your weight distribution and oversteer/understeer which can get good or bad depending on what you like. All my buddies on superbikes ride them at 35/25. But I have a street bike and not a race rig.
I am still able to lead rides and wait for the majority of them in the mountains plus ride for hours comfortably.
 

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I totally agree. Just recently i set my sag to 35/35 and the bike transformed. It became more comfortable without any bouncing and taking corners with it became magic. For once it didn't seem to matter the quality of the tarmac or my tyres that are finished.
 
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