Relationship between fork position and shock action

Just had a mate raise his forks up 6mm in the triple clamps to see if it would improve his turning/weight on the front wheel. Generally you expect to see an improvement in turning and some reduction in HS stability. Less tendancy to push, but a higher likeliness to tuck in the corners. I'm not sure if he found this to be the case or not, but commented on the negative effects it had on his shock setup and that the rear was bucking and kicking where it previously wasn't.

 

I've also read that running excessive preload on the shock can cause the same buck/kicking action and it got me wondering. Is it the same forces at work in both cases, being that the rear is slightly high and as such doesn't absorb the impacts as well as it otherwise would. Would running a few more mms race sag in his case then restore the balance?

 

It seems to me that both ends 'ride height' can be used to balance the stance of the chasis. A balance that favours the rear will take more effort to initiate into turns and give the bike that feeling of steering with the back wheel (under power), and added stability.

 

How do most tuners work? Start with the rear sag and then dial the fork height to the best medium, or vice versa. In my mates case I'm running the same chasis (EC250/300 2010/2011 frame) yet I have my forks pushed 8.5mm through the triple. I've also been working with the shim stacks to address my rear end kicking which seems to be taking me in the right direction. I had tried more and less preload on the shock with no real positive results, but never thought to change the front at the same time. I simply set my front to where I have the best compromise of steering vs stability. Usually gets a bit twitchy if I hit some sand or dust off the throttle, but I consider that a pretty standard reaction.

 

Thoughts?

I think you're learning a lot about setup.  All the fine tuning that makes a balanced machine takes work, never saw how some 3rd party could know where your clickers should be.

Indeed there is a lot to it when you start to fine tune. I also realised that even the difference in rear tyre, ie 110/100 or 110/90 is 10mm difference in rear ride height.

 

I guess the main question I was asking was, does the rear kicking from excessive preload have more to do with a high ride height in the rear, or the initial plushness thats lost by preloading the spring?

Don't know, I don't let excessive preload into the picture..

On a KTM they recommend about 10-12mm of preload apart from on PDS shocks

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now