SuperMoto Junkie banner

1 - 14 of 14 Posts

·
Registered
Joined
·
321 Posts
Discussion Starter #1
Anyone have any good tips for eliminating front end chatter at full lean angle on the front?

Here's the scoop - 2006 CRF450, 22mm clamps, 16.5 front wheel with Bridgestone supermoto tire. Stock 47mm Showa Suspension revalved by Factory Connection for supermoto.

When I'm in a turn where the bike is at full lean angle, the front wheel chatters bad enough that racers behind me can see it. For example, I'm coming into a faster corner 40-50mph, brake, turn the bike in and get on the gas, the front end chatters really bad at the apex of the corner until I've started to pick the bike up out of the corner on the gas.

Also, if I'm in a sweeping corner at full lean angle holding a steady throttle, the front end also chatters.

I've tried increasing and decreasing compression and rebound dampening more than a few click and it's not helping. I've talked to Factory Connection and they recommended running higher tire pressure in the front tire. I'm currently running 24psi hot in the front.

Anyone else on a Honda have this issue?

Anyone have any tips to resolve it? Anything at all!??
 

·
Registered
Joined
·
1,487 Posts
You may want to change the weight bias on the motorcycle

Where is the fork in the clamp - pushed up in the clamp, stock or pushed down in the clamp.

How much sag in the rear?

The fastest way I have removed chatter that happens after the apex of a corner or under steady throttle is to lower the rear or raise the front 5-10mm. Try running 100mm of sag if the bike is set up a 90mm. And you can go up to 105 just for testing.

Or if your fork is pushed up in the clamp sticking out of the clamp - put it back to stock or test with just the cap poking out of the clamp.

This usually helps. or it is a good place to start.
 

·
Registered
Joined
·
657 Posts
I loved the way both the question and the answer was written, with very specific explenations of exactly when it was chattering, both where in the turn and at what throttle position the front was chattering. Same goes for the answer, very clear, detailed and specific response.
 

·
Registered
Joined
·
319 Posts
22mm clamps are for motocross, running 12-14mm clamps may also help, they did in my case. But sliding the forks up or down through the clamps as well as messing with the sag like smrscott said is a good place to start before spending cash on clamps or tires or whatever.:bike:
 

·
Registered
Joined
·
1,487 Posts
If you are riding a KTM I can understand how the 12-14mm clamps work - but you can't compare a KTM to a Honda when it comes to offset.

Clamp offset is just a number in the big picture. The big picture is overall offset - the difference between the center of the axle and the center of the steering head pivot. This along with the rake which makes up the bikes trail.

Even for supermoto 20-22mm clamps are what most teams use on the CRF. We have heard that some riders have tested less offset but they are custom or one off-clamps.

A few years back Honda moved the axle position in the fork 2mm back - which is the same a going from 24-22mm clamps. And in 2008 they went from 24-22mm clamps stock.
 

·
Registered
Joined
·
321 Posts
Discussion Starter #6
Hi Scott, Here's the answers:

Where is the fork in the clamp - pushed up in the clamp, stock or pushed down in the clamp. - Forks are only 5mm above top of triple clamp.

How much sag in the rear? - 101mm (4")

So this seems pretty much on par with what you recommend. I'll try leveling the forks with the top of the triple clamp and see if that helps, as well as some of the other recommendations you ahve. Is there any credence to tire pressure affecting chatter (which is what Factory Connection told me)? They said to try a higher tire pressure than 24psi hot.
 

·
Registered
Joined
·
648 Posts
I would drop the forks as you're suggesting. But in my opinion your tire pressure is real close to optimum and raising it will only stiffen it thus increasing the chatter. Try adding 2 clicks of rebound dampening on the front as a second option (I only make one major change at a time).
 

·
Registered
Joined
·
128 Posts
The biggest improvement I made to my '06 CRF to reduce chatter was cranking up the preload. Granted this is with stock suspension and clamps but the difference was immediate and very noticeable. I don't recall the exact amount but it had a very small amount of free sag after the adjustment. (Bike standing on it's own weight only.) Although my bike is stock, the symptoms were identical.
 

·
Registered
Joined
·
497 Posts
I also suggest increasing rear pre-load, but before raising the fork tubes. Less than 100mm for rear sag helped with more than just chatter.
 

·
Registered
Joined
·
112 Posts
Don't you want to put more weight on front if it is chattering? From what I've read in this thread, it sounds like the recommendations are to put more on the rear so far.

I have very similar chatter mid-turn and at exit. I'm going to change preload on both ends at my next track date to see what works and what doesn't.
 

·
Registered
Joined
·
213 Posts
I had the exact same problem and solved it mostly through changing my body position. I was overloading the front tire causing it to push and chatter badly, so I leaned my upper body back a little bit and it seemed to help out alot. Do a bunch of laps with the same bike setup at about 75% pace and try leaning your body different directions to see what makes the chatter worse and what makes it better.

Also, 24 psi sounds a little too high for me. Lower psi up front really helped me out.

Good luck!
 

·
Registered
Joined
·
321 Posts
Discussion Starter #14
Update: So I was using the new Bridgestone 16.5 supermoto tire but tried some Dunlops last week and the chatter went away! I didn't change anything else based on the recommendations everyone has so generously posted. One of the responses from SMR Scott was to try a new tire brand, so I did and miraculously the chatter went away. I used the same suspension settings that I always do for the track I practice at, the only difference was Marchesini Wheels and Dunlop tires.

The Dunlops seem to be more absorbent or flexible or something, but the chatter went away. Amazing.

So, what this tells me is that the tire profile and carcass has a lot to do with chatter. Why? The Bridgestones have a more peaky profile with flatter sides whereas the Dunlops have a rounder profile and what looks like a taller sidewall than the Bridgestones. Soo...it looks like tire profile has a lot to do with chatter.
 
1 - 14 of 14 Posts
Top