front tire studder off power in corners

[rm6keith]

I am on a KTM450SMR on a track with slicks.

When I go into a fast corner off the power, the front tires studders, if I get back on the power it seems fine.

I do not want to have to go under throttle on every corner, sometimes you have to slow down!

Keith

Originally the front was sliding at all speeds, I dropped two lbs air, softened two clicks compression and increased two clicks rebound. Helped quite a bit, but now the throttle chatter is getting me confused.

If you now something about suspension tuning, I would really appreciate your advice. Thank you.

Edited October 7, 2011 by rm6keith

[tgrundy131]

If you are not a suspension expert, please guess to yourself. Thank you.

Prolly turns alot of people off, just say'n.

Give us some sag numbers, your weight, and spring set up on your bike, and maybe one of the experts will chime in.

[Tmall]

If you are not a suspension expert, please guess to yourself. Thank you.

Experts cost money. You want free advice, you get what you pay for.

If you don't want "non-experts" posting, then a public internet forum is probably not your best bet to start throwing around conditions...

[rm6keith]

Sorry about the poor wording, I just did not want to go in 4 different directions. (Check original posting edit.)

I have the stock springs in, 17 clicks of rebound and 12 clicks of compression. I am 160 without gear, sage is 4".

I am using Dunlop 208 slicks, the front is the dual compound, soft in the rear. I hear this is a common problem with supermotos on the track and was hoping someone else has experienced this, and I could share the results with the other guys too.

[tgrundy131]

Do you have any dirt background, or only supermoto? I know NOTHING about setting up a dirtbike for supermoto, or if it is the same for dirt or not??? But I can point you in a direction for chassis setup for dirt. What I did is to run a formula posted by one of the Thumpertalk members (Dwight_Rudder) on front and rear sag. I can tell you that 4" of sag is kind of non specific. You need some good numbers in millimeters for static, and rider(race) sag front and rear. I will post Dwight's formula next...it was VERY helpful.

[tgrundy131]

Here is a copy of Dwight's post explaining his formula for sag.

I have come up with a formula that I use for setting the suspension up on my bikes. This info was collected the past few years from several different tuners and applied. I have broken this down into a formula using percentages of available travel so this will work on most any bike. (KTM PDS is slightly different but close). I thought I would share this knowledge with you.

Your shock spring preload should be less than 10mm on linkage suspension but not less than 5mm. You don't want to over preload a weak spring as you will just get a harsh ride that still will allow hard bottoming. I usually shoot for about 5mm preload on fork springs. If you have the right spring.

You can figure your correct sag numbers by using percentages. That way you can get the correct springs for you and your bike. Base these percentages on the available travel front and rear with a variance of + - 2 mm.

Front suspension static sag should be 14% ( available travel in mm X .14 = static sag in mm)

Front suspension rider sag should be 25% (X .25 = Rider sag)

Rear suspension static sag should be 11% of available travel (X .11 = static sag)

Rear suspension rider sag should be 34% of available travel (X .34 = rider sag)

Using these principles you can figure the correct sags for any bike and thus the correct springs without guessing and compromising.

[rm6keith]

I have no dirt background at all. The bike is not a dirtbike either, it is a factory KTM Supermoto. I came right from the factory with 17 wheels with slicks mounted, it is valved for supermoto and not dirt.

Thank you for the info on sag for the front forks, there was nothing in my tuning book on this.

It is possible the front studder is rider technique and I need more weight over the front end? I was wondering more if more rebound would solve this, or if it is possibly the dual compound tire should only be used in the heat of the summer and not this time of year? Or if I should try softening up the compression? Since I leave for my final two races of the season tomorrow, I will be trying the above. I was hoping for a little advice before wasting time going in the wrong direction.

[mog]

do a search on google for road bike suspension tuning guide , as this is something I have heard of in road bikes and yours is similar with the slicks

[Windblown]

Off the power and on the front brakes or just off the power?

[crofrog]

Sit farther forward. My smr chatters like no other when you aren't far enough forward. If you get the weight in the right place you can keep the front brake on all the way to apex dragging pegs.

Also, you shouldn't really be "off the throttle" either on the throttle or on the brakes.

[rm6keith]

I ended up getting it sorted out! The weekend went fantastic. I went to a soft compound front, increased the rebound to 16 clicks, and lowered my tire pressure to 23.5psi. (one lb lower).

I think I may not have been getting far enough forward either.

For the other post. It was not doing it on braking, just letting off the throttle in the turn. This is my first season and I am not sure I can be on the gas or braking only just yet.

Keith

[crofrog]

The softer tire is likely just hiding a rider error ?

[cardinale199]

try 16.5 wheels!!!!i work at race whit pmr h2o world championship team marco governatori and thierry van den bosch 17 wheel is no good for supermoto at high level .chattering,less directionality.dunlop what mescola??950 , 465 ,417 ,6178 ,497 ??it s important

[cardinale199]

dunlop pressure 1.70 after 50 minutes warmcover