Kart develops understeer during the race

[Anonymous]

Hi all, I currently race a 2011 CRG Tork chassis in the LO206 class at my local track. The past couple of races I have noticed my kart has really fallen off in terms of front grip after about 5 laps. The kart feels great for the first 5 laps and has good turn in, however it develops a bad understeer. Any thoughts as to how to correct this?

 

Current setup:

Front wheels: all but 1 spacer out

Rear width 52″

Minimum caster/max camber setting

toe neutral

tire pressures 12 all around on hot 90 deg. day

tires: bridgestone YLC

1 seat strut on left side of seat

Front bar in and flat

 

Current thoughts:

Move weight from rear of seat to front under legs

move front wheels out final spacer

Increase rear width

 

I know the other answer should be increase caster, however I found that I got better exit speed when I took it out.

 

So, any thoughts?

 

[Martin A. SecrestParticipant]

I hate to ask this, but how old are the tires?

Or, have you tried 10 lbs in the front?

[Anonymous]

Valid question. When this first developed that was the first thing that I changed. So the tires only have 2 races on them since changing them did not fix it. As for the TP change, I think it has more to do with the rear’s being stuck to the track as compared to the front not getting enough grip, if that makes sense. Im willing to try some different TPs though.

[Martin A. SecrestParticipant]

Yes you could loosen the rear and that might take care of it.  In a roadrace kart two races can be the limit on front tires, depending on the track; as always, it could be a combination of factors.

[Jim SilverheelsParticipant]

Matt, what happens is the rear wheels heat up and get real grippy. They overpower the fronts, making a push. Give the front end more positive camber which makes the inside tire lift for a longer duration through the turn stopping the push. Works for us every time. Learned that from Mr Koyen.

[Anonymous]

Thanks Jim I am going to have to give that a shot. Luckily this weekend is open practice so ill have a lot of time to try different things out.

[Rod HawkinsParticipant]

Had similar situation in my kart this weekend. A couple things helped and my thought process (I am still learning).

Dropped tire pressure from 11 lbs to 9.5 front and 10.5 rear. ( the fact that it handles well for 5 laps then goes off on a 90 degree day tells me this could be an issue).

More negative camber

I could have widened the rear, but I was already at max.

Also a stiffer front torsion bar (I didn’t have that available).

Also possible to widen front track?
Maybe raise front of chassis?

[Paolo Nunzio LicaryParticipant]

Check your hot pressures. If your fronts are raising much more than the rear, take grip out of the rear according to the setup guide from your chassis manufacturer. Jim is spot on.

[Author]

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