Part of Tuning your Go Kart is getting the cross weight correct. Before we get too far into this conversation, every go kart and driver combo will have a slightly different cross weight.
Hit the High Points on Cross Weight
- Cross Weight and my Go Kart
- Adjusting Cross Weight
- Which way do you move washers to adjust Cross?
- Go Kart Cross Weight – Affects You Will Feel
- What other Adjustments Affect Cross?
This is what makes racing fun and challenging. A Chassis manufacturer will recommend a cross setting for a good starting point. This may work for you, or you may find that to be fast you need to deviate from that setting.
I want to help you understand some key information about cross weight adjustments to help you be a Better Karter at the track!
First off we cannot have a discussion about cross weight if we don’t know what it is!
Cross Weight and my Go Kart
What is Cross weight?
Cross weight = (LR + RF) / Total Weight
Cross weight is calculated when the go kart is at race weight. So, this includes driver, fuel, oil, helmet, shoes, suit.
The calculation is kind of pointless really. Most scales today will do this math for you but just like in middle school one day you may have to show your work.
As you can see the LR, and the RF weights are added then divided by the total weight of the go kart. Giving you the percentage of cross you have in the go kart.
You can find an additional description of how cross works here.
Adjusting Cross Weight
There are a couple different ways to intentionally adjust cross and some you may not think about that will adjust your cross weight.
Remember the cross is the LR wheel weight and RF wheel weight combined. Anything you do to raise the LR or RF will increase cross weight.
Similarly, if you lower the LF or RR this too will increase cross.
Right about now you are looking at your RF “suspension” and saying how in the hell am I going to raise or lower the tire! There is no suspension!
On racing go karts the spindle is centered in the yoke by washers above and below. Moving washers from the top to bottom or bottom to top is your ride height adjustment.
The best way to adjust cross weight is the movement of washers on the RF.
Which way do you move washers to adjust Cross?
Remember Cross Weight is the percentage of weight the RF and LR are holding compared to the total weight of the go kart.
On a go kart if you raise a tire, that tire will be carrying more weight.
This may get confusing but, moving a tire down raises the chassis higher. This will cause that corner of the go kart to be carrying more of a load.
Moving a washer from below the spindle and putting it above the spindle will cause the RF corner weight to be heavier.
When to Adjust Cross Weight
The best time to adjust cross weight is while you are scaling a go kart. It is best to put the go kart back on the kart stand. Once on the stand remove the tire, remove the king pin bolt and then move your washers.
You want to avoid moving washers around and hoping for the best. Once you move one washer either up or down you will see a change in the RF and LR weights.
Does that mean you have to have your scales set up all the time?
Practice on your scales at home. Move a washer above the spindle and then move one below the spindle.
Document the numbers and how much the numbers change. When you go to the track, and you want to make a cross adjustment you will know what that change is doing without setting up the scales.
Go Kart Cross Weight – Affects You Will Feel
Now you have a good idea of how and when you will adjust cross.
That doesn’t really do you any good if you do not understand how that will affect your go kart.
In racing there are a lot of variables that go into a set up. The best test is consistency. Be consistent with your changes. When learning, be sure to make one change at a time and document the change!
Documentation cannot be stressed. You can’t remember what you had for dinner yesterday. Do you really think you are going to remember you dropped a 1/2 percent of cross and the go kart pushed like a dump truck?
Yeah, I didn’t think so.
Go Kart Cross Weight – What Happens When Increasing Cross
When you increase the cross-weight percentage you are increasing the bite of the LR and RF.
This is in static conditions. Dynamically cross will accomplish different effects on entry and exit of the corner.
Loose in Tight Off – Raising Cross Weight Percentages
This is a potential scenario for when you increase cross. Let’s assume the front of the go kart is turning perfect. The Caster and the Camber adjustments are spot on, and we have no troubles turning into the corner.
More weight is sitting on the LR compared to the RR. The go kart turns in and weight is now being transferred from the LR to the RF and LR to the RR. Due to the solid axle the inside rear wheel needs to lift to help the go kart turn.
Weight has left the LR tire and moved to the other corners of the go kart. Thus, allowing the go kart to lift the LR tire and turn the corner.
On corner exit the steering wheel is returning to the straight position. The weight starts to move back to where it came from. This increases the bite of the LR of the go kart. This gives the LR more grip than the RR.
If this happens before the go kart is completely out of the corner the driver will complain the go kart has a push or understeer condition.
There are a lot of factors that go into cross adjustments. A LOT!
What other Adjustments Affect Cross?
There are other ways to adjust cross other than moving those dang washers.
A go kart is a rigid frame that will bend and twist. Anything you do to raise a corner higher than another will affect the corner weight on the go kart.
Adjusting Cross with Tire Pressure
For example… If you add 5 PSI more air pressure to the LR tire you will increase cross.
Just 5 PSI of air will make that tire larger than it was. A larger tire will carry more weight because it raises that corner of the go kart. The circumference of the tire is a major tuning tool that you can learn more here.
Adjusting Go Kart Cross with Camber
Camber is another adjustment that will affect cross. I go in depth on Camber here. You can learn what camber is and how it will affect the go kart.
Increasing negative camber on the RF will lower cross. Increasing positive camber will add cross.
This adjustment is not for adjusting cross! This is an adjustment that has an effect on cross.
Static Weight Adjustment
Because we have to follow rules in karting it allows for another adjustment. Most go kart racers will have to add weight to make the minimum weight.
For example, if you are racing in the WKA 206 Senior 360 you will have to weigh 360lbs go kart and driver combined.
If you only weigh 345 with the go kart at race weight, then you better find some large rocks or something!
No, lead is the legal weight used. You will have to add a little over 15 lbs to make race weight.
If you add the lead weight to the LR of the seat, cross will increase. If you add the weight to the LF area, cross will decrease.
The easiest test is to put the go kart on the scales and move the weight around. When we were kids, we sometimes had 30 pounds of lead in our lap while sitting on the scales. Usually with our Dad yelling at us to stop squirming you’re affecting the numbers!
Weight Jacking Screw
While the above-mentioned adjustments are common to all go karts, this one may not be. On some chassis the LR bearing cassette will be slotted. There is an adjusting screw on the top.
You will bust the jam nut loose and either tighten or loosen the screw. This effectively raises and lowers the cross by lifting and lowering the LR corner.
Cross is a Delicate Relationship
Setting, Adjusting, and Fine-Tuning Cross may be difficult at first. What you will find is that once you find the sweet spot, there won’t be much tuning you will need to do. The fine tuning can be done with air pressure.
Best practice is to get out there and try it out. Adjust cross and see what the go kart does. Then be sure to document the results so you know what to do next time!