Is cross weight outdated?

[Dirtmod13]

With a lot of cars rolling around barely touching the left front, how can measured crossweight really matter? Like measuring a 4th wheel on a tricycle

[Mr.Kennedy777]

With a lot of cars rolling around barely touching the left front, how can measured crossweight really matter? Like measuring a 4th wheel on a tricycle Absolutely it matters. It changes the way spring load curve behaves on each tire. Even though it’s not touching the ground the diagonal preload in the car will determine the static load at which the tire will start increasing load from set ride height at during decel, cornering and acceleration. This changes how soon one tire reaches peak loading versus another and even though one tire is off the ground let’s say, or at least locked out on extension, the RF and RR corners are also set. So I would say it does absolutely. Some might argue, but cross also changes how hard you get into secondary suspension by adjusting the static load, either increasing or decreasing. If anything the way we are using spring pre load is evolving more with the use of secondary and even third levels of suspension. It’s in those cases it actually becomes more of a big deal because you’re dealing with a game of tenths of inches.

[MasterSbilt_Racer]

Static cross means little. Dynamic cross, at various points on the track, means everything. Always has.

[Mr.Kennedy777]

Static cross means little. Dynamic cross, at various points on the track, means everything. Always has.I agree with the second part, however, your static cross setting can greatly affect your dynamic cross greatly. Especially when secondary suspension is involved.

[Mr.Kennedy777]

If static cross means little throw 525 pounds of bite and the car without making any changes and ask your driver if static cross means little.

[MasterSbilt_Racer]

If static cross means little throw 525 pounds of bite and the car without making any changes and ask your driver if static cross means little.

Does your car race at ride height? How close to the same number is the cross on the 49 car when they go thru tech and when it hits the track and the lr deck is no longer legal?

Static only matters if it adjustments to it effect dynamic.

[Mr.Kennedy777]

Does your car race at ride height? How close to the same number is the cross on the 49 car when they go thru tech and when it hits the track and the lr deck is no longer legal?Static only matters if it adjustments to it effect dynamic. Which it ALWAYS does.

[Mr.Kennedy777]

It doesn’t race at ride height but energy is stored into your suspension there. So any movement from that point will change depending on what you have at static.

[MasterSbilt_Racer]

Which it ALWAYS does.

Let's say I got a 300# LR spring. It is unloaded all the way around the track. What difference does it make if I add 4 turns to it and it is still unloaded?

Maybe the car reaches full hike on starts .002 seconds faster? Who cares?

[Mr.Kennedy777]

Let's say I got a 300# LR spring. It is unloaded all the way around the track. What difference does it make if I add 4 turns to it and it is still unloaded?Maybe the car reaches full hike on starts .002 seconds faster? Who cares?Because that one spring isn’t the only one involved in crossweight.

[Mr.Kennedy777]

And in my experience, cross weight adjustments are more efficient being done on all four corners keeping the ride heights the same, not just one corner.

[adamsraceshocks]

If you are off your springs all the way around the track then no, it means little to nothing. I do think you need to track your dynamic and or your static cross numbers to be able to be consistent in your setups. You also need to know how your adjustments affect your transition points too. We race mods, we are on all 4 springs at some point every lap (except extreme hammer down conditions).

[MasterSbilt_Racer]

If you are off your springs all the way around the track then no, it means little to nothing. I do think you need to track your dynamic and or your static cross numbers to be able to be consistent in your setups. You also need to know how your adjustments affect your transition points too. We race mods, we are on all 4 springs at some point every lap (except extreme hammer down conditions).

I don't advocate not using your springs, just an example. My whole point was that within reason, I can make various points in travel any wheel load value I want with the same wheel load at ride height. Or I can change the ride height values and still hit the same load number at a travel value.

[Mr.Kennedy777]

Let’s say I want to make a crossweight adjustment because the car doesn’t seem to be keeping the RR under itself so well when entering the corner and it’s tight as hell once it hooks back up. I go from 225 bite down to 50 bite. Not only is the pre load split different in the rear now, but the front as well. So even if that 300 spring is unloaded around the track, I’ve also changed how the LF, RF and RR corners load up. When you’re setting things like bump stop timing, bump stop height and desired bump stop loads, your static cross weight can change the handling of the car quite a bit especially if you’re decreasing the pre load in the RF and LR corners because that extra x amount of pounds that needs to be taken up by the spring system is reduced and is now being absorbed into the bump, or vice versa. And I’m sure you’re familiar with bump stop load curves and what an additional 100 pounds into the bump can do in terms of increasing or decreasing harshness over surfaces that aren’t perfectly smooth.

[MasterSbilt_Racer]

I am well aware. There is no reason the bump has to absorb extra load. We are way past single rate spring systems. It's been 10 years since I was there.

[Mr.Kennedy777]

I am well aware. There is no reason the bump has to absorb extra load. We are way past single rate spring systems. It's been 10 years since I was there. A bump setup isn’t a single rate spring system and I’m sure you know that. If cornering force is the same, everything else is the same, except for example pre load in the RF, more or less force will go into the bump itself because more or less of the max load is “taken up” by pre load.

[Mr.Kennedy777]

If you’re talking about running a stacked spring setup with a bump, then the same thing would apply. Less initial take up in the initial spring rate, means more to take up in the second stage and if you don’t change that, then you still have more to take up in the bump.

[Mr.Kennedy777]

All things staying the same besides pre load.

[mickley.28]

All that matters is the individual wheel loads dynamically on the track.... everyone should be able to agree on that. The cross weight at static ride height you will never see when going around the track so it doesn’t matter what the static cross weight is, but changes to static cross weight will typically effect your dynamic cross weight (wheel loads).... the exception would be changes to the left rear may or may not have a dynamic effect. So I guess both of you are correct... static cross weight means nothing to how the car will handle in the dynamic state but changes in cross weight will typically effect dynamic wheel loads. I no longer consider things like cross weight or wedge in my setup because someone with 300lbs of static wedge could easily have less dynamic wedge than someone with 0lbs of static wedge. One could put ten turns in there left rear and add over 100lbs of wedge and it might not change the way the car handles dynamically at all or it could change everything. Based off what I seen this year with jds car I would be willing to bet he’s running negitive wedge numbers and the xr1s are running over 100lbs of wedge but if you could weigh each corner as it went around the track I’d be willing to bet the dynamic numbers are much closer to eachother.

[fastford]

I agree with the above analyses , all we use static measurements for is reference points , so if we go to the track and go to tuning the car and find some speed , then we go back to shop , put on scales and make adjustments to our base , static set up. I dont have a pull down rig , but i also do a static check with right front on the bump stop , with no spring and log left rear static bite , there is some things to be gained here to. MK777 and MBR , both you guy,s are sharp , theres no doubt , but i still believe you need to use every thing you can now days......