Does anyone know how to check if a frame is bent? I really dont want to pay good money for someone just to say it isn’t bent. Any tips will help! Thanks
Set it on the ground, turn the wheel full lock each direction, lift the inside rear wheel with your hand, see if one side feels lighter or not. That’s a quick and dirty way to test it.
Throw a set of Snipers on the front and see how the alignment looks too.
Measure each side from Kingpin to axle (or bearing carrier) and compare measurements. They should be the same for a sprint kart. I can’t speak about ovals.
You can do the same with diagonal checks too.
Check for a warped floortray and or mounting points that have been pushed back. This isn’t a very conclusive one of course because it’s not hard to swap a floortray.
If (and it’s a big if) the ground is level and the tires are equal circumference/inflation you can lift the front about 1" off the ground, slowly lower it down and see if the wheel on one side touches the ground noticeably sooner than the other.
I’m not super fond of checking lock to lock unless you’re really used to “feeling” it, but there’s certainly no harm in trying that along with the other checks.
Power Republic go through some of these checks in this video.
You could also corner weight it, and see if the cornerweights are just super off.
Personally, I don’t have a problem putting a kart on a frame table, if you’re concerned about it. Piece of mind is always a good thing.
Thank you James! I’ll give it a shot!
Does it matter if the engine is on or off? I did this earlier this year with it on and the rr stayed flat on the ground. Sadly I only have toe plates
If I turn the wheel all the way to the left and press down on the right front the left rear pops up. If I turn it to the right and press down on the left front the right rear does nothing. Does this mean its bent?
It’s hard to tell honestly. It’s not super unusual for that to happen especially if an engine is on the chassis.
It depends on the Caster, ride height, toe, track width, tire pressure and Ackerman being the same on both sides on the front end. Rear hubs equal distance out from the bearing carriers both sides. Same pressures left/right. Flat and level ground too. It’s kind of a feel thing even at that I’ve found it to be inconclusive.
Was there an engine on the chassis? That will have an effect as it “weighs down” the “spring” of the chassis on that side.
If the engine was off and you are able to cancel out all the variables above then I’d say there’s a chance it’s tweaked at the waist. You could use the diagonal measurement to verify
I took the engine off and did it, I measured the kingpins to the bearing cassettes and it was the same measurement, front and rear track widths are the same tire psi all the same, ackerman is the same. The toe is eyeballed at the moment. I bent the tie rod and kingpin last race when I smoked the barriers, which is why I’m concerned the frame may be bent lol. I put a new kingpin in and spindle bearings. Knocked the tie rod as straight as I can for now. Picking up a new tie rod friday
If you’re checking corner weights, you’ll want to check the front end geometry (camber, caster, toe, ride height) first to make sure everything is even. On the first kart we ever bought, I checked the corner weights and was initially thinking it was bent when the front end settings just weren’t the same on both sides.
Thank you Chris! Corner weights meaning Lf, rf, rr, Lr when I put it on the scales?
I’ve done some looking and haven’t found much about using the snipers to help in checking the frame. While it would seems this could be used on the back half of the chassis it probably won’t tell you much about the front. The power republic video mentions a chassis jig, but I’ve never seen one or plans to make one. Does anyone have that information they are willing to share?
I think they mean a chassis table, pretty sure it’s just a flat table.they are probably expensive as all hell. I took my frame to comet and they put it on their table. It was bent 1/8th of an inch. $75 for labor, but atleast its straight now
Looking for some advice. I bought a 2017 Compkart recently with an unknown past. Upon closer inspection and using some of the points mentioned in this thread, I am all but certain I have a bent chassis. The chassis has some sag in the middle, not a big deal but of more concern, turning full left the right front lifts off the ground, while turning full right does not cause the left to lift. Also when sitting on the ground with no driver the wheel takes a set to the right. It will straighten a bit with a driver but still favors turning right. I have yet to scale it or run it on the track. I also couldn’t get the Snipers to have the same caster/camber without having the adjusters almost 180* from each other. So my questions are:
When adjusting caster/camber do you usually go by the Snipers or the settings on the adjusters to make them the same left and right? Ideally both adjusters and Sniper should be the same, more curious about running with a tweaked chassis.
The chassis is rather flexible, can it be straightened and does this work permanently or will the steel have a memory and want to go back to its bent position as it is used?
Other ideas on what I should do?
Not a great sign. Sounds like something is bent. I would just double check all the tie rods, steering shaft, and spindles first to make sure it’s not one of those rather than the frame itself.
If the kart is bent and you intend on running it, I would try to get it as close to straight as possible on the Snipers, even if that means they are unevenly set. I would rather have the alignment correct than have the pills be the same. Fairly common to see pills slightly offset to account for little bends here and there on chassis that have seen some battles.
You can straighten the kart, but usually you’ll have to straighten it a couple times, as the metal will spring back after flexing and going through some on-track load.
A bent kingpin can cause that alignment issue too…
The kingpin bolts look okay (I have new ones coming). The freeline spindles also have removable axles and one has a very slight bend.
Who does chassis straightening? Is this something a machine shop or non kart business can address? I know my local shop does not have a table. What would be a normal amount to have this done?
I’ve never tried to take one to a non karting shop.
Locally 125-250 for a straighten depending on the severity.
I always check kingpins with the lasers on and turn the kingpin watching for camber movement. I’ve had them be bent but not visibly to the eyeball check.
Where are you located?
I am in Upstate NY / Syracuse. I have seen videos of people using 2x4s and jumping on the frame. I would be looking for something a little more technical than that.