Scaling sprint kart

When setting up scales to weigh a sprint kart how close to level do the scales have to be 1/8"? 1/16"? I have a 4' spirit level - not sure if this will be accurate enough. I am planning on shimming 4 scales as close to being in the same plane as possible on a concrete slab. I'm not looking to be 100% accurate at this point - just want to make sure it's not way off.

Do I need to determine corner weights or just front/rear weights and cross percentage?
 

XXX#40

TRUMP 2020
When setting up scales to weigh a sprint kart how close to level do the scales have to be 1/8"? 1/16"? I have a 4' spirit level - not sure if this will be accurate enough. I am planning on shimming 4 scales as close to being in the same plane as possible on a concrete slab. I'm not looking to be 100% accurate at this point - just want to make sure it's not way off.

Do I need to determine corner weights or just front/rear weights and cross percentage?

The scales need to be 100% level.
Need the percentages, individual wheel weights will be what they are
 

sundog

Member
They need to be level with each other too and your tires have to have the same roll out at the same pressure. Get it as close as you can.
 
I am planning on aligning the kart first, set tire pressure and center and lock steering. The tip that has been mentioned previously to scale the kart, and then rotate the kart 180 degrees and rescale as a check seemed like a good idea. This time around I am not looking to get it perfect - I just want to make sure I'm not way off before we go to the track. The kart has adjustable front shims and the manufacturer says changing even one shim on the front can change a corner weight by ~5 lbs so I can see the need for accuracy.
 

XXX#40

TRUMP 2020
I am planning on aligning the kart first, set tire pressure and center and lock steering. The tip that has been mentioned previously to scale the kart, and then rotate the kart 180 degrees and rescale as a check seemed like a good idea. This time around I am not looking to get it perfect - I just want to make sure I'm not way off before we go to the track. The kart has adjustable front shims and the manufacturer says changing even one shim on the front can change a corner weight by ~5 lbs so I can see the need for accuracy.

you don't have to rotate the kart.
way off or a little off will effect your experience, get it perfect to what they say you need
 

Ted Hamilton

Design Drafter / Racer
I leveled my scales with linoleum tiles, using a 4' level. ILAR method. Set all adjustments to equal, didn't worry about rollout --- it's a sprint kart, and I hadn't stretched any tires. Set pressures equal in fronts, rears. Sat in seat with all gear on, recorded weights. Later verified on a set of electronic scales at a kart shop and was within a pound of my Wal-Mart cheapie analogs. Good enough for me. Add weights where needed to get L/R to 50/50 and F/R to 42/58 IIRC. Manufacturer will spec best numbers. The old method for adjusting corners was a big 2x4 wedged in the front Y and tweaked appropriately with your buddy standing on the frame, opposite side. Usually camber wasn't adjustable, so you did the best you could to get corners equal with chassis tabled (aligned on surface plate and even) and shims in the spindle yokes.
 
So I got the postal scales and made some leveling pads out of particle board and furniture leveling feet. Seems to work pretty well. I am about 15lbs heavy on the right rear - I have lead on the seat I can move to the left. The front is a little light and I can move the engine forward a little bit and maybe put a small puck on the floor pan.

We did have hopping during the season when the heavy right rear was the inside wheel on a big sweeping turn. We narrowed the front and it helped - but we are also not getting a lot of wheel jacking out of the front. Would getting the kart more balanced help that right rear tick pick up?
 

flattop1

Dawg 89
Particle boards and furniture feet may not be stiff enough.
any flex is going to translate into skewed numbers .
 

Ted Hamilton

Design Drafter / Racer
Hopping may indicate TOO NARROW at front. A wider front will create more leverage at the rear, to a point. I'd get corners balanced as well as possible, then use seat position to ensure proper jacking via Cg. And then I'd use width adjustments to balance grip. I'd find the manufacturer's baseline and then adapt as needed for body type variations and hp variations.
 
I am going to try a slightly wider front the next time at the track. And more caster. The right side of the kart needs to go on a diet too. Does anyone get the RR and LR on an LO206 close to the same? Seems difficult ...
 
I am going to try a slightly wider front the next time at the track. And more caster. The right side of the kart needs to go on a diet too. Does anyone get the RR and LR on an LO206 close to the same? Seems difficult ...

I'm NO sprint race guy know nothing about it, BUT trying to understand why would you widen front track width to reduce grip then add caster to put grip back in ? or are things that much different in the sprint kart world ? Curious trying to understand !
 

Ted Hamilton

Design Drafter / Racer
Castor affects rate of jacking... more castor would un-weight opposite rear more quickly. Wider front jacks more as there's more swing, but more scrub. Also better leverage. Higher driver promotes picking up rears...
 
As I understand it the goal is to cure A hopping issue, I get the widen front track width,But I can't see how adding caster that effect would be that much different from oval racing to sprint racing that adding caster is going to fit in with the end goal, like I said I know NOTHING about sprint set-up so not trying to sound like I do and maybe I'm being pig headed but if all these Adjustments are made and it cures a Hop it would surprise the heck out of me, in oval racing on dirt hop is caused by to much grip at a corner that it grabs then releases then grabs then releases creating a rhythm end result a hop so again can not see it being much different just because it's in a sprint kart.
 
I was going to try more caster to see if we can get the inside wheel to lift on corners (also just curious how it would work). We did cure the hop last year by narrowing the front a little bit so I'm really not sure what is going on.
 
I was going to try more caster to see if we can get the inside wheel to lift on corners (also just curious how it would work). We did cure the hop last year by narrowing the front a little bit so I'm really not sure what is going on.

Curing it by narrowing the front tells me the hop was being cause by the rear tires thus it helped, I can see that happening in that case, I'm still not seeing the current approach working, I hope I'm wrong and you get great results.

Good Luck !!
 
Old Kart Dad... where do you race and what make kart are you racing? Sometimes a chat on the phone will clear a lot of things that are not understood.

shoot me an email and a phone number.. I will give you a call if you would like to discuss some of this stuff. Mike, mikimmotorsports@gmail.com
 

Jimbo

A trial w/o witnesses is like racin w/o tech
If it hops turning left move the Rt rear out and if it hops turning right move the left rear out.
Wider rims will help.
Depending on the tires and track grip, make air pressure adjustments
If you are a big guy get the center of gravity lower. Drop the seat. Use a lower motor mount.
If you have a rear torsion bar try putting it in.
It's a lot of work but if you kart doesn't have one, you could try installing one.
 
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