RR tire wear

2004 Nemesis asphalt oval Yellow vega no prep 12psi right 10psi left
front 46% left 58% cross 59% Caster 10 right 8 left Camber -2,5 right 0 left Toed out 1/16"
The RR is hopping at corner exit and there is excessive tire wear on the inside edge of the RR tire.
-Any ideas?
 

CMR4749

Member
I had a 2004 nemesis that I ran on asphalt. I would try 10psi on the right side and 9psi on left front and 8psi left rear. Also +1 left front camber and 3.5 right front camber. Get the cross around 63-64%. Move right rear out as far as it can go and try and tuck the left rear in. Front stagger 1 1/4. Rear stagger 11/2
 

CMR4749

Member
Thanks for the feedback. I will try air pressure first. We race tonight so i will post my findings tomorrow. What about a wide RR hub?
No problem anytime let me know how you make out. Start with small adjustments first. Also go with standard rr hub like flattop1 said it will stiffen the axle and you don't want that on ashpalt
 

CarlsonMotorsports

Site Supporter
I've always found that stiffening the axle helped prevent the hopping and helps unload the LR.
For syrup we even ran a stiffener from the RR bearing out to the hub.
Maybe I'm thinking of this hopping problem differently than others.

More left side percentage first and foremost. More psi split.
Depending on when the hop starts, would tell me what direction to go on air. More psi will build tire temps quicker. Less will delay it.
How much psi increase are you currently seeing (cold to hot)?
A properly cut tire to flatten the contact patch and stiffer shoulder will help as well.
Some internal prep to help control the heat can help tremendously, but it won't make up for an ill set-up chassis.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
I've always found that stiffening the axle helped prevent the hopping and helps unload the LR.
For syrup we even ran a stiffener from the RR bearing out to the hub.
Maybe I'm thinking of this hopping problem differently than others.

More left side percentage first and foremost. More psi split.
Depending on when the hop starts, would tell me what direction to go on air. More psi will build tire temps quicker. Less will delay it.
How much psi increase are you currently seeing (cold to hot)?
A properly cut tire to flatten the contact patch and stiffer shoulder will help as well.
Some internal prep to help control the heat can help tremendously, but it won't make up for an ill set-up chassis.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
33 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
Interesting thought on the stiffener and would something pretty easy to test back to back and measure results.

I agree with more left and starting air pressures lower, especially if the hop comes in mid race when the tire temps increase and PSI builds.

The other thing that would be worth a try is sliding your RR hub out in 1/4" increments and see if that helps with the hop.
 

CarlsonMotorsports

Site Supporter
Interesting thought on the stiffener and would something pretty easy to test back to back and measure results.

I agree with more left and starting air pressures lower, especially if the hop comes in mid race when the tire temps increase and PSI builds.

The other thing that would be worth a try is sliding your RR hub out in 1/4" increments and see if that helps with the hop.
On soft axles, sliding the hub out increases the axle flex and resultant "hop." Think about it as a leverage point from the bearing to the hub. This is a reason we use 4" offset wheels instead of 5" right sides, or centered up wheels (like the pavement guys would.) Oval karts run the right rear all the way in against the frame. Part of the reason for this is to eliminate axle flex, or at least limit it's effect. Our Vector DO chassis actually has the motor rails swapped so that the engine sits outside of the main frame rail and you can move the RR in further with likely the narrowest rear tracking of any kart in the industry. In reality, (with the exception of grass tracks or ice racing) we never needed the right rear in that far, but instead ran it further out on the axle. This the cause the right rear to bite up hard (acceptable for big HP or even very low HP) but was not fast when you needed a more balanced car on a track that has much bite at all.
We used to run aluminum axles (back in the 80s-90s) and readily felt this "seat of the pants." Same with thin wall axles compared to thick wall. It wasn't until we got on syrup where we had a ton of grip that we needed to go to longer RR hubs. Axle stiffeners ranged from stacking lock collars to pipe sleeve to a hardwood dowel rod driven inside the axle and pinned. I believe Jeff @ Rage has a spacer/sleeve kit available still. Lots of stuff has been tried over the years to "tame the hop." My understanding is that the axle is loaded/flexed to the point that it rebounds, or snaps back, and causes the grip of the tire to be released, resulting in the dreaded hop. I could be all washed up on this idea, but it's certainly played out like that over the years that we've built karts. :)
For sure, most chassis like the thin wall axle for pavement, and we reccomend them as well, but sometimes you've got to think outside of the box.
 
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