Track Tac

Right rear tire wear

J

jacobsdad

Member
What would cause the left rear tire to wear more than the other 3 tires? The inside edge of the tread is feathering and the tread squares look like they are feathering to the inside. Our track went to the Hoosier predator rules this year. Stock predator engines with Hoosier D20 treads. Running a 1/8 dirt track, a good momentum track. We can run wide open all the way around, especially with these pathetically slow engines and heavy tires. No prep, but my daughters right rear is wearing bad. After about 6 races the tire is half gone.
I don’t know where her setup numbers are, we started with the setup we finished with last year. Made a few small adjustments and she is running in the top 3 or 4 every week. I just can’t figure out this tire wear we are seeing.
 
Sliding is what causes increased tire wear. If the tires are wearing faster than youre use to, its sliding. Figure out why and you will be good to go. Hard to tell you what needs done when you say you dont even know what the set up numbers are.
 
If one corner of the car is seeing all the abuse, then that tire is working harder than the rest.
ie - if the RR is seeing all the heat and wear, then the car is sitting on the RR too hard, too long, etc.
Increasing cross "could" help, so could decreasing rear stagger, and left side percentage - but like Earl said, it's difficult to suggest much without scale numbers.
Keep in mind that the D20A is almost the softest tire made. Using it as a "spec" tire doesn't sound the wisest, but we see this regularly with treaded tire rules. And they're likely dictating that you run the bigger right side tires that were made for the 250 & 500cc winged outlaw cage karts (which are HUGE!) This only compounds your handling and wear problems.


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... ????? I'm visulizing a kart that you can see is laying on the right rear, rather then one which looks like it's driving around the track with ease???
If it's on the right rear, sort of leaning is one thing but it could also be on the right rear sort of hung out all around the track or turns???
And as said above if it wears more it's being used more.
And if your going to use it less use the other 3 more in a way that will get you freer and faster.
You now have a lot of grip, "Use it wisely grasshopper", before you give it away trying to fix a problem.

Too much not known but threw some thought out there below anyway.

take them all with a grain of salt ... there just thunkin bout it and that's all





I'm looking at it differently then the two above posts.
I'm thinking differently because you said she can flat foot all around the track, your using low hp and high grip.

Though it's still because of tire slip I'm looking at why the tire is slipping more so then about it being over loaded, which it is.
It's slipping because it's loaded too much, wanting to roll straight and your front tires have enough grip and turning power to over come it wanting to go straight.
And the slip is caused by its grip being twisted away from the track.

I'm going to say more stagger not less to help get some rotation/turning from the back which will also free you up and maybe get you some more speed.
More cross by getting weight to the left rear instead of putting cross in it via the right front.
And more air in the right rear and if that doesn't help also go a tad less in the left rear.
I'm guessing you couldn't get a lot of stagger in the back because of the treads.

Dumb question follows ..... did your lap times or speed increase as your right rear got half worn out?
I'm thinking maybe it did?
 
Found my notes. This year we started with Front 46 left 57 cross 60. We started with 2.5 inch stagger on the rear until I found a narrow left rear wheel, now the stagger on the back is 1 1/2. Front stagger is still stuck at 1 3/4. At the beginning she was loose coming off the corners so I loosened it up with the weight jack on the left rear until she got it handling good. Air pressure we are running is 7 left 8 right. If I was home I would take a picture of the tire, it is wearing faster than the other 3 but it is also wearing uneven. It is wearing more on the inside half than the outside half.
I almost forgot to add, she won the feature two weeks ago. That night I ran a 2 pound split opposite of the usual. I ran 10 pounds right side and 8 pounds left side. We did that because we were fighting to get the stagger down.
 
I'm wondering how much RF caster, LF caster? That LR is pretty light, but then again, changing the stagger changes the weights. I'm guessing you don't have your own scales. Stagger depends on the radius of the corner, do you know your tracks turn radius? Do you know your rear tread widths?
What's your scale weight at the track?
 
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Scale weight is 360 minimum she weighs in at 374. I use 4 bathroom scales zeroed with known 10 pound weights, but I don’t think they are very accurate. I don’t think her kart has adjustable caster. We made adjustments at the track with the weight jack on the left rear or sliding the left rear in or out. She was loose coming off the corners so we raised the left rear which gave her control coming off the turns. Not sure if that was the right way to go.
 
No caster adjustment!! How old is this kart? Do you know your weight percentages since you changed the stagger? How do you Calculate Your percentages?

I think I would use a little heavier test weight. I think most scales are within an "acceptable" tolerance.

" range Consistency is more important than absolute accuracy. Electronic scales have their problems also. If the scales for all level, that's more important.
 
It is an older Legend kart. It may have adjustments that I havnt found yet. To weigh it I found a level spot on the shop floor, checked level across each scale and corner to corner. I painted the floor so the scales go in the same place each time, each scale on the same corner each time. We haven’t had a chance to get back on the scales since changing the left rear wheel to change stagger. I have had a big project in the shop so no room to get the scales set down.
 
If you made an adjustment and it improved lap times , it worked .
As far as tire wear treads wear like that feather edge the blocks .
Flap wheel them or flip on the wheels .
Big stagger in front hinders weight transfer .
 
Maybe the wear is normal. A couple of the guys at the track noticed the wear and we were talking about it. Theirs are not showing any wear. But they are running in the back, maybe it is just the price of being fast? I was just curious if there was anything in particular I should look at. I will definitely see what I can to with the front stagger, it is still way higher than I like.
 
2 1/2 REAR STAGGER is probably twice as much as you need, maybe more. If I knew what size track you were on I would know a liittle better. Just saying 1/8 mile is not enough. If I knew what kind of kart you had, there might be a clue there. With no stagger adjustment, it's got to be an old kart and who knows what the stagger is on the left. Makes a big difference. Your L are iis lighter than most, make CRR do all the work. I know it's a pain in the butt to write all this stuff down, but it's also a pain in the butt working, as it is, with our eyes closed.
 
Treads don't stagger out well .
2. - 2 1/4 was normal for us 12/9/6 and 6/6/6 right and left worked best .
 
I wonder, on a 1/8 mile track, would 2 1/2 stagger be better than no stagger at all? Don't know the turn radius yet, no way to figure it.
 
Alvin, I don’t have the radius of the turns but on slicks we found 1 inch of stagger was where we wanted to be. I stepped the track off a few years ago but I don’t remember what I came up with. We have been running this same kart for I think 4 years. I bought it race ready from someone at our track. My son drove it as it was with a few minor adjustments. He took first place in points that year and was almost undefeated. My daughter has been using it for I think 3 years now. All we changed from him to her is weight percentages. She has finished in the top 3 every year. She is still running in the top 4 but I am curious if we could pick up a little speed if she wasn’t burning up the right rear.
 
alvin l nunley said:
2 1/2 REAR STAGGER is probably twice as much as you need, maybe more. If I knew what size track you were on I would know a liittle better. Just saying 1/8 mile is not enough. If I knew what kind of kart you had, there might be a clue there. With no stagger adjustment, it's got to be an old kart and who knows what the stagger is on the left. Makes a big difference. Your L are iis lighter than most, make CRR do all the work. I know it's a pain in the butt to write all this stuff down, but it's also a pain in the butt working, as it is, with our eyes closed.
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Dont matter how old the kart is to adjust stagger. Stagger is done with tires, not kart.
Stagger on the left? Stagger is the difference between 2 tires.
 
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