just before winter i took off my summer wheels and this is what i found...

little illustration so you understand what i mean.



my tires were 'cupped' and were worn out pretty good on the insides. all 4 tires looked like this. i've heard that bad toe will wear out tires faster than camber and my camber wasn't really that bad with the 2" drop. the car was aligned every time i swapped these wheels and tires onto the car. i used my hatch as my daily driver and occasional auto-x racer.

what do you think this could be from?

btw... one time i did over-inflate all 4 tires by 8-9 psi right before an auto-x... i was thinking that maybe since they were over-inflated, it stretched the tire and when i went back to my normal pressure (32 psi), it caused them to 'cup'? * i think max pressure for these tires is 35 psi*

thanks


Modified by Blazin Si at 5:08 PM 1/14/2004


Modified by Blazin Si at 6:09 PM 1/14/2004

 

Bad dampers could be a cause, though the "cupping" would be a bit different from the illustration you provided.

 

You are using the term "cupping" to refer to an uneven wear patter in which the tire wears faster in the middle of the tread than along the edges. That is not how I have heard the term used.

I have heard the term "cupping" used to refer to a wear pattern in which areas of the tire tread are wearing unevenly, such that there are areas that are actually concave (been "cupped out") rather than the normal smooth surface that follows the circumference of the tire.

I found the following illustration and description on the Kaltire website:

Appearance



What's Happening

The tire is not tracking straight down the highway, but is bouncing sideways during parts of its rotation. It may be wobbling on the axle or rim. On trailers, the condition is aggravated by running empty. Because of the light load, the trailer begins to bounce, creating more irregular wear, which creates more bouncing, and so forth. The bouncing can create vehicle suspension component wear.

Probable Causes

- loose wheel bearings
- mismounted tire/ wheel assembly
- out of balance wheel assembly
- tread design/ tire design
- worn bearings, shocks, springs or other suspension compnents
- mismatched duals
- inconsistent dual inflation (10 PSI or greater)

Corrective Action

Tighten wheel bearings. Check wheel assembly for proper mounting of tire on wheel (or rim) and for proper mounting of axle. If you have many tires of the same tire brand and tread design with cupping/scallop wear, test other tire brands, tire series or tread designs. Match duals by the tire brand, size and series (differences no more than 1/4" in overall diameter). Inflate tires to fleet standard.

What to do with the tire

Continue to run tire. When worn area reaches tread wear indicators, have Kal Tire retread the tire.

 

P.S. A wear pattern in which the tires wear faster in the middle of the tread than along the edges is a classic sign of overinflation.

A wear pattern in which the tires wear faster along the inner edge than the outer edge is usually due to improper alignment.

Neither of these problems would be associated with the term "cupping".

 

no no no... i'm not really talking about how the tires are wearing out. look at the top of the tire and the bottom... the middle is sunk in and the side wall is where it should be.

i'll redo the illustration.

*EDIT*

see where the arrows are at... that's what i mean by 'cupping'. they look like this, even at 32 psi.

i'm trying to find out why it does this.

sorry about the misunderstanding... i should have clarified that at the begining. thanks for the info, though.

also, i'm using 'cupping' as a generic term since i don't know what the real term is.

 

nsxtasy has the correct information. Cupping is not the term for what you're trying to describe.

 

You are saying that the center of the tread appears "sunken" relative to the edges (which could be because the center of your tread is wearing faster than the edges, or it could be because the tire is underinflated). Does it look this way when the tires are fully inflated, or only when you have them off the rim?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">
You are saying that the center of the tread appears "sunken" relative to the edges (which could be because the center of your tread is wearing faster than the edges, or it could be because the tire is underinflated). Does it look this way when the tires are fully inflated, or only when you have them off the rim?
</TD></TR></TABLE>

correct... that's what i mean... and the tire looks like this while on the rim at 32 psi when the max tire pressure should be 35 psi.

i've checked my tire pressure several times and it will be 32 - 33 psi, so that has to be right. maybe it's possible my guage is off, but the tire feels very firm.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Blazin Si &raquo;</TD></TR><TR><TD CLASS="quote">the tire looks like this while on the rim at 32 psi when the max tire pressure should be 35 psi.</TD></TR></TABLE>

Remember, you don't want to inflate your tires to the "max pressure" shown on the sidewall, but rather, to the pressure recommended by your car. At least, this should be your starting point, and you can adjust from there - particularly for track use.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Blazin Si &raquo;</TD></TR><TR><TD CLASS="quote">i've checked my tire pressure several times and it will be 32 - 33 psi, so that has to be right. maybe it's possible my guage is off, but the tire feels very firm.</TD></TR></TABLE>

It's possible that you are inflating to the wrong pressure, as noted above. It's also possible that your gauge is indeed off; I would suggest you check it using other tire gauges, to find out. (The tire might feel very firm even if it is overinflated - in fact, even more so.)

 

i don't have these wheels at my house right now, as they're being used by my buddy as temporary replacements for his wheels. otherwise i would take digital pictures of them to show you.

it's not a big concern to me right now since these tires are about spent and i am in need of new ones, however i would like to figure out what the problem is and correct it so i don't ruin a new set of tires the same way.

 

i had the same problem with my old snow tires. The center of the tire was more worn than the outside. Every time I checked the psi it was always to spec (30psi) or lower. This was on a completely stock car too. weird.

 

In checking your tire pressure, keep in mind that pressure increases about 1 psi for each 10 degrees F in temperature. This could have an effect in either direction if you don't adjust for it - for example, the pressure could read high if you measure it in a heated garage before starting out driving at a time of year when temperatures are cold, or it could read low if you measure it first thing in the morning for a car parked outside when nights are cold and daytime temperatures are warm.

 

if it's not overinflation causing wear in the middle... could it be that your wheels are too wide for the chosen tire?

 

If the wheel was too wide, the sides would wear faster than the center becasue the carcass was stretched open. Too wide a tire on too narrow a rim would wear the center faster.

Regarding the snow tire comment above, if the snow tire was a bias ply then it could explain why the center wore too quickly even at the right pressure. Bias ply belting direction in the carcass will generally want to make the inner carcass more rounded in the center than a radial. Just a thought.

 

the tires were Nitto NT450's 205/50/15's and the wheels i use are Rota Slipstreams 15" x 6.5"

the most wear is on the inside of the tire. the middle of the tire is a little better and the outside of the tire still has some threadlife left.

it's not that the middle is necessarily worn out the most, it's just that it's 'sunk' in compared to the side wall.

that one time i did over-inflate my tires, it was pretty cold out in morning (60 degrees) and it did warm up later, maybe to about 70 degrees... so it could be possible that they stretched somehow, and when i went back to my normal pressure, the middle of the tire sunk in.

 

On a side note: You have 30% tread on the outside and 5% tread on the inside. This is most likely from too much neg chamber. Run less chamber, or go to more auto-x events to wear the outside more

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 57STS &raquo;</TD></TR><TR><TD CLASS="quote">On a side note: You have 30% tread on the outside and 5% tread on the inside. This is most likely from too much neg chamber. Run less chamber, or go to more auto-x events to wear the outside more </TD></TR></TABLE>

i've heard that bad toe causes uneven tread wear... not always camber.

i need to do more autocrossing. and some HPDE's.

 

toe by itself will just cause faster tread wear. If camber is zero but you have toe out of wack, it will wear the tire down evenly but faster than it would with zero toe. Neg camber will get you uneven tread wear like your showing in the fig. If you have too much toe AND too much camber it will wear uneven and do it at a fast rate. This might be the case for you.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Blazin Si &raquo;</TD></TR><TR><TD CLASS="quote">
the most wear is on the inside of the tire. the middle of the tire is a little better and the outside of the tire still has some threadlife left.
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It just sounds like you have a toe problem, did you do an alignment after lowering your car? (you said you lowered it 2")

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MightyMouseTech &raquo;</TD></TR><TR><TD CLASS="quote">

It just sounds like you have a toe problem, did you do an alignment after lowering your car? (you said you lowered it 2")

</TD></TR></TABLE>

yeah, it's aligned several times... every time i switch from my stock steelies (winter) to the rota's (summer) i have it aligned. i've done that a few times now.

what i might just do it get new tires and when i get aligned with the rota's, i'll have them ignore camber and correct the toe if it needs corrected.

i've never seen a tire do this before and all 4 of my tires did it! if it were one, i would blame it on Nitto for putting together a bad tire.