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  #1 (permalink)  
Old 06-14-2006, 10:44 AM
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Cobra Make, Engine: ERA #414 427 s/o w. Shelby Aluminum heads, Edelbrock Performer RPM Intake, Mighty Demon 750, Tremec TKO 600
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Default Major wear problem with left rear tire

The fun never ends does it on these cars.....

Was looking at the tires and found the left rear severly wore on the inside portion of the tread. The tires are Goodyear big letter slicks with tread cut in to them from Roger Krause. Probably have a total of 1500 miles on them with one 2 day track event last year when they were brand new. Relatively minor track wear as it was my first track event ever!

Based on the signifcant wear vs the right rear, I have to believe this is an alignment issue of some type.

Any suggestions based on past experience? I'm also going to send the pics to Roger Krause and see what they say.

Here's the left rear and there are other worn patches around the tire, but this is the largest. All are in line on this portion of the tire.


Here's the right rear for comparison
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  #2 (permalink)  
Old 06-14-2006, 10:53 AM
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Just last Saturday I talked to Tom Barnham of Tom's Motorsports regarding the Shelby Challenge cars. He told me that he runs his camber "straight up". With Negative camber he says he finds he gets heavy wear on the inside of the tires. He was also running the Goodyear tires with tread.
Tom is the mechanic/driver who maintains, develops, and drives the Shelby Challenge cars. I saw him at the Portland races last weekend. Great guy to get info from.
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  #3 (permalink)  
Old 06-14-2006, 10:56 AM
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Do you ever have good luck?
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  #4 (permalink)  
Old 06-14-2006, 11:47 AM
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blykins - I'm just trying to be efficient and get all the bad luck done at once !
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Old 06-14-2006, 12:29 PM
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I am all for that bad luck all at once thing, been doing it a little over a year now...yikes. will it ever end?

buzz
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Old 06-14-2006, 12:32 PM
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My understanding of the ERA that you can not adjust the camber on the rear wheels for the earlier cars. I have #389 and recently had this conversation with Doug.
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Old 06-14-2006, 01:01 PM
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Wow, your getting 1,500 street miles on tires that are made for the track. I run the same tires without the hand grooving and get about 500 miles out of a set of rears for track only use.

NFN but it is a mistake to expect any kind of mileage out of these tires.

As far as the inside wear of the left rear it is common with the Jag rear to get lots of camber gain especially when doing hard cornering. Don't forget these tires are real soft and any amount of misalignment (as in hard cornering )is gonna show up in premature wear.
Do yourself a favor and buy a set of street tires and leave the race tires for the track.

If you insist on running these tires you can always go to a much stiffer FRONT sway bar. I did and it helps with the rear camber gain.

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  #8 (permalink)  
Old 06-14-2006, 01:35 PM
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Quote:
Originally Posted by JWheaton
My understanding of the ERA that you can not adjust the camber on the rear wheels for the earlier cars. I have #389 and recently had this conversation with Doug.
I think you misunderstood Doug. The camber is adjustable with shims. There is a limit to the amount of negative camber you can put in (zero shims), but it's high enough to cover just about any situation.
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Old 06-14-2006, 01:42 PM
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Quote:
Originally Posted by HSSS427
The fun never ends does it on these cars.....

Was looking at the tires and found the left rear severly wore on the inside portion of the tread. The tires are Goodyear big letter slicks with tread cut in to them from Roger Krause. Probably have a total of 1500 miles on them with one 2 day track event last year when they were brand new. Relatively minor track wear as it was my first track event ever!

Based on the signifcant wear vs the right rear, I have to believe this is an alignment issue of some type.

Any suggestions based on past experience? I'm also going to send the pics to Roger Krause and see what they say.
Improper toe-in will cause tread feathering, but that also happens with lots of track work. I don't see any of that on your tire anyway. Nor do I see uneven wear from the inside to the outside of the tire, so your camber seems pretty close. I think that the tire was internally non-uniform, causing the uneven wear.
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  #10 (permalink)  
Old 06-14-2006, 02:27 PM
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Bob
Anyway to validate that so I would have a case to go to Goodyear for a new tire? I have had the car on the track at Roebling for 2 days when the tires were brand new, and one short autocross run. Everything else has been street driving.

Racer X - I hear what you're saying, but I would think your 500 track miles equal a lot more than 1500 street miles. Plus the right rear and fronts are fine. Granted not expecting 10s of thousands of miles on them, and darn it I can't seem to accept the look of any other tires I've seen once you look at these on the car. Is there a big letter Goodyear street tire in 15"?

In any case, I guess regardless of driving on street or track, I have to accept it is a race car and will consume tires like a race car does. I've heard that's one of the key race questions "what's your tire budget?"

Heck at the rate I'm spending on engine parts and gizmos, tires look cheap!
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Old 06-14-2006, 02:54 PM
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427,
Those two days of track time is what caused most of the tire wear. I have to assume the the track you ran was in a clockwise direction and that is why you are seeing the wear on the inside of the left rear. I wear out the left rear much faster than the right simply because the majority of the turns are right handed and you are working the left side tires harder than the right.
I have thrown out a half dozen left rear tires that look exactly like the ones in your photo (minus the grooving).
I'm gonna look for pictures of my car doing hard right handers and you will be able to see what I am talking about.
I'll post here when I find them.

X
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  #12 (permalink)  
Old 06-14-2006, 04:36 PM
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Stictlyperson nailed it, unless a wheel is out of round?
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Old 06-18-2006, 09:17 PM
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I use the Goodyear Sports Car Specials G-7 (hard compound) and currently have way over 2000 miles and there are 5/32 tread remaining overall F&R. Not good in the wet though!
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Old 06-25-2006, 02:17 PM
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Default Tire size

Rick, what size are your rear tires?
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Old 06-25-2006, 05:09 PM
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6.50 X 15 on the front, 7.00 X 15 rear
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