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05-09-2019, 11:27 AM | #89 |
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Not to hijack this thread, but here's my front and rear passenger tires after 3 days at COTA, 1/2 day at MSR Cresson, and 1 day at Autobahn CC. Also had about 4-5k worth of street miles on them.
Up front there's still a decent amount of wear on the outside shoulder, but also some inside shoulder wear. Car is -2.0 camber all around. Going to take it to the guys at Texas Track Works for a more aggressive alignment. Any thoughts? Rears seem to be wearing more evenly, and the wear is fairly even on both sides of the car.
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05-09-2019, 01:58 PM | #91 |
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Yeah, what are your toe settings? That inner wear looks like toe + camber wear probably just from normal driving. I wouldn't worry about it since the track miles will probably wear your tires before that inside shoulder becomes a problem
For optimum camber it's probably best to buy or borrow a pyrometer and measure hot temps across the tire, shooting for around 5 degree increase from outside to middle, and middle to inside (hottest temperatures on the inside). I have this one https://www.amazon.com/Joes-Racing-5.../dp/B005JVFTTM It's not perfect since whichever turn you took last will influence your measurements, but it's better and quicker feedback than using tire wear alone. -2.0 is probably good for the rear if you're getting even wear. That seems to be around the range people run. But I imagine you'll need at least -2.5 in the front, maybe more depending how much you're limiting body roll and loss of camber, etc. Strut cars tend to need more. I've heard stories of Porsche Cup cars running in the range of -5 degrees up front. I was getting even wear across my Rival S in my Miata with -3.5 deg, and that's on a double wishbone car, albeit for autocross and not the track. |
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05-09-2019, 03:57 PM | #92 | ||
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Car is aligned to GM's "competitive driving" spec which is an aggressive street alignment but definitely not purely for track use since they know owners can't move the alignment back and forth every time. Plenty more room to dial in negative camber (guys can get -2.5 or more on stock suspension) but I'm going to let the shop handle it since they do nothing but race car prep. Just thought I'd get some extra opinions. I wouldn't say the tire wear is really that bad, all things considered.
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05-09-2019, 04:06 PM | #93 |
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Oh that's for your Vette? What range of adjustment do you have up front?
Guess any inner wear you see must be from the camber then. Gotta make the same choice as everyone else then, whether you want better street wear or want to avoid burning through tires at the track from outside shoulder wear. I would think if you're doing more than one or two track days in a year, and not daily driving it, it'll be worth optimizing for the track |
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05-09-2019, 05:57 PM | #94 | |
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There are guys who get -2.7 on the stock suspension, no extra parts needed. I don't think 5-6 track days is that bad given the corner forces this thing pulls. 3 days at COTA is going to be hard on any tire.
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05-10-2019, 06:56 PM | #96 |
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Officially done with the 275/30/19 today
This interesting thing here is that the tire corded the inside, not the outside. Wait... there is more, it corded only half the tire, the other half looks like the outside. Today was half day wet but in the afternoon we had open track and semi dry track with spilled oil to make it interesting so I got two sessions of ~40 minutes but ran out if rubber and couldn't do the third open session. This was a Honda S2000 day. I got to know the leader if the group last year, so he let me snick into his S2K day. Best times was in the 1:40 All three pictures are the front passenger. First and third are the inside. the middle is the outside. The outside was uniformed but the inside was corded on half the tire, while the other half was used, but not abused. Good time |
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05-10-2019, 07:31 PM | #97 | |
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05-11-2019, 06:48 AM | #98 | ||
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Camber at -2.9 seems to be good for the outside. Can Toe settings be a good direction? I know we set it to mildly point outward. |
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05-11-2019, 07:51 AM | #99 |
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camber doesn't seem too aggressive, and i don't see any feathering just eyeballing it, but double check the toe. is the car still pushing in the corners?
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05-11-2019, 08:22 AM | #100 | |
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With 3rd gear I can peel off the rubber of any tire, so I managing the long turn on 4th gear. The suspension is now tuned to die for. It is truly amazing to drive this car. I will be posting few videos after my 5/19 trackday now that I got my in-car studio to work. Back to tires wear, At pace of 1:43-1:50 the tires survive and evenly consumed on all 4 corners and inside and out. Just the way I want it. And 35 PSI "warm" seems to be a key contributor But... on pace, 1:38-1:40 it develops this inside issue that I have to solve. |
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05-11-2019, 02:22 PM | #101 | |
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That's a toe issue, if I had to guess. Or that portion of the tire is rubbing on something under the car (loose fender liner, suspension piece, etc).
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05-11-2019, 03:32 PM | #102 | ||
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For -3.0 camber, what should the toe be? I will have to bring it into the dealership and tell them what I want. I can't get to ACM before the next track day. |
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05-11-2019, 04:14 PM | #103 | |
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There's no correct answer. It depends on what kind of handling characteristics you want. You can't find another alignment shop?
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05-11-2019, 04:19 PM | #104 | ||
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05-12-2019, 04:31 AM | #106 |
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Mostly track and 140 miles round trip to the track. -2.9 camber
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05-12-2019, 02:47 PM | #107 |
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You don't know your current toe settings?
Slight toe-in would reduce the inner wear the most, given the camber, but nobody really wants front toe-in for track/performance drivin. So, we generally go with zero front toe as a compromise, instead of slight toe out. |
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05-12-2019, 03:54 PM | #108 | |
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I am not willing to eat up the inside just to win my HPDE session. |
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05-13-2019, 09:46 AM | #109 |
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Running a lot of negative camber with toe out will wear the tire wicked fast.
I ran a little toe out (1/16" per side/1/8" total) when I was at max stock camber but not at -2.5 camber. The added negative camber will dial out most of the understeer inherent to the car. General statement...Driver's can also induce understeer and alignments won't fix that.
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05-13-2019, 04:49 PM | #110 | |
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This is what I have now. Will see tire wear with this setup . . |
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