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Old 09-27-2005, 09:25 AM   #1
MattSTi
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Default I Need More Camber - But How Much?

I originally posted this in tire & wheel.

After 6 track events at summit point this summer/fall I've noticed some abnormal wear of my RA-1's. The outside shoulders seem to be getting overheated and wearing more than then the center of the tire. This abnormal wear occurred with -2.5 camber up front, -1.5 in the rear, 0 toe all around. I know that I need more camber, but how much? I'm thinking -3.5, -2.5 or -2.0 would do the trick, but I don't have experience with those settings yet.

FYI I have JIC FLT-A2 7K/5k, and whiteline whiteline sways, my hot pressures are around 42-43.

Any help would be appreciated.

-Matt
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Old 09-27-2005, 09:33 AM   #2
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on my stx prepped wrx on ra1's on teh track run -3.5F/-1/5R degrees camber. wear seems to be fine. hot pressure 42F/40R
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Old 09-27-2005, 10:48 AM   #3
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Are ra-1s legal for STX?
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Old 09-27-2005, 10:56 AM   #4
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Quote:
Originally Posted by waktasz
Are ra-1s legal for STX?
No, the treadwear rating is 40. STX tires must have a minimum tread wear rating of 140.
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Old 09-27-2005, 11:05 AM   #5
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i said my stx wrx ON THE TRACK... so he knows a baseline of my suspension setup. i only run these tires fro track days.
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Old 09-27-2005, 11:05 AM   #6
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That's what I thought. After re-reading his thread he uses his ra-1s for track not autox. I thought I was missing something.

Carry on.


edit: Post whore! You beat me to my correction.
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Old 09-27-2005, 11:06 AM   #7
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I would shoot for -3 F and -2 R to bring the tire wear more even, and you should find that 40-41 psi hot will work out for you in that case. More wouldn't hurt but these would be the minimum I would shoot for.

Also the rear spring rates are probably low relative to the front - 6k would probably be better for you (on track).
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Old 09-27-2005, 11:22 AM   #8
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-3 in front and -1 to -1.5 in back should be ideal.
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Old 09-27-2005, 11:34 AM   #9
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-3 on the front is pretty much accepted by all as the minimum even among differing setups. I think you will find that the rear is much more sensitive to your spring rate and sway bar rate, anything less than -2 on the rear of my old 04 would wear the outside faster on track - try different settings and get a probe thermocouple.
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Old 09-27-2005, 12:26 PM   #10
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I think I'll try the -3, -2 setup and possibly bump my rear bar up a notch and see how that helps.

http://forums.nasioc.com/forums/showthread.php?t=853250 - I am in the second picture on the first page, silver sti #115. If you look at the pic you can see how the rear camber has gone way positive.

Thanks for the input guys

-matt
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Old 09-27-2005, 01:31 PM   #11
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Looks like coming out of the apex at T3 (or you were way off the apex ) anyway that amount of dynamic camber there is not highly unusual given the changing camber nature around the apex (all on camber but decreasing as you move away from the apex) of the turn and before the course goes camber neutral over the crown. (Did you go on the track walk - if not do so some time you will be amazed how different the course appears on the ground.)

Additional rear static camber will help in this turn more than the ASB. Also only do one suspension change at a time and see how much each helps you.

Don't get overly hung up on how the car or wheels look in any given turn because they would look completely different on T9 for instance. The best way to guage your suspension tuning effects is lap times - they don't lie and let you know if the gross impact on each turn is netting to improvements. At SP though if you can carry more speed in T3, T4, T9 and T10 it will always compensate for any time lost in any other turn as a result of a suspension change.
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Old 09-27-2005, 03:16 PM   #12
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Good to know that the amount of dynamic camber change in the pic is not totally unusual.

In terms of lap times, etc., my car felt great this last weekend as it has for most of the season after of bit of changes to dampening and ride height, but I'm really just worried about my tire wear right now. My RA-1's have a lot of life left in them and I don't want to end up cording the outside shoulder and have to trash them.

I was not able to go on the track walk, but I did last year and it is pretty amazing to see how everything looks from the ground.
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Old 09-27-2005, 03:25 PM   #13
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41 psi front COLD and 37 psi rear COLD works for me with my set up. Just over -2 camber in front and -1.75 rear. Max stiffness on rear bar (24-26mm?) with solid end links and 22mm bar front, coil-overs, RA1s on SSR comps 17in.
I would try higher tire pressures, I use the above settings for all the tracks on the west coast. Starting point.
Good luck,
---4porsh--
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Old 09-27-2005, 04:09 PM   #14
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I've gathered that the target hot pressures are in the low-mid 40's. It seems like starting with those cold pressures they might get too high (I normally start with 36F 34R and get up to about 43F 41R.

Maybe I will try some higher pressures as well to see how that changes things.

-matt
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Old 09-28-2005, 09:40 AM   #15
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So here's another question. Would upgrading to stiffer bushings help prevent the suspension from extending under load and adding camber? If so, what bushings would be key?
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Old 09-28-2005, 06:59 PM   #16
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Matt,

You won't be able to get enough negative camber in the front given your spring rate and tires. Give her all she's got

We have the same problem over heating the outsides of our tires. Even with 12kg springs I still run -3.5 in the front on high grip street tires an even more with Hoosiers.

At my last event tire wear was decent but I really concentrated on steering angle and tried not to scrub the tires so much. With 500 hp you don't have to steer as much though

Phil
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Old 09-29-2005, 10:12 AM   #17
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Can you flip the RA1's- if you can save them now

In addition to camber increases, someone hinted at stiffer bushings- Grp N transverse link, lateral and trailing link bushings would help some as well (or maybe even spherical/pillowball ones).

From what I've read your tire pressures (hot) are pretty close (to comparable weight cars). If you could borrow a pyrometer from someone you'd have additional info to look at that might help "steer" you in the right direction.
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Old 09-29-2005, 02:34 PM   #18
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my track settings...
-2.75 front...1/4 toe out...
-1.6 rear..0 toe
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Old 09-29-2005, 11:15 PM   #19
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I ran into the same problem and for my next event (Road america october 15 can't wait) I want to add more camber with the camber plates and I'm wondering if anyone knew approximately how much toe i would get going from -1 degree rear camber to -2 degrees camber and going from -2 degrees in the front to -3 degrees.

Is this a good idea or do I need some smart strings to dial 0 toe back in. I'm want to do this because -2/-1 is about all i want to run on the street for tire wear.
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Old 09-29-2005, 11:18 PM   #20
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Quote:
Originally Posted by slickvic
I'm want to do this because -2/-1 is about all i want to run on the street for tire wear.
What tire wear issue would come up from -3/-2? I ran this year around with no tire wear problems as long as toe is zero it is not a problem. Camber is only a problem when toe is off.
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Old 09-30-2005, 12:43 AM   #21
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huge change in toe changing camber one degree ...



going from -2.5 to -3.5 will increase toe out a good 1/4 inch total.

btw. each 1/6th turn of one steer arm ... one facet ... is equal to about 1 mm.

1.6 mm = 1/16th inch
3.2 mm = 1/8th
6.4 mm = 1/4

Last edited by makofoto; 09-30-2005 at 01:44 AM.
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Old 09-30-2005, 01:41 AM   #22
slickvic
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Wow that is alot of toe change. Maybe I'll just run the -3/-2 setup as suggested, and see how the wear is.
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Old 09-30-2005, 01:51 AM   #23
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It's very easy to check and change toe ... two 2' straight boards leaned against the outside of your tires/wheels ... measure the difference between the front and back of the boards with a steel tape measure.

To change your toe ... your need two 19 mm (one could be an adjustable spanner) and one 13 mm open end wrenches. Mark the steering arm so you have a reference, loosen the locking collar on the steering arm, turn steering arm, one facet (out of 6 on the steering arm) = 1 mm toe change ... think in terms of "sucking in" the front of the wheel to reduce toe out, or pushing out the front of the wheel to gain toe out ... while looking at the threads to see whether they suck-in or push-out the wheel. Whatever you do on one side do exactly the same on the other side ... to keep your steering straight.

Alignment primer here: http://tinyurl.com/a5d6c
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Old 09-30-2005, 05:30 AM   #24
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try to get as much castor as you can as well
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Old 09-30-2005, 01:07 PM   #25
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Quote:
Originally Posted by makofoto
It's very easy to check and change toe ... two 2' straight boards leaned against the outside of your tires/wheels ... measure the difference between the front and back of the boards with a steel tape measure.

To change your toe ... your need two 19 mm (one could be an adjustable spanner) and one 13 mm open end wrenches. Mark the steering arm so you have a reference, loosen the locking collar on the steering arm, turn steering arm, one facet (out of 6 on the steering arm) = 1 mm toe change ... think in terms of "sucking in" the front of the wheel to reduce toe out, or pushing out the front of the wheel to gain toe out ... while looking at the threads to see whether they suck-in or push-out the wheel. Whatever you do on one side do exactly the same on the other side ... to keep your steering straight.

Alignment primer here: http://tinyurl.com/a5d6c
Yeah i know about this method but you still run into the problem of a thrust angle in the rear, this is why I will be using smart strings. Thanks for answering my question about toe change.
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