Moparts

Tire wear, Additional camber, and tire pressures

Posted By: Uhcoog1

Tire wear, Additional camber, and tire pressures - 01/20/14 10:30 PM

I've been doing a little at home testing over the last couple days. Figured I'd get some input from those guys who have more experience tracking their cars.

This started when I pulled my tires to rotate them to get ready for next weekends HPDE, and I realized I had excessive wear on my front tires as a result of my outing at Texas World Speedway (Clockwise).

Alignment going in:
6.9* caster both sides, 1.2* camber both sides, .15 toe in.
32 psi cold on all 4 corners

Tires:
Michelin Pilot Super Sport 265/40/18 on all 4 corners

Picture of rears next to fronts:
Right Rear on left, Right Front on right (facing same direction):

Left front on left, left rear on right (facing opposite directions):


Measurements of tires:
LF: inside slats, inside line, 2nd line, 3rd line, outside line, outside slat
LF: .100, .209, .211, .217, .151, .00
LR: .121, .237, .261, .260, .209,.058
RF: .118, .211, .220, .206, .154, .029
RR: .108, .235, .259, .253, .210, .062

Next, I went to do some skidpad work and measure tire temps.

Outer / middle / inner:
Pre- skidpad, after driving 20-30 minutes.
fronts: left 113,120,109
right 103,106,102

5 skidpad turns rt at Horse Track parking lot:
LF:137,138,107 (35 psi 2 min aft, 33 psi before left house)
LR:99,104,103 (33 psi hot, 31 before?)

This morning I added AndyF's camber spacers, which added around 1.2-1.3* of camber to my set-up.

Back out on the skidpad:
5 turns at outlet mall parking lot:
117/115/100 LF 33 psi as tested. Baseline.
110/108/100 LF 30 psi. Tire rolling more than I'd like.
120/117/101 LF 26 psi. Tire rolled past wear arrow.
125/123/105 LF 37 psi, FAST. 3400 rpm vs just over 2000 at 26 psi. Stable, solid feel. More balanced.

I also marked the tires with chalk, though even 37 psi rolled the tires slightly past the tip of the arrow.
37 psi with chalk:

Picture of arrow before chalk (this was the LR tire that is now in the LF position.)


At this point, I'm going to run the car with the additional camber (so ~2.5* total camber now), and up the tire pressures to that Hotchkis used in the Hot Rod tire test article (38/34 cold). I'm also going to flip the rears (which were the fronts), so the heavy wear now sits inside. If the fronts wear the outside edges too fast on saturday, I might flip those as well.

I'm also considering really torquing down the front sway bar end links, to reduce the rubber deflection and reduce body roll.


I'll also measure tire temps and wear at the track on saturday and sunday.

Any experienced racers have thoughts on what caused my abnormal tire wear? A combination of too low pressure and not enough negative camber? Or?

And the skidpad test - the numbers make sense, but I thought the test was telling me to drop tire pressure, given the temps were not linear. Obviously not the case. Further, I expected my adjustments both to camber and psi to have more of an impact on tire temperatures (granted the increased camber did cut down the gap). I'm not sure more camber is the answer with 'street' tires. Thoughts?

Thanks!
Wade
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/20/14 10:33 PM

Best pic for evaluating tire to ground (camber mid-corner):

Posted By: 72Swinger

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 01:09 AM

Where I go to play is also like 80% right turns and this is one reason I think a non-directional tire may suit me best,like a Michelin, so I can swap sides in between sessions without worries. Its just a matter of getting every dollar of tire life out of the tire investment IMO. It looks like your wear has gotten out of hand in your case lol! A 3500+lb car is going to eat tires like Wheaties man.
Posted By: Dan@Hotchkis

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 05:37 AM

Great data. To make adjustments increase or decrease PSI to get temp even or the "slant of temp" even. As an example:
if you saw from inside to outside:

110/120/105

You have too much air in the tire.

A decrease in pressure by 2 psi would probably net you:

112/115/110

Further Decrease would get you to:

113/113/112

Which would be about on the money.

Lets say you see...

100/115/130

This would tell you the car is lacking camber and the outside of the tire needs to come in. A couple factors come in to see if you want to make the adjustment using static camber or caster.
Posted By: autoxcuda

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 06:06 AM

uhcoog1,

What are your front and rear spring-rates/spring-size.

What are your front and rear (if applic) sway bar sizes.
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 06:15 AM

Quote:

Great data. To make adjustments increase or decrease PSI to get temp even or the "slant of temp" even. As an example:
if you saw from inside to outside:

110/120/105

You have too much air in the tire.

A decrease in pressure by 2 psi would probably net you:

112/115/110

Further Decrease would get you to:

113/113/112

Which would be about on the money.

Lets say you see...

100/115/130

This would tell you the car is lacking camber and the outside of the tire needs to come in. A couple factors come in to see if you want to make the adjustment using static camber or caster.



Dan-

Thanks for the reply! I'm with you on interpreting the temp data, but the data didn't fall in line as expected with the changes I made. Dropping the pressure didn't align the temperature readings, and hurt the performance.

Adding camber helped, but didn't entirely solve the issue.

I'm thinking I'm losing effective camber in a corner due to body roll. The roll couple is close, but I don't think the front roll bar is coming into play early enough to combat the roll. Thoughts?

Quote:


A couple factors come in to see if you want to make the adjustment using static camber or caster.



I'd love to hear more on this...
Posted By: amxautox

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 06:18 AM

So what is the rim width on those wheels? Tire casing width?
Posted By: Dan@Hotchkis

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 06:20 AM

Quote:

Quote:

Great data. To make adjustments increase or decrease PSI to get temp even or the "slant of temp" even. As an example:
if you saw from inside to outside:

110/120/105

You have too much air in the tire.

A decrease in pressure by 2 psi would probably net you:

112/115/110

Further Decrease would get you to:

113/113/112

Which would be about on the money.

Lets say you see...

100/115/130

This would tell you the car is lacking camber and the outside of the tire needs to come in. A couple factors come in to see if you want to make the adjustment using static camber or caster.



Dan-

Thanks for the reply! I'm with you on interpreting the temp data, but the data didn't fall in line as expected with the changes I made. Dropping the pressure didn't align the temperature readings, and hurt the performance.

Adding camber helped, but didn't entirely solve the issue.

I'm thinking I'm losing effective camber in a corner due to body roll. The roll couple is close, but I don't think the front roll bar is coming into play early enough to combat the roll. Thoughts?

Quote:


A couple factors come in to see if you want to make the adjustment using static camber or caster.



I'd love to hear more on this...



I'm sure you would..there is a reason I get paid a lot of money to help people set up their cars for the track. And my cars are always on the podium

To be honest, I'd have to drive the car. Steve has a great suggestion on checking your roll rates. How is the steering (responsiveness/under/over) on the car?
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 07:02 AM

More info on the set-up:
1.04 Mopar Performance TB's up front (~225 lb wheel rate)
1 5/16 x.250 wall Hellwig custom front bar (~475 lb wheel rate - 73+ k member)
MP 0" oval leaf springs (listed as 130 lb, though someone measured at 180 lb - these are not wheel rates. Also required 1.5" drop spacer)
Hellwig solid 3/4 rear bar (notes say wheel rates of 71, 82, or 96 - don't remember if this is wheel rate or bar rate - would need to run the numbers again to verify - currently on softest setting)

wheels are 18x9.5, +45mm offset. Tire allows a 9-10.5 rim width, and tire measurements on tire rack uses a 9.5" rim. Section with 10.7, tread width 10.2.

weight bias = 54.8% front, 45.2% rear. 3620 w/o driver. Bias didn't change on scales when driver got in.

Mopar handling line (used as a guide, not the gospel):
55% front bias = 77% front roll couple
54.5% front bias = 78% front roll couple
54% front bias = 79% front roll couple
53.5% front bias = 80% front roll couple

My math says I'm currently at 80% roll couple (using 180 lb for leaf), and can get 79% and 78% with rear sway adjustments. My 'goal' when picking components was to have some adjustment in the range that the handling line says I need, given it's theory and not a hard rule.

Currently I've got a bit of understeer. Max registered on the skidpad was .98 (peak, not constant). On the track, I was able to run down a number of great handling cars in the corners, albeit this occurred in the 'green' run group.

I'll play around with the rear bar soon, just wanted to fix the front tire wear issue first. I've also made it a point to only change one thing at a time, so I know what does what.

Car is a little lazy getting into the corners. Takes a split second to 'set'. Course, my only point of reference is shifter karts, which require a hard set with the steering wheel, which my instructor was trying to break that habit of mine in the duster.

Quote:


I'm sure you would..there is a reason I get paid a lot of money to help people set up their cars for the track. And my cars are always on the podium




And deservedly so! I'd sure appreciate you pointing me in the right direction, though!

The camber resulting from caster was something I was looking at this weekend. How significant is this when tuning a road course car vs an autocross car?
Posted By: autoxcuda

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 07:07 AM

Bigger torsion bars.

And/Or stiffer slow speed shocks to slow down the rate of weight transfer. And/Or stiffer slow speed compression front shocks and stiffer setting slow speed rebound on rear shocks.

And/Or too aggressive driving line entering corners (too hot in). Driving instructor's input/feelings?
Posted By: Tomswheels

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 08:12 AM

I've run Super Sports on both my 3500lb 69 Barracuda and my 2013 3700lb Mustang GT and to be honest, I think your tire wear isn't really abnormal. When you track a heavy car on a 300 treadware street tire, with an alignment that is remotely streetable, the outside of the tire is going to wear faster. I've found the pressure sweet spot for my SuperSports to be 38/34 on a road course, and 32/30 on a shorter autocross track. I have since switched to Falken RT615Ks and found the sidewalls to be stiffer than the Michelins, and that has improved the vagueness on turn-in you described. The new Dunlop Z2 will be the next tire I try, particularly since you can dismount them and run them on the other side of the car to equalize wear....
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 04:01 PM

Quote:

Bigger torsion bars.

And/Or stiffer slow speed shocks to slow down the rate of weight transfer. And/Or stiffer slow speed compression front shocks and stiffer setting slow speed rebound on rear shocks.

And/Or too aggressive driving line entering corners (too hot in). Driving instructor's input/feelings?



I disagree with you on needing bigger torsion bars. I've got plenty of wheel rate between the TB's and sway bar, I just need that wheel rate to come in sooner. Solid end links, maybe?

That being said, larger TB's would be easier to align. Just if I make that move now, I'll upset the balance I have, and will need to replace a second component as well.

None of the 4 instructors that got in the car had any complaints about the handling of the car; quite the opposite- I think they were all impressed. My main instructor spent a good amount of time feeling the car out, including evaluating the suspension set up and response. His only complaint was the throttle engagement (too aggressive).

Quote:

I've run Super Sports on both my 3500lb 69 Barracuda and my 2013 3700lb Mustang GT and to be honest, I think your tire wear isn't really abnormal. When you track a heavy car on a 300 treadware street tire, with an alignment that is remotely streetable, the outside of the tire is going to wear faster. I've found the pressure sweet spot for my SuperSports to be 38/34 on a road course, and 32/30 on a shorter autocross track. I have since switched to Falken RT615Ks and found the sidewalls to be stiffer than the Michelins, and that has improved the vagueness on turn-in you described. The new Dunlop Z2 will be the next tire I try, particularly since you can dismount them and run them on the other side of the car to equalize wear....



Thanks for the heads up! I went ahead and flipped the more worn set and put them on the rear. Will probably give up some traction with the 'wrong' compound facing out, but my set up can stand to lose a little traction in the rear and still be fine.

38/34 for super sports- is that cold or hot?

Oh yeah- my tire guy agreed with you- didn't think the wear was that abnormal. Shoot, the inner to outer main tread wear was only 2/32 off (7/32 vs 5/32). He indicated wearing through the side block wasn't a concern to him.
Posted By: autoxcuda

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 06:55 PM

Quote:

Quote:

Bigger torsion bars.

And/Or stiffer slow speed shocks to slow down the rate of weight transfer. And/Or stiffer slow speed compression front shocks and stiffer setting slow speed rebound on rear shocks.

And/Or too aggressive driving line entering corners (too hot in). Driving instructor's input/feelings?



I disagree with you on needing bigger torsion bars. I've got plenty of wheel rate between the TB's and sway bar, I just need that wheel rate to come in sooner. Solid end links, maybe?

That being said, larger TB's would be easier to align. Just if I make that move now, I'll upset the balance I have, and will need to replace a second component as well.

None of the 4 instructors that got in the car had any complaints about the handling of the car; quite the opposite- I think they were all impressed. My main instructor spent a good amount of time feeling the car out, including evaluating the suspension set up and response. His only complaint was the throttle engagement (too aggressive).





Then if it's just sooner (time) try the end link deal. Stiffen shocks would be a time deal too.

Maybe I'm over fixating on that picture where the car is in a tight turn and looks like it's loosing camber.

You have an adjustable rear sway bar? Where are you with the setting now?
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 07:47 PM

Quote:

Quote:

Quote:

Bigger torsion bars.

And/Or stiffer slow speed shocks to slow down the rate of weight transfer. And/Or stiffer slow speed compression front shocks and stiffer setting slow speed rebound on rear shocks.

And/Or too aggressive driving line entering corners (too hot in). Driving instructor's input/feelings?



I disagree with you on needing bigger torsion bars. I've got plenty of wheel rate between the TB's and sway bar, I just need that wheel rate to come in sooner. Solid end links, maybe?

That being said, larger TB's would be easier to align. Just if I make that move now, I'll upset the balance I have, and will need to replace a second component as well.

None of the 4 instructors that got in the car had any complaints about the handling of the car; quite the opposite- I think they were all impressed. My main instructor spent a good amount of time feeling the car out, including evaluating the suspension set up and response. His only complaint was the throttle engagement (too aggressive).





Then if it's just sooner (time) try the end link deal. Stiffen shocks would be a time deal too.

Maybe I'm over fixating on that picture where the car is in a tight turn and looks like it's loosing camber.

You have an adjustable rear sway bar? Where are you with the setting now?



I agree- I'm losing camber. I think it can be 'fixed' with the components I have now, though. If I can't improve the tire wear after a few sets of tires, then I'll start looking into new components.

I've got Bilstein RCD's in the car right now. Don't think I had that listed above.

Rear bar is set at the weakest setting.
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/21/14 08:18 PM

Good talking to you just now Dan. Thanks for taking the time!

wade
Posted By: Dan@Hotchkis

Re: Tire wear, Additional camber, and tire pressures - 01/22/14 01:53 AM

Quote:

Good talking to you just now Dan. Thanks for taking the time!

wade



My pleasure!
Posted By: Tomswheels

Re: Tire wear, Additional camber, and tire pressures - 01/22/14 06:40 AM


Quote:


Thanks for the heads up! I went ahead and flipped the more worn set and put them on the rear. Will probably give up some traction with the 'wrong' compound facing out, but my set up can stand to lose a little traction in the rear and still be fine.

38/34 for super sports- is that cold or hot?

Oh yeah- my tire guy agreed with you- didn't think the wear was that abnormal. Shoot, the inner to outer main tread wear was only 2/32 off (7/32 vs 5/32). He indicated wearing through the side block wasn't a concern to him.



That's my cold pressure. As your tires wear, you should notice they don't wear out quite as quickly, the tread blocks are more stable with less than 1/2 instead of full tread...
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/23/14 06:59 PM

Quote:




That's my cold pressure. As your tires wear, you should notice they don't wear out quite as quickly, the tread blocks are more stable with less than 1/2 instead of full tread...



That's good to know!


Also, for those of you following the thread, I was able to reduce the body roll significantly today. Put these in:

MasterPro K750074 - $28 each at Oreilly. That's also the Moog PN
-5.3" mounting point to mounting point (longer than factory?)

This is a 'must do' modification in my book. $60 cheap.





I don't have definitive test data on tire temps with this modification yet (started to rain this morning), but I can say the 'feel' was much improved. better turn in response, and much less body roll. It didn't change the roll couple, as the car is still close to balanced. It pushed slightly on the skidpad and kicked the rear out on a damp turn a few minutes later.

We've got bad weather the next two days, so I won't run the car until the event this weekend. I'll report back and include pictures and video.
Posted By: Rapom65

Re: Tire wear, Additional camber, and tire pressures - 01/24/14 12:32 AM

Wade, glad to hear you have had some initial positive results with the solid end links. I almost pulled the trigger on a set of those last night but was not having much luck finding info on lengths and stud sizes on the different truck applications listed in this and the other thread. Questions: I assume you were running stock type links with poly bushings before? Are the solid end link studs the correct size for the LCA and sway bar mounts? I measured my poly end links to be right at 4" (LCA tab to sway bar,'74 Duster, Helwig bar and end links) From your pictures your bar appears to be fairly level but at 5.5" mine would be angled down quite a bit more, thoughts?
Posted By: Dan@Hotchkis

Re: Tire wear, Additional camber, and tire pressures - 01/24/14 03:43 AM

Quote:


MasterPro K750074 - $28 each at Oreilly. That's also the Moog PN
-5.3" mounting point to mounting point (longer than factory?)

This is a 'must do' modification in my book. $60 cheap.





Very nice!
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/24/14 05:01 AM

Quote:

Wade, glad to hear you have had some initial positive results with the solid end links. I almost pulled the trigger on a set of those last night but was not having much luck finding info on lengths and stud sizes on the different truck applications listed in this and the other thread. Questions: I assume you were running stock type links with poly bushings before? Are the solid end link studs the correct size for the LCA and sway bar mounts? I measured my poly end links to be right at 4" (LCA tab to sway bar,'74 Duster, Helwig bar and end links) From your pictures your bar appears to be fairly level but at 5.5" mine would be angled down quite a bit more, thoughts?



5.3" mount to mount
Center piece is about 1.7"
'studs' are smaller, but work ok. I was concerned the 'shoulder' would be smaller than the holes, but it worked out ok (just big enough).

Mine is a Hellwig custom bar. Big fan of Dave at Hellwig. My measurement was exactly 4" as well prior to swap (same hardware as you on end links).

I actually have spacers under the bushings that move the center down 3/4" or so. Probably helps with the angle. Also, my ride height is pretty low. Say, 1"-1.5" from metal to metal at bump stop location.

If there was an option that was 1-1.5" shorter it would be perfect. Worst case scenario, you buy a set and return them. Or cut it down and reweld the link after removing 1".
Posted By: TC@HP2

Re: Tire wear, Additional camber, and tire pressures - 01/30/14 07:16 PM

Looking at your pictures, you still have a fair amount of body roll. This allows a couple of different approaches to improve.

The most direct improvement would be to shorten the upper control arm to allow more dynamic camber to come in with the roll. This is tough to do with the OEM control arms but could be accomplished with a more adjustable unit like SPC.

Another approach would be to step up t-bar or s-bar rates to reduce roll. This would be effective as well, but will require an adjustment to all four corners to restore the desired roll couple you have now. You know the math to this, so it certainly is possible, its just a matter of ride preference.
Posted By: 72Swinger

Re: Tire wear, Additional camber, and tire pressures - 01/30/14 07:23 PM

Quote:

Quote:

Wade, glad to hear you have had some initial positive results with the solid end links. I almost pulled the trigger on a set of those last night but was not having much luck finding info on lengths and stud sizes on the different truck applications listed in this and the other thread. Questions: I assume you were running stock type links with poly bushings before? Are the solid end link studs the correct size for the LCA and sway bar mounts? I measured my poly end links to be right at 4" (LCA tab to sway bar,'74 Duster, Helwig bar and end links) From your pictures your bar appears to be fairly level but at 5.5" mine would be angled down quite a bit more, thoughts?



5.3" mount to mount
Center piece is about 1.7"
'studs' are smaller, but work ok. I was concerned the 'shoulder' would be smaller than the holes, but it worked out ok (just big enough).

Mine is a Hellwig custom bar. Big fan of Dave at Hellwig. My measurement was exactly 4" as well prior to swap (same hardware as you on end links).

I actually have spacers under the bushings that move the center down 3/4" or so. Probably helps with the angle. Also, my ride height is pretty low. Say, 1"-1.5" from metal to metal at bump stop location.

If there was an option that was 1-1.5" shorter it would be perfect. Worst case scenario, you buy a set and return them. Or cut it down and reweld the link after removing 1".

I have one coming that I will shorten and hope it doesn't have plastic internals.
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/30/14 09:58 PM

Quote:

Looking at your pictures, you still have a fair amount of body roll. This allows a couple of different approaches to improve.

The most direct improvement would be to shorten the upper control arm to allow more dynamic camber to come in with the roll. This is tough to do with the OEM control arms but could be accomplished with a more adjustable unit like SPC.

Another approach would be to step up t-bar or s-bar rates to reduce roll. This would be effective as well, but will require an adjustment to all four corners to restore the desired roll couple you have now. You know the math to this, so it certainly is possible, its just a matter of ride preference.



Thanks for the input Tony!

I think I'm going to exhaust all my options with my current components before I start playing with adding roll resistance up front.


Gameplan:
-Check alignment and look at components (since I went off track in the last session - and my left front tire is squealing when it goes over tar on the road right now)
-Change front tires to a single compound tire - go to skidpad and check tire temps
-Adjust rear bar to stiffer setting - go to skidpad and check tire temps
-If car isn't oversteering with rear bar adjustment, add weight to rear of car until it does. Go to skidpad and check tire temps
-If tire temps aren't in an acceptable range, Adjust front suspension cam bolts for max camber with spacers (looking for 4*). Go to skidpad and check tire temps with car at a 'neutral' setting based on previous data.


If all else fails, then yes, time for some bigger TB's and a bigger rear sway bar to match.

The thing that gets me is the car flat out runs. It's already turned better lap times than I thought possible, and my driving is still a ways from where it needs to be.
Posted By: Consulier

Re: Tire wear, Additional camber, and tire pressures - 01/30/14 10:08 PM

Couple things I learned at the tire test...

1) That little arrow doesn't mean a damn thing. Has some other meaning that I can't remember, but not what we all think it means.

2) I've been close, but need to run a couple more pounds than I have ever run because I let the tires roll too much.

There is a separation line that you can just barely see in this photo, just above where that arrow would be pointing. But probably 1/4", or so, higher than the tip of the arrow... Hot Rod - Michelin Pic

That's all the further the tire should roll. That's the separation line from where the contact rubber is bonded to the sidewall rubber. Past that and you are into less sticky material.

Basically I have been running to about the arrow like you... forever. I've never taken temps, but by your temps, it looks like if you raise the pressure a couple pounds you will probably get the tire over where it should be.
Posted By: 72Swinger

Re: Tire wear, Additional camber, and tire pressures - 01/30/14 10:16 PM

Plus the tires you're using are not THAT great spec wise from what ive noticed.
What T-bars do you have now Wade?
Posted By: Supercuda

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 12:34 AM

Quote:

Looking at your pictures, you still have a fair amount of body roll. This allows a couple of different approaches to improve.

The most direct improvement would be to shorten the upper control arm to allow more dynamic camber to come in with the roll. This is tough to do with the OEM control arms but could be accomplished with a more adjustable unit like SPC.



I must be missing something but unless you relocate the inner pivot to account for a shorter UCA you will increase the static camber as well, not sure that's a good idea.
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 12:58 AM




Couple things I learned at the tire test...

1) That little arrow doesn't mean a damn thing. Has some other meaning that I can't remember, but not what we all think it means.

2) I've been close, but need to run a couple more pounds than I have ever run because I let the tires roll too much.

There is a separation line that you can just barely see in this photo, just above where that arrow would be pointing. But probably 1/4", or so, higher than the tip of the arrow... Hot Rod - Michelin Pic

That's all the further the tire should roll. That's the separation line from where the contact rubber is bonded to the sidewall rubber. Past that and you are into less sticky material.

Basically I have been running to about the arrow like you... forever. I've never taken temps, but by your temps, it looks like if you raise the pressure a couple pounds you will probably get the tire over where it should be.




I've got the fronts at 38 PSI, though I started at 32. I'll try higher and report back. Thanks for the tips.

Quote:

Plus the tires you're using are not THAT great spec wise from what ive noticed.
What T-bars do you have now Wade?



MP 1.04's

LOL - I think this is a great tire. It may not be the 'top dog' on the hot rod tire test, but it's won a number of other tire tests. It gives great feedback and performs well when wet.

That said, my next set of tires will be cheaper. The HPDE event manager recommended the HTR Z III, so I'll probably run through a set of those next.

I want more track time, so cheaper tires will help that happen.
Posted By: 72Swinger

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 01:39 AM

I saw a guy on LXForums with a 300 SRT8 wear out a pair of fronts in ONE track day. That and the pics of yours kinda tells me they at least dont like heavy cars.
Posted By: Trojmn

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 02:10 AM

Maybe i missed it, but I thought it was conspicuous that the pressures didn't vary from one brand to another in the Hot Rod tire test.
Posted By: Tomswheels

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 06:37 AM

Oh no, no, no on the HTR Z, I don't care how cheap they are... The Michelin Pilot Super Sport is not the absolute best tire for what you are doing, but it's easily top 10 in the 140 and higher Treadwear class. It is an extremely consistent tire. The ONLY other tires you should consider are: Nitto NT-01, Toyo R888, Dunlop Z1/Z2, Falken RT615K, Hankook RS3, and BFG Rival. I would rank your SuperSports 7th or 8th behind those for outright performance/hot dry lap times. Slightly behind those tires and your SuperSports would be the Yokohama Ad08, Kumho Ecsta XS, and maybe the Bridgestone RE11. That's it! Don't consider any other 140 + up Treadwear tires for the type of tracking you are doing!

Oh and I agree completely that different tires need different pressures!
Posted By: Trojmn

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 07:29 AM

once i found the vid of the taxicab dodging cones and i was up till 2AM watching old cars turn. also found some goodguys videos and hotchkis cars. It really kicked me into gear to get my A-body on the autox.

In other news the inter-webs a buz with a updated RS3 coming soon, which im a big fan of the current model for value and performance.
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 03:21 PM

Quote:

Oh no, no, no on the HTR Z, I don't care how cheap they are... The Michelin Pilot Super Sport is not the absolute best tire for what you are doing, but it's easily top 10 in the 140 and higher Treadwear class. It is an extremely consistent tire. The ONLY other tires you should consider are: Nitto NT-01, Toyo R888, Dunlop Z1/Z2, Falken RT615K, Hankook RS3, and BFG Rival. I would rank your SuperSports 7th or 8th behind those for outright performance/hot dry lap times. Slightly behind those tires and your SuperSports would be the Yokohama Ad08, Kumho Ecsta XS, and maybe the Bridgestone RE11. That's it! Don't consider any other 140 + up Treadwear tires for the type of tracking you are doing!

Oh and I agree completely that different tires need different pressures!



The price difference will 'buy' me two more track weekends. I say that's worth it. I guarantee I'll be faster on a lesser tire after the additional sixteen 20 minute sessions.

Not to mention, the 'test data' is pretty favorable for that tire. Not top 10, but probably top 20.
http://www.autocross.us/forums/topic/5084-hottest-autocross-tires-for-2011/


Unless of course somebody here is a tire rep and wants to sponsor me and send me free tires or sell me tires at cost... Any takers? Ha
Posted By: Consulier

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 05:02 PM

Quote:

Maybe i missed it, but I thought it was conspicuous that the pressures didn't vary from one brand to another in the Hot Rod tire test.


They did during testing, but you didn't get to see all the details. There was a little sidebar in the article (I think) about tire temps. We ran the Rival at varying temps and collected results to show what happens when you don't run enough, or run too much.

The tires really shouldn't run at drastically different pressures. A couple pounds here or there and that's it. They are all the same basic construction. Not like there was a bias ply in the group.
Posted By: Consulier

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 05:03 PM

Quote:

I saw a guy on LXForums with a 300 SRT8 wear out a pair of fronts in ONE track day. That and the pics of yours kinda tells me they at least dont like heavy cars.


LX/LC will destroy a set of tires in a day because they don't have any camber. The cars needs a ton and unless you bring it, the tires will essentially self destruct.
Posted By: 72Swinger

Re: Tire wear, Additional camber, and tire pressures - 01/31/14 06:10 PM

I agree, this car did have like 3* negative. Car was a setup car, if you want I can dig it up Wade and post a link.Edit: Here is the thread
http://www.lxforums.com/board/showthread.php/331958-NR-s-Winter-Build-For-Summer-Road-Racing/page3
Posted By: Tomswheels

Re: Tire wear, Additional camber, and tire pressures - 02/01/14 08:03 AM

Did you even read this? : "Sumitomo HTR ZIII Not an autocross tire, but pretty close to it. Good wet and dry. And dirt cheap. I’d recommend this as a daily driver to anyone who wants good fast street tires, but isn’t actually going to race on them".

Prepare to be disappointed.
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 02/01/14 09:54 AM

Quote:

Did you even read this?



I read it all.

I'm expecting 'lesser' performance. I don't need the best of the best to improve my driving.
Posted By: Trojmn

Re: Tire wear, Additional camber, and tire pressures - 02/01/14 10:33 AM

im not sure if your tire wear issue is normal for a track day. is it? But, it is generally true that better tires take abuse better at autox. you may find better tires to be more heat tolerant and therefore could wear longer because they don't turn into erasers. at 135F an RS3 is just getting tacky, but can be slick <60F. the kumho XS is another higher heat tire.

have you been able to take temps at the end of your driving session?
Posted By: Uhcoog1

Re: Tire wear, Additional camber, and tire pressures - 02/01/14 04:50 PM

Quote:

im not sure if your tire wear issue is normal for a track day. is it? But, it is generally true that better tires take abuse better at autox. you may find better tires to be more heat tolerant and therefore could wear longer because they don't turn into erasers. at 135F an RS3 is just getting tacky, but can be slick <60F. the kumho XS is another higher heat tire.

have you been able to take temps at the end of your driving session?



I have not yet taken temps while on track. Maybe next time.
Posted By: TC@HP2

Re: Tire wear, Additional camber, and tire pressures - 02/02/14 08:24 PM

Quote:

Quote:

Looking at your pictures, you still have a fair amount of body roll. This allows a couple of different approaches to improve.

The most direct improvement would be to shorten the upper control arm to allow more dynamic camber to come in with the roll. This is tough to do with the OEM control arms but could be accomplished with a more adjustable unit like SPC.



I must be missing something but unless you relocate the inner pivot to account for a shorter UCA you will increase the static camber as well, not sure that's a good idea.



It is the most direct way to address camber gain, but certainly not the easiest because, as you point out, you need to relocate inner pivot points. The only way I see to address this with the stock pick up points is to use SPC control arms. This would allow you to rotate the eccentrics to a full out position to reduce the effective length of the arm, then you use the double adjustable feature of the SPC arms to dial in caster and camber.

Because of this, there is no way any fixed length tubular control arm could do the same thing. It also means that once you use up the additional half inch of range from the eccentrics, that is all you get. If you needed further length reductions, its time to whip out the plasma and mig welder.

Before I'd jump into either of these solutions, I'd certainly put the effort into analysing the camber gain currently and required to see if it would get the results desired.
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