uwaeve

This is a long shot, and I'm not even sure I'll know how to use the information, but has anyone measured the camber curves for the stock suspension?

The reason I ask is that I will be trying my first set of RA1s soon. So far my street tires have worn pretty evenly across the tread. Since I'm assuming the RA1s will have the car developing more roll, I'm interested to see if the camber change from the increased travel will help keep the tire on the ground.

I know, the best way to measure this is to LOOK AT THE TIRES after a couple of track days. However, since I'm an analyst and need to know how everything works, I thought maybe someone had either measured this on an alignment rack or put the end locations and lengths of the suspension members into one of those whiz-bang software packages that will show you this junk.

Thanks in advance.

uwaeve
soon-to-be-tire-flipper

Kolia

iTrader: (2)

Pictures ?

dnguyent

iTrader: (5)

hmmm, how timely. I was just having some good email chats with a couple members regarding tire wear and alignment.

I've run Pirelli Corsas for the past 4 track days, and have what I consider unusual tire wear. The attached picture is from Geoff's car, but my wear is very similar. Wear is noticeably worse along the outer treadblocks, as you can see where the tire grooves vanish, and reappear near mold line.

My rear and front tires have similar wear pattern, but the front is worn out more at the shoulders. I run -2.8/-2.9 degrees of camber up front and -1.9/-2.0 rear. Toe is -1/16" (f) and +1/16" (r). Tire pressures set at 36 to 37 psi pit hot, but Pirelli recommends 28psi to 35psi hot. Temps across the tread were pretty even, though I question my measurements because the probe-type thermometer I use registers temps as slow as one of those digital thermometers that our moms put in our mouths when we have a fever.

Not surprinsingly, some say outside shoulders should wear faster while others say inside shoulders should wear faster. Perhaps I just need a proper suspension system (currently OE shocks w/Hotchkis TVS). The Hotchkis successfully mitigated the horrible freeway bounce, but it's a soft system.

As for the question by the OP, I'm not familiar w/camber curves. I'd like to know more if someone can explain it or post a link.

-don

Kolia

iTrader: (2)

Wow, that's some pretty localized tire wear!

All 4 tires are like that? I'll have to go out and that some pics of my RA1s.

The camber curve is a plot of the camber change that the wheel goes through as the suspension goes from full droop to full bump. Ideally, it should counter the car's body roll and maintain the tire flat.

In our cases, it might be desirable to have more dynamic camber in order to help the tire work against the force vectors. ie: so that the tire is still "flat" when taking lateral load.

edit: Are the Pirelly known to have stiff sidewalls ?

MoodDude

on that tire wear.
I run my camber -1.5 all the way around and my hot tire pressures at 38-39 front and 39-40 rear.
I am seeing very even wear on my track tires with this set up. That is including 7 hours of track time this weekend at Barber Motorsports and it was almost 100F air temp (I don't know what the track temps where although).

My guess would be that would be a tire problem, not the car?

C Ray Z

iTrader: (2)

I also run -3degree front and -2.5 rear on a very stiff T2 suspension. tires are V710 with 11 track days on them. I have about 2 more left but wear has been very even.

uwaeve

MoodDude,

what tires are you running? As I understand it the wear will be different on street tires vs. rcomps. I'm working with the factory alignment and my street tire wear on the track has been essentially even. I'm worried about what is going to happen once I step up to some rcomps.

mpowers

iTrader: (7)

I have the same pirellis that the wear pattern was the same way as yours, I'll have to take a pic but it was mostly the front. I memory serves me correctly they were 255/17, when I swapped back to the victoracer 275/17 the problem went away. I was disappointed to say the least on the quality of the tires. They over heated quickly and became very greasy. I'll post some pics of the pirelli's tonight.

amolaver

iTrader: (1)

no offense intended dnguyent, but that kind of tirewear can happen when the car is overdriven. you may want to try dropping your corner entry speeds, get the car turned in, and get on the power earlier. i'm not saying that's the issue, but i believe its a possibility.

how would you describe the car's handling with the alignment/setup you detailed earlier?

uwaeve - sorry, no help here for finding information on the camber curves. it would be interesting to see it, although i think even more useful to see it when overlaid with a couple of aftermarket a-arms. ie, does going to 350evo arms dramatically change the camber curve?

ahm

Eagle1

iTrader: (2)

It certainly looks like the car's inertial momentum is rolling over the tire wall. Inadequate tire pressure, too soft a front suspension and "push" understeer on corner entries could all be contributing factors. It would seem, and this is speculation, that no single factor is giving that result, but that you have a combination at work to deliver that extreme a result.

Certainly the easiest thing to do is to up the psi about 3 pounds. But I would definitely get more sway bar stiffness and adjust front camber to 3 degrees negative, perhaps even 3.5.

That the rears are getting the same tire wear pattern as the fronts is perplexing, because they should not be. If the fronts are pushing then the rears would not be scrubbing. Can you describe whether the car is understeering, oversteering at the limits? Have you had any changes to the suspension done, coilovers, lowering? It just seems too extreme. What is happening to your street tires?

MoodDude

I have Pilot Sport Cups, they are a DOT approved R-Compound tire. If you want pictures, let me know. I have about 12 hours of total track time on them, in the hot southern weather! They have a little less than 1/2 their original tread left.

uwaeve

No pictures necessary if you say they're wearing evenly. Thanks though. This kind of answers my question, which really should have been asked as:

Will the suspension sufficiently compensate for the extra body roll induced by using stickier tires?

Did you run them on the track at full-tread? I'm assuming so if you say you have 12 hours of track time on them and have only gone to half tread. What kind of feedback do you get from them (audio, too)? I'm thinking of my first set of Rcomps and have been told that the RA1 at full tread is somewhat forgiving, but haven't heard too much about the PSC regarding how it would fare as an "entry-level" R-compound. Thanks!

Fluid1

iTrader: (19)

Wow, that tire wear looks like autocross wear. Usually a sign that the car is being pushed too hard in the front half of turns.... however being that I have no experience with those specific tires and am unaware of their sidewall/treadwear, it's hard for me to go too far out on a limb.

dnguyent

iTrader: (5)

I was told by several different sources that these tires need to be run 28psi to 35psi hot or they'll get greasy quickly. The only reason why I was at 36 to 37 hot was because of the odd tire wear. I think I'll go down to 30-32 hot, and get a feel for it.

My lap times at Thill were better than I expected on a 105F day, near stock suspension, newbie on r-comps, and limited driving experience. The tires did get greasy, but I don't have a baseline to gauge from. From my lap times, I assume these tires are doing a decent job of keeping me planted despite the odd wear pattern.

All four are like that.
When I first bought these, I was amazed at how stiff the sidewalls were. I could barely bend them, while both street tires in my garage (T1S & SportContact II) were flimsy by a huge margin.

No offense taken. I did adjust my corner entry speeds based on the amount of judder I felt through the steering. If I overcook on entry, It literally feels like sh*t, and the rubber on the front tires will peel up across the midsection of the tread like planing wood against the grain. Also, my rears have the same wear pattern.

As for balance, driving with same sized tires all around is like finding a better drug! I finally know what Kolia has been talking about; Getting the car to go on a nice four-wheel drift. Sometimes, it's like f**ckin' ballet...

[QUOTE=Eagle1]
It certainly looks like the car's inertial momentum is rolling over the tire wall. Inadequate tire pressure, too soft a front suspension and "push" understeer ...Have you had any changes to the suspension done, coilovers, lowering? It just seems too extreme. What is happening to your street tires?

I don't have the same problem on street tires. My suspension is: stock shocks and Hotchkis springs/sway bars. The springs are nearly stock rates, 10% stiffer up front and 10% softer in the rear. The car is lowered about 3/4".

Well, I spent more time inspecting the tires last night because I got them off, and here's what I see. It appears that the grooves on the exterior shoulder are much shallower than the other sections of the tire. I'm wondering if Pirelli designs their Corsa tire to be slick along the shoulder block while maintining some tread at the middle and interior shoulder. Check out http://www.tirerack.com/tires/BigPic...el=PZero+Corsa

Does it look like there's much tread there to start with?
I guess I'll find out soon enough how much rubber is really there once I cord a set.

mpowers

iTrader: (7)

I still think its the tire, with 3.5 degrees of camber they should have never worn like this. I'll get the pics up tonight but they would pass as a double for your tires.

For what its worth, my set only had 1 track day on them at Roebling before I swap back to the victoracer.

uwaeve

That's interesting about those sipes being shallow, it looks like that from the new picture.

If you have a tread depth gauge I'd be interested to see what you have for tread left in the middle and at the inside of the tire. If you could get the manufacturer-molded tread depth for those deeper sipes, as well as the molded tread depth for the outside shoulder sipe, you should be able to tell if your tires are wearing evenly.

MoodDude

These are my first R-compound tires, so I can't give you a comparison. And none of my suspension is stock, so I don't know how they will do there either.
These tires started out life on my car un-shaved, so yes full-tread.
As for noise, they do give you a little warning, but I don't use it. I usually can't hear them since my helmet blocks a lot of noise, my exhaust is loud as hell, the rubber coming off the tire is hitting the car everywhere, and the other cars on track are loud as hell too! Plus, I use my hearing for the engine to listen to see if I need to shift since I like to keep my eyes up.
I use my butt/lower back and my feet/legs to see if the tires are going to break loose. I will say that since switch to a race seat, you have so much feedback from the car (it takes a while to get use to) that I even drove on the track in the rain, and could push the hell out of her and anytime I even started getting loose, I had time to react!

daveh

iTrader: (9)

I've never calculated the numbers but the Z has some steep camber curves and the rear is greater than the front. I've found that the car doesn't need the high amounts of negative camber found on others cars.
Running almost a full degree more camber up front than in the rear is optimal.

MoodDude

What are you running on Camber in front and rear? I was thinking about changing it to -2 degrees in front and -1 degree in rear. Yet, haven't had the time to change it yet.

daveh

iTrader: (9)

Best to test with a pyrometer. Your results may vary