Wore my tires out.

[benebob]

Originally posted by Porter


Your statements and your attitude are both offensive. "Ricer go fast"? Give me a break. You obviously have me confused with my inferiors. I've never street raced in my life, nor would I associate with those who do. That entire culture is irritating and annoying in the extreme. My background is primarily in wrenching and tuning turbo Saabs and Subarus... sorry if that's not "elite" enough for your illustrious friend.

If you could explain properly why I and a master tech is wrong you wouldn't be so offended I'm sure but the ricer comment was all him. He thinks I'm a ricer too but then again your comments gave him quite a chuckle. What do you expect from a 55 year old Greek with a bad heart who hates anything that doesn't say made in Italy? Since I have explained the neg. aspects of high tire pressures and have no desire to offend you I think its lunchtime.

I know tires are highly subjective but I bough the RE950s over others recommendations and found them to be for the most part horrible in snow. I'll stick with the A540s until they die. Currently have nearly 25k on them and had no problems driving through a 2+ foot snow to get to the slopes. It definately kept the tranny cool though.

Perhaps our difference in tire pressures contributed to our radical difference in the experience of the tires' performance.

Here's a post from Luke, the head tire tech at Tirerack. He evaluates tires for a living.

Posted by Luke@tirerack on 04-11-2003 08:19 AM:
Load Capacity issues

Since this has been brought up many times and I was directed to a post in the Motorsports forum I thought I would repost my response here

So, let's look into the issue of shorter tires for AutoX ......

The Facts:

A P-Metric tires max load is achieved at 35 psi and a Euro metric tires max load is achieved at 36 psi adding more air pressure will not increase the tires load capacity but, lowering it will reduce the load carrying ablility. When increasing pressure all you are accomplishing is a lower rolling resistance, quicker steering response, stiffer ride and contact patch reduction.

Based on a WRX:
the OE tire is a 205/55-16 89V
max load capacity is 1279 lbs.
load capacity at recommended pressure (which we will call PLC for placard load capacity at 32psi) = 1213 lbs.

so the minimum load capacity for a WRX is 1213 lbs. according to the PLC

now if you look at the optional tire "OK'd" by Subaru
215/45-17 87W
max load is 1201
PLC = 1135

so in reality the minimum load capacity is 1135 lbs.

now lets consider the idea of running a capacity that is too low .... what happens:
the tire is put into a condition where it can support the car at a static rest point but, when driven aggressively the sidewalls are so over worked they can not properly control the contact patch of the tire allowing for excessive sidewall roll-over, irregular wear tread block and contact patch flex which robs the tires performance ability and grip. also the added flexing of the tire will increase the heat it generates which can make a tire feel really slippery .... better gear ratio is achieved but if you can't utilize the power it doesn't matter ....

A good way to understand this is: let's say I just put a 100lb. back pack on you .... you can stand there for quite a while (that's your car sitting in a parking lot) now go run up and down some stairs with that back pack .... that's normal driving and you can't do that very well, nearly as fast or for very long before your legs give out .... after you've recovered enough to walk (let the car rest once you arrive at the venue for your autoX), take a 500 meter sprint through deep sand, that's your autoX and you will most likely not make it to the finish without falling atleast once if you can finish at all.

there are possibilities for a shorter tire though

alternate tire sizes that would work on the WRX while maintaining load capacity (these may or may not be all of the sizes that could work and some of these may not even fit)

235/45-17/1135 PLC
225/45-17/1250 PLC
245/45-16/1235
215/45-16/1168 **** minimum 36 psi
195/55-16/1168
225/50-15/1246 PLC
215/50-15/1157 PLC
225/45-14/1168

all of these tires would be acceptable as long as at least 35 psi was run in them except where noted.

[svx_commuter]

Okay you guys, Play nice Some more help please. How important is the condition of the rubber at the ends of the springs? Mine is still original and looked okay when I did my struts.

Second, How about if I rotate these tires to the other side of the car? Then I can wear off a new inside tread on the tire.

Originally posted by svx_commuter
Okay you guys, Play nice Some more help please. How important is the condition of the rubber at the ends of the springs? Mine is still original and looked okay when I did my struts.

Second, How about if I rotate these tires to the other side of the car? Then I can wear off a new inside tread on the tire.

The rubber on the perches is there to prevent knocking or "groaning" of the spring when load changes, especially when you go over a crest and the suspension unloads. It's not really a load bearing item and won't affect ride quality unless it's not there... and then only in terms of noise.

Rotation... these are unidirectional tires? Rotating to the other side without unmounting the tires would cause your wheels to be backwards... If you're ok with remounting the tires then that's an idea... Make sure your tires are unidirectional though, and not asymmetrical. Asymmetricals have specific inner and outer tread.

[svx_commuter]

I would un-mount and remount to the other rims.
You said:
Make sure your tires are unidirectional though, and not asymmetrical. Asymmetricals have specific inner and outer tread.

So tires if directional and asymmetrical would be made left and right?

Asymmetricals will have a dedicated left and right side tire.

Directionals can be used on either side but have a dedicated rotation direction, which can normally be seen in the tread.

Some tires are both asymmetrical and directional, as some Pirellis.

[svx_commuter]

Oh take a simple question and turn it into a 3 page thread. I feel for the person that tries to follow this.

I pumped up my tires before I left for home, 37 psi rear and 34 psi front. When I got home they were at 40 front and 37 rear.

Okay Porter the car rides better with the higher pressure. It is even smoother on the highway bumps. I am really kicking myself now for wrecking these tires.

The front gross weight is 2405 lbs. Half for each tire is 1203 lbs. the tire is rated 1389 lbs at 44 psi. Heck even if I take 1/4 the cargo load off (685/4) 171 I get 1032 lbs per tire empty. The placard for these tire is wrong for sure. 33 psi is too low. The tire is stiffer in the bumps at 30 than it is at 37 psi.

[sfsvx]

Originally posted by Mr. Pockets
I'd be interested to see what tire pressure is stamped on the Japanese SVXs.

Check with Joe (svxistentialist). He's got a JDM SVX.

[svx_commuter]

Okay so I call Yokohama 800 number and ask. They say they go by the placard, 33 front and 28 rear. I get the following info for tire load:
1210 @ 28
1232 @ 29
1323 @ 33
1389 @ 36
1389 @ 44

Now what? I am
I am thinking I may be able to get replacement tires for free.

[kuoh]

After experiencing uneven wear with the original set of tires on my SVX, I've been running 35 all around ever since and have never had a problem with handling or abnormal wear even with extended use between rotations. I don't know about all the science, but at 180k miles and averaging 60k per set, I prefer to run this setup as opposed to what it says on the door jamb.

KuoH

[floatingkiwi]

According to the stamp on my door jam

Rear 2.0 kg/m2 (28.5psi)
Front 2.2 (or is it 2.3 - my car is in town today)kg/m2 (31.2-32.7psi)

I happen to believe that this is way too low, and in fact my mother's car (SVX) with I can't remember what tyres (but quite expensive) is having the same problem that SVX_commuter has i.e the inside inch or so is severly chewed out.

I run my SVX at about 35 f 32 r, simply because I have cheap Indonesian tyres and our NZ roads are so incredibly noisy that we can't run what we'd like to.

Matt

[mbtoloczko]

Originally posted by gl1674
....

Wear on the inside may also be a sign of wrong camber.
Apparently the factory service manual lists a different number
compared to what is in the electronic database in places like Big-O tires. Not a big deal, half a degree difference, but still.
I don't remember exactly, something like Big O says 0.5 degree, but factory manual says 0.1 degree...

Factory specs on SVX alignment are as follows:

front toe: nominal 0", allowable +/- 0.12"
front camber: nominal -0.4 deg, allowable +0.3 deg to -1.2 deg
front caster (factory non adjustable): nominal +4.8 deg, allowable +4.1 deg to +5.6 deg

rear toe: nominal 0", allowable +/- 0.12"
rear camber (factory non-adjustable): nominal -0.7 deg, allowable +0.1 deg to -1.4 deg

If you need to adjust the rear camber, there is a company that makes an eccentric bolt for the strut that adds the ability to adjust rear camber. The nominal values are a nice comprimise between performance and wear. If you take it in for alignment, don't try to get the shop to push the camber values to 0 deg.

Were the insides of both the front and rear tires worn out?

Wear was rate was certainly dramatically increased by the lack of tire rotation and low tire pressure. I doubt your struts are bad if you are on your 2nd set within 80k miles. Do they feel bad?

Running higher than stock tire pressure is a good thing. The stock pressures were derived to provide a comfortable ride. I don't run values as high as Jason does, but I definitely increase the pressures by 5 psi over the values on the door jam.

If you are running your tires in the 30-40 psi range, for the front and rear tires to have the same *rolling* radius, the front tires will need to have much more pressure than the rear tires. I verified this myself using whiteout to mark the tires and a straight piece of road. With my 225/45-17 tires, to get the same rolling radius in the front and rear, I had to run 38 psi in the front and 30 psi in the rear. With a 4 psi differential, there was a 0.12% difference in rolling radius. With equal psi, there was a 0.25% difference in rolling radius.

[immortal_suby]

I ran my avs sports at stock pressure for most of their life - tore the shoulders to pieces and recently replaced them with azenis when the cord was showing. Middle of the tire had alot of tread left - it was disappointing. I just swapped tires on my wife's svx last night - her avid V4's sidewalls were also chewed to the point where metal was showing in the shoulders. I put my used avs db's on and there is no way they are going to be set at stock pressure. She drives fast but not aggressively in corners.
On recommendation from mainly Porter and the other folks at i-club I'm running 45/ 43 and I love it on these new tires. I started a little lower and gradually went up some. Ride is not harsh and cornering feels great and I don't get the feeling I'm going to peel the tire off of the rim in a fast corner.

I may be a junior member, but I'm not junior when it comes to tires and what the door jam sticker says vs type of tire in use.
This applies to all vehicles, AWD or not.

My 93 SVX placard indicates that this specific vehicle was set-up to run P225/50 R16 (91V) tires, front 33, rear 29. I have Toyo Proxes FZ4 on the car at present and can tell a difference between these tires and the Michelins (same size) that were on the car when I purchased it. The Michelins provided a smoother ride with the same tire presssure.

Tire performance and ride characteristics boil down to one very specific aspect: tire construction. Different brands provide/present different ride characteristics. I prefer Michelins, because they deliver, in my opinion, better ride quality. But that characteristic comes with a higher price.

Side wall construction is the key to ride quality and overall tire performance. Some manufacturers build a better tire than others. Don't blame it on tire pressure.

The manufacturer's placard specifies tire size/pressure based on weight distribution/suspension design/load capacity.

I recently purchased two 2003 Chevy Suburbans. Both are 3/4 ton, 4WD vehicles. One is an LT, the other is an LS. One rides better than the other. Why? Different shocks on the LT. But the two vehicles have identical tire placard information. Both call for LT 245/75R16E tires with 50 PSI Front, 80 PSI rear. Both vehicles have identical tires and same psi. I guess Chevy thought that the LT should present more of a refined ride (leather and all that stuff) than the LS. It's not the tires my fellow forum members, it's the shocks.

Let's back off on this thread. Typically, specific tire wear patterns, such as cupping or feathering, is the result of worn suspension parts or improper alignment. Plain and simple. No personal thoughts, just facts.

If you wish to discuss tire performance, or lack thereof, then it's time for a new/different thread.