Tire width or compound? (NOT a "which tire should I buy thread)

[az3579]

While perusing summer tires that I'm in dire need of with summer just around the corner, I started thinking. Since I'm looking for tires that are at the top end of the performance category that will see both track time AND lots of daily driving, I started to think where the compromise needs to come from. There is no way I can afford what I really want, so something's got to give.

Ideally what I want is 255/35R-18 Michelin Pilot Super Sports all around. That ain't gonna happen, at $235 each for a total of $940 for a set not even including mounting.

So, here is what I was thinking.

In the size I want (255's all around), the Bridgestone Potenza S-04 Pole Position tires are significantly cheaper at $656 for a set and seem to fall into second place in most of the tests when compared to the Michelin PSS tires. To me, this is far greater value, and would be OK with buying these as the performance of them is most definitely close. But, this leads me to the important question.

What is more important: tire width or the compound?
For a heavy car like the E46, I would think both are equally important, but need to hear this from those with experience. I've always bought cheaper tires, so the PSS would in theory be way over my usual price range, so I've never actually taken such an advanced compound to the limit before (with the exception of some Hoosier A6's in autox on a RX8 a couple of times). I don't know what makes a bigger difference; the amount of tire tread you have on the road or compound.

Having the answer to this question will allow me to make the choice between slightly narrower Michelin PSS tires (easing the cost pain) or full width Pole Positions.
Anyone with experience with track and autox care to chime in?

[M0nk3y]

I realize the criteria you have above...but any thoughts on Dunlop ZIIs, Hankook RS3s, BFG Rivals or Yokohama AD08R?

You're going to compromise a bit on road noise...but other than that the tires are considerably cheaper, and are much, much, much better for a performance oriented aspect.


To answer the question at hand, tire compound is where you want to be. PSS tires on HPDE courses like to chew apart (multiple threads on 1addicts showing that the tread literally falling off the tire). You need a compound that can tolerate hot temperatures without having any ill effect. Heat cycling is indeed a issue and tires more oriented towards autox/track can handle this. But as you run a tire....heat them up to operating temperature and then cool the tire down, the rubber likes to harden. The more you do this, and a tire can/will lose its grip overtime. Now this isn't something you'll see after 2 events. My Hankook RS3s lasted 2 years (approx 20-25 autox and 3 track days) before I could notice an issue with grip.

However, a tire like PSS...can it tolerate these multiple heat cycles? Who knows....I certainly don't.

Alone with a tire compound, comes sidewall strength. Hankook RS3s have a really soft sidewall and need a ton of slip angle to get full grip. Dunlop ZIIs however are very stiff on the sidewall, and thus are much more responsive on initial turn in. However on the other side...if you overdrive the Hankooks they recover fairly easily...if you do the same on the Dunlops you'll lose all grip.

It is a game, what are you willing to sacrifice and what you need.

To just touch on the width...in SCCA Solo II, specifically STX, max tire width is 265. The car that won this year ran on 235 squared. He could have easily fit 265s, but he didn't.

Make any sense?

[slater]

great thread!

i have PSS experience on a DD/twisty carver, and they are 'all that' for that application. i never got race track heat into mine, but for street use they do everything well. plus, they are light - and we all know what less unsprung weight does.

given your budget - and yes, $940 for a set of tires is expensive for lots of people - one tire you might want to check out, that i might check out this year too, is the bfgoodrich g-force sport comp-2's... they are $650 after rebate from tirerack in 255/35/18, $535 in 245/40/18 and $475 in 235/40/18. the reviews are good, the test results are good, the survey results are good. they are quite 'square' in profile so you might want to step down from a 255 in them.

peter

[ZHPRegistry.net]

Unless you are comparing the worst vs the best compounds, I am going to say that width has most effect on lateral grip (rolling resistance). But keep in mind that width starts working against you in straight lines. Also on a given rim, the wider the tire, the more it flexes which in turn has effect on handling. What's your goal at the track? times? car control?

[LivesNearCostco]

I'll go with Monkey and say that tire compound is more important up to a point. PSS vs. Bridgestone S04 is maybe worth 10-20mm? That is a 235mm PSS might grip as well as a 245 or 255 S-04. (I have staggered PSS now, never had Bridgestone S-04.) Certainly my Continental ExtremeDW 245mm tires gripped a lot better than my 255mm Bridgestone RE-760 tires, though the ExtremeDW is probably not as good as the PSS in the dry and the RE-760 is not as good as the Bridgestone S-04.

My 235mm Conti race slick takeoffs--reputed to be similar to Hoosier R6--grip a lot better than the 245mm ExtremDW and probably a little better than the 255mm Hankook R-S3 tires, but it's hard for me to remember because I had the R-S3 tires around 2011-2012 and didn't get the Conti race takeoffs until September 2013, and I drove those tires on different tracks using different suspensions. To complicate things, the 235mm Contis are probably really 245mm width and they supposedly lose grip quickly after a few track days, and I bought them used.

[az3579]

Great responses, thanks guys. Perhaps some key points should be thrown in here as far as how the tires will be used.

First and foremost, my tire selection options were based purely on "test results" from Tire Rack and a few other car magazines that tested these tires. With that said, I'm not sure how their reviews would reflect on the actual usage I will put these tires through. They do test the things that matter for a daily driven tire, which is partially why I chose these two (they top the charts) and they do some autox and wet course testing as well. With all this said, I have no idea how these will fair to extended sessions on the track, which is the harshest usage the tires will receive from me (4x 20-minute sessions at Lime Rock Park and Watkins Glen).

These tires will be used on the street for daily duties about 75% of the time, so tire width for this use doesn't matter. 5% will be for autox and 20% will be track usage, so there will be considerable performance driving involved. These percentages are based on miles driven. When on the street, I am pretty mild when I drive; I used to take corners at full speed all the time but I've mellowed down so I'd say I'd be driving on them on a scale of mild (most of the time) to moderate (occasionally). For the street, the level of grip doesn't matter much, though I do take lots of value out of a tire that will play the part when it comes to emergency maneuvers, which I have to do on a very regular basis (mostly potholes but truckers who like to cut me off while halfway done passing them is becoming more common). I do want them to be quiet. A little bit of noise is ok as long as it's not unbearable like my Hankook V12's were. Noise isn't a big priority but is a biiiig plus. Tread life will be the most important factor for me. I will not be able to justify spending extra for tires if they wear out before the season is through. If I can make it through this track season (3 track days this year), autox season (two events per month until October), and daily driving (probably about 15-20k of daily duties) on these tires then I'll be happy. I do want good wet performance because autox and track days run rain or shine.

Requirements summary, in order of importance: All around performance in wet and dry, tread wear, price, noise, comfort.

Kyle,
I can't use the other tires you mentioned because they fail in one or more categories that are "musts" for me (according to these tests, of course). This is even before you take into consideration their resistance to heat cycling. Because these aren't R-compound tires, heat cycling isn't as much of an issue, though is something to keep in mind as it's still affected to some degree. Please PM your thoughts on viable options as I don't intend to turn this into a "which tire to choose" thread. The info above is purely for reference since you mentioned tire choices.



Regarding what is more important, so far I'm getting conflicting answers about compound vs width, based on research online. Does anyone know of some hard data that exists that answers the question? I'm torn because the E46 is a heavy car. If it was lightweight, I could probably get away with thinner tires and stickier rubber.
So far it looks like it's leaning towards compound instead of width...



BTW, if anyone has any suggestions for the right kind of tire (if one jumps out at you) then feel free to PM me! There could be others there that I'm not even thinking about that would fit the bill.

[az3579]

So it looks like I don't have as much of a dilemma anymore after all. I completely forgot about my spare set of track wheels in my garage, which has Bridgestone RE-11's mounted with some life left. I guess all I have to do is buy a daily set. Yay.


The original question still stands of course. lol
I did a little more digging and found that the compound makes a huge difference because of the way it reacts with the road. If you really think about it, the tire width of a 235 vs a 255 really isn't all that much because the amount of tire actually contacting the road isn't all that much to begin with. So, with a compound that bites harder, I would think that would have more of a tendency to draw the car into the corner more than more area.

I can only relate this to bowling; the ball's coverstock is more important than it's weight (compound more important than width). Ideally you want the heaviest ball you can get (16lb, or a 255 width tire in this comparison), but the coverstock (compound in the tire's case) is what determines the performance of the ball (tire). Is this the case?

Perhaps I'm answering my own question. :dunno

[derbo]

BP,

I do not have personally experience with PSS but my friend who tracks his E39 540i used to use them. The brand new tires that were mounted the week before would rip chunks off during the morning sessions and barely last the whole day. The compound in the PSS is fantastic via daily driving and some spirited driving but I believe the compound is not capable to keep up with the heat generated with our heavier cars.

I personally believe compound is a bigger importance than tread width if you are comparing 235 vs 255. The 20mm is just a sectional width and the extreme performance tires like the Starspec and RE11s do have a more "square" tire shape. The Dunlop Star Spec in 245mm is more like a 255mm sport tire.

Unfortunately it seems treadwear and rain/wet is more of a priority than trackday performance. I personally think the PSS, S04 or DW would be the tire for you if you didn't find your track tires. RE11, StarSpecs, RS3 are wonderful in the dry but are terrible in the wet when compared to PSS and S04s.


I'm planning to pick the Continental DWs as my stock zhp wheel's next tires as they will be similar to the PSS without the major cost.

[az3579]

It's interesting that you say that about the PSS, Derek. BMW chooses Pilot Super Sport tires for their M cars, which they test rigorously at the Nürburgring. They specifically choose this tire because it passes all of their tests. If it started chunking off tread blocks for your friend, it makes me wonder why BMW didn't have an issue with this. Did your friend properly break in the tires before pushing them to the limit? I believe most tires have like a 500 mile break-in period before they start performing at their best. If you don't break it in properly, it could cause premature wear from what I understand.

The tires on my 17" track wheels are 255-width Potenza RE-11's. Those aren't bad in the rain from when I pushed them in autox but then again, I had nothing to compare them to other than my crappy all-seasons at the time. They are 255 all around but could sense more understeer in the wet than in the dry.

Regardless, being able to step down a size is helpful now because this reduces the cost, in some cases quite dramatically.

Thanks for the insight!

[derbo]

BP,

One thing I may note is that he may have pushed the limit of the tires and overdriven the tire to cause it to chunk. It may be his driving style that cause the tires to excessively chunk. He bought the PSS when they were first introduced in 2011 and there were barely any real information on them except they were a bi-compound tire with a harder compound in the middle and a softer compound on the outer edge. I believe he was driving it like it was a Bridgestone RE11 and that may have cause the tires to reach it's limit far faster than it was capable of handling.

As for rain,
I've tried my 255/35/18 RE11s, 245/40/17 StarSpec1s in the rain and its definitely not bad in regular rain. However if there is a lot of standing water, I would be more concern with it. The treadwear 200 tires are definitely aren't extremely terrible in the rain, just not as great as some regular summer tires. If I ever switch to R compounds in competitive racing, I'm sure the RE11 or Starspecs would be my intermediate tires. :)

Personally I would try the PSS even at the cost. It comes with a 6yr 30k warranty if it is same tire size all around. I definitely expect the PSS to outperform the S04 and DW on the track. Since my usual cost for tires is roughly $1200 for the RE11 on the 18s, $900 non-mounted isn't too bad. :)

[Hornung418]

I've got 235 Kumho XS mounted on 8.5s. Killer in the dry. Tragic in the wet.

Sent from my GS3.

[M0nk3y]

BP,

One thing I may note is that he may have pushed the limit of the tires and overdriven the tire to cause it to chunk. It may be his driving style that cause the tires to excessively chunk. He bought the PSS when they were first introduced in 2011 and there were barely any real information on them except they were a bi-compound tire with a harder compound in the middle and a softer compound on the outer edge. I believe he was driving it like it was a Bridgestone RE11 and that may have cause the tires to reach it's limit far faster than it was capable of handling.

As for rain,
I've tried my 255/35/18 RE11s, 245/40/17 StarSpec1s in the rain and its definitely not bad in regular rain. However if there is a lot of standing water, I would be more concern with it. The treadwear 200 tires are definitely aren't extremely terrible in the rain, just not as great as some regular summer tires. If I ever switch to R compounds in competitive racing, I'm sure the RE11 or Starspecs would be my intermediate tires. :)

Personally I would try the PSS even at the cost. It comes with a 6yr 30k warranty if it is same tire size all around. I definitely expect the PSS to outperform the S04 and DW on the track. Since my usual cost for tires is roughly $1200 for the RE11 on the 18s, $900 non-mounted isn't too bad. :)

Actually, DWs are superior in the wet over Star Specs, RS3s...etc. Many people on autox run small tires (around 225-235 on a 9" wheel) during rain events

[derbo]

Would that appy to track days too? Everyone I encounter had used star specs in the rain but it's not in heavy rain.


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[LivesNearCostco]

In theory, tire width shouldn't matter for lateral grip. Friction is F*A*k, or Force (downward force per area unit) * Area * friction constant (tire compound grippiness). If your tire is twice as wide, it has 1/2 the downward force per area--assuming car weight stays the same. If your tire is half the width, A is halved but F per area is doubled so again theoretical friction is the same. But in reality this isn't true because friction does not go up linearly with downward force. Double the downward force per area = less than double the friction per area, so wider tires usually have more grip in the dry and lighter cars normally corner better than heavier cars -- if all else is equal.

Several things also mess up the equation, mostly heat and water. Tires have an optimum heat range so the friction constant "k" increases then decreases as the tires warm up. Narrower tires heat up faster than wider tires. So if you have a light car in cold weather, narrower tires might get into the best temp range sooner. A heavy car in hot weather might like wider tires to prevent overheating. And in rain a narrower tire might cut through the water better to get more surface area onto the ground.

Back from my tangent... all else equal, for dry track I would get 9" wide wheels and 255mm tires in the best compound I could afford (where "best" is some combination of dry grip, wet grip, and ability to handle heat). Since I already have 8.5" wheels, maybe 245mm.

[az3579]

Back from my tangent... all else equal, for dry track I would get 9" wide wheels and 255mm tires in the best compound I could afford (where "best" is some combination of dry grip, wet grip, and ability to handle heat). Since I already have 8.5" wheels, maybe 245mm.


You know, you can fit 255's on a 8.5" wheel. That is the stock setup.


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[LivesNearCostco]

You're absolutely right, and my street tires are 255mm rear on the stock 8.5" rim. I did run 255mm Hankooks on my 8.5" track wheels, then went to 245 ExtremeDW, then 235 Conti/Hoosier takeoffs (which are really like 245mm). There's lots of online debate about which is the best tire width on 8.5" rims--many say the 255mm is better in the dry. I'm not good enough of a driver to say for sure whether 245mm has better turn-in and steering feel, especially since I've never tired the same tires twice in different widths.

I signed up for driving school with local Porsche club next weekend. Was assuming it would be my last event on the Conti/Hoosier slicks, but rain is forecast, so maybe I will be driving the staggered PSS (OEM rims) instead.

[tkundhi]

BP,

I know you are considering a 255 tire but let me share my experience. I recently went with PSS in 245/35 all around on the ZHP. Cheaper than the 255 but not by that much ($206/tire). FWIW, there is a $70 rebate till month end. These tires will be 85% street and 15% track. I mounted them Wed and immediately drove 900 miles to COTA and then put 250 track miles on them this past weekend. Last year I ran the Dunlop Direzza ZII in 255 on an E36 M3. The ZHP is heavier than the M3. The PSS definitely have more grip. So I think compound in more important than width.

Note width will vary based upon manufacturer. Sometimes even within manufacturer. Michelin makes two versions of the PSS in the 245/35 18. One is an OE spec tire for the European M135, the other is the regular version. Both are available here. The OE Spec tire has a wider tread width and is over 1 lb lighter. It's also more expensive by $30/tire. I went for the cheaper version.

FWIW I had no problems running with a 332ti on Hankook (r-comps) and an E34 M5 that was on Hoosier/Contis. I didn't think I would stay with those cars on their sticky tires. But I did. Overall I very impressed with the ZHP on PSS.

Since much of your driving will be street use, do you end up keeping the tires until the are completely worn? With cheaper tires I found myself replacing them sooner. Wet performance went down and noise went up as they wore.

t.

[az3579]

T,
That is some good insight. At this point I have no doubt in my mind that the PSS's performance is top notch. This is why I'm considering them as my next set of track wheels when they wear out, probably in 245 size as well.

Going forward I'm going to consider the tire's performance over its size based on the logical answers I see in this thread.


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