Really Weird Handling - and a reason for it!

[m3griff]

Wanted to post this for information for everyone:

About 6 weeks ago, I replaced my two rear tires (Hankook Ventus V12's) with two more of the same. The old tires had about 18K miles on them and were getting a little slick. Thought it best to make the swap with the SC rainy season here (any day in the summer). My fronts are also Hankook V12's - also with 18K miles - but still have a great deal of tread ().

This partial replacement turned out to be a big mistake. From the first day, my car felt very different (in fact, I stopped on the way home thinking one of my wheels was loose). Unsettled in long sweeping corners - it would shift out; twitchy and requiring constant correction on the interstate. At first, I thought it was the break in on the new rears (Hankooks seem to take a while to settle in), but never did get better. To make matters worse, I swapped over to a TCK coilover suspension about a month ago. If anything, that accentuated the problem. The rear felt like it was steering the car a bit. It was really becoming hard to enjoy the car.

After doing all kinds of searches, I decided that it couldn't be the tires - I have replaced rear tires on other cars before with no problems. So, I thought it HAD to be bushings. But, a friend of mine convinced me to go ahead and buy some new Hankook front tires before doing anything else.

I did that and the car is instantly right again. Perfect handling and now I can enjoy my new suspension.

I have never seen anything like this before - and I don't understand it., The only thing I can think of is that the short wheelbase and the fact that the driver sits just in front of the rear wheels make the car really sensitive to "small" changes.

Just wanted to get this on record so that someone else might see this when faced with a similar problem. It would have saved me a lot of aggravation.
Anyone else run across this issue?


Cheers,

Jeff

[kklin]

Who did the new suspension install, you or a shop? Did you check that all the front bolts/lugs were torqued?

While I had my E36M and was autocrossing regularly, I had an incident where the rear felt progressively sloppy while I was driving on the street. After checking the rears several times and not finding anything wrong, a few days later I decided to check the fronts and found that I had forgotten to torque one of the fronts! So the front lugs (I had studs) were coming loose. After torquing them, all was fine again.

I wonder if something similar happened to you, and were fooled by concentrating on the wrong end.

[m3griff]

I did the suspension install. Everything is torqued and alignment was done. The key is that the problem occurred before the install and remained after. The cure was the new front tires.

Jeff

[Finnegan]

My bet would be that the front tires, while still having a lot of thread, have lost a lot of grip and are actually quiet "worn". Exposure to UV, heat/cold, lots of heat cycles-- all that ages the rubber. Kind of like hockey pucks in the front compared to the nice new sticky rear tires. That unbalanced the car.

[Huz-Z]

This is great information. I am running Hankook V12s and although I don't think they are in need of replacement for a while yet, I will plan to replace all four tires when the time comes.

[inTgr8r]

Originally Posted by Finnegan

My bet would be that the front tires, while still having a lot of thread, have lost a lot of grip and are actually quiet "worn". Exposure to UV, heat/cold, lots of heat cycles-- all that ages the rubber. Kind of like hockey pucks in the front compared to the nice new sticky rear tires. That unbalanced the car.

^on this note
I've seen a few tires that look to be in great shape, but if you look at the date code are 5 or more years old.
Your fronts could have been old & out of date.
I also check new tires when I get them.
They sometimes sit in inventory for a long time.


IIRC, expiration date = 6yrs from mfg date.
e.g. code is 1st 2 numbers are week, 2nd 2 numbers are year (post 2000)
...this example is 8th week of 2006

[HaiDef]

id also get an alignment done after changing anything with your wheels.

[gtMc]

I sheepishly admit I did something similar about 3 months ago, (with stock conti's) -swapping half of my set for another used pair to extend overall life a bit. a bad and cheap move on my part.

Long Story short I too have noticed the same type of questionable handling characteristics through long sweeping turns. "Unsettled in long sweeping corners - it would shift out; twitchy and requiring constant correction on the interstate." is a good description. Dubbedown smartly convinced me to just get new tires rather than get into suspension mods, and I am about to do that. I am now even more confident that a nice new set of Michelins will have a dramatic improvement over a mixed set of crappy used stock contis.

[David70]

Besides the tires being too old on the front (past expiration) I don't understand the logic behind the poor handling. The rear tires on my car are far more worn than the fronts and it handles fine, if I go to having new tires on the rear and worn (but not excessively worn) on the front I don't see how this changes the overall stability of the car as they will then both have acceptable amounts of tread left. Seems odd to just replace all four regardless of whether two of them are worn too much or not. Somehow worn out tires on the rear and less worn on the front is ok but the reverse situation isn't?

Not saying it isn't true just don't understand why.

[m3griff]

Originally Posted by David70

Besides the tires being too old on the front (past expiration) I don't understand the logic behind the poor handling. The rear tires on my car are far more worn than the fronts and it handles fine, if I go to having new tires on the rear and worn (but not excessively worn) on the front I don't see how this changes the overall stability of the car as they will then both have acceptable amounts of tread left. Seems odd to just replace all four regardless of whether two of them are worn too much or not. Somehow worn out tires on the rear and less worn on the front is ok but the reverse situation isn't?

Not saying it isn't true just don't understand why.

I don't necessarily understand it either. My rationale in replacing only the rear tires was just what you describe. How could this not work? But, I got a real difference that others verified as well. Maybe it has to do with some kind of "tread squirm" on the full depth rear tires not working well with the (relatively) worn front tires? I don't know. Is this limited to Hankook V12's? I dont know that either. I don't have the fronts anymore, but they were only about two years old. They have only been on the market since sometime in 2009, I think.

For an explanation, I'm leaning toward a combination of tire and car characteristics. I will definitely replace tires as a set on this car.

Thanks for the replies so far. I'd like to hear more experiences if anyone has any.

Jeff

[m3griff]

Originally Posted by Huz-Z

This is great information. I am running Hankook V12s and although I don't think they are in need of replacement for a while yet, I will plan to replace all four tires when the time comes.

Huz,

Love the color of your car and the fact that you are consistently high on the 3.0si. I have had M3's (note the username) and driven a number of Z4M's, but the SI is just about perfect for me. (except there are not enough mod options). Great balance of power, looks, handling and low maintenance demands.

Jeff

[Finnegan]

I'm sure someone can explain in a way more articulate way than I can, or will correct me if my understanding is wrong, but here goes.

If the front tires and rear tires are of the same vintage, installed at the same time, then the rubber aged at the same rate. Initially more grip after break-in and removal of some tread, then less and less as the tire ages, goes through heat cycles (heating/cooling as the tires are run), gets sun/UV damage. But the point is that they will have comparable relative grip front to rear with no bias as they age together. (I'm leaving out things like suspension set-up, alignment, and other considerations--yes they are there--to focus on the tires only.)

A new tire has has nice soft rubber and is quite sticky; a old tire is hard and much more slick, regardless of tread depth. Think about what happens to plastic or rubber left in the sun for a period of time--hard, brittle, damaged. (A tire with 18k miles and 2 years has aged--a lot--regardless of tread remaining.)

So effectively we have 2 very high performance summer tires and what essentially equate to 2 season tires (or possibly worse, depending on aging). To put it another way, we've got really hard, old hockey pucks on the front of the car, and really sticky new fresh rubber on the rear.

In this scenario, what happens to the car's balance? What happens when we push the car hard into a corner, especially a long sweeper, with a lot more grip rear vs. the front (and relative to baseline equally aged tires)? What happens on the freeway (especially grooved cement), when the sticky rear pushes in one direction with the grooves (and it's not the direction we want the car to go)?

These differences would not be nearly as apparent on a car like a family sedan or SUV (which won't be used to attack corners). But on a performance car, where we tend to push the car a bit, and where alignment is typically more aggressive (negative camber, etc.) it's going to be noticeable.

[nwflbimmer]

I had never heard about an expiration on tires before. I always knew when the tiny crackes appeared and the dry rot set in it was time to replace them. Now maybe you have helped me possibly fix my problem. I just recently purchased my 07 Mcoupe and while driving the car down from Ohio to Florida, I kept thinking that the tires seemed very noisey to me. The car only has 30k miles on it, but the majority of those miles where put on during the first two years. and the car hasn't been driven much in the last 3 years. There is alot of tread still on the tires. I was kind of thinking the noise might be coming from cupping on the tires. But how am I to know for sure? I hate to but a set of tires for no reason.

[Finnegan]

Originally Posted by nwflbimmer

I had never heard about an expiration on tires before. I always knew when the tiny crackes appeared and the dry rot set in it was time to replace them. Now maybe you have helped me possibly fix my problem. I just recently purchased my 07 Mcoupe and while driving the car down from Ohio to Florida, I kept thinking that the tires seemed very noisey to me. The car only has 30k miles on it, but the majority of those miles where put on during the first two years. and the car hasn't been driven much in the last 3 years. There is alot of tread still on the tires. I was kind of thinking the noise might be coming from cupping on the tires. But how am I to know for sure? I hate to but a set of tires for no reason.

Wait, so these are the original Contis tires that are now close to 6 years old? (If not, what kind of tires? Any idea how many miles/years on them?) Take a look at Intgr8's post, to find the mfg date for the tires.

If they're the original tires, yes, new tires for sure! It will be a totally different car! And much safer too. The original tires are horrible IMO and were hard as rocks and noisy as hell at 15k--I killed mine at a car control clinic, put some Star Specs on, and never looked back! (Take a look in the tire section for some other good replacement choices.)

[nwflbimmer]

If I swap tires I may go with the same tires on my Z3 Coupe. They have been very quiet tires and super aggressive looking, Sumitomo HTR Z II.

[Finnegan]

The Sumis HTR IIIs are a pretty good tire. We put them back on the wife's Z for wet weather and "winter" use (California winter that is). Quiet, good street tire. Good choice if you don't plan to AutoX or take the car to the track. More info and a thread on this vs. Hankooks over here.

[nwflbimmer]

well my tires are not old. The date is 4711 = last week of november 2011. I think. The make of the tires are Bridgestone Potenza. Are the the run flats? Maybe that would explain the rough ride and noise.

[m3griff]

M cars don't get runflats. But I have never liked the Bridgestones on any car I've had. At 30k miles on those, it's time to swap. The new Michelin Pilot Superports are great tires and still priced nicely.

[nwflbimmer]

There isn't 30000 miles on the tires. According to my carfax there is less than 4000 miles on the tires. I just don't understand how tires so new can be so noisy. I wish there was another coupe nearby to compare with.

[m3griff]

Originally Posted by nwflbimmer

There isn't 30000 miles on the tires. According to my carfax there is less than 4000 miles on the tires. I just don't understand how tires so new can be so noisy. I wish there was another coupe nearby to compare with.

Sorry - misunderstood your post. I don't understand it either, though some tires are just that way. These cars are not quiet at all in any case. You might do a little research on tire rack - they have lots of information and test results that might help you determine if this is normal or not.

Jeff

[m3griff]

Originally Posted by Finnegan

I'm sure someone can explain in a way more articulate way than I can, or will correct me if my understanding is wrong, but here goes.

If the front tires and rear tires are of the same vintage, installed at the same time, then the rubber aged at the same rate. Initially more grip after break-in and removal of some tread, then less and less as the tire ages, goes through heat cycles (heating/cooling as the tires are run), gets sun/UV damage. But the point is that they will have comparable relative grip front to rear with no bias as they age together. (I'm leaving out things like suspension set-up, alignment, and other considerations--yes they are there--to focus on the tires only.)

A new tire has has nice soft rubber and is quite sticky; a old tire is hard and much more slick, regardless of tread depth. Think about what happens to plastic or rubber left in the sun for a period of time--hard, brittle, damaged. (A tire with 18k miles and 2 years has aged--a lot--regardless of tread remaining.)

So effectively we have 2 very high performance summer tires and what essentially equate to 2 season tires (or possibly worse, depending on aging). To put it another way, we've got really hard, old hockey pucks on the front of the car, and really sticky new fresh rubber on the rear.

In this scenario, what happens to the car's balance? What happens when we push the car hard into a corner, especially a long sweeper, with a lot more grip rear vs. the front (and relative to baseline equally aged tires)? What happens on the freeway (especially grooved cement), when the sticky rear pushes in one direction with the grooves (and it's not the direction we want the car to go)?

These differences would not be nearly as apparent on a car like a family sedan or SUV (which won't be used to attack corners). But on a performance car, where we tend to push the car a bit, and where alignment is typically more aggressive (negative camber, etc.) it's going to be noticeable.

Finnegan,

I think your analysis sounds very likely - at least it makes sense to me.

Jeff

[kklin]

Originally Posted by m3griff

M cars don't get runflats. But I have never liked the Bridgestones on any car I've had. At 30k miles on those, it's time to swap. The new Michelin Pilot Superports are great tires and still priced nicely.

FYI - Michelins currently get a $70 rebate!

If you find this info useful, consider browsing through my TireRack affiliate link at http://p1gear.com. Once at the TireRack site, click on View All Special Offers.

So far I've only driven on the Continental DW and Star Specs on my M Coupe. I don't find the latter noisy for street driving.