Strange handling after new rear tires?

[RADRACR]

Replaced my rear Bridgestone RE-11s with a fresh pair and my car feels super "boaty" when performing short aggressive inputs (like a fast lane change). Feels like the rear takes a full 1-second to catch up with the front.

I won't rule out that it could just be in my head; I've been performing these maneuvers just to test the new tires But I don't recall it ever feeling like this. Or maybe I've had a suspension problem for a long time and I never noticed til now? What does the peanut gallery say?

[pokeybritches]

Do your front and rear tires match? Are the rears oriented correctly?

When I replaced all four tires with RE-71R's, the extra grip highlighted some of the weaknesses in the suspension.

[RedOctober]

Originally Posted by RADRACR

Replaced my rear Bridgestone RE-11s with a fresh pair and my car feels super "boaty" when performing short aggressive inputs (like a fast lane change). Feels like the rear takes a full 1-second to catch up with the front.

I won't rule out that it could just be in my head; I've been performing these maneuvers just to test the new tires But I don't recall it ever feeling like this. Or maybe I've had a suspension problem for a long time and I never noticed til now? What does the peanut gallery say?

After years in the tire industry, as already mentioned:
Are your tires matched and mounted correctly?
This is so common it's crazy.

Sometimes it's simply the "crown" of the new tire and after a couple hundred miles there are no issues.

If the tires are in fact matched and mounted correctly, then I can suggest an easy way to break in the crown of the tires.

[RADRACR]

Yes all four are RE-11; I replaced with same thing I had before. The fronts are 2-1/2 years old and wear much slower than the rears. Mounted correctly; checked for the "outside" label on sidewall.

I got a chance to power through some sweeping corners today. The cornering feels good through the apex but again, there is an unsettling shimmy when I straighten out. The lateral grip does seem improved over the old tires. I guess the best way to describe it is that the rear wants to remain in its current direction instead of going where the front wants to go. Then the rear is like "ok, if you insist".

[imz4n]

Did you reset your tire pressure monitoring system? New tires are coated, as the manufacturer does not know when the tires will be sold. Get out and put 100 miles on the tires on a freeway ( not in town driving ) and let the tires heat up and cool down. Heat cycling.

[mckenna4978]

I had the same thing happen when I swapped the tires out from what was on the car at time of purchase being an all season Kuhmo Ecstasy tire versus the new Michelin pss which I wanted. At first the handling was so different and felt slow. Then when I got a couple of hundred miles on them and the releasing agent burned off the Michelin's were impressive. We'll see in a couple of days when I have some apex arc-8 wheels in satin black fitted with continental extreme contact dw tires from tire rack thrown on. I'm sure it will be the same process over again of releasing agent burn-off and initial slippery handling. Nothing to worry about though. Congrats on the shoes for your ride!!!

[polar]

Last time I changed the rears the tire guy put in 3+ bar and the zed floated around like a drunk hippo.
...so check the pressure.

[The HACK]

How old were the old rear tires? Were they worn down to or past the wear bars?

An easy explanation is, worn off tire tread has less "tread squirm." As in the tread block is so much shorter that they don't flex as much. New tires have taller tread thus on short, quick change of direction it takes a little bit longer for the tire tread to respond.

Hence a lot of racers and DE "champions" shave r-comps, because treaded race tires on full tread tend to exhibit that squirmy feel when new. BEST grip on typical greased tires come after 1-2 heat cycle and tread shaved away.

[StickMon]

^WHS First thing I thought of.
I run my tires to near bald. The balder they get, the better they feel, as long as I don't hit a puddle.
When I put a new set on I can definitely feel the tread squish around.

[inTgr8r]

Lots of good advice already.
One more thing to check are your RTABs

[gas-can]

Hi Rad,

I have the little brother of the group, but I had the same issue last time I changed just the rears after a stupid nail. Car felt very floaty/unstable/terrifying on corners.
I tried everything- what fixed it for me was replacing the fronts with new ones as well.

I have a feeling the older fronts have less grip, which causes some kind of imbalance with the new grippier tires in the rear (and vice versa I'd imagine).

Which is the reason why I'm about to spend another grand replacing all 4 again, thanks to the stupid nail in the sidewall I received yesterday

gc

[m3griff]

Originally Posted by RADRACR

Yes all four are RE-11; I replaced with same thing I had before. The fronts are 2-1/2 years old and wear much slower than the rears. Mounted correctly; checked for the "outside" label on sidewall.

I got a chance to power through some sweeping corners today. The cornering feels good through the apex but again, there is an unsettling shimmy when I straighten out. The lateral grip does seem improved over the old tires. I guess the best way to describe it is that the rear wants to remain in its current direction instead of going where the front wants to go. Then the rear is like "ok, if you insist".

I had exactly this issue after changing out my rears only on my 06 3.0Si. Sweeping corners were the worst - unsettling. After checking everything (alignment, balance, pressures,), I replaced the fronts and presto - like new again.

My hypothesis is that the short wheelbase has an impact.

Jeff

[aarofloyd]

I know this is a super old thread, but experiencing this for the first time on my car after getting her some new rubber. My question is...(if any of you are still on the forum 13 years later)...do you think its ok to drive the car like this? Is the rear end actually loose or is that just a false sensation I'm feeling? 2 brand new Continentals on the rear, and 2 existing Toyos on the front with plenty of tread left....dont really care to spend an extra $600 if its safe and I can just learn to live with it. I mean, who doesn't want to continually step the back out anyway?!

[KevinC]

Mixing Toyos and Conti's? Yikes. I tried a similar stunt on my ZHP coupe a few years ago, mixing a pair of Pilot Sports with Conti's, and the handling was SO bad, it felt dangerous. Within 2 weeks I swapped the other pair so that the tires were identical all the way around, and all was well again. It was so bad that I was almost positive that the tire mismatch couldn't possibly be causing the problem - but in fact it was.

[aarofloyd]

toyos is what was on there when i got the car. Unfortunately picked up a nail, and shop only had 2 options on hand....conti's or road huggers??? easy choice....

Going to try and pay very close attention to the behavior the car is showing now...and try to figure out if it really is unsafe or just in my head

[Molez93]

The feel of the car is going to tell you how safe or unsafe it is. My concern would be the front-to-rear difference in relative grip dry, and if the dynamic changed with rain/wet.

I've only ever had "mismatched" tires on race cars (and only a couple times when in a jam). New, sticky rubber on the fronts meant every turn was a powerslide as the rears were easy to break loose compared to the fronts. Swap them to the rear and now the front end understeers like a pig in every corner.

Some mismatches will work better than others, and it sounds like you don't much enjoy how this pair is. I'd doubt it's going to get better assuming you've confirmed pressures are right and put a few hundred miles on the new ones to get past the factory sealant/mold inhibitor/whatever on the outside of the new ones.

[Efthreeoh]

Originally Posted by aarofloyd

I know this is a super old thread, but experiencing this for the first time on my car after getting her some new rubber. My question is...(if any of you are still on the forum 13 years later)...do you think its ok to drive the car like this? Is the rear end actually loose or is that just a false sensation I'm feeling? 2 brand new Continentals on the rear, and 2 existing Toyos on the front with plenty of tread left....dont really care to spend an extra $600 if its safe and I can just learn to live with it. I mean, who doesn't want to continually step the back out anyway?!

Why would you mix tires on a sports car like a Z4? It makes no sense. If you picked up a nail and it was more than an inch from the tread shoulder, why didn't you just have the tire repaired?

[aarofloyd]

Originally Posted by Efthreeoh

Why would you mix tires on a sports car like a Z4? It makes no sense. If you picked up a nail and it was more than an inch from the tread shoulder, why didn't you just have the tire repaired?

It was in the tread shoulder and rubbed against the sidewall inside the tire making it non-repairable. The fronts still had like 8/32nds on them so definitely didnt "Need" replacing. I may end up just replacing them though...drove all weekend and the car still isnt responding well.