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07-16-2018, 04:27 PM | #1 |
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are new tires causing my rear to act squirrely at speed?
a few weeks ago i got rid of my rear pilot super sports (225/40/18) and replaced with falken azenis rt615k+. I do plan to use a set of 4 falkens all around but i am considering going with staggered tires and wanted to be sure of fitment (tire guy said 235/40/18 would not fit but i am a little skeptical of that and may end up with spacers if needed to make it work). car is on stock dampers, but eibach pro springs lowered about an inch. camber is roughly neutral in the front and there is some slight camber from the drop in the back (my guess is about ~1) - i have not touched the camber.
my issue is that at speed (50-60mph+) on the interstate the back end has a feeling of being pretty "floaty" like the rear tires are worn or losing traction and lift-off oversteer is pretty noticeable going into higher speed banks - the kind of banks where the pilot super sports felt very planted. the newer tire setup is engaging traction control on the rear wheels pretty quickly (i can't tell for sure if i am losing setup or traction control is acting over aggressively, but the speeds are too high for me to test it safely with traction off). this effect is somewhat lessened when the tires are warm, but it does not go away completely. lower speed cornering and off-the-line traction seem to be as good or better than ever. my guess is that this probably has something to do with mixing tire compounds (mpss are max perf summer and falkens are extreme perf summer tires) and perhaps the falkens have stiffer sidewalls than the michelins, leading to more nose dive and weight transfer leading to liftoff oversteer? just an uneducated guess. i'm thinking it was a mistake to mix compounds and may just sell off the super sports (they are still at ~50% tread) and go with falkens all around sooner than i anticipated. i just want to see if there is maybe something else I may be overlooking in the suspension that is causing this effect. can someone more knowledgeable than me chime in? |
07-16-2018, 04:46 PM | #2 |
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Mismatched tires front and rear have caused similar issues for me.
Side wall stiffness Michelin > Falken Just because the UTQG number is the same or close to the same does not mean tires are compatible. I have tried combos that have worked and some that do not. It is best to have the same tire and size all around.
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07-16-2018, 04:55 PM | #3 | |
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07-16-2018, 05:00 PM | #4 | |
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It is ALL about the tire compound, not the width. I have 215 front and 245 rear tires. But they are the same tire, and have no issues.
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07-16-2018, 07:20 PM | #5 |
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i'm not disagreeing with you, but why i've got the stickier, lower treadwear tires on the back. shouldn't there be MORE grip than the outgoing MPSS?
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07-16-2018, 07:47 PM | #6 |
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Now you're saying on the interstate and "banks" so it's a little confusing if you're actually pushing the tires or if this is leisurely interstate speed (or if there are two scenarios). I can say that in my experience, the Azenis have a lot of grip, but when they let go, it is not in any way gradual, it is a greasy feeling. The sidewalls of those tires are also insane, which may be contributing to the imbalance you're feeling; the fronts will be squishier, and the rears being stiffer is forcing more body roll since the tire carcass won't budge.
I've run the Azenis a lot in my life, and can say they're really a purpose built tire that are not good all around like the MPSS or other tires ( StarSpec Z1 back in the day, RE-71, etc) but their grip when heated is incredible. I would bet that your traction control is coming on because either the tires aren't heated, the tires haven't been through heat cycles yet, and/or they're engaging more suspension roll which is triggering the loss of traction on the road surface. |
07-16-2018, 09:57 PM | #7 |
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Well, my money is on an off alignment and uneven tire pressure.
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The Following User Says Thank You to Mr.ac For This Useful Post: | Spuds (07-17-2018) |
07-16-2018, 11:34 PM | #8 |
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I just skimmed read this, but try rotating rears to front and front to rears and see what that does.
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07-16-2018, 11:49 PM | #9 |
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it's alignment, you might think -.5 degree is nothing. but it changes how the car feels dramatically when the left and right aren't sitting the same.
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07-17-2018, 12:19 AM | #10 |
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First question, what are the tire pressures?
Second question, what are the tire and wheel sizes? Third, has an alignment been performed since it was lowered? |
07-17-2018, 12:18 PM | #11 | |||
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2. both sets are 225/40/18. wheels are 18x8, +48 offset enkei raijins 3. rims and springs were done by the previous owner. i believe he did get the car aligned (like i said, the car behaved well before the new tires went on. the previous rears did not have in my opinion overly uneven treadwear) Quote:
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07-17-2018, 12:31 PM | #12 |
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I'm going to be "that guy" and ask why you are considering staggering your wheels? Do you make significantly more power than stock? If not, I would advise against a staggered setup, and just stick with a square setup.
Staggered will make the car more prone to understeer, and shorten tire life due to the inability to rotate front-to-rear. If you are doing it because you want an aggressive stance, then just put the same size up front for an even MORE aggressive stance!
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07-17-2018, 01:57 PM | #13 | |
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07-17-2018, 02:24 PM | #14 | |
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The Following User Says Thank You to Spuds For This Useful Post: | re-animator (07-17-2018) |
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