Factory narrower tires seems to hook better...

[chagan02]

Moved this portion of the discussion to the tire thread.

Bought new wheels and tires from a user on here, which I’m super happy with. Had the car aligned and it seems to want to break loose out back fairly easy. Much more easy than factory. Could completely be all tires, although I doubt it. The car has PZero All Season Plus 275s on from the factory, now Michelin Super Sport 305s. I would think the Michelin’s have a softer compound (UTQG rating is lower). No to mention the additional width.

Or the camber in the rear is too aggressive (too negative).

Anyone have any thoughts?

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[Brian@BMVK]

Tire pressures? What size wheel is that 305 mounted on? What road conditions and ambient temperatures?

Contrary to what people think, wider tires don't have a wider contact patch at the same tire pressure as a narrower tire. It's the same area, just a different shape (wider and shorter vs. narrower and longer). Wider tires have higher load capacity and can run at lower pressures while still supporting the vehicle cornering and acceleration loads adequately.

 

[cmxPPL219]

The only change is to the new tire setup right? (i.e., no other suspension changes)

What are your tire pressures?
What are the alignment specs? Did you spec a custom alignment that deviates from factory specs?

 

[cmxPPL219]

Tire pressures? What size wheel is that 305 mounted on? What road conditions and ambient temperatures?

Contrary to what people think, wider tires don't have a wider contact patch at the same tire pressure as a narrower tire. It's the same area, just a different shape (wider and shorter vs. narrower and longer). Wider tires have higher load capacity and can run at lower pressures while still supporting the vehicle cornering and acceleration loads adequately.

(You beat me to it, asking the same questions, but better lol )

 

[chagan02]

Tire pressures? What size wheel is that 305 mounted on? What road conditions and ambient temperatures?

Contrary to what people think, wider tires don't have a wider contact patch at the same tire pressure as a narrower tire. It's the same area, just a different shape (wider and shorter vs. narrower and longer). Wider tires have higher load capacity and can run at lower pressures while still supporting the vehicle cornering and acceleration loads adequately.

Rear pressure (according to TPMS) is 35psi. Rear wheel is 19x11. Yesterday the ambient air temp was 80. Not sure on road temp. Full sun though all day. Was driving in the late afternoon. What you said makes sense, essentially the wider tires doesn’t “flatten” as much when on the ground at the same pressure, so the patch is more width vs length. Whereas the stock tires are have more length but less width. Really all that matters is the area of that patch, correct?

 

[chagan02]

The only change is to the new tire setup right? (i.e., no other suspension changes)

What are your tire pressures?
What are the alignment specs? Did you spec a custom alignment that deviates from factory specs?

Just new wheels and tires. I took it to Ford for the alignment and they had to install camber bolts up front. I measured the front and the height to the fender was 27.5” which seems and inch low. I didn’t install any suspension on it, apparently the first owner did when it was new. Looks like a Ford Kit, springs are blue. I didn’t ask for any special alignment.

 

[Brian@BMVK]

Rear pressure (according to TPMS) is 35psi. Rear wheels is 19x11. Yesterday the ambient air temp was 80. Not sure on road temp. Full sun though all day. Was driving in the late afternoon. What you said makes sense, essentially the wider tires doesn’t “flatten” as much when on the ground at the same pressure, so the patch is more width vs length. Whereas the stock tires are have more length but less width. Really all that matters is the area of that patch, correct?

Drop that to 30-31.

The shape changes what the tire is better at (lateral vs longitudinal grip). It's a little more complex than total area because there are things like dynamic camber and toe changes that a longer but narrower tire is less sensitive to.

 

[cmxPPL219]

Just new wheels and tires. I took it to Ford for the alignment and they had to install camber bolts up front. I measured the front and the height to the fender was 27.5” which seems and inch low. I didn’t install any suspension on it, apparently the first owner did when it was new. Looks like a Ford Kit, springs are blue. I didn’t ask for any special alignment.

Gotcha.

I'd say try what Brian@BMVK is suggesting, he knows what he's talking about
Because in this case, with your new setup, setting the cold PSI to 35, if you drive a bit, you could
be closer to a hot PSI of closer to 40, which would increase rear end breakaway.

Especially on performance tires like Sport 4s/SuperSports or Cup2s, they're really sensitive to PSI and ambient temps. It comes to a point where at a certain PSI, and once hot, the contact patch bulges out and your traction is reduced.

So what Brian is saying, try setting your cold PSI to 30-31.

On the note of the alignment, a bit of negative front camber should help to promote turn-in, coupled with correct tire pressures should bring you back to somewhat neutral handling characteristics.

 

[chagan02]

Okay thanks guys. Will do and take for a test drive this weekend and will report back. The dealer didn’t give me a spec sheet on the alignment, even though I asked. They said they’d give me one after coming in on my 100 mile recheck.

 

[Adamone92]

Okay thanks guys. Will do and take for a test drive this weekend and will report back. The dealer didn’t give me a spec sheet on the alignment, even though I asked. They said they’d give me one after coming in on my 100 mile recheck.

thats weird, so basically no proof they even did the alignment or did it properly?

 

[Brian@BMVK]

Okay thanks guys. Will do and take for a test drive this weekend and will report back. The dealer didn’t give me a spec sheet on the alignment, even though I asked. They said they’d give me one after coming in on my 100 mile recheck.

Be very careful with that type of alignment. "In the green" is not an appropriate measure of alignment quality when the range is so big.

 

[chagan02]

thats weird, so basically no proof they even did the alignment or did it properly?

Exactly. I’d like to know what the car is spec’d at post alignment. I’ve never NOT gotten a spec sheet. I took it to Ford for a reason, perhaps I’ve expected to much.

 

[chagan02]

Be very careful with that type of alignment. "In the green" is not an appropriate measure of alignment quality when the range is so big.

What do you mean by “that type of alignment”? Just within spec? Given that Spec is a large range? What would be an appropriate spec on camber for this car lowered 1”.

 

[Brian@BMVK]

What do you mean by “that type of alignment”? Just within spec? Given that Spec is a large range? What would be an appropriate spec on camber for this car lowered 1”.

"that type" meaning a generic alignment at a dealer or not a performance shop. I've seen some awful alignments posted on this site that were all "green".

You should target the following (do you have camber plates?):

Front
Camber -1.5-1.7 deg, no more than 0.2 diff between each side
Caster 7 deg +/- 0.3 deg
Toe 0.00-0.05 deg per side, 0.00 deg steer ahead

Rear
Camber -1.3-1.5 deg, no more than 0.2 diff between each side
Toe 0.10-0.12 deg per side, 0.00 deg thrust angle

 

[VisceralSyn]

When I put the Ford Performance Street Handling suspension pack on my 17 Mustang GT, I knew she needed an alignment. Took her to the dealership I purchased her at, and when the alignment was complete, they provided me the spec sheet, which has exact measurements, also were in the green. Maybe try a different dealership?

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