Handling issues after wheel and tire install

[ultimateburrito]

So I decided to pull the trigger on new rims and tires for my 12 gt track pack. So I ordered two 305/30r19 for the 10" rear rims and just swapped the old fronts onto the new rims. I know it's retarded but I didn't think of the sidewall height issue. My fronts are 40 sidewall and rear is 30. Is this causing my soft handling and weak turn in? I am ordering fronts and don't know if I should get 30 sidewall or 35. I hope somebody can tell me that it's just the sidewall difference that makes it handle like crap.

 

[Vert]

I would think it would be more of the staggered set up rather than the sidewall height.

 

[_Snake_]

Aren't the Track Pack / Brembo package wheels 9" wide?

 

[ultimateburrito]

I bought the replicas from AM aND the rears are 10 fronts are 8.5

 

[Angry50]

isnt 305 too wide for a 10inch wheel? what tire you using?

 

[ultimateburrito]

isnt 305 too wide for a 10inch wheel? what tire you using?

It's slightly wider than recommended, but I know people that run 305 on a ten without any problems. That's not the issue. It's my turn in. There's no sharpness in my steering it's all floaty.

 

[Angry50]

straight line sure its fine but the sidewall would probably roll around some being oversize. what size is your front tire? are the front and back off by a lot?

 

[Zandura99]

More info. What exact tire size, tire model and brand on front. Same info for back. You might be surprised, but just the tire type can be enough to cause the handling problem you are experiencing. Many folks think of your tires as fronts and rears separate from eachother because we have been straight line cars for so long... but now that our cars handle well they also need to have tires that work together well. In your case, if you are running the 255/40R19 front, they are 27 inches tall. The 305/30R19 is typically 26.2 inches tall. That doesn't help either. If you have a major mismatch, you cannot expect the handling to be on par with what you experienced with the factory setup. Its not always wrong (however if it handles bad, there usually is an issue), its just not right for turning. Say you had a Pirelli Pzero Nero AS on the front and a Conti DW (summer) on the back, that would cause the handling you are expierincing... just for example.

 

[ultimateburrito]

More info. What exact tire size, tire model and brand on front. Same info for back. You might be surprised, but just the tire type can be enough to cause the handling problem you are experiencing. Many folks think of your tires as fronts and rears separate from eachother because we have been straight line cars for so long... but now that our cars handle well they also need to have tires that work together well. In your case, if you are running the 255/40R19 front, they are 27 inches tall. The 305/30R19 is typically 26.2 inches tall. That doesn't help either. If you have a major mismatch, you cannot expect the handling to be on par with what you experienced with the factory setup. Its not always wrong (however if it handles bad, there usually is an issue), its just not right for turning. Say you had a Pirelli Pzero Nero AS on the front and a Conti DW (summer) on the back, that would cause the handling you are expierincing... just for example.

The fronts are kumho 255/40r19 on 19×8.5, the rears are hankook ventus v12 305/30r19 on 19×10. The fronts are actually .82 of an inch taller by calculation. I have some hankook ventus v12 255/35r19 on the way. Which are very close (.08 inch) shorter than the rears. Will this fix my problem?

 

[Angry50]

your front tires are taller than your rear currently which could be causing a problem

 

[el jefe 302]

Kumhos are junk, get a gopro and mount it facing the sidewall on the front tire. Go around some turns and look at the footage, I bet they are flexing like a MoFo.

 

[Zandura99]

The fronts are kumho 255/40r19 on 19×8.5, the rears are hankook ventus v12 305/30r19 on 19×10. The fronts are actually .82 of an inch taller by calculation. I have some hankook ventus v12 255/35r19 on the way. Which are very close (.08 inch) shorter than the rears. Will this fix my problem?

sorry was busy at work the last few days and didn't get on here! Yeah, I bet that was the issue, at .82 inches taller. If they were 4x as well, that would add to the problem (performance all season). Getting diameters right on and having the same tire all the way around should work much better. You might find that the understeer is a bit exaggerated with your size discrepancy.... but maybe not. That is the only risk running such a huge stagger, your rears can feel like they overpower the fronts on the initial turn in.

 

[80KM2E]

Thats a massive stagger... Ford actually recommends against it in one of their tech videos I've seen on the GT500.