Got 17x10s and M&H drag radials 325 47 17, High speed sway and vibration normal? What psi?

Discussion in 'Wheels & Tires' started by Andy13186, Jan 17, 2020.

  1. Andy13186

    Andy13186 Well-Known Member

    Vehicle(s):
    2018 Mustang GT 10speed
    Joined:
    Sep 19, 2018
    Location:
    Florida
    Posts:
    1,080
    Likes Received:
    353
    0   0   0
    Hi I got some VMS 17x10 and M&H 325 45 17 drag radials on my mustang, they grip amazing but I get a lot of sway at high speeds and vibration at like 100+ mph. So far I tried 32 and 30 psi, is that proper for the street or should I go lower? The sway is kind of concerning and the vibration too especially at like 100-130 mph. My first set of drag radials so I dont know whats normal.

    I am running the stock pp1 front wheels and tires with these on the back.

    Any tips or advice would be appreciated.
     
  2. OP
    OP
    Andy13186

    Andy13186 Well-Known Member

    Vehicle(s):
    2018 Mustang GT 10speed
    Joined:
    Sep 19, 2018
    Location:
    Florida
    Posts:
    1,080
    Likes Received:
    353
    0   0   0
    I lowered the tires from 31 to 26 and that seems to solved the vibration at high speeds mostly, and reduced the sway. Here is what the contact patch looks like at 26 psi, you can see the outside 1 inch of each tire is not in contact but I think thats due to camber and I dont know if thats avoidable. They grip amazing my max acceleration G forces went from .78 on the street to .92 on the street.

    Yxmmfkm.jpg

    Side pic


    amAwmS6.jpg
     
  3. aleccesarenriquez

    aleccesarenriquez Well-Known Member

    First Name:
    Alec
    Vehicle(s):
    2017 GT PP
    Joined:
    Mar 19, 2018
    Location:
    San Antonio, TX
    Posts:
    357
    Likes Received:
    105
    Occupation:
    Engineer - Med Devices
    Rating:
    100%
    1   0   0
    The tire width is probably a little too big for the wheel width. 325s are usually for 11" wide wheels. Most people run 305/45/17 on the 17x10s. Not sure if that would cause your issue or not but it's worth considering.

    Also when you got the tires mounted, did you have them balanced? If it has weights on the rim, sounds like you did, so I wouldn't recommend taking them off unless you know for a fact they were balanced incorrectly. Take it to another shop to see if they are within spec.

    Lastly, i'm not sure if M&H are different but 30-32 psi is pretty high for a drag radial from what I know. I usually keep my MT Et street SS around 22 psi. Usually higher psi should reduce sway so I doubt this is causing your issue, but it's something to keep in mind as you will wear out your tires prematurely if you keep it at that high of a tire pressure.
     
  4. OP
    OP
    Andy13186

    Andy13186 Well-Known Member

    Vehicle(s):
    2018 Mustang GT 10speed
    Joined:
    Sep 19, 2018
    Location:
    Florida
    Posts:
    1,080
    Likes Received:
    353
    0   0   0
    Yes they were balanced but they were balanced at 30+ psi which is definitely too high, but they still moved on the rim. I dont know if they used tire lube when installing but there were no signs of that which I normally do have signs of with street tires. I know for a fact now that the tire is not in the same place on the rim as it was when they balanced it so the balance is totally invalid and possibly negatively affecting the setup. The sway is pretty much gone running 20-22 psi (cold-hot temps) but the vibration from misbalance is apparent above 80-90 mph. The grip is great though in a straight line , never felt anything like it but drag mode on these cars is so violent that apparently its moving the tire on the rim.
     
  5. aleccesarenriquez

    aleccesarenriquez Well-Known Member

    First Name:
    Alec
    Vehicle(s):
    2017 GT PP
    Joined:
    Mar 19, 2018
    Location:
    San Antonio, TX
    Posts:
    357
    Likes Received:
    105
    Occupation:
    Engineer - Med Devices
    Rating:
    100%
    1   0   0
    Yeah definitely get them checked out for a misbalance. See if the weight needs to be re-distributed. If they move again and go out of balance again, might have to remove the tires from the wheels to see what's going on.
     
Loading...

Share This Page