I went on the highway today for the first time in about a month. Although I wasn't accelerating quickly, it didn't feel particularly smooth. At one point I boosted lightly in 5th gear at about 80mph, and the front end shuddered badly under acceleration. After I let off, it went away.

Is it possible for there to be a wheel balance problem that occurs only after a certain speed, and just under acceleration? I highly doubt it's my motor mounts, because the bottom 3 are only a few months old from Inline Pro. An engine swap was done several months ago, btw. Any ideas would be appreciated, thanks!

P.S. Using stock 15" 99-00 Si wheels and Falken Ziex 512 205/50/15 tires.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by USE2B16A &raquo;</TD></TR><TR><TD CLASS="quote">Is it possible for there to be a wheel balance problem that occurs only after a certain speed</TD></TR></TABLE>

...yes...

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by USE2B16A &raquo;</TD></TR><TR><TD CLASS="quote">and just under acceleration?</TD></TR></TABLE>

...no. A wheel balance problem may only be noticeable at certain speeds, but wouldn't happen only under acceleration. Sounds drivetrain-related, rather than wheel/tire-related. Maybe a dirty/clogged air filter or fuel filter, or some condensation in the gas tank?

 

The car runs very strong, so it's not a problem with the engine. It's a severe vibration/shudder that doesn't happen during everyday driving. The car has 300+ whp on stock axles, although I have a Quaife. Could it be an axle problem? Someone else mentioned wheel bearings. What do you think?