wheel hop after adding larger tires

[jnmac]

I have a 98 Tacoma 2WD Reg Cab, which came with stock 195/14s. I did a body lift, and added 235/75R15s, using wheels with the offset specified for the originals. After 10000 mi I noticed scalloping on the fronts, so I rotated and had two shops confirm the balance and alignment as "in spec". I also replaced the front shocks with standard new ones. I am still getting wheel hop or shimmy at around 60mph on the highway. Any ideas? Thanks!

[CapriRacer]

If the only thing you did was rotate the tires out of the front, then you haven't fixed anything - just moved the problem somewhere else. The tires will eventually develop a new wear pattern, but it may take quite a while depending on how bad the scalloping was.

[jnmac]

Thanks for the response. You are right; moving the scalloped tires to the back does not eliminate them as a problem. However, the tires which were moved to the front had perfectly even wear, and the hop or shimmy is definitely coming from the front end. Also, the rear tires have just about lost the scallop pattern after being on the rear for several months. With the alignment, balance, wheel bearings and steering components all inspected and found to be OK, I wonder if the additional mass/diameter of the larger wheel/tire combo is too much for the stock suspension, or if the alignment specs need to be altered.

Thanks again!

[CapriRacer]

Did you get aftermarket wheels? Do they pilot off the hubs? If not, then that could be the source of the vibration - non-concentric mounting.

I don't think the mass has anything to do with the vibration, but just for curiositiy - what inflation pressure are you using?

[jnmac]

Yes, aftermarket wheels, and not the most expensive ones, either. I actually had little choice in wheels, as this model truck has a positive offset like a front-wheel drive sedan!

The wheels are not piloted on the hub. Checking into this, I'm not sure the shops I used for balancing had the lug-centric balancing equipment. I know my local Toyota dealer has this - I may give them a try.

Recommended full-load inflation on the tires is 50psi - I am running at 40, as the vehicle is never loaded.

From what I understand, the scalloping and hopping are probably two separate issues. I have not seen evidence of scalloping on the fronts since the rotation/alignment, so I may be down to solving the balance issue.

Still have the original wheels and 195/14s; maybe I'll put them on for a test, as I really didn't drive this vehicle on the highway much before the modification.

Thanks again for the replies and advice - it is appreciated!!