Gwampa

My daughters 2005 Malibu LS is equipped with a 3.5 Liter V6. She has always had trouble with the brakes, as they seemed like they were warped and would viberate to the point that it was difficult to stop the car. From 70 or 60 and trying to slow down had gotten to the point where it was almost dangerous. I finally took matters into my own hands and replaced the rotors and pads on the front. The old rotors had been machined and although they had sufficient meat left (thickness), I just couldn't let the viberations continue and so put it in the air and did it.
To anticipate any steering problem questions, the front end was recently alighned by a reputable local shop and checked thoroughly. There are no suspect parts in the front end. The struts are good and the rack & pinion had been recently replaced along with the intermediate steering shaft.
During the replacement I found somthing interesting and a bit disturbing which is the reason for my question, so I'll continue. Went by the local parts store and picked up pads and rotors for the car listed earlier in the post. Removed the piston assembly and retracted the piston with my large trusty c-clamp and hung the piston from the springs with a piece of wire to keep it out of the way.
Removed the pad support assembly from the spindle (two very tight bolts) and removed the original rotor. This removed rotor measured 11" in diameter. Began to replace with the new rotor, cleaned real thoroughly with Brakleen (Red Can) but the pad support assembly would not fit or bolt back on. It fit the studs (correct spread) but it was because the new rotor was 11.5" in diameter. Went back to store and asked if there was an 11" rotor available (and if I had the correct pads, I did). Got new 11" rotors for listing of 2005 Malibu Classic. Back to garage and tried to install 11" new rotors, Nope! no go. This time the stud spread was wrong (too wide). Back to store (3rd time), this time I took one old rotor with me. Finally found correct rotor. Was listed under 4 cylinder for that year Malibu.
Now I'm concerned. Car was bought from major used car chain and certified to be up to factory specs. Would the factory put a V6 in a 4 cylinder frame? Is there future wear problems putting the extra weight on the lighter brake system? Is my daughter and her children (my grandsons) at risk? Opinions and technical advice appreciated.

EvansBlue

The added weight of the V6 is not enough to make much of a difference stopping.

The Malibu Classics were almost solely sold as rental car in 05 and 06. They basically just used what was left of the 1997-2003 constructions of these cars.

Gwampa

An update.....seems you were both correct. The 11" rotors (really 10 7/8") are standard for the Malibu (either V6 or 4 banger). The 11 1/2 (really 11 21/32") are probably for the SS with the 3.9 liter motor. It's a guess but I feel pretty sure it's true or close. All is cool here and thanks for the responses. Now for this:

Accuracy and honesty on this forum is essential and and of utmost importance. This being said, Brent I owe you and a number of other members here an apology. I'll listen closer to the more astute before I pop-off again about technical things I know nothing or little about. You were and are correct about the 115mm spread on the N body Malibu's and I was totally off-base. Giving incorrect information can have a far-reaching negative effect and I don't want that to happen. Consider me contrite and humbled. Thanks.