Having a strange issue where my 2009 TL AWD vibrates while braking but only between 50mph and 40mph. Car has 133k miles and was recently at dealer and was told its most likely rotor issue as they inspected suspension and found nothing. Just installed new Power Stop rotors and ceramic pads and same problem persists. Problem does not affect anything other than it's extremely annoying and I am completely out of ideas. No other vibrations can be felt at any speeds both while accelerating and braking except between that specific range.

 

And the wheels are balanced?

 

Yes wheels and tires are balanced, very smooth at highway speeds. Wheels are aftermarket Voxx MGA 18's and tires are Continental Control Contact Sport SRS from Discount Tire. I suppose the wheels could be the issue but I would assume the vibration would be constant at whatever speed and not just while braking.

 

That depends, if it's not hub centric you will have random vibrations at high speed when it goes off centre. Do you know if it sits flush on the hub? Do you have a 2nd set of wheels to try?

From my quick search, 4G TL hub bore size is 64.1
Your wheels look like 73.10
Do you have hub rings?

 

No hub rings installed so you could be onto something. I do have the original wheels that came with the car but one of them is bent beyond repair which is why I put the new ones on.

 

It's ONLY braking? Or cruising between 40-50mph too?
you could try 2 or 3 of the OEMs with the 1 or 2 aftermarket wheels to see if things improve.

 

Yes only with braking and only between those two speeds. Braking at any speed above 50mph feels totally normal and same at low speeds. I stumbled onto a different forum for BMW's and found someone with a similar issue that turned out to be control arm bushings so when I took my car to the Acura dealership I was surprised that all was fine and nothing was found during the inspection. I have no reason not to trust their findings as I have been using the same dealership for years with no problems. I suppose I could try and get a second opinion from an independent shop.

 

Not sure if it the same issue but I had some 'strange' vibration during braking and it turned out to be due to the front struts being worn out (2012 Acura TL SH-AWD 105k miles). Struts were original. I personally would steer clear of the cheap strut assemblies, if it is the case, as they are noisy, especially when temp is below freezing. The Acura strut assemblies are discontinued as well. Most would recommend the Acura replacement struts but I used KYB and I am satisfied.

 

Vibration while braking is most likely from the brakes. No other systems should be in play when you apply brakes. If you feel vibration in the pedal only, it usually indicates the rear brakes, in the steering wheel, indicates the front brakes. Just because you replaced the rotors, does not mean that they are not out of round. I have seen new parts that came out of the factory bad. Have a brake shop look at the round of the rotors, they have the tools to check it pretty easily.
If the problem is only between 40-50, then something else is going on too. I would take a look at all the suspension bushings, sometimes the dealer misses things.

 

I would try out different wheels to (OEM) 2 at a time to rule that out. I spent whole summer with some road noise that I thought was mechanical but I suspect the tires are wearing out. I have winters (17s X-Ice3) and summers (18s Continental DW). Current winter setup on 17's are smooth as butter (as expected) & super quiet.

 

Losing a wheel weight can cause the vibration, too....