Rear end Shudder?

Ok Guys,..Heres my dilemma. 2012 DCLB Sport 4X4
My truck shudders when braking. Not front end,.more underneath or rear. Not violent,..but noticeable.
Has new brakes with new rear drums installed by toyota 3 months ago when I got it CPO.
Just brought it to dealer with my winter tires mounted on Tundra 17" rims to them for diagnosis. They said because the truck came with 18" wheels originally that they cannot diagnose it properly, even though the tires are a factory size for the 17" Rim that most tacomas came with. Any ideas out there because Im ready to have a stroke.
The tires that the truck came Cert Pre-Owned with are 32" cooper discoverers. I told the Tech that Rim diameter should have nothing to do with it, but they wouldnt hear it.

 

If rim size was the problem there wouldnt be 1000's of people buying different size rims...they might have got brake fluid on the brake shoes and thats whats causing your shudder... the shoes and drums need to be taken off, cleaned and maybe even scrub the shoes if theres any type of oil on the shoes.

 

I was gonna ask the same question today. Mine is an 07 TRD. Shudders somewhere around the 40mph range then goes away by 20. I was suspecting the rear brakes because I've never changed them. Bought them a couple years ago but didn't have time that day after doing the front and never got back to it.

I also thought maybe it was related to the bad springs, causing some hop, but I don't think mine are cracked. Not as far as I can tell, at least.

 

Shudder has been going on through 2 visits to the dealer, so Im sure its not a brake fluid thing. Plus they even put Brand new rear drums on it at the last visit.
UPDATE - Just got back from picking it up. Slip says Customer has incorrect tire size on vehicle. The tires are 265-65/17 on it. Factory size tire for a 17" rim.
I hate being fed BS from people.