Well it looks like my less than a week old mazda5 already needs some major work done.
The cyclical “whump whump” noise I was hearing (even from the initial test drive, which the sales person said was just road noise) turns out to be the left front drive axle. Good thing that this is under warranty (Mazda’s Certified Preowned Limited Warranty).
I bought this car used from Wellesley Mazda, and while I question how this drive axle problem was missed in the “150 point inspection” that Mazda Certified Preowned program features, at least for now I am willing to give them a benefit of the doubt. Hopefully this will fix the whump whump noise and also the slight clicking noise I hear when shifting.
I will be bringing in the Mazda5 next Monday and be getting a loaner car for the day. More to come later
It looks like the tire problem has caused many owners to look to alternative size tires from stock (205/50/17)
The change in looks is probably way too subtle for many enthusiast owners, but I went with 215/50-17 Contis for my first set of replacement tires. These are slightly too large in circumference, making the odometer under-record by 1% or so, but have the advantage of making the speedometer ABSOLUTELY accurate, compared to Garmin GPS just taken on 8800 mile road trip back east from Seattle. Plus, they give a slight clearance improvement for driveway nose-scraping, and slightly improve the “economy” aspects of gearing (our is manual, and 2800 rpm 
60 in 5th is plenty high for me)
I recently purchased a used 2009 Mazda5 Sport, with manual transmission. I was curious about the (to me) high RPMs I was experiencing driving it home from the dealer, when I ran across this on edmunds forums:
The gearing is somewhat high, although it feels smooth to me (sometimes I forget to shift up to 5th) on the highway and then notice it when I look at the RPMs). I only saw your question now, so I can give an inexact answer. When I drive around 65, the RPMs are in the low 3000’s (3100 – 3200). Doing the math would get you a bit under 3000 for 60 MPH and a bit under 3500 for 70 MPH. I sure wish it had a 6-speed manual so highway driving could be down around 2500 RPM. My 2000 MPV automatic did around 2700-2800 at 65 MPH and my 2005 MPV with the 3.0 engine was around 2200-2300 at the same speed. Did C4C with the 2000 MPV to get the M5 Sport Manual.
Other things to watch out for:
- Premature tire wear
- Rear strut wear
- Rear sway bar wear
- Road noise due to flattened tires (after being stationary for a long time)
- Replacing OEM tires with more durable quieter tires