Q: We live in the Midwest, where potholes and bumpy roads are common. Which tire/wheel combination gives the smoothest ride? Which is less prone to damage? Here are the combinations available on the Volvo XC40 we want: P235/55HR18, P235/50HR19, P235/45HR20.

J.B., Iowa City, Iowa

A: The lower the tire's profile, the rougher it rides. The number after the slash is the aspect ratio denoting the profile. The P235/55HR18 has an aspect ratio of 55. In other words, the height of the tire is 55 percent of the tire's width (the 235). The taller the sidewall and the higher the aspect ratio, the softer the ride. Low-profile tires on big rims are more prone to damage.

Q: We need some guidance on the purchase of a car. We are in our early 80s, and my husband drives a 2006 Maxima and I drive a 2014 Maxima. We take the AARP Senior Safe driving courses every three years, and are committed to driving safely as long possible. I love my 2014 Maxima and thought it would be the last car I would ever buy. The last Senior Safe driving course emphasized the safety features on newer cars, like super cruise control, lane change warnings, automatic braking, etc., none of which we have. Would you recommend the features you think would be useful for older drivers, and even which manufacturer has these features?

S.M., Williamsburg, Va.

A: We don't have the expertise to suggest a particular make or model. There are plenty of other sources such as Consumer Reports that may be helpful. Also visit mycardoeswhat.org to understand each function. If you are excellent drivers, your Nissan Maximas have many more miles left in them. But if you are concerned about your abilities, new cars have lots of safety features that are well worth trading up to. CR rates new cars by advanced safety features, including automatic emergency braking, forward collision control, blind spot warning, rear cross-traffic warning and lane-keeping assist.

Q: I have owned, since new, a 2008 Toyota V-6, which is driven six months of the year in Florida. It has 50,000 miles on it and has been serviced according to the manufacturer's recommendations. I recently had an oil change and tire rotation at a dealer's garage. I could tell by the expression on the service adviser that I was in trouble! The list was long, starting out with "you have a weeping water pump" that needs immediate repair. And as long as we are replacing the pump, the timing chain must be replaced. I was told that if the timing chain broke, it could destroy the engine. I know this is true but pointed out my owner's manual says the chain should be replaced at 90,000 miles. I believe this is a metal chain, so it should last, right?

P.C., Minneapolis

A: A tiny bit of weeping at the water pump vent hole is not uncommon. If it becomes worse, the seal is wearing out and the pump should, indeed, be replaced. Until then, we suggest you add a cooling system leak-stop such as Bar's Leaks. Timing chains are very durable and, unlike belts, usually do not have a replacement schedule.

Bob Weber is a writer, mechanic and ASE-certified Master Automobile Technician.