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Auto Doctor: Reducing tire size can smooth rides

Swapping out larger tires for smaller ones on

Swapping out larger tires for smaller ones on cars like the 2009 Toyota Venza (pictured above) can make for a smoother ride. Photo Credit: Toyota

Dear Doctor: I own a Toyota Venza with a rough and harsh ride. The tire size is P245/55R19 Bridgestone Duller. Will changing out from the 19-inch tire size make the ride any better? -- Rob

Dear Rob: When the tire size is changed to a larger aspect ratio 55 series to 60 series there is more flexibility between the tire and rim, which equals a smoother ride. You can change the tire size, keeping in mind that no more than one-quarter inch in overall diameter is recommended. I have downsized from a 19-inch to 18-inch tire size while retaining the same outside diameter. As for the tire brand you choose, make sure the tire is not aggressive and has a summer-type tread pattern.

Dear Doctor: After driving for long distances with a/c on in our 2004 Infiniti I35, the passenger side carpeting becomes soaking wet. The drains are clear and the a/c drains when the motor is running and standing still. We have been to the dealer on many occasions and since they can't replicate the problem they can't rectify the problem. Your advice is appreciated. -- Gloria and Ed

Dear Gloria and Ed: I see this problem on many vehicles where the a/c drain is clear. The problem is the actual drain tube is too short and the water drips back into the passenger compartment. I looked on our Identifix web site and found the quick and easy repair is to add a 4-inch spark plug wire boot onto the drain. In some cases, the seal between the heater box and firewall also needs to be resealed with silicone. has perfect view of the heater box and drain.

Dear Doctor: I own a 2002 Buick Century with only 80,000 miles. The shift indicator and odometer stopped illuminating. I went to the dealer and they said I need to replace the dash cluster at a cost of $500. Is there any other solution? -- Vincent

Dear Vincent: We work on a lot of dash cluster failures. We remove and send out the dash clusters to a company in Taunton, Mass., called BBA remanufacturing where they rebuild the dash cluster for one-third the price of what GM charges. There may be a local company in your area if you research it that also can rebuild your dash.

Dear Doctor: I have a 1965 Dodge Coronet with a stock charging system. The problem I'm having is an over-voltage charging system (15 to 16.5-plus volts). Also, the voltage level increases with the engine rpms. I tried other voltage regulators with no change. Do you have any advice? -- Ken

Dear Ken: In older vehicles the alternator's charging rate is controlled by the voltage regulator through the field circuit. The high voltage would indicate a wiring fault (internal alternator problem). I suggest you take the alternator and regulator to the local rebuilder and let them test both. You can also change over to an updated single wire internal regulator alternator. The older alternators with the external regulators had low amperage out output by today's standards.

Dear Doctor: Two years ago I bought a 2004 Dodge Viper equipped with an aftermarket Corsa Exhaust System. The exhaust works fine, but it's too loud. Is there any way of toning down the sound? I know that motorcycles use baffles. Is this a possibility? -- Eddie

Dear Eddie: The Corsa performance exhaust is in my opinion the best aftermarket exhaust for both auto and marine applications. I would first call Corsa and ask them if they have or can make a quieter muffler or add another sound baffle. Another choice is the addition of a straight through resonator. The large V-10 engine does not like restrictions in the exhaust system. The motorcycle baffles would be too restrictive. There is always the use of the factory muffler replacement. 

Junior Damato is an ASE-certified Master Technician. Email questions to

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