Car & Lifestyle Forum

Kslater

Info:
2003
C4S-Coupe
31K miles
Manual
Never tracked or abused
Recently purchased 2 new rear tires

Noticed when I'm coming off a FWY and making the round house turn my car feels like it's downshifting (but not) and as I straighten out the wheel it goes away. The more I push it (turn) the more I feel the tugging feeling. Noticed this after getting my 2 new rear tires. Car drives perfect around town and on the fwy. Car does feel a little looser since the new tires. Tires are lower rated, ie. price. Thanks. Eli I sent you an email on possible service. Thanks guys!
Garrett.....

CJ_Boxster · Joined: 18 Jan 2007 Posts: 1585 Location: Long Beach, Ca

sounds like your transmission is slipping during hard turns, could be the differential or the transmission.

SPDADCT · Joined: 10 Sep 2008 Posts: 417 Location: Glendale, CA

Kslater wrote: Info:
2003
C4S-Coupe- AWD CAR?
31K miles
Manual
Never tracked or abused
Recently purchased 2 new rear tires- 2 TIRES?

Noticed when I'm coming off a FWY and making the round house turn my car feels like it's downshifting (but not) and as I straighten out the wheel it goes away. The more I push it (turn) the more I feel the tugging feeling. Noticed this after getting my 2 new rear tires. Car drives perfect around town and on the fwy. Car does feel a little looser since the new tires. Tires are lower rated, ie. price. Thanks. Eli I sent you an email on possible service. Thanks guys!
Garrett.....

On a all wheel drive car you need to change all 4 tires at the same time. This is true of all AWD cars, or else the transmission / driveline is trying to compensate for traction per tire.

FastForwardWheels · Posted: Tue Jun 08, 2010 6:32 pm Post subject:

Interesting in-put....

How's your alignment? When is the last time your car was aligned?

-Eli

SPDADCT · Joined: 10 Sep 2008 Posts: 417 Location: Glendale, CA

FYI...

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18

Matching Tires on Four-Wheel Drive and All-Wheel Drive Vehicles

The ability of four-wheel drive and all-wheel drive vehicles to divide the engine's horsepower between its four tires is especially useful on loose or slippery surfaces such as sand and dirt, as well as on wet, icy or snow-covered roads. However it's important to remember that in order to transfer this extra power, the four-wheel drive and all-wheel drive vehicle's driveline mechanically connects the tires so they work in unison.

Four-wheel drive and all-wheel drive vehicles are equipped with additional differentials and/or viscous couplings that are designed to allow momentary differences in wheel speeds when the vehicle turns a corner or temporarily spins a tire. However, if the differentials or viscous couplings are forced to operate 100% of the time because of mismatched tires, they will experience excessive heat and unwarranted wear until they fail.

This necessitates that four-wheel drive and all-wheel drive vehicles use tires that are very closely matched. This is because different diameter tires roll a different number of times each mile as a result of the variations in their circumferences. Tire diameter variations can be caused by accidentally using different sized tires, tires with different tread designs, tires made by different manufacturers, different inflation pressures or even tires worn to different tread depths.

As an example of different tire diameters resulting from tires worn to different tread depths, we'll compare two 225/45R17-sized tires, a new tire with its original tread depth of 10/32-inch and a second tire worn to 8/32-inch of remaining tread depth. The new 225/45R17-sized tire has a calculated diameter of 24.97", a circumference of 78.44" and will roll 835 times each mile. The same tire worn to 8/32-inch of remaining tread depth is calculated to be 1/8" shorter with a diameter of 24.84", have a circumference of 78.04" and will roll 839 times per mile. While the difference of 1/8" in overall diameter doesn't seem excessive, the resulting 4 revolutions per mile difference can place a continuous strain on the tires and vehicle's driveline. Obviously, the greater the difference in the tires' circumferences, the greater the resulting strain.

This makes maintaining the vehicle manufacturer's recommended tire inflation pressures and using "matched" tires on all wheel positions necessary procedures to reduce strain on the vehicle's driveline. Using "matched" tires means all four tires are the same brand, design and tread depth. Mixing tire brands, tread designs and tread depths may cause components in the vehicle's driveline to fail.

Mismatched tires or using improper inflation pressures for all-wheel drive and four-wheel drive vehicles can also result in immediate drivability problems. Some Control Trac equipped vehicles in 4Auto mode may exhibit a shutter on acceleration and/or a noise from the front driveline and transfer case while driving. Some all-wheel drive and four-wheel drive vehicles may exhibit axle windup or binding while driving. Some four-wheel drive vehicles (manual or electronic shift) with a two-wheel drive mode may refuse to shift "on the fly" into 4x4 Auto or 4x4 High at highway speeds.

Kslater · Posted: Wed Jun 09, 2010 1:21 pm Post subject: Thanks

Thank you so much for the insight on my problem. Never would have suspected the 4-wheel system. Hopefully getting my 30K soon. You guys rock!

aren040 · Posted: Fri Jun 11, 2010 1:16 am Post subject:

Yup, that is very true. That is why sometimes AWD guys have to shave new tires to match the others.

-aren