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You're right but you don't have to be a dick about it...or maybe you do.
Not being a dick.. just reinterating WHY ( since the same question keeps being asked ), he shop is wanting to do it their way.. that is the train of thought converning tire/vehicle dynamics/liability...
Dumbing it down just means editing out the long basic VD talk and tire srvices SOPs regarding liability issues to explain more thoroughly.. your welcome..D
GGGooollllyyyyy Martha but it's just SOOOOO easy to steer with NO traction at the front , golly that works just SSOOOOOO well.
YEAH come back at me about this one , oh please do since I've got enough laps in the rain in various tracks around this country to *know* what works at speed in the wet , not just " what I was told".......
Now hows that for " dumbing it down"?....BOY.
Hey Mc Snappy, I was just speaking of the SHOPS point of view... Which IS the same as manufacturers, AGAIN, the reason why virtually EVERY car has understeer as the inherant dynamic limit... except certain niche models.. and Im probally not someone you want to trade barbs with about "track laps" unless you've got plenty of real checkered flags AND many "laps" as a professional tire tester under your belt so you can just jump off that high horse right now, as all I was doing was answering the question as asked about from the shops point of view.. happy motoring.. track day boy..
It might be a liability issue. They're afraid somebody will sue them if they have a wreck after tires have been installed in a way that some jury might decide was not in compliance with some industry standard. In these litigious time, not an unreasonable expectation. Like everywhere nowadays, their legal affairs department has the final word on making the rules.
My step daughter once took her car to a chain muffler shop to have the brakes checked, and they said it would be illegal to let her drive the car off the lot with those brakes. We went back after dark and got the car with a spare key. Luckily, they had put the wheels back on and pulled it out onto the lot. We should have then reported the car stolen from their lot, and let their legal affairs department try to wiggle off that hook.
"Intuition suggests that since the front tires wore out first and because there is still about half of the tread remaining on the rear tires, the new tires should be installed on the front axle. ... However in this case, intuition isn't right...and following it can be downright dangerous.
"When tires are replaced in pairs in situations like these, the new tires should always be installed on the rear axle and the partially worn tires moved to the front. New tires on the rear axle help the driver more easily maintain control on wet roads since deeper treaded tires are better at resisting hydroplaning.
"Hydroplaning occurs when the tire cannot process enough water through its tread design to maintain effective contact with the road. ...
"Exactly when hydroplaning occurs is the result of a combination of elements including water depth, vehicle weight and speed, as well as tire size, air pressure, tread design and tread depth. ...
"If the front tires have significantly less tread depth than the rear tires, the front tires will begin to hydroplane and lose traction on wet roads before the rear tires. While this will cause the vehicle to understeer, understeer is relatively easy to control because releasing the gas pedal will slow the vehicle and help the driver maintain control.
"However, if the front tires have significantly more tread depth than the rear tires, the rear tires will begin to hydroplane and lose traction on wet roads before the fronts. This will cause the vehicle to oversteer (the vehicle will want to spin). Oversteer is far more difficult to control and in addition to the initial distress felt when the rear of the car starts sliding, quickly releasing the gas pedal in an attempt to slow down may actually make it more difficult for the driver to regain control, possibly causing a complete spinout.
"Members of Tire Rack team had the chance to experience this phenomenon at Michelin's Laurens Proving Grounds. Participants were allowed to drive around a large radius, wet curve in vehicles fitted with tires of different tread depths -- one vehicle with new tires on the rear and half-worn tires on the front and the other with the new tires in the front and half-worn tires on the rear.
"It didn't take long for this hands-on experience to confirm that the "proving grounds" name for the facility was correct. The ability to sense and control predictable understeer with the new tires on the rear and the helplessness in trying to control the surprising oversteer with the new tires on the front was emphatically proven.
"And even though our drivers had the advantage of knowing we were going to be challenged to maintain car control, spinouts became common during our laps in the car with the new tires on the front and the worn tires on the rear. Michelin advises us that almost every driver spins out at least once when participating in this demonstration!"
Huh.. imagine that, EXACTLY as I been saying since page 1, except I dont do a basic VD talk like posted above for free. Choke on that ole "Goooolllyyy Martha/Ronin" and the rest that jumped down my throat when I explained the same from the shops liability point of view and was called a "dick" for it..
The VD reasoning above is the SAME reason virtually every steet car built has understeer built it as the prominant handling dynamic. Safer, being easier to recognize and easier to fix than oversteer for the general public. Its easier for the 99% to avoid something headed staight at it instead of headed towards it backwards. Its not rocket science.
...Ever do any dirt-tracking? Doesn't matter what really the dynamics are the same from mini-stocks to sprinters , a skaty front end is slow laptimes , just like terrible traction off the corner due to the wrong stagger etc. is SLOW.
Nope. Everyone know's, dirt's for plantin' taters.
"Replacing Fewer Than Four Tires: Whether your vehicle is front-, rear-, or all-wheel drive, if your rear tires lose traction because of hydroplaning on a wet road, oversteer skidding condition may result and lead to loss of
control, particularly in a turn. Generally, new tires provide
increased resistance to hydroplaning due to their full tread
depth. With the new tires on the rear, the oversteer skidding
condition may be more easily avoided. Therefore, if
replacing only one or two tires at a time:
• Two new tires should be placed on the rear axle.
• One new tire should be paired with another tire from the
vehicle with the deepest tread depth, and then both should
be placed on the rear axle."
"Replacing Fewer Than Four Tires: Whether your vehicle is front-, rear-, or all-wheel drive, if your rear tires lose traction because of hydroplaning on a wet road, oversteer skidding condition may result and lead to loss of
control, particularly in a turn. Generally, new tires provide
increased resistance to hydroplaning due to their full tread
depth. With the new tires on the rear, the oversteer skidding
condition may be more easily avoided. Therefore, if
replacing only one or two tires at a time:
• Two new tires should be placed on the rear axle.
• One new tire should be paired with another tire from the
vehicle with the deepest tread depth, and then both should
be placed on the rear axle."
Yes This. Because VD is the same, fwd, rwd ,awd, EXCEPT of course for loss of traction because of TOO much power added, re: power oversteer rwd, power understeer fwd etc etc.. still weight/load always goes to the front jumping off power or slowing, always goes to rear adding power/releasing brake pressure... And the TOT being that on the street understeer ie. sliding towards peril FORWARDS instead of BACKWARDS is safer and easier recognized and fixed by the general driving public. Those backyard dirttrackers might not agree, BUT that doesn't matter as the reality is that auto and tire manufacters operate under this standard.
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New on rear per mfr.
