Compact spare in the rear

[Ultramaroon]

Originally Posted by mdm

No I am not, difference in the contact patch size should not cause any additional strain on the differential (in normal driving, I am not talking launching or attempting donuts), difference in diameter theoretically could, but I am not sure how if it's only 0.5% or 0.4%.

It's not so bad for an open differential because there is no resistance to different wheel rates.

A Torsen is designed to resist different wheel rates as a function of the input torque. That's why you get the rumble accelerating out of a sharp turn. Put your foot in it hard enough and the axles lock altogether.

Now, with the wheels constantly turning at different rates while you're applying constant torque to keep the car cruising along at 60 MPH, there's a hell of a lot of heat being generated. It's like driving with the hand brake engaged. If that's not reason enough to put the donut up front, consider how well it would handle the the diff lockup in the wet.

Put the donut up front.

[mdm]

Originally Posted by Ultramaroon

while you're applying constant torque to keep the car cruising along at 60 MPH, there's a hell of a lot of heat being generated.

Yeah, I am still not sure why this would be much worse than racing around a road track, where you are in a turn, often a sharp one, most of the time. Or actually around an oval, where you are in a left turn almost all the time (as if you had a donut on your left rear wheel).


I guess the key is what I put on bold above - even the smallest ovals and most winding road tracks will have straights where heat is only dissipated. Also, the manual is about keeping the car in good shape for a long time. No one expects a car that that is raced hard every weekend to last 10 years and 150 kmiles, or its diff to be repaired under warranty.

[kthxbai]

Aside from the wise cracks and jabs, this is why I appreciate this forum...you read the 5-10 pages I didn't read in the manual when I first bought my FRS 4 years ago! This happened on a lunch run after switching into the turn lane (stock tires, rear passenger side). What you can't see is the rest of the bolt, which went all the way down to the rim leaving a mild dent. Tires only had 8k on them.

I did not know the spare had to go on the front, but after getting the spare on I drove about 8 miles total to my local Tires Plus. They wanted $180 per Michelin Primacy HP and had to special order them. The rep stated they had some Bridgestones with "similar tread" if we couldn't wait, so I made the mistake of getting the pair of Bridgestones because we were heading out on a small trip the next day. It was the middle of summer and I felt like I was driving on ice the entire trip.

Ended up buying a full set of used Michelin Primacy HP's from a member here for $100, tires only had ~2k on them, and all was well again.



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[Ultramaroon]

Originally Posted by mdm

Yeah, I am still not sure why this would be much worse than racing around a road track, where you are in a turn, often a sharp one, most of the time. Or actually around an oval, where you are in a left turn almost all the time (as if you had a donut on your left rear wheel).


I guess the key is what I put on bold above - even the smallest ovals and most winding road tracks will have straights where heat is only dissipated. Also, the manual is about keeping the car in good shape for a long time. No one expects a car that that is raced hard every weekend to last 10 years and 150 kmiles, or its diff to be repaired under warranty.

It's worse because it's constant. There's no opportunity for the diff to cool down. Would you ride your brakes just a little bit all the time because it's not really that bad for the car?

Just because, the manual is written for liability doesn't keep it from being a good idea to follow it. This thing is NOT a racecar and 99.95% of the owners don't know how, or want to rebuild the diff.

I get what you're saying but it's still a good idea to spend the extra 5 minutes swapping wheels.