Not having much luck in the tires and wheels sections, and dieselers know all ('cuase we're pretty anal about our cars.)

How much of an issue could this cuase? Let's say using two 195/70/14's and two 205/70/14's. Yes, these tires are about an inch different in diameter, but that is only 2% different.

Motives are unimportant, just curious if there would be any adverse effects. I'm thinking over or under steer, or wandering. Same sized tires would stay on same axle, no mix and matching on the rear for example.

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B
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1983 300SD

As long as you use the same size on each end (Exmaple: 195 on the front, 205 on the back), you will be fine. The car will look funny, but I doubt it will hurt anything.

I doubt it would have any serious affect. It would change the steering geometry, but it's probably no worse than having sagging springs in the back.

Put the bigger tires on the rear. Difference may be smaller than you think. Make a mark on one tire entending onto the ground then roll car one revolution of the tire until mark is once again touching ground. Measure distance traveled. Now do that with the other tire and get its distance traveled. Now compare the two numbers. Only like a 2.5% difference. Heck, treadwear can give you close to that much difference.

bbeardb,

I do different size tires front to rear all the time with no problems. Some of the new "hotrod" cars come standard with larger tires on the rear.

P E H

I calculate a 14mm difference in diameter, or approx 1/2 inch. That's only a 7mm difference in radius. There is that much difference between a new and worn tire of the same size. I doubt that there would be any noticible difference.

The tires that provide the best traction should go on the rear.

the tires with the bet traction SHOULD ALWAYS go on the front!
have you ever tried to steer or stop a car when the front tires are bald? um, bad things happen.
the back may slip around a little, or make it a little harder to move in wet weather, front and you crash or die with bald tires in wet weather.

Just make sure they are front and rear.

With the larger AMG and Brabus wheels its pretty commen to have a wider slightly larger tire and wheel for the rear. Looks better.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Just an example, I have 205/60R15's on the front and 195/70R14's on the rear.
Like vstech said, best tires on the front.

I (and most car manufacturers) disagree. You want the car to understeer not oversteer. If the tires witht he best traction are on front, the car will oversteer. Most carmakers build in a little understeer, just to keep people out of trouble. If your tires are so bad they have no tread, stay off the road.
Remember:
Cars that understeer go thru the fence nose first. Cars that oversteer go thru the fence butt first.

BobK is right. Good tire installers will not put the best tires on the front, citing some insurance rules or something. NHTSA probably
BTDT

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Can you provide a single credible reference to support that position? It seems that every time this topic comes up, a truckload of shadetree engineers come forward supporting this notion. But I don't think you will find any support from the tire manufacturers.

Here is an interesting acticle:
http://www.canadiandriver.com/articles/pw/laurens.htm

As long as your car is pre ABS it should be okay for such a small diff front to rear.
Good tires in back....you can steer a bad/bald/flat front directly. The rear can only be steered indirectly....I think most firestone/explorer flips were caused by rear failures.

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82 300D....went to MB heaven
90 350 SDL....excercising con rods

Tire tread being equal, the biggest/widest best traction tires should of course go on the rear. but not knowing exactly what the OP was asking for, just make sure that defective or sub par tires go on the rear. I have driven several million miles, and I have had traction problems with worn tires, I have had tires blow out on the road at speed. TRUST ME, rear problems are much easier to overcome than front problems.

I would really like to do that. But it would require that I ignore a ton of scientific evidence and rely entirely on supposition.

You have not convinced me yet. But I'm still listening. Can you cite a single credible bit of documentation that support your "feelings?"