The local rubber merchants ordered and installed P245/70R17-108S tires on my front rims last week.

OEM is P245/70R17-108T BW ALS - a 6-MPH difference. T = 118, S = 112. Yes, in the desert it is easy to find yourself driving smoothly along at 120mph. Odd the way that happens along US-70 in New Mexico.

The rear stock N88 rims are slightly out of true so stay on the rear because of a slight thwup-thwup-thwup-thwup sound when rolling to a stop. The rear rims wear OEM tires - P245/70/17 108T, including one date code 0813, originally the spare rotated into lineup in 2017.

I'm finally thinking of having the aluminum rims rebalanced / trued. Can I more-or-less safely drive with T in front and S in rear? (Assuming I move back into a traditional rotation schedule).

Without being too OCD and anal, there were a few triggers to the install :

1] they ordered the wrong speed rating
2] they installed one of the two tires with its 4520 date code facing inside; at least the tires date code match
3] they rotated T-rated tires to the front and S-rated to the rear, which may be a a no-no, and the gist of this thread
4] they rotated imbalanced rims to the front, though they are the ones who discovered the issue, helping me decide to leave them in the rear
4] they mixed up rim position without having a way to assign its individual TPMS to the correct location - FL FL RR RL
5] simply asking for 40psi on the new tires was not sufficient to actually get it

quote:

Can I more-or-less safely drive with T in front and S in rear?

If all things otherwise are equal then: YES

The question is "Did you get what you ordered?"
If NOT then make them fix it.

Yes

quote:

The question is "Did you get what you ordered?"

Agreed. The speed rating on the tires re safety is inconsequential. They aren't going to blow out because of a letter.

NO NO NO NO.

NEVER put new tires in the front with old tires in the rear. Always the old tires in front. You want to understeer at the limit, not oversteer. When braking you don't want the rears to lock

Many tires places get this wrong because they think the driving wheels should get the newer tires because of traction. It's incompetence at best and approaching gross negligence.

And then you try to explain the reason and you get a blank stare "but driving wheels should get more traction".

For the speed rating it doesn't make a difference as long as you don't exceed the lowest rating. Cars are usually governed to the speed of the factory tire rating, so putting lower rated tires on can put you in an overspeed condition at max speed. Stay below 112 mph in this case.

OK, thanks. I'll get my rims shaved or trued or whatever they do to them. And then put the better tires on the back.

What about on a rear wheel drive car? Put new tires on front or rear?

quote:

Originally posted by maxdog:
What about on a rear wheel drive car? Put new tires on front or rear?

The answer is (generally) always the rear.

The extra traction keeps them from spinning around. YouTube videos show this if you want to get a real explanation.

I understand that you don’t want the rear to swing out. That being said, it also makes sense to have higher traction in the front because that’s where most of the braking force will be. Also for steering. I get the oversteer aspect. But seems like there are many situations where having traction up front would be better.

Perhaps this needs more context of how relatively different the front and rear traction is? Is fairly similar then one way; I’d very different then another way. If somewhat different the what?

How does one rotate tires if the best tires always go on the back? I’d never be able to rotate the tires on my two front wheel drive vehicles if I followed that plan.

I've read of "oversteer" putting higher speed-rated tires in front with lower in the rear.

The S tires are quieter than the T-rated, a bit softer and a hair mushier, I think. But they will take 44psi and the 108 load rating is identical.

quote:

Originally posted by trapper189:
How does one rotate tires if the best tires always go on the back? I’d never be able to rotate the tires on my two front wheel drive vehicles if I followed that plan.

I've wondered about this too. What's the point of rotating tires on a FWD vehicle if the tires w/ more & better tread are supposed to be on the rear wheels? Is it no longer advisable to rotate tires on FWD autos?

quote:

Originally posted by trapper189:

How does one rotate tires if the best tires always go on the back? I’d never be able to rotate the tires on my two front wheel drive vehicles if I followed that plan.

Starting with four new tires, I rotate every 5,000 miles. This keeps the wear pretty even.

Of course this plan falls apart if you have an unexpected replacement of one or two.

Two problems I have with the installation. If the tires are directional I would not want them to change the direction of the mismounted one. In my opinion they should replace it with a new one mounted correctly or offer you a deal on two additional tires to correct their error mounted in the correct orientation.

Another issue is their ordering a lower speed rated tire than was originally on your car without notifying you or having you sign a release to that effect stating that you were informed of this fact. I agree that the difference of six mph is inconsequential as long as the weight rating is the same or greater than originally installed at the factory but in today’s legal atmosphere deviating from factory specs opens the store and possibly the employee open to a multitude of problems.

At minimum today’s “usual” customer having one of those lower rated tires fail regardless of the cause will piss and moan and end up getting one “comped” by the seller if not more. Or decide to sue for “putting their family at risk” as some will contend.

Last dealership I was at had a policy that we would not sell any tire with a speed or weight rating less than was factory installed, no exceptions. One of their few policies that I agreed with even though we had some service advisors trying to sneak one past us on multiple occasions.

quote:

Originally posted by shovelhead:
... we would not sell any tire with a speed or weight rating less than was factory installed,

The 108 weight rating is identical; I believe their data was faulty on speed rating because when the owner rattled off the number, I confirmed it but said it was "T". He seemed surprised. That is almost all they do. The date code turned inside? There is a yellow stripe along one side of the tread. Not sure how they messed that, but you have 18-23 year olds doing grunt work on the coldest windiest day of the year, mistakes happen. At least the tires were fresh from the warehouse; I had the install done 30 minutes after they arrived; they were not sitting out frozen.

Motoring through White Sands it is easy to purr up to 120mph before realizing you are speeding. I'll replace the rears with T when the time comes, and then the fronts in two years or so. And not in the winter.

I may have the rear rims looked at. Shaved or balanced or whatever they do. We'll see. $$$

quote:

Originally posted by egregore:

quote:

The question is "Did you get what you ordered?"

Agreed. The speed rating on the tires re safety is inconsequential. They aren't going to blow out because of a letter.

Perhaps, but it is bad practice to install mis-matched tires on a vehicle. Any tire store worth their salt should know better than this.

quote:

Originally posted by konata88:
I understand that you don’t want the rear to swing out. That being said, it also makes sense to have higher traction in the front because that’s where most of the braking force will be. Also for steering. I get the oversteer aspect. But seems like there are many situations where having traction up front would be better.

Perhaps this needs more context of how relatively different the front and rear traction is? Is fairly similar then one way; I’d very different then another way. If somewhat different the what?

100% of vehicle dynamics engineers agree. The tires capable of generating the most friction should be on the rear axle. 100% of the time when mixing new tires with worn tires. The best drivers in the world can't beat uncontrollable yaw rates.

This message has been edited. Last edited by: Budlum,

quote:

Originally posted by bigdeal:

it is bad practice to install mis-matched tires on a vehicle. Any tire store worth their salt should know better than this.

I bought a used Ford Edge from one of the largest Ford dealers in Centra Florida.

They proudly told me that they had installed four new tires. Yup, they sure did -- two new Goodyears, and two new BF Goodrich tires.

Of course their service department has consistently lied to us, and screwed up just about everything that they have touched, both on this vehicle, and on my wife's Escape.

quote:

Originally posted by Woodman:
Motoring through White Sands it is easy to purr up to 120mph before realizing you are speeding. I'll replace the rears with T when the time comes, and then the fronts in two years or so. And not in the winter.

I may have the rear rims looked at. Shaved or balanced or whatever they do. We'll see. $$$

OK Woodman I have to ask where is this White Sands area in the Mid Atlantic you speak of where you’re zipping along at a buck twenty?
Also, what kind of car do you have??

quote:

Originally posted by Budlum:

quote:

Originally posted by konata88:
I understand that you don’t want the rear to swing out. That being said, it also makes sense to have higher traction in the front because that’s where most of the braking force will be. Also for steering. I get the oversteer aspect. But seems like there are many situations where having traction up front would be better.

Perhaps this needs more context of how relatively different the front and rear traction is? Is fairly similar then one way; I’d very different then another way. If somewhat different the what?

100% of vehicle dynamics engineers agree. The tires capable of generating the most friction should be on the rear axle. 100% of the time when mixing new tires with worn tires. The best drivers in the world can't beat uncontrollable yaw rates.

Let's take an example: Let's say we aren't concerned about hydroplaning. I have two pairs of tires, one that can do the slalom at 0.8g, the other that can do the slalom at 0.85g. Let's say I don't drive aggressively that pushes the g limit of a tire - in other words, there is very little concern I will swing out the backend. If I have a FWD car, why wouldn't I put the 0.85g tires up front, even if they are older? I should expect incrementally better braking and also steering. And still no risk of swinging out the backend.

I'm trying to understand why this rule is absolute and seems to be assuming scenarios that aren't in play.