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Discussion Starter · #1 ·
Hello all,

I daily drive a stock 2017 WRX with stock 18x8.5 rims and stock 245/40 R18 tires. I'm looking to swap the tires out for a set of Pilot Sport A/S 3+.

I'll be keeping the stock rims since I only need one set for this setup. The only question remaining is about size and fitment.

I'm looking at two options here, stock or staggered.

Stock:
F: 245/40 ZR18 97Y - Diameter: 25.7"
R: 245/40 ZR18 97Y - Diameter: 25.7"

Staggered:
F: 225/45 ZR18 95Y - Diameter: 25.9"
R: 255/40 ZR18 95Y - Diameter: 26"

This is my daily driver and I don't plan to do any other modifications. I'm considering a staggered wheel sizes for better traction and cornering, but having never done this before, I am not sure how this will look or perform.

Any input is greatly appreciated.
 

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Νεκρέ, καλώς όρισες. Φοβάμαι ότι αν τα ελαστικά δεν έχουν την ίδια διάμετρο, το κεντρικό διαφορικό διαφορικό είναι που θα νεκρώσει...

Welcome Nekros, I fear that if the tyres are not of the same diameter, it's the central differential that will go necrotic...

Staggering would make some sense if you put the wider tyres in the front rather than the rear, but honestly I'd not do this at all. I'd keep the same tyres front and rear. The manual states the maximum ΔΦ between any two tyres to keep the diffs safe.

I'd say no go on staggering. Keep it the same F/R.
 

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Discussion Starter · #3 ·
Would a difference of 0.1 inch on diameter put significant stress on a clutch-operated center diff?
 

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That's 2,5mm. Check the manual to see if it's "tolerated" but ultimately, I don't see what you are trying to accomplish. You're narrowing the front and adding to the car's problems (understeer). You're also preventing yourself from rotations so your wear will increase (and with it, the 2,5mm of ΔΦ may change for all we know).

If the wider stuff fits all around, why not just use the same size front and back? See if others have fitted 255s in the nose and go from there.
 

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Would a difference of 0.1 inch on diameter put significant stress on a clutch-operated center diff?
Your center differential is not clutch operated.

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I would advise against this. The awd system basically negates any benefit to staggered tires as it is a 50/50 system. It doesn't work like more performance oriented systems where the majority of the power is routed to the rear tires.

Anyway. The tires need to be within 1/4" circumference. What you listed is not within that margin so the short and long answer is no, you can't run them.
 

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Discussion Starter · #8 ·
Thanks for the answers, but it seems I have not provided adequate information to describe my situation.

What I am hoping to achieve is tighter steering in the front and better grip in the back.

Also, this vehicle is equipped with Active Torque Split, which uses a 60:40 front and rear split by default.
 

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It seems your mind is made up. So have at it. Again what you listed is outside of Subarus specs. So the answer again is no, you shouldn't.

It's an extremely nose heavy vehicle. This setup you speak of will likely not have any appreciable change in the handling characteristics of the vehicle.
 

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Discussion Starter · #10 · (Edited)
Not so much made. I just want to gather as much information as possible before I make a commitment.

I had a good long dig through the owner's manual and did not find anything concerning the center diff or tolerances. As far as tires go, the manual clearly states that tires must be purchased from the dealer, in stock specification, down to the speed rating.
 

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What I am hoping to achieve is tighter steering in the front
Yet you're selecting narrower tyres up front. The car understeers already.
 

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So you have a CVT?

A lot of this doesn't make sense to me. You want to have tighter steering and feel so you wish to swap out for All Season tires?

At least in the past, the WRX owner manual specifically advises against staggered fitment. The the fact that we are even continuing this conversation means that we are ignoring this point. Very well. If you want more steering feel and front end grip AND wish to ignore Subaru recommendation, you should be running the wider tire in the front.

I'm also not aware of any performance Subaru that runs a 60:40 torque split as the standard Impreza. MT6 WRX is 50:50 with the crappy VLSD, CVT is 45:55 with the much better active system, and the WRX STI is 41:59.

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I run 255/35/18 PSS in the summer and they are fine up front. No rubbing at all. I doubt the extra 5mm on the profile is going to make a difference just run the wider tire all around
 

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Discussion Starter · #14 ·
So you have a CVT?

A lot of this doesn't make sense to me. You want to have tighter steering and feel so you wish to swap out for All Season tires?

At least in the past, the WRX owner manual specifically advises against staggered fitment. The the fact that we are even continuing this conversation means that we are ignoring this point. Very well. If you want more steering feel and front end grip AND wish to ignore Subaru recommendation, you should be running the wider tire in the front.

I'm also not aware of any performance Subaru that runs a 60:40 torque split as the standard Impreza. MT6 WRX is 50:50 with the crappy VLSD, CVT is 45:55 with the much better active system, and the WRX STI is 41:59.

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You are overthinking it. The type of tires are irrelevant. The point of my original post is not to figure out how to give my car more power.

I'm trying figure out what kind of damage to expect. I have no doubt that it will blow up the diff, but when? A week? A year? Maybe 10?

If you don't know, no need to get angry. Just say you don't know.

And yes, I have a CVT.

Can I ask where you get these numbers from?
 

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Discussion Starter · #15 ·
I run 255/35/18 PSS in the summer and they are fine up front. No rubbing at all. I doubt the extra 5mm on the profile is going to make a difference just run the wider tire all around
I really want to avoid dropping my ride height if I can help it. I like to go all sorts of places in this car, faraway places. I've already run into high-speed clearance issues and would like to avoid anymore encounters with the ground.

I'd much rather use 255/40/18, assuming it would fit.
 

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What exactly is your goal? What is your car doing or not doing that you want to change? What exactly are you doing at high speed to be dragging the tub?
 

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You are overthinking it. The type of tires are irrelevant. The point of my original post is not to figure out how to give my car more power.

I'm trying figure out what kind of damage to expect. I have no doubt that it will blow up the diff, but when? A week? A year? Maybe 10?

If you don't know, no need to get angry. Just say you don't know.

And yes, I have a CVT.

Can I ask where you get these numbers from?
There is no anger here, but a very serious miscommunication.

The simple answer is: don't do it.

Who is discussing "giving the car more power?" Do you not understand what a torque split means?

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True that. I'll keep searching.
You need to know what you are searching for. You are looking for a result, but asking about doing something that gives you the opposite result.

I'll bet you just need a good set of tires and an alignment.
 
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