Tire sizing
 

Hi all,

In need of some advice with tires. I’m wondering if I can run 255/40 R17 (semis) just on the rears? I wouldn’t be able to do them all around bcuz it will scrub on the front. Or should I go for the current tire size all around with Michelin pilot sports?

My specs are:
Rims are 17x9 +35
Current tyres are 235/45 R17


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Is this car exclusively driven on the street, or does it see any track time?

I would suggest running a 245/40-17 square setup so you can continue to rotate, and just dial in negative camber to ensure they clear the fenders. Assuming you are still on stock suspension and do not want to invest in coilovers just yet, you can install camber bolts to get the camber you need up front. The ET35 offset gives you plenty of inner strut clearance to work with, and the 245's will provide you with plenty of grip no matter how you enjoy the car.

- Ryan

This car is turbocharged and is only driven on the street. I’m sitting on pedders coilovers but the front will scrub if I go 245 so yes that’s a great suggestion! ill get the camber bolts and see how I go


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I dont think it should rub/scrub with 245/40 tires. Maybe you need to run some more camber to tuck the tire in.

I'm running the same specs for wheels and 245/40/17 tires on coilovers.

Currently with zero fitment/rubbing issues. It may depend on your ride height and camber setup.

You may need to alter if you're going for a track setup or want to be a stanceboi.

Not the OP, but when you got that size. Is the handling and turning feel duller? Thats what Ive read people say about that when they go 9” tires. Does the turning feel any different like what ive read about?

My setup will be +400whp. Id like some traction but not change how the car feels when youre going round bends/corners.

If you have the same wheel specs as me I’d say go 245/40 or 245/45 over 255/40 as I’ve heard the Speedo is less accurate and it is slugging in corners. I decided to stay at 235/45 R17 and just got some yoko AD08R for the rears instead. I am turbocharged sitting at 316hp and I’m gripping well in both wet and dry conditions.


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I'd say the handling is better but the turning feel does feel "duller" imo.
With the wider tires, I have more confidence making tighter corners than I did on stock tires/specs.

Can also confirm that over 225 width starts to feel duller than a narrow tire.

That's unfortunate. I love the look of widebois but I hope I don't regret it because of downgraded feel.

It's still pleasant to drive, just slightly less sharp. It still handles just as well.
I went from 200tw tires to 240tw, so maybe my complaint lies there?

I never noticed any "dulling" of steering responsiveness going to lightweight 9" wheels with good (RE71R) 245/40-17 tires. If anything, ightweight 9" wheels with good 245s should should generate more lateral grip per degree of slip angle and hence feel *more* responsive.

I just switched from 225 RS4s on 17x8 +35 Rota Grids to 255 RT615K+s on 17x9 +35 RPF1s and they definitely feel very different. There's less sharpness/directness to the inputs but it doesn't necessarily feel bad. The car actually seems to want to rotate more on the 255s, which is the opposite of what I expected. I'm on TRD springs and running 3.3F/2R for camber and -0.10F/0R for toe. I was worried about rubbing but have no issues at all.

Won't really know how I feel about the setup until I track it this Saturday. I got the wheels intending to run 245s, but the 255s they came with have a lot of tread left so I'm gonna give them a shot first.

All of what you are feeling can be attributed to the change in tire/compound.

In my opinion any dullness or lazy initial response is probably more of a function of a few extra pounds gained between a wider wheel and tire combo vs anything to do with the extra width. Hard to tell without an apples to apples comparison (weight, compound etc.).

In this instance the wider setup actually still manages to be lighter. 43lbs (19+24) vs 42lbs (16+26)...which says a lot about why so many people are running RPF1s.

Could definitely be down to differences between the tires themselves, which I'll have a better understanding of whenever I get a fresh set of RS4s on them. I have no prior experience on the Falkens.

I am still inclined to believe that an increase in width as dramatic as 225-255 by itself would have an impact on the steering feel, and my track buddies that I've spoken with about it have had the same experience.

It's not just the tire itself or the weight of the wheel/tire combo. You're changing wheel and tire width along with wheel offset compared to stock, so it's probably also increasing scrub radius which increases the feeling of effort and feedback through the steering.

To me, the car doesn't feel as playful or light on its feet with wider wheels and tires. Not necessarily better or worse, good or bad. It just depends on your use case.

I wonder if there is a definitive answer to this. For sure the tire compound and build should make a huge difference by themselves (well fitted tires with strong sidewalls vs meaty tires with squishy sidewalls), but of course total rotating mass/weight will affect feel too. According to my spreasheet, the stock PP wheels and tires are 41 lbs total per corner, while my TC105s 17x9 with 245/40/17 V12 evo2s are 39 lbs; I wonder how different or similar feel will be. guess I'll report once I have time to mount them.

Wider tires can give you more grip but not feel any better. Feeling and grip may not go hand in hand. For example when you get wide tires on the front wheels it is so much easier for the car to tramline, especially on highways that have heavy trucks that form those depressions. I can feel the difference in tramlining for different summer tires. This is why a dedicated track or auto setup is better than trying to do both track and DD. A setup that gives great grip at a track could feel crappy on our lovely local roads.

I live just over the border in NY and on my commute to NJ I can feel so many bumps and cracks in NY, as soon as I cross the border onto the garden state parkway it’s nice and smooth. NY roads are pretty bad. Everyone claims it’s salt and winter, but I drove in Maine and the roads were great compared to here.