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235/40 vs 225/45 -- 17x8" -- summer high perf -- signif handling improv?


caramall2

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Buying Dunlop Z1. Kind of chickening out on 245 as several say I'll have rubbing issues--definitely don't want that (I'm on Zeals, lowered about 3/4"). I've read tons of threads on this...mixed reviews. So, my next question is:

 

Do you think 235/40 is a good adv handling wise over 225/45? I like the extra protection of the higher side wall, but would like to try some wider tires (running 225/45 summer high perf now).

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I researched this issue long and deep. I decided to stick to 225/45/17 so to avoid any rubbing/fender rolling. I also found comments by people on this forum who tried both and said 245 are great for autox, but 225 are better on the street.

 

Since my cars spend majority of their time on the street I stayed with 225/45/17. Plus I could not find sensibly priced 17x8 wheels I'd like.

 

Remember that wagons leave slightly less outboard clearance in the rear, so wheel/tire combo that doesn't rub on sedan may rub on wagon.

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aside from the fender clearance issue, why would 225/45/17 be better than 245/40/17 on the street? the total sidewall heights are within 3mm of each other, and the 245/40/17 is closer to the stock 215/45/17 tire diameter. I say if you can make it fit, the wider the tire, the better, unless its in the snow ;)
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I am not sure about the wider always the better. Seems like steering response may suffer. Added weight is not a plus either.

 

Wider is better when cornering. With sticky 225/45/17 it's not quite easy to reach their limit of adhesion on the street anyway. I try, but usually it's beyond what most would call crazy ;):lol:

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steeing response improves since there would be more front end grip due to more tire on the ground. steering weight at low speeds would increase alittle for obvious reasons.

 

you arent trying hard enough then. ;) i can get to the limit often if i want, and im on re-01rs 245 wide on the street.

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I'm glad I found this as I've been running over this same basic subject in my head lately. I've been having dreams of summer wheels soon and am not quite sure what to do. I live in Potholeville, AKA, Pennsylvania. The extra sidewall of 225/45 plus tire pricing, availability, and weight seems the best choice to me. I'm not even close to an aggressive driver and when I do do it, I should have good enough rubber to not need the extra 20mm of width. Add in cheaper wheels and no issues with rubbing and I'm happy. Now a question though. I see a few people on here run a 235/40 on a 17x7.5. How does that size fit in with sidewall protection, rubbing, and the possible need for rolling fenders?
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Thanks guys. Whitetiger, what's your suspension again (coilovers, springs, etc)?

 

 

tien flex coilovers, heavily lowered for a street car. but witht he rght offset rim, 245 wider tires fit with no issue. not sure about the differences in fender clearance with a wagon. Unclemat would know more about that, but on a sedan, no issues.

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caramall2: what are your wheel offsets? This may dictate if you're going to rub or not.

 

Last season, I ran a 235/40/17 (Toyo RA-1) with a 17x8 45mm offset (Enkei RPF1) with no rubbing. But this was for autox and track days. My street tires are 225 on 8" rims.

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Happy. Sticky like glue and don't get greasy on the track. On the stiffer side, but not too stiff. Wear surprisingly slowly for the abuse they went thru. Kinda noisy.
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As has been pointed out....bigger tires means:

 

1. More rotating mass (typically)

2. More stress on the steering/suspension

3. Can reduce braking capabilities

3. Less snow traction vs. equal tire with smaller width

4. Less resistance to hydroplaning.

5. More road noise (agian, vs. an equal tire with smaller width)

 

I'm not saying it's a bad idea. Just things to weigh when you consider this.

 

Joe

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As has been pointed out....bigger tires means:

 

1. More rotating mass (typically)

2. More stress on the steering/suspension

3. Can reduce braking capabilities

3. Less snow traction vs. equal tire with smaller width

4. Less resistance to hydroplaning.

5. More road noise (agian, vs. an equal tire with smaller width)

 

I'm not saying it's a bad idea. Just things to weigh when you consider this.

 

Joe

 

1. if you find a lighter wheel, you can save mass even thouigh the tire is wider. my setup is like this, lighter than stock

2. in motion, a lighter wheel/tire combo will have less tress on the steering. although one can argure that more grip in general has more stress ont he car, but that is to be expected, and is in essence the whole point of a wider tires. better grip.

3. a lighter wheel/tire comber with more rubber on the ground due to a wider tire will improve braking, not make it worse.

3(again). agreed. this is why its nice to have dedicated winter and summer setups. ;)

4.the right tire selection will make he difference between a narrow tire and wide tires very little in terms of hydroplaning threshold

5. agreed, but if you are compaing the same exact tire, just 2 different widths, the difference in road noies will be almost nothing unless you are comparing a 195 wide tire to a 295 tire.

 

 

the real world variables that would cause someone not to get a wider tire are cost and fitment.

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1. A tire represents the greatest rotating mass in the drivetrain, due to it's distance from the hub. A lightweight wheel will not overcome a heavier tire, unless you are a physics major and actually do the calculation and i'm wrong.

2. A heavier tire will put more stress on the suspension because it needs to deal with more weight. It's probably granny smith apples vs. roma apples. I'll retract what I said about steering, since it's pretty much all argumentative.

3. I won't argue that in a 60-0 test that a wider tire could offer benefits. What I have observed in my transition from an 18 pound tire to a 25 pound tire (same tire size), is that braking effort is significantly increased. Take that for what it's worth.

4. Like I said, examining the same tire. I'm not saying it's going to be the difference between cruising through 3 feet of water or going waterskiing; just that it is a difference to consider.

5. Same here.

 

6. I'll add one: A wider tire means you have increased the frontal area of your vehicle. You will meet more wind resistance.

 

:)

 

Joe

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Just to bring the discussion back to the original post:

 

Do you think 235/40 is a good adv handling wise over 225/45? I like the extra protection of the higher side wall, but would like to try some wider tires (running 225/45 summer high perf now).

 

I don't think you will notice much difference between the two...

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Thanks again all. Interestingly, for cross-section (not sure what contact patch width is) for Z1:

 

225/45/17 (7.5" rim) -- 8.9

235/40/17 (8.5" rim) -- 9.6

 

May have more to do with the rim width (1" difference) than the tire width...not sure.

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Oh, I have 48 mm offset.

 

You'll be fine with either:

225/45/17

235/40/17

(if anything, remove the rear rubber strip around the wheel well to give you a little more room)

 

Now the choice is really up to you and what you want to do.

 

I don't think you'll notice a difference in handling (especially on the streets) but you will notice the gearing difference.

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You'll be fine with either:

225/45/17

235/45/17

235/40/17

or

245/40/17 (if anything, remove the rear rubber strip around the wheel well to give you a little more room)

 

Now the choice is really up to you and what you want to do.

 

I have 235/40/17s on 48 mm positive offset.

 

I had rubbing with the rubber strip on my car, now with the strip taken off I do not rub.

 

What makes you think that 245/40/17s will now fit? Especially on a wagon? And especially with tires known to have a wider then normal profile?:rolleyes:

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