16" vs 17" vs 18" wheels with the same Max Performance tires comparisons?

[Heather]

This question has never been answered anywhere. The question of the advantages of 17" wheels over 16" wheels going from the stock Re92's to really good tires on 17" wheels has been answered many times. That is NOT my question.

My question is: What are the advantages of going from 205/55/16 Max performance tires on stock wheels to 225/45/17 with the SAME Max performance tires on 17" wheels of EQUAL weights? The weights of the tires are the same and the weights of the wheels are the same, so unsprung weight is not an issue here. Are there any additional performance/handling gains using 18" wheels with 225/40/18 tires?

Here are the advantages as I know them so far when going to larger wheels:
1) You can someday add bigger brakes to the 17" wheels.
2) Sidewall stiffness for less deflection in a corner and this means lower slip angles and a higher limit of adhesion.
3) Improves brake cooling.
4) More feel of the road through the wheel and a tighter steering response.

Anything else? What about handling improvements? What about the feel of the car with larger wheels? I am so close to buying 17" wheels (OEM UK) and the same tires I have now- Michelin Pilot Sport A/S tires, but I want to be able to justify the $2,000 dollars it will take to get there. Is there really any justification for this at all? If so please post it here
Heather

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[Heather]

After much investigation and research on this topic I have only one conclusion I can make: It is not worth $2,000 to up size my wheels and to gain 8 pounds unsprung weight in the process!

I got a reply from the e-mail I sent to Michelin on tire weights for the A/S tires:
The Pilot Sport A/S in a 225/45ZR17 weighs 23.11 lbs.;
225/50ZR16 weighs 24.48 lbs; 205/55ZR16 weighs 22.27 lbs.

I then call the Tire Rack and they verified these weights to the exact figures.

I have it all, the best tires with the lowest weight (22.27 pounds) with the lightest wheels at 16.5 pounds. I am sticking with my 205/55/16 wheels and tires. I'd be dumb to upsize wheels and gain 4 pounds there and the 4 pounds on the larger tires, 8 pounds unsprung weight gain and $2,000 down the drain- No thanks! Problem solved!

We will though be buying 205/55/16 Michelin Pilot Sport tires for my husband's GT wagon. He just got a huge bonus and he deserves to have great tires too!
Heather

[dunny]

If I remember correctly, Tire Rack did a comparison on exactly this issue a while back. I believe they used a Honda Civic (though I could be completely off base on that one) and did plus one, plus two, and plus three fitments. I think they used the same tire and wheel for each fitment, but in the correct size obviously.

Maybe Luke can dredge up that test

[Heather]

I did read something like that, but it was not from the Tire Rack. It was a Honda Civic going up from 14, 15, 16 and 17 wheels. But they had different tires and they never did mention the weights of the tires or the wheels. All they stated was a couple of opinions in that article and no real data. They did conclude that 17" wheels ran smoother then the others and they liked them the best. If that's the same article you are referring to, I did not like it. But if there is another one, please do dredge it up for me!

I called America's Tire Company, where I bought my Pilot Sport A/S tires. They can get my husband's tire, with a trade for his old ones, at $500 out the door. Now we can't beat that and it's way less the the $2,000 I was thinking of spending for tires and wheels that weigh 8 pounds more then before. We are happy with this choice.
Heather

[rexaroo]

Personally, I would never pay big bucks for any wheel unless they also had a significant advantage in unsprung weight. That means they need to weigh less than the 16.5 lb. stock wheel.

It's been said before and it's true--every 5 pounds in unsprung weight you knock off is like taking 75 lbs. of sprung weight off your car.

So a 16 inch wheel of the same type will always come out ahead of 17 and 18 in my book. The 16-inchers are stronger, lighter, better riding (especially in winter). Also faster accelerating, and sometimes even shorter braking distance with less fade (again because less unsprung weight).

One exception for me is the SSR comps--17 inch are only 12.9 lbs. and flat-out gorgeous, especially when you lower the car.

Another advantage of 16" --if you get them, there's no way you will be tempted into shelling out another two grand for a Brembo big brake upgrade.

[Heather]

Originally posted by rexaroo
Another advantage of 16" --if you get them, there's no way you will be tempted into shelling out another two grand for a Brembo big brake upgrade.

I do have stock 16" wheels on both the GT and the WRX. I hear you there, no temptation for the larger brakes! I did the right thing from the beginning when I bought my WRX in May I bought her Michelin Pilot Sport A/S tires in 205/55/16. I was thinking of going up to 17" wheels with the same tires in 225/45/17, but I know all about unsprung weight and it is not worth the sacrific in performance, not to mention the pocketbook, to upsize my wheels and tires.

I do though wonder, in theory, what the differences are in handling with the 17" wheels. Everyone seems to recommend them and the STI has them. The MRT WRX Trainging book highly recommends 17" wheels as idea for our cars, but they do not say why. Maybe I will never know, or maybe I'll get lucky and someone will let me text drive their WRX with 17" wheels so I can findout for myself without wasting the money.

I think the upgrades i did for my WRX are superior and much cheaper then wheels- 20mm rear swaybar, Steering rack Bushings, the best tires I could buy, the ALK and the Aluminum endlinks.
Heather

[igorshos]

You are forgetting about the increased footprint you get when you go with a bigger wheel/wider tire. It improves traction. I am kind of thinking about Enkei RPF-1, they are only 15.2 pounds in 17" and they are very reasonably priced (about $1000 a set).

I am still running stock wheels/tires and the car gets way too tail happy in those tight turns...

[SpinAll4]

How about running stock wheels with 225/50 rubber. Thats what i have done and think its a great way to go. I am sure the extra tire adds up in weight, but the increase in grip i have experienced has far outweighed any other penalties. My 2 cents.

RB

[JewPac42]

From what I understand going to a bigger wheel means a smaller sidewall. When the sidewall is shorter it has to be stiffer which means that the tires will hold their shape better. This translates into cornering harder, when my car got my OZ P1's (lighter then stock) in 18s the handeling improved slightly. This was not due to more aggressive tires, they were actually less aggressive becuase I needed all weather for the snow I encounter at school. This is just what I think I have read over the years, I'm not exactly sure if it is correct.

[vsigma]

here's another alternative.

find an ultralight/strong wheel in 16" that'll fit a larger brake anyway.

examples: speedline safari's, newer (and current!) speedline wheels, Volk's (ex: TE-37's), BBS wheels and so on.

All lighter than stock, and way stronger as well. All will also fit 4 pots up front under the wrx stock rotor size, or 'almost'-old school-sti rotor size by like 4mm.

[rexaroo]

Sure the 17's have some definite advantages, else no one would be buying them.

Slightly better cornering and steering response, and great to look at. It's fun to dress up your Rex with some eye-catching wheels that turn heads.

But the 16s make for a better "urban guerilla" street-fighter wheel-- stronger for when you hit potholes, faster accelerating when you need a burst of speed in traffic. Plus more comfortable for everyday driving over broken pavement, etc.

For me, the 17" SSRs are really mouth-watering, but I'll probably go with the 16" because only 11.5 lbs. and like you guys mentioned, you can always put wider tread on a 16 if you need to and there are brake kits that will fit.

[Chuck H]

If you're really interested in handling, you probably would have been better off going with the 225/50-16 tires on the stock wheels, rather than keeping the 205/55-16 stock size. Also, I'm not quite sure why you have your heart so set on Michelin tires. I've just never been that much of a fan of Michelins. From everything I've seen they're obscenely overpriced and you can almost always find a better performer for less money. Especially if you're going to have a second set of wheels/tires, then go with a dedicated summer tire like a S03 on the new wheels and keep the stock ones for winter. The S03's are cheaper than the Michelins, stick FAR better in the dry and rain, but are useless in snow.

I'm hoping to upgrade to 16x7.5 SSR Competitions with 225/50-16 SO3's next summer and keep the stock wheels for winter use with real snow tires on them.

[Nordstone]

I generally agree with you on this subject. You can play with sidewall profile and go from 16/55 to 16/50. Some knowledgable people say the car was actually meant for 16/50s.

I debated this for a long time and finally (last week) ended up ordering the Enkei RP02s which are currently on sale in the vendor section. I got a set of 17" wheels for $780 and they only weigh 15.7 lbs a piece. So, they're actually lighter than the stockers.

If you're considering 17's for performance advantages alone, I'd say spend the $1500 else where. However, I live in Minnesota and have started to rallyx. I'm going to put some winter/rally tires on the 16's and summer/three season tarmac tires on the 17's and have the best of both worlds.

So many people buy 17" wheels as a matter of course. If customizing the looks of your car is important, by all means get 17s or 18s.

[Heather]

Originally posted by Chuck H
If you're really interested in handling, you probably would have been better off going with the 225/50-16 tires on the stock wheels, rather than keeping the 205/55-16 stock size.

Yes I am really interested in handling. Here's the facts. Yes a 225/50/16 is wider then a 205/55/16, but not on out stock 16 x 6.5" rims. There is exactly a 2mm width difference on the 6.5" rim, plus the 225/50/16 tires weigh 2 pounds more per tire then the 205/55/16's. This tire needs a 16 x 7" wheel minimum.

Here's a quote from Whiteline, "A tire width was designed by the Manufacturer to work with the wheel size. Increasing width of the tire will not necesssarily increase the contact patch. This is particurarly relevant to standard wheels where overly wide tires will often handle worse then the original with the undersized wheel creating a balloon that easily distorts through a spongy sidewall. Tire width can also be a problem when the extra width grows out from the wheel hub face."

I will be looking into 16 x 7.5" wheels someday. The wider the wheel the better, regardless of the wheel diameter.

Heather

[dunny]

Heather:

Reading your post, I see you've already read the test I did locate, and completely by accident. I remember it being a Tire Rack test because it was done at their headquarters, and using some of their staff, but by Grassroots Motorsports. Here
it is anyhow.

It actually does seem pretty relevant to me. Using the aspect ratios as a guide, the 14-17 sizes on the civic would be equivalent to 15-18 on the Subaru. And aside from the OEM 14" steel wheels and tires, the plus size tests were conducted using the same tire (the Dunlop W-10) and a Kosei 15" wheel and TRM for the 16" and 17". I'm sure Tire Rack could provide weights.

[stanton]

That "plus sizing" experiment provides some good results.

Heather, I'm not sure where you got your "facts". You might be confusing "section width" with "tread width". The 225 is going to give you (approx) 20mm more tread width than the 205. The section width doesn't increase by 20mm because the sidewall is more tucked on the same-width wheel.

The merrits of the 225/50-16 on stock wheels shouldn't immediately be dismissed unless you try it. Lots of wagon owners are very happy with them. Depending on your set-up, it may even keep you in a lower auto-x class - no, sorry, the ALK would change that!

The Pilot Sport A/S in 225/50-16 is recommended for wheel widths from 6.0 - 8.0", so there's no fundamental problem using them on 6.5's. Yes, the wider the wheel, the less flex of the sidewall, but you would have to buy them, they'd be more prone to tire-rubbing and pulling the bead off the rim in extreme circumstances.

Could I suggest that if you're going to head down the 225/50-16 path, to try them on the stock wheels before investing in wider ones? Those tires could then be transferred to new wheels if you still wanted to. (Hint: experiment on Hubby's car)

As an asside, in the 16" vs. 17" weight argument, the "rotational intertia" shouldn't be underestimated. More than 10% more for the 17's if they weigh the same. It was alluded to earlier, but bigger wheels need to weigh much less in order to give the same acceleration (and deceleration).

-Kevin

[Heather]

I agree to the benefit on the 225/50/16 over the 205/55/16, but like I said, not on our rims. That size is recommened for 7" rims not 6.5", although it will fit, it is not optimum for our rims. My problem with that size is they weigh 2 pounds more per tire then the 205/55/16 tires- Just go to any tire manufacturer's website and see for yourself, or call the Tire Rack- they have immediate customer service and have all the tire weights on hand. That's 8 pounds more unsprung weight plus you will not get the full benefit of the tire width due to the narrow rim (you will not get the entire 20mm extra width on your 6.5 rim like you would on a 7 or higher rim). If I had a 16 x 7 rim, I'd buy those tires. I would experiment on hubby's car, but he wants the 205/55/16.
Heather

[drees]

Originally posted by stanton
As an asside, in the 16" vs. 17" weight argument, the "rotational intertia" shouldn't be underestimated. More than 10% more for the 17's if they weigh the same. It was alluded to earlier, but bigger wheels need to weigh much less in order to give the same acceleration (and deceleration).

I was waiting for someone to bring this up. 16.5 lb 16" wheels will accelerate/decelerate quicker than a 16.5 lb 17" wheel!

[Heather]

Originally posted by dunny
Heather:

Reading your post, I see you've already read the test I did locate, and completely by accident. I remember it being a Tire Rack test because it was done at their headquarters, and using some of their staff, but by Grassroots Motorsports. Here
it is anyhow.

It actually does seem pretty relevant to me. Using the aspect ratios as a guide, the 14-17 sizes on the civic would be equivalent to 15-18 on the Subaru. And aside from the OEM 14" steel wheels and tires, the plus size tests were conducted using the same tire (the Dunlop W-10) and a Kosei 15" wheel and TRM for the 16" and 17". I'm sure Tire Rack could provide weights.

Hmmm I just re-read that Grassroots Motorsport article twice. The "Star driver" of the test Brian got the fastest laptimes in the 16's, even faster then the 17's and several of the guys said the 16s were smoother and better. They only said they prefer the 17's due to the "bling" or looks factor. Yes two of the five guys did say the 17's were smoother and quieter, but they also said those wheels were heavier and it was harder to brake and accelerate. Yes they did conduct the test on the same tires and the wheels varied in weight, but they did not say by how much. They concluded they all liked the 15 and 16 combinations the best for daily driving, and for looks and pure lap-times, they would choose the 17's.

Heather

[Heather]

Originally posted by stanton
Heather, I'm not sure where you got your "facts". You might be confusing "section width" with "tread width". The 225 is going to give you (approx) 20mm more tread width than the 205. The section width doesn't increase by 20mm because the sidewall is more tucked on the same-width wheel.
-Kevin

Okay my facts were off. I got my mathematical formulas on width of the tire per tire size on the rim from the book: How To Make Your Car Handle by Fred Puhn. My husband re-did the math this morning and a 225/50/16 tire on a 16 x 6.5" rim will be 1/4 an inch wider then our 205/55/16 tires on the same rims. But if you go up to a 16 x 7" rim or wider, the 225/50/16 tire will spreadout on the rim to it's full potential of 3/4 an inch more then the stock size. With the matter of bulging of the tire, the balloon effect and worse handling as described by Whiteline's fact sheet on tires, I chose against 225/50/16 tires on stock rims. I will though look into 16 x 7.5" rims one day. Heck even 205/55/16 tires on 7.5" rims will spread out more and the contact patch will improve a lot. The rims width is far more important then the tires width- Infact the book recommends a wider rim then tire due to aluminum being much stiffer then rubber. It's all a comprimise. I am sure 225/50/16 tires have some benefits over the stock size and some trade-offs.
Heather

[daveyboy]

For what it is worth, all of the fast STS cars I have seen (I haven't actually seen a fast STX car yet ) are running 15 or 16 inch wheels. I am really tempted to get a set of 17s for the looks, but a set of 16" rota slipstreams in bronze with 225/50s would still look pretty good on my black wrx

[stanton]

Originally posted by Heather

-snip-
Yes they did conduct the test on the same tires and the wheels varied in weight, but they did not say by how much. They concluded they all liked the 15 and 16 combinations the best for daily driving, and for looks and pure lap-times, they would choose the 17's.

Heather

Here's where I was surprised... I always thought "plus sizing" was only increasing the wheel size and compensating with the aspect ratio to get back to the same overall diameter and use the same treadwidth . It's not defined that way at Tire Rack. The test was performed with increasingly wider tires every time the wheel size went up.

I don't think that kind of test is what you wanted answers from. If they performed that test with varrying wheel sizes with the same treadwidth, then I think we'd see some different results.

It seems the wagon can take a maximum treadwith of 225 (with most tires and the right wheels). I'd like to see some quantitative comparisons of 16", 17" wheel combinations while sticking to a common width. Heck, even throw in a range of wheel widths.

-Kevin

[Heather]

When you plus-size a tire you must increase the width as well. It's an aspect ratio of keeping the tire the same diameter on the larger wheel. If you go from 205/55/16 the plus size would be 215/45/17- wider and lower profile. There is no way around this math- Or I don't think there is. Wider is always better, as long as it fits under the car and on the wheel properly. I am now strongly concidering 16 x 7.5" wheels for 225/50/16 tires. Someday though, for now with a baby on the way, it's a low priority. I am just curious to the differences of lower profile/wider tires on bigger rims. I think I understand it theoretically now, but it would still be fun to understand it from experience and real world testing
Heather

[Chuck H]

You're confusing a bunch of different statistics in your analysis.

Going wider is definitely *not* an integral part of plus-sizing. But most people do it when swapping wheels/tires because they figure why spend all that money for an "upgrade" that isn't going to buy you anything other than bigger wheels and shorter sidewalls. That's why Tire Rack went progressively wider with each upgrade size in their test. They were trying to simulate some real-world scenarios that people would buy.

For plus-sizing WRX wheels/tires there are a number of different options. The closest "plus one" upgrade from the stock 205/55-16 size is actually 205/50-17. But most people want more rubber on the ground when they upgrade, so they go with 215/45-17 on wagons or 225/45-17 on sedans. The 225/45-17 is actually closer to stock diameter than the 215, but is prone to rubbing on wagons.

Also, your analysis on the 225/50-16 tires on 6.5 inch wide wheels is misleading. With your Pilot Sport tires, it's true that the section width is only going to increase by about 5mm with the 225's. But the tread width will still increase by almost the full 20mm. And the "ballooning" on a 50 series tire with its short stiff sidewall isn't going to be enough of an issue to counteract the benefits of getting that extra 20mm of tread width down on the road under you.

At a certain point, you have to give up on all the paper analysis and just take the word of all the autocrossers on here that wider is always better up until the point where it doesn't fit on the wheel any more. You should see some of the stuff the Neon autocrossers do, like putting 225/50-15 tires on the factory 14x5.5 or 14x6 wheels on the front. It's WAY outside the manufacturer's specs, but it also wins, so they must be doing something right!

[SC WRX]

I agree with Chuck H. You are confusing section width with tread width. The tread width will remain the same regardless of the size rim used because of the steel belt construction of the tires.