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Old 10-08-2015, 04:54 PM   #1
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17" vs 18" wheels (not a tire thread)

Now, I probably should post this in the racing section but this one gets the most traffic and it would be nice to have a " general discussion" about wheel size. So I have a Boxster S (there's that S again) that I occasionally track. It has 18" wheels with decent street tires which seem to be okay on the track Won't name them, it's not a tire thread. There's been some mention of using 17" wheels on the track: tires less expensive, etc.
Okay, so can we dicuss the merits/drawbacks of 17" vs 18" wheels with their proportionate tires on the Boxster ( or 986, or Porsche Roadster, or Ssssss, haha)
No, seriously though.
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Old 10-08-2015, 05:27 PM   #2
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I have considered getting 18 inch wheels for my non S. But I can't seem to pull the trigger. Is one inch going to make my car look or handle that much better? Is the added cost of the 18 inch tires worth it? I'm not sure. I seem to spend enough money on it already without the more costly tires I seem to replace every three years. Here are a few pics I took. My car silver with 17 inch wheels. My buddy's grey S with 18 inch wheels.




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Old 10-08-2015, 05:40 PM   #3
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I run 17"s on the track, 225/45/17 and 255/40/15. Stock sizes for Boxster in 18 are 225/40/18 and 265/35/18, not that much more rubber, and they are much more expensive.

In Hankook RS3, I can't really go any wider with 17's, and not really that much wider with 18's. Same with a tire like Nitto NT-01, can't get any wider in 17's and the wider 18's are way wider like for GT3 type.

I think Hoosiers and the like have more options for getting wider and custom wheels may support those wider widths.

For me it is mostly cost I think, way cheaper to run 17's.

Others may have some feedback and maybe there are more tires available that I don't know about
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Old 10-08-2015, 05:41 PM   #4
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One plus for 18's is that Michelin pilot super sports don't come in 255/40/17 but they do come in the 18 sizes.
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Old 10-08-2015, 05:54 PM   #5
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I'm considering buying a second set of wheels for the track. 18s are pretty but this is less important when I'm peeling off layers of rubber in those 20 minute runs. This is why I thought 17s might be a viable option.
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Old 10-08-2015, 07:35 PM   #6
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I specifically bought a set of 17's for track and AX. Most likely they will get shod with RS3's. Maybe something else after I speak with a bunch of track rats when I am at Chuckwalla in a few weeks.

17" tires are about 20-15% less expensive than 18"
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Old 10-08-2015, 07:58 PM   #7
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I'm not sure about tire size availability, but wouldn't 17's with a smaller diameter tire give you a lower center of gravity and raise the RPM level to a more suitable level for the track? Weight is an issue also.
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Old 10-08-2015, 08:23 PM   #8
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As Steve pointed out, there is no difference in the width of the front tires and only 10mm additional width in the rear tires when comparing 17" vs 18" and the 17" is cheaper and weighs less.

Track winner = 17". (In theory)

How much does it really matter? Ignoring cost, probably not enough to worry about. Your level of driving skill will make MUCH more difference than 17" vs 18".
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Old 10-08-2015, 08:39 PM   #9
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Quote:
Originally Posted by itsnotanova View Post
I'm not sure about tire size availability, but wouldn't 17's with a smaller diameter tire give you a lower center of gravity and raise the RPM level to a more suitable level for the track? Weight is an issue also.
Tire diameter would be the same
for example 255/40-17 is the same diameter as 265/35-18
if there is a difference, its less than .25 inch
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Old 10-08-2015, 09:19 PM   #10
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My son and I replaced the factory 18s with factory 17" on his 99 in June. The 18s are chrome and a little beat up. The 17" tires are definitely less expensive. I took the time to weigh the 17" with brand new tires vs the 18" rims with half tread in front and bald rears. The 17" were way lighter! The fronts are 5# less, the rears are 6.5# less!
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Old 10-09-2015, 02:17 AM   #11
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Quote:
Originally Posted by tommy583 View Post
I have considered getting 18 inch wheels for my non S. But I can't seem to pull the trigger. Is one inch going to make my car look or handle that much better? Is the added cost of the 18 inch tires worth it? I'm not sure. I seem to spend enough money on it already without the more costly tires I seem to replace every three years. Here are a few pics I took. My car silver with 17 inch wheels. My buddy's grey S with 18 inch wheels.




You have the nice body kit. IMO, when you have side skirts on the car, you need 18" wheels to balance out the look, as they make the wheels look too small. Mine on 18"...

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Old 10-09-2015, 04:53 AM   #12
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Why not go for boxster 16s 205 front and I think 205 rear.

That's a big difference between 18s and having driven one of each they sure handle and rev differently!

Get some cheap 16 inch tires and have fun
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Old 10-09-2015, 05:09 AM   #13
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Why not go for boxster 16s 205 front and I think 205 rear.
OP says he has an S so 16s won't clear the brakes (evidently).
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Old 10-09-2015, 05:54 AM   #14
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I will say that for looks the 18" Cayman S wheel is my personal favorite:


It seems to look a little "tougher" and the tire sidewall is shorter to account for the larger diameter of the wheel. To some people those particular ratios look better.

For 17" my favorite wheel is the Boxster S twist:



That is another "muscular" looking wheel but is heavier than the 996 Carrera Twist which is a common wheel for spec boxster:


I got these images from here:

944racing
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Old 10-09-2015, 04:26 PM   #15
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Quote:
Originally Posted by NewArt View Post
Now, I probably should post this in the racing section but this one gets the most traffic and it would be nice to have a " general discussion" about wheel size. So I have a Boxster S (there's that S again) that I occasionally track. It has 18" wheels with decent street tires which seem to be okay on the track Won't name them, it's not a tire thread. There's been some mention of using 17" wheels on the track: tires less expensive, etc.
Okay, so can we dicuss the merits/drawbacks of 17" vs 18" wheels with their proportionate tires on the Boxster ( or 986, or Porsche Roadster, or Ssssss, haha)
No, seriously though.
Performance difference and tire choice is probably not noticeable.
Appearance is completely subjective.
Cost and weight, hat tip 17" wheels.

Pick your poison.
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Old 10-09-2015, 05:49 PM   #16
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My first post here

I've been hanging around here for a while but haven't posted yet, so here goes. I have a 2003 S that I bought new and now has close to 54,000 miles. It came with the 18 inch 5 spoke Carrera Lightweight wheels. Last year I found a good deal on a set of 5 double spoke 17 inch wheels that were standard on the 2003 Boxsters. I haven't been to the track yet, my reason for buying the 17 inch wheels was to put an extra half inch of sidewall between my rims and what passes for roads here in Northern New Jersey. In everyday driving, the ride is a bit more comfortable with the 17 inch wheels, there is no detectable difference in handling. In stock sizes for the Boxster, the 17 and 18 tires have practically identical outer diameters. My 18 inch wheels have Michelin Pilot Sport PS2 N-3 tires, and the 17 inch wheels have Toyo Proxes T1 Sport tires. Interestingly, to me anyway, was that there was no real weight savings with the 17 inch wheels and tires compared to the 18s. 1 front 17 was 41.4 lbs vs 1 front 18 at 41.6 lbs. At the rear, 1 17 was 46.8 lbs and 1 18 was 48 lbs. The 17 inch tires were brand new, the 18s were not - 18,500 miles on the front tires and 5,700 miles on the rears, but still have lots of tread left on all of them.
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Old 10-09-2015, 06:52 PM   #17
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Old 10-10-2015, 05:43 AM   #18
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Quote:
Originally Posted by PaulE View Post
In stock sizes for the Boxster, the 17 and 18 tires have practically identical outer diameters. My 18 inch wheels have Michelin Pilot Sport PS2 N-3 tires, and the 17 inch wheels have Toyo Proxes T1 Sport tires. Interestingly, to me anyway, was that there was no real weight savings with the 17 inch wheels and tires compared to the 18s. 1 front 17 was 41.4 lbs vs 1 front 18 at 41.6 lbs. At the rear, 1 17 was 46.8 lbs and 1 18 was 48 lbs. The 17 inch tires were brand new, the 18s were not - 18,500 miles on the front tires and 5,700 miles on the rears, but still have lots of tread left on all of them.
Welcome to the forum, and thanks for the real world data. Even though not rigorously scientific, this data does indicate there is not much if any advantage in weight of one over the other after including the tire weight.

Also as you noted, there is usually no significant advantage in tire diameter with a 17" vs. 18" due to the street tire industry's dedication to that +1/-1 tire sizing concept, since they don't want anyone's speedometer or traction control to be fooled.

It may seem obvious, but the wheel is there for one reason - to support the tire. So it comes down to first selecting the tire size that you can and want to run, and then selecting the wheel to match. If you want to run something wider than a 255 tire, your choices for fitment on a 17" wheel are very limited, and will probably not get any better in the future. If you plan to stay with 255 and smaller tires, the 17" wheel is a good lower cost option.

One caution with 17" wheels: If you ever shim your rear toe links to adjust bump steer, it can cause the retaining nut where the rear toe link bolts to the upright (wheel bearing carrier) to make contact with the inside of the wheel. This happened with my OEM 17" wheels that I use for rain tires, and I didn't realize it until I was bolting them on in a hurry for a wet track session. I was able to file the nut down about 2-3 mm to clear this clearance issue, but this took off the nylon part of the lock nut. I later drilled and safety wired. This is probably not an issue unless you are seeking the last fraction of an improvement in suspension set-up.
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