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Discussion Starter #1
Hi,

I have an 06 wrx with 17inch wheels, i was wondering whether it would be better to go down to 16 inch for track use as well as rally (mainly tarmac) as i dont want to have to have too many sets of wheels, i dont want to go up to 18 as to hinder acceleration, however wondered if there were any cons by going down in size.

cheers
 

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Modern tires have excellent sidewall stiffness. It is very unlikely that a well-setup car will "roll-over" the sidewall on a modern tire under any foreseen circumstance.

In other words, as long as the wheels clear a brake setup, I see no reason not to take advantage of the potentially lower mass of a smaller wheel/tire.
 

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Discussion Starter #3
Modern tires have excellent sidewall stiffness. It is very unlikely that a well-setup car will "roll-over" the sidewall on a modern tire under any foreseen circumstance.

In other words, as long as the wheels clear a brake setup, I see no reason not to take advantage of the potentially lower mass of a smaller wheel/tire.
I was thinking going with a stiffer tarmac style tyre if I was to go with 16 inch with a taller side wall.

Where as if I was to go with 17's I'd probably go with something like a nankang ns2r which would have a smaller side wall. Either way I want to go with 7.5-8.5 wide wheels.

Which would be better suite in a track/tarmac style rally application?
 

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With a GD chassis, I think 17x8 is the perfect size. I would think the 16x8 could also suffice. You'd have difficult time fitting anything wider and with good rubber, the 8" tire has plenty of thermal mass... not reason to go wider.
 

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Discussion Starter #5
With a GD chassis, I think 17x8 is the perfect size. I would think the 16x8 could also suffice. You'd have difficult time fitting anything wider and with good rubber, the 8" tire has plenty of thermal mass... not reason to go wider.
Yeah 8 does seem the happy place, its just whether I go for 16's with a beefier sidewall that will cope on track and just generally (probably one with a slighter harder compound so tread wear isnt too bad, or a 17 with a 225/45 nankang ns2r
 

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The TW is a topic that depends on your use.

Typically a 180TW tire like a Pilot Sport Cup 2 will outperform a 200TW tire like the Potenza RE 71R will outperform a 300TW tire like the Pilot Super Sport for track use.

I opted for the Pilot Super Sport because I daily drive my car and am willing to sacrifice some track performance for tire life.

Treadware isn't always indicative of performance, though. The OEM tires that came on my car were Dunlop SP Sport Maxx RT tires with a 240TW. I strongly believe the 300TW Super Sports on my car now outperform the OEM tires on pavement, warm or cold. Block and shoulder design and compound formulation play a bigger role.
 

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Discussion Starter #7
The TW is a topic that depends on your use.

Typically a 180TW tire like a Pilot Sport Cup 2 will outperform a 200TW tire like the Potenza RE 71R will outperform a 300TW tire like the Pilot Super Sport for track use.

I opted for the Pilot Super Sport because I daily drive my car and am willing to sacrifice some track performance for tire life.

Treadware isn't always indicative of performance, though. The OEM tires that came on my car were Dunlop SP Sport Maxx RT tires with a 240TW. I strongly believe the 300TW Super Sports on my car now outperform the OEM tires on pavement, warm or cold. Block and shoulder design and compound formulation play a bigger role.
Yeah I'm in the same boat, I also daily the car usually so am willing to sacrifice some performance but still want a track capable setup
 

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While not specific to all tires, the tire sidewall aspect ratio will help determine the sidewall stiffness. FWIW, a stiffer sidewall prevents a feeling of rolling over in hard cornering. The trade-off is that a stiffer sidewall makes for a stiffer ride.

I'll touch briefly on the more track oriented types of tires. The Pilot Super Sport Cup 2 is famous for one or two hero laps and then falling off. Another general statement is that many tires will be gone after XX numbers of heat cycles. The tread may look fine, but once you cross the number of heat cycles, the tire becomes greasy very early on in a session. Cornering suffers and so does braking. The fix is another set of tires. One example of this is the Michelin Pilot Sport 4S (PS4S). This is a very good road tire. It works well in the wet and wears well. However, the number of heat cycles is very low. Perhaps as low as 10 or 12 (2-3 track days). Once that line was crossed, the tires become greasy and performance fall off quickly.
 

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The issue people run across isn't the wheels, it's the brakes. On gravel you'd run small discs anyway, so a 15" wheel would likely still clear them OK. On tarmac though you'd want larger discs.

So people end up swapping both wheels and brakes for tarmac vs. gravel.
 

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Discussion Starter #10
While not specific to all tires, the tire sidewall aspect ratio will help determine the sidewall stiffness. FWIW, a stiffer sidewall prevents a feeling of rolling over in hard cornering. The trade-off is that a stiffer sidewall makes for a stiffer ride.

I'll touch briefly on the more track oriented types of tires. The Pilot Super Sport Cup 2 is famous for one or two hero laps and then falling off. Another general statement is that many tires will be gone after XX numbers of heat cycles. The tread may look fine, but once you cross the number of heat cycles, the tire becomes greasy very early on in a session. Cornering suffers and so does braking. The fix is another set of tires. One example of this is the Michelin Pilot Sport 4S (PS4S). This is a very good road tire. It works well in the wet and wears well. However, the number of heat cycles is very low. Perhaps as low as 10 or 12 (2-3 track days). Once that line was crossed, the tires become greasy and performance fall off quickly.
Yeah I was thinking if I was to go with a more rally style wheel with a thicker sidewall I'd have to make sure it had a really stiff sidewall to limit as much roll over as possible
 

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Discussion Starter #11
The issue people run across isn't the wheels, it's the brakes. On gravel you'd run small discs anyway, so a 15" wheel would likely still clear them OK. On tarmac though you'd want larger discs.

So people end up swapping both wheels and brakes for tarmac vs. gravel.
Yeah I get that, the problem is I'm aiming for more of a rallycross style build that can cope on multiple surfaces rather than all out track or rally
 

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Smallest strongest wheel that can clear your brakes. Braid makes some phenomenal wheels. Everything from custom race wheels to production everyman's wheels.
 

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Discussion Starter #13
Smallest strongest wheel that can clear your brakes. Braid makes some phenomenal wheels. Everything from custom race wheels to production everyman's wheels.
Would that be even for tarmac, I'm trying to build a car that can basically cope with both track and rally, obviously with suspension adjustments to suit? Almost like a rallycross car
 

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Because of your multi terrain goal you have to find a mid ground. My biggest concern with non paved surfaces is impact damage. Even 1/2 inch additional of tire below the wheel can help. With modern tires you should be able to find something to fill your need for sidewall strength as you go down in wheel size.

I would opt for 16-17 inches in a forged wheel, or wheel designed for use in a high speed rough terrain environment. Braid would be my choice.
 

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Discussion Starter #17
Because of your multi terrain goal you have to find a mid ground. My biggest concern with non paved surfaces is impact damage. Even 1/2 inch additional of tire below the wheel can help. With modern tires you should be able to find something to fill your need for sidewall strength as you go down in wheel size.

I would opt for 16-17 inches in a forged wheel, or wheel designed for use in a high speed rough terrain environment. Braid would be my choice.
Standard are 17 but I was thinking going to either 17x8 or 16x8 and then getting some rallycross (street legal tyres) 235 or 225/45 tyres
 
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