Short story: 235/45R17 fits nicely on my stock suspension Octavia 1.8T. Also looks nice and aggresive on Avus Audi S3 17" rims (wider and more offset than stock 17" spyder rims), my intention of keeping the car as a sleeper just went down the drain. Before/after pics below.
Long story:
So after running around the whole year incognito mode, steel 15" rims 195/65R15 w/o hubcaps, enjoying myself, and faces of unsuspecting BMW drivers - I've done the famous AUM stage 1 remap to 210 hp after which the tyres can't handle the acceleration in first two gears, and made the car almost impossible to accelerate/drive when raining so I had to do something about the grip. The idea was to get ANY cheapo/trash/dank - undamaged 17" rim to fit the standard 225/45R17, I really wanted some Fe rims (again, incognito-sleeper style), but they don't exist in 57,1 5x100 dimensions (there is a 5x100 17" steel rim, but it's for some huge Renault, and I think it's only for the spare wheel, making the rim witdh in range of lol-J). There is a lot to choose in 16" region, but 205 is just too small for the power the car makes, IMHO. I even looked into 215 combinations in 16" and not only there is no performance tyre in this dimension, it's ridiculously expensive.
Mind you, I'm running standard setup on all four corners - Bilstein B4 shocks, Bilstein OEM springs - no lowering, I was a click away to order the heightened springs!! I'm never going to be a style-slave, laughing while just casually cruising over speedbumps whereas dropped GTI's/Type-R's/RS's have to do the diagonal idle+clutch maneuvers
I also fancied the idea of fitting larger tyres on it, 235/45R17, my flow of thought was the following, pros/cons:
+ more grip ofcourse
+ more offset/scrub radius - more initial turn-in, responsiveness on the steering wheel
+ more accurate speedo
+ keeping comfort (decent sidewall)
+ less wear
+ overall height of car increased, again more comfort
+ tyre "attack angle" smaller, making it easier to run over obstacles (eg. curbs, speed-bumps), again, even more comfort (you probably noticed a pattern, I'm anti-style oriented, pro-sleeper/comfort style :))
+ visually I always liked seeing fat-meaty tyres in the back
+ only slightly more expensive than 225/45R17
- very little experience on Octavia mk1 + that tyre combo, some say it fit's others say it doesn't
- much heavier
- slower acceleration
- possible rubbing
- worse fuel consumption (it's LPG-ed and it's dirt cheap here in Croatia)
Anyway, I managed to snatch a great deal on original 17" Audi S3 "Avus" Alu rims (made by Ronal, Made in Germany), bonus points: they are 6 mm more offset and 0.5J wider than standard rims 17" Spyders, making way for wider tyre! All the calculations point to no rubbing with 235/45R17 ( https://www.wheel-size.com/calc/?wheel1=195-65-15X6ET38&wheel2=235-45-17X7.5ET32&fcl=50mm&scl=50mm&wcl=30mm&sr=0mm left is my standard setup, right is Avus). But a real life test is needed, I don't want to risk spending €€€'s and putting new summer 235's just to find out they don't fit/rub! So I also managed to snatch winter tyres dirt cheap (almost free), Hankook Winter iCept 235/45R17 DOT2016 halfway worn - perfect for testing out the setup - if it fits, great, if it doesn't I spent a few hours and a few bucks demistifying it.
Putting on just the rim on the car was a shock, when lifted, viusally seems like ~2 cm more than outline of car, ouch - on the inside though, quite a lot of space; the guys at the wheel shop rolled they eyes constantly We fitted the tyre rim combo, dropped the car, did a run around the lot full lock..... Purrrrfect, no rubbing, and when car is sitting on it's own it's just right, slightly out of car outline, this will be a slight pain to homologate tho.
Inital impressions after a few runs:
+/- wheels are a stunner, so much for my incognito/sleeper preferences, honestly, looks much more aggressive than the RS... I guess I'll deal with it.
+ very soft and controlled wheelhop, car doesn't want to break apart when you loose grip
+ comfortable
+ better turn-in, much less wobbly car
- awfully heavy, steel rims+tyre 16.6 kg, alu rims+tyre 22.4 kg, ouch, you can see the pictures below, but I'll write up for any google search guys to stumble upon this, I find it invaluable info:
- 235/45R17 Hankook Winter iCept 1/2 worn: 10.5 kg
- Audi S3 Ronal Alu 17" rims: 11.7 kg
- 17" above tyre+rim combo: 22.4 kg
- 15" stock steel rim + 195/65R15 Pirelli P7 combo: 16.6 kg
- noticeably "slower", feeling is the inital throttle response is much lazier, not so agressive as on 15"; can't really blame it, the car couldn't even accelerate before
Didn't try the twisties yet, but the idea is to run around a few weeks and notice how the car behaves and if there will be no rubbing in spring get the Goodyears F1 Assy 5 in 235/45R17.
@Madket