Reducing rim size on vRS

[pologti18t]

I hope the tyres used as replacement have the same/better load rating and what about the speed rating?

[kaanage]

I will source some new tyres in the next couple of weeks and let you know of the results after my next sortie into the bush.

I am sure that DunlopRS will make sure his permanent tyres are compliant for load and speed. Anyway, it's easier to find tyres with high load ratings when they have taller profiles (for the same width) due to the larger air volume.

[DunlopRS]

Yes, as indicated the next “challenge” is tyre selection. I will definitely respect minimum load index (91 – and given the rough roads I travel on am keen to get something higher than this) and the minimum speed rating of V. Most of the tyres in my possible basket have no troubles at least with the speed rating. I usually end up with something out of the Michelin/Yokohama/Pirelli range and this is again the likely end point (an early experience with wide BF Goodrich TAs on a 265 charger brought physics into the real world (or at least my world) as wider tyres do not always mean more grip – as you are putting the same mass onto a bigger area – while great on the black top, unsealed roads were a real joy (those torsion bars..) – learnt a lot about predicting what the car was going to do when the surface changed……..).

There have been a few posts on tyre size. While leaning towards the std 16” fitment of 205/55 the comments about that 225/55s are worth following up on. This would also give more protection of the rim from the potential for brushing against the kerb parking….. And it would be nice to have a speedo that gave a slightly more accurate indication of speed (I reckon its about 5-8% fast – but remedying this will also likely increase indicated fuel consumption….)
The generic tool on carbon black (Tyre sizes) gives:

Specifications Sidewall Radius Diameter Circumference Rev/Miles Difference
205/55-16 113 mm 316 mm 632 mm 1985 mm 504 0.00% man recommended 16" fitment
225/55-16 124 mm 327 mm 654 mm 2054 mm 487 3.50%
225/40-18 90 mm 319 mm 637 mm 2002 mm 500 0.80% current fitment
225/50-16 112 mm 316 mm 631 mm 1984 mm 504 -0.10%

If the comment on that webpage that +/-15mm D is all that’s legal is correct it looks like the 225/55 is out? - so I have probably answered my own question…..
I understand 215/55-16 is an uncommon size?
215/55-16 118 mm 321 mm 643 mm 2020 mm 495 1.70%

I'm running 225/55x16 at the moment. I'd rather run them than 205/55x16 (which I have done).

brad – what vehicle are you running the 255/55-16s on? – as the RS sits a bit lower than a std Octavia I would also need to consider guard clearance with the 17mm higher (from 18” or 22mm from 16”) tyre…

[brad]

minimum load index (91 – and given the rough roads I travel on am keen to get something higher than this) and the minimum speed rating of V.

I thought it was 92? (as per your first post)....... /looks at placard on own car....... OIC - 91 it is.

I usually end up with something out of the Michelin/Yokohama/Pirelli range

Good choice but don't forget Continental & the higher end offerings of Goodyear, Bridgestone & Toyo.

And it would be nice to have a speedo that gave a slightly more accurate indication of speed (I reckon its about 5-8% fast – but remedying this will also likely increase indicated fuel consumption….)

No, it will give an accurate fuel consumption readout rather than p!ssing in your pocket.
The speedo will be 100% accurate. There will be no margin for error.
One of the reasons I'll be going smaller diameter again is that my daughter gets her Ls next year, so I need some wiggle room for her.

If the comment on that webpage that +/-15mm D is all that’s legal is correct it looks like the 225/55 is out? - so I have probably answered my own question…..
I understand 215/55-16 is an uncommon size?
215/55-16 118 mm 321 mm 643 mm 2020 mm 495 1.70%

225/55x16 is +17mm but that is nominal sizing & most tyres have 13mm of useable tread over the diameter (8mm total less 1.5mm minimum depth x2). Personally, that doesn't phase me as the legal requirement is mainly to do with speedo accuracy (it was a speeding case with a guy with a Suzuki Sierra with big tyres), so if the speedo still reads correctly then you are still within the intent of the law.
Continental Extreme Contact DW & Yokohama S-drive are both a few mm smaller (653mm rather than 655mm) than the norm & should fit within the letter of the law if you are still concerned.

brad – what vehicle are you running the 255/55-16s on? – as the RS sits a bit lower than a std Octavia I would also need to consider guard clearance with the 17mm higher (from 18” or 22mm from 16”) tyre…

I have an Octavia Elegance hatch, so it's a bit LandCruiser-like in it's stance. I've never experienced any tyre rubbing with any of the tyre/rim combos I've run. The cuurrent tyre is a Michelin Primacy HP.

My current 16x7.5 rims extend 13mm closer to both the strut & guard than the 16x6.5 you have. The edge of the front tyre sits level with the lip of the guard; the edge of the back tyre sits 20mm inboard of the guard lip.

The 17x8 ET35 BBS rims extended 34mm outwards. The fronts poked outside the guards & the rears were level. The extra offset stuffed up the feel of the handling.

I like your idea of 215/55x16. There's a reasonable selection in 93V/W - not much in XL/99 though.

The other size to consider is 225/50x16. You get a lot more choice of performance tyres in that size. Load rating is generally 92 with V or W speed ratings.

I haven't any photos with the 16x7.5 but here are some with your new rims & the BBS
OEM


OEM


BBS


BBS


OEM Landcruiser-like stance

[kaanage]

The other size to consider is 225/50x16. You get a lot more choice of performance tyres in that size. Load rating is generally 92 with V or W speed ratings.

That's the one that would get my vote as it would match the OE gearing better and the slightly lower profile would retain more of the sporty feel that you expect of the vRS.

[DunlopRS]

Thanks guys,
I must work out how to ensure cynicism comes across right. I always like instruments to be accurate....

I thought it was 92? (as per your first post)....... /looks at placard on own car....... OIC - 91 it is.

For some reason on my car 16&17" are marked as load index 91 & 18" as 92.
Am well aware of this anyway.

Off shopping next week.....

[brad]

Off shopping next week.....

Have a look at tirerack. You'll get ContiExtremeContact DW in 225/50x16 for <AUD900 landed in ACT. Yokohama S-Drive for about $40 less. Some very nice performance tyres there if you want to pay a bit more.

Allow $25 for bank fees & $80 for fitting/balance

[Diesel_vert]

I hope the tyres used as replacement have the same/better load rating and what about the speed rating?

The Road Transport Act 2000 (ACT) basically says that any tyre you fit should be capable of at least 180 km/h (for passenger cars) or the vehicle's top speed - whichever is the lesser of the two.

Therefore, he could fit tyres with a speed index of S (which corresponds to 180 km/h) on his vRS if he really wanted to.

It also allows the operator to fit winter tyres (which often have a speed index several categories below a typical summer tyre) without contravening regulations.

I usually end up with something out of the Michelin/Yokohama/Pirelli range and this is again the likely end point (an early experience with wide BF Goodrich TAs on a 265 charger brought physics into the real world (or at least my world) as wider tyres do not always mean more grip – as you are putting the same mass onto a bigger area – while great on the black top, unsealed roads were a real joy (those torsion bars..) – learnt a lot about predicting what the car was going to do when the surface changed……..).

When it comes to modifying cars, the benefits or advantages of most mods often do not increase in a linear fashion.

There have been a few posts on tyre size. While leaning towards the std 16” fitment of 205/55 the comments about that 225/55s are worth following up on. This would also give more protection of the rim from the potential for brushing against the kerb parking….. And it would be nice to have a speedo that gave a slightly more accurate indication of speed (I reckon its about 5-8% fast – but remedying this will also likely increase indicated fuel consumption….)

In terms of rolling circumference:

205/55 R16 is the near equivalent of 225/40 R18 (and 225/50 R16 as well)
215/55 R16 is the near equivalent of 235/40 R18
225/55 R16 is the near equivalent of 245/40 R18


Both 215/55 R16 and 225/55 R16 tyres would also benefit from 7.0 J x 16 wheels due to their width, but it's perfectly acceptable to fit them on 6.5 J x 16 wheels as well (in fact, the lowest you can go with is 6.0 J x 16).

If the comment on that webpage that +/-15mm D is all that’s legal is correct it looks like the 225/55 is out?

Different states and territories have different regulations.

The Road Transport Act 2000 (ACT) says that as long you don't fit a tyre with a section width over 30% (or, for a four-wheel drive built for off-road use, 50%) larger than the largest optional tyre specified by the vehicle's manufacturer, you'll be fine.

225/55 R16 is perfectly acceptable.

I understand 215/55-16 is an uncommon size?

Any tyre that isn't fitted to an Australian or Japanese car is uncommon.

Though as sales of European cars increase, tyre importers/distributors will have more incentive to bring in Euro-centric sizes at cheaper prices. For example, prices of 225/45 R17 tyres (a common European fitment) have gone down a lot.

For some reason on my car 16&17" are marked as load index 91 & 18" as 92.

A standard load 225/40 R18 tyre has a load index of 88, whereas a reinforced or extra load 225/40 R18 tyre has a load index of 92.

The load index of the standard load tyre was probably a bit too low for comfort, so they went with the extra load version.

Have a look at tirerack. You'll get ContiExtremeContact DW in 225/50x16 for <AUD900 landed in ACT. Yokohama S-Drive for about $40 less. Some very nice performance tyres there if you want to pay a bit more.

Allow $25 for bank fees & $80 for fitting/balance

The price of smaller tyres here usually aren't exorbitant enough to justify importing a set, but depending on what's available here compared to overseas, it may (or may not) be worth it.



Finally, choosing which non-original tyre size to go with is mostly a personal decision. As as long as it doesn't contravene any regulations, there really isn't a right or wrong choice - it all depends on what you want from a tyre.

[applesee]

DunlopRS, have you taken any photos of the car with the 16" alloys on?
I'm planning to do the same, but purely for taking the car above the snow line (so that snow chain can be fitted).

Haven't had much luck finding a set of 16" in Victoria though.

[brad]

Haven't had much luck finding a set of 16" in Victoria though.

You must be joking? There are heaps of suitable rims in VIC. I have the audi 16x7.5 on my car - cost me $400 in new condition with near new michelins.

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