Reducing rim size on vRS

[kaanage]

Personally, i think you'll be pretty disapointed in the result though.

Because of the taller tyre profile (since the vRS is the equivalent of a GTi)?

225/55R16 is almost spot on for rolling diameter, has the same contact patch and would be only marginally less responsive.

If the improved ride means DunlopRS doesn't have to slow down for rough patches or run really high tyre pressures and have the car crashing about, then that's a real world performance gain.

Running 45 psi is a recipe for disaster. ..... That sort of pressure on any road surface with irregularities is simply asking for a monumentally large blow out and instant tyre deflation to occur when you roll over something that is sharp and pointing at the tyre.

Tyres are far tougher than that - damage from sidewall pinching over sharp edges is far more likely than any possibility of puncturing due to lack of pliability

[Diesel_vert]

A few folk on briskoda have fitted RS 312mm discs & carriers (the std calipers will fit) to their 288mm/16" cars & it works as long as the wheel weights don't get in the way. You have to test fit your wheel of choice though as profiles vary.

I had a strong suspicion they'd fit.

My sweet spot would be 17x7.5 ET50 with a 235/40x17 if it doesn't throw the speedo into over-reading.

I think 235/40 R17 (1891 mm) is too small. It'd be like fitting the equivalent of a 205/40 R18 (1895 mm) tyre.

And although it's more compliant than 225/40 R18 (1943 mm), it's actually less compliant than 225/45 R17 (1934 mm).

225/55R16 is almost spot on for rolling diameter, has the same contact patch and would be only marginally less responsive.

I think 225/55 R16 (1995 mm) is too big. It'd be like fitting the equivalent of a 245/40 R18 (1992 mm) tyre.

In terms of response, it's only better than 195/65 R15 (1937 mm), which results in an overly comfort biased setup IMO.


My 2 cents:
I think sticking with the OEM 16" wheel dimensions with the OEM tyre size of 205/55 R16 (1928 mm) is the best way to go.

If the improved ride means DunlopRS doesn't have to slow down for rough patches or run really high tyre pressures and have the car crashing about, then that's a real world performance gain.

+1111111

Probably the most underrated quality in any car - be it for racing or road use.

Tyres are far tougher than that - damage from sidewall pinching over sharp edges is far more likely than any possibility of puncturing due to lack of pliability

I tend to agree.
As long as the inflation pressure doesn't exceed whatever is on the tyre's sidewall (typically 350 kPA or 51 psi for high speed passenger tyres) it should be fine, if not ideal.

[kaanage]

I think 225/55 R16 (1995 mm) is too big. It'd be like fitting the equivalent of a 245/40 R18 (1992 mm) tyre.

In terms of response, it's only better than 195/65 R15 (1937 mm), which results in an overly comfort biased setup IMO.

Whoops!! Sorry for the typo - I should have typed 225/50R16

[Diesel_vert]

Whoops!! Sorry for the typo - I should have typed 225/50R16

Ah, I see. 225/50 R16 (1928 mm) does indeed have an identical rolling circumference to 205/55 R16 (1928 mm) and is as compliant. It's also actually a tiny bit wider than 225/40 R18.

In fact, a 225/50 R16 tyre on a 6.5 J x 16 wheel can potentially be slightly wider (by up to 3mm) than a 225/40 R18 tyre on a 7.5 J x 18 wheel. But this ultimately varies depending on the make and model of tyre due to tolerances.

[DunlopRS]

, then that's a real world performance gain.

Real world performance is what it is all about. This is the quickest car I have ever owned – and that includes a number of big sixes – its ability to get past road trains quickly with no fuss is phenomenal. However dropping off the bitumen half way past is something I do not enjoy on 40 series tyres……..

[gldgti]

To whom it may concern....

The wheels fitted nicey and DunlopRS is happily on way home -

Once fitted up, there was a good 6mm clearance between the balancing weights and caliper.

Win for all!

[kaanage]

Everybody wins

It'll be interesting to hear DunlopRS's long term verdict.

[gldgti]

My own take - on 16's -

When I first got the octy with the 16's, I felt that the steering response, handling and ride were all excellent. The only thing I didnt like was the looks.

I bought some badly gutter rashed audi ronals, 17x7.5 et50, bogged and resprayed them, got tyres and fitted them.

Handling over bumps with the 17's is notably worse (significant increase in sprung weight) but on a smooth road the drive is nicer. I dont think anyone would notice an ultimate performance difference in normal road driving.

I would say provided the quality of the rubber is good, and using the 55 series tyres, the real world performance could only benfit.

I would also disagree with K1W1 - 45 psi is not too high for just about any low profile tyre. Most 45 and lower profile tyres have printed a maximum inflation presure between 45-50psi. The last two sets of "extra load" tyres I have bought (due to the bad roads) have been 57psi max inflation pressure.

I think statistically I do enough km on bad roads ridden with corrugations and potholes to have had some kind of exploding tyre by now - but the only problem I've ever had is from running 45 series tyres at below 38psi - when the rim was damaged and the tyre deflated.

Still, death may come for me yet.

kaanage - thankyou, I had no idea there was also a dancing carrot, chillie and (i guess) cucumber. Awesome.

[DunlopRS]

Thanks to all for the comments.

The wheels fitted nicey and DunlopRS is happily on way home -
Once fitted up, there was a good 6mm clearance between the balancing weights and caliper.
Win for all!

Thanks to gldgti for indulging me in a try-before-you buy. As noted the fit is good.
Great trip today – 5.1 L/100 km from Canberra to the end of the M7 (downhill) and 5.5 L/100 km OA for the 731 km round trip……

Everybody wins

It'll be interesting to hear DunlopRS's long term verdict.

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.

[brad]

I think 235/40 R17 (1891 mm) is too small. It'd be like fitting the equivalent of a 205/40 R18 (1895 mm) tyre.

And although it's more compliant than 225/40 R18 (1943 mm), it's actually less compliant than 225/45 R17 (1934 mm).

woops. I meant 235/45x17

I think 225/55 R16 (1995 mm) is too big. It'd be like fitting the equivalent of a 245/40 R18 (1992 mm) tyre.

In terms of response, it's only better than 195/65 R15 (1937 mm), which results in an overly comfort biased setup IMO.

I'm running 225/55x16 at the moment. I'd rather run them than 205/55x16 (which I have done). A bit more grip, you can run them at 36psi all the time, responsive & the sidewalls are so tall you don't have to worry about kerbing your rims. You can belt up driveways & through potholes without an issue. They make the speedo 100% accurate rather than the 10% under that the OEM 205/55x16 gives you.

I drive on some really lousy private roads at silly speeds & they work great.

The cons are that the tyres weigh 10kg & the Audi 16x7.5 rims I have weigh 10kg.

Before the Audi rims I had a set of 17x8 ET35 BBS with 225/45x17 which weighed 18kg. Got rid of them because they had too much poke & the previous owner had kerbed them too much.

And before that the 16x6.5 ET51 with 205/55x16 that weighed 17.2kg.

For my next set of wheels (I change wheels when the tyres wear out - it's like having a new car), I'd like 17x7.5 ET45-50 with 235/45x17 weighing around 17kg. I think that might be the sweet spot for me.

My 2 cents:
I think sticking with the OEM 16" wheel dimensions with the OEM tyre size of 205/55 R16 (1928 mm) is the best way to go.

See above re: innacurate speedo. Also the odometer is too far out. 15,000km on the odo is ~14,000km actual.

To the OP: I'd still only drop to 17". vRS come out stock in most parts of the world with 17". Easy to justify the change to your insurance company.

[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.