Spare tire question for those who have OEM 20s

[AccordingToAlex]

Hi all,

For those who have an A/S5 that came with OEM 20s, do you have a 20" donut in the back? If so, any idea what part number it is? If not, what is in its place? Thank you

[Smac770]

The B9 spare wheel is a 19x4 compact.
8W0 601 027 C for steel.
8W0 601 027 E for aluminum.

None of the brake systems on the B9 require a 20" wheel that I know of.
D5 420mm ceramic requires 20", but the B9 ceramic is only 400mm.
The B9 era workshop manual fails to document these specifications.

[Andy_FL]

Hi all,

For those who have an A/S5 that came with OEM 20s, do you have a 20" donut in the back? If so, any idea what part number it is? If not, what is in its place? Thank you

S5: I have a 19" donut, as Smac770 commented.

[AccordingToAlex]

Thanks guys. I guess what I'm trying to wrap my head around is how it is possible to use a 19" spare with 20s. Wouldn't that fry the Quattro? Or do they put taller tires on the models that came with 20s?

[JohnEnglish]

Thanks guys. I guess what I'm trying to wrap my head around is how it is possible to use a 19" spare with 20s. Wouldn't that fry the Quattro? Or do they put taller tires on the models that came with 20s?

Yes, it has a taller side wall. The circumference of the spare tire is the same as the OEM 20" wheel.

[CurvesAhead]

Thanks guys. I guess what I'm trying to wrap my head around is how it is possible to use a 19" spare with 20s. Wouldn't that fry the Quattro? Or do they put taller tires on the models that came with 20s?

Here is what came with my car: A LingLong T125/75R19. More info in your other post under Wheels and Tires. The sidewall on the 19 inch spare does not appear taller that the 20 inch tire that came on the car.

IMG_0649 2.jpg

[Smac770]

All the B8 and B9 cars have the same target tire diameter. That's why the lower profile tires on the larger wheels. 245/40 for 18 but 245/35 for 19, etc.

The allroad is +1" vs the non-allroad cars. Ie, 245/45r18 rather than 245/40r18, etc. Thus it uses a different spare, 175/55r19 expandable on 19x6. The expandable aspect allows it to fit in the same spare tire well but inflate to match the +1" main tires.

[Liquid Smoke]

i have an S5 with the factory 20" wheels, and i also have that same spare, LingLong T125/70/19. the 125/70 is thicker than the stock 265/30, the overall diameter ends up about the same so it's not an issue. it will not damage anything using it as a temporary spare.

[CurvesAhead]

i have an S5 with the factory 20" wheels, and i also have that same spare, LingLong T125/70/19. the 125/70 is thicker than the stock 265/30, the overall diameter ends up about the same so it's not an issue. it will not damage anything using it as a temporary spare.

Thanks for confirming the spare is adequate for the S5 with twenties.

[Smac770]

Here is what came with my car: A LingLong T125/75R19. More info in your other post under Wheels and Tires. The sidewall on the 19 inch spare does not appear taller that the 20 inch tire that came on the car.

IMG_0649 2.jpg

unloaded new diameter comparison
mains:
(2*245*0.40)/25.4 + 18 = 25.72"
(2*245*0.35)/25.4 + 19 = 25.75"
(2*255*0.35)/25.4 + 19 = 26.03"
(2*265*0.30)/25.4 + 20 = 26.26"
spare:
(2*125*0.70)/25.4 + 19 = 25.89"

So you see how the spare straddles the center ground between the various sizes.

As for is that ok, let's consider your tires at new. So:
axle 1: (25.89"+26.26")/2 = 26.075 average.
axle 2: (26.26"+26.26")/2 = 26.26" average.

non-haldex quattro requires a 2mm max tread depth average diff between the two axles. That's on both sides of the tire, so 4mm max diameter diff, or .1575". But yours would be .1850". So yeah, on brand new 265/30, the spare would seem a bit too small. Drop the pressure in the mains a tad? The real problem is these are unloaded new diameters. Who knows what your real rolling diameter is, as that'll vary with tire wear and tire pressure and current vehicle load.

But since the spare limits you to 50 miles at not more than 50 mph, I wouldn't stress about it.

[CurvesAhead]

unloaded new diameter comparison
mains:
(2*245*0.40)/25.4 + 18 = 25.72"
(2*245*0.35)/25.4 + 19 = 25.75"
(2*255*0.35)/25.4 + 19 = 26.03"
(2*265*0.30)/25.4 + 20 = 26.26"
spare:
(2*125*0.70)/25.4 + 19 = 25.89"

So you see how the spare straddles the center ground between the various sizes.

As for is that ok, let's consider your tires at new. So:
axle 1: (25.89"+26.26")/2 = 26.075 average.
axle 2: (26.26"+26.26")/2 = 26.26" average.

non-haldex quattro requires a 2mm max tread depth average diff between the two axles. That's on both sides of the tire, so 4mm max diameter diff, or .1575". But yours would be .1850". So yeah, on brand new 265/30, the spare would seem a bit too small. Drop the pressure in the mains a tad? The real problem is these are unloaded new diameters. Who knows what your real rolling diameter is, as that'll vary with tire wear and tire pressure and current vehicle load.

But since the spare limits you to 50 miles at not more than 50 mph, I wouldn't stress about it.

Thank you Smac770 for posting the numbers and explanation concerning the spare, like you said: we should be fine.

[AccordingToAlex]

Got it. So after reading all this wonderful information, the conclusion is: Flatbed LOL. These RS5 rotors have 275/30s on them which would make them 26.5" in diameter, which is an almost 15.5 mm difference from the spare diameter. Thanks again everyone, in really do appreciate all your input and information!

[JohnEnglish]

I had my RS5 with 20” OEMs get a flat tire and I used the temporary spare and drove over 30 miles on it without any problems.

[AccordingToAlex]

I had my RS5 with 20” OEMs get a flat tire and I used the temporary spare and drove over 30 miles on it without any problems.

Interesting! I thought all RS5s came with fix-a-flat and no spare?

[Smac770]

There is no spare tire/wheel part in the B8 RS5 catalog. There is one in the B9 RS5 catalog.

[AccordingToAlex]

There is no spare tire/wheel part in the B8 RS5 catalog. There is one in the B9 RS5 catalog.

What's the part number? 8W0 601 027?

[Smac770]

I posted in the second post. ...027 C for steel, ...027 E for aluminum.

The B8/B9 spares come in three PR codes:
1G5 - steel
1G6 - aluminum
3F1 - expandable

The 1G6 is specific to the RS models, but it's only for weight. Same physical dimensions and same tire, Hankook S300 T125/70r19

B8 used the same T125/70r19 100M tire, but by Continental. I don't find the Hankook on Tirerack, but I do find the Continenal.

But I wonder with those 275/30, if you might find the 3F1 for the allroad more interesting. I couldn't find the specs for the B9 version (8W9 601 010 B), but the B8 version was 175/55r19 expanded, or 26.58". The B9 should be the same, as it uses the same tire sizes as the B8. Also the benefit of 2" wider wheel and tire. Though still 50/50 limited as I understand it. Being an expandable, you would need the air compressor too, which you might already have if you have the 1G8 "road hazard repair kit" instead of an actual spare.

[Smac770]

If I can ever find a not-temp use tire of suitable size and a wheel, I'll be happy to tell these temp spares off.

For my 245/40r18, which my A4 brakes can handle 17",:
175/65r17
175/55r18
175/50r19
185/60r17
185/55r18
185/45r19
195/55r17
195/50r18
195/45r19

Even 175 might cause the cargo floor to sit a few mm up, but that's fine. 165 would be best. But you can't find a real tire that's narrow in 17" or 18".

50/50 should be illegal.

[Smac770]

Or just swap out the spare with a larger one:
https://www.tirerack.com/tires/tires...omCompare1=yes

26.4", assuming the extra 3/4" fits in the spare wheel well. (where do they expect you to put the dead full size tire if you're loaded up on a trip?)