255/35/19 tyre pressures

[gman11]

Hi, conflicting tyre pressures for my tyres. Purchased my A6 last weekend and upgraded my alloys to 19" Blackline. Checked tyre pressures when I got home, and they ranged from 34psi - 38psi. Been online and asked a couple of tyre fitters and contacted local Audi dealer. Dealer stated they were an "odd" fitment, and didn't have the tyre pressures listed, although recommended 32psi for front, and 30psi at back. Others have mentioned 30 in the front and 28 in the back. Any response would be greatly appreciated.

[GrolschUK]

All supported wheel and tyre combos should be on the sticker in the drivers side door.

My FL BE 2.0 Avant is showing as wanting 36/35 for 19" rims, but show the tyre profile as being 255/40... 255/35R20

Yours may be different depending on spec of the car, so take a look at what the sticker says.

Would running a lower profile tyre than suggested mess up the speedo and odometer, as you will be travelling less distance per revolution?

[isleaiw]

All supported wheel and tyre combos should be on the sticker in the drivers side door.

My FL BE 2.0 Avant is showing as wanting 36/35 for 19" rims, but show the tyre profile as being 255/40... 255/35R20



20" tyres on 19" rims would have very interesting pressures!

[GrolschUK]

20" tyres on 19" rims would have very interesting pressures!

I Probably could have worded that a bit better

I've got 255/40 on 19"
His 255/35 is recommended 20" rims on the pressure sticker, and thus putting that profile on a 19" rim is going to mess things up a little.

[GrolschUK]

Being quite sad (and also interested in the affect of this)

Allowing for slightly iffy maths skills
For every 10,000 miles on the clock, the car would have only travelled 9,600 if using /35 rather than /40 on 19's
And sat at <cough> 70 on the motorway, you will only actually be doing 67

[MarkTM]

Doesn't the engine size and whether saloon or estate play a factor since a 3.0 lump weighs significantly more than a 2.0 and a 5 door more than a 4?

May be useful if you actually state this...or ideally put your car spec (year/variant/engine) in your signature strip:confused:

[gman11]

Doesn't the engine size and whether saloon or estate play a factor since a 3.0 lump weighs significantly more than a 2.0 and a 5 door more than a 4?

May be useful if you actually state this...or ideally put your car spec (year/variant/engine) in your signature strip:confused:



Apologies if I have not given enough information. It is a 2013 2.0 TDI 177 saloon. As I have already explained, main ******* stated he has not got tyre pressures for my tyres as they are an odd size.


Also, the sticker in the side of the drivers door does not give 255/35/19 tyre pressure.

[wildbore]

Apologies if I have not given enough information. It is a 2013 2.0 TDI 177 saloon. As I have already explained, main ******* stated he has not got tyre pressures for my tyres as they are an odd size.


Also, the sticker in the side of the drivers door does not give 255/35/19 tyre pressure.

As far as I can see, that size rim should be fitted with a 255/40/19" tyre. That would explain why the dealer says that they don't have a recommended pressure.

[gman11]

As far as I can see, that size rim should be fitted with a 255/40/19" tyre. That would explain why the dealer says that they don't have a recommended pressure.


These are the dimensions of each rim......... PCD - 5x112

size- -19x8.5

offset/ET - 35

centre bore - 66.45

I have tried gaining the suitable size of tyre to fit these dimensions online, unfortunately have come up so far with a big zero. I wonder if there is someone more technically minded on the forum able to shed some light?

[MarkTM]

Am assuming that the tyres are Extra Load as (IIRC) they have to be for insurance purposes due to the weight of the car.

Googling the tyre size brings this up on an A5 forum:

19" Y tyre pressure - Audi A5 Forum & Audi S5 Forum (http://www.a5oc.com/forums/a5-general-q/6529-19-y-tyre-pressure.html)

[GrolschUK]

These are the dimensions of each rim......... PCD - 5x112

size- -19x8.5

offset/ET - 35

centre bore - 66.45

I have tried gaining the suitable size of tyre to fit these dimensions online, unfortunately have come up so far with a big zero. I wonder if there is someone more technically minded on the forum able to shed some light?

A search on any tyre selling site for 255/40/Y19 should fit your wheels, I don't think the PCD, Offset or anything other than the rim dimensions will make a difference...
You should find you have the pressure ratings for that size on your door sticker too.

[gman11]

Thx Mark, although still confused around correct pressures. So many conflicting recommended tyre pressures. On a positive note though, the rims set the car off perfectly. :biglaugh:

[wildbore]

These are the dimensions of each rim......... PCD - 5x112

size- -19x8.5

offset/ET - 35

centre bore - 66.45

I have tried gaining the suitable size of tyre to fit these dimensions online, unfortunately have come up so far with a big zero. I wonder if there is someone more technically minded on the forum able to shed some light?

OK, if the wheels are genuine Audi then the PCD and centre bore will be correct.

I can't comment on the offset; that information should be in the owner's handbook, though.

The 19" rim isn't available on the A6 any more but it is the standard fitment on the S6. The Wheel size is 19x8.5 and the fitment is the 255/40/19 tyre. This is the tyre you need to fit to your car to get the correct rolling radius for the A6 chassis. A 35 section tyre will be too small so your speedo will read incorrectly and your engine gearing will be out, it won't look as good in the wheel arch and it will invalidate your insurance unless you notify them that you have deviated from factory-fit specification.

[gman11]

The wheels are not genuine Audi, after market make YSM by all account.

[gman11]

I just contacted two separate alloy wheel specialists who informed me the correct tyre size for my rims are indeed 255/35/19. At least that is one thing less to be concerned about. Would that make more sense wildbore?

[wildbore]

I just contacted two separate alloy wheel specialists who informed me the correct tyre size for my rims are indeed 255/35/19. At least that is one thing less to be concerned about. Would that make more sense wildbore?
Not to me, but I am no tyre expert. Ideally, you need to know the wheel and tyre specifications for 19" rims for your specific model of A6 and for your specific model year of car, which I am sure would have had a 19" option available (I think the 19" option was only dropped at the facelift?). That information would be in the relevant brochure or your owner's handbook. As far as I can see, the correct tyre is the 40 profile but if I were in your shoes I would go on what Audi specified at the time and nothing else.

As a cross-check, there are internet sites that provide a rolling circumference for a given tyre size. I suggest you input your car's standard tyre size and then your desired tyre size for your new rims; they should be very close. If the figures differ then the tyre is not correct and you will have speedo error and gearing issues.

[wildbore]

Here you go, pop your current and desired tyre sizes in here:
http://www.club80-90syncro.co.uk/Syncro_website/TechnicalPages/TRC%20calculator.htm (http://www.club80-90syncro.co.uk/Syncro_website/TechnicalPages/TRC%20calculator.htm)

[gman11]

Thanks wildbore

[GrolschUK]

I just contacted two separate alloy wheel specialists who informed me the correct tyre size for my rims are indeed 255/35/19. At least that is one thing less to be concerned about. Would that make more sense wildbore?

They may be the correct size for the rims, but they are not the correct size for your car.
I'm pretty sure any 255/?/19 tyre will be correct for the rims...

The /35 and /40 are the tyre profile... the smaller the number, the narrower the sidewall is.
Less sidewall means a smaller diameter for the entire wheel.
Smaller wheel, as Wildbore pointed out, means that the gearing, speedo, and odometer will be out.

I have an A6 with 19" wheels that came with the car from new.
The tyres are 255/40/19
The tyre pressures are 36 front, 35 rear on a 2.0 TDI Auto

[gman11]

Here you go, pop your current and desired tyre sizes in here:
http://www.club80-90syncro.co.uk/Syncro_website/TechnicalPages/TRC%20calculator.htm (http://www.club80-90syncro.co.uk/Syncro_website/TechnicalPages/TRC%20calculator.htm)


Interesting. Standard 225/50/17 speedo deviation @ 100km/h is 5.7km/h. My 255/35/19 speedo deviation is 0.7 km/h. So the 19's are more accurate showing on the speedo as opposed to the 17's.

Tyre suspension comfort is obviously better on the 17's, but I can live with that. Who would have thought it eh?

[gman11]

I finally found out tyre pressures as well. Contacted the shop where the alloys were purchased from. 2.2 bar for front and 2.1 bar for back

[wildbore]

Interesting. Standard 225/50/17 speedo deviation @ 100km/h is 5.7km/h. My 255/35/19 speedo deviation is 0.7 km/h. So the 19's are more accurate showing on the speedo as opposed to the 17's.

Tyre suspension comfort is obviously better on the 17's, but I can live with that. Who would have thought it eh?

Current standard 17" tyre is a 225/55, not 225/50 :confused: Have they changed fitment since your car was made? Could you post a pic of the tyre pressure label that is fitted to your car? that should really tell us everything we need to know.

[gman11]

Ooops, you are quite right. -2.7 speedo deviation on the 19's

[GrolschUK]

Current standard 17" tyre is a 225/55, not 225/50 :confused: Have they changed fitment since your car was made? Could you post a pic of the tyre pressure label that is fitted to your car? that should really tell us everything we need to know.

Fitment hasn't changed
I've just found a copy of the pre-FL brochure that I had downloaded last year.

Standard wheels are:
SE - 17" 225/55
S-Line - 18" 245/45
BE - 20" 255/35
Hybrid - 17" 225/55
S6 - 19" 255/40

With every 'optional' wheel showing the same tyre size per rim as above.


So as long as your car is a 2011- C7, your new tyres to go on your new 19" rims need to be 255/40... and the pressures will be as per the sticker on the door.
If you stick with your choice of 255/35, every 10k miles your car thinks it has done, it will have only actually travelled 9.6k, as well as other things being out of alignment.

[gman11]

New tyres needed methinks..........Thx for your input everyone.

[Clauuualc]

The setup that you have is like the C6 A6.

The C6 has smaller wheels than the C7. I also have a 2.0tdi C7 and run 19" on it but 255/40 R19. My friend has a C6 and runs 255/35 R19.