Quick tyre question

[Singh]

I have 9J 275 35 20 tyres on my car at the moment, will I be able to fit 285 30 20 wheels on to the alloys okay?
Also out of interest what's the max tyre that could go on, any help would be appreciated as I want to order my new tyres today.

[Architex_mA8tey]

hi Amar

use the following website to tell you what the effect will be
http://www.kouki.co.uk/utilities/vis...ize-calculator

I think you will be over 3% out on your old size on overall diameter which will affect your speedo reading.
its more important if youve got staggered set up like me to make the back and the front get near enough that the quattro doesnt misinterpret the difference as wheel spin but if you are doing all 4 then you should be ok. Your overall rolling radius will be slightly smaller so your speedo will read faster than you are actually doing.

BUT with a 9" width wheel they recommend the minimum tyre width to be 235mm, the ideal to be 245 or 355mm, and the maximum to be 265mm so as you have 275mm you are already over the recommended maximum and shouldnt go wider still

HTH
Cheers Neil

[Singh]

Thanks Neil, that site is quite helpful. I upgraded from 245 45 18 so I am actually going to be getting more accurate speedo reading by going to a 30 profile over 35. I may try 285..

[Conan_the_Librarian]

The corret wheel and tyre combination should give a rolling radius of 2129.06 mm

Therefore with a standard 18" whell the tyre is 245/45 18
for a 19" wheel it is 245/40 19 for a rolling radius of 2131.88 (0.13% difference)
for a 20" wheel 245/35 20 gives 2134.71 (0.27% difference)

Once you start playing around with cross sections and tyre width it's just a case of keeping as close to stock as possible to not cause any speedometer errors (a potential MOT fail)

However, most speedos read high so they don't fall foul of the construction and use regs with regard to accuracy. A speedometer mat read upto 10% high but may not have any error reading low. manufactures also use this to 'demonstate how economical' your car is. You think your doing 70 and realy your doing 64..........

Your wheel tyre combination is about max for a D2 on the front.
the rolling radius is 2200.68 about 3.36% oversize and probably on the limit of your speedo error. When your speedo says you are doing 70 you may be doing 72.35. However if you speedo is reading high in the first bplace you have just corrected it with the tyre size! Check it against a satnav for accuracy.

The tyres you have (275) are designed for a 9" - 11.5" wheel. A 285/30 20 will need a 9.5" wheel minimum and I think you'll have rubbing issues at the front. At the back you should be able to get an 11" wheel with a proper offset of about 35. I have a 10" rear to go on with an ofset of 55 and i will use 15 or 20mm spacers to make it sit right.

If you want a staggerd set up then to maintain rolling radius parity front to back the 245/35 20 fronts match 285/30 20 rears running on 8.5 - 9.5 wheels front and 9.5 to 11 rears.

265/30 20 and 315/25 30 also match; but will cause your speedo to read high (show 70 when you are doing 68. If you can find them well done. If you can afford them, buy a D3 S8 and stop wasting money on tyres for a D2!!!!!

[Architex_mA8tey]

oh and what he said too !!! ^^^^^^

[Singh]

Thanks for your post Mike, well my alloys are from a D3 so does that count? I have just ordered some 285 30 20 Michelin PS2 tyres, they are meant to be the best. Saw your post a little late. Fingers crossed they fit if not my girlfriends dad has 285 30 20 tyres on the rear of his car so will give them to him.

[Singh]

I could be wrong maybe my wheel is 9.5J why would Audi mount 275 35 20 tyres to a 9J tyre if the maximuim recommended is 265mm, sureley the millions they spend on development would have flagged that up. Does anyone know what tyre size the D3 alloys are

[Architex_mA8tey]

Originally Posted by Singh

I could be wrong maybe my wheel is 9.5J why would Audi mount 275 35 20 tyres to a 9J tyre if the maximuim recommended is 265mm, sureley the millions they spend on development would have flagged that up. Does anyone know what tyre size the D3 alloys are

if it's 9.5J that would make more sense Amar as the max tyre size recommended is then 275mm, which is what youve got currently

[Singh]

Nope, just found out its 9J. But the C5 RS6s boys fit 275 tyres on their 9J wheels and they come standard with 255. I think it should be okay, if it rubs at the front I will add some spacers. At £295 each they better be a good tyre. All four Verdistans at the moment are bald, dad nearly killed me when he saw them so had to order some asap, doubt they have 1mm on them.

[Architex_mA8tey]

lol that must have been James doing donuts when he tried out your car the other day