245/40/18 tyres - OK to run on the rear?

[DALE_AVANT]

Hi guys.

Would 245/40/18 tyres be fine for the rear on my Avant Sport? I have two spare so I may as well use them if I can.

Many thanks

 

[pink.teg]

Wat size rims are they
???

 

[DALE_AVANT]

Wat size rims are they
???

8J x 18".

ET43.

The width should not be an issue but I think the rolling radius will be out a little

 

[quattrojames]

Rolling radius shouldn't matter on the rear, assuming your car isn't a quattro.

 

[DALE_AVANT]

Rolling radius shouldn't matter on the rear, assuming your car isn't a quattro.

Nah it FWD. I meant in relation to space in the rear arches over bumps and such

 

[pink.teg]

In that sence ... No problems
i have a Quattro
and have 234/40/18 on front
245/40/18 on rear and it's fine
was on RR and the bloke that set up my map asked !
and said the read out was fine !!

 

[jbcalvin]

245 is the width of the tyre and will not have any effect on the rolling radius, 40 profile is right for 18" wheel, you should be fine with these, it's only 10mm wider than a normal 235....

 

[DALE_AVANT]

245 is the width of the tyre and will not have any effect on the rolling radius, 40 profile is right for 18" wheel, you should be fine with these, it's only 10mm wider than a normal 235....

245/40 has a larger rolling radius than 235/40, as the 40 represents a percentage of the 235/245.

So 40% of 245 = a bigger overall tyre than 40% of 235 (iirc)

 

[PetrolDave]

See the tyre size calculator here Cheap Low Price Special Offer Alloys and Tyres from TYRESAVE

235/40 x 18 has an overall diameter of 245mm, but 245/40 x 18 has an overall diameter of 653mm, i.e. 8mm or 1.24% larger.

 

[BahnStormer77]

In that sence ... No problems
i have a Quattro
and have 234/40/18 on front
245/40/18 on rear and it's fine
was on RR and the bloke that set up my map asked !
and said the read out was fine !!

FWD should be fine to run different rolling radius tyres, but you are putting a lot of completely pointless strain on the quattro differential by doing what you're doing... it'll run fine on RR or on the road, but it just works the differential constantly...

 

[pink.teg]

K
will wack the 235's back on ASAP then

Cool save them for the dry summer days ...

 

[BahnStormer77]

other thing to bear in mind for anybody who's got FWD and wanting that hot-rod stnad with slightly chunkier tyres on the rear... it may seem really obvious, but wider tyres = more grip... so the back will grip more and increase understeer...

One of the later model Polo GTI's (2008?) has NARROWER tyres on the back to give the car a more neutral balance on the limit

 

[quattrojames]

One of the later model Polo GTI's (2008?) has NARROWER tyres on the back to give the car a more neutral balance on the limit

I 'think' RS3's do too.

 

[avantsport]

Will 245/40/18 on 8j et 43 go on the avant sport front and rear as i have a full set from an a6 but unsure if they will fit.

 

[archemist]

Will 245/40/18 on 8j et 43 go on the avant sport front and rear as i have a full set from an a6 but unsure if they will fit.

they'll be about 2% bigger (RR / circumference ) than standard 215/55/16 baseline

Tyre Calculator - Alloy Wheels - Specialist supplier of alloy wheels and tyres packages, Fast Delivery, Buy Online.

gives you loads of option for tyre width / size.

don't know about width (+5mm both in and out) but if people are running spacers and 35 et's then the ouside 'rim' shouldn't be a problem

don't know about the 5mm nearer inner wheel liner though.