235 45 R18 rear and 245 45 R18 possible?

[AShingers]

Currently have a 2.0 tsi 220 superb estate

 

I need some new tyres on the front and currently have 235 45 R18 all round (pirell Cinturato P7).  The rear tyres replaced last year so probably have about 4 years wear left.

 

Now I am thinking of going with 245 45 R18 on the front and leaving the 235 45 r18 on the back.  Is this possible? 

 

There is much more choice of 245's they are slightly cheaper, wider with more grip and have deeper sidewalls so probably more comfortable.

 

The total circumference difference is only 1.3% with a 1mph difference in Speedo reading.  Only possible issue I forsee is ACC issues possibly, has anyone actually done this and have they had any of these issues or did it all go well?

[SurreyJohn]

It's not good idea to mix wheel sizes, even if on different axles.

 

Also if you have the relatively high powered car (220), the idea of changing tyre sizes to save a few pounds, is not really very good thinking from safety point of view.

 

If anything bigger wheels would normally be on the back, so why can't the back wheels go on the front

 

What season are you looking at, or is it all year (all season), you can get all the best rated ones in 235/45 R18 anyway (Continental all season contact 2, Michelin cross climate 2, Goodyear vector 4season gen 3, Pirelli all season SF2 etc

[AShingers]

They absolutely could go on the back and switch around that's just how they at the minute.  It's not just to save a few pounds that's one of various positives 

 

1. more grip as wider contact patch 

2. Deeper sidewall so more comfortable 

3. More readily available size (hence cheaper 

4. More rim protection 

 

I am was looking at summer tyres in the above probably PS4 was topping the list.

 

I have been considering some all season tyres for a while but would need to switch fronts to back so they all wear out at the same time first if I did this.

 

My only concern with all season is there performance in the dry/wet in the summer months.  If it's constantly going to be spinning up the front wheels during warmer wet days that doesn't sound good but I can't find any information on this so would be useful to have some real world experiences as to grip levels in the warmer months particularly in the wet 

[MarkyG82]

Not a good idea to mix tyre types (it's unclear if that's what you are talking about re. all seasons).  Different grip levels front to back is asking for trouble.

Also not a good idea to mix sizes front to back as the ABS (and associated safety systems) will not function correctly.

[AShingers]

I wouldn't mix types it was purely a question about if going to 245 tyres from 235 would they need to all be changed at the same time or could I do them two at a time without it effecting ACC ESP etc

 

It will probably be safer for me to switch the current tyres round until they are all worn out at the same time and get four all together. That way I can buy 4 tyres in the slightly wider size without any of these issues.  I just think the 245's will be slightly better in various ways so would like to change to this size.

 

I think what I would like is the most summer bias all season tyres possible.  I want to reduce the occasional wheelspin when pulling out of cold wet junctions etc and have a bit more grip over winter for increased Safety if that makes sense.  Not bothered about on the limit dry/wet handling (it's a family estate) I just want to reduce wheelspin in poor conditions 

[nta16]

15 hours ago, AShingers said:

There is much more choice of 245's they are slightly cheaper, wider with more grip and have deeper sidewalls so probably more comfortable.

1 hour ago, AShingers said:

I wouldn't mix types it was purely a question about if going to 245 tyres from 235

1 hour ago, AShingers said:

I just think the 245's will be slightly better in various ways so would like to change to this size.

 

Just going slightly wider with the same make and model of tyre is unlikely to give you much difference in grip other than a new tyre being less worm and aged.  A wide tyre compared to a narrow tyre gives a different foot pattern but not considerably more road contact with small increments of tyre width.

 

Grip is more about the tyre's design and make up, a different model or make and model of tyre may offer more, about the same or less grip, same for ride comfort, noise, handling and braking.

 

If you were to reduce the wheel size (if possible) to 17" this would give more options but I don't know about availability and cost for any of these sorts of sizes.

 

A different model or make and model of tyre may offer more rim protection, plus I think I've seen you can buy separate rim protectors.

 

These larger wheel and tyre sizes are often more about fashion, and possibly mine are bigger than yours for some blokes, those that want them then that's fine, each to their own, but fashion usually puts form over function.

 

Tyres are a very complex and important component on a vehicle unfortunately it's not just a matter of the numbers and even the numbers can't all be taken at face value, have a look at a tyre catalogue for one make and model over the various sizes of tyre available in that make and model and you might see what I mean with that.

 

I suggest it could be useful to ask on the relevant Superb forum here what other 2.0 TSI 220 owners use and find with tyres.  HTH.

 

[MarkyG82]

The wider tyre will also weigh more. This affects acceleration/deceleration as the rotating mass is greatly increased.

Additionally it will affect the suspension performance. If its comfort and safety over performance I'd go smaller and maybe narrower.

It also depends how wide your wheels are.

[Ootohere]

Audi had wider front than rears as a option on RS3,s. (AWD,s)

 

I used to use 215/40 R 17,s on the front of Mk2 Fabia vRS & 205/40 R 17,s on the rear.

 

Actually measure tyres circumferences when on the wheels as the sizes on the sidewall or using a comparison site might not be the actual difference with tyres of a different manufacture / type  / tread.

 

But think what you are doing, check and take any consequence of co-cking up if you do. 

[AShingers]

That's the site I used, if they are not completely accurate it seems this is more hassle than it's worth, I'm just going to change the wheels round and wear them all down so I can replace all 4 at once 👍

[Ootohere]

They are accurate enough.   (They are not accurate as to what they say the speedo might read or under read as they over read with the OEM tyres on.)

 

All i am saying is when you have different tyres, new or used, run the tape measure around them.

Tyre off the rim and tyres on the rim and inflated and sometimes there can be just a ba,s hair of a difference. 

 

eg a new 205/40 R 17 Dunlop Sportmaxx does not measure the same as new 205/40 R Pirelli Zero Nero.  Which can measure the same as a 215/40 R 70 from another brand.

Edited 24 November, 2023 by Rooted

[nta16]

@AShingers

 

2 hours ago, Rooted said:

All i am saying is when you have different tyres, new or used, run the tape measure around them.

Tyre off the rim and tyres on the rim and inflated and sometimes there can be just a ba,s hair of a difference. 

Or IF available look at the tyre manufactures' specifications on their sites or catalogues, the same make and model of tyre can also differ over the range of sizes and some sizes are nominal. 

 

2 hours ago, AShingers said:

I'm just going to change the wheels round and wear them all down so I can replace all 4 at once 👍

👍

 

[MarkyG82]

@Rooted do you think the variance is to do with the profiles being "binned" into 5% pots? A tyre that is 33% high could be placed in the same size as one with 37% for example. Both might be rounded to 35. On a 245 tyre that would be nearly 10mm difference!

[Ootohere]

It can make a difference with XL / Reinforced tyres or not, and if there is any Rim Protection or not.

Just measure tyres side by side when on rims, not just tyres on a rack. 

 

Find the actual differences with a tape measure and not by some Table or Comparison tape and tread or tyre width and circumference / total diameter.

 

eg,

A mix of 205/40 R 17 here and 215/40 R 17, and there are 205/40 R 17,s bigger than the 215,s.

 

Edited 26 November, 2023 by Rooted

[MarkyG82]

But then if your insurance company step in and say "you have different tyre sizes fitted!" (in a grumpy grown up voice), no amount of showing them real life measurements will convince them (maybe).

It's a bit of a mess really, and just reinforces the theory of fitting the same make and model all round.

[Ootohere]

You do what you do or want and don't risk it for a biscuit.  Way too risky for the risk adverse. 

 

Loss adjusters might well check, might well not be totally daft & have a bit of knowledge.  

'Stretched tyres' would be a total no no for me, and should maybe be for MOT,s and road side checks & insurance underwriters.

 

?

Is this about Insurers and Tyre Approval / Certificate or Confirmation and approved standard OME Tyre sizes.

 

If the car has approved sizes / tyres - wheels of different sizes but the same Speed / Load ratings can the different axles have tyres / wheels from these sizes? 

 

Audi option of wider on the front and rear, BMW, Mercedes, Porsche, Audi etc etc etc larger rear than front.

Skoda Enyaq, ID4 etc Staggered Tyres / wider/ larger rear than front.  Honda Electric, BMW i3 etc.

 

Can you take the Staggered wheels and change than for matching front and rear winter time?   When you need Snow Chains?

When you want to carry a spare that will suit front & rear!

 

Is it just a matter of declaring mods then as we do with Off-roaders or other cars, Modified or kit cars etc.

 

215 front, 205 rear, matching circumference.

& the orange JImny,s never came with tyres the size this one had on. 235,s.

Edited 26 November, 2023 by Rooted