Would you alter your tyre sizes?

[mik]

Prompted by a discussion on the Loltus forum - bloke who chose the larger 23" wheel option for his Eletre is unhappy with the OEM Pirellis (both the wear rate, and the fact a new set is £2k), but Lotus appear to have chosen a bit of an oddball size (for the rears in particular) so options are limited unless he moves to slightly different sizes.

It occured to me that I've done this quite a bit over the years on various cars, for various reasons. As you can fit different sizes of metric sized tyres on an imperial sized wheel rim you have this flexibility. (Toyo are one of the few manufacturers who quote a recommended wheel rim width for each of their tyres - so they are a great reference source).

Obviously you need to apply caution - particularly on cars with staggered front/rear sizes. In addition to "could this size fit on my wheel rim?" you need to consider speed and load ratings, any rolling-radius (tank track) changes and how that could affect your gearing / speedometer reading / ABS / TCS / ESP / centre diff (AWD ICE only) yada yada.

So woodya/couldya?

[Jobbo]

Have done in the past, do currently and will do in future.

[integrale_evo]

Yes, lots. Because I’m a very naughty boy.

[John]

Have done, will do.

[Delphi]

The rears on the 928 are a rare size (245/45/16) but I wouldn't fuck about with using different tyre sizes - If I'm batting down the autobahn at over 140mph, I don't want any scary surprises (or a potential fiery death). I know my knowledge limitations and if Porsche's chassis engineers dictated that size tyre, then that's what I'll use. Appreciate that's an extreme example, but I never take chances with tyres as they're your only contact with the road.

[Beany]

The Z4C has come on non-factory wheels and tyres (which aren't that well fitted, bit of a stretch) so I might as well include myself in the 'would' category.

They're brand new tyres though and there's no problems, it just leaves the rim exposed a bit more than I'd like. So I'm not dumping >£700 for aesthetics.

[mik]

The rears on the 928 are a rare size (245/45/16) but I wouldn't fuck about with using different tyre sizes

I'm with you on that very specific situation - mainly because there are zero suitable 235 or 255 alternative options you can jump to

The 944 Turbo came on the same rear size - weirdly I think the situation (in terms of tyre choices available) is slightly better than it was 15-odd years ago, but it is the reason why many so many owners decided to move over to 17" Cup1 or Cup2.

I started fiddling around with this topic when I was at uni driving a knackered old SuperStrada. OEM tyre size was a weirdo 165/65/14, but I realised that the (steel) wheels were 5.5J14. The majority of the hot hatches of the day had the same wheel size (in alloy) and almost all ran 185/60/14. So I switched over to that size to get access to loads more performance-oriented options, which were also much cheaper.

[Matty]

Done on the Lupo and the Up mainly because they used odd factory sizes that were mega expensive, so going with slight more girth was much cheaper.

[Rich B]

i would and have on most of my cars. There’s often a better/cheaper/available/etc size or spec of tyres that get recommended.

[Carlos]

Back when you had them the handbook would often have more than 1 width tyre per diameter wheel from factory. My daughters Mito could have had 205 or 215 17's.

I would generally stick to the manufacturers recommendation though. Seems daft to ignore all that R&D to save a few quid per corner on a performance car.

[Marv]

IDGaF about kettle wattage Mik, but tyres are an area of geeky interest to me

I don’t think I’ve ever fitted a non-oem tyre size to a car I’ve owned, but I haven’t owned that many cars and the tyre sizes for my cars are quite prevalent and decent tyres are available for them, so there has been no reason to stray away.

I don’t have anything against people going up/down sizes slightly though. Probably with most cars it would be difficult to tell the difference anyway.

[Mito Man]

I'd change sizes a bit without being too concerned if the difference in price is really that much but in the situation of the Eletre chap, unless I've got a spare set of wheels I'm not messing about with a near 3 tonne unreliable shitbox whilst its got a warranty.

[mik]

IDGaF about kettle wattage Mik, but tyres are an area of geeky interest to me

I didn't want to trigger your wrath (again)

[integrale_evo]

Tyres like everything the manufacturer chooses are a compromise. To say they know best on everything is a bit of an over simplification. They have to match grip, handling, balance, economy, noise, comfort, arch clearance etc.

You might stick to the same size but be ok running a completely different tread pattern and compound from whatever the manufacturer fitted, of do you stick to 100% oem at all times?

Do you buy the same brand of headlight bulb in as oem, would you never fit any ‘uprated’ parts like different bushes or springs?

I’m sure there are people out there that would have a heat attack if you suggested a different tyre size but will happily stick a set of oem size Linglongs on the front and Debicas on the back.

The oem tyres on an e36 M3 were the original Michelin pilot sport, I bet Michelin don’t make an exact equivalent now some 30 years later, and I bet if they did everyone would criticise them for their lack of grip. A ps5 is probably leagues ahead which then means they’re not going to be the same match to the suspension and brake specifications on the original car. I don’t see how that is much different than changing from the 225 45 17 to a 215 45 17 for example.

Not aimed at anyone in particular, just bored and it’s raining