Winter tires doubt

[Andrea]

Hi all, as per last update from the deal I should take delivery of my Emira in Jan 2023 (not that I believe him, but...), since I want to buy winter tires bring to be always on the safe side I've been checking what would be best for the car, after some research I've noticed that lotus, in the official Emira hand book, recommends Michelin Pilot Alpin 235/35 ZR20 front and 285/30 ZR rear (attached a picture of the page stating this).

Given that, for summer tires, they recommend Goodyear Eagle F1 Supersport 245/35 ZR20 front and 195/30 ZR20 rear I don't get why we should get smaller tires for winter.

Shouldn't be better to stick with the summer tire sizes using, for example, Continental TS 860 S?

I really don't get why the size difference, it's a sport car, we won't dig into the snow.....maybe someone could help me on this matter that could be of any help also for thers!

Thank you and sorry for my English, it needs improvements

PS according to the italian Michelin website front tires would be Pilot Alpin 4 whereas the rear ones would be Pilot Aplin 5....even different types, more and more strange to my eyes

 

[Max]

You want a narrower profile tire if you're going through snow.

 

[VL3X]

10mm isn't that much of a difference, especially between Michelin winters and Goodyear summer tires. It's been my experience that different manufactures measure their widths slightly differently or at different points. For instance, I've have 245 Firestone Indy 500s and 245 PS4S and the PS4S were wider. So I guess some just "run narrow" like shoes?

 

[Nova]

I am considering getting winter wheels - this is usually how I run my cars instead of changing tires twice a year. It's less about the cost, but more about avoiding damage to the wheels due to frequent tire changes, and inconvenience. However, I would like to run one size smaller wheels in the winter, using 19 inch wheels. Do we know if there will be clearance issues?

 

[Andrea]

10mm isn't that much of a difference, especially between Michelin winters and Goodyear summer tires. It's been my experience that different manufactures measure their widths slightly differently or at different points. For instance, I've have 245 Firestone Indy 500s and 245 PS4S and the PS4S were wider. So I guess some just "run narrow" like shoes?

That’s what I though! Since the difference is basically…nothing, why don’t they stick to the original measure?

this makes me think there must be some other reason we are not getting.

Relatively a clearance difference between summer and winter tires perhaps? Just guessing

 

[VL3X]

That’s what I though! Since the difference is basically…nothing, why don’t they stick to the original measure?

this makes me think there must be some other reason we are not getting.

Relatively a clearance difference between summer and winter tires perhaps? Just guessing

Maybe that size just isn't offered or its a special order spec and would cost much more so they recommended the more common width.

 

[Andrea]

Maybe that size just isn't offered or its a special order spec and would cost much more so they recommended the more common width.

Mmmmmmmmmmmm

To be honest the only set I've found of winter tires with summer sizes are Continental's, probably when they wrote the handbook they weren't available yet and, as you stated, they wrote the only sizes available at that time for winter tires.

Does it make any sense?

It think something similar happened when the BMW M3 E92 was released, during the first months there were no winter tires of the same size as the summer's

 

[lion shf]

10mm isn't that much of a difference, especially between Michelin winters and Goodyear summer tires. It's been my experience that different manufactures measure their widths slightly differently or at different points. For instance, I've have 245 Firestone Indy 500s and 245 PS4S and the PS4S were wider. So I guess some just "run narrow" like shoes?

Firestone 500s, you really are a true VAG man

 

[Porter]

The difference is likely due to rolling circumference. The winter tires will have a taller/deeper tread than the sport tires, and there is variation in how they handle this from manufacturer to manufacturer. The split is between strategically undersizing the tire carcass on deeper tread tires, vs accepting a variation in rolling circumference between different tire models of the same nominal size.

In this case, that size of that particular tire is most likely the closest match that maintains acceptable speedometer accuracy, and also fits the wheel size.

 

[Andrea]

The difference is likely due to rolling circumference. The winter tires will have a taller/deeper tread than the sport tires, and there is variation in how they handle this from manufacturer to manufacturer. The split is between strategically undersizing the tire carcass on deeper tread tires, vs accepting a variation in rolling circumference between different tire models of the same nominal size.

In this case, that size of that particular tire is most likely the closest match that maintains acceptable speedometer accuracy, and also fits the wheel size.

I didn't know winter tires have a deeper tread, your theory makes a lot of sense to me but are 10mm difference of width such big deal? Probably, but just guessing, if it is only a matter of speedometer accuracy I'd rather choice larger tires...does it make sense?

 

[Porter]

I didn't know winter tires have a deeper tread, your theory makes a lot of sense to me but are 10mm difference of width such big deal? Probably, but just guessing, if it is only a matter of speedometer accuracy I'd rather choice larger tires...does it make sense?

It's not the width that they are correcting for, but the tire's rolling radius.

In the Tire Code the first number is the section width in millimeters, and the second number is the height of the sidewall as a percentage of the section width.

So a 235/35 and a 245/35 (both on the same wheel) have two different sidewall heights, and thus different rolling radius.

The 235/35 sidewall is ~82.25mm tall, and the 245/35 sidewall is ~85.75mm tall, at least nominally. Sidewall measurement doesn't always correct for tread depth.

What I'm suggesting is that when the tread depth is accounted for, these may be very close or equivalent between the two (very different) types of tires.

 

[Andrea]

It's not the width that they are correcting for, but the tire's rolling radius.

In the Tire Code the first number is the section width in millimeters, and the second number is the height of the sidewall as a percentage of the section width.

So a 235/35 and a 245/35 (both on the same wheel) have two different sidewall heights, and thus different rolling radius.

The 235/35 sidewall is ~82.25mm tall, and the 245/35 sidewall is ~85.75mm tall, at least nominally. Sidewall measurement doesn't always correct for tread depth.

What I'm suggesting is that when the tread depth is accounted for, these may be very close or equivalent between the two (very different) types of tires.

Thanks for the clarification, your contribution enlight a new interesting perspective on the matter!

I was wondering, given your calculation based on the 10mm wider tires and therefore the taller sidewall plus the deeper treads, how much could the difference be, if it would really be that big deal and if it would make sense to stick with the wider measures anyway comparing all the lossess and all the gains on both options

 

[Porter]

Thanks for the clarification, your contribution enlight a new interesting perspective on the matter!

I was wondering, given your calculation based on the 10mm wider tires and therefore the taller sidewall plus the deeper treads, how much could the difference be, if it would really be that big deal and if it would make sense to stick with the wider measures anyway comparing all the lossess and all the gains on both options

I doubt it would make any difference from a driving perspective. It's winter use, after all, so you aren't going to be cornering at high lateral G. The primary difference would be in speedo accuracy... if the tire height increases, your speedo will read low. If the tire height decreases, your speedo will read high.

 

[Time2Fly]

Michelin doesn't list the rear size tire available in the US in the PA4.