Increasing tyres a letdown?

[Bper]

If increasing the tyre size from the original spec has negative effects, are any of these ever taken into account before the change.

According to studies and tests undertaken, if you go from a 15” to 19” wheel, you will experience a 10% decrease in fuel economy with city driving. On top of that, a 4% loss in 0-60 acceleration times. 

Fuel economy likely suffers because your engine will have to work harder to move the extra weight, and wider tyres will increase drag and friction, which reduces efficiency. 

[Derek.w]

A good point larger wheels tyres will last longer in miles.

[Catlover]

Larger tyres tend to cost a lot more.

[FROSTYBALLS]

They can also adversely affect the speedometer reading. Eg it is ilegal for speedometer to under-read and can only over-read within certain limits.

There are online tyre  checkers that will determine how a change in size affects  speedometers.

[Bper]

56 minutes ago, FROSTYBALLS said:

They can also adversely affect the speedometer reading. Eg it is ilegal for speedometer to under-read and can only over-read within certain limits.

There are online tyre  checkers that will determine how a change in size affects  speedometers.

Do drivers actually understand these problems or are they ignoring them because they are led to believe that it's just about a better ride with no other mention of any issues 

[FROSTYBALLS]

35 minutes ago, Bper said:

Do drivers actually understand these problems or are they ignoring them because they are led to believe that it's just about a better ride with no other mention of any issues 

Can't say for most, but those who post queries on these forums are usually made aware of some of the issues.

[Bper]

Many posts have been made regarding tyre size upgrading but very little has ever been mentioned on the negative effects of doing so . Does the lack of discussion on these effects reflect the lack of information in various car media. If drivers had this information would they still do the change or if they were looking for a more comfortable ride would they look at a car that offers this.
 

[Markyswan]

I know a few guys that have changed tyres for larger but never heard anyone talk about the negative side of doing this. I never realised it could be a problem. Thanks for that bob.

[Cyker]

Well in our cases the overall size of the wheel is the same - Smaller rim is off-set by more sidewall, so won't affect the speedo enough to matter.

It gets more complicated if you start changing the overall diameter of the wheel, as that's there things like the speedo become an issue, but for what we're doing it's negligible.

Within that, smaller rim means less mass and a shorter moment/momentum arm, which means better acceleration and braking but limits brake caliper size. It also means the corresponding tyre has more sidewall which means more shock absorption, but also flex, which will heat up the tyre faster and dampen impacts but also steering feel. Tyres for bigger rims have less sidewall which mean less flex and movement, translating to better steering feel, but also less margin between impacts and the actual rim. The extra mass and longer moment-arm of the bigger rim also give them a larger fly-wheel effect, which can be better for constant speed distance cruising.

The next thing is the tyre width - Wider tyres have longer life but more rolling resistance and aero drag (Due to being wider - They present more 'face' to the oncoming air than skinny tyres.). The lower wear rate means softer, grippier compounds can be used without tyre life becoming a joke, and the larger contact surface helps grip in the dry. However, in the wet and other inclement surfaces, because the weight of the car is spread over a wider area, wider tyres are more prone to skating over the top of aquaplaning, whereas narrower tyres tend to cut through to the tarmac as the weight is focused on a smaller contact patch, although these days advances in tread pattern design have made the difference a lot less.

 

[Bper]

21 hours ago, Cyker said:

Well in our cases the overall size of the wheel is the same - Smaller rim is off-set by more sidewall, so won't affect the speedo enough to matter.

It gets more complicated if you start changing the overall diameter of the wheel, as that's there things like the speedo become an issue, but for what we're doing it's negligible.

Within that, smaller rim means less mass and a shorter moment/momentum arm, which means better acceleration and braking but limits brake caliper size. It also means the corresponding tyre has more sidewall which means more shock absorption, but also flex, which will heat up the tyre faster and dampen impacts but also steering feel. Tyres for bigger rims have less sidewall which mean less flex and movement, translating to better steering feel, but also less margin between impacts and the actual rim. The extra mass and longer moment-arm of the bigger rim also give them a larger fly-wheel effect, which can be better for constant speed distance cruising.

The next thing is the tyre width - Wider tyres have longer life but more rolling resistance and aero drag (Due to being wider - They present more 'face' to the oncoming air than skinny tyres.). The lower wear rate means softer, grippier compounds can be used without tyre life becoming a joke, and the larger contact surface helps grip in the dry. However, in the wet and other inclement surfaces, because the weight of the car is spread over a wider area, wider tyres are more prone to skating over the top of aquaplaning, whereas narrower tyres tend to cut through to the tarmac as the weight is focused on a smaller contact patch, although these days advances in tread pattern design have made the difference a lot less.

 

Cyker, thank you for that but do you think you could explain your post in more detail, 😅

On a more serious note do you think that drivers are generally aware of the negative effects tyre upgrades can have.?

[Roy124]

Bob, on your second point, it's a yes and a no. 

The traditional, or noticeable, upgrade (?) of smaller diameter but wider wheels, wider wings larger exhaust pipe do it as a fashion statement.  

Those who look to change for other reasons, and often for the OEM alternative fit for the same model probably weight up the pros and cons. 

[Cyker]

34 minutes ago, Bper said:

Cyker, thank you for that but do you think you could explain your post in more detail, 😅

On a more serious note do you think that drivers are generally aware of the negative effects tyre upgrades can have.?

I think most drivers don't even know you can change the rim or tyre sizes from what it comes with!!

The ones that do tend to be more in the enthusiast bracket and I'd hope would be more clued up, although there seems to be a general pervading opinion that Bigger rims and lower profile tyres always = "Better"

[APS]

Ever bigger wheels on ever bigger cars. It doesn't make sense - but it sells.

 

[Mojo1010]

It's individual cases really. Most people don't even know about changing sizes of tyres and wheels. Have increased tyre width of 10-20mm in a few cars in the past and it's very positive (also felt the need to). As highlighted, actual speed cannot under read and also to inform insurance. I know the sizes of tyre i want or as close to from the way the car perform to suit my driving needs while staying within the law. 

https://tiresize.com/calculator/

[Bper]

24 minutes ago, Roy124 said:

Bob, on your second point, it's a yes and a no. 

The traditional, or noticeable, upgrade (?) of smaller diameter but wider wheels, wider wings larger exhaust pipe do it as a fashion statement.  

Those who look to change for other reasons, and often for the OEM alternative fit for the same model probably weight up the pros and cons. 

Hi Roy, I was chatting to three car owners today and all of them thought there wasn't any  problems with upgrading tyres. However what was also concerning was the idea that mismatched tyres on a car was also OK. 

I just think more information should be put out about the pitfalls regarding tyre upgrades. I didn't really understand much about this until I read how this can affect the handling and wear on other parts of the car. Glad I know a little bit now.👍

[Roy124]

Bob, not only that, but how many people actually look at options, noise, comfort, grip, economy, all part of a tyre specification or just go for ££? 

I used to go for Pirelli as a default (years ago) as I could not really afford Michelin.  Buying new cars now I find it disappointing that I get what's given though I am happy with the Goodyear fitted to the Yaris Cross. 

As I am older I am more concerned with comfort, noise and ride, rather than the stiction between road and tyre as I go max G slaloms around country lanes. 

 

[Cyker]

Shoutouts to the TyreReviews website for more tyre information and reviews than you'd ever want to have  

 

[Bper]

9 hours ago, Roy124 said:

Bob, not only that, but how many people actually look at options, noise, comfort, grip, economy, all part of a tyre specification or just go for ££? 

I used to go for Pirelli as a default (years ago) as I could not really afford Michelin.  Buying new cars now I find it disappointing that I get what's given though I am happy with the Goodyear fitted to the Yaris Cross. 

As I am older I am more concerned with comfort, noise and ride, rather than the stiction between road and tyre as I go max G slaloms around country lanes. 

 

Roy I think you are right, Many drivers opt for the cheapest tyres without any thought to the effects this can have on the car. The used car market being the obvious. Many of these cars have different makes of tyres on but budget plays the main part for many.

Understand needing comfort when you get older that's for sure.😅

 

[Bper]

2 hours ago, Cyker said:

Shoutouts to the TyreReviews website for more tyre information and reviews than you'd ever want to have  

 

Never underestimate the power of forum's. 😂

[Bper]

Upgrading tyres can damage suspension if driven aggressive. Would you upgrade and risk this happening or not be to concerned. 

[Mojo1010]

Do you mean going bigger tyres as upgrading? I don't see going bigger on tyres necessarily as an upgrade. If going too wide then it could rub against wheel arch or the wheel cannot take the size. 

No damage to my previous cars suspension by going 10-20mm wider. It was within the manufacturers spec. It also can be outside of manufacturer spec and still be fine as long as u do the research. 

[Bper]

Hi MoJo, yes upgrading or upsizing is the same thing really. When you upgrade your current set of wheels either by putting on wider tyres or bigger wheels, it is known as upsizing which you probably already know.

Cars with upsized tyres tend to have a heavier steering. This is due to the added weight of wider tyres and even wider wheels in some cases. This could impact the precision of your steering, thereby altering the handling characteristics.

Choosing an ideal tyre upsize.

This is the area where most people make mistakes. Just because a tyre seems bigger doesn’t mean it is good for your car. Upsizing is a very critical change to a car and must be done with utmost care. An upsize is good for your car only if the resultant diameter difference is less than or equal to three per cent.

Upsized tyres not only lead to more wear and tear for your tyres but also your car. A car's suspension is designed for a specific rim size and when you upsize the tyres, the dynamics of the suspension change too.

There are numerous articles on tyre upsizing which highlight both positive and negative effects this can have on the car. It is true that choosing a tyre that is within the manufacturers specifications can have benefits but the point I have been making is not everyone understands the pitfalls of incorrect tyre and wheel choice. This is a very critical decision that drivers like myself had not been fully aware of.

I believe that discussions on this particular subject highlight potential dangers and pitfalls from tyres to other issues like brakes etc., can not only help members who are not as clued up as others but can ultimately save them money and time but more importantly potentially save lives.👍

[Mojo1010]

Upgrading means better for me, though upsizing in tyres doesn't necessarily means better, that was my point. 

You are putting a little too much emphasis on extra weight, it's minimal, and steering actually is more planted with wider tyres, provided one don't go crazy on width, as they provide better grip. Wider tyre have more grip, better braking and last longer. Also car isn't specific to one rim or tyre size to perform ok, or other setups will make it very horrible. We are talking about a standard car, not a track racing car that needed to be set up optimally. 

You have done some reading on the subject good, only once u have the experience of say going a bit wider 10-20mm, then you will understand the fuss is about nothing and the car is performing a lot better than before on narrow tyres. You may not ever need to go wider or bigger wheels if you are happy with its current setup.  

 

[Markyswan]

On 2/11/2023 at 7:43 PM, Mojo1010 said:

Upgrading means better for me, though upsizing in tyres doesn't necessarily means better, that was my point. 

You are putting a little too much emphasis on extra weight, it's minimal, and steering actually is more planted with wider tyres, provided one don't go crazy on width, as they provide better grip. Wider tyre have more grip, better braking and last longer. Also car isn't specific to one rim or tyre size to perform ok, or other setups will make it very horrible. We are talking about a standard car, not a track racing car that needed to be set up optimally. 

You have done some reading on the subject good, only once u have the experience of say going a bit wider 10-20mm, then you will understand the fuss is about nothing and the car is performing a lot better than before on narrow tyres. You may not ever need to go wider or bigger wheels if you are happy with its current setup.  

 

Do you only have to worry about weight if you only drive a high performance car .

[Mojo1010]

I would say even less so as the car has power, weight is less of an issue. 

So my current car is on 185/60/15, if I were to go 205/45/18 (GR sport Yaris) and the car can take that size then weigh will be an issue.