Explain tyres to me...
Discussion
I don't understand the codes. What do they mean?
Also, I've noticed that lower profile tyres seem to be more expensive than thicker profile tyres... Why? Surely, the thinner profile tyres would have less rubber going into their construction and thus should be cheaper.
What is the difference between winter and summer tyres, and why is that so? I can see the difference in tread, and that makes sense, but what's all this about 'compounds' and why do they matter?
Probably dumb questions
Also, I've noticed that lower profile tyres seem to be more expensive than thicker profile tyres... Why? Surely, the thinner profile tyres would have less rubber going into their construction and thus should be cheaper.
What is the difference between winter and summer tyres, and why is that so? I can see the difference in tread, and that makes sense, but what's all this about 'compounds' and why do they matter?
Probably dumb questions
http://lmgtfy.com/?q=sidewall+markings+explained
Sorry couldn't resist.
Some good questions actually.
Sorry couldn't resist.
Some good questions actually.
Edited by colonel c on Tuesday 26th July 21:18
As above it's not hard to look up.
The size markings consist of the width in mm, the sidewall height as a percentage of the width and the size of the rim they are designed to fit in inches. For example: 225/55R17 means the tread is 225mm wide, the sidewalls are 55% of 225mm high, and the tyre is designed to fit a 17 inch diameter rim. The "R" just means radial but all modern car tyres are radial. The sidewall also contains information on the date of manufacture, the noise levels, the wet grip levels, the maximum load and speed ratings, and a number of other things.
Lower profile tyres cost more primarily because they are usually fitted to more expensive cars so the people buying them are willing to pay more.
Winter tyres have two major differences from summer tyres; firstly they are made of a compound of rubber which stays softer at lower temperatures than summer tyres (the flip-side being that they wear more quickly at higher temperatures). They also have a different tread pattern - there are typically lots of small "sipes" which are fine grooves in the tyre designed to grip loose snow; they also have tread blocks which are designed to move around and generate heat as they flex.
The size markings consist of the width in mm, the sidewall height as a percentage of the width and the size of the rim they are designed to fit in inches. For example: 225/55R17 means the tread is 225mm wide, the sidewalls are 55% of 225mm high, and the tyre is designed to fit a 17 inch diameter rim. The "R" just means radial but all modern car tyres are radial. The sidewall also contains information on the date of manufacture, the noise levels, the wet grip levels, the maximum load and speed ratings, and a number of other things.
Lower profile tyres cost more primarily because they are usually fitted to more expensive cars so the people buying them are willing to pay more.
Winter tyres have two major differences from summer tyres; firstly they are made of a compound of rubber which stays softer at lower temperatures than summer tyres (the flip-side being that they wear more quickly at higher temperatures). They also have a different tread pattern - there are typically lots of small "sipes" which are fine grooves in the tyre designed to grip loose snow; they also have tread blocks which are designed to move around and generate heat as they flex.
Take 205/55R16 as an example.
The first number (205) is the width of the tyre in millimetres. The second figure is the size of the sidewall measured from the rim to the edge of the tyre and is a percentage of the width. So 55% of 205mm is 112.75mm. The R16 is the wheel size, in this case a 16" wheel.
You'll see a letter following this too such as H, W, ZR etc. This is the maximum speed of the tyre. H is 135mph, W is 150mph (I think), ZR is over 155mph.
Tyres tend to be cheaper due to batch sizes. A 205/55R16 is cheap because its used in many cars. A 295/30R20 might only use 50% more rubber but could cost five times the price because they sell 1% as many.
Tyres are made up of blocks in the tread pattern that are in contact with the road. These themselves are quite rigid in summer tyres which provide confidence when driving hard. Winter tyres have addition cuts in the tread blocks which provide more flexibility in the tyre and therefore better grip in snow. I understand they are made from a different compound too which can help in low temperatures (even if there is no snow). I notice winter tyres are much better driving through standing water too.
The first number (205) is the width of the tyre in millimetres. The second figure is the size of the sidewall measured from the rim to the edge of the tyre and is a percentage of the width. So 55% of 205mm is 112.75mm. The R16 is the wheel size, in this case a 16" wheel.
You'll see a letter following this too such as H, W, ZR etc. This is the maximum speed of the tyre. H is 135mph, W is 150mph (I think), ZR is over 155mph.
Tyres tend to be cheaper due to batch sizes. A 205/55R16 is cheap because its used in many cars. A 295/30R20 might only use 50% more rubber but could cost five times the price because they sell 1% as many.
Tyres are made up of blocks in the tread pattern that are in contact with the road. These themselves are quite rigid in summer tyres which provide confidence when driving hard. Winter tyres have addition cuts in the tread blocks which provide more flexibility in the tyre and therefore better grip in snow. I understand they are made from a different compound too which can help in low temperatures (even if there is no snow). I notice winter tyres are much better driving through standing water too.
colonel c said:
http://lmgtfy.com/?q=sidewall+markings+explained
Sorry couldn't resist.
Some good questions actually.
Sorry couldn't resist.
Some good questions actually.
Edited by colonel c on Tuesday 26th July 21:18
sorry! I knew it was a daft question but couldn't remember what they were called so couldn't bring up any decent explanations!To the others, thanks for that! Very useful to know.
So what is it that means cheaper tyres tend to not be as grippy as better tyres? Is it the softness of rubber?
Presumably harder tyres mean less grippy then?
TheInsanity1234 said:
So what is it that means cheaper tyres tend to not be as grippy as better tyres? Is it the softness of rubber?
Presumably harder tyres mean less grippy then?
If only it were that simple! Presumably harder tyres mean less grippy then?
High quality tyres last a long time, provide good grip and short stopping distances in both wet and dry conditions, handle well, roll quietly and efficiently, and they do all of this until they are worn beyond their useful life- during which they will not crack up, wear unevenly or go out of shape.
Mid range of budget tyres will trade off these qualities in one or more areas in favour of a cheaper price.
Or,
premium tyre brands are the ones that spend the most on advertising and corporate entertainment for motoring journalists. I've had some supposedly "premium" tyres that have been inferior to mid-range tyres in terms of grip.
However, I do now only choose A rated wet grip tyres for the family cars, such as Dunlop Sport Bluresponse or Goodyear efficient grip performance.
But even those names are cunningly crafted by marketing teams: they put in "efficient" and "blu" in there, but also "performance" and "sport", making you think you're getting the "perfect" all rounder tyre.
It's like "brand new recipe, same great taste" - it's just a meaningless marketing phrase to make people feel reassurred.
Looking at customer reviews might help? But who gets new tyres on their car and then goes round telling people "yes, these are definately worse than the last set". Very few I reckon, as most people are good at self justifying their choice, especially if they've paid top whack for them.
So, explaining tyres is as much about cutting through the marketing as it is understanding the codes.
Oh, and don't choose Arrowspeed (emergency choice by wife after 2 punctures). They were most definately worse than the previous set I had on the car.
Ian
premium tyre brands are the ones that spend the most on advertising and corporate entertainment for motoring journalists. I've had some supposedly "premium" tyres that have been inferior to mid-range tyres in terms of grip.
However, I do now only choose A rated wet grip tyres for the family cars, such as Dunlop Sport Bluresponse or Goodyear efficient grip performance.
But even those names are cunningly crafted by marketing teams: they put in "efficient" and "blu" in there, but also "performance" and "sport", making you think you're getting the "perfect" all rounder tyre.
It's like "brand new recipe, same great taste" - it's just a meaningless marketing phrase to make people feel reassurred.
Looking at customer reviews might help? But who gets new tyres on their car and then goes round telling people "yes, these are definately worse than the last set". Very few I reckon, as most people are good at self justifying their choice, especially if they've paid top whack for them.
So, explaining tyres is as much about cutting through the marketing as it is understanding the codes.
Oh, and don't choose Arrowspeed (emergency choice by wife after 2 punctures). They were most definately worse than the previous set I had on the car.
Ian
Ian Geary said:
premium tyre brands are the ones that spend the most on advertising and corporate entertainment for motoring journalists. I've had some supposedly "premium" tyres that have been inferior to mid-range tyres in terms of grip.
Hence I didn't say 'premium', but 'quality'Ian Geary said:
However, I do now only choose A rated wet grip tyres for the family cars, such as Dunlop Sport Bluresponse or Goodyear efficient grip performance.
Those ratings are to be taken with a pinch of salt. They are self-assessed by the manufacturer.Ian Geary said:
Looking at customer reviews might help?
Most customers don't know what they're talking about. Fortunately there are a ton of independent professional tyre reviews carried out by Autocar, ADAC etc etc.TheInsanity1234 said:
I don't understand the codes. What do they mean?
E.G 235/45R17 91V235 is the nominal section width expressed in millimetres. This is the width of the tyre from sidewall to sidewall.
45 is the aspect ratio (sidewall height) of the tyre expressed as a percentage (of the section width).
R is radial construction. Fabric body plies (polyester, rayon etc) that run in a radial direction in passenger car tyres.
17 is the diameter of the wheel fitement expressed in inches.
91 is the load index which corresponds with a certain load in KG (615kg)
Y is the speed index which corresponds with a maximum speed in MPH (150 mph)
TheInsanity1234 said:
Also, I've noticed that lower profile tyres seem to be more expensive than thicker profile tyres... Why? Surely, the thinner profile tyres would have less rubber going into their construction and thus should be cheaper.
Lower profile tyres have higher speed capabilites and require more reinforcement in the construction of the bead, belt packages etc to meet these speeds as well as carry the weight required. These are also typically within the sports segment so will invariably have more associated R&D costs for compound technology. This increases the cost.
TheInsanity1234 said:
What is the difference between winter and summer tyres, and why is that so? I can see the difference in tread, and that makes sense, but what's all this about 'compounds' and why do they matter?
Cold Weather tyres have two main differences over summer tyres. The first is the tread pattern. They are heavily siped (small cut like patterns in the tread) which aids traction on loose media such as snow and in wet weather. The other is the tread compound used. Cold weather tread compounds have a lower glass transition temerature which essentially means they stay pliable in cold conditions where normal summer compounds would lead to the rubber hardening and therefore, losing adhesion.
Typically, summer compounds work well to around 7 degrees C. Anything below that and cold weather tyres will have the edge - especially in wet weather which is what we tend to suffer with mst in the UK. Once you drive cold weather tyres in poor conditions, you'll wonder how you ever managed with normal summer tyres. The difference is night and day.
TheInsanity1234 said:
Probably dumb questions
Not at all. Any questions asked to educate yoruself about something so important will always be valid.Gassing Station | General Gassing | Top of Page | What's New | My Stuff