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I have read that the smaller tyre size gives a more comfortable suspension and ride. However, I do not understand why this is the case. I would be grateful if anyone could explain simply ( I'm not technical ) why and the relationship between tyre choice and comfort. Of necessity comfort is important in my choice of car.
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I think you mean smaller wheels, with the same overall wheel-tyre diameter.
If you make the wheel smaller (say from 18" to 15") then you have less solid metal and more flexible rubber (3" more in this example) to cushion the imperfections on the road.
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I think the issue may be wheel size where differing wheel/tyre combos are offered but with same rolling radius. Clutching at numbers model X may be offered with a 16 inch wheel and 70% profile tyre or 18 inch wheels with a much lower profile - eventually you end up with rubber bands.
The higher profile tyre has some flex in the sidewall at the expense of 'absolute' handling.
I'd be chary of very low profile tyres on a car for ordinary family use.
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When you mean 'size' do you mean profile, width or overall diameter?
Generally the lower the profile the less give in the sidewalls. Vehicle feels more planted but ride quality suffers. This is magnified by increase in width because there is greater contact with the road surface. Overall diameter makes no difference in straight line comfort but increases the ride height therefore the centre of gravity which can induce less stability on corners. Choosing is a compromise.
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>> When you mean 'size' do you mean profile, width or overall diameter?
>>
>> Generally the lower the profile the less give in the sidewalls. Vehicle feels more planted
>> but ride quality suffers. This is magnified by increase in width because there is greater
>> contact with the road surface. Overall diameter makes no difference in straight line comfort but
>> increases the ride height therefore the centre of gravity which can induce less stability on
>> corners. Choosing is a compromise.
>>
But suspension is usually designed to work most effectively with a given wheel size (diameter/profile/width), and there is usually an optimal size. I have experience of this effect on the two Saabs I own/have owned.
My old Saab 9-5, with sport suspension, rode better on 17" wheels fitted with 225 width tyres and a 45 profile - for the benefit of the OP, normally described as 225/45x17 - than on the 16" wheels fitted with 215/55 tyres. And on my current 9-5 Aero estate, I have 225/45x17s for the summer, and 205/55x16s for the winter. There's no difference, in my opinion, in ride quality. The 16" give the car slightly lighter steering, and make the car feel slightly less stable on fast motorway bends, but the actually ride quality is subjectively no different. I've been running this setup for some years, so it's not a recent observation over a couple of miles.
Not sure whether anyone has mentioned that, when bumps are absorbed by the tyre due to the extra rubber in higher profile tyres, rather than allowing the suspension to work, the absorption is undamped and can lead to bounce. Whether this is significant or not I can't say.
For the sake of accuracy, I should point out that all the tyres are XL (94) rated.
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Crudely, it's the amount of rubber between the road and you. Big wheels with thin tyres are less compliant than smaller wheels with thicker tyres to the same rolling diameter. And the low profile tyres are more expensive, sometimes absurdly.
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Yes its become clearer. I did mean wheel size but now realise tyre width and profile matter as well. Presumably once you choose a car you've no real choice as to tyre width - it must fit the wheel. I've no interest in bling : just safety and comfort. I haven't a clue what a tyre profile is and would appreciate an explanation. Thanks for the prompt and helpful posts. I've said before but people giving their time to help is appreciated.
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Tyre sizes/ratings are like this:
185/50 VR 16
185 = the width across the tyre in millimetres
/50 means the height of the tyre sidewall as a percentage of the width (from wheel rim to road) - 50% of 185mm = 92.5mm in this case
VR (or HR/ZR etc) is a rating that tells you the maximum speed the tyre is meant to run at - VR = 150mph, HR = 130mph.
16 = diameter in inches of the wheel the tyre is designed to fit.
Last edited by: Lygonos on Wed 5 Mar 14 at 22:38
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The other thing is that as tyre profiles get lower the tyre sidewall gets stiffer - so it ends up feeling like you're driving on iron rings rather than rubber tyres.
Often cars with very low profile tyres have XL (Extra Load) tyres - these have stiffer sidewalls again, and need to be inflated to higher pressures.
Last edited by: Bill Payer on Wed 5 Mar 14 at 23:01
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Pardon me for butting in after several glasses of red..but this is my take.
There's a hole on four corners of your car.
You can fill the hole by:
- A large wheel and small profile tyre
- An average wheel and average profile tyre
- A small wheel and large profile tyre
..and of course all sorts in between.
When I'm talking about the tyre profile, I mean the amount of tyre between the road and the wheel....and as you can only have so much filling the hole, you have to choose which wheel/tyre combination suits you.
Trouble is, the tyre manufacturers offer deals to the car manufacturers for the price of tyres..and they significantly discount the low profile ones..because they'll puncture and wear out quicker..and then you'll buy new ones.
If you want comfort, you want a high profile tyre..but..you need the wheels that go with it and the chances are the car when new was specced up with a larger wheel than was really necessary.
Many people think bigger wheels 'look nice'...so it's a case of style over substance.
Last edited by: Westpig on Wed 5 Mar 14 at 23:28
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>> Tyre sizes/ratings are like this:
>>
>> 185/50 VR 16
>>
>> 185 = the width across the tyre in millimetres
>>
>> /50 means the height of the tyre sidewall as a percentage of the width (from
>> wheel rim to road) - 50% of 185mm = 92.5mm in this case
To the original poster the larger the number after / = the more comfortable it is
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What everyone seems to be missing here is that it is the content of the tyre that is important.
Air suspension - fitted as standard on every car I have ever driven (apart from a friends pedal car)
The lower profile tyres stop this working as well as it could. You can compensate a little with spring/damper settings but not entirely.
Spring/Damper - primarily intended to keep the tyre in contact the road.
Air in tyre - primarily intended for comfort.
Next time you are near a train you will see that they also have two systems but the equivalent of the tyre is normally an air bag between the body and the bogie.
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I see the effect every day driving behind other cars as they go over the inumerable pot-holes, temporary road surfaces and "ramps" that are the essence of the modern road infrastructure.
The more modern the car and the lower profile the wheels, the slower the driver has to go to stop his car shaking to pieces.
The Volvo 240 justs flops comfortably over the holes and bumps. It's maddening though to have to be so vigilant for other cars that brake so abruptly for no apparent reason, and then go so slowly.
185/80 14 rules OK
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>>185/80 14 rules OK
No, it's not okay .. the 215/60 16 jobbies on my Sub sail o'er 'pot' holes & bumps better than my 240 GLT ever did.
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Thanks everyone - your time and advice are appreciated. Its better than the Open University !
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>> No, it's not okay .. the 215/60 16 jobbies on my Sub sail o'er 'pot'
>> holes & bumps better than my 240 GLT ever did.
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Well, you may well be right in many instances. I'm only observing how I see it.
People in big 4WDs crash over them regardless, and people in ordinary small cars with what I presume must be low-profile tyres drive ultra-cautiously as if their car was an eggbox with a precious load.
And then complain on forums like this that their car has a hard ride.
A friend we gave a lift to in the Triumph recently said it was the most comfortable car she had ever riden in, miles better than her focus or astra or whatever it was.
(Anyway, don't the GLTs have beefed up suspension with lower profile tyres? It's a harder ride than the usual sloppy 240 feel. I know why - for better road-holding - I'm not disputing that)
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Subaru Forester is rather well screwed together AWD estate car of course rather than a big 4WD.
>>(Anyway, don't the GLTs have beefed up suspension with lower profile tyres?
Yep.
>>It's a harder ride than the usual sloppy 240 feel
Yep, I used to compare it to a friends common-or-garden 240, and that was a totally different kettle of fiche.
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Tyres size relationship to comfort - Lygonos
