Low profile tyre advantages/disadvantages

[iloveboost]

Hi I've always wondered what are the advantages of low profile tyres other than (to me) better looks. There's a chart on 'Car & Driver' for example where they went from a 225/45/17 to a 225/40/18 and from 0.85g to 0.89g on a skidpad in a Golf. As a wheel is meant to weigh more a tyre in terms of diameter I want to know why?

I've got a few ideas:
Less sidewall and tread stretch (slip angle?) when cornering=less heat gain (although less sidewall area means less cooling?).

Therefore temperature is more stable and that means less tyre wear so a softer rubber compound can be used? I'd imagine this also makes pressure more stable which means the tyre contact patch is more even?

Low profile tyres seem to be better for ultimate grip but add more weight. I wonder though is a low profile narrower tyre better than a high profile wider tyre with the same grip level? Especially if you have to use a wider wheel then I imagine low profile/high profile tyres become more about your own preference?

Thanks.

[HertsBiker]

Lower profile is more grip in the dry, but I feel less in the wet or snowy, low profile is also horribly prone to tramlining and kerb damage. On balance, I prefer about 50 section or greater. Also cost is huge factor. Tread pattern very limited in the lower sections. I can't actually see the benefit now I look at it.

[HaloGen8]

Pros: Handling and looks.

Cons: Potholes are your enemy.

[chris watton]

HertsBiker said:

Lower profile is more grip in the dry, but I feel less in the wet or snowy, low profile is also horribly prone to tramlining and kerb damage. On balance, I prefer about 50 section or greater. Also cost is huge factor. Tread pattern very limited in the lower sections. I can't actually see the benefit now I look at it.

Absolutely.

I just had my wheels re-painted in shadow chrome on my Tamora, and a dropped kerb just caught the very edge of the wheel rim! Ridiculous. When I change the front tyres, I'm going for 225/40, rather than the 225/35's - there's less than 2" from road to wheel rim!

Great for track days, but bordering on not fit for purpose on the UK roads today.

Edited by chris watton on Tuesday 1st July 19:53

[iloveboost]

HertsBiker said:

Lower profile is more grip in the dry, but I feel less in the wet or snowy, low profile is also horribly prone to tramlining and kerb damage. On balance, I prefer about 50 section or greater. Also cost is huge factor. Tread pattern very limited in the lower sections. I can't actually see the benefit now I look at it.

I agree with you that anything below about a 50 profile is more easily damaged abd they tend to follow bumps in the road more whilst jiggling the wheel.
I wonder if in theory you should use the largest tyre profile that allows enough space for the brake discs?
I mean is that what engineers would prefer?
The other thing I forgot to mention is that I think a tyre acts like an undamped spring? I'm guessing this effect is greater with a high profile tyre and less with a low profile tyre?

[balls-out]

HaloGen8 said:

Pros: Handling and looks.

Cons: Potholes are your enemy.

From my side I would argue that low profile are bad for handling. They will grip more, but there is less 'feel' and break-away at the limit is usually more sudden.

Low profiles do allow a bigger wheel for the same rolling radius, which in turn allows room for huge discs required due to the modern car bloat.

[aka_kerrly]

balls-out said:

From my side I would argue that low profile are bad for handling. They will grip more, but there is less 'feel' and break-away at the limit is usually more sudden.

Low profiles do allow a bigger wheel for the same rolling radius, which in turn allows room for huge discs required due to the modern car bloat.

Agree.

Generally speaking I like a 45 profile on a rim no more than 1 inch larger than factory or larger if it for brakes. Although you can fit 312mm brakes behind 16 inch wheels and for most road cars that is easily enough braking power!

[g3org3y]

Recently changed from 205/50 R16 (winters) to 225/45 R17s (summers) on the E36.

Improved:
- turn in 'bite'
- overall grip
- feels more stable mid corner
- looks (subjective!)

Worse:
- ride comfort
- tramlining
- road noise at motorway speed.

For general driving the 16s were the better balance between comfort and handling. Once the new tyres are worn, would be very interested in going back down to 16s for summer too.

I'd hate to think what cars running 19s/20s must be like.

[Rawwr]

balls-out said:

From my side I would argue that low profile are bad for handling. They will grip more, but there is less 'feel' and break-away at the limit is usually more sudden.

Low profiles do allow a bigger wheel for the same rolling radius, which in turn allows room for huge discs required due to the modern car bloat.

Agree. Although brakes are all well over-engineered and I'm fairly sure that most modern hatchbacks don't need 600mm discs with callipers that look like a Decepticon's vagina to bring them to a timely stop. Chunky sidewalls all the way for me, please.

[Monty Python]

Rawwr said:

Agree. Although brakes are all well over-engineered and I'm fairly sure that most modern hatchbacks don't need 600mm discs with callipers that look like a Decepticon's vagina to bring them to a timely stop. Chunky sidewalls all the way for me, please.

Which hatchback has 600mm discs? That's nearly 24 inches!

[aka_kerrly]

Monty Python said:

Rawwr said:

Agree. Although brakes are all well over-engineered and I'm fairly sure that most modern hatchbacks don't need 600mm discs with callipers that look like a Decepticon's vagina to bring them to a timely stop. Chunky sidewalls all the way for me, please.

Which hatchback has 600mm discs? That's nearly 24 inches!

I overlooked that error on the basis that " a Decepticon's vagina" is a bizarrely funny remark

[Rawwr]

Monty Python said:

Rawwr said:

Agree. Although brakes are all well over-engineered and I'm fairly sure that most modern hatchbacks don't need 600mm discs with callipers that look like a Decepticon's vagina to bring them to a timely stop. Chunky sidewalls all the way for me, please.

Which hatchback has 600mm discs? That's nearly 24 inches!

It was clearly an exaggeration

[8bit]

If we're talking about the same car (i.e. changing tyre profile and/or wheel diameter on one car) then you will probably feel a harsher ride and possibly notice more tramlining. These are not the only factors though - my Jaguar has 20" rims and 35/30 (front/rear) profile tyres but it rides infinitely better than my old SEAT Leon Cupra R did on 18" 40 profile tyres. That's using the same tyres on both cars.

The common assumption that anything on low profile tyres and/or bigger wheels will just ride harshly doesn't always hold; suspension design and configuration play a bigger part in this.

If you just want to increase sidewall stiffness (so increasing handling precision at the expense of a little ride comfort) then choose different tyres; a bit of research should dig up which brands/models of tyres have stiffer or softer sidewalls. Vredestein Ultrac Sessantas are quite stiff but not harsh.

[iloveboost]

8bit said:

If we're talking about the same car (i.e. changing tyre profile and/or wheel diameter on one car) then you will probably feel a harsher ride and possibly notice more tramlining. These are not the only factors though - my Jaguar has 20" rims and 35/30 (front/rear) profile tyres but it rides infinitely better than my old SEAT Leon Cupra R did on 18" 40 profile tyres. That's using the same tyres on both cars.

The common assumption that anything on low profile tyres and/or bigger wheels will just ride harshly doesn't always hold; suspension design and configuration play a bigger part in this.

If you just want to increase sidewall stiffness (so increasing handling precision at the expense of a little ride comfort) then choose different tyres; a bit of research should dig up which brands/models of tyres have stiffer or softer sidewalls. Vredestein Ultrac Sessantas are quite stiff but not harsh.

You see this is what I was thinking. Reason is I read an old article on when they first introduced radial tyres. I think the main advantages were that they ran cooler so they lasted much longer and because they flexed less they gripped much better with better transitional response.

Many car manufacturers hated them at first because despite the advantages the ride quality, bump steer and on the limit handling was horrible with the current cars they had.
Then I think one car company tried re-designing the suspension of one of their cars. They did things like added more caster, re-designed the steering rack for a slower turn in and less bump steer. They also softened the suspension bushes.
They then re-tested the car and it rode as well as it had done on bias ply tyres, but handled far better. Now there were no real disadvantages to radial tyres and other manufacturers did the same. Soon people realised that radials rode as well but lasted many times longer than bias ply tyres so bias ply tyres became obsolete.

I'm thinking if you're a manufacturer you just design suspension with more caster, less bump steer and softer suspension bushes for low profile tyres and most of the problems go away? I think if the car rides harshly that's just because of the spring rate being too high so it's 'sporty'. Or if the car uses run flats that means firmer damping is needed to control the extra unsprung weight?