Technical Considering changing tyre aspect ratio

[KHALED25]

I'm thinking about changing the stock tyres (205/55/16) to one with a slightly larger aspect ratio (205/60/16). The only reason I'm considering this is to increase comfort. The odometer and speedometer will be very slightly off, yes, but it's nothing major.

My question is: do you think this slightly bigger sidewall will actually make any notable difference when it comes to comfort, assuming I'll be using the same exact tyre type. Will the affect on handling be anything significant?

p.s. This link says the overall tyre length will increase by 20mm.

 

[Matthewr1990]

I'm thinking about changing the stock tyres (205/55/16) to one with a slightly larger aspect ratio (205/60/16). The only reason I'm considering this is to increase comfort. The odometer and speedometer will be very slightly off, yes, but it's nothing major.

My question is: do you think this slightly bigger sidewall will actually make any notable difference when it comes to comfort, assuming I'll be using the same exact tyre type. Will the affect on handling be anything significant?

p.s. This link says the overall tyre length will increase by 20mm.

It will make some difference yes, youve got more sidewall and more play in the tyre, ride will become softer. Pot holes will become more subtle as the tyre can mild to the shape better. The tyre going bigger will result in your speedo being under, this isn't so bad as the speedo is set slightly under anyway just absolutely make sure to stick to the speed limit or you may find yourself speeding. Your odometer will sah you are doing less miles than you actually are. 20mm doesn't seem a lot but multiply that by million rotations it starts to add up.
I can't see it being a big issue but I'll be honest I run the 16's on duty amid alloys and they're fine in my view.

 

[Fergie]

Comfort will improve, but you will loose handling.

Acceleration will be slightly slower, but may gain top end / mpg.

 

[KHALED25]

It will make some difference yes, youve got more sidewall and more play in the tyre, ride will become softer. Pot holes will become more subtle as the tyre can mild to the shape better. The tyre going bigger will result in your speedo being under, this isn't so bad as the speedo is set slightly under anyway just absolutely make sure to stick to the speed limit or you may find yourself speeding. Your odometer will sah you are doing less miles than you actually are. 20mm doesn't seem a lot but multiply that by million rotations it starts to add up.
I can't see it being a big issue but I'll be honest I run the 16's on duty amid alloys and they're fine in my view.

Comfort will improve, but you will loose handling.

Acceleration will be slightly slower, but may gain top end / mpg.

To be honest the difference in mpg and acceleration doesn't concern me. What I don't know is whether the difference in comfort will be big enough to warrant the change as I still need to find someone to give/sell my existing tyres to. The current wheels and tyres are good enough on normal roads but they can be easily disturbed by rough roads and potholes, and the easiest way I can think of to improve this is to increase the aspect ratio of the the tyres. I only recently replaced both front dampers but I've still not reached the level of comfort I'd like.

 

[F123C]

Hi, KHALED25
Have you considered 195/65 x 15 which I think was a standard size on the Bravo in some markets (but probably not on your T-Jet) + (no change to gearing).
IIRC this size wheel/tyre combination with the correct offset was fitted to some Stilo models.
Maybe you could find someone with this size tyre/wheel who would allow you to borrow his set (he could try your 16'' ones) and then you'd know for sure without any expense.
I don't think going up only one step in Aspect Ratio will give you enough extra comfort in relation to the cost incurred, plus you'll always be wondering if 2 steps in A/R would have been better?
I can appreciate you might want to stay with your 16'' wheels though!
Al.

 

[Ziggy122]

Simple - drop an inch size on the rims - this then allows for a bigger A/R

but i dont think 1 step would be different really

205
55% = 112.75mm
60% = 123mm

Ziggy

 

[KHALED25]

Hi, KHALED25
Have you considered 195/65 x 15 which I think was a standard size on the Bravo in some markets (but probably not on your T-Jet) + (no change to gearing).
IIRC this size wheel/tyre combination with the correct offset was fitted to some Stilo models.
Maybe you could find someone with this size tyre/wheel who would allow you to borrow his set (he could try your 16'' ones) and then you'd know for sure without any expense.
I don't think going up only one step in Aspect Ratio will give you enough extra comfort in relation to the cost incurred, plus you'll always be wondering if 2 steps in A/R would have been better?
I can appreciate you might want to stay with your 16'' wheels though!
Al.

To be honest I wouldn't consider downsizing the wheel size like you said. I like the stock one and I hate how the aftermarket ones look. 195/65/15 wheels would definitely be comfortable, but each of its dimensions will cause relatively worse handling than the stocks. I never saw 205/65/16 tyres before, but I know some cars like the mazda 3 use 205/60/16 so I should be able to find them. Whatever the size, I hope to find some continental tyres, as they offer the best comfort as far as I know.

The problem with switching/selling the tires wouldn't be about finding someone as much as it would be taking them back if I don't like them . My brother could take my current tyres as he is about the replace his car's tyres which are the same size, but there'll be no going back if I decide I don't like the new ones LOL.

Simple - drop an inch size on the rims - this then allows for a bigger A/R

but i dont think 1 step would be different really

205
55% = 112.75mm
60% = 123mm

Ziggy

It's only 10mm difference in sidewall length across each side, yes, so its 20mm in total. I'm afraid 2 steps would cause a big reduction in handling, but its going to be a compromise anyway. I was hoping this 1 step rise could strike a good balance.

 

[Matthewr1990]

How about taking a look at the springs instead? Might be cheaper, more reversible and get better results than spending £250+ on a set of 4 new tyres?

 

[KHALED25]

How about taking a look at the springs instead? Might be cheaper, more reversible and get better results than spending £250+ on a set of 4 new tyres?

I doubt any after market spring will be more comfortable than the stocks, right? After all, they only exist to make the ride "sportier". I was thinking the same when I changed my dampers a few weeks ago.

 

[Matthewr1990]

I doubt any after market spring will be more comfortable than the stocks, right? After all, they only exist to make the ride "sportier". I was thinking the same when I changed my dampers a few weeks ago.

Im sure you can buy more than just "sportier" springs.

 

[KHALED25]

Im sure you can buy more than just "sportier" springs.

To be honest I think the springs would be too much of a hassle. first I'll need to look around for some good aftermarket ones that are designed for comfort rather than handling. I'm not sure this even exists, but even if they do, they'll be much more expensive than a set of new tyres because i'll most probably have to ship them from overseas. The dealership will also ask for a good amount of money for the labor expenses. And finally, when I come to sell the car it'll cause its value to decrease significantly because it has aftermaket components (That's how the market is here.)

And to think that I always wanted to fit the bravo's 18inch wheels

 

[F123C]

Hi, KHALED25

What I was suggesting was to try to find someone with a Stilo with 195/65x15 tyres and swap (short-term) the wheels and tyres between their Stilo and your Bravo in order to see if the 65 profile tyres give you sufficient improvement in comfort/ride quality.
Sadly it appears that good ride quality on bumpy roads is being sacrificed by manufacturers of many smaller cars in the interest of giving a 'sporty' feel to the handling. Even going to a more expensive make may be no better, I've noticed BMW and others being criticized in car magazine roadtests for poor ride quality on other than billiard-table smooth surfaces, when you look at what tyres are fitted it often is something like 245/35x18 or worse!!
Ps. I feel your pain about cost of importing parts, here, in Ireland, the situation is the same, everything has to imported from the UK ,Europe or further afield and the final cost incl purchase tax of 23% can be prohibitive!!(and the parts are not being transported as far as is likely to reach your country)
Regards,
Al.

 

[KHALED25]

Hi, KHALED25

What I was suggesting was to try to find someone with a Stilo with 195/65x15 tyres and swap (short-term) the wheels and tyres between their Stilo and your Bravo in order to see if the 65 profile tyres give you sufficient improvement in comfort/ride quality.
Sadly it appears that good ride quality on bumpy roads is being sacrificed by manufacturers of many smaller cars in the interest of giving a 'sporty' feel to the handling. Even going to a more expensive make may be no better, I've noticed BMW and others being criticized in car magazine roadtests for poor ride quality on other than billiard-table smooth surfaces, when you look at what tyres are fitted it often is something like 245/35x18 or worse!!
Ps. I feel your pain about cost of importing parts, here, in Ireland, the situation is the same, everything has to imported from the UK ,Europe or further afield and the final cost incl purchase tax of 23% can be prohibitive!!(and the parts are not being transported as far as is likely to reach your country)
Regards,
Al.

I know you don't mean specifically a stilo and nothing else, but it wasn't sold here unfortunately. Remember that the bravo only has 4 bolts to hold the wheel and not many other cars have that. I know a friend who has a punto but it has 16 inch wheels as well.

You're right about manufacturers sacrificing comfort lately, but unfortunately this trend is extending into all car segments and not just the compact/small family segment. BMW, as you say, are notorious here for having exceptionally poor ride comfort because of their use of run-flat tyres. For example, their small crossover, the X1, comes standard with 18 inch runflat tyres, which are roughly as hard as dry concrete.

I'm not looking into any extreme or costly measure with this issue, so I think it's either going to be the 205/60/16 wheels or I just leave the car as is. I've asked around for 205/65/16 but no-one seems to have them (at least in continentals). I'm guessing only a cross-over would use such a size. The other option would be 215/60/16 but I don't really want wider tyres.

 

[F123C]

HI, KHALED25
Only other thoughts/suggestions are to lower the tyre pressures by say 2-4 psi (circa 0.15-0.3 bar) which can cause funny wear patterns on the tyres etc or maybe carry some extra weight e.g. a couple of bags of cement, in the boot/trunk if driving the car solo. I've noticed that when my Bravo is carrying 3 or 4 passengers the ride quality seems more acceptable.
PS I like your description of BMW run-flat tyres as being 'roughly as hard as dry concrete' !!!

Regards,
Al.

 

[rossocorsa]

I found that the ride is better with slightly higher pressures, as regards ride quality I suspect it is mainly down to under specified dampers which have to be set too stiff because they don't have adequate capacity have pondered changing to bilstein but they are very expensive. Overall I feel that there isn't enough roll stiffness but the dampers are too stiff in compression

 

[KHALED25]

HI, KHALED25
Only other thoughts/suggestions are to lower the tyre pressures by say 2-4 psi (circa 0.15-0.3 bar) which can cause funny wear patterns on the tyres etc or maybe carry some extra weight e.g. a couple of bags of cement, in the boot/trunk if driving the car solo. I've noticed that when my Bravo is carrying 3 or 4 passengers the ride quality seems more acceptable.
PS I like your description of BMW run-flat tyres as being 'roughly as hard as dry concrete' !!!

Regards,
Al.

I found that the ride is better with slightly higher pressures, as regards ride quality I suspect it is mainly down to under specified dampers which have to be set too stiff because they don't have adequate capacity have pondered changing to bilstein but they are very expensive. Overall I feel that there isn't enough roll stiffness but the dampers are too stiff in compression

I was about to say the exact same thing regarding tyre pressure. Its weird how it affects the ride comfort on this car. At first I used to set the pressure at 30 psi, and when I decided I wanted more comfort, I tried setting it on 27-28, and surprisingly the ride became worse. For some reason I tried increasing the pressure to 32-33 and it became noticeably better. When I increased it further to 35-36, it became very harsh so I figured around 32psi is the "sweet spot" for my conditions

Interestingly, the ride is indeed better when there's people riding along in the car, but unfortunately I usually drive by myself. I read before in a book around suspension that the damping properties are usually designed with the weight of 3 people in the car: 2 in the front and one in the center of the backseats, so maybe that's why the ride is better when someone is riding along.

It's weird (in a good way) that the giulietta, which is based on the bravo, has really good ride comfort even on 17 and 18 wheels according to all the reviews I've seen of it, whilst appearing to have much less roll and pitch. That fortunately goes against the trend @F123C was mentioning

 

[RobBravo]

I think that's because although the Giulietta shares many parts with the Bravo, suspension isn't one of them.

For a start, the Alfa has fully independent rear suspension vs the standard torsion beam on the Bravo.

On a side note, upgrading my suspension improved my ride. After going from a standard set up to a set of Eibach Pro (30mm)springs and Bilstein B4 shocks, coupled with 225/40/18s I would say overall the ride quality in regards to absorbing bumps may have even slightly improved.

I would be willing to bet my set-up is more comfortable than the sport set-up, judging by owners reviews of a "harsh ride".

Shortly I am going up set myself up on 225/45/17s which I feel will finally set up the car "just right" for me.

 

[KHALED25]

I think that's because although the Giulietta shares many parts with the Bravo, suspension isn't one of them.

For a start, the Alfa has fully independent rear suspension vs the standard torsion beam on the Bravo.

On a side note, upgrading my suspension improved my ride. After going from a standard set up to a set of Eibach Pro (30mm)springs and Bilstein B4 shocks, coupled with 225/40/18s I would say overall the ride quality in regards to absorbing bumps may have even slightly improved.

I would be willing to bet my set-up is more comfortable than the sport set-up, judging by owners reviews of a "harsh ride".

Shortly I am going up set myself up on 225/45/17s which I feel will finally set up the car "just right" for me.

Yup, I'm aware the giulietta has been overhauled in many aspects, but I'm surprised that there's such a big improvement in both comfort and handling. A big reason is that they used an aluminum alloy for the multi-link suspension in the rear. It also has a longer wheelbase and is very slightly wider. Its only downside is that the bravo has surprisingly more storage space, and a much better looking dash. If only there was a new bravo instead of the much higher priced giulietta .

Back to the topic, you might actually get a perfect balance between comfort and handling if you use 17" wheels, it just depends on the roads you drive in. The sidewall on the 225/45/17 is actually only a bit smaller than the one on the 205/55/16. I wouldn't be surprised either if your aftermarket springs and dampers gave you a better ride overall since I think they are undoubtedly of higher quality than the stocks. Are they adjustable though?

 

[rossocorsa]

Yup, I'm aware the giulietta has been overhauled in many aspects, but I'm surprised that there's such a big improvement in both comfort and handling. A big reason is that they used an aluminum alloy for the multi-link suspension in the rear. It also has a longer wheelbase and is very slightly wider. Its only downside is that the bravo has surprisingly more storage space, and a much better looking dash. If only there was a new bravo instead of the much higher priced giulietta .

Back to the topic, you might actually get a perfect balance between comfort and handling if you use 17" wheels, it just depends on the roads you drive in. The sidewall on the 225/45/17 is actually only a bit smaller than the one on the 205/55/16. I wouldn't be surprised either if your aftermarket springs and dampers gave you a better ride overall since I think they are undoubtedly of higher quality than the stocks. Are they adjustable though?

Our delta has longer wheelbase than bravo but same suspension, reviews generally say ride is good but tbh it isn't very good and is pants compared to a 30+ year old lancia beta in both ride and handling the main reason for that is I think inferior suspension design especially at the back and far too much reliance on electronic intervention as a cheap option instead of well engineered solutions (pretty much like most modern cars tbh)

 

[KHALED25]

Our delta has longer wheelbase than bravo but same suspension, reviews generally say ride is good but tbh it isn't very good and is pants compared to a 30+ year old lancia beta in both ride and handling the main reason for that is I think inferior suspension design especially at the back and far too much reliance on electronic intervention as a cheap option instead of well engineered solutions (pretty much like most modern cars tbh)

Problem is when you make a chassis that doesn't naturally resist roll and pitch movement well enough, you have to make up for it with stiff springs and dampers, which end up making the ride harsh. This is what happened with the bravo, and with the delta as well as you say (they use the same platform right?). When the chassis design itself(including suspension links) is rigid, it enables the manufacturer to use softer springs and dampers, so you get better comfort while making handling even better at the same time. The giulietta mainly achieved this with the use of the multi-link suspension in the rear instead of the torsion beam suspension of previous fiat group models. That's why one of the most advertised features any OEM mentions with a new platform is how much they increased its rigidity.