Acceptable Tyre size

[ride_comfort_is_my_object]

I'm a newbie on here, so permission granted to slap me up to forum spanner manners.

The car is a ford focus mk2 (preface lift) 2005 2L Automatic.

It has 16" alloys with 205/55 tyres as per the manual spec.

The car only is used around town and 50mph is all it ever gets to dream of hitting.

Really would like a more comfortable soft drive and looking at putting either 185/65 or 195/65 on the 16" alloys.

Will this make a noticeable difference to the speedometer and how about stopping distance?

Is this a good idea or not, feel free to enlighten me as to why this is a good or bad move?

[F0CUE]

A list of alternative sizes to the 205x55x16

 

[Luke4efc]

3 hours ago, ride_comfort_is_my_object said:

Really would like a more comfortable soft drive and looking at putting either 185/65 or 195/65 on the 16" alloys.

Will this make a noticeable difference to the speedometer and how about stopping distance?

Is this a good idea or not, feel free to enlighten me as to why this is a good or bad move?

You're not gaining anything by narrowing the width of the tyre and increasing the profile. The "55" profile is just 55% of the 205. By going to "60", that would be 60% of 185, which is pretty much the same value of around 112mm.

If you left the width at 205 and increased the profile to 60, then you will have increased the overall circumference of the wheel, which will throw the speedo out by a few mph.

The only way to get a bigger profile (and not affect the speedo) is to make the rims smaller.

Wider tyres will (in theory) have better stopping power, as there is more contact area with the floor. In reality an extra 10mm won't make much difference on a bog standard car.

I also wouldn't recommend fitting narrower tyres to fatter rims as stretching tyres is not the safest thing to do.

[fiestaecoboostman]

Think about all the threads where people complain how bumpy 19" rims are, and how the car rode better on 18's. Both with have the same overall circumference, just that the smaller wheels will have a deeper sidewall for a more cushioned ride. You could consider fitting extra load tyres for a stiffer sidewall next time you change your rubber if its bumps and potholes banging, but in all honesty it's only a small difference.

[ride_comfort_is_my_object]

On 9/17/2021 at 5:59 PM, F0CUE said:

A list of alternative sizes to the 205x55x16

 

Thanks Ian.  Soooooooo, I could get 195/60/R16 the next tyre change.

[ride_comfort_is_my_object]

On 9/17/2021 at 9:55 PM, Luke4efc said:

You're not gaining anything by narrowing the width of the tyre and increasing the profile. The "55" profile is just 55% of the 205. By going to "60", that would be 60% of 185, which is pretty much the same value of around 112mm.

If you left the width at 205 and increased the profile to 60, then you will have increased the overall circumference of the wheel, which will throw the speedo out by a few mph.

The only way to get a bigger profile (and not affect the speedo) is to make the rims smaller.

Wider tyres will (in theory) have better stopping power, as there is more contact area with the floor. In reality an extra 10mm won't make much difference on a bog standard car.

I also wouldn't recommend fitting narrower tyres to fatter rims as stretching tyres is not the safest thing to do.

Could we agree that by narrowing the tyre I am reducing the grip slightly, by increasing the wall height I am improving the ride comfort slightly..?

[ride_comfort_is_my_object]

On 9/19/2021 at 6:14 PM, fiestaecoboostman said:

Think about all the threads where people complain how bumpy 19" rims are, and how the car rode better on 18's. Both with have the same overall circumference, just that the smaller wheels will have a deeper sidewall for a more cushioned ride. You could consider fitting extra load tyres for a stiffer sidewall next time you change your rubber if its bumps and potholes banging, but in all honesty it's only a small difference.

 

Sounds a good idea, but would stiffer walls equal stiffer ride...?

[Luke4efc]

22 minutes ago, ride_comfort_is_my_object said:

Could we agree that by narrowing the tyre I am reducing the grip slightly, by increasing the wall height I am improving the ride comfort slightly..?

Yes both those statements are correct.

However, I'm saying that if you decrease the width of the tyre to 195 AND increase the profile to 60, then your profile is actually still the same at 112mm.

Basically if you increase the tyre profile without decreasing the size of your alloy wheel to 15", then you will knock the speedo out of calibration.

[ride_comfort_is_my_object]

19 hours ago, Luke4efc said:

Yes both those statements are correct.

However, I'm saying that if you decrease the width of the tyre to 195 AND increase the profile to 60, then your profile is actually still the same at 112mm.

Basically if you increase the tyre profile without decreasing the size of your alloy wheel to 15", then you will knock the speedo out of calibration.

“When you eliminate the impossible, whatever remains, however improbable, must be the truth.”

[fiestaecoboostman]

On 9/21/2021 at 9:51 PM, ride_comfort_is_my_object said:

Sounds a good idea, but would stiffer walls equal stiffer ride...?

Yes, I'm saying if you put smaller rims on for a softer ride and find it's too soft at least you can tweek it back up a bit when you change tyres.

For an unknown reason when I'm looking at tyre prices the XL variant of the same tyre is sometimes cheaper than the std one too.

[ride_comfort_is_my_object]

Thanks to everyone for throwing their spanner into this query.

I think the answer to my question is that I can 'Acceptable' put 195/60/R16 on and I may get a slight improvement. (Thanks FOCUE)

[Luke4efc]

6 hours ago, ride_comfort_is_my_object said:

Put 195/60/r16 on and I may get a slight improvement

I can tell you now that it will make absolutely no difference whatsoever to the harshness of the ride by doing this.

Put the tyres side by side and you'll find the sidewalls are no bigger than your current tyres.

You need to buy smaller wheels to make the ride softer.