A new TYRE question

johnos1984

Simple question.

Will fitting 205/55 R16's make any difference to a car which has 215/55 R16's already on.

I'm told the 2006 Passat came with both.

The reason I was advised to do it is the price difference in the size of tyre is HUGE

langdang

1.7% diff, basically nothing. You will be moving 1.7% slower compared to your old tyres for the same reading on the speedo.

http://www.miata.net/garage/tirecalc.html

johnos1984

I was thinking along those lines alright.

Any I'm getting Bridgestone 205/55 R 16 for the magic sum of €95.

Budget tyres were more expensive and a laser wheel alignment is €25.

Mr.David

It depends on the width of the rim - what width is it?

Ev84

If you are going from 215's to 205's would that not mean you are getting a tyre that is 10mm narrower?
205mm=tyre width / 55mm=tyre profile(sidewall) / R16=wheel size...

johnos1984

I haven't a clue but to buy the correct size tyre in the same brand will cost €150 a corner.

The tyre place reckons all will be good

Ev84

johnos1984 wrote: »

I haven't a clue but to buy the correct size tyre in the same brand will cost €150 a corner.

The tyre place reckons all will be good

Cool. Go with them so... afaik the overall tyre radius/height is not increasing or decreasing so it shouldn't affect your speedo. 10mm less tyre width will give you less traction/grip alright.

langdang

Ev84 wrote: »

55mm=tyre profile.

The "55" is not mm. It's a percentage.
The "height" of the tyre is Width X tyre profile.
In this case 215mm * 55% = 118.25mm
205mm * 55% = 112.75mm so a 5.5mm diff in tire "height"
But taking the total size of the wheel + tyre, it's only a 1.7% difference.

Assuming that the old tyres are near the wear limits, there will be even less difference between the old and new diameters until the new tyres wear down.

EDIT - the traction/friction/tyre width thing is a whole other ballgame, and it still kinda confuses me.

Tea 1000

Ev84 wrote: »

If you are going from 215's to 205's would that not mean you are getting a tyre that is 10mm narrower?
205mm=tyre width / 55mm=tyre profile(sidewall) / R16=wheel size...

Yes. Also the profile will be slightly lower. The 55 in the profile is not mm, it's % of the width. Wheel size in inches when the rest is metric is a bit silly also!
So basically a 255/40 tyre will have a similar profile to a 205/55.

johnos1984

Ev84 wrote: »

Cool. Go with them so... afaik the overall tyre radius/height is not increasing or decreasing so it shouldn't affect your speedo. 10mm less tyre width will give you less traction/grip alright.

In normal use I'd imagine the less grip wouldn't be noticable

Ev84

Sorry guys, I didn't know that...

langdang

johnos1984 wrote: »

In normal use I'd imagine the less grip wouldn't be noticable

Tyre composition will be far more important in the traction available I'd say

Mr.David

I think the important factor is not the change in diameter affecting speedo, its putting a narrower tyre on the same rim. This can be done, up to a point and its defined as to what is and is not acceptable. Beyond that it can be dangerous.

You really really need to check your rim width, its measured in inches for example 8J. It may well be cast into the inside of your rim or else in the owners handbook.

vectra

Put the proper size on but fit Hankook's
shouldnt be much more than 100 poer corner and if you are around my area i ciould get laser allignment thrown in for free with 4 tyres

sundodger5

if memory serves the passat with those tyres requires an extra load tyre, with this in mind the smaller tyre will be wrong on size and load carrying cabability.
I would recommend a budget tyre in the correct spec rather than a brand in the wrong size.
Get the best you can afford in the correct spec.
Tyres are cheaper than panel beaters.

CiniO

Ev84 wrote: »

10mm less tyre width will give you less traction/grip alright.

That's not as straight as it looks like.
If someone is thinking - the wider the tyre, the more grip it has - it's wrong assumption.

According to physics surface of contact, doesn't affect fraction, so grip shouldn't be affected.
In reality there's million other factors, and grip is actually affected depending on tyre width, but it's definitely not as simple as you wrote.
In some conditions narrower tyre will have better grip. In other condition wider tyre will be better.

CiniO

johnos1984 wrote: »

Simple question.

Will fitting 205/55 R16's make any difference to a car which has 215/55 R16's already on.

I'm told the 2006 Passat came with both.

The reason I was advised to do it is the price difference in the size of tyre is HUGE

Make sure you inform your insurance company then, as this is the modification to your car, and all insurance companies require to tell them about modifications.

route66

As stated, the tyre you are considering is narrower. This means there is a smaller "shoulder" or overhang over the wheel which will make your wheels much more susceptible to kerbing.

Unless you are a perfect driver of course

Also, wouldn't worry too much about the insurance aspect of fitting these tyres.

johnos1984

Makes little difference now as there is two nice bridgestones on the car now. I also got tracking and balancing done for €215 all in.

TBH having thought about it for the type of driving I do and the type of car it is the grip situation shouldn't affect me much as it is only a boggo engine Passat and won't ever see too much spirited driving in my ownership as its motorway all the way.

As for insurance companies, when I told them I fitted winter tyres they just said that great and why did you call us again

As for kerbing, the previous owner saw to that so I don't have to worry or feel guilty about it.

The only place in town that could supply hankooks wanted €120 per corner and €35 for the tracking, uniroyals were €129 and Bridgestones of the correct size were €150. I could of gotten some cheap brand made by Michelin for €105 a corner so alll in all I'm happy going a size smaller and getting them fitted.

It worked out cheaper than ordering the tyres and paying for fitting online

route66

Woops, hangon - only 2?

Whatever about replacing the tyres with 10mm narrower (and therefore smaller in diameter) ones, I'm not so sure about only replacing 2. I'd say this will affect the handling.

johnos1984

route66 wrote: »

Woops, hangon - only 2?

Whatever about replacing the tyres with 10mm narrower (and therefore smaller in diameter) ones, I'm not so sure about only replacing 2. I'd say this will affect the handling.

The are both on the rear so there shouldn't be any issue.

If they were mixed and matched then yes it may create issues but you would really have to be pushing the car to find out

It never created any issues when I had the winter tyres on which were also 205/55 R16's.