Another question about my Mk2 Fabia. It's a base model - about as base as base can be. 

 

The front tyres are worn out. They are 195x55R15's, which is the same as on the back of the car. 

 

It seems that 195x50R15 tyres are another recommended size for the car, and are significantly (about £25/corner) cheaper.

 

Is there any harm in having 195x55R15's at one end of the car and 195x50R15's at the other end? (I'm assuming not, but I am also assuming that I'd do better to run the slightly smaller ones at the front in order prevent the old girl from looking too odd.)

 

Thanks. 

3 hours ago, zcacogp said:

Another question about my Mk2 Fabia. It's a base model - about as base as base can be. 

 

The front tyres are worn out. They are 195x55R15's, which is the same as on the back of the car. 

 

It seems that 195x50R15 tyres are another recommended size for the car, and are significantly (about £25/corner) cheaper.

 

Is there any harm in having 195x55R15's at one end of the car and 195x50R15's at the other end? (I'm assuming not, but I am also assuming that I'd do better to run the slightly smaller ones at the front in order prevent the old girl from looking too odd.)

 

Outside diameter of tyres

195/55R15 595.5mm

195/50R15 576.0mm

 

Therefore, 195/55R15 has an outside diameter 3.4% bigger than 195/50R15.

 

If you put 195/50R15 on the front they will rotate 3.4% faster than the 195/55R15 tyres on the rear. In general, anything over 1.5% difference in the outside diameter of tyres could cause problems with traction control, anti-lock brakes, electronic stability program, etc.

 

195/50R15 has a standard load index (ie. not XL) of 82 (475kg)

195/55R15 has a standard load index (ie. not XL) of 85 (515kg)

 

This means that by changing the front tyres from 195/55R15 to 195/50R15 you would have to increase your front tyre pressures by about 0.2 bar (3 psi) in order for the tyres to be able to support the same load. Due to the slightly increased tread width of the lower profile 195/50R15 tyres, the lower sidewall height, the stiffer construction of the carcass, the change in front tyre size would result in a harder ride (all other things being equal).

 

195/50R15 may have more lateral grip than 195/55R15 in certain situations. This could potentially result in an oversteer situation, losing the back end of the car, etc. In the invent of an accident, the insurance assessor may not be happy with this staggered arrangement. It's very easy to spot, as the front tyres will have noticeably less sidewall height.

 

Edited 30 April, 20224 yr by Carlston

Unfortunately the cars ABS system won't like the front and back wheels rolling at different speeds so you'll need to keep all the tyres on the car the same size.

Bother. So mixed sizes front and back won't work? 

 

That's annoying. It'll make it all a chunk more expensive. I wonder whether it'll be cheaper in the long run to swap both the worn-out tyres at the front and the part-worn ones at the back for new ones in the smaller size. 

 

Thanks for your input chaps. 

1 hour ago, zcacogp said:

Bother. So mixed sizes front and back won't work? 

 

That's annoying. It'll make it all a chunk more expensive. I wonder whether it'll be cheaper in the long run to swap both the worn-out tyres at the front and the part-worn ones at the back for new ones in the smaller size. 

 

Thanks for your input chaps. 

 

No it won't work.

 

In your position I'd change all four tyres for the cheaper size because you can often get a discount for supply and fit on four and you can sell the two part worn tyres on ebay for a fair price to help defray the additional costs.

The Fabia Mk2's ABS cares not if there are different sized / diameter / circumference tyres front or rear and neither does the ESP if the car had it as standard or an option, 

or does the TPMS if set.

Not all had ESP fitted right up to the Mk2 Fabia being discontinues. 

 

The reason i know and others do is because they have used different sized tyres on the front / rear. 

Matching sizes as a pair at front or at rear. 

http://briskoda.net/forums/topic/473927-mixing-tyre-sizes

 

Edited 30 April, 20224 yr by roottoot

3 hours ago, roottoot said:

The Fabia Mk2's ABS cares not if there are different sized / diameter / circumference tyres front or rear and neither does the ESP if the car had it as standard or an option, 

or does the TPMS if set.

Not all had ESP fitted right up to the Mk2 Fabia being discontinues. 

 

The reason i know and others do is because they have used different sized tyres on the front / rear. 

Matching sizes as a pair at front or at rear. 

http://briskoda.net/forums/topic/473927-mixing-tyre-sizes

 

 

It cares not a jot about the change in width by a few millimetres but a change of 5% on profile is a vastly different matter as @Carlston has clearly quantified above.

So that is width covered.

 

5% profile of 195 width, neither here nor there. When you actually put them on and drive the car. 

   

What about the 3.1 or even 3.4% difference in diameter front to rear?   

 

The ABS does not care a jot. 

 

I have had 205/45 R 17 on the front and 205/40 R 17 on the rear and winter / all weathers where the size on the tyre is not matching what a tyre calculator shows the circumference to show. 

That might only be near 3.5% difference with a tape measure around the tyres. 

?

How much before a ABS issue shows do you have to have the difference?

 

It is sometimes when you actually use the different sizes and run the cars that you know what does or does not happen.

I used to put on the bigger tyres on the front and run them for a few days or weeks before the matching rears went on or if the weather never changed they rears did not go on. 

 

A Pirelli Zero Nero 205/40 R 17 could be bigger or the same size as than another manufacturers 215/40 R 17 or 205/45 R 17

More of a circumference than others 205/40 R 17's

Edited 30 April, 20224 yr by roottoot

...and I've had ABS issues with 185/60/14 on the fronts and 185/65/14 on the rears.

 

I'm erring on the side of caution with my advice based upon this experience.

That is good info.

& can we assume was on a Mk1 Fabia?   

 What were the issues, was it a ABS warning light or the cars behaviour?

2 hours ago, roottoot said:

That is good info.

& can we assume was on a Mk1 Fabia?   

 What were the issues, was it a ABS warning light or the cars behaviour?

 

The ABS would trigger randomly when braking, the ECU thought the back wheels were locking up because they were rotating slower. Yes it was a Mark 1 with Bosch ABS, the same system as other Polo 9N platform cars. It was incredibly annoying because it increased stopping distances needlessly. It stopped when I got rid of the 185/65/14 for 185/60/14 all round.

You sure you got the numbers right?

On mine, for 15 inch rims allowed sizes are 195/55 and 185/60. For 16 inch it does have 195/50 however.

 

Oh and, regarding abs. I ran in the winter one 185/55 with 195/55 on fronts and everything is okay until you need to brake or turn with the smaller wheel on the outside. Traction control becomes very trigger happy in these situations

@AthrxWhat reason did you run those, had you needed to fit one of those as a spare?

You have a DSG do you not?

Edited 30 April, 20224 yr by roottoot

21 minutes ago, Athrx said:

You sure you got the numbers right?

On mine, for 15 inch rims allowed sizes are 195/55 and 185/60. For 16 inch it does have 195/50 however.

 

Oh and, regarding abs. I ran in the winter one 185/55 with 195/55 on fronts and everything is okay until you need to brake or turn with the smaller wheel on the outside. Traction control becomes very trigger happy in these situations

 

The numbers are right, the point is not the actual sizes, it's the mixing of them that causes the confusion, because the ECU is measuring all four wheel speeds many times per second, if it sees the rears going slower during braking it assumes the rears are locking up and pulses the brakes.

you can get 2 tyres in that size for less than £90, hundreds of them on Ebay for example.......

 

https://www.ebay.co.uk/itm/144489771550?hash=item21a442f21e:g:14cAAOSwrY5iTFks

13 hours ago, Athrx said:

I ran in the winter one 185/55 with 195/55 on fronts and everything is okay until you need to brake or turn with the smaller wheel on the outside.

When is the smaller wheel on the outside whilst turning if you have different sizes front and rear!?

Different sizes (of any kind - width, diameter or sidewall height) on an axle will cause problems, I understand that. I'd not be trying this in any circumstances. However what are the odds of a different rolling circumference front to rear causing problems? Thanks for the maths Carlston, 3.4% sounds about right.

 

I guess that the only surefire way of finding out is to try it and see. Sepulchrave, your idea of changing all four and selling the part with ones from the back on eBay sounds like a good one. If no one can reassure me that mixing sizes front to back won't cause problems then this is the way that I'll go.

 

Edited To Add: early mk2 fabia, very base model, pretty sure that it has ABS but also pretty sure that it doesn't have ESP or TPMS.

Edited 1 May, 20224 yr by zcacogp
Additional detail

Thinking about it, would 185x60R15 be a better choice? What's the difference between the rolling diameter of these and the 195x55R15's? It's a smaller width but bigger proportion in the sidewall height so it may be quite similar in circumference.

Many Mk2 Fabia did / do not have ESP / ESC as Skoda were still charging as an option when others had it as standard. 

Some did have it as standard.

 

Then Traction Control / TC / ASR was not on all cars or enabled on all, and some had an off switch and some did not, including Monte Carlo's.

Then with the DSG some like the vRS had XDS while others with the DSG did not.

 

Those with TC/ ASR and with or without XDS can have lots of flashing of the TC light even with the correct tyres can be because they are tyres with crap traction. 

TC/ ASR is only dealing with the drive wheels (Front)

 

ESP / ESC is trying to keep things going where they should. 

.... and ABS?

Well the Anti-lock (skid)  brake systems compulsory from 2004 are not activated until the user is pressing the brake pedal or hand control if they have that. 

But then the system is part of more stuff as time moved on. 

having a different overall size / rolling circumference potentially will make a difference front to rear as already been explained, the ABS will see it....

 

Why not just buy 2 tyres in the correct size.??????.......................I don't understand the want to "try" something that might be a waste of money and turn out more expensive in the long run.

 

I posted a link to tyres which are very cheap earlier in the thread.

 

Thinking about it, would 185x60R15 be a better choice? What's the difference between the rolling diameter of these and the 195x55R15's? It's a smaller width but bigger proportion in the sidewall height so it may be quite similar in circumference.

 

Not a lot, about 6 mm, or just over 1%................but my question would be again why ? there can't be much difference in cost between these 2 tyre sizes.

Edited 1 May, 20224 yr by UrbanPanzer

I'm not sure how many of the tyre comparison calculators or sites actually included the rolling circumference but this one appears to. - " . . . it is important to make sure your vehicles rolling circumference remains the same or as close to the original rolling circumference as is possible.  Our handy Tyre Calculator lets you see all the acceptable tyre sizes that exist within a 1% tolerance of your original size and also lets you compare two tyre sizes to see if the new size will be within the 1% tolerance of the old size."

 

The 1% tolerance seems to include 1.24%.

 

https://alloywheels.com/tyreCalculator

 

Calculator Results

Comparing 195/55R15 against 185/60R15

	Width	Profile	Rim Diameter	Diameter
Tyre 1	195	55	15	595.5mm
Tyre 2	185	60	15	603mm

FITMENT OK!
The percentage change is 1.24% and the circumferece change is 7.5mm.

On 01/05/2022 at 10:18, KenONeill said:

When is the smaller wheel on the outside whilst turning if you have different sizes front and rear!?

3 wheels same size, 1 smaller on front left hand side. Need to mention that it was some chinese crap as well, so traction in the winter constant wet weather wasn't particularly great

 

@roottooti did not really notice until it was time to change them for the first time since car's purchase. websites + fuel cap were telling me different numbers from what i happened to check (the odd one). Now i learned at least. 

10 hours ago, Athrx said:

3 wheels same size, 1 smaller on front left hand side.

That didn't come through from the earlier posts. Since it was the actual case, I agree the point.