Correct pressure for "get you home" spare tyre?

[Roddy]

My 2011 Yeti is fitted with a "get you home" spare tyre (195/60 R16 89H).

The owner's manual does not detail the correct inflation pressure, neither is it on the filler-flap.

On checking, the spare is inflated to 38 psi.

The dealer, from whom I purchased the car, could not be more specific than "it should be significantly higher than your normal tyres". They suggested that 38 psi was "about right".

Is there an authoritative source for the correct inflation pressure for the 195/60 R16 89H spare tyre?

[rk696]

Well, on my sisters MR2, the spare (space saver) is supposed to be inflated to over 60 PSI, so 38 sounds a bit low.

Is it a proper space saver tyre (195 sounds too wide for a space saver), or just a normal one?

[Roddy]

Well, on my sisters MR2, the spare (space saver) is supposed to be inflated to over 60 PSI, so 38 sounds a bit low.

Is it a proper space saver tyre (195 sounds too wide for a space saver), or just a normal one?

Thanks for responding.

I don't believe that it is a space-saver tyre. As you indicate, it seems more like a normal tyre. But, it does have the warning "do not exceed 50 mph".

[The Plumber]

Hi,

mine is also set from factory at a similar figure 2.9 bar. That's were I left it and as I sometimes run with 2.9 in the rear tyres when she's fully loaded up including a softbox on the roof, it seemed appropriate.

Also checked the Elsawin service manual, there is a chapter on tyre pressures including spare but bizarrely there is no figure given for it :S

TP

[Roddy]

Hi,

mine is also set from factory at a similar figure 2.9 bar. That's were I left it and as I sometimes run with 2.9 in the rear tyres when she's fully loaded up including a softbox on the roof, it seemed appropriate.

TP

Thanks for this. I make 2.9 bar = 42 psi. So, in the same ball-park.

What I can't understand is why it is difficult to get an "official" figure from Skoda. After all, they supplide the spare wheel with the car!

[CFB]

Roddy, I believe the correct tyre pressure for the skinny spare should be on the big yellow warning label on the rim of the spare?

[The Plumber]

Roddy, I believe the correct tyre pressure for the skinny spare should be on the big yellow warning label on the rim of the spare?

Hi CFB,

not on mine, just multiple language warning re not driving over 80kph and getting the full size back on ASAP.

Regards,

TP

[Roddy]

Roddy, I believe the correct tyre pressure for the skinny spare should be on the big yellow warning label on the rim of the spare?

The yellow warning label was the second place I looked, after the owner's handbook. I have just re-checked. It warns of a 50 mph speed limitation, but says nothing about tyre pressure.

[freedie]

Oddly, the correct pressure for my space-saver tyre is imprinted on the tyre wall itself: 60psi (which google tells me is 4.14 bar).

[The Plumber]

Oddly, the correct pressure for my space-saver tyre is imprinted on the tyre wall itself: 60psi (which google tells me is 4.14 bar).

Believe some space-savers do, but don't get confused with the max tyre inflation pressure which will also be embossed on the side-wall.

Regards,

TP

[g6zru]

Thanks for this. I make 2.9 bar = 42 psi. So, in the same ball-park.

What I can't understand is why it is difficult to get an "official" figure from Skoda. After all, they supplide the spare wheel with the car!

You have fallen into the same trap that caught me out. I assumed that Skoda would be the best people to ask when I wanted to know about my Yeti. Other that assuring me that they would respond within 48 hours I heard nothing!

They seem to employ people who don't know anything about the products they sell and the misnamed Customer Support are the worst

Best thing is what you've already discovered, if you want to know something Skoda ask here.

Fred

[Agerbundsen]

Common logic and man's propensity to laziness should give you a reasonable indication:

All tyres leak a little, strangely enough more when not in use.

Spare tyres tend to get ignored and not checked too often.

Maximum inflation pressure stamped on the tyre will always be OK for getting you home.

My take is: Inflate to maximum allowed for the tyre. Chances are that there will be enough pressure in it when you need it. You can always deflate it to a more normal pressure if you feel the need.

BTW, it is NOT a spacesaver special tyre per definition - it is a normal tyre in a slightly smaller dimension that the fitted road tyres, so pressures a bit higher than the others should be OK.

Edited 20 August, 2011 by Agerbundsen

[to12ny]

As Agerbunsen says, it is not a spacesaver tyre. 

 

195/60 R16 compared to 215/60 R16 is only slightly skinnier.

 

My Yaris's spare tyre is a spacesaver tyre (an awful lot skinnier) and has 60psi printed on the tyre itself.

 

The maximum pressure stamped on my 195/60 R16 tyre is 51psi.

 

I have mine inflated to around 40psi.

[gadgetman]

Most need inflating to 50 or 60 psi.

Should be on the sticker along with the 50mph warning

[to12ny]

Gadgetman

 

Nothing about pressures on the sticker, but the maximum pressure stamped on the tyre is 51psi.

 

I do not fancy pumping up to maximum pressure.

[Llanigraham]

Due to the "standard" size of the tyre I suspect it is the same pressure as the rest of the car.

[FlintstoneR1]

Or a few psi above, on the grounds its going to lose some pressure before you come to want to use it?

[rafi_arch]

As per p.209 eng. pdf manual:

"The inflation pressure for this spare wheel is identical to the maximum inflation pressure of the standard tyres"

[kibby]

Why they fit a 90% (195) tyre and loose boot depth when a real skinny spare would do defeats me.

Let's assume they know best.

Hoped they would have re-thought tyre sizes in general so tyres not difficult to source and hence less

expensive with the facelift, but see nothing has changed.

Edited 3 December, 2013 by kibby

[ejstubbs]

Due to the "standard" size of the tyre I suspect it is the same pressure as the rest of the car.

 

I'm sure I read a definitive statement to that effect somewhere a while back, but blowed if I can remember where.  I'd agree with you, though: it's close enough to the size of the standard tyre to suggest that the same pressure should be OK.

 

As per p.209 eng. pdf manual:

"The inflation pressure for this spare wheel is identical to the maximum inflation pressure of the standard tyres"

 

That's a little confusing since it refers to the inflation pressure of the spare but the maximum inflation pressure of the standard tyre.  Sounds to me like the usual slightly garbled Skoda translation TBH.  I wouldn't be comfortable running on a tyre at its maximum inflation pressure for any length of time, if (as is the case with the standard tyre) that figure is so much higher than the normal running pressure (60% in the case of the standard tyre).

 

The pressure given in the manual for the standard 225 width tyre is 32psi.  For the a 205 width winter tyre it is 35psi, which is almost exactly 32x225/205.  Applying the same logic to the 195 spare yields a result of 37psi - still nearly 30% less than the spare's maximum inflation pressure.

 

One way I believe you can think about it is that for a narrower tyre to support the same downward force (ie weight of the car on that corner) at the same pressure as the wider tyre, the contact patch will have to be longer (since it can't usefully get any wider, given the tyre's shape & construction).  That means greater tread deformation when static, and more flexing when moving.  More flexing -> running hotter and more wear.  So all other things being equal (which I recognise they may not be) the narrower tyre needs to run at a higher pressure, approximately proportional to the ratio of its width to the width of the standard tyre.  Given that the Yeti's spare is just a slightly smaller normal tyre rather than a skinny "get you home" job, I believe that other factors eg tyre construction etc are roughly equal (to within what my university lecturers used to call "an engineering approximation") between the spare and the standard tyre.

 

This idea also seems to tally with the prevailing wisdom in cycling circles, summed up by the bicycle tech guru Sheldon Brown as: "wider tyres call for lower pressures, narrower tyres call for higher pressures."  I realise that this may not be directly applicable to car tyres since they have a significantly different profile to bicycle tyres, but I think that the principle should be basically the same.

 

I'd be happy to be accept good evidence that I am wrong about any or all of the above, though

[rafi_arch]

That's a little confusing since it refers to the inflation pressure of the spare but the maximum inflation pressure of the standard tyre.  Sounds to me like the usual slightly garbled Skoda translation TBH.

 

I guess they refer to the maximum recommended pressure indicated in the "inflation pressure table".

It makes sense to me - after all it has to replace a correct inflated wheel so it has to be at least the same pressure. I'm sure they take in consideration the "engineering approximation" educatedly explained above by you.

[ejstubbs]

I guess they refer to the maximum recommended pressure indicated in the "inflation pressure table".

 

But that's the point: we have to try to guess what they mean because the information they provide is unclear.  It would be perfectly reasonable for someone to read it as meaning the maximum inflation pressure indicated on the standard tyre, and inflate to 51psi.  The difference between 51psi and 32psi is vastly more than is allowed by "an engineering approximation".

 

For something as potentially safety-critical as tyre inflation pressures, I would prefer not to have to guess!

[Michaelski]

Checked the spare on my new (delivered in June) 75 BHP Elegance Greentech, & I "may" have what I paid some £50 extra for - a "normal???" tyre, but on a on a steel wheel. And sure enough there's only warnings to not exceed 80k, but NOT any correct pressure quoted. The tyre, although "treaded" appears to be considerably different from the tyres on the 4 Alloys, but IS IT just a space saver, or simply one from a different tyre brand???

It's such a ball-breaker to have to dig everything out of the boot & then remove the wheel to check the tyre, that quite frankly, I simply cannot be arsed to go through the whole routine again.

I checked with the supplying dealership, & the guy there told me that it was indeed a road (define "road")tyre, & the change-it-asap stickers were only there because I could be driving on 3 x Alloys, & 1 x steel wheel???

Anyway, he stated that the pressure that the Dealership/Factory had inflated the spare to (38.5 psi) was correct!!!

This would indeed make sense in the case of a normal tyre, even with a steel wheel, but the space saver that I had in my last car, was as smooth as a billiard ball, & there was no tread on it whatsoever, AND the manufacturer's stipulated pressure was 60psi - the road wheels by comparison, were 31/30.

Sigh.....life used to be SO simple!

[The Plumber]

Our Volvo is fitted with a skinny spacesaver unfortunately (better than a tube of glue mind), however I was pleasantly surprised to find the correct tyre pressure for it listed with the road going tyre pressures, on a sticker in the drivers door frame.

 

 

TP

[x19]

My CR-V has a spare tyre as standard. It is a 17" instead of the car's normal 19" tyres. The following information is clearly moulded into the sidewall of the tyre along with all the other normal info found there, "For temporary use only", "Inflate to 60 psi".

It's strange how Skoda have an ability to keep to themselves information which is essential/useful to the users of their vehicles.