Space Saver Wheel - Is my paranoia justified?

[wai]

Yes, the coefficient of friction is non-dimensional so it does not matter how wide your tyres are, you get exactly the same amount of grip. Also, in wet weather, you have a higher contact pressure so reducing the possibility of aquaplaning.

On, a narrow tyre will heat up more (but nothing to worry about in normal highway use), and it will wear quicker.

Many years ago, Alf Costanza raced in the Alfasud series and he went for the narrowest tyre permitted because it would heat up quicker in race conditions. He lost no grip at all.

[Diesel_vert]

Anyhow, just one question. The space saver spares in the video were running at 60 PSI. Seems rather high. What's the accepted wisdom for pressures in these tyres?

A tyre's load capacity is mostly determined by air pressure.

T-type temporary tyres are designed to be inflated and operate at 420 kPa (60 psi).

If the volume is small (T-type temporary tyre) and the load is high (passenger vehicle) then the pressure must also be high (420 kPa or 60 psi).

[brad]

I think the recomended pressure for the space saver is on the fuel flap.

I just pump my spare up to 60 anyway - no matter what it is. Saves dissapointment when you go to put it on the car & it's flat.

[midlifecrisis]

I finally put my full sized spare in. Just needed to razor out a bit of plastic.

[Mountainman]

I just couldn't get myself to do that to mine.

[DV52]

I finally put my full sized spare in. Just needed to razor out a bit of plastic.

midlifecrisis: Very impressive! Can you put back the boot floor thingy into the lowest position, or is the full size tire so large that you can only use the upper position?

[midlifecrisis]

Floor is upper level only.

[adhock]

This is a bit delayed, but hey, others may benefit also. Recently decided the time had come to get the full sized spare (thinking of driving outside the metro area, where 225x45/17 tyres may be scarce or expensive) and so rang around. We have space in the wheel well in the wagon - can't comment on hatches. Alloy 17" is $750 odd just for the wheel! Anyway, Wangara VW offered a 15" steel rim with tyre for $150, rolling radius 2 mm different from 17" rim and 225x45/17 tyre apparently. Recycled from bargain Golfs optioned up to alloys from tin rims, they say. Bargain if so. I'll find out how close the size is later this week, but other dealers should be the same if the solution works. Downside: didn't know this when wheeling, dealing and trying to deal for the purchase 6 months ago.

[midlifecrisis]

I bought 4 alloys - most economical way to get my spare. I plan to sell 2 off. I was think $250 each to others who also want a full sized spare with the proper alloy for looks and full performance. Shipping extra. If anyone is interested private mail me.

[brad]

This is a bit delayed, but hey, others may benefit also. Recently decided the time had come to get the full sized spare (thinking of driving outside the metro area, where 225x45/17 tyres may be scarce or expensive) and so rang around. We have space in the wheel well in the wagon - can't comment on hatches. Alloy 17" is $750 odd just for the wheel! Anyway, Wangara VW offered a 15" steel rim with tyre for $150, rolling radius 2 mm different from 17" rim and 225x45/17 tyre apparently. Recycled from bargain Golfs optioned up to alloys from tin rims, they say. Bargain if so. I'll find out how close the size is later this week, but other dealers should be the same if the solution works. Downside: didn't know this when wheeling, dealing and trying to deal for the purchase 6 months ago.

The 15" will still be regarded as a "temporary spare" and you'll be limited to 80kph. The tyre size will most likely be 195/60r15.

You're better off sourcing something (a whole set maybe) from ebay, gumtree or an AU based forum. It doesn't matter if the style of wheel doesn't match - it's the diameter, width & offset that matters. Just put a 2nd hand tyre on it.

225/45r17 is a really common size these days. 235/45r17 even more so (something to think about when replacement time comes)

[Mountainman]

The 15" will still be regarded as a "temporary spare" and you'll be limited to 80kph. The tyre size will most likely be 195/60r15.

I think you'll find that is a 195/65 15 for the standard Golf size (been that way since the Mk5), which also keeps it to the same rolling circumference as the 205/55 16 (like I have optioned on my Golf) and the 225/45 17 on the Highline. I'm going to see if I can get a standard 16" steel wheel from a Jetta and run the 205/55 tyre that I have on the rest of the car. It has to be cheaper than the $680 Toronto 16" alloy that VW are asking. And I only intend taking it as an extra spare anyway when I do extended country driving. it still leaves enough room for our luggage and does give that extra peace of mind for not having to replace that tyre straight away.

[brad]

I think you'll find that is a 195/65 15 for the standard Golf size (been that way since the Mk5), which also keeps it to the same rolling circumference as the 205/55 16 (like I have optioned on my Golf) and the 225/45 17 on the Highline. I'm going to see if I can get a standard 16" steel wheel from a Jetta and run the 205/55 tyre that I have on the rest of the car. It has to be cheaper than the $680 Toronto 16" alloy that VW are asking. And I only intend taking it as an extra spare anyway when I do extended country driving. it still leaves enough room for our luggage and does give that extra peace of mind for not having to replace that tyre straight away.

I'm sure you're right.

The Octavia had 16x6.5 alloys with 205/55r16. The spare is a 16x6.5 steel wheel with 205/55r16. It still has a big yellow sticker saying "Temporary Spare - Speed Limited 80kph". It's crazy.

I'd still be searching for a set of alloys - you'll only pay $300-$600 with tyres.

[adhock]

I'm with Mountainman. Peace of mind when out of town, which the Spacesaver doesn't give. The tin rim will only go on the back, and it'd get me round until we get to a decent tyre dealer. Our previous mk 6 Golf had 16" alloys and a steel 16" spare, did a tyre round town (@#$% nails!) and the spare spent about a month on the back. No probs.

So a genuine VW rim with new Continental tyre for $150 suits me. Matching alloy would be nice, so would 17" rim and matching tyre, but not for the price. Maybe I can get a bit back for the spacesaver also....

[Diesel_vert]

General summary:

For the purposes of roadworthiness, a vehicle is required to have a matching wheel and tyre assembly for any given axle. Specifically:

- All tyres must be of the same construction (e.g. radial) and size.

- All rims must be of the same diameter, offset, width and mounting configuration.

There is a provision in the regulations where the above requirement does not apply to a wheel and tyre assembly that is only intended to be used in an emergency as a temporary replacement under restricted driving conditions.

Thus, any non-matching wheel and tyre assembly fitted on a given axle, in respect to the above requirements, is to be considered a temporary spare.

When any temporary spare is fitted, vehicle manufacturers will ordinarily restrict the operating speed (usually 80 km/h or 50 mph), irrespective of the tyre's actual speed symbol.

Always be mindful when driving on a temporary spare of any kind, adopt a more cautious driving style and use common sense, even in the absence of a yellow warning sticker.



For reference, rolling circumference figures for various tyres:

Standard fitment tyres for the Mk7 Golf:
195/65 R15 91H - 1937 mm
205/55 R16 91V - 1928 mm
225/45 R17 91W - 1934 mm
225/40 R18 92Y - 1943 mm
225/35 R19 88Y - 1955 mm*

T-type temporary tyres:
T 125/70 R16 96M - 1787 mm
T 125/70 R18 99M - 1943 mm

Alternative tyres:
235/45 R17 94W - 1964 mm
235/40 R18 91W - 1967 mm
235/35 R19 91Y - 1973 mm**

*Except for the Golf R.
**Factory option for the Golf R.



The distance one may drive with a temporary spare fitted on a vehicle is limited by its tread depth - this includes T-type temporary tyres.

Tread life is difficult to predict, but I would expect to be able to cover a distance of approximately 3 000 km on an unused T-type temporary tyre before reaching its tread depth limit, provided it is inflated at the correct pressure (usually 420 kPa or 60 psi).

The only proviso is that, in the interests of preserving the drivetrain, Volkswagen states never to drive further than 200 km with a temporary spare if it is fitted to the drive axle.

Do note the small, but crucial differences in rolling circumference, even between 'equivalent' sizes - hence the warning by Volkswagen on temporary spares (or any non-matching tyre size) fitted on a driven axle.

The Octavia had 16x6.5 alloys with 205/55r16. The spare is a 16x6.5 steel wheel with 205/55r16. It still has a big yellow sticker saying "Temporary Spare - Speed Limited 80kph". It's crazy.

The steel rim may have a different offset to that of the alloy rims fitted on the vehicle.

If that is not the case and the steel rim matches the dimensions of the alloy rim, my best guess is that Skoda decided to place the yellow warning sticker on every temporary spare on the production line for the sake of simplicity, rather than determine which model had which wheel and tyre wheel assembly and place the sticker accordingly.