You’ll see I have a 98 SLK230, and as I look into the boot (trunk) I see the collapsible spare
tyre and ask myself…”How old is that? and is it safe to use if I really need it?”
So I have pursued some research on this topic, having found not much on the forum, and have come up with the following.
The collapsible spare “SpaceMaster" is made by Vredestein and comes pre-fitted to the rim.
The Vredestein national importer advised that they do not stock or import any of the collapsible tyres.
I checked tyre retails, yep, they couldn’t get them. Same with M-B
Vredestein suggested that there is a special technique for installing the tyre on the rim (presumably, without inflating it). This makes sense.
This is the reason that no tyre retailers will supply the tyre, and also why M-B only supply the complete tyre-rim assembly. No one can fit them.
UK M-B dealer was 226 pounds plus [email protected]
% so about $400USD. Aussie M-B was $1200 +GST=$1320 AUD, so about $1000 USD.
I think the Aussie ones must be very very special to be 2.5 times the price of the UK ones. Airfreight doesn’t cost that much.
These collapsible tyres were used way back in the 1980s on 944/ 928 etc and are still used on many Porsches,
VW, Maserati, Ferrari, Holden, Audi, & M-B, however most of those ones today are not 15” SLK size, but 17” / 18”/ 19" / 20" sizes.
From eBay advertisements of ones for 944s, they looks like they were the same as SLK ones.
All the used ones I saw on eBay are much more than ten years old. You can often see the date stamp in the picture.
What size do I need ?
Just give your Vin number to the M-B dealer and let them work it out.
How Old Is Too Old ? More than 10 years !
General wisdom from all tyre retailers and the tyre industry seems to settle on this number.
Vredestein website specifically says 10 years for these.
Vredestein Tech Brochure 2015 ENG
See Page 66 “Tyre must be replaced ten years after purchase in all cases….."
Why? well the tyres age with time, even if they are never used or exposed to UV light, or heat.
As they age, their hardness increases. They loose their flexibility.
This is the classic problem seen with old trailers and camper vans.
They sit for years and years (decades?) and when someone goes to tow them interstate
to their new location you can bet that (often multiple) tyre blowouts are a high probability.
With normal road tyre use, we wear them out before they get to 10 years.
For Toy cars that live mostly in the garage, they will often get to 10 years before they are fully worn. It is good policy to replace them.
But if you don’t, and one fails, well you have a spare.
Unless your spare is also quite much too old.
Early R170 spare tyres are now all 11 to 18 years old. Mine is 17.
How can you tell the age?
Every tyre is date stamped,
see under 11 Markings, DOT Code, for details
You will find the date stamp usually only on one side. Look after the DOT bit. "DOT WVAD 3908” -This example is week 39, 2008. So October.
Post 2000, it is 4 digits WWYY WW = week of the year YY = year
In 1990s date stamp was 3 digits, with a triangle < WWY<
in 1980s date stamp was 3 digits no triangle WWY
My tyre was 258< so June 1998 !
For the R170 tyre, the date code was on the outer rim side, yes the hidden side, so you have to pull the whole lot out to look.
It’ll be in an embossed ring, where they have to change an insert in the tyre mold every week.
There may be other letters. the first four after DOT are manufacturer code.
Whilst you are doing that, look at the age of your road tyres too.
Make sure you buy a fresh tyre !
If you are buying a new collapsible tyre & rim you really do want a NEW one.
So I am going to buy one from UK which should be fresh from Vredestein in EU. I would accept anything less than 6 months old.
Careful that your dealer doesn’t sell you one that has been sitting on the shelf for a few years.
How much is a used one from eBay worth ? about $10
It would make a nice hose reel for your garden hose. How good would two of them look on your wheel barrow ?,
or get four and make a neat billy cart, but useless for your SLK.
So why do I care?
I use the SLK as my main car. I don’t want to get stuck 100 miles from home, late on a Sunday night.
- First off I have the Tire Fix, The can of magic spray.
- If that doesn’t work I want to be sure that the spare tyre will do the job, and not blow out along the way.
Yes the old one might work and it might not. A new tyre WILL work.
Can I reuse my collapsible spare tyre ?
This is not clear. Various users on the forum have complained that the tyre does not easily contract back to a size that fits in the trunk floor.
This says to me that the M-B Design Engineers expected it to be a single use only (maybe).
The owners manual gives instructions how to collapse it replace it in the trunk. So it is not clear.
I expect most owners will not replace the spare after only one, usually short, trip home with it.
The tread has to expand about 20% in length when inflated, which is a pretty impressive trick for a car tyre.
It needs to be very elastic, so durability is likely to be something that suffers to achieve that.
How much age-related tyre hardening is acceptable for a tyre that has to stretch 20% or more to get to full inflation ?
Tyre Pressure when using the spare tyre
Since the tread has to expand so much and it is the air pressure that is making the tyre “grow”,
You need to carefully follow the handbook instructions for tyre pressure when inflating these collapsible tyres.
Otherwise the rolling radius of that wheel could be very different to the other 3, and this will upset ESP and also braking and handling.
Why do I want to replace my spare now?
They are still available. But the dealers I spoke to could not remember every ordering them.
Increasingly many car manufacturers are moving away from having any spare tyre. Customers now accept this. Lower weight gives better Fuel test figures.
Well, they may be very hard to find new in another 10 years if no manufacturers are using them and no customers are buying replacements.
An existing tyre that is 10+ years old might work ok, but do you really want to use it in 10-15 years when it is 25+ years old?
A blow out at speed in heavy traffic could spoil everyone’s day.
- Check your tyre date stamps
- 10 years is recommended maximum age.
- Check date stamp on a new replacement tyre/rim before accepting it.
- If using spare, Inflate accurately to manufacturers advised pressure.