Spare wheel lowdown

Post by **Trundler** » 07 Sep 2006, 11:59

So, what's the real lowdown on spare wheels for the Syncro? I know the wheels should all have the same rolling radius but how big a difference is acceptable for a short emergency trip?

Even if the spare is the same size and the same make and model, the difference in rolling radius will increase as the tyres in use wear. So, the spare should be included in the rotation, but how can you achieve even wear over all tyres?? Two spares? Even then you'd have to do some pretty regular wheel juggling, and you'd be faced with buying new tyres 6 at a time! It could be almost as expensive as replacing the VC....

I find it hard to accept that VW built a vehicle with such a serious lack of tolerance!

Opinions of any experienced Syncronauts welcome as I'm currently without a spare and the 205/70X15 Yokos are wearing down imperceptibly with every journey

Post by **syncroandy** » 07 Sep 2006, 12:11

If directional tyres are avoided then a five-wheel rotation should be possible. Of course this also requires permanently marking each wheel so you don't lose track of which is which.

Post by **Hacksawbob** » 07 Sep 2006, 12:34

take a look here under tyre rotation
http://www.club80-90.co.uk/wiki/index.p ... links_page

Post by **Russel** » 08 Sep 2006, 05:54

U can have a maximum of 1mm tread depth difference beetween tyres
on all 5 or 6.

Post by **Trundler** » 08 Sep 2006, 11:36

1mm ?? For a high-mileage user like me, achieving that makes the vehicle almost unviable. I can't believe it's that sensitive; the VC has to cope with rotational speed differences every time you go round a bend.

Is there a restriction on how twisty the roads can be???

Post by **Trundler** » 09 Sep 2006, 18:19

I'm genuinely interested in other Syncro owners spare wheel arrangements and experiences.

This is all new to me...

Does the VC really go pop instantly if a spare with say 3mm more tread is used??

Post by **KarlT** » 10 Sep 2006, 10:33

No

Bought mine off a guy who knew nothing about it & had a brand new tyre on the front offside.

Drove back from London & VC is still good.

Although it can't be good for it.

Post by **HarryMann** » 10 Sep 2006, 19:22

Does the VC really go pop instantly if a spare with say 3mm more tread is used??

No, far from it!

I've driven hundreds of miles with a big difference between both fronts (new) and rears( well worn)... the VC however, is less than 5,000 miles from refurb, I'm not recommending it for others but suggest you don't have a nervous breakdown about it either!

The difference between cornering continually and running with different front and rear TRCs (or rolling rads) is that that the latter can be a constant state, on a straight road. This doesn't allow cooling intervals and as we know, VCs internally change temperature very quickly, fractions of a second, so developing a steady state temp rise that holds it in the critical ramping range, rather than locked or unlocked... I also think VW advised against serious rolling radius differences fro othert reasons than VC life!

I seem to remember Penske reporting 2mm, but this may tie in with Russel's 1mm on tread, giving 2mm on diameter - I will check and report back.

Post by **irish.david** » 11 Sep 2006, 09:05

I might be wrong about this but as far as i can see in an emergency spare type situation the difference in rolling radius between your 3 original tyres and your emergency spare of different radius would be halved due to the action of the front or rear diff. This is due to the diff compensating for the different rotation speeds of the tyres and effectively averaging them out.

If i'm right this might give the people who want to carry a spare without hanging off the front or rear of the van a bit more room to manoeuvre.

Dave

Post by **Trundler** » 11 Sep 2006, 12:10

Thanks chaps, this is all educational stuff!

Post by **Hacksawbob** » 11 Sep 2006, 20:16

if you wanted knowledge you came to the right place!

Post by **irish.david** » 11 Sep 2006, 20:30

What i'd love to know at the moment is the biggest wheel/tyre combination that anyone's managed to fit into the spare tyre rack under the radiator. When I said room to manoeurve in the post above i reckon that it's probably still not enough for anyone with upgraded wheels.

1 inch = 25.4 millimetres. So even with the diff halving the difference if your spare tyre has a rolling radius of 1 inch less that'll translate to a 12.7mm difference in the case of a blowout. Quite a bit more that what was discussed above......

Dave

Post by **HarryMann** » 11 Sep 2006, 20:52

Aidan will answer that one soon, I'm sure

Post by **Aidan** » 12 Sep 2006, 12:20

haven't been able to get any bigger than a 205R14C in there, Andy's 205R15 ATwas too big. Height becomes an issue too so 205 may be the max, maybe 215 but then you'll be up against the bottom of the gearshift. That's in a proper bash plate carrier mind, don't know about the others - german post office syncro or 2wd carriers, but I really struggled to get a 205R14 into a genuine 2wd 205 wheel carrier on a 2wd - very tight fit.