Need a MK IV 16" front wheel !

[westcott]

Hello all,
   
   a MK IV owner here in Germany damaged one of his 16" front wheels and is looking for a replacement.
   
   Who want to sell a not needed spare or left over to bring the car back on the road ?
   
   Uwe

[MkIV Lux]

Uwe,
   The spare on a MkIV, needing to fit both front and rear, may have its central part machined differently than a front rim. So the spare would just be useable as a spare and not as a full substitude for a missing front wheel. On my 16" rimmed car this is the case. Just to be checked.
   
   Constant

[SB7019]

Constant.   Interesting - I had always presumed that  my spare being machined slightly differently was an error.  I had obviously underestimated the AC build team!

[MkIV Lux]

Peter,
   I guess the reason has to do with offset clearance. So far I have not taken the time to measure spare vs front vs rear. Might be an interesting exercise though.
   
   Constant

[SB7019]

Constant.
   
   Just took a look at my spare. I  has been machined around where the spinner locates to create a shallow dish rather than the flat face that is on a "normal" wheel.   As a result the conical mating surface between the spinner and the wheel is substantially reduced ( from a depth of about 22mm to one of 16mm) so I certainly would not wish to use it, other than in an emergency!  The rest of the wheel looks identical so am not sure that this machining would change the offset?  For that matter,  I can't see what benefit the extra machining would provide when using it as a spare - maybe someone out there has an answer?

[marklotus]

There is a wheel on ebay.
   Item # 182454043778

[MkIV Lux]

quote:Originally posted by SB7019
   
Constant.
   
   Just took a look at my spare. I  has been machined around where the spinner locates to create a shallow dish rather than the flat face that is on a "normal" wheel.   As a result the conical mating surface between the spinner and the wheel is substantially reduced ( from a depth of about 22mm to one of 16mm) so I certainly would not wish to use it, other than in an emergency!  The rest of the wheel looks identical so am not sure that this machining would change the offset?  For that matter,  I can't see what benefit the extra machining would provide when using it as a spare - maybe someone out there has an answer?
   

   Peter,
   
   The way you describe it, is exactly how it looks on my spare.
   I think the answer will come when trying to fit a standard front wheel at the rear. I will do that exercise next time I will have two wheels same side off the car.
   Maybe John could be so kind as to take a pic of the center part of his wheels (since they are off the car) or measure the spare vs front vs rear.

[MkIV Lux]

Just been looking at the wheels on my Mk IV. One difference between front and rear rim (16") is in the outside pattern of the central part. My car is fitted with centre lock nuts. At the front, there is abaout a 5 mm gap between the nut's edge and the rim's outermost part, whereas at the rear, the gap is nil. This is due to the rear rim's conical mating surface sitting in a cavity machined into the outermost part. I tried to make a drawing of it. Here it is. The clue as to why the spare rim is machined differently is in the text box in the middle of the pic.
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[MkIV Lux]

can't get that URL line off

[nikbj68]

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[TTM]

Hello,
   
   If the rear tyres on a MKIV are wider than the fronts and if both axles have the same width with the wheels removed, then CR may be higher than CF to give a resulting wider rear axle with wheels mounted.
   DR is most likely lower than DF with the purpose of avoiding excessive tangential load on the rear wheel bearings while allowing for a wider (outer) rim, thus a wider tyre.

[westcott]

Hello Constant and all,
   
   i am aware of the difference in machining for the 16" wheels, especially for the "spare wheel". It was the first thing that struck me right away after i inspected my car and the wheel set comming with it.
   
   By spare i ment a 16 " front wheel someone has left as a spare not a "spare wheel" sorry for my bad english writing. I'm discussing a lot of technical details everyday with my chinese colleauges by phone and it seems that I'm going to loose my vocabulary more or less completely......   :-)
   
   Thanks Mark for the ebay link, I'm watching the item and will get in contact with the seller today.

[MkIV Lux]

Hi Uwe,
   Got your message!
   Nevertheless the subject of the "spare wheel" (Ersatzrad in German = the one some of us carry in the boot while cruising all over the country and abroad, taking up precious space that could otherwise be used by our lady co-pilot's third or fourth pair of shoes and some beauty case) is most interesting. Would be delighted to hear your interpretation on the reason of the spare being machined the way it is.
   Cheers
   Constant

[MkIV Lux]

@ TTM
   see inside your text; needs to be checked after measuring
   

quote:Originally posted by TTM
   
Hello,
   
   If the rear tyres on a MKIV are wider than the fronts (yes they are) and if both axles have the same width with the wheels removed (needs to be measured), then CR may be higher than CF to give a resulting wider rear axle with wheels mounted.
   DR is most likely lower than DF with the purpose of avoiding excessive tangential load on the rear wheel bearings while allowing for a wider (outer) rim, thus a wider tyre.
   

[AC Ace Bristol]

.
   Interesting subject.
   
   Being a Ace owner  I don't have such problems, Just a observation or two, With such a variation In size of front tyre to rear tyre you can only carry one as a spare.
   Which leads to why have different offset when the smaller tyre can only be used on the front.
   Assuming Cobras have LSD then a smaller tyre on the rear would surely cause long term problems with the diff, you then inherit the potential problem of does
   your larger tyre fit in the wheel well.[?] or does your passenger find their own way home..[:0]...[B)]
   Just carry a squirty and hope the puncture is small and alocal tyre shop carries such size rubber.
   Back to your initial question,  So why have the different offset.[?]
   
   The hidden joys of owning a Cobra....
   
   Keith