AC Owners Club Forum
AC Owners Club Forum => Mk IV, Superblower, CRS and other Continuation Cars Forum => Topic started by: westcott on February 14, 2017, 19:44:50
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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
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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
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Constant. Interesting - I had always presumed that my spare being machined slightly differently was an error. I had obviously underestimated the AC build team!
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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
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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?
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There is a wheel on ebay.
Item # 182454043778
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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.
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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.
Sorry can't get this f...... URL line away!
(http://[URL=http://s172.photobucket.com/user/MkIVLux/media/Mk%20IV/AC%20Cobra%20Mk%20IV%2016%20wheels%20pattern%20by%20CW_zpsktudw8it.jpg.html][img]http://i172.photobucket.com/albums/w34/MkIVLux/Mk%20IV/AC%20Cobra%20Mk%20IV%2016%20wheels%20pattern%20by%20CW_zpsktudw8it.jpg)[/URL][/img]
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can't get that URL line off
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quote:
Originally posted by MkIV Lux(http://i172.photobucket.com/albums/w34/MkIVLux/Mk%20IV/AC%20Cobra%20Mk%20IV%2016%20wheels%20pattern%20by%20CW_zpsktudw8it.jpg) (http://"http://s172.photobucket.com/user/MkIVLux/media/Mk%20IV/AC%20Cobra%20Mk%20IV%2016%20wheels%20pattern%20by%20CW_zpsktudw8it.jpg.html")[/img]
After URL= insert " then after .html insert "
[URL="blahblahblah....jpg.html"]
Code goes away! [;)]
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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.
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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.
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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
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@ 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.
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.
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
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Nice to read you, Keith [:)]
The spare is machined specifically to allow both front and rear use.
Not only are the outsides differing between front and rear rim, but also the stubs dimensions. The front rim's inner fits the rear stub but not the other way around.
You are damn right in your statement about the diff. So spare can really only be used to get you to the neerest garage. Should leave the spare at home (as some of my friends already do) and offer more boot space to the lady [;)]
Yes the larger wheel also fits into the boot.
These tyres are not found on the shelf[:(]
Switching to Bristol power might be a solution [;)][;)]
Cheers
Constant
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On a more modern car I experienced a 200 mile trek home driving with the spare wheel on the rear axle. With quite a lot of power on tap and the opposing tyre being more than twice as wide, arguing with snowy roundabouts took a certain amount of commitment to avoid any disaster.
While this context was a bit extreme, I do not imagine anyone risking driving their MkIV in any spirited manner in the knowledge they have different sizes of tyres on the rear axle.
What type of LSD does the MkIV typically use? Not a Torsen I would hope?
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Hi Constant,
you are absolutely right regarding passenger's shoes, beauty case and so on.... :-)
I removed and stored the spare wheel directly after the car arrived in my garage. Today i carry a tire inflator kit from Continental i bought years before, just removing the bottle of sealing compound every 2 years to keep it in working condition. That kit will work for punctures up to 5mm but not bigger.
The standard MK IV trunk inner is much more spacious then the LW's one. It is quite big and the inflator kit fits neat in a side pocket behind the rear inner fender.
The next weekends will be very busy installing splined hubs and Ace size wire wheels to the car, O.K. maybe AC 289 size wheels :-)
Keith, thanks a lot for planting that idea into my brain !
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Update: Problem solved, we bought the Ebay wheel.
Thanks Mark for the information !
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Hi Uwe,
Did I get that right, you are going to equip the Frog with wire wheels?
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quote:
Originally posted by TTM
What type of LSD does the MkIV typically use? Not a Torsen I would hope?
No,
A Salisbury "Pow-R-Lok" clutch type LSD
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@ Juergen,
no, for sure not, just kidding :-)
I saw a blue MK IV with wire wheels and 4 exhaust pipes at the rear during a visit at "Burgschmiede Namedy".
End of last year I thought about switching to 15" but did not come to a final decission.
But if someone would offer a set of 15" wheels for a reasonable price now............
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Uwe, what you call reasonable? I do have a set of 15" wheels as spare...with lovely Cooper Cobra wheels on it ;-), almost new...
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The wheel shipped from the US Ebay seller was declared as "lost" during its jurney arriving at an UK airport.....[B)]
Nevertheless the seller directly and without any discussion sent the money back.
After that i did a deep dive into 16" wheels and found out the following:
- as long as the wheels are intended for hex nut fixation the 7 inch wide front and spare wheels are identically.
- if the wheels are intended to be fixed by spinners from the factory the center of the wheels is machined to clear the wings of the spinner.
- in case of spinner usage the front and rear 16" inch wheels are machined different, so the cut off has different shape and dimensions front and rear
So the spare wheel from a hex nut set is the same as the front wheel of the same set
A spare wheel of a spinner set is the same as the front wheel of the same set
All wheels from a spinner set can be used with hex nuts.
The wheels from a hex nut set have very small clearance to spinners and if the tolerances come together the wings of a spinner can contakt the center area of a hex nut wheel before the cone itself is seated.
Main dimensions and backspace is the same between spinner and hex nut wheels.
I will take some pics and post them here.
The above mentioned statemets are based on 16" wheels and on two different sets i own, one for spinner fixation one for hex nut usage.
Both wheel sets are from early cars made in 85 and 86.