13 replies to this topic

[ClassicAsh]

Hi all, this is probably a silly question, however, I want to buy some new alloy wheels to replace the rover mini cooper alloys that are fitted to my car, the ones I have are original (as far as I know) they are fitted with 165/60/R12 tyres. but are badly damaged and the tyres are old. so I thought I would purchase some new replicas. The question is, what size wheels do I need. I know that the wheels are 12 inch diameter, but what width of wheel do I need? on the old wheels stamped into the back of the wheel is 4.5B x12. do I assume this is the actual wheel width? because if I measure the total width of the wheel is in 5.5 inches, so the question is does anyone know how to measure the width of the wheel? I assumed it was the total width but the stamping would say otherwise. any advice would be most welcome . Thanks in advance . 

[GraemeC]

4.5" is the width of your wheels - it is measured between the inside edges of the rim (where the tyre sits against).

You should also be able to find an ET figure on your existing wheels - ideally you'd want to match that across to your new wheels too, otherwise they may sit a little more inboard (or outboard) of the arch line.

[ClassicAsh]

ah ok thanks for your help with that, next to the 4.5B x12 it also says x35. is the 35 the ET number? what does ET stand for? thanks

[tiger99]

The ET relates to the offset between wheel mounting face and tyre centre line and is critical to get good handling as it directly controls the scrub radius. I fear that many people drive with good roadholding, which is hardly affected up to a certain point, but with degraded steering "feel" because they have changed things and the scrub radius is now wrong. Many of them will never know. Sad.

The scrub radius is the offset from the tyre contact patch centre and the steering axis where it meets the ground, and that is simply a line through both ball joint centres. The contact patch varies according to wheel camber so there are a lot of variables to juggle. It all comes out rather well with standard offset and wheel width. Alec knew what he was doing!

[Ethel]

ET is the gap in mm from the centreline of the wheel to the face that bolts against the hub. A minus number means the the mounting face is  nearer the inside rim of the wheel than the centreline - A smaller +ve number means the wheel will stick out more, but a bigger -ve number sticks out more too. ET of +35 is correct for an original 12inch alloy.

[ClassicAsh]

ok thanks for the above, at least I know what I should be looking for now, mini sport has some pretty decent deals on minilite replicas complete with tyres, new nuts and balanced ready to fit etc. doesn't mention the ET dimension though so will have to make some enquires on that, failing that I guess I could refurb the old wheels, stupid money from an alloy wheel restorer but I have a blast cabinet, a tig welder etc, so might have a crack myself.

[tiger99]

DO NOT REFURBISH ALLOY WHEELS!

There is far more to it than a bit of TIG weld, and if they are scruffy they are very likely to be at the end of their fatigue life and ready for catastrophic failure.

[tiger99]

Sorry,duplicate post due to bad Internet connection.

Edited by tiger99, 16 February 2017 - 01:12 PM.

[sonikk4]

DO NOT REFURBISH ALLOY WHEELS!

There is far more to it than a bit of TIG weld, and if they are scruffy they are very likely to be at the end of their fatigue life and ready for catastrophic failure.

 

Proof, here we are again with a statement that has nothing to back it up. So your statement is basically stating that all of the Alloy wheel refurbishment companies out there who do repair wheels (and i'm not just talking about a coat of paint) are carrying out dangerous practises!!!!

 

They will undoubtedly state when you bring a wheel in for repair whether it is in fact capable of being repaired or not. (price wise or physically)

 

NDT (non destructive testing) can be carried out on a wheel before and after to see if a repair has been carried out that has removed all of the damage.

 

So before a statement has been made please back it up with irrefutable proof that doing something will end up with catastrophic failure. Without this then its scaremongering.

 

Now if you were to make it very clear that doing a repair yourself without the correct equipment, material or processes in place could lead to a potential failure would be a far better approach without the alarmist statement. So to the OP, although you may have access to equipment that will allow you to carry out a repair, depending on the damage you may end up with potential issues.

 

As someone who works a lot with Aluminium and other materials what you see with the naked eye will without doubt be just the tip of the iceberg if the wheel in question has suffered impact damage. You can buy Dye Penetrant kits which will enable you to see if there are cracks but this is only a very basic form of NDT. HFEC is the way forward here but we are now into a specialised area especially with the equipment. (there other techniques that we use especially on our aircraft up to and including Xray but obviously something your average Joe mechanic will not be able to do)  

 

So if in doubt by all means have a play with repairing the wheel but seriously consider changing it out anyway. The last thing you want is a wheel to fail whilst driving.

[midridge2]

A man from the brake down service told him.

[Dusky]

All depends on what damage there is too. Could be anything from a split in half wheel to a lot of light curbing marks.

[Dusky]

All depends on what damage there is too. Could be anything from a split in half wheel to a lot of light curbing marks.

[tiger99]

Well, I was referring to DIY repairs. It is possible that sometimes a proper professional may successfully repair an alloy wheel. But how do you reverse the cumulative fatigue damage due to repetitive load cycles? And how do you know how long until a crack reaches the Griffith crack length, which under peak load can be very short indeed, at which point catastrophic failure is inevitable.

 

I understand that aircraft wheels are "lifed" and then the metal is recycled. That applies to many other parts of an aircraft too. Car wheels should be too. I had a large and very heavy alloy fail about 6 months ago on my daily driver. Fortunately the crack was in the rim and let the air out before it reached the Griffith length. Had it been near the hub, the first indication would have been the remains of the wheel detaching at speed, and I had been doing 120 on the autobahn not long before.

 

The fatigue problem is the reason that most alloy wheels are heavier than their steel equivalent, and utterly pointless. However I could not get my engine choice without alloys. I have replaced them all, at 100k miles, and will not be keeping the car to 200k so someone else can worry about the next lot.

[ClassicAsh]

The wheels just have surface corrosion / pitting, with a wire wheel in the angle grinder it takes out most of this, I can then tig weld or fill with aluminum filler. The edge of the rims have some kerb damage, nothing serious that wont blend out, with a spot of tig welding to bring the height back up, the paint is flaky, so one all this is done I will pop them into the blast cabinet, then degrease, etch prime, prime and then spay. in fact I have done all of this and they look a good 8 out of ten rather than a 2 out of then. Tiger 99, with respect. I am a fabricator welder by trade with 25 years experience including machining etc. and obviously would not attempt to repair badly damaged wheels.

I might have over egged the original post, by badly damaged I was meaning the paint surface, nothing catastrophic. I was just pretty shocked at the alloy wheel refurb place wanting £84 per wheel ! it has cost be £15 quid for the paint and a pleasant afternoon in the workshop. New tyres now ! yokos ! £69 per corner! ouch !.