Cracked Wheel

[DSLiverpool]

I'm getting the SL detailed again and made perfect before sale, it has 2 faults both Are leaks from the split rims. Front one drops flat over 2 weeks, it was light corrosion and easily fixed for £10, the rear drops soft never flat over 3+ months and I asked them to have a look expecting corrosion, sadly it's a 1" crack on the inner rim :-(

These wheels are £££ approx £900 each

Options are: New wheel or Weld it (doing nothing isn't an option)

Just wondering if its insurance claimable probably not.

Can I have opinions on welding it please (I know a specialist alloy welder who does wheels)

 

[ringway]

Our man Johnsco was talking about alloy wheel welding recently. IIRC, he said that he had X-Rayed a repaired wheel and the crack was still evident behind the weld.

 

[Agwarn]

Not sure i'd want to risk a repaired wheel on something as powerful as a SL55.

 

[JasM]

A member on here (KLP 92) is currently selling one on ebay :

LINK

 

[DSLiverpool]

A member on here (KLP 92) is currently selling one on ebay.

LINK

That's an option, I'd have to get the centre painted (bet it wouldn't match the rest) - mate just told me to get a price from MB for the rim without the centre - it's an option I suppose.

 

[mercedescl500]

If done correctly then the weld will be stronger then the surrounding metal. I don't see anything wrong with a high quality weld.

 

[mabz]

get it welded mate and add it in the for sale ad if your worried.theres no point buying a new wheel to then sell it on

 

[LTD]

I admire your honesty and attention to detail.

Many would have just pumped up the tyre and sold the car.

 

[flango]

Johnsco is the expert on weld inspection testing whatever he says is gospel. I've also never seen a successful alloy wheel weld the surrounding corrosion sometimes not visible usually makes for poor weld.

 

[johnsco]

For every 100 good welders in steel and stainless steel there's probably one good welder of aluminium and aluminium alloys.

All welds are ALWAYS an inherent weakness in any structure.
In my work as an inspection engineer, my customers will go to enormous lengths to avoid welds in any safety-critical structures.

Where there are safety-critical welds, then careful consideration has to be given to the particular alloy composition ... There are very many grades of aluminium alloys.
Also - Special welding techniques have to be approved for satisfactory welding of just-about any materials where safety is an issue.

Some time ago, a customer of ours brought an alloy wheel and asked us if we could test the weld-repair. It looked fine. We X-rayed it and there was a crack in the heat-affected zone adjoining the weld.
The customer took the wheel away ... The weld was gouged-out and re-welded ... We X-rayed it again ... The crack was still there (or one very-similar).

The weld metal may indeed be stronger than the parent metal of the alloy wheel.
Many of the weaknesses will be at the fusion interface or in the heat-affected zone.

Many guys will tell you that they are expert welders of aluminium.
Ask to see their welder qualifications.
Ask whether their repairs are subject to nondestructive testing on completion.

There are one or two specialist welders of aluminium alloys, who are good.
They will NOT be cheap.
If you use a good outfit ... and get it X-rayed and dye-penetrant tested with satisfactory results ... Then you will probably be safe.

But ... What about 12 months down the line.
Fatigue-life in aluminium alloys is pretty-much impossible to predict.
That's comforting next time you fly !!!

 

[hotrodder]

If done correctly then the weld will be stronger then the surrounding metal. I don't see anything wrong with a high quality weld.

No it won't. All welds have a HAZ (heat affected zone) where the microstructure of the metal has been altered by thermal cycling. In carbon steels this HAZ can be harder (more brittle) than the surrounding metal, especially if cooling rates are excessive- lack of pre & post heat with med carbon/alloy steels. With aluminium the weld and HAZ is complex containing annealed, partially annealed and (in the case of heat treatable alloys) overaged areas. It is ALWAYS softer and weaker unless the part itself was annealed anyway.

In addition to what Johnsco said many, probably most, OE car wheels are heat treated during manufacture to increase strength and hardness. Yep, cast wheels too. The final stage of heat treatment is typically 'artifical aging' which involves 'cooking' the part at around 180 C for 8+ hours. Heating the part above this temp for any length of time WILL change things. The annealing temp for aluminium and it's alloys is in the 340 - 410 C range. Welding = melting it = 660ish C.

Flow forming cast wheels is becoming more popular and like forging flow forming improves the grain structure over the 'randomness' of a straight casting. This grain structure can be used to engineer weight out of the wheel (or make it stronger for a given weight). Welding is, in effect, casting so will undo this grain structure local to the repair i.e. even if the weld is perfect (no such thing) the wheel will still be softer and weaker afterwoods. In the case of an alloy like 6082-T6 (fairly common suspect for forged wheels) welding it can halve it's strength, best case scenario is around 60% of the origional

FWIW i'm a welder & fabricator that specialises in ally for example...

and as a general rule i don't touch wheels

 

[mercedescl500]

Heres a good thread, fairly balanced view from both sides.

http://www.mbclub.co.uk/forums/wheels-tyres/72799-cracked-alloy.html

 

[coupe deville]

All welds are ALWAYS an inherent weakness in any structure. QUOTE ]


Ayton Senna had his steering column shortened and welded after he complained he couldn't see the instruments during practise for the 1994 San Marino GP. After his fatal accident while leading the race the column was found to be broken at the weld. The team maintained the break was caused by the accident and not the cause of the accident.
Maybe so but I bet no race cars are sent out with welded steering column anymore.

 

[mercedescl500]

this company has destructive testing on repairs

For every 100 good welders in steel and stainless steel there's probably one good welder of aluminium and aluminium alloys.

All welds are ALWAYS an inherent weakness in any structure.
In my work as an inspection engineer, my customers will go to enormous lengths to avoid welds in any safety-critical structures.

Where there are safety-critical welds, then careful consideration has to be given to the particular alloy composition ... There are very many grades of aluminium alloys.
Also - Special welding techniques have to be approved for satisfactory welding of just-about any materials where safety is an issue.

Some time ago, a customer of ours brought an alloy wheel and asked us if we could test the weld-repair. It looked fine. We X-rayed it and there was a crack in the heat-affected zone adjoining the weld.
The customer took the wheel away ... The weld was gouged-out and re-welded ... We X-rayed it again ... The crack was still there (or one very-similar).

The weld metal may indeed be stronger than the parent metal of the alloy wheel.
Many of the weaknesses will be at the fusion interface or in the heat-affected zone.

Many guys will tell you that they are expert welders of aluminium.
Ask to see their welder qualifications.
Ask whether their repairs are subject to nondestructive testing on completion.

There are one or two specialist welders of aluminium alloys, who are good.
They will NOT be cheap.
If you use a good outfit ... and get it X-rayed and dye-penetrant tested with satisfactory results ... Then you will probably be safe.

But ... What about 12 months down the line.
Fatigue-life in aluminium alloys is pretty-much impossible to predict.
That's comforting next time you fly !!!

Alloyweldcraft in High Wicombe does do destructive testing. dye penetration and is Zurich Insurance approved to weld/repair alloy wheels. HTH

Alloy Weldcraft ? alloy wheel repair and refurbish

 

[johnsco]

I'm not at all sure that you can "destructively test" a repair.
We offer nondestructive testing of repairs (X-ray and dye penetrant test).

Alloy Weldcraft will have produced a sample weld on one particular wheel, and submitted it to a fracture test.
The assumption is that this is generally representative of the welder's work.

All "coded" welders have to produce what are known as test plates from time to time.
We X-ray, ultrasonic test, MPI and dye pen test a lot of test plates for the welders that our customers employ.
This is often overseen by insurance companies (such as Zurich or Royal-Sun) or sometimes by Lloyds.

All welding on critical structures (nuclear, marine, aerospace, pressure-vessel, etc) usually requires the use of coded welders.

Please don't take my comments to imply that there are no good welders in aluminium and its alloys.
My doubt comes in because of the very-variable metallurgy and quality of vehicle alloy wheels, and the fact that some of the alloy wheel repairers (as I have seen) are not that competent.

 

[WDB124066]

I wonder if MB have guidelines on repairing cracked wheels like they do for welding a chassis after an accident, may pay to ask them officially??

If you are going to weld it properly you need to know the Spec and Grade (including the thermal history) of the parent metal, this will need to come from the manufacturer. - if they will tell you. From there you can organise a Weld Procedure qualified specifically for the material or alternatively if MB do permit weld repairs they may well have a Proceudre for you to use.

The location of the crack within the wheel is also an important consideration, repairing an area that is highly stressed should really be treated as a temp repair, especially in Al.

If it is welded, and if you want to be confident, the repaired area (at least) WILL need to be checked periodically. As others have said Al has a low fatigue life compared to other materials and will crack if the conditions are right, the same conditions that caused the original crack are still there remember...

 

[wooddoor6]

Not sure i would fancy getting the wheel repaired for selling having the knowledge it could let go sometime in the future on an unsuspected family of on their hols. Might be better to tell the buyer the problem before the deal and let them decide if they want to repair or replace

 

[LTD]

Are you more liable to have an issue with an external puncture rather than this rim ?

That should be the real caveat ...

 

[DSLiverpool]

All people reading this I bet no new owner of anything used has X-ray examined the wheels after purchase of a used car. In fact the tyres only get a quick looksy before you rag the balls of whatever you have.

So as the SL may be sold early in 2013 I've decided to weld and tell the new owner of it with a discount to cover buying a used wheel as part of a private sale. If I px it I guess it would go in the auctions so I would leave a note in the car where a new owner would find it.

Pity this blemish because its been faultless (one rev sensor) for an SL, granted I hardly use it but I've had no issues at all.

 

[LTD]

You should offer it up here ...