Split Rim Wheel Bolts

[Ian B]

I'm in the process of refurbishing the alloy wheel rims on my car. The rims are 19" BBS Speedline split rims - like these: https://www.ebay.co.uk/itm/GENUINE-A...-/253815831300

They each have 19 M7 bolts with 12 point heads. the 20th hole has the wheel valve in it. So 76 bolts. 75 came out in one piece. They were all tight, needing an impact wrench or a breaker bar to get them loose. They were all covered in white oxide from corrosion, and a blue sealant - looks like Loctite 222. But they came out.

Then there's number 76. That one snapped off just below the head. I separated the barrels from the centres, and there's about 6mm of bolt sticking out. I tried a tiny pipe wrench on it, but it's stuck far too solid for that.

Plan B is to bore the bolt out in the vertical mill. I flattened the broken face of the bolt with an angle grinder (also thinking the heat from grinding might help). The sparks that came off were very white - tiny tinge of yellow, bushy and bursting at the ends. It was tough to grind. I ground the end of a file in the same light - much darker orange sparks.

The bolt is not magnetic and is corrosion resistant.

Could it be titanium? I can't imagine a 3 series stainless steel being that hard, and a 4 series would be magnetic. Some vendors do sell titanium bolts for these wheels, I just can't find what the OEM uses.

New rims are $shocking. Suggestions on how to remove this bolt?

Ian

[wierdscience]

Tig a head on it with Ti filler rod? That's my usual method.

[old mart]

They may well be titanium. I would use a solid carbide end cutting mill on it to remove the core, probably 6mm would do it. When re assembling, you must seal the threads and bolt shanks 100% to prevent water ingress causing corrosion. An aircraft type sealant like JC5A would do nicely.

[Willy]

Heat above 150°C or about 300°F will greatly compromise the hold that the Locktite 222 has on the fastener.

Welding a nut on the end as described by Wierdscience will also aid in this plus the rapid heating and cooling will also assist in breaking the galvanic corrosion bond.

The use of a solid carbide end cutting mill as described by Old Mart would also produce good results.

It all depends on the equipment you have on hand and the comfort level with each process as to which procedure to use.
You could even get lucky with just local heating and a pair of visegrips clamped onto the broken bolt, but don't force it. Discretion is you friend.

[old mart]

Try the heat first before the bother of getting the mill set up. You could put flats in the bit of bolt projecting before proceeding.

[Ian B]

I managed to get it out, different way altogether. I don't have a TIG set yet, so sadly, that was out. I'm pretty sure the bolt was titanium.

I first put the broken off head in the lathe, drilled a small hole through it without any problem. So it wasn't as hard as I thought.

I took a long M5 coupling nut, drilled it through 5.5mm. Drilled a 6mm hole into one end 6mm deep, tapped an M7 thread in it. Hardened it. I now had a drill bushing that would screw onto the stub and give me a nice central hole.

Screwed it on tight, then drilled a 5.5mm hole down the middle of the remains of the bolt to full depth. The core of an M7 thread is 5.773mm, so the thread was still just intact.

Unscrewed the nut, pulled on the remains of the stub with pliers and the thread unwound from the female hole like a spring. This left the original threaded hole intact. I ran the tap through it to clean it out, job done.

Many ways to skin a cat I guess.

Ian

[old mart]

Now you have to get a replacement bolt. You could try the car and motorcycle tuning goodies suppliers.
Run the tap into all the holes to clean the threads.
Do these rims have an o ring sealing the halves like aircraft wheels?

https://www.pwmotorsport.com/shop,bbs-products,bbs-split-rim-bolts.html

[mattthemuppet]

that's a neat solution Ian, well worth remembering. Out of curiosity, what refurbishment are you doing that requires taking the rims of the centers? Stripping and reanodising?

[Ian B]

I've found a supplier for a bolt - bolts are about GBP 2.50 each, postage to Holland is 3 times that. Good job it's titanium - keeps the postage down

The rims split into 2 parts - an outer barrel that has the inner & outer tyre bead on it (so basically a tube) and a flange that fits inside that. There's no possibility of an air leak as the joint isn't exposed to air pressure. Yes, I'm cleaning the holes out with an M7 tap when they're back from the spray shop.

The wheels are 11 years old, and the paint is bubbling, metal is corroding. It's basically a cosmetic job, and to stop further corrosion. Interesting you mention anodizing - I haven't seen that done to car wheels, although obviously it would be possible. There's quite a bit of pitting corrosion, so polishing that out would be an expensive option. There's a little bit of kerb rash, which I think 3 coats of paint will hide.

Ian

[epicfail48]

Bright white sparks are a sure sign of titanium. Steel is orange, the color is pretty constant with the only variables being the amount of sparks and how they burst. Stainless, carbon, even cast iron, bout the same color, just different amounts and burst pattern. Titanium is an extremely bright white cascade of sparks, kinda hard to look at cause of how bright it is. Its also pretty hard on grinding media

[MattiJ]

I managed to get it out, different way altogether. I don't have a TIG set yet, so sadly, that was out. I'm pretty sure the bolt was titanium.

I first put the broken off head in the lathe, drilled a small hole through it without any problem. So it wasn't as hard as I thought.

I took a long M5 coupling nut, drilled it through 5.5mm. Drilled a 6mm hole into one end 6mm deep, tapped an M7 thread in it. Hardened it. I now had a drill bushing that would screw onto the stub and give me a nice central hole.

Screwed it on tight, then drilled a 5.5mm hole down the middle of the remains of the bolt to full depth. The core of an M7 thread is 5.773mm, so the thread was still just intact.

Unscrewed the nut, pulled on the remains of the stub with pliers and the thread unwound from the female hole like a spring. This left the original threaded hole intact. I ran the tap through it to clean it out, job done.

Many ways to skin a cat I guess.

Ian

Good trick on guide bushing, have to remember that if I have one that is sheared cleanly off with part of the bolt visible.

[old mart]

You may have to mask off the mating joints, if the paint threatens to make the fit difficult. I would put a thin coating of a non setting waterproof compound all over the joint faces and threads, and treat the tightening of the bolts in a similar way to tightening a cylinder head. Diagonal tightening a little at a time to ensure the compound extrudes evenly and fully from the joint. I used to use a Makita battery drill with adjustable torque to tighten two fuel tank spacers which had mastic between them, held together by Hi Lok fasteners. The fasteners were designed to have their nuts snap at a predetermed torque, and with a thick layer of mastic and 100 bolts to tighten, they had to be tightened a little at a time as premature breaking would leave that bolt loose. These fuel tank spacers were about 3 feet long and fitted Boeing wings.

[Ian B]

Mart,

The "paint in the joint" thing was indeed a concern. The first idea was to powder coat the parts, but this either means cleaning the powder coat off the mating faces or pre-machining some metal off one of the faces. I didn't fancy either.

When I took the wheels apart, there was a layer of paint in the mating face - the OEM had obviously coated everything and then assembled, which is what I intend to do. I'm also going for paint rather than powder coat.

It is a matter of torqueing the bolts evenly, as you say. I'm planning using Loctite 222 on the bolts and packing the joints with silicone sealant. There are all sorts of gaps where water / dirt / salt had crept into and caused corrosion; I'd like to keep all of that out.

The paint shop expect to take 10 days. With this virus, everyone seems to be doing jobs that result in their cars being off the road; they must have had a dozen sets of wheels in there for recoating. It gives the replacement bolt time to come.

Ian

[old mart]

Sealing against water ingress is particularly important when using titanium bolts in light alloys.

[mattthemuppet]

The wheels are 11 years old, and the paint is bubbling, metal is corroding. It's basically a cosmetic job, and to stop further corrosion. Interesting you mention anodizing - I haven't seen that done to car wheels, although obviously it would be possible. There's quite a bit of pitting corrosion, so polishing that out would be an expensive option. There's a little bit of kerb rash, which I think 3 coats of paint will hide.

Ian

Ah, got ya. Didn't even think of powdercoating for alu/ mag wheels, but given how anodising is relatively thin and hides no blemishes at all it, paint makes sense.

As for the expensive bolt, with that many in there holding things together I doubt you'd miss one