Knock on drive pins (pegs)

[bitsobrits]

The original drive pins on my S3 with the earlier flange type pin were very corroded, and I removed them to have them zinc plated. While functional, they still looked pretty terrible, and I imagine they would capture dirt and grime in all those pits.

So I orded a set from a UK supplier who sent me pins that were useless as they were much too large in diameter to fit the hub (even when heated to 400f), and in fact were too large for the wheel centers as well (two emails from them with a promise they will "do something", then silence).

So I did some research, and drew up a replacement which I had made in 303 stainless. They are about .030 longer, as I may use Minilites, and was looking for a more positive engagement. They do still look normal with stock wheels. A very nice look once installed, and should look good for a very long time.

Made up an extra set which is going on eBay when I get a moment.

[englishmaninwales]

Should these (safety critical) items made from high tensile steel rather than stainless?
Malcolm

[Elanman99]

Stainless should be fine in this position, they are in shear only and I think even brass or copper would work.

Plain steel plated is probably the most sensible, SS does not get on with aluminium if there is any water present as Galvanic corrosion is inevitable, but unless the car is in a marine environment its probably not a worry.

Ian

[englishmaninwales]

Thanks. Just shows I know SFA about metallurgy

[knockoffnut]

I would use stainless steel very happily for a road car, but would lean towards something like 4340 if I was building an all out racecar.

(years ago I culdn't even spell metalergy and now I are a engineer... )

[elj221c]

Should these (safety critical) items made from high tensile steel rather than stainless?
Malcolm

They only locate the wheel while it is being tightened. Drive pins/pegs is a misnomer.

BMS is fine or stainless if you wish.

[fattogatto]

"They only locate the wheel while it is being tightened. Drive pins/pegs is a misnomer."



It's very refreshing to find someone who really understands the dynamic of this fitment.

[Elanman99]

Two pegs would give location, add lightness, and would have saved Colin money.

I still call them drive pegs.

Ian

[fattogatto]

A rose by any other name. . .

[Craven]

Why do the LOCATING pin holes become elongated?

[fattogatto]

Because the center locks loosen. They must be tightened dry and checked reasonably often. If tight the wheels will not rotate on the hub at all, even without the pegs.

[Craven]

Would that mean they are a SAFETY device?

[fattogatto]

Call them what you will. They may serve a slight safety function in that if the wheel nut loosens some they will continue to provide drive/braking force until you can stop the car. Hopefully you will feel the wobble and pull over immediately.

However, their purpose is to locate the wheel so the wheel nut may be engaged. All drive/braking force is transmitted to the wheel through the clamping force between wheel nut and wheel.

If your wheel nuts loosen it is an indication of other issues: improper tightening, matter between wheel nut and wheel, too much anti-seize on threads, too much paint on wheels, bent wheel center from over-tightening, etc.

[Elanman99]

Why do the LOCATING pin holes become elongated?

I have seen mention of enlarged holes in wheels, (which elongated holes are) but in which direction does the elongation take place?

For the holes to get enlarged, wear must have taken place probably because the nut was not tight enough

Its a long time since my S4 had steel knock on wheels but from memory I thought the central hole was oversize and the wheel diametrical location was determined solely by the close fit of the drive pegs?

Ian

[joe7]

I thought I read something about there being 2 types/sizes of drive pins. One is stepped the other isn't.