Alloy wheel bolts. How long should they be?

[Thotos]

My Trevi is fitted with the 8 spoke Beta alloy wheels. I know that before I've owned it, the car has had different wheels fitted in the  past and I think my alloys might be fitted with bolts intended for steel wheels.  The bolts currently fitted to my car are 35mm long from the base of the bolt head i.e. the long straight bit. The hubs of the Trevi seem to have spacers fitted so the threaded part doesn't start at the point of contact with the wheel. So it seems that less than 10mm of the thread of the bolts actually hold the wheel and that doesn't seem enough to me. I made some basic checks this evening and it seems to me that I can fit 45mm bolts to the rear hubs at least (I'll check the fronts tomorrow). But coming to my original question in the subject of this thread, how long should the bolts be for alloy wheels?

[MattNoVAT]

Theo,

I went through this not so long ago, as I have the 5mm spacers fitted on both my coupes and I was concerned that the 30mm bolts were not long enough.

Your measurements are spot on, the length is based on the threaded section starting at the end of the taper.

I spoke with a friend of mine who has a wheel refurb business. He advised that a wheel bolt needs to go through eight full rotations to safely secure a wheel.

Be careful with using really long wheel bolts as you can lock up the wheel because the tip of the bolt protrudes out the back of the hub and locks off against the carrier.

The 30mm bolts are for either steel wheels or 8 spoke alloys with no spacers, if you fit spacers then 35mm wheel bolts are needed.

I've run my red coupe with 35mm bolt with no issues for the past ten years and I recently bought a new chromed set for the blue coupe for £40.

[WestonE]

The engineering definition/ rule of thumb is there must by 1.5 x the diameter of the thread engaged in the hole as a minimum. A brief coat of typex on a cleaned bolt thread will show you how much you have. PS clean it off again.

Eric 

[rossocorsa]

I remember changing a berlina from steel to alloy wheels the original bolts were not long enough I had to substitute bolts off a coupé

[Iain]

Theo,

I went through this not so long ago, as I have the 5mm spacers fitted on both my coupes and I was concerned that the 30mm bolts were not long enough.

Your measurements are spot on, the length is based on the threaded section starting at the end of the taper.

I spoke with a friend of mine who has a wheel refurb business. He advised that a wheel bolt needs to go through eight full rotations to safely secure a wheel.

Be careful with using really long wheel bolts as you can lock up the wheel because the tip of the bolt protrudes out the back of the hub and locks off against the carrier.

The 30mm bolts are for either steel wheels or 8 spoke alloys with no spacers, if you fit spacers then 35mm wheel bolts are needed.

I've run my red coupe with 35mm bolt with no issues for the past ten years and I recently bought a new chromed set for the blue coupe for £40.

I'm looking to buy a new set of bolts to go with my nicely refurbed wheels.  Can you confirm the size?  As far as I understand they should be 12mm diameter with a 1.25mm thread pitch and have a 17mm head.  The supplier has asked about the seating against the wheel, am I right in saying it's a 60 degree tapered seat?

Cheers 

[MattNoVAT]

Correct 60 degree taper, as stated earlier - I've used 35mm bolts with the 5mm spacer fitted with no issues for years.