Securing Front Hub Bolts

[Bob_Spidell]

My BJ8 has significant pedal vibration on braking. Since I bought new rotors years ago I'll install them after the engine rebuild. I've always been a bit concerned that the adapter bolts are not secured, like the studs on the rear drums; if I try to torque the nuts on the adapter the bolts turn which, of course, prevents proper torquing. I'm considering tack-welding the bolt heads to the backside of the rotors so I can re-torque the nuts without pulling the rotors. Anybody see a downside to this; e.g. could the localized heating of the rotor cause distortion or weakening of the rotor metal?

Thanks for any input.

 

[Deleted member 19315]

Bob are you concerned about the wire wheel hubs which bolt through the disc rotor. If so the stud should be a round headed design with a spine which locates in the wire wheel hub adaptor. I t should not turn when you torque the nut. If it does you need new studs which can be fitted with a Loctite retainer to help hold them. I would be wary about tack welding them into place just in case of metallurgy issues I'm not qualified to understand. !

 

[Randy Forbes]

The most recent pair of front hubs I bought doesn't have pressed in studs; I ordered "grip length" bolts and all-metal locknuts.

https://www.pegasusautoracing.com/advcat.asp?CategoryID=ANBOLT (embarrassed, now that I posted the link to an aircraft mechanic)

Personally, I'd be more inclined to tack the head of a bolt instead of a nut, but not sure if there clearance to reorient their direction. That isn't to say I'd weld on a rotor, but I'd be more inclined to weld on the hub (but that's just me...)

The black finish on the hubs & rotors is a metallic-ceramic thermal dispersant coating.

 

[Bob_Spidell]

Ha ... I've got bolts with the head inside the rotor (nuts on the outside). I think they'll go either way; dunno if they were that way originally and I just copied, or I reversed them last time I installed new adapters.

Point taken on welding on a rotor, Randy and asaad; I'm concerned welding could somehow change the metallurgy of the rotor, which might prove problematic on such a highly stressed--and somewhat important--component. But, I'd like to be able to re-torque the bolt or nut without the backside turning. Rotors get pretty hot in normal use, I'm not sure localized heating from a quick tack would hurt (but I'm also not sure I want to find out).

 

[steveg]

My BJ8 has significant pedal vibration on braking. Since I bought new rotors years ago I'll install them after the engine rebuild. I've always been a bit concerned that the adapter bolts are not secured, like the studs on the rear drums; if I try to torque the nuts on the adapter the bolts turn which, of course, prevents proper torquing. I'm considering tack-welding the bolt heads to the backside of the rotors so I can re-torque the nuts without pulling the rotors. Anybody see a downside to this; e.g. could the localized heating of the rotor cause distortion or weakening of the rotor metal?

Thanks for any input.

I would wonder if they ever get loose - especially with the AF bolts and nuts per above.

I'd be inclined to make a sheet steel retaining ring for each hub and fold the edges up to capture the bolt heads and keep them from rotating - if indeed they come loose.

Did mine with grade 8 bolts (heads inside) and all-metal prevailing-torque ("stover") locknuts. Pretty sure they're not loose after three years.

 

[Randy Forbes]

Steve's got a good idea, and who here doesn't like to make extra stuff...?

I just looked in the Parts Catalogs (original MK I/II & reprinted MKIII) and they're showing both front hub types with studs pressed in from the front (outermost) side. I guess it's just easier for the re-producers to leave the fasteners up to us.

I don't remember if I made a conscious effort to mimic the factory by putting the nuts on the inside, or just to make everything look more streamlined (hiding as much hdwr as possible) when the wheel was off.

I doubt we'd gain or lose concours points either way

 

[steveg]

Randy,
Do you happen to know the length of the AF bolts?

 

[Randy Forbes]

Randy,
Do you happen to know the length of the AF bolts?

In a word, no. I could remove one of mine and tell you what it is, and one day if I have nothing to do...

The reality is that you'll need to measure the hub and rotor that you'll be using to get the most accurate bolt-shank length. By rights, they should all be the same, but I wouldn't bet money on it!

 

[steveg]

Thanks Randy. A good idea to verify length before ordering.