HJ60 Front Disks from Toyota missing 2 small holes?

Aimass

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I am in canada
Sep 27, 2015
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Toronto, Ontario - Canada
Hi there!

I bought the two original front discs from Toyota Canada (which actually come from California) and when I took it to the mechanic, they noticed that the new discs were missing 2 small holes where 2 small screws seem to hold the hub and the disk together from the back. The mechanic refused to install the new discs until we have more information. I went to Toyota and those are the correct replacement parts, so not sure wtf.

I don't think those 2 little screws do much because the actual force should be held together by the studs themselves, but honestly don't know what to do. I can't return the discs anymore.

Has anyone run into this situation, is this more or less normal?
Is it safe to install without the 2 small screws ?

TIA!!
Alex
Toronto, Canada
 

flint

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Mar 11, 2014
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If the holes are threaded, they're there to separate the disc and hub. If no threading, they're (as you said) just to take a screw to keep the disc in place with the wheel off.
 

Aimass

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I am in canada
Sep 27, 2015
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Toronto, Ontario - Canada
Thanks both for your prompt replies. I have attached a diagram that shows the missing hole. I think they are threaded on the disc itself. It seems to hold the hub to the disc but I believe the studs also do that. Toyota insists that is the correct SKU, so maybe the replacement doesn't come with those?

HJ60FRONTBRAKEDETAIL.gif
 
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Chris

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I'd see that simply as an indexing or alignment device. It's got nothing to do with holding the car together for sure. 60's aren't my thing but generally speaking the disc would go OVER the hub from the front and the wheel studs would be pressed from behind into the hub. This means that the disc is held on by the actual wheel itself. So, if you pull the wheel off, the disc wobbles about being checked only by the caliper. In that, having a small grub screw to hold it in place during wheel changes is something quite common. This set up is clearly a reverse and it's possible that on later discs (which might fit other models) Mr T realised that it didn't need these screws and saved the money on tapping out the threads. See this hub below, the disc fits over the studs from this side not behind the hub. However, similarly, when pressing the studs through the disc into the hub from the rear, having an alignment screw would still be a handy thing

Screenshot 2019-11-27 at 16.04.46.jpg
 

Rodger

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I have 60 series axles which are the same as 40 series except 70mm wider. I changed my discs and studs about 10,000 kms ago.
These holes are for separating the hub nose from the disc and alleviates the need to hit the expensive hub nose with a blunt screwdriver and a big hammer. They make no difference to the mechanical performance of the disc or hub, When you put the new discs on you ease them on with equal pressure on the disc edge as the holes are machined for the studs. So how strong are the studs - if you are going to change them you'll need a 20 ton press!
My new discs did not have the holes in question so I checked and and if the hub nose is stuck use a puller.

Regards,

Rodger
 

Aimass

New Member
I am in canada
Sep 27, 2015
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Toronto, Ontario - Canada
Hey guys! Thanks A LOT for all your replies.

@Chris not sure what you mean by "the disc would go OVER the hub", I am guessing it's a terminology thing... when we took it apart, the flange is in front of the disc and the studs are pressed through the disc and pressed into the flange (see link below) (i.e. if you put a stud directly through the disc without pressing through the flange, the stud would fall right off).

I completely agree these small screws are not structural and seem to be some sort of alignment device, maybe for keeping the flange and disc together to facilitate the pressing of the studs into the flange, or for separation as @Rodger suggests.

Here is a diagram comparing the FJ40, 60 and 80 in different years:

https://www.fjparts.com/disc_front_axle_hub_diagram.htm

If you look closely, the 40 series before 8/1980 had no such threaded hole nor screw. Then, from 8-80 for BJ42, FJ40 as well as FJ60, HJ60, BJ60, FJ62, FJ80, and up to 1990, they have the freakin small holes and screws. Then after 1990, they seem to disappear again.

So my conclusion is that I can safely install the new disks and ignore the 2 alignment screws, although my flange will still have the 2 holes.

One last question: can I re-use the old studs or is it always mandatory to replace the studs?

Thanks again!
Alex
 

Chris

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Don't worry, I was actually confusing two different things actually. I've had coffee since then. However, there is a difference and you can see in the diagram that on the 60, the studs pass through the disc and the hub from the rear. On the 80 they don't. The hub is bolted to the disc and the studs are captive only in the hub - in effect there are two full sets of fixings.; 6 studs and 6 bolts.

It's not mandatory to swap out the studs, but I think there is sufficient body of evidence to show now that after 20+ to 30 years of use, studs fail. I swapped all of mine last year for genuine ones prior to a very hard trip across Northern Russia. I didn't want to take the chance. But I knew that mine had really had a hard life.
 
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