Rear Disc Brake Conversion

[2002isGuy]

Hello All,

 

So I gathered up all of the parts I needed to do the VW rear disc brake conversion aside from brake lines. Yesterday I dove in disassembling everything, and was curious to see how much machining my rear hubs would need. When I started doing measurements, I realized something was wrong with my parts.

 

It seems that I can't use these VW rotors I bought over a year ago. My hubs measure 142mm's wide, and inside my rotors, they measure 125mm's. Look at these pics below. That means to use these rotors, I'd have to have to have 17mm's machined off, and that would get into the wheel studs. WTF!?

 

My rotors are solid, cross-drilled and slotted, and for a 1980 VW Rabbit and they measure 239mm x 12mm. I don't get it... What's the fix here? Anyone...

 

Barry

[Tommy]

Doesn't that disc have the same 4x100 bolt pattern? They seem to fit, right? Are you perhaps confused by diameter/radius dimensions?

[stephers]

Actually, it is only 8.5 mm that you are taking off to reduce down to 125        Taking 17mm off would reduce it by 34mm        

 

Thanks, Rick

[2002isGuy]

Okay, now I'll stop freaking out... So I just need to get a machine shop to turn these down 8.5mm's and I'm good?

 

Barry

[stephers]

Yep, I would take the rotor with me to the machine shop at the same time, just to make sure it will slide over the hub without any binding

 

Thanks, Rick

[2002isGuy]

Sounds like a plan. Now to locate a good machine shop locally. Thanks Rick.

 

Barry

[Son of Marty]

There's a chamfer on the backside of the hub and it's just about the amount that needs to come off, if that's starting to look a little dicey you could turn some off the hub but I've not seen a mismatch that needed that.

[2002isGuy]

Thanks. I only have one hub off for now. After I get the other one off, a shop I spoke to earlier asked me to bring the parts to them and they'll quote me a price.

 

Barry

[Georges]

I couldn't find a shop that would do it. I ended up using my bench grinder since the job doesn't have to be perfect.

[BeMyWay]

Is the opening in the rotor large enough to accept the hub center and allow the rotor & hub surfaces to fit flush against each other?

[Cabbage Fumes]

IE used to offer that service, maybe give them a call.

[PhilC]

Find a friend with a lathe and ask them to do it (or do it yourself). I did my own on a newly (second hand) bought lathe and it took 20 minutes, easy peasy.

[TobyB]

If you're handy, there are lots of ways to cut the hubs down a bit.

 

The first time I did it, I think I roughed it with an angle grinder,

then made a sleeve to mount the things in a drill press,

and used the angle grinder to round it off nicely.

 

When I was finished, it looked like it had been done by someone

who knew what they were doing!

 

t

 

Edited February 21 by TobyB