Dimensions for 944 hub machining

[Sunroof53]

Hi,

I am buying some brakes from an 86 944 (single piston ).Has anyone got a drawing or dimensions to modify the front hub for a ball joint beam.I probably could work it out but as this is a popular mod i am sure somone has the details to give as close as stock wheel offset.Also can you use the porsche bearings for the back as well as the front .I am aware that you have to make a sleeve for the front (outside) bearing.
I have done some research but cannot find the hub mod dimensions.

thanks in advance.:)

[ricola]

I have drawings on my site, look in the speedster bit...
Rich

[DORIGTT]

What was your change in track over the stock setup?

What about the spindle modification?

[Sunroof53]

Sorry mate i havnt done it yet!

[Sunroof53]

I have drawings on my site, look in the speedster bit...
Rich
Thanks Ricola ,Your site is has been an inspiration .I Was a toolmaker many years ago ,but still have access to a lathe in my maintenance dept, so i can do the machining myself.Are both the inner and outer bearings vw and are they drum or disc bearings ?not sure if they are the same.Just had one hickup though,i hadnt realized you use a drum stub axle and i have two sets for discs only ,so now need to find some more!Thanks again.

[DORIGTT]

I apologize Skeeter, the question was directed toward Ricola.

[ricola]

I'm pretty sure that VW drum/disc bearings are the same so that bit's easy. From memory the increase in track was about 9mm?

What about the spindle modification? It was only a matter of spotfacing the mounting face and grinding down a bit for clearance..

Rich

[old gh bug]

I have just done this conversion and used ricola's excellent drawings i have a nice set up now like you i went and got disc stubs for some reason thinking that was what you needed . when you get the drum stubs you might find that you have to machine down the backing plate locating ring as my hub was just catching also used the dimensions on here for the caliper adaptor plates

Sorry for the rusty pic garage got flooded
http://i104.photobucket.com/albums/m191/huntgs/944hub.jpg~original

[Sunroof53]

Thanks for the pic ,
I spent some time at the weekend measuring my disc stubs to see if i can use them .I have figures out that i need to drill the two M10s for the bracket 8mm in front of the back plate mounting holes which have the same pitch of 56mm .What i did find strange is that the mounting point measured from the rear bearing shoulder to the caliper mount is the same .This means that i need to gain the 10mm for the bracket.I can gain the 3mm from deepening the hub and the rest from machining the stub axle as you did the drum one .This leaves 10mm of tapped hole for the bracket and makes the caliper sit as the original spec.Of course i then have to cut the original vw mount back.Incidently i have build up up my stubs with weld and machined to use the porka bearing .I may regret this as it seems to use an imperial race 3/4 and 1"1/4.

[old gh bug]

I like the idea of that i did look at using disc stubs first of all but had a set of drum ones laying around so i took the easy route
Iwould be intersested to hear if the welding works as i think i would prefer that to the spacers i have used

[Sunroof53]

I have nearly completed the disc stubs and will post a picture soon .The built up diameters seem ok ,although i did make a spacer for the seal diameter .I did also
have to plug the 7mm tapped hole for the original back plate, as it would just break into the caliper bracket mount holes.What is apparent is the far graeter amount of surface area for the bracket to sit on compared to the drum axle.
I am looking forward to getting this sorted but i still have to narrow the rear trailing arms to finish the major bits .

[Chris Percival]

I have just done this. Write up to follow soon on www.fastbug.net. 944 aluminium hub machined and then fitted with steel inserts to take beetle bearings and oil seal. Drum axles used and all I need is the correct shape steel plate and a spacer to hold the brake caliper. I created detailed CAD drawings which I will also make available.

[Sunroof53]

Thanks ,I went down a diiferent route and used the porsche bearings .Those beetle ones look very small in that 944 hub.

[Chris Percival]

The bearings are not carrying any more weight, so why not use beetle ones.. :)

Here's my solution. Full write up at http://www.fastbug.net/node/219

Using this image you can see the difference between the beetle spindle and Porsche hub.

http://www.fastbug.net/drupalfiles/images/hubspindle.preview.png

Spacers where created to go into the hub to hold the beetle bearings. The hub was shortened at the back edge and a spacer inserted to hold the seal.

http://www.fastbug.net/drupalfiles/images/IMG_3146.preview.JPG
http://www.fastbug.net/drupalfiles/images/IMG_3148.preview.JPG

The result? Custom hubs that use beetle parts, but allow the mounting of a Porsche disc, and with minimal track increase.

Chris aka CSP

[Chris Percival]

I need to use cap screws to hold the caliper mounting plate on to clear the hub. the Porsche dust cap clears the beetle locking nut easily. It might have been easier to mount the caliper with radial mount caliper and disk brake spindles but these calipers were cheap as chips so this was my chosen path..

[Sunroof53]

Heres some photos to show the vw disc spindle built up to porsche diameters (welded and turned between centres).I took 3.5mm from the back of the hub and rear counterbores .Made spacer to move front bearing forward 2mm to correct the pitch as much as i could.Made a spacer for the seal diameter to use 62x8x45 seal.This increased the track by 3mm each side.If i did another i would probably try it the way you did .It was basically easier for me to do it this way ,as i could do it myself.Did you use a back plate ?
http://i44.photobucket.com/albums/f30/sqeeter/DSC02687.jpg~original
http://i44.photobucket.com/albums/f30/sqeeter/DSC02681.jpg~original
http://i44.photobucket.com/albums/f30/sqeeter/DSC02682.jpg~original
http://i44.photobucket.com/albums/f30/sqeeter/DSC02686.jpg~original

[Sunroof53]

What was your change in track over the stock setup?

What about the spindle modification?

I can answer that now .It was a 3mm each side.

[Chris Percival]

Yeah, good work. A very neat solution, I like your caliper mounting bracket, I think mine is going to be harder work! :)

[Chris Percival]

I have added pictures showing the tools that where made up in order to machine accurately.

http://www.fastbug.net/node/219

[Sunroof53]

Thats some jig your using ,but i guess your mass producing them .I didnt realise you were a buisness .I used soft jaws machined to the front boss dia and faced them so the hub sits squaure .I didnt have to machine the front just make a bearing spacer.I guess from the pictures you press the insert in with the bearing c/b under size and finish machine that in the fixture.
Many thanks Chris .

[Chris Percival]

No its not a business.. The machining was done by a friend of mine, these are his jigs that he made in order to do it for me.

The bearing inserts where made on the lathe, then pressed in complete. The bearing spacer is separate as it had to be made from aluminium so it doesn't rust..

[wrljet]

The bearing inserts where made on the lathe, then pressed in complete. The bearing spacer is separate as it had to be made from aluminium so it doesn't rust..

Chris,

How do you get repeatable centering with that fixture held in a 3-jaw chuck?
(or is accuracy beyond the 3-jaw not an issue for the machining required on the hubs?)

Bill

[Chris Percival]

Hi Bill, not sure why you'd need repeatable centering, please elaborate?

[wrljet]

Hi Bill, not sure why you'd need repeatable centering, please elaborate?

A normal 3-jaw chuck only centers a part to within a few thousandths.
(of course some are better and some do have adjustable centering)

Say you check a bar and turn it round. Remove it and put it back into the chuck. Chances are good if you put a dial indicator on it, it's not centered anymore.

It looks like the same situation exists with the hub holding fixture in your pictures. Once that fixture is removed from the chuck, it'll be hard to get it back in again centered precisely the same way.

Thus, not repeatable.

Bill

[Chris Percival]

Ah I see, for machining both ends of the hub. I don't think it was ever a major issue, he just had to centre it as best he could every time he fixed it to the mounting tool and chuck. Resulting run-out of it all assembled was 0.01mm, so I guess he did a good job of that.. :)

[wrljet]

If I understand the mods to the hub, the overall runout of the entire system will be a function only of the accuracy of the new bearing spacers (and of course the original parts' accuracy).

Very nice job, BTW.

Bill

[Chris Percival]

I think the run-out we measured was on the face of the brake disk as bolted to hub (so 'wobble' if you like), not run-out at the circumference (from centering errors), but both could be effected by centering errors, and bearing spacer inacuracy as you say. Thanks, but he takes all the credit for the machining, I was just mad enough to envisage it all working... :)

[wrljet]

I'm a hobbyist machinist and 0.01mm is accuracy I can only read about, not something I achieve. ;-)

FWIW, I just looked up the Porsche specs for runout in the 996 Workshop Manual.

Lateral runout of the brake disc, max. - 0.03 mm
Lateral runout of the wheel hub, max. - 0.03 mm
Lateral runout of the brake disc when installed, max. - 0.06 mm

Maximum permissible radial runout and lateral runout of the light
alloy wheels = 0.7 mm.

Bill

[Chris Percival]

Yeah, I think I remember us reading up on the Porsche specs and feeling chuffed with ourselves that we came in within them.. :)

[wrljet]

Also, the Porsche specs (996) are set for the car going 175 MPH.

I just checked a recent Chrysler book and they spec 0.08mm lateral at the hub.
That's almost 3 times what Porsche wants. And 0.13mm at the rotor.

Bill

[kombi211]

i have some videos on youtube under kombi211 where i modified my hubs as well i used the stock vw inner bearing and machined
.
the hub a lot like the above but i used stock vw drum brake seals which are the same od as the 944 hubs and a off the part shelf for the outer bearing i had a spacer made and used stock 944 outer bearing lease machine work needed for that. i used 996 rotors and machine there OD down and there thickness as well. And using 944 4pot brembos....