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vented brake discs mystery


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Hi,

a TR mate asked me and other TR friends to join a new project: to modify existing vented brake discs to fit our TRs.

I don't want to go this way - but it's an interesting project, so I suggested to use these discs.

The offset is 100% correct, some other details we have to change.

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My part is to change them from 5 studs to 4 studs (because I promised this is no problem...)

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I failed with the suggestion to make 3 new drills and move the one on the top with a file (sometimes I'm so simple minded...)

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So next I suggested to close all 5 of them with plugs (interference fit) made of cast iron (GG25) and drill like this:

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The new drills are overlapping in the original ones for about 1.25 mm;

so I ordered a bar of cast iron and this is the second plug (the first sadly dropped through)

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fits

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Making one means - to make 9 more (the boring part of the project).

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To press them in I use my old lever press, 50 Euros from eBay some years ago

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ready, but for marking them for the new drills I have to make a tool, my lathe is too small to use it for this

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Any thoughts and suggestions about this are welcome.

Ciao, Marco

Edited by Z320
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Hi Marco,

3 questions 

1 - are you plugging the holes simply to fill them in or is there a strength gain etc

2 - are the new holes for the TR on the same PDC as the BMW holes.

3 - are the BMW stud holes the same diameter as the TR holes.

 

Roger

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Hi Roger,

1 - I'm plugging the holes 1st to avoid the drill moving out of center 2nd to keep the disc balanced.

2 - the pitch diameter circles of the 5 / 4 holes are different

3 - the diameters of the holes are also different

4 - why you are asking for BMW?

Ciao, Marco

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If you rotated your 4 new holes a farily small amount would the then clear the existing 5 holes ?

Bob.

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Is your challenge to drill the 4 holes in the correct places and your lathe has too small a height from bed to centre, thus not allowing the disc to be mounted?

If so I would think about making a stepped bar (73.5mm to 79.5mm) that both the vented disc and the original TR disc will mount on concentrically using their round centres as registers. 

Fit the two disc types to the bar so their flat faces are in contact.

Turn up a guide bush to fit the attaching bolt holes of the TR disc and drill through it into the new disc one hole and then clamp the two discs together with a nut and bolt.

Now drill the remaining holes using the guide bush and finish to size as required.

Next step is to create a sleeve or ring to fit concentrically between the TR hub disc location register and the new vented disc bigger centre locating hole. 73.5mm bore and  79.5mm external.  Glue it in the new disc or on the hub, whichever you fancy.

Job done.

 

I am doing something very similar to this at present as I have a lathe with a 1.5" x 8 tpi threaded chuck location that has a 1.5" plain location register.  It is the 1.5" diameter register on the lathe headstock spindle that keeps the chuck running true, (like the hole in the middle of the disc does on the hub - the bolts only hold the thing from rotating)  I recently bought very cheaply a new 4 jaw self centring chuck with the correct 8 tpi threaded backplate but that chuck backplate has a location register bored to 1.875", so it will never run true if I rely on the spindle thread alone.  I made a sleeve with 1.5" internal, to fit the lathe spindle, and an external of 1.875" to fit the new chuck and backplate.  Result is the chuck will run concentric to the lathe spindle.

Cheers

Peter W

 

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Hi Peter,

good advice, but I have no TR brake disc around here.

Only some things I throw away, some months ago sadly my old discs have been one of them....

But I have a different idea. And the centering diameter of the TR is lager than the one on the vented discs.

Another mate takes over with his lathe to do this job.

Thanks a lot.

Marco

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Nice project Marco,

How critical is the exact pitch circle and diameter for the new holes?

Not too critical if it centers on the central bore, I guess.

If so, I would not worry much but having the plugs in the original holes to get a nicer hole is a good idea.

Make sure to avoid stress risers and the wheel is not contacting in the holes too much (although the are filled).

What is costs of vented disks that are a straight fit?

Cheers,

Waldi

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12 hours ago, Z320 said:

Hi Roger,

1 - I'm plugging the holes 1st to avoid the drill moving out of center 2nd to keep the disc balanced.

2 - the pitch diameter circles of the 5 / 4 holes are different

3 - the diameters of the holes are also different

4 - why you are asking for BMW?

Ciao, Marco

Hi Marco,

I am doing a project at the moment that involves a BMW E43 door window motor. I have BMW on my mind (Catchy tune title)

You do not need to fill the existing holes to keep it balanced but if the new/old holes interfere then that is different.

Waldi,

the EBC vented discs go for apprx £150/pair.  A more cost effective disc that fits with a little bit of work could be a good plan 

 

Roger

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28 minutes ago, Waldi said:

Nice project Marco,

How critical is the exact pitch circle and diameter for the new holes?

Not too critical if it centers on the central bore, I guess.

Cheers,

Waldi

Hi Waldi,

you realized this absolutely correct.

Ciao, Marco

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27 minutes ago, Waldi said:

Not too critical if it centers on the central bore, I guess.

do not rely too much on this. not all hubs fit perfect. I would prefer to have the 4 holes in relation to the center to be as accurate as possible.

 

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Roger,

on your link you see photos of vented discs,

but by the text / discription they are standard / solid discs (for very much money)

Please let me know if you read the discription different.

Marco

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Why that complicated?

meanwhile about 10cars adapted my use of the Cosworth discs.

They are 4 hole and do not look that ugly when redrilled.

 

For centering I have a very simple tool:

I made an emergency wheel from Volvo with 114,3 x4 circle and

did a fine job with my finebalancer to balance at the car.

Swapping the wheel into several positions you find it properly balanced.

 

Than you fit the new disc to the flange and to the car, fit the wheel and balance.

Difference is not to put weight to the wheel but cut material from the disc with a grinder if necessary.

 

Not that necessary and in most cases not that amount but as it is easy done I grind it to perfection.

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39 minutes ago, JochemsTR said:

GD199 and D203 are NOT vented discs.

Hi Jochem,

the pictures with the advert showed vented discs, as does the EBC web site.

However I can accept that these are general pics.

Thanks for making me aware.

Roger

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Note in Jochems picture the EBC disks are 4 mm (!) thinner (20 vs 24 mm); It can only mean less cooling or less “meat”.

Waldi

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Hi Andreas,

with the Ford Sierra discs you need to make a distance shim?

Or is this not the case?

My intention was not to need that, this is also an effort, same-same but different.

And to plug the holes was little effort.

Ciao, Marco

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Hi,

this will be my center and pre drilling tool

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This gives me the possibility mark the drills very easy, check the distances before drilling and finally drill very fast.

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By marking through the 4 drills with diameter 4 mm with a pencil,

then turn it in the other 3 positions, the marks must always be visible the same way.

This was the case ready to pre drill with diameter 4 mm

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then 9.6 mm

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ready to go out tomorrow the be modified on a bigger lathe

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I hope they fit to the calipers, we are not 100% sure, please realize this before you go this way.

Ciao, Marco

 

 

 

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Your definitely going to have to modify the calipers if your using original type anyway.

Stuart.

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