jimgiblett
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| posted on 1/2/11 at 11:25 PM |
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PLug welding discs 5 stud to 4 stud conversion
I am wanting to use some vented discs on my old 1967 Alfa project car. The dimensions are ideal but they are 5 stud rather than the desired 4. Many
people redrill disks but I was wondering what peoples opinion of plug welding the stud holes before redrilling. Good idea or not?
The PCD is 114.3 x 5 and will be 108x4 so pleanty of distance on all but one stud hole.
The expensive route is a £1000 disc conversion I am looking for a lower cost solution.
Thanks in advance
- Jim
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mookaloid
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| posted on 1/2/11 at 11:45 PM |
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Just my gut reaction - I would have thought it would be ok without welding. If you are careful about it and bear in mind which way the disc rotates
when drilling the holes so that you don't leave a very thin bit in front of the stud (rotationally), and bearing in mind it will be clamped in
place with the wheel anyway.....
Of course I could be wrong. 
"That thing you're thinking - it wont be that."
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Chippy
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| posted on 1/2/11 at 11:48 PM |
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I would say that welding is a definate No No due to heat distortion, you would end up with a very wobbly disc. IMHO Ray
To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy
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mcerd1
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| posted on 1/2/11 at 11:53 PM |
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I thought most discs were cast iron - that doesn't lend itself to welding easily apart from anything else
so if you've got plety space between the new and old holes then I'd just leave them alone
what car do the new discs come from ?
[Edited on 1/2/2011 by mcerd1]
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blakep82
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| posted on 2/2/11 at 12:03 AM |
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i wouldn't go welding brake discs...
http://www.driftworks.com/shop/4-to-5-stud-conversion-25mm-nissan-wheel-spacers.html
think that shows that with some careful drilling, it could work, yes, 2 of the studs are close to the 4/5 stud equivalent (which ever way you look at
it) the discs are held by the wheels, 2 of the studs will still hold the disc in the even of the other 2 failing, even then, i doubt both would fail
given one is before a hole, the other after the hole. and with a different PCD, there should be a little more meat between the stud and hole than
there is in that photo...
careful drilling should do it
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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Uphill Racer
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| posted on 2/2/11 at 12:24 AM |
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I brazed mine before re drilling but they are bike disks.
[Edited on 2/2/11 by Uphill Racer]
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Daddylonglegs
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| posted on 2/2/11 at 07:26 AM |
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Can new discs be that expensive? Personally, when it comes to brakes I would sooner know I have the correct discs (and new ones) fitted rather than
have that nagging 'what if?' in the back of my mind whilst driving.
Just my opinion of course
It looks like the Midget is winning at the moment......
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phelpsa
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| posted on 2/2/11 at 09:06 AM |
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quote:
Originally posted by Daddylonglegs
Can new discs be that expensive? Personally, when it comes to brakes I would sooner know I have the correct discs (and new ones) fitted rather than
have that nagging 'what if?' in the back of my mind whilst driving.
Just my opinion of course
Custom discs can be very expensive!
Don't bother welding, just drill. The holes are only there to let the wheel studs poke through, they dont do any locating or anything. Do,
however, make sure that the centre bore is the same and the disc is located centrally!
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thefreak
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| posted on 2/2/11 at 09:33 AM |
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I have found you can get a clunk from the disks if the PCD on the disk isn't the same as the one on the hub, as the caliper stops the disk and
the hub still rotates round.
Custom disks with aluminium bells start from around £250 and go up depending on diameter/thickness. Replacement rotors start around £65 each from
memory.
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jimgiblett
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| posted on 2/2/11 at 10:27 AM |
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quote:
Originally posted by Daddylonglegs
Can new discs be that expensive?
The discs are brand new brembos. The problem is there is no off the shelf "big" discs for my application (1960s Alfa) unless I go for a
custom bells and rotors which gets very expensive.
The general consensus seems to be to drill and not plug.
Thanks
Jim
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thefreak
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| posted on 2/2/11 at 10:28 AM |
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Did you get my U2U?
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jimgiblett
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| posted on 2/2/11 at 10:44 AM |
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quote:
Originally posted by thefreak
I have found you can get a clunk from the disks if the PCD on the disk isn't the same as the one on the hub, as the caliper stops the disk and
the hub still rotates round.
Custom disks with aluminium bells start from around £250 and go up depending on diameter/thickness. Replacement rotors start around £65 each from
memory.
Fortunately the studs are fixed in the disk and there is a hat which connects to the hub so little chance of movement. The redrilled PCD will be the
same as the hub.
The depth of the bell made custom bells expensive and the rotors diameters are not ideal for 15" wheels (ie smaller or much bigger than what I
wanted 290mm). There isnt sufficient friction area on the rotors to turn them down to a smaller diameter.
You then have to add on the machining time, NAS nuts and possibly calipers. Caliper compatibility (will probably have to purchase new radial
calipers) My route uses ali Mazda RX7 calipers and discs which I already have.
- Jim
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thefreak
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| posted on 2/2/11 at 10:49 AM |
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There are rotors available in the sizes you're looking at. I believe the RX7 (FD) calipers use a 292x22mm thick front disk with a 67mm offset
yes?
Are you making up adaptors to fit the calipers to the hubs? if so are you able to space them out to a 298mm diameter?
Whatever the options, you're looking at a LOT less than £1000
[Edited on 2-2-11 by thefreak]
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jimgiblett
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| posted on 2/2/11 at 10:53 AM |
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quote:
Originally posted by thefreak
Did you get my U2U?
Sorry just picked it up. Have replied.
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rossnzwpi
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| posted on 11/2/11 at 08:49 PM |
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4 to 5 stud geometry
Hi, My 2 cents worth:
Quote:
_______________________________________________________________________________________________________________
i wouldn't go welding brake discs...
http://www.driftworks.com/shop/4-to-5-stud-conversion-25mm-nissan-wheel-spacers.html
think that shows that with some careful drilling, it could work, yes, 2 of the studs are close to the 4/5 stud equivalent (which ever way you look at
it) the discs are held by the wheels, 2 of the studs will still hold the disc in the even of the other 2 failing, even then, i doubt both would fail
given one is before a hole, the other after the hole. and with a different PCD, there should be a little more meat between the stud and hole than
there is in that photo...
_______________________________________________________________________________________________________________
the photo in the link is about changing from 4 to 5 stud where both have the same PCD. This means that one stud remains in the same place for the
swap. If the new PCD is to be different to the original PCD, as per the original question in this thread, then it may not be possible to do.
Just draw it on paper and see how close the new holes need to be!
Cheers
Ross (in NZ)
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