Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

Rear disc brake upgrade

 
Post new topic   Reply to topic    924Board.org Forum Index -> Performance Upgrades
View previous topic :: View next topic  
Author Message
H2OSB  



Joined: 09 Nov 2015
Posts: 8
Location: California

PostPosted: Sun May 10, 2020 2:32 am    Post subject: Rear disc brake upgrade Reply with quote

Greetings--

Has anyone come up with a bolt on solution to upgrade the rear brakes from drum to disc without changing the 4x108 bolt pattern.

Doing a search reveals this as an old topic, that never seems to have a full solution.

Thanks in advance
H2OSB
_________________
johnL (aka H2OSB)
www.superbeetlesonly.com
Back to top
View user's profile Send private message
Raize  



Joined: 18 Sep 2013
Posts: 136
Location: Scotland

PostPosted: Sun May 10, 2020 3:17 am    Post subject: Reply with quote

http://www.924board.org/viewtopic.php?t=43588

4th post down. Sounds like a lot of work, and its probably as difficult/costly to source those Peugeot calipers and discs as a 5-lug conversion.
Back to top
View user's profile Send private message
CÚdric  



Joined: 27 Aug 2004
Posts: 1998
Location: Sweden

PostPosted: Sun May 10, 2020 4:51 am    Post subject: Reply with quote

Question nr1, what do you want to achieved?
_________________
┤80 924 Turbo
Back to top
View user's profile Send private message MSN Messenger
H2OSB  



Joined: 09 Nov 2015
Posts: 8
Location: California

PostPosted: Mon May 11, 2020 1:00 am    Post subject: 924 Rear disc brakes Reply with quote

Though I absolutely appreciate the link, I was hoping for, perhaps a mix and match of, say, Audi, Porsche and VW bits for a bolt on set up.

I almost fear saying so, but this is for a VW Super Beetle application. I have 944 rear brakes and mostly 944 fronts(with 914 calipers) on one of my Supers. There are a couple issues with using 944 spindles on a Beetle, but the worst is sourcing the necessary ball joints. They come from a single company in Germany, are very expensive for what they are, and shipping is horrible.

924 spindles are a FAR better fit on a Super in that they use the same ball joints, and both 914 and Karman ghia rotors are a direct fit, as well as bolting directly to the Super Beetle strut(924/944 and late Super Beetle use the same strut housing). Unfortunately it is not possible to redrill 924 rotors for either 4x130(Beetle/914) or 5x130(obviously most Porsche).

Regarding using either Ghia or 914 rotors, some kind of adapter would be required for any caliper due to the size of the smaller diameter rotors of the 924 locating the stock caliper nearer the center line of the axle. The obvious alternative would be to simply use the 924 front brake set up as is, from the spindles out. I don't know how effective they are on a 924 in stock configuration, but they sould be quite effective on a Beetle. The 48mm piston, though large-ish for a Beetle wouldn't be quite as ridiculous as the giant 54mm pistons from the 944 that have been used many times on Beetles over the years.

The problem here is matching the rear. Probably the easiest way would be to use a Beetle rear disc brake conversion kit, and have the rotors redrilled to 4x108. I was unaware of the Peugeot caliper/disc combo but then Peugeot is an uncommon brand in the States. I always thought it would be some Audi disc, perhaps even the hub, though I don't know what configuration any Audi uses.
_________________
johnL (aka H2OSB)
www.superbeetlesonly.com
Back to top
View user's profile Send private message
Karlio  



Joined: 17 Nov 2019
Posts: 6
Location: UK

PostPosted: Mon May 11, 2020 1:28 am    Post subject: Reply with quote

Have a look at machine7.com here in Uk. They do a rear disc conversion for beetles and they manufacture the discs to suit your requirements
Back to top
View user's profile Send private message
CÚdric  



Joined: 27 Aug 2004
Posts: 1998
Location: Sweden

PostPosted: Mon May 11, 2020 2:26 am    Post subject: Reply with quote

Would be interesting to know more about the car. For a 125hp std 924 the brakes are enough even for endurance racing with the right pads. So there's not a massive incentive for a change from a performance perspective, bar the pedal feel and annoying adjustment.

Im not sure its actually better in any way, but i think the super beetle conversion kits (but with blank discs that you bore to 4x108) could work. But I guess you already seen those.
_________________
┤80 924 Turbo
Back to top
View user's profile Send private message MSN Messenger
H2OSB  



Joined: 09 Nov 2015
Posts: 8
Location: California

PostPosted: Mon May 11, 2020 1:23 pm    Post subject: 924 Rear disc brakes Reply with quote

I'm not diametrically opposed to those kits at all. In fact, the car I'm referring to(for now after the '73) currently has 4 wheel disc brakes, which are what we VW Beetle guys call "the common conversion kits". I have autocrossed the car a couple times and was actually surprised at just how well the brakes worked.

The car with the Porsche brakes (from here after, the '74), is getting a 2056cc 914 engine, thus has uprated suspension and brakes, and is currently still on jack stands in the build phase, so I cannot assess the efficiency of the brakes yet. My issue with those brakes is I spent a good amount of money and R&D time to put them together, only to discover the "kits" on my '73 are pretty outstanding and I'm not certain need any upgrading.

My Porsche brakes consist of nearly 100% fully 944 rears, which are a direct bolt on affair for any IRS Beetle. The only items that needed changing were the tube were the parking brake cable enters and the small fixture the end of the cable attaches to. Both easily changed and reasonably inexpensive. The front takes a bit more work, particularly the way I did it, and requires mods that made it less than something I want to do again.

The spindles bolt in for the most part, except they 944 uses a 17mm diameter ball joint, where the 1303(curved window Super) and 924 use a 15mm diameter ball joint. I detest having to special order the expensive ball joints. I didn't want to over brake the front of my light Beetle and had actually gathered anecdotal evidence from three different, personally respected, sources saying 914 front brakes with 944 rears is a perfectly balanced set up on a Beetle. Since I'm weird and couldn't stand the idea of a solid rotor in the front with vented rotors in the back, I researched for a way to either get solid in the back or vented in the front. In hindsite...I should have just kept solid front and vented rear and left it alone.

So I decided on vented fronts, thinking the extra thermal mass would come in handy if I were doing an autocross event where I was required to do repeated runs without enough time for the brakes to cool down.

I discovered 914 front calipers have the same bolt spacing as 944 front calipers. Also, the inner side of the 914 caliper sits 1mm further OUT than the 944 inner side. Additionally, I found out 70s 911s used a rear caliper that was the exact same casting as 914 front calipers, but were spaced to use a 20mm wide rotor. Unfortunately the 911 caliper only has 35mm pistons vs. the 914 which has 42mm pistons, so you can't just use the 911 calipers, but it was easy enough to get a set someone was selling as exchange cores and salvaging the spacers. The ONLY real issue with this was the bolts that hold the halves together.

Both the 914 and 911 calipers used non-standardized size, 7mm Ribe bolts. Now, in a perfect world, I would have been able to reuse the 911 caliper Ribe bolts on the 914 calipers, BUT the pervious owner of the 911 calipers tried to remove the bolts with the wrong tool, and 4 of the 8 bolts were totally unusable. 7mm Ribe bolts have been out of production for approximately 40 years, thus cost an arm, leg, and your first born to replace. After researching, I found others had done this widening for Ferrari rear brakes, I think, and had redrilled and tapped for either 8mm or 5/16ths(I think), but I wasn't certain taking away material was a good idea, as there didn't seem like much to spare. The alternative was to find 7mm socket head bolts in the correct length(and hardness...12.9). After a week of searching I found a company in Germany called Tola Tools. They were expensive, but only 1/4th the cost of of Ribe bolts...and from the current epoch. Unfortunately, the shipping was almost exactly the same cost as the bolts. Cry once, they say. So now I have proper width calipers for 20mm wide rotors, which is the width of 944 front rotors. In order for the calipers to fit down over the rotors, I had to have a machinist buddy take approximately 50mm off of the overall diameter, which oddly enough made them 257mm, the exact same diameter of 924 front rotors. A 1.0mm shim washers between the caliper and the mount at each bolt, and the calipers are perfectly centered over the rotors. The only other thing required was to skim a bit off the diameter of the hub so the caliper wouldn't foul the hub, and all bolted together like it was meant to be that way. It remains to be seen if my reduction of diameter reduces brake torque.

Anyway, all of that became silly after I autocrossed my '73 and found stopping power to be excellent. That said, I really want to be able to use 924 spindles on my Beetle(s. Ultimately I like to do away with the 944 spindles). No Beetle in the States ever got front disc brakes, even though we only ever got the "big" engine that was available on any given model year. The front "kits" available on the aftermarket are basically Karmann Ghia brakes.

H2OSB
_________________
johnL (aka H2OSB)
www.superbeetlesonly.com
Back to top
View user's profile Send private message
safe  



Joined: 18 Mar 2017
Posts: 173
Location: Sweden

PostPosted: Mon May 11, 2020 7:05 pm    Post subject: Re: 924 Rear disc brakes Reply with quote

H2OSB wrote:

Both the 914 and 911 calipers used non-standardized size, 7mm Ribe bolts. Now, in a perfect world, I would have been able to reuse the 911 caliper Ribe bolts on the 914 calipers, BUT the pervious owner of the 911 calipers tried to remove the bolts with the wrong tool, and 4 of the 8 bolts were totally unusable. 7mm Ribe bolts have been out of production for approximately 40 years, thus cost an arm, leg, and your first born to replace. H2OSB


Drill and retap for M8x1.0 12.9 its not a lot of meat that get lost. You can get someone with a lathe turn down the M8x1.0 to M7x1.0, it would be a bit weaker since the threads are cut instead of rolled.
Most who really is looking for the original Ribe are "originality nerds" that really wants the correct bolts.
Back to top
View user's profile Send private message
H2OSB  



Joined: 09 Nov 2015
Posts: 8
Location: California

PostPosted: Mon May 11, 2020 11:39 pm    Post subject: Re: 924 Rear disc brakes Reply with quote

safe wrote:
H2OSB wrote:

Both the 914 and 911 calipers used non-standardized size, 7mm Ribe bolts. Now, in a perfect world, I would have been able to reuse the 911 caliper Ribe bolts on the 914 calipers, BUT the pervious owner of the 911 calipers tried to remove the bolts with the wrong tool, and 4 of the 8 bolts were totally unusable. 7mm Ribe bolts have been out of production for approximately 40 years, thus cost an arm, leg, and your first born to replace. H2OSB


Drill and retap for M8x1.0 12.9 its not a lot of meat that get lost. You can get someone with a lathe turn down the M8x1.0 to M7x1.0, it would be a bit weaker since the threads are cut instead of rolled.
Most who really is looking for the original Ribe are "originality nerds" that really wants the correct bolts.


I already bought the 7mm socket head bolts some time back, so too late for me.

Yeah, with the Ribe bolts I have left, I'm going to seek out some concours 356 guy to sell them to and finance one of my son's college education. I've heard they go anywhere from $25-$40 per bolt.
_________________
johnL (aka H2OSB)
www.superbeetlesonly.com
Back to top
View user's profile Send private message
Coco_Lev  



Joined: 04 May 2020
Posts: 21
Location: France

PostPosted: Sun May 31, 2020 8:17 pm    Post subject: Reply with quote

HI,
Here you can find some parts
https://www.kerscher-tuning.de/kaefer/detail.php?lang=en&id=83
Back to top
View user's profile Send private message
H2OSB  



Joined: 09 Nov 2015
Posts: 8
Location: California

PostPosted: Mon Jun 01, 2020 3:47 am    Post subject: Reply with quote

Coco_Lev wrote:
HI,
Here you can find some parts
https://www.kerscher-tuning.de/kaefer/detail.php?lang=en&id=83


Kerscher is the single source for the above mentioned, 17mm ball joints that fit in late Super Beetle control arms, When I bought a pair originally, many years ago, they were $52 PER ball joint, and shipping was approximately $50. On top of that, they got hung up at customs in NYC(I'm in CA) for two and a half months! Very glad the car was not a daily driver.

I have since found a method, used frequently in Europe, to modify the control arms to take a slightly modified, and locally available, $15 VW Passat ball joint. However, in all honesty, I hope to put together a brake set up some day that will allow the use of the factory Super Beetle spindles, so I can have factory suspension geometry. I don't, currently, get any overly weird behavior, but I'm also no automotive engineer.

Btw, in my original description of my front brakes, I stated I removed 50mm from the overall diameter. It was, in fact, only 25mm. I took the factory 282mm 944 front rotors down to 257mm. This, by absolute coincidence, is the same diameter as unmolested 924 rotors.

Edit: Those ball joints are now $63 each. It just offends my sensibilities to pay that much for a ball joint. Not to mention shipping from Germany.

H2OSB
_________________
johnL (aka H2OSB)
www.superbeetlesonly.com
Back to top
View user's profile Send private message
winddude  



Joined: 15 Jan 2020
Posts: 54
Location: Vancouver Island

PostPosted: Wed Jul 22, 2020 7:07 am    Post subject: Reply with quote

I haven't done it, but another option appears to be Peugeot 405 disks, with a bit of machining on the drum. I looked the rotors and calipers can be found pretty cheap. http://www.924board.org/viewtopic.php?t=15634
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> Performance Upgrades All times are GMT + 11 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group