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

Alloy trailing arms on NA? Rear hubs loose.

 
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions
View previous topic :: View next topic  
Author Message
Raize  



Joined: 18 Sep 2013
Posts: 337
Location: Scotland

PostPosted: Sat May 03, 2025 7:00 pm    Post subject: Alloy trailing arms on NA? Rear hubs loose. Reply with quote

Anyone know if it’s possible to use the alloy trailing arms on the NA?
And if not, why?

My steel trailing arms are shot, the rear hub has almost 0.5mm of axial play with the hub nut tight suggesting the ball bearing outer race is just sliding around in the hub.

The stub axles also just spin in the inner bearing races and this is the same on all trailing arms I’ve seen, it’s meant to be a press fit though.

The pricing of the steel arms is just unreasonable, hundreds of pounds and might not even be decent… and the alloy ones are much cheaper and more available.
Back to top
View user's profile Send private message
Raize  



Joined: 18 Sep 2013
Posts: 337
Location: Scotland

PostPosted: Sat May 03, 2025 8:15 pm    Post subject: Reply with quote

I also don’t understand why they put a circlip in to retain the bearing if it’s meant to have a press fit and zero axial play.

I stripped down a spare trailing arm I had and the ball bearing is just loose behind the circlip too and moves 0.7mm axially between slop on the bearing itself and the outer bearing race moving. Even worse than the ones on the car. Obviously this would never go away no matter how much you tighten the hub nut.

I guess this is completely game over for my disc brake conversion as well as the discs would just move around and rub constantly.

I don’t have time or money to drop the rear axle and replace the control arms, do I just scrap the car at this point? Literally everything is worn out and the scammers on eBay want half the value of the car for a pair of rusty used control arms that will probably have the exact same issue.
Back to top
View user's profile Send private message
Cedric  



Joined: 27 Aug 2004
Posts: 2742
Location: Sweden

PostPosted: Sat May 03, 2025 8:23 pm    Post subject: Reply with quote

Are you in the UK 924OC? Thats a helpful bunch, maybe some parts hoarder can help, they are normally peanuts when they pop up on sale locally here at least. I never buy anything from eBay though, prices are hilarious.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/
Back to top
View user's profile Send private message MSN Messenger
Raize  



Joined: 18 Sep 2013
Posts: 337
Location: Scotland

PostPosted: Sat May 03, 2025 9:34 pm    Post subject: Reply with quote

I’ve investigated further and the slop is about 0.3 mm from the ball bearing itself and 0.3mm from the race moving underneath the circlip. This is on the spare trailing arm, unsure how old the bearings are in it. The ones on the car have less than 10k miles.

On further reflection replacing the trailing arms doesn’t seem like the right solution, the bearing is not meant to be retained by a press fit or it wouldn’t have a circlip. It just needs to be snug enough to not move radially.

Likewise the inner races don’t really “need” to be press fit, as long as they are snug the axle nuts hold it all rigidly together.

So essentially you would need a thicker circlip or some kind of very thin shims. I read that there were originally 5 circlip thicknesses available but no doubt NLA now like everything else. Or alternatively a very thin shims that could go on top of the bearing outer races (no doubt custom and ££££££).

I am no longer a 924OC member, that got chopped along with many other things in the cost of living crisis.
Back to top
View user's profile Send private message
Beartooth  



Joined: 05 Apr 2022
Posts: 280
Location: Roberts, MT

PostPosted: Sun May 04, 2025 4:06 am    Post subject: Reply with quote

I hear you on the cost of living stuff: I think my food costs alone have gone up 50% the last five years; pretty bad when a single guy like me starts noticing. Also that's before we get into my healthy eating aspirations, but hopefully that one has some real return on investment. Anyway, I serviced my 931's rear wheel bearings (nothing wrong that I could tell, but I'm pretty sure they'd never been opened, and 40+ year-old grease can't be as good as fresh). It all seemed pretty straightforward. I didn't find anything unusual so I just cleaned all the old grease out and put it back together with new seals. As mentioned, it's not a press fit, everything should slide right out and back in. That said, if it seems iffy, I'd replace the bearings. My memory was that they're four identical bearings, but apparently the inner is a ball bearing and the outer is a barrel roller. The outer is a 527539, the inner is a 6206; both available from FAG. The inner is very common, but not so much the outer. Could it be someone tried using a 6206 for inner and outer? I'd also buy new circlips (OE, unless you can identify the exact size). With new bearings and the right circlip, I can't see any way you'd have excessive play unless the carrier was damaged, but that should be obvious.
_________________
1980 931 diamond in the rough
Back to top
View user's profile Send private message
MikeJinCO  



Joined: 08 Jun 2010
Posts: 1244
Location: Maysville, Colorado

PostPosted: Sun May 04, 2025 7:35 am    Post subject: Reply with quote

Locktite makes a bearing gap filler. Called Locktite 660, I have used it on my 50 year old aluminum hubs on my race car that uses tiny Triumph Spitfire bearings and it seems to be working. Note that my front wheel loaded weight is about 240 lb so it doesn't need a very big bearing.
_________________
Mike


'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild)
Back to top
View user's profile Send private message Visit poster's website
Raize  



Joined: 18 Sep 2013
Posts: 337
Location: Scotland

PostPosted: Sun May 04, 2025 8:26 pm    Post subject: Reply with quote

Beartooth wrote:
I hear you on the cost of living stuff: I think my food costs alone have gone up 50% the last five years; pretty bad when a single guy like me starts noticing. Also that's before we get into my healthy eating aspirations, but hopefully that one has some real return on investment. Anyway, I serviced my 931's rear wheel bearings (nothing wrong that I could tell, but I'm pretty sure they'd never been opened, and 40+ year-old grease can't be as good as fresh). It all seemed pretty straightforward. I didn't find anything unusual so I just cleaned all the old grease out and put it back together with new seals. As mentioned, it's not a press fit, everything should slide right out and back in. That said, if it seems iffy, I'd replace the bearings. My memory was that they're four identical bearings, but apparently the inner is a ball bearing and the outer is a barrel roller. The outer is a 527539, the inner is a 6206; both available from FAG. The inner is very common, but not so much the outer. Could it be someone tried using a 6206 for inner and outer? I'd also buy new circlips (OE, unless you can identify the exact size). With new bearings and the right circlip, I can't see any way you'd have excessive play unless the carrier was damaged, but that should be obvious.


The inner bearing is at fault here for sure. Thanks for the part numbers, that will be really useful in future.

I replaced the rear wheel bearings just 10.000 miles ago with a kit (SKF I think) so there’s no faulty assembly or worn out parts. There’s absolutely no radial play when the axle nut is tight.

I suspect the root cause is the circlip supplied with the kits is just too thin, hopefully I can find a working replacement or at least one that could be sanded down to the right thickness. Might just be able to replace the circlip rather than pointlessly replacing the whole bearing assembly again. And if that doesn’t work I can try the loctite 660.

The area ratio of my rear brake pistons to the master cylinder is 2,5x and it appears the full stroke of the cylinder is 32mm so in the worst case a 0.5mm knock back on both sides would use up less than 10% of the pedal stroke to correct, might just send it and see what happens tbh. It’s not a race car.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions All times are GMT + 10 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