Alloy rear traling arm bearing seat knurling

[karose]

Hello,

I'm restoring my suspension parts on a 3.2 Carrera. I have disassembled the rear trailing arm (banana arm as some like to call it) and I have also removed a wheel bearing. I noticed that the bearing went out too easily, which caught my attention.
After inspecting the trailing arm bearing housing, I have noticed there were some repairs done in the past (probably welding + machining). I assume the bearing spun in the housing at some point so the bearing housing needed repair.

Now the bearing can be pressed into the housing too easy (80% of the way mostly by hand and the last 20% with light hammer taps). Since I don't want that the bearing will spin in the housing in the future, I would like to knurl the housing's inner diameter to get a tighter fit of the bearing. I also plan to use Loctite for a tighter fit of the bearing.




Has any of you done knurling of bearing housing before and do you have any advice on how to do it without a visit of a machinist workshop?

Looking forward to your replies.

BR, Seb.

[911hillclimber]

Seen this before but inside a 915 gearbox.

I think on the arms the bore ovalizes over the miles and 'rocks' in the housing, hence the partial loose fit you describe.

I doubt any internal knurling will stand up to the rigors of road shocks, all the small 'high spots' that a knurl gives will be flattened in part by inserting the bearing and the shocks to the bearing via the road wheel.
It will imho deteriorate over time.
I have seen solutions where lots of centre-punch dimples are hammered all over the surface of the bore (essentially like the knurl) and this has failed over time.

Last time I faced this was in my 915 transmission, two main bearings had spun.
The bores had been centre punched and had gone flat, and the bearings had ovalized their bores.

Solution was to machine the bore true and oversize by a few mm, let in a high frictiion fit sleeve and then machine the inside dia of the sleeve to give the right bearing fit.
This way all is round, tight and true.

That will be expensive.

Alternative is to see if there is a suitable bearing size that is slightly larger than the original outside dia and have the arm machined to take the larger bearing. Just Bearings website is really good for this check.

Obviously the cheapest but risky alternative is to get another pair of arm with their bearings still in the arms and hope the bearings are good or remove them heating the arms first and let the new standard size bearing into the arm again with a hot arm.

Replacement arms could be expensive, best check ebay.

Hope this helps, just my opinion.
I have these arms on my modified hillclimb car so understand the issue!

[Gary71]

The correct way is as Graham describes, however it is worth trying some Loctite bearing fit or similar first .

I had a bearing spin on my diff output shaft (literally fell off) and glued a new one back on with some Bondloc B641 (fake loctite!) from Simply Bearings and it’s still holding strong after 2000+ miles of abuse. I’m surprised, but hey it worked!

[neilbardsley]

The trouble you are going to get this right a quick fix doesn't seem like the right way. You would prefer not to take it all apart in 6 months time. I think Graham's idea of fitting a slightly oversized bearing if the way forward. Any chance of using emory cloth too see if you can fit without machining first or is that silly talk which will just misshape the hole more?

Sent from my 22011119UY using Tapatalk

[911hillclimber]

I think the bore in the arm will be oval and needs to be true in diameter and length.
Bearing fit liquid fills the oval gaps.

Depends on how oval it is.

[karose]

Thank you all for your feedbacks. I appreciate it

Since I have one SC rolling chassis at home I removed rear trailing arm from that chassis today.
Removed rear bearing an this trailing arm is ok.

So for now I decided to use this good trailing arm for my car. The one that is damaged will be repaired if needed in the future (i think loctite will be enough since the gap is not that big).

[LukasM]

Make sure you use the right Loctite, they make several different compounds specifically for bearing retention. 635 is the only one they list as "very high strength for cylindrical parts".

https://next.henkel-adhesives.com/in/en ... ort=recent

[JohnS]

Just a suggestion but can you drill, tap a thread into the bearing housing and use a grub screw (or two) to locate the bearing in the housing maybe 6mm plus loctite?