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MG MGB Technical - CB to RB steering rack replacement

Does anyone know if the later type RB steering rack can be bolted straight onto a CB cross member ? I realise that the shaft is longer, but that's not an issue in my case, (V8 conversion). I want to replace the lengthened shaft CB rack with an RB one.I know the mounting is different on RB racks, I just wondered about angles etc. Barrie E
B Egerton

Nope, it's not a bolt-on proposition. The angles of the bracket are different.
Stephen Strange

Unless the angles *on the rack itself* of either the mounting ears or the pinion shaft are different, I'd have said the only issue would be length as Barrie has said. But I'm only guessing. The different brackets on the crossmembers themselves are to cater for the inch or so spacer between the RB crossmember and chassis rails, and having to pass through the engine mounting bracket as a result.
PaulH Solihull


steve and Paul are both right. The job is not bolt on but it can be done. just need to make/alter rack mounts so that rb rack will mount to the CB cross member. It's done all the time by RB guys that want to convert to the CB cross member and lower the front without the associated bump steer issues or harder springs. There is a shop near me that specilaised in it. Have looked at what they do and it's tediuos but not impossible.

A J Ogilvie

Thanks for the info guys. I was thinking (& hoping) along the same lines as PaulH but no such luck.
Allan, do you know if the existing mounts are modified in situ, or are they chopped off & welded back on in a new position ? Barrie E
B Egerton

FYI the moss racks (Rubber bumper and chrome) are all the chrome bumper ratio of about 2.5 lock to lock.
Peter Sherman

Hi Barrie,

The mounts are chopped off and new ones welded in to located the rack in the right place for the column and for the suspension. I have been looking at maybe doing this for my RB. The guy that does it tells me he guarantees no bump steer and good suspension geometry. The only issue is the cost because it also includes full suspension overhaul which is expensive. I have thought about having a go myself at some point as I think you could possibly get the RB mounts to mate up to the CB cross member but not sure. Either way you will have to chop off the cb mounts and re position the rack. Still undecided.
A J Ogilvie

There were 2 main problems for the factory when fitting the V8 engine. 1, Steering rack alignment with the 1" raised crossmember 2, Moving the Steering UJ towards the steering wheel by recessing it in the firewall to clear the Exhaust manifold.
It is possible to fit the CB crossmember to a RB car without changing the CB geometry but it puts the front of the sump within 10mm of the rack.
This is how I did it.
Cut a piece of angle iron the exact length of the tube in the middle of the rack (between the alloy castings). With the CB crossmember off the car, bolt up the rack. Now position the angle iron from underneath and clamp into place. Now tack Weld strips of metal from underneath the angle back to the crossmember to hold the angle iron in place.
Next remove the rack and cut off the rack mounts. Now bolt the crossmember onto the car and sit the rack back into place on the angle iron . The rack can be rotated so that the shaft points at the steering UJ (will need length adjusting). The hole in the engine mount might need adjusting but not by much.
Re weld the rack mounts.
A lot of work but it keeps the geometry spot on.
What you must avoid is moving the rack up or down as this WILL cause bump steer.
Hope im not teaching you to suck eggs.

M Rawlins

This thread was discussed between 14/11/2010 and 17/11/2010

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