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MG MGB Technical - MGB Crossmember

Is it possible to fit a Rubber Bumper crossmember to a Chrome Bumper car? I've not compared the two, side by side, but I understand that the RB one offers more room for the sump (of a diferent engine)? Is there any effect on the suspension geomerty if a RB crossmember is fitted?

Cheers... Phil.
Phil

The rubber bumper cross member has an extension to the top where it mounts to the underside of the chassis. thus hanging the cross member about 3/4 to an inch lower then the original chrome cross member. I'm doing a chrome bumper v8 roadster and have used the rubber bumper x-member to give the correct clearance for steering etc,.
Ian Sanders

Yes, the RB crossmember will fit, but I think you will need the RB steering rack as well. Fitting the RB crossmember to a CB car will give you more clearance below the engine, but will also raise the ride height by about an inch (thereby spoiling the handling) unless you use shorter springs.
Mike
Mike Howlett

Phil-
Mike is right about needing a Rubber Bumper steering rack for the Rubber Bumper crossmember as the mounts are at a different angle. You'll also need a Rubber Bumper steering column plus the lower suspension arms as well. He's also right about the effect on handling. The motor mounts are also different.
Steve S.

I'm headed in the opposite direction, changing my '80 front crossmember to a '73. I've searched the archives
and have found conflicting information. I'm planning to use the '73 rack. Will I need to use a CB column as well? Do I need to change to the early style motor mounts? I'd like to use my '80 dampers, spindle assy's
and lower control arms on the earlier crossmember.
Any problems forseen here? Thank You!
Mark Heyburn

Mark-
Yep, lottsa problems, but nothing that can't be fixed if you're willing to put in the time and effort. You will need the Chrome Bumper steering column to line up with the Chrome Bumper steering rack. You'll also need to switch to the Chrome Bumper rear spring mounts or the car will sit with its tail up in the air. Then you'll need the Chrome Bumper rear shock links and rebound limiting strap. You'll also need to shorten the rear stabilizer bar. Once you've done that you'll also need to change to the earlier front stabilizer bar type of a 3/4"-7/8" size or the car will oversteer badly. The spindles, dampers, and steering arms are the same. As for the motor mounts, which engine will you be installing, 1980 or 1973?
Steve S.

Mark,
Are you doing this for ride height sake only? The reason I ask, is that I have seen (and read in the archives) that people use shorter CB springs on RB crossmembers to lower their B's ride height. I think the MGOC even sells a complete RB to CB height kit with front and rear springs of shorter height to bring your RB car down.

jimt
jimt

Thank you for the advice.

Steve S-I'm using the '80 engine.

jimt- I'm lowering the car to match CB conversion
already completed.

Mark H.
Mark Heyburn

Mark-
Since you're installing the 1980 engine on the Chrome Bumper crossmember I'd suggest installing it with Rubber Bumper motor mounts.
Steve S.

This thread was discussed between 13/05/2002 and 15/05/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.