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MG MGB Technical - Rear bumper alignment

Hello all,

I am nearing completion of my restoration project and have found the rear bumper over-rider fouls on the petrol cap. I understand that the car was in an accident prior to my ownership and the rear got slightly shunted.

I believe this issue results from some deformation to the spring bar as I have played around with spacers at the mounting to push the bar out which has helped to an extent but not as much as I require.

I am hopeful that someone out there might be take pity and provide me with some measurements etc of a known "good" spring bar so that I can bend mine as required to match the correct profile.

Cheers all!
C Brennan

Picture? Overrider type? Petrol cap type?

The top of my 73 overrider is 3 1/4" from the rear panel, and the bottom 1 1/4". The minimum distance between cap and overrider is 1 1/2".

My bumper goes under the rear panel by 1/4". You could adjust the bumper bar to push it out as much as you like, but I wouldn't want there to be a gap between the two when looking down vertically on it, and especially not a gap between the bumper and the bright filler piece immediately inboard of the rear light 'hulls'.
Paul Hunt

You will probably need to twist, or otherwise bend the bumper bars, especially if they have been "thumped". Even if you buy new ones they always need "manipulating".
Allan Reeling

Thanks all,

Unfortunately I only have pics prior to restoration excitement where it is actually fitted.

The top inch or so would just come into contact with the filler lid, as you can see in the pic. To remove the cap for fills I had to ease it off to one side.

As you can see by pic 2 the bar used to sit at a bad angle also further confirming the hit to the rear.

I feel that the spring bars have been distorted by a reasonable hit.

Cheers,


C Brennan

Looks like a couple of things going on here. Have just had a look at both my cars, they have both plain and rubber insert over-riders. The plain ones are "after market", the insert ones original. While there is no chance of a problem with the OE ones (big clearance), the plain after markets are very close to the filler, not unlike yours. On measuring the bumper "recess" on the plain ones is deeper than the OE, throwing them 20mm closer to the front of the bumper and hence the filler neck. Now this might be a problem associated with all the plain items, or it could be another example of "poor replacement product" again!
I'm assuming your bumper is equally spaced from each rear wing bottom, that the bumper ends are horizontal and that it is sitting back as far as possible without revealing a gap between bumper and panel, in which case you have options, 1. live with it, 2. dispense with the over-riders and fit alternate plate illumination 3. Move the filler neck. 4. Find some OE over-riders and check their dimensions against yours, if different buy a pair.
Allan Reeling

This photo dropped off for some reason, this shows the poor angle (at the time) of the bumper against the rear quarter.

As I have said I also feel that the spring bar mounting has been bent which may be having a further negative effect on the whole.

Looking at ones on line they show more angle on the over rider mounting end as opposed to the outer mounting. It may be easier for me to purchase a new set to ensure that everything is aligned in this area.

The over rider sin the 1st pic are as far as I know OE, I purchased new units that are not as snug a fit on the bar however seem to impact the filler cap in the same way.

If I was to modify the filler tube it appears that the ridge on the tube will prevent to much adjustment, can this be carefully ground away successfully??

The previous owner had 3 spacer washers on the left side and two on the right compensating for something!!!

Cheers,

C Brennan

As I said in my first post, the bumper irons, more often than not, need much bending and twisting and lots of trial and error fitting to get things lined up. I've spent hours doing this to get a decent fit. Don't expect new irons to be any better, they are often way out. The chassis bracket is a hefty forging and would need a heavy collision to deform it. Spacers/washers are often needed as well, as your previous owner found.
Allan Reeling

Mr Brennan
This filler cap difficulty is not unusual. My 67 MGB was a challenge to refill; my current 63 is also tight.
Firstly - you don't need to do anything with the filler neck unless the rear damage was so great that the hole is in completely the wrong place. Centre of my cap to the RH light frame mounting screw is 250mm, and 40mm down from the boot opening lip.

If you had major damage affecting the structural members that the cast bumper brackets bolt to, then these would be in the wrong place. But let's assume that the damage was confined to the bumper and the steel spring bar. My 2 spring bars were different shapes so I had to adjust them to be the same. Then there was a bit of trial fitting to get the bumper to the right angle and position. I packed the spring bar out from the body with washers to prevent a light shunt from causing paint damage. Ideally I needed to slot the holes in the spring bar to allow the assembly to sit a few mm lower, but as I had already zinc plated the spring bars, I didn't want to do any more cutting. There is a fair bit of rotation available with the components not tightened up, so I made sure there was cloth protecting the paintwork, and kept jiggling and tightening until it looked about right. Replace item 56 (Spacers) in the Moss catalogue if yours are bent.
In the photo you can see the clearance to the filler cap is only about 10mm - a bit of jiggling to get it off! If you have the later type of over-riders you might have a bit more jiggle room - its hard to tell in your photos.
Have patience! small changes to the spring bar will have a big effect.
John

John Minchin

Could they be front overriders? Although having said that I don't know if they would mount to the rear bumper. Those look pretty dumpy, whereas comparing front to rear in Clausager the rears do look slimmer. The rears should also have the holes to mount the number plate lights, which I can't see on yours. AFAIK the rear overriders always carried the number plate lights, except for 1974 non-North American models (Clausager) where they were on the bumper itself. You don't seem to have holes there either.

As I say there is a 3 1/4" gap between the top of mine and the rear panel, measuring straight back, what are yours?

The left-hand side looks a lot more 'pushed in' towards the body than the right, and your 2nd pic indicates the bumper is tipped back at the top.
Paul Hunt

My front over riders clear the radiator grille "mouth" (I have the recessed grille) with much less clearance than the rear ones do the rear panel. ie the gap with the back over riders is bigger allowing space to remove the fuel cap (similar to Paul's).
Michael Beswick

Paul,
You've been getting too much Solihull sun, or sundowners!!! Number plate lamps clearly visible!!
Allan Reeling

"Number plate lamps clearly visible!!"

Oh yes! I'd looked a couple of times even enlarging it, but by that time I was looking for the holes.
Paul Hunt

Thanks to all,

Will be having another shot at it next weekend and will advise results.

I really appreciate the efforts and advice from you all.

Regards,
C Brennan

This thread was discussed between 27/07/2014 and 30/07/2014

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