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MG MGB Technical - Gap between quarterlight/front window frame

Hello,

I am trial fitting my quarter lights after the bare shell of my 1976 mgb roadster has been repainted and the door skins have been replaced. I fitted the front window frame and the doors to see how the quarter lights would fit. Adjustment of the window frame holes in the body is now still relatively easy and will be difficult once the dashboard has been fitted.

The left hand door shows after some adjustment of the window frame, an even gap of 10mm with the quarter light frame. The door catch and lock haven't been fitted yet. If i fit the rubber seal between front window frame and quarter light, the door is pushed down a bit. Before the restauration, my quarter light frame was cracked so i welded it, polished it and fitted new seals. It is oke again.
i want to avoid that the quarter light frame cracks again so can anybody tell me if a gap of 10mm is oke
It also seems that the new rubber is 1mm thicker than the old one
Thanks in advance.
Regards
Peter van de Velde
Peter

Peter, I've just gone out and measured the gap in my rebuilt 72 roadster (original shell) and i believe that 10 mm is too tight. Not to worry though.

The main task is to get door alignment and gapping accurately set so that the waistline runs level and then the gaps between the front wing and door and the rear of the door and rear wing are approx 4mm, but in any event parallel and equal at the A post and B post.

Fit the rubbers, lock and strikers and adjust the doors for perfect closing. Only then should you fit the windscreen and I believe that you need 13/14 mm parallel gap between the front on the quarterlight and the bare screen frame. If you cannot get this then adjust the screen and also file the slots in the tops of the doors to allow the quarterlights slide rearwards. Adjust the parallelism of the gap in the screen angle and also by packing the quarterlight mounts on the front face of the leg and also by fitting slotted washers under the top of door mounts if desired. This will also be held by the bottom brackets.

Now that's not all because you will have to fit the dropglass and ensure that it operates properly and that the rear slide has adequate adjustment to allow it to fit correctly.

All in all this can be a most frustrating job that is linked to so many things but door adjustment does NOT come into it as this is determined by panel fit and gapping.
Iain MacKintosh

Hello Ian,

Thanks for your reaction. My door alignment and gaps are near perfect and even. It took an imense amount of work while fitting new door skins but it was worth it. So i don't have any problems there. The 13 or 14 mm you mention is a lot. I checked an unrestored roadster yesterday evening and this showed a not quit even gap which at the bottom was 7mm and at the top 10mm. The 7 mm was clearly too tight while the rubber was damaged there.
Regards
Peter
Peter

Peter, you have already outlined the problem in your first post in that if the gap is too small the windscreen will push the door down. This leads to what we know as the "crack of doom" which is a crack which starts under the quarterlight and moves down the face of the door. If I am 100% honest then the gap on my own roadster is slightly tapered on the drivers side going from 10mm at the bottom to 14 mm at the top. The 10mm gap is definitely too tight and squashes the seal a bit so you should do everything you can to get a bit more space here before you continue. It's always easy when you have too much space but if you haven't got enough then its a real problem. It's great that you have the doors well aligned but don't loose this now under any circumstances although you will have to lift the tail end slightly after you fit them all up as the weight of all the fittings and trim will make the rear edge drop about 3mm
Iain MacKintosh

Hello Ian,

I know what you mean with the "crack of doom". This was one of the reasons to replace the door skin because the old skin was cracked there. I welded a small sheet of steel under the new skin to avoid cracks.
I will now as you mentioned, fit the door glass but i compared dimensions with the other roadster and the door is about 6mm shorter than on the unrestored roadster so i believe i don't have much room to slide the quarterlights backwards. After fitting the new door skin, i trial fitted the quarter lights but not the sliding window. Although the door is shorter on the car i am restoring, i don't believe the shell sacked because the line where the chrome strips has to be fitted on front fender, door and rear fender is very straight. I replaced the sills. These were only rusted near the front and rear fender and i fitted a thick pipe between front door hinge and the door lock to avoid the shell to sack. After replacing the sills, i renewed the door skins.

I also checked the rubber between quarter lights-front window frame and without pressing, its 15-16mmm thick so now i am convinced, i will need the 13-14mm you mentioned before. It looks like i will need to slide the front window frame 3-4mm formard.
As you say, its a lot of fiddlng but i want to do the right way to avoid cracks in the quarter light or door skin.
I will keep you informed but it make take some time because time to work on is limited in the coming weeks.
Regards
Peter
Peter

Ah the fun of MGs. No two are alike or indeed the same size. It is fairly well known that the B is about 6mm longer on one side than it is on the other but I can't remember which is longest. I see that you fitted the sills with the old doors and skins still in position so you have reassurance that nothing has moved. New skins can also vary but yours seem to match up OK so i wouldn't worry. There really is not much room available to slide the glass rearward and I seem to remember mine being very close. It's not unknown to have to move the screen frame a bit forward as well and you might have to file the slots in the wing. I seem to remember having to do this on one side. Don't worry about the two sides being differently gapped or nangled as the screen frame is easily capable of being twisted this small amount over its width to allow for this. One bonus you seem to have is that your car isn't yet painted ??
Iain MacKintosh

Hello Ian,

The 6mm difference is not between left and right hand but compared with the door of another MGB.
The skins didn't fit very well. These were to long and too high (which of course is better than being too short).
My car is already painted so i basically have a bare painted shell. But making alternations to the holes in the shell for the frame window shouldn't affect that.
Regards
Peter
Peter

Yes Peter I realise that you were making a comparison with another MG but I'm merely pointing out that both sides of the same car may be different lengths !!

Mine was painted at that stage too and there was no real difficulty enlarging holes and slots./
Iain MacKintosh

Peter
The gap at the bottom of my quarterlight is narrower
than the top. I recently had a new windscreen fitted
and had to go back to the windscreen fitters twice.
A 13mm or so gap may be ideal, but very difficult to acheive in practise.

Most MGB's probably never had even gaps from new. Even today, If you look at several other MGBs I do not think you will find many with an even gap all the way down the quarterlight, so be prepared to comprimise!

I think you have a far greater chance of an even gap if you fit the windsceen before the dashboard.
Robert.
R J Collier

I admitted to not having an even gap and it might be difficult to achieve. I did say that my minimum gap was 10mm at the bottom and that cannot be compromised on or you just wont have enough space. On a car body you should always aim to have at least enough length as you build up because if you don't get this in the early stages you will never get it back.
Iain MacKintosh

Ian, Robert,

This weekend i achieved a more or less even gap of 12-13mm on the left hand door. I had to file the slot holes in the door and with my Dremel i widened the wind screen fitting holes in the body. Its time consuming. The rubber now fits well.
Now see what surprises the right hand door brings.

Robert, i agree with you that most roadsters don't have an even gap. As you mention ,one has to adjust the gap when the dash isn't fitted, otherwise acces to the windscreen fitting in the body is limited.
Regards
Peter
Peter

Well done Peter that's just great and you can be well pleased. Now keep your fingers crossed that the other side works out as well
Iain MacKintosh

With the windscreen frame seal in place it should only just touch the front face of the 1/4-light frame all the way up. When under way wind pressure will tend to tighten it up a bit more. What is just as important is the gap between the *side* of the 1/4-light frame and the narrow thin lip of the windscreen frame seal, and there should be an even *clearance* all the way up of about 1/8" to 3/16". Insufficient clearance hear is one of the main causes of the crack of doom from scuttle-shake. The other main cause is a design weakness in the door skin itself.
Paul Hunt 2

Hello Paul,

i see what you mean. I got this gap even. I will measure it. This gap was easier to adjust.

By the way, i am also working on the wiring loom and will follow a lot of your good advices on your site. Will install the relais and fuses and the earth connections to the body near the fans.
Ordered special coloured wires, terminals, fuseholders ect.
Its been a great help a lot useful information.
Thanks again.

Peter
peter

I have fitted the other door and quarter light.
The gap at the bottom is 10mm and at the top its 12mm.
It looks as if there is enough space to slide the quarter light a litte away from the front window frame. I hope the quarter light rotates a little so the gap will be even.

I also looked at the gap Paul mentioned and it is within the range of 1/8 to 3/16. It seems this job is finalised this weekend.
Regards
Peter
Peter

There is always a little wriggle-room in quarter-light mounting, although the main adjustment is sideways on the bottom bolt of the long channel to match the angle of the screen, rather than fore and aft movement or tilting. Having said that packing between the bottom of the 1/4-light and top of the door skin, either at the rear or front, will give you some tilt.
Paul Hunt 2

Now have the right gaps. As usual things didn't go as quick as expected. I couldn't get the 2 special bolts fitted behind the plastic caps in the front. Had to position the quarterlight 2mmm more outside and had to grind the upper hole where the plastic gap sits in the door a little bigger. I painted the grinded edges and have to wait for the paint to harden.
Then i can finalize this door.
Regards
Peter
Peter

This all sounds familiar Peter but you seem to have got to grips with the situation now. Regarding the two bolts under the plastic caps you will have to fit packing washers between the quarter light frame and the door otherwise when you tighten the bolts the short leg of the frame may be pulled forward out of line. Just wait till you see where you have to put your hands to get these packers in place !!!
Iain MacKintosh

This thread was discussed between 01/02/2006 and 13/02/2006

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