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MG MGB Technical - Ground Clearance

I am having ground clearance issues with my 72B.

I suspect my exhaust system (who knows what it is from, but the muffler looks like something from a farmsall) is too close to the ground, especially the exhaust clamps.

I will also offer that I am in tht 250+ range myself, but I hit the exhaust pipe at mid-car yesterday simply driving over one of the raised (1-1 1/2") manhole covers at the gas station where they fill the underground tanks.

I really have to be careful driving out of slanted driveways, etc.

Is there a measurement for how much ground clearance my car should have empty, vs. someone my size being in the car?

Empty the car looks to have 2-3" from ground to exhaust clamps. I'm thinking I may have to go to exhaust shop and have them weld all the connections to eliminate the clamps. (Yes, I've already rotated the clamps 90 degrees so the bolts are at 3 o'clock instead of 6 o'clock.)

Is it time to install an extended shackle, or another leaf on the spring or ???

Thanks for assistance.
R.W Anderson

MGB handbook states ground clearance as 5 inches minimum. Something seems seriously not right in your car. It may be the exhaust components/fitting. It may be springs sagging. I've not measured mine but but the 5 inches is probably pretty close, though I wonder about the rear axle shackle ends.

That aside, most of us have learnt to angle over road/parking bay humps.
Regards
Roger
Roger T

Is the whole car too low, or is it the exhaust just sagging?

Liam
Liam H

Too me the whole car looks equally low & level. The exhaust is not sagging, it is tight and high. In fact one point hits a bolt coming out of the bottom of the car. I had to put in a sideways hanger to pull it away. The dang clamps get in the way, as does the muffler.

I'll check this weekend to see if I have 5" of clearance anywhere. but I rather doubt it. Hitting a 1-1/2" obstruction was a bit of a surprise.
R.W Anderson

Bear in mind that the factory only allowed for 150lb per person. But even though self and navigator come just within that, fully loaded with tools let alone luggage when touring the exhaust was constantly grounding if not the suspension bottoming over humps and bumps and the longditudinal raised section of narrow lanes. First I replaced the springs thinking they were worn out seeing as they were nearly flat, but that made no difference, the new ones were virtually the same (that is how they are supposed to be). Next I fitted RB roadster springs to a CB roadster, which did increase the clearance but at the expense of handling and comfort over certain surfaces. Eventually I extended the rear shackles by about 1.25", refitted the proper springs, and not bottoming and grounding is a thing of the past.

However from what most people say these days just replace the springs and you will end up with the car sitting like a submissive monkey i.e. the rear way up in the air, so much so that some have to weight the boot/trunk in order to get the springs and rebound straps installed. I'm convinced this is because manufacturers are (over) compensating for the, erm, greater weight of modern occupants.

Also check the distance between the top of the exhaust pipe and the bottom of the fixed rear cross-member. This should have a recess to accomodate movement of the exhaust up and down without hitting the body. If there is more than 3/4" clearance then your exhaust is probably too low.
Paul Hunt 2

The exhaust was originally hung to the car nice and tight and then welded up in one piece at the factory. If you took it back to Morris Garages for a new silencer in the 60s they would do this in the workshop locally, the reason for this is that they have always had a ground clearance issue although they qualify as off roaders in comparison to AH3000s!
Stan Best

Is yours a two muffler car?
When I put in a new exhaust (wide bore for the V8) I got them to put the first muffler just prior to the back axle, and of course, the second muffler after the back axle, in the usual place.
The low point is the middle, furthurst away from the wheels.
The first muffler is a short one.
I've also made sure the whole system is as high as it can go without vibrating against the body of the car.
Peter

I had the same issue and I don't now:

1) The center muffler is not required. Cut it out and put a straight tube in. It increases power and the noise is a low pitch - sounds good
2) the leaf springs in the back are likely sagging if they are original. I replaced them in about 4 hours. It raised the car by 4 or 5 inches (a lot) - Better handling too
Frank Baker

I had exactly the same problem with my ´63. Solved it by using GT springs at the rear, and replacing the huge center muffler with the small type often referred to as a "bomb" muffler. Pure routine for my local exhaust shop - they had done this to a number of MGBs.

In addition to better ground clearance, the car now sounds much better. Even if it is louder, I find the deeper exhaust note is more comfortable, particularly when driving with the top up.

Tore
Tore

RW - you touch on a topic I raised a month or so ago, except I referred to it as the "ride height" of my 73BGT being too low. Many respondents helped with suggestions, and from memory a measurement of about 14.5 inches from centre of wheelrim to underside of chrome strip, was popular. I wonder whether you should measure your B at each side to see how it stacks up? It might help you to judge just how low it is,compared to some sort of "norm". Good luck. John.
John Hall

To provide some interim answers to the above, I will clarify that I have an obvious after market exhaust system.

I have the original exhaust header, and what I perceive to be the original design exhaust pipe coming down by back of engine/front of transmission.

The EXH pipe is connected to a pipe that is clamped to another pipe just below drivers seat, this pipe extends back to muffler (8" dia x 18" L apx) just in front of rear bumper.

So I have a "one muffler" no convertor-no resonator system - that occassionally vibrates against a bolt sticking below floor and repeatedly hits speed bumps and other low obstacles.

I will measure things this weekend, with me in and out of car and/or find another B to compare to.

R.W Anderson

Okay I've measured ground clearance a bit.

Distance from center wheel hub to ground - 11" at all 4 wheels.

Distance from center wheel hub to lower edge of fender - 11" at rear & 13" at front.

Distance at lowest point of exhaust (below driver's seat - 3 5/8" from ground to bottom of pipe. Clamps hang 3/4 - 1" below that and are at 90 degrees so clamp points sideways not down.

Rear Springs are 6 leaf.

Does any of the above set off an alarm? This was without anyone in car.
R.W Anderson

Way low at rear = springs

A bit low at front = bad lower control arm inner bushes, possible bad outer lower A arm/KP bush/bolts

The correct fitting of exhaust has the pipe centered in the crossmember notch below the seat, with about 1/4-3/8" clearance all the way round.
The correct hanger at the rear bulkhead exactly locates the pipe where it should be, and NO other hanger I've ever seen will do so.
If the pipe is correct, there is no bolt anywhere that will hit it. So, either the pipe is wrong, the bolt is wrong, or more likely all both of these.
Find some different clamps or weld the system.
It is almost always necessary with the crap parts today to have to heat and bend pipes to get them right; they used to go on much easier!

FRM
FR Millmore

The normal point of ride-height measurement is from the centre of the axle to the bottom of the trim strip. This eliminates any variables from wheels and tyres when trying to determine if the springs are OK or not, and also gives a front to rear comparison. Hopwever it is dependant on the accuracy of any wing replacement that might have been done.

There are over 30 ride heights from around the world at http://www.mgb-stuff.org.uk/wn_suspensionframe.htm and click on 'Ride Height' if you want to compare. 13" is low (especially unladen), it is typically around 14" to 14.5", but should give great cornering :o) Squint under the car along the springs. They should be almost flat, almost no upwards bow left, and the rear hangers should be almost vertical. If your springs are reverse bowed they are knackered.
Paul Hunt 2

I see that the reference point for Ride Height is not from the center of the hub to the bottom of the fender well (as I measured), but from the center of the hub to the chrome strip that runs fore to aft just above the door keyway.

So my 13" Front & 11" Rear measurements require an additional 2-3" being added to them. I double check this tonight. This won't change my front dimension at all as strip is right at fender well edge, but it should change my rear from 11" to 13"+ - which appears to be closer to spec.

I did have an exhaust shop remove my two clamps going to two hangars on Friday and simply weld the hangars to the pipes. All my connections are welded, not clamps. All clamps had grinding marks on them.

I've enclosed a photo of my car. In comparing my car to some other car photos it looks like others have almost full tire clearance in fender well. The top of my rear tire is still partially inside the fender.

I also have a photo with 2 people in car to show laden situation if needed.

Thanks for everyone's help and I've printed out the Steering & Suspension discussion mentioned above by Mr. Hunt.



R.W Anderson

Your rear looks about mid-way between what mine was before and after I extended the hangers, i.e. around normal. If I jack under the axle it's a bit marginal as to whether I can get the centre-lock wheel off the hub i.e. the top of the tyre still fouls the bottom of the arch. Before I extended the hangers I stood no chance and had to jack under the front hanger.

Remember that many who will have had occasion to photograph the rear suspension will have rplaced the rear springs, and many of these today are way too hard or arched, giving a rear-high stance, sometimes to the point of not bein able to fasten the rebound straps without a couple of heavyweights sitting in the boot. The Workshop Manual dimesional drawing of the body clearly shows the rear tyres up inside the arches, photo attached. While the drawing probably isn't accurate enough to take detailed measurements from, it must be representative. I've spent some time looking for original brochure pictures on the web and whilst there are very few showing the rear arch straight on th couple that I've found do seem to show roadsters with the top of the tyre just tucked inside and GTs with it just about level.

Paul Hunt 2

This thread was discussed between 15/06/2007 and 26/06/2007

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