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MG Midget and Sprite Technical - 1500 Bentley Manual?

Was there ever a Bentley manual for the 1500?
Does someone have it, or a BL shop manual or something like that, who could look up for me the free height, fitted length and wire diameter of the original springs fitted to the front suspension of a '75 ~ '79?

I am just curious about the 1500 for comparison, as I was looking at the other springs used in our cars since the beginning and found that the wire diameter was decreased when the spring was lengthened in '73.

First, I hadn't realized it was lengthened before '75. Even though the amount wasn't by much (+0.26"), I guess it was done to compensate for added mass of body reinforcing added at that time. But having reduced the wire diameter, it would have softened the ride too I guess.


free length wire diameter Model
9.4" 3.625" 948cc
9.59 3.625 1098 & 1275 through '72
9.85 3.575 1275 ('73 & '74)

The Bentley states that the fitted length of all years until the '75 change was 7.08". It also defines the spring rate of the first two as 271lb/in, but doesn't mention what the final one's spring rate was.

What it looks like to me is that if someone with a '73 or '74 wanted to drop their ride height a small amount, and stiffen their ride a little bit, they could fit bugeye springs and get about a 1/4" (0.45 shorter spring x 0.5 ratio), and some small increase in spring rate. Not much, I know, but a cheap option compared with aftermarket springs.

Knowing the 1500 information wouldn't change any of this, of course, but it could, I think, provide a useful contrast to help grasp what these small differences would make in a car.



Norm "curious" Kerr
Norm Kerr

from workshop manual for uk 1500


mark (1977 1500 Midget) Preston Lancs

WOW, the 1500 used the same front spring as the late 1275 did.



At first that blew my mind, but now I see what I was confusing:


duh, the coil diameter is not wire diameter of course. So, they didn't ever change the spring rate at any time, only the free length.

The other thing I was confusing myself about was that the front suspension was not raised 1" at the 1500 by increasing the coil spring length, it must have been raised by changing something in the mounting points. It was only the rear spring that was raised 1".


So, for all years of production, from '58 ~ '79, the spring rate, coil diameter, fitted length and # of effective coils for the front spring stayed the same.
Only the free length of the spring was increased, and that, only at two times when the body got heavier (once at the "bug-eye to fenders & bonnet", and then at "FMVSS impact reinforcement adoption" in '73). Neither of them was when the 1500 was introduced!

Now I more fully understand when they say the 1500 can not be easily lowered down that 1" (basically, 2" shorter springs = that much less travel, I guess).

Norm "older, wiser" Kerr
Norm Kerr

2" shorter springs?
Dave O'Neill 2

yeah, you know, if you wanted to drop a 1500 down to the ride height of a 1275, you'd have to lower it 1", and the 2:1 ratio of the suspension would make that need to be a 2" shorter spring.

Oh, but now that I think about it, the fenders got longer too, didn't they? Ok, good point. No need to lower. If someone removed the heavy bumpers, they'd have some height to get rid of, but that wouldn't be the full 1" then, would it?

I should stop trying to think about what someone would do with a 1500, because I only am familiar with the 1275 models. Thinking too much will make me say silly things.


Norm "all done now" Kerr
Norm Kerr

Norm,

I lowered my 1500 recently and the springs ARE different.

The 1500 springs (at least on my 1979) have a free length of 10.5 inches.

I substituted 1275 springs (I think from a 1969) that had a free length of 9.625 inches.

This lowered the front end about 1.25 inches.

I didn't change the rear leaves.

I didn't like the way it looked or handled and put the original springs back in and added 1/2 inch spaces (actually nuts) to the lower spring pans that resulted in lowering the front end one inch. I'm happy now, but still would like to lower the back a bit.

BTW, I have some springs from a MkII 1966 midget that are 9.5 inches.

Lee

Lee Fox

This thread was discussed between 03/07/2010 and 04/07/2010

MG Midget and Sprite Technical index

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