At 09:35 AM 6/14/2007 +0100, Dave Shattock wrote:
"The springs I got from a supplier in the midwest USA were terrible. They flexed in such away that the rear axle was shifting terribly. They were in the car for 50 miles and we pulled them out. We've had a set of originals re-arched. Apparently most replacements available in the USA aren't worth using. Does anyone have more up-to-date info?"

For some years, spanning minimally from the mid 90's until as recently as a few years ago, North American source leaf springs for the MGA were notorious for being too tall and would never settle down to the right height. I had seen the same problem as far back as 1989. I installed a set of these in 1997, but put up with them for only a short time before returning to the original ones (reconditioned).

When the leaf springs are too tall the rebound strap will become taught with only moderate body roll during cornering, lifting the inside rear wheel off the pavement. When that happens you get half the weight of the car on one rear tire. This overloads the tire, reducing grip efficiency. Result is that the tail end swings wide with a wild oversteer condition. The faster you go the worse it gets, but it can happen at relatively moderate speed such as 45 mph on an expressway exit ramp. Very scary, and unsafe, not to mention taking a lot of fun out of brisk driving and losing the competitive edge.

I am not sure if the problem persists today, but would appreciate any recent user report.

Okay, in early 2009 I am still getting lots of reports of new leaf springs being too tall, and so far no known source for correct height springs (off the shelf). My best solution to this problem is to take your old springs to a professional spring shop for reconditioning. They can make a new leaf to replace a broken one, and they can re-arch springs to any desired ride height. New springs might be cheaper (or maybe not), but if you have to get the new springs re-arched then the combined cost of purchase and rework will likely exceed the cost of rebuilding the old ones. See RS-105 for correct leaf spring specifications.

Addendum June 8, 2016:
After 58 years my original leaf springs have finally collapsed. I suppose removing one leaf for competition work 20 years earlier was likely a contributing factor in their demise. So I had to install new, current issue leaf springs. There is apparently only one manufacturing source for these parts, so they will be the same no matter where you buy them. Free height of the new springs is 1/2-inch too high. Also the spring rate of the new springs is 175-lb/in where original springs were 150-lb/in (thicker leaves), so the new ones deflect about 1/2-inch less under load. This combines to give ride height 1-inch too high, which makes it near impossible to install the rebound straps and really screws up handling characteristics.

For information (photos and notes) on the installation, measurement of free height and spring rate, see our travel log for June 8, 2016.

For a few years now we have been touring with a fully laden car plus a 17-lb trailer hitch and a trailer with maybe 40-pound tongue load (think always two heavy guys plus the equivalent of 150-pounds in the boot). Hoping this will depress the rear ride height enough to keep the screwed up handling from getting too far out of hand. End result is the rear end is a little more bouncy, and the steering is a little bit twitchy as it does oversteer slightly. I do not recommend use of these new springs without some corrective work, but we are learning to live with it for touring (no competition work anticipated).

Addendum December 5, 2023:
On Nov 20, 2023, Donald Rosie in Edinburgh, Scotland, UK wrote:
"MGOC ... tell me awaiting new batch of rear spring coming soon, 'Build to original spec'. ... So guess who will be the next guinea pig.

On Dec 4, 2023, Donald Rosie wrote:
"I have received rear springs from MGOC. Tthey measure
40 7/8-in eye to eye centre,
6 3/4 and 6 7/8" high,
and the leaves are 3/16 thick. (That's the best I could come up with my ruler)".

So I asked. "Don, -- Could you try measuring the leaf thickness again? Original leaf thickness was 7/32-in. Replacements from British Motor Heritage are 1/4" thick, making them to tall and way too stiff. Spring rate varies as the square of the leaf thickness. Reducing thickness from 7/32 to 3/16 would reduce the spring strength and rate by 25%, which would be a huge change".

On Dec 5, 2023, Donald Rosie wrote:
"Pictures attached, what do you think"?


Bingo. Both of those pictures show 7-layers = 1-17/32" stack height. Divide by 7 and you get exactly 7/32" per leaf. Spot on. Three cheers for MGOC.