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MG Midget and Sprite Technical - looking for kingpin/bushing changing instructions

Hi All,

I have new kingpins with new bushings to install. However, I can't seem to find any data on the size reamer that is needed (Moss no longer sells it and the manual does not say what size it is). Also, what are the measurements that need to be made to determine the proper fit.

I am sure that I am not the first person who has asked this group how to change kingpins. I am pretty handy but for this I am willing to seek professional help. However they are going to ask me what the clearance is and what size reamer is needed.

thanks for any info.

R Harvey

Rebecca, I don't have the dimensions but there are two different sizes on the king pin and the reamer is a special tool that reams both bushings at the same time to ensure alignment. The tool was expensive when it was available but some MG clubs here bought them and loaned them out to their members. Perhaps one of those is still available. Most folks now just buy the rebuilt swivel axle assemblies that are already reamed to size. You can get the size needed by simply measuring the two bushing areas on the king pin with a micrometer and add a couple of thousandths for clearance. Most machine shops should be able to ream out the bushings once pressed into place, but may not be able to ensure alignment. Check around if you can't find the reaming tool.
B Young

Rebecca. You need a piloted bushing driver (must be custom made) to drive out the old bushings and insert the new bushings.

The bushing driver (one for the top and one for the bottom) are used with a hydraulic press to press out the old bushings.

Then, the stub axles are cleaned, should be crack inspected, painted, and the press and bushing drivers are used to install the new bushings. The center holes of the bushings will be undersized.

A special, piloted reamer is used to ream the bushings, ensuring that they are perfectly in line with each other.

It is possible to bodge any part of this process, but, the finished product will never be as good as it could be done correctly.

Bob and Gil Schaulin have the correct reamer and the bushing drivers to properly do the job. They are located in Arizona and operate a wrecking yard specializing in MGs. If you are not able to find someone with the proper tooling closer to you, you might give them a call at 602-415-1846. Their prices are reasonable and USPS flat rate shipping provides both quick and inexpensive service.

Les Bengtson

I think David Lieb once said that Chicagoland MG Club had a reamer. If you know anyone in the Windy City maybe they could help.
Altenativly, there are several shops in MA and at least one in CT. that specialize in MG restorations.
HTH Phil
Phil Burke

Rebecca, I know that you are building a quick autocross car. I have recently completed a couple of mods to my midget that you might be interested in, the installation of a home built pedal box that uses a bias bar for the brakes and an Accusump system to protect the engine from dry starts and loss of oil pressure in hard cornering. I'll be happy to share details and photos with you if you are interested (same goes for anyone else for that matter) just drop me a line at bkyoungatkcdotrrdotcom and I'll be happy to send you the information.
B Young

Rebecca - which model do you have? The kingpins are of different diameters on the early and late cars.

I took my Frogeye axles to my local machine shop, and they happily pushed out the existing bushes, pressed in the new (which I supplied), and reamed them - having both early and late reamers on the shelf. But perhaps these shops are becoming rarer - particularly on your side of the water.

After that, the rest - as they say - is easy.

Over here, we are told awful tales of very bad rebuilds that don't last more than a year, so I reckon it's good to see the whole process for yourself rather than accept a complete, all-closed-up exchange assembly.

I bought reconditioned winners circle swivel axels (the ones that have the axel part replaced with better 4030 steel so that it won't crack after racing it). The new kingpins that I bought (with the major suspension kit from them) are not installed. They don't offer that service. so I am not removing pld kingpins, I am only installing them.

If I had the specification for what the clearances are supposed to be, then I am pretty sure that a local machine shop can do the job with the tools that they have. What are the clearances supposed to be?

I have a 1973 car. When I ordered the new ones I don't remember being told that they sold different ones for different years (but they know what I am sending them as exchange). Perhaps I should call back and ask them these questions.
R Harvey

i hope someone will correct me if I am wrong, but I think the only difference between early stub axles and late is the early ones were for drum braked cars. I have been told that all disc braked cars are the same (subject to verification)
Chris Edwards

IIRC the drum brake stub axles have a smaller lower journal diameter on the kingpin than the later disc brake ones so are not interchangeable although I have heard the odd tale of the early one being accidentally fitted then quickly replaced after a short drive and realising the error.
David Billington

Drum brake cars have smaller swivel pins, but all disc brake are the same.
Clearance on all the bushes should be .001./.002. AKA "free without shake".
Any competent machine shop can install and ream the bushes in line with normal shop equipment. The stepped reamer was for shops that did a lot and/or did not have or were not competent to use standard tools. Even better than reamers is use of a Sunnen hone, better fit for longer time.
Be sure the bushes are pressed in correctly. Top is flush with top of axle, bottom is flush with counterbore in bottom of axle.
WC not doing this while selling all the parts is unfathomable!

FR Millmore

Rebecca I can do this for you. Peter
Peter Caldwell

Thanks peter. I will send them to you.
R Harvey

This thread was discussed between 01/03/2011 and 04/03/2011

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