MG TC Wobbly Pedals

Paul Ireland has come up with an improved design over the original Factory arrangement.

When I bought my TC in 1967 it looked as if the pedal bearings had not been lubricated since the car had left the factory. The clutch pedal had seized onto the shaft and a very rusty shaft had been rotating in the pedal box and worn both and the central and outer supports! I have been running for the past 46 years with a bodge shim and wobbly peddles! At the time I also drilled and tapped the pedals and fitted grease nipples. This worked fine, but meant you had to crawl under the car to grease them. 46 years later this is becoming more difficult. This year I decided it was time to fix the problem by fitting an oversized and cross drilled shaft so I could grease the bearings from the outside of the car.

The pedal box is basically a U shaped fitting with two 5/8” holes to mount the pedal shaft. It is fitted onto the chassis with three bolts and one rivet (I do not know why the factory fitted one rivet) which means it is very difficult to remove. There is a larger diameter hole through both the outer and box sections in the chassis. There are a number of problems with this arrangement:

• There is no means to lubricate the pedals.
• Shaft can rotate in the pedal box and wear the pedal box (as mine did).
• There is no means of preventing end float in the shaft; it is only located by the two spring washers.
• Spring washers allow dirt and water to enter the ends of the pedal bearings.
• Clutch end of the shaft is unsupported at one end placing a high load on the outer (chassis end) pedal box support.
• It is not possible to provide for a grease nipple as the outer split pin prevents drilling an end feed.

My replacement shaft attempts to address some of these issues.

The boss on the outside serves to provide an end location for the shaft and removes the need for the inner split pin. The outer part of the shaft is +2 thou to create an interference fit with the outside of the pedal box to prevent the shaft from rotating. This arrangement has allowed a central feed hole from a grease nipple at the end of the shaft to cross drillings inside the pedal bushes. This permits the pedals to be greased from the outside of the chassis. In addition I have added 4 phosphor bronze thrust washers both to “seal” the faces of the sides of the pedals to deter water and dirt ingress and provide a bearing surface.

The new shaft was made from 18mm stainless bar and I increased the diameter of the pedal shaft by 55 thou (from 625 to 680 thou) to allow for the wear in the outer side of the pedal box. To maintain the thickness of the bushes in the pedals, I also reamed the pedals to increase the diameter of the hole in them by a similar amount. The new oversized bushes and thrust washers were turned from phosphor bronze.

The thrust washers were made after the central hole had been bored to fit the new shaft by facing the bar and using a parting tool to slice off each washer, repeated 4 times. The inner washers are 60 thou thick and the outer 75 thou. Each washer has 4 filed radial groves on one face, deeper on the inner edge tapering to nothing on the outer to allow grease to flow between the pedal and washer. They are a close fit on the shaft to force grease between the pedal and washer rather than allowing it to flow between the washer and shaft.

The accuracy of the cross drilling is not critical as long as the two grease feed holes meet the central feed. At the brake pedal side, the plain and thrust washer thicknesses should be chosen to ensure there is adequate compression of the spring washer.

The distance of the split pin hole from the end of the shaft depends on the thickness of the plain and thrust washers and again should be positioned to ensure the spring washer is adequately compressed. The split pin hole is at 90o to the grease feed holes to ensure the bearing face under load is properly lubricated when the split pin is installed vertically.

Warning: Do not forget to fit the fume excluder over the pedals before fitting into the car.

While care is needed not to “over ream” the chassis or bushes, the whole assembly can be easily manufactured using a metal lathe.

The 250mm x 18 mm stainless round bar and 1”OD x 1⁄2” ID hollow Bronze tube were bought from www.metals4u.co.uk The 21/32” – 23/32” adjustable hand reamer for the bushes and chassis box and 23/32” – 25/32” adjustable hand reamer from www.totoolsupplies.co.uk The reamers were reasonably cheap and their quality adequate.

I now have two free moving pedals that no longer wobble and are much easier to grease.

Paul Ireland
April 2014

Ed’s note: Drawings of the old and new layouts follow along with photographs of the parts used, the shaft, the location of the grease nipple and the completed job.