A Little History…

The overrider fitted to the Healey 100, the MG TD& TF, and the Bugeye Sprite wound up being the same part number. Based on the information available, it was always believed that if you walked into a BMC parts department in 1970 and asked for one of each, you would have received three 27H9612 over riders. This seems odd because the Healey facebar has a relatively deep longitudinal groove, while the T Series and the Sprite face bar have smooth curved surfaces. The factory overriders never fit perfectly. The packing pieces, which fit on the edges of the overrider where it contacts the facebar, protect the facebar and help obscure the unavoidable gaps between the two parts.

 About the redesigned Overrider…

The originally produced the overrider with a captive nut welded to a plate that was in turn welded to the overrider. In production, the plate was difficult to position perfectly and the angle of the installed overrider depended on exactly where the captive nut was and the precise angle of the facebar. If the facebar was canted the least little bit, the overrider leaned either forward or backwards. It was a lot more noticeable with the overrider than the facebar. Because the nut was fixed in place, there was not a lot that could be done. A fixture that could be used in production to properly locate the captive nut, it was found that an overrider that fit a T-Series facebar just fine could not be fitted to a Sprite or a Healey. See photo of old style overrider Fig 1, with 1a, & 1b. 

Current Production Overrider

The newly retooled overriders and pressed from steel plate, and the edges are cleaned up by hand. The plates with the slot for the carriage bolt are pressed separately. The outer shell and the plates are assembled in a fixture that precisely locates the plate, and the two pieces are welded together. The overrider is chrome plated, and the back of the overrider is painted silver, which is how all bumpers and overriders were done by the factory. The correct bolts for the Healey would be 7/16 UNF (20 TPI), and there is no source at this time for these, and it is not certain that the bolts used on the Healey would be correct for the MG TD & TF or the Sprite. The overriders are therefore supplied with one somewhat generic 3/8” UNC (16 TPI) x 2” carriage bolt. If you are fitting these to the front facebar on a 100-4, the carriage bolt supplied may be too long and it may show behind the facebar. If so, it can be shortened.

About the Chrome Plating

Decorative chrome plating on automotive trim is often called nickel-chrome plating because nickel is always electroplated onto the object before the chrome. For maximum corrosion resistance, our overriders are nickel plated (0.005MM), then copper plated (0.025-0.030MM), after which they are polished. They then receive a layer of semi-bright nickel (0.015-0.018MM) then bright nickel (0.008-0.012MM). They are polished again, and finally chrome plated, after which they are polished once more. The nickel plating actually provides the smoothness, and most of the rust and corrosion resistance, which is greatly increased by the layering of two different nickel compounds. Contrary to what you may have heard, most of the reflectivity you see is due to the nickel. The chrome plating is exceptionally thin, measured in millionths of an inch rather than in thousandths. When you look at a decorative chromium plated surface like these overriders, most of what you are seeing is actually the effects of the nickel plating. The chrome adds a bluish cast, protects the nickel against tarnish, minimizes scratching, and symbiotically contributes to corrosion resistance. But the point is, without the brilliant nickel undercoating, you would not have the beautiful reflective surface we all call chrome.

Caring for Chrome

Clean all the chrome trim with soap and warm water only. DO NOT use harsh abrasives or polishing compounds to clean the chrome trim. Hard as it is, it is easy to scratch the chrome finish, leaving visible scratches and haze marks. After the chrome trim has been cleaned and dried, apply a coat of good-quality non-abrasive automotive wax. If you drive your vehicle in winter where the roads are treated for ice, or if you live near the coast, the chrome trim is exposed to salt and there is not much you can do about it except to clean and wax the chrome trim following any outing. Weekly maintenance in the face of such harsh conditions is the only way to properly protect and maintain your chrome trim.  Grant, M. “Supplemental Information on 454-010 or 27H9612 OVERRIDER, WITH BOLT AHY 100-4, MG TD, TF, BUGEYE SPRITE.” http://www.mossmotors.com/graphics/products/PDF/454-010.pdf, September 24, 2007, January 2015.