NOS Shimano SuperGlide (First Generation) Chainring Set...52x42 w/130mm BCD

Description

New-Old-Stock Shimano SuperGlide (First Generation) Chainring Set...52x42 w/130mm BCD
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Product Description:
This offering is for a new-old-stock Shimano SuperGlide (SG) chainring set. The set includes a 52T model, a 42T model (both of which have a bolt-circle diameter (BCD) of 130 mm) and a complete set of chainring bolts. The chainrings were made from an aluminum alloy and date back to the early 90's. Both chainrings have beveled teeth and the 52T model includes a chain guard pin to help prevent an overshifted chain from lodging itself between the backside of the crankarm and this chainring. Shimano made better quality chainrings during this era, but through shop catalog research we confirmed these are Shimano 105 equivalent rings...so still a good quality offering with a number of Shimano double crankset applications. Additionally, Shimano spec'd a number of their road triple cranksets with the same BCD measurement for the middle ring and outer (largest) ring, which provides other compatible options for this offering. Although, please do not consider these rings for a Shimano mountain bike triple cranksets, as they generally have a smaller BCD measurement.
Please note one of the close-up pictures to the left indicates the chainring is narrow chain compatible, but this can be misleading when considering today's market where current stock drivetrains include 9/10-speed cassettes. As discussed in more detail below, this reference indicates the narrower chain requirement of an early 90's 7-speed drivetrain relative to older 5/6-speed drivetrains. Most of today's narrower chains should still shift fine on these chainrings, but slightly wider chains (7/8-speed chains) would be preferred when matched on 7/8-speed drivetrains. We also understand Shimano was manufacturing Biopace (oval) models during this period, but this particular offering is for round chainrings with a satin silver finish.
From what we can tell, Shimano introduced the SuperGlide chainring in the early 90's. At a glance, the tooth design on these first generation SuperGlide chainrings appears fairly similar to older (pre-SuperGlide) Shimano chainrings. Both have beveled teeth to facilitate shifting, but the SuperGlide chainrings are the first to introduce slight variations in the shape of selected teeth (referred to as the tooth profile) at the two points of lowest pressure on the chainring (i.e., where the pedaling effort is generally at it's weakest state). These changes to the tooth profile are subtle, but we are able to notice slightly different shapes to some teeth in this low pressure area (and especially on the larger chainrings). More specifically, some teeth appear narrower (but still the same height), while other teeth look as if they have been "squashed" slightly, as they appear shorter and a little wider. Whatever the tooth profile changes, Shimano claims the computer aided design facilitates shifting on the front chainrings by limiting the "shift shock" (where the shift is sudden and dramatic) and chain throwing occurences. We are not entirely sure if these subtle tooth profile differences result in the significant shifting performance claimed by Shimano, but our guess is they probably offer some modest improvements over predecessor models with more uniform tooth profiles.
We have also noted the width of these rings appears slightly thinner at it's mounting points relative to predecessor models. Our best guess is this slightly thinner design is to bring the rings closer together (when mounted) to better accomodate the narrower chain required for a 7-speed cassette/drivetrain (relative to the older 5/6-speed drivetrains). Please understand, this observation is focused primarily on the entire ring design and not necessarily the teeth...as the teeth on this chainring are compatible with the relatively standard 1/2" x 3/32" chain. We also believe these chainrings may be used on any number of drivetrains (5, 6, 7, 8 and even 9-speed drivetrains) with a compatible chain...meaning a chain with an appropriate external width for the intended drivetrain. If we had to make a recommendation, we would probably lean towards a 7 or 8-speed drivetrain, but there is some flexibility here...as alluded to above.
With respect to condition, they are new and unused...and although bulk-packed...they are still in fairly nice condition (with no signs of wear on any of the teeth). The chainring bolts are also fairly nice. We have a box of them and although some show signs of use (with slightly rounded allen bolt openings, the chrome is still nice and the bolts are still functional).
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