GB 531
Main Photo
Category:  Stems
Name:  GB 531
Brand:  GB
Years:  Early 1950's - Mid 1960's
Country:  England
Added By: daveross on 01/31/08
Updated By: peterbman on 05/19/19
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GB 531GB 531
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MaterialSteelMarkingsscript "G.B." over "KROMO" or "531"
Bar Clamp Size 1"; 25.4Quill Size 22.2
Expander Style ConicalExpander Bolt Size
Binder Bolt Size   
General Information
GB steel Spearpoint stems came in many sizes and two materials choices - Accles & Pollock ‘KROMO’ steel or Reynolds 531, both chrome plated. As its name implies, the A&P KROMO is made from a chrome-molybdenum steel alloy and the R531 is, of course, Reynolds classic manganese–molybdenum, medium-carbon steel. All sizes were (at one point) offered in both materials. There was no price difference between the two steels. The two examples pictured are on the longer side, 4½" and 53/8". Initially (c.mid-1950’s) it appears that only KROMO stems were available and in shorter lengths (23/8", 3” & 35/8"). By the early 60s, both steels were offered in a wide range of extension lengths - 23/8", 3”, 35/8", 4”, 4¼”, 4½", 5”, 53/8" & 5¾”. However, by 1966, the surviving catalogues again only show KROMO available with only 23/8", 3”, 35/8", 4”, 4½" & 5” sizes listed. Steel stems are not shown in any later catalogues and it seems that the very similar design alloy (‘Hiduminium’) stem had become more popular and high quality steel stems were no longer much in vogue (except perhaps amongst some track riders and especially since the alloy spearpoint never seems to have been offered with an extension longer than 4"). All the steel stems seem to have shared a common 6¼" quill length, although there is no info for the stems longer than 5", so these might have had longer quills.
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