Faffing and fas­ten­ers

A flurry of ac­tiv­ity has the Yamaha TDR ready to em­brace the ar­rival of sum­mer weather, though Mike’s in tur­moil over ten­sions…

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Sched­ul­ing my Yamaha’s MOT, tax and in­sur­ance for the same time gets it all con­ve­niently sorted in one hit. It also presents am­ple faffing op­por­tu­nity. This is es­pe­cially true when the DVLA web­site throws a wob­bly, the in­sur­ance firm award them­selves a 40% bonus over last year’s pre­mium, and the twostroke’s in­di­ca­tors ob­sti­nately refuse to flash.

How­ever, de­spite ready­ing my­self for te­dious dither­ing and has­sle, ev­ery­thing slots into place with un­ex­pected ease. The DVLA’S site won’t re­new the tax as it doesn’t recog­nise the TDR, how­ever the nice lady in the lo­cal Post Of­fice mer­rily sorts it us­ing the re­newal no­tice. A quick call to the in­sur­ers with a made-up quote from an­other firm se­cures cover for the same price as last year. And, notic­ing the winkers flicker when the mo­tor’s revved, the penny drops that the bat­tery’s flat­tened over win­ter. Charged and good as new, the Yam zips to clas­sic-friendly TK Mo­tor­cy­cles (01664 560466) and whis­tles through its MOT.

All is now well with my world... apart from a sub­con­scious con­cern over bolts. My bike had TZR wheels when I bought it, with longer stain­less-steel bolts and spac­ers used to line the brake calipers up with the discs. I like the look of a stain­less cap­head, so used four of orig­i­nal length when re­fit­ting the stan­dard wheels. How­ever, glimps­ing the num­bers stamped on the heads has me ques­tion­ing what I’ve used.

Fine aes­thet­ics aside, the ad­van­tage of stain­less is cor­ro­sion re­sis­tance. It’s due to chem­i­cal com­po­si­tion, the most com­mon grade of 304 be­ing steel with 18% chromium and 8% nickel. Such fas­ten­ers are stamped ‘A2’. There’s also an­other num­ber which is 10% of the ten­sile strength, so my ‘A2-70’ bolts’ ten­sile rat­ing is 700N/mm². Now, if you’ve seen ‘8.8’ on a fas­tener it means high-ten­sile al­loy steel that’s been heat treated, and the TDR’S orig­i­nal bolts would’ve been some­thing sim­i­lar. Ten­sile strength is greater than 800N/mm², they’re more re­sis­tant to shear, and yield strength (the elas­tic limit; the point where the ma­te­rial de­forms) is around 50% higher than my stain­less. I’ve got fas­ten­ers that are weaker and eas­ier to stretch than they should be. You could ar­gue the alu­minium of the TDR’S forks won’t have the thread strength of the stain­less. You’d have a point. The bike’s only used for cheery trun­dles too, so brakes aren’t abused. How­ever, now I’ve no­ticed I can’t un-no­tice. Buy­ing OE parts is the easy fix, but I pre­fer the look of stain­less, so have ordered some ‘A4-80’. A4 means a grade called 316 (like 304 but with 3% molyb­de­num for more salt re­sis­tance), and the ‘80’ sig­ni­fies 800N/mm² – up there with the orig­i­nals for strength.

They’re 66p each. Peace of mind never came so cheap.

‘THE YAM ZIPS TO THE SHOP AND WHIS­TLES THROUGH ITS MOT’

ABOVE Mike’s bike among the ever-present clas­sics at his lo­cal bike shop

BE­LOW: One of the fas­ten­ers in ques­tion – but they have to have the right rat­ing for Mike

Stain­less bolts and hoses: not orig­i­nal, but pretty

MIKE AR­MITAGE

TDR was bought just over a year ago in or­der to re­live the ex­pe­ri­ences of 30 years ago. Shares shed space with a Honda C50 recom­mis­sioned af­ter a 34-year slum­ber.

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