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…
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.