With all due respect to what others have written regarding bolt, threads,
lengths etc., here is my own experience.
1. I replaced my crossmember bolts with grade 8. Yes, I was caught between
two sizes. I simply opted for the longer of the bolts and used hardened
washers to get as correct thread depth as possible. In a worst case senario
(damaged threads) I would think one could just (barely) drill out the tubes
slide in a longer bolt and put a nut on it. It seems the bulk of the force
is perpendicular to the tube, rather than pulling on the threads themselves.
2. I have cut threads with a die in both grade 8 bolts and the Tiger rack
arms. I did extesive back cutting (maybe ever 1/12th of a turn or less).
Yes, it took a long time. Yes, at the end the dies didn't look great, but
they were not that bad either. I would think one "might" actually cut at
least another set with these (left/right thread) $9 dies. Extensively rotary
wire brushing the threads removes the small amount of burrs that were left.
Now, my appication was rather unique. Some previous owner has broken a rack
arm and welded an Alpine piece in. I was not too thrilled about this. After
much contemplation I opted to cut the rack arms, thread them, create a
right/left thread rod from the grade 8 bolt and then use an AMC (Hornet, but
they are all pretty much the same) tie rod adjustment sleeve to connect
everything together.
Sort of like this:
Rack Arm Sleeve Threaded Grade 8 Bolt Tie Rod
End
=========/////////// /////////\\\\\\\\\ \\\\\\\\\\\\=////////////
//////////////////O
Not only did this solve the kludged welded rack arm, but it offers toe
adjustment in fine incriments. I was cautioned that the rack was too hard
(and small near the end I was threading). The die was adjustable (to
compensate for the thinning area of the rack) and the AMC sleeves clamp onto
the rack thus making for a very snug fit. Sometimes the theory of doing
things and the reality are two different things.
As a kid one of my favorite movies was "Airport." George Kennedy had some
youthful "cockpit qualified" guy shouting at him as they pushed a plane to
the limits trying to get it unstuck from a runway. The kid screams "Mr.
Petroni can't you hear them (on the radio), they said to shut the plane
down." Kennedy shouts "Can't hear a thing, there's too much noise." He then
puts his cigar in his mouth hits the throttles and out the plane comes.
Sometimes you just have try and see for yourself.
Tom Witt
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