Replacing suspension bolts

Replacing suspension bolts

Author
Discussion

texaxile

Original Poster:

3,289 posts

149 months

Monday 2nd June 2014
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Hi,
I've got a bit of a problem with my project. After removing the Trailing arms etc and having them shotblasted and repainted, I took the old Bolts (which are threaded into the Chassis) to get them replaced. Fair play to the bloke in the fixings shop, he measured the thread and compared them, but upon trying them in the holes, it seems they don't want to go in (they "start" but then will not tighten anymore by hand). I've no idea why this is but as the old bolts are 30+ years old, will it be ok to re use them?.

They're a fine thread, Metric, on an 80's Jap Saloon.

Secondly, I was going to use Stainless bolts but was informed that Stainless has a lower tensile strength than regular steel (and as such is not suitable), but they can also seize in easier, so instead of going for aesthetics it's best to use regular Steel.

Thanks for any advice,
Cheers,
Pete

SnailTrail

107 posts

119 months

Monday 2nd June 2014
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You say they won't thread anymore by hand, did you try getting a ratchet or a spanner onto them? Sometimes if there's crap in the threads or the threads are corroded it will just take a bit more persuasion. You could try some thread grease on the new bolt and spray some WD40 into the threads on the chassis to try and loosen any dirt or corrosion.

If you are sure the threads on the two bolts are an exact match then there's no reason for the new bolts not to thread in.

one eyed mick

1,189 posts

160 months

Tuesday 3rd June 2014
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there can be some odd thread forms on jap stuff thread gauges should help

BritishRacinGrin

24,602 posts

159 months

Tuesday 3rd June 2014
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SnailTrail said:
You say they won't thread anymore by hand, did you try getting a ratchet or a spanner onto them? Sometimes if there's crap in the threads or the threads are corroded it will just take a bit more persuasion. You could try some thread grease on the new bolt and spray some WD40 into the threads on the chassis to try and loosen any dirt or corrosion.

If you are sure the threads on the two bolts are an exact match then there's no reason for the new bolts not to thread in.
Bad advice, this is a sure fire method of completely buggering threads if the pitch turns out to be slightly wrong.

BritishRacinGrin

24,602 posts

159 months

Tuesday 3rd June 2014
quotequote all
SnailTrail said:
You say they won't thread anymore by hand, did you try getting a ratchet or a spanner onto them? Sometimes if there's crap in the threads or the threads are corroded it will just take a bit more persuasion. You could try some thread grease on the new bolt and spray some WD40 into the threads on the chassis to try and loosen any dirt or corrosion.

If you are sure the threads on the two bolts are an exact match then there's no reason for the new bolts not to thread in.
Bad advice, this is a sure fire method of completely buggering threads if the pitch turns out to be slightly wrong.

TheRealFingers99

1,996 posts

127 months

Tuesday 3rd June 2014
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My guess is that somewhere between measuring and ordering there's been an error. Start again at the beginning.

SnailTrail

107 posts

119 months

Tuesday 3rd June 2014
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BritishRacinGrin said:
Bad advice, this is a sure fire method of completely buggering threads if the pitch turns out to be slightly wrong.
That's why i said if he is sure there are an exact match, although I probably should've put that at the beginning rather than the end. If the old bolt threads in fine and the new one doesn't the threads are obviously different.

Snake the Sniper

2,544 posts

200 months

Tuesday 3rd June 2014
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If the bolts are old and rusty, so will the chassis mounts be old and rusty. Best to get a tap to match the bolts and run in into all of the mounts before using the new bolts.

Stainless bolts are also more brittle than "normal" steel bolts, which is bad for suspension shock loads. 8.8 grade bolts will generally be fine unless the manufacturer spec'd something stronger for some reason.

330p4

668 posts

229 months

Saturday 7th June 2014
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Should use 8.8 HT bolts min or 12.9 if specified
Ian