high tensile bolts?

[johnakay]

what grade in stainless steel that is near enough?
its for the shock absorbers,thinking of fitting these on my new scooter.
currently 795 mm in height and barely can get my leg over the seat.

Pardon our interruption...

this what I've bought to replace my Forza 750.

 

[keithski122]

Cool. I bought a vespa gts 300 to replace my vespa px200 and I absolutely love it, worlds apart with modern tech. Fantastic to ride on the mmotorway and actually be able to overtake stuff.

 

[ajlelectronics]

Rule of thumb is that stainless should not be used for such applications as they are not strong enough. I can't remember why but no doubt someone will be along to tell us.

 

[Richiew]

Too hard, I think. Prone to fracture?

 

[optima21]

I think A4 stainless (316 grade) has roughly the same tensile strength as 8.8 standard bolt, but high tensile bolts are normally 10.9 or 12.9 so the stainless isnt a strong as them

 

[bricol]

Technically, 8.8 is hi-tensile. 4.8 might be termed "standard" (or cheese ).

Stainless has worse fatigue properties than mild steel - and that bracket looks a good way to add extra stress to the standard spring mount!

 

[hotponyshoes]

Tensile grades of stainless bolts are available easily enough. Maybe not in small quantities though?
Grade 8 is available in a good variety of sizes, I've got a selection here that I use for ramps etc on horseboxes.

Grades 10 & 12 don't seem to be particularly rare either.

 

[brightspark]

most of the nuts and bolts on my norton are ss steel including the wheel spindles

 

[Onoff]

I always thought A2 or A4 Grade 80 rather than 70 had the approximate same tensile strength as 8.8.

 

[Munkul]

The tensile equivalent of grade 8.8 (ISO standard) is grade 80 in stainless, but as Bricol says, its not as clear cut as all that, as stainless has a much different stress-strain curve than carbon steel. So much so, that you cannot just substitute SS in engineering applications without doing some specific qualifying testing first.
Having said that, I've had a lot of experience using stainless a4-80 bolts in low pressure chemical pipework with few if any problems. At higher bolt stresses I think you'd maybe find problems.

I believe you can get a grade 90 or maybe 100 SS fastener, but I'd be very wary of these.

Don't mix up grade 8 bolts (ASME/ASTM) with grade 8.8 ISO... they are not the same at all

 

[Erie Fred]

what grade in stainless steel that is near enough?
its for the shock absorbers,thinking of fitting these on my new scooter.
currently 795 mm in height and barely can get my leg over the seat.

Pardon our interruption...

this what I've bought to replace my Forza 750.
View attachment 455103

What did the OEM have ?

 

[Smallfry]

I always understood any stainless should not be used for any suspension applications.

I have always found it brittle. Heres a test for you. Torque up a SS bolt into a nut held in a vice, undo and repeat until the head snaps off, they try the same with an 8.8 HT steel bolt and see how many cycles you get.

I have also tried it with stainless steel woodscrews, and have found they are one use only.

I thought they used titanium fixings on bikes ? Not a biker so don't know.

 

[bricol]

I've never had an issues with stainless fasteners, other than galling, in my engineering job. But I wouldn't use it in anything load bearing in a motor vehicle, especially one with not many spare wheels on the ground.

I had a bolt snap in the rear suspension of my Caterham a few years ago - on slow speed bit of reasonably straight road - dropped the rear nearside so the inside of the rear wheel arch became the supporting member for that side - the tyre rubbing inside it just kept the car off the ground sort of. If it had happened a mile sooner round a fast sequence of bends, I probably wouldn't have been calling the recovery truck, someone might have been calling one with blue lights for me.

No visible sign of imminent failure a week or so before from a good overall inspection - every bolt in the suspension got changed - 19 yrs and 50,000 miles.

 

[Morrisman]

most of the nuts and bolts on my norton are ss steel including the wheel spindles

I’ve used stainless bolts on just about every car or bike I’ve ever built, and never had one fail.

Stainless may not be as strong as a proper carbon steel high tensile equivalent bolt, but that doesn’t mean they are made of glass, or cheese.

The stock bolt is probably a minimum 3 times stronger than it would ever need to be, in a worse case scenario, so swapping it out with something marginally weaker is not a problem.

 

[Agroshield]

The stainless/not stainless is not relevant here. Look at what the bolts are doing and the load path.

Looking at the part and what it does, it may be that the supplied bolts are 'fitted bolts', with shanks that match the ID of the bearing.

That would be even more evident from the OEM parts as they _will_ be properly engineered for the application.

You'd want the bolts to fit the bearing well to stop any play. Note also on the ones supplied that the length of the unthreaded shank approximates the length of the bearing.

The worst thing to replace the supplied bolts with would be a fully threaded item (setscrew) as then the ID of the bearing is pushing on threads so the load is distributed over a much smaller area and the threads will damage the ID of the bearing.

 

[Morrisman]

“Protect the rear bumper for more comfortable walking”

What does it even mean?

 

[Agroshield]

What does it even mean?

From the listing: "This will lower the seat by 3-5cm. Perfect compliment for our lowering link giving you a lower more comfortable riding height"

To the OP: the spiel above implies that the two parts shown are to be use in conjunction with a 'lowering link'. I mention this just in case you had not seen it.

 

[Morrisman]

From the listing: "This will lower the seat by 3-5cm. Perfect compliment for our lowering link giving you a lower more comfortable riding height"

To the OP: the spiel above implies that the two parts shown are to be use in conjunction with a 'lowering link'. I mention this just in case you had not seen it.

I can see what it does, just I hope the manufacturers quality control is better than their English.

 

[johnakay]

“Protect the rear bumper for more comfortable walking” not a clue. lol
I've had a couple of billet bracket for footrest ,dropped one bike on it side.
bent the foot rest bracket but it took some doing to straighten it,no cracks etc so its good quality.
between 3cm/5cm is quite a lot 1.1/4"- 2"..
s/steel is out on for other but not shocks etc.
thanks for the replies.

 

[Smallfry]

I've never had an issues with stainless fasteners, other than galling, in my engineering job. But I wouldn't use it in anything load bearing in a motor vehicle, especially one with not many spare wheels on the ground.

I had a bolt snap in the rear suspension of my Caterham a few years ago - on slow speed bit of reasonably straight road - dropped the rear nearside so the inside of the rear wheel arch became the supporting member for that side - the tyre rubbing inside it just kept the car off the ground sort of. If it had happened a mile sooner round a fast sequence of bends, I probably wouldn't have been calling the recovery truck, someone might have been calling one with blue lights for me.

No visible sign of imminent failure a week or so before from a good overall inspection - every bolt in the suspension got changed - 19 yrs and 50,000 miles.

I think thats what happened to Jim Clark