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Piston grade
Posted: Sat Dec 13, 2014 1:13 pm
by Fux
Idiot question time.
What does the grade A B C , stand for?
Re: Piston grade
Posted: Sat Dec 13, 2014 1:26 pm
by bristolmod
I think its the actual size of the piston as fitted into the bore at the factory.
It takes into allowance production tolerances- some bores are slightly larger/ smaller than others, therefore this has to be allowed for when fitting a piston.
I think.......
Chris
Re: Piston grade
Posted: Sat Dec 13, 2014 1:59 pm
by cgt75b
My understanding of it is. A grade is just that, A grade the best piston you can get, I may be wrong ! It wouldn't be the first and certainly won't be the last .
Re: Piston grade
Posted: Sat Dec 13, 2014 3:54 pm
by purple_pill67
From a Q asking the same on mb site
"A B C D, what is the difference? Regard "
MB Group, Serious Outdoors Ltd replied: These pistons come graded to suit the cylinder bore size, on the cylinder there should be a letter A, B, C or D. Usually if the bore is not worn you match a piston to bore. A = A etc, if not sure sure let us measure the bore for you.
Re: Piston grade
Posted: Sat Dec 13, 2014 5:52 pm
by Boo
When the bore wears you could go from a grade A to a grade B piston and so on.They go up in .0005" (inch) incriments.
Pistons and barrels are usually matched.
Re: Piston grade
Posted: Sun Dec 14, 2014 3:01 am
by rosscla
cgt75b wrote:My understanding of it is. A grade is just that, A grade the best piston you can get, I may be wrong ! It wouldn't be the first and certainly won't be the last .
Yep you're wrong.
It's related to the bore & clearance, on a nominal 70mm bore the ABC Pistons might be 69.95, 69.96, 69.97. Might mean different for different manufacturers.
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Re: Piston grade
Posted: Sun Dec 14, 2014 7:41 am
by cgt75b
rosscla wrote:cgt75b wrote:My understanding of it is. A grade is just that, A grade the best piston you can get, I may be wrong ! It wouldn't be the first and certainly won't be the last .
Yep you're wrong.
It's related to the bore & clearance, on a nominal 70mm bore the ABC Pistons might be 69.95, 69.96, 69.97. Might mean different for different manufacturers.
Sent from my iPhone using Tapatalk
Thanks Rosscla for the explanation, I've learnt something new today
Re: Piston grade
Posted: Sun Dec 14, 2014 2:02 pm
by drunkmunkey6969
cgt75b wrote:My understanding of it is. A grade is just that, A grade the best piston you can get, I may be wrong ! It wouldn't be the first and certainly won't be the last .
That's why most people stick to class A drugs, you are guaranteed better quality. That's right isn't it? lol
Re: Piston grade
Posted: Mon Dec 22, 2014 8:53 pm
by byron
we were discussing this at the weekend, a mate was looking into mitaka 70mm pistons.
he was told, by supertune, that A ~ 69.97mm; B ~ 69.98mm; C ~ 69.99mm
Re: Piston grade
Posted: Mon Dec 22, 2014 11:34 pm
by rosscla
byron wrote:we were discussing this at the weekend, a mate was looking into mitaka 70mm pistons.
he was told, by supertune, that A ~ 69.97mm; B ~ 69.98mm; C ~ 69.99mm
Agree, had the same figures for the non avanti pistons. Other kits may be different and will be matched to the bore to get the right tolerance. If in doubt get it measured by someone who knows how to work bore gauges.
Original SIL barrels for example are often graded -, 0, + and pistons available to match. Once they've been rebored though all bets are off.