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7wt vs 7.5wt for shock rebuild

BadDNA

BadDNA

hophead
Mar 31, 2006
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Living the dream.
Rebuilding a Rock Shox Monarch 3.1 tonight, mainly because the air seals are leaking and I'm losing pressure between rides I've only got one season on it so I'm not sure I really need to rebuild the damper. The instructions call for 7wt oil but I only have 7.5wt on hand. I'm a heavy guy though and what I want to know is, would I notice a huge difference if I rebuild the damper with 7.5wt oil instead of the 7wt recommended in the service instructions?
 
jonKranked

jonKranked

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Nov 10, 2005
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0.5 change in weight isn't gonna change anything. most people can't tell the performance difference from a 2.5wt difference (say 5wt to 7.5wt, or 7.5wt to 10wt), yet alone a 0.5wt difference. I regularly change between oil weights like this, have been doing so for YEARS and on multiple shocks and forks, and have not had a single issue. Only EXTREMELY subtle performance changes as well, to the degree that most riders can't pick up on it.

Besides, OP isnt exactly a small guy, so it wouldn't hurt to have a teensy bit heavier weight.
 
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HAB

HAB

Chelsea from Seattle
Apr 28, 2007
11,580
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Here's the thing: the 2.5/5/7/7.5 etc scale of measuring oil weights blows goats. Here's why: manufacturers aren't even slightly consistent with how they label their stuff. What matters is the viscosity, measured in centi Stokes (cSt). See columns 1 and 2 below. The latter columns are about how the oil changes viscosity changes with temperature, high viscosity index = good. Viscosity temperature coefficient provides similar info, but in that case, low numbers are better. Ditto for VI.

 
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HAB

HAB

Chelsea from Seattle
Apr 28, 2007
11,580
2,006
Seattle
Also, the viscosity of the lubricating oil matters a LOT less than it does in the damper. You could put olive oil in there and it'd work fine.
 
jonKranked

jonKranked

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HAB said:
Here's the thing: the 2.5/5/7/7.5 etc scale of measuring oil weights blows goats. Here's why: manufacturers aren't even slightly consistent with how they label their stuff. What matters is the viscosity, measured in centi Stokes (cSt). See columns 1 and 2 below. The latter columns are about how the oil changes viscosity changes with temperature, high viscosity index = good. Viscosity temperature coefficient provides similar info, but in that case, low numbers are better. Ditto for VI.

Click to expand...
i was thinking about this as well, couldn't remember the source.
 
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