I guess this is a common question but I couldn’t find a definitive answer. Pikes require a bit of 5wt and a bit of 15wt. My local motorbike shop has 5wt, but no 15wt. I can buy two bottles, one 10wt and one 20wt and mix them, but it’ll cost me £7 more and I’m a cheapskate (bike is being very expensive this month…)

Does anyone know if it’s ok to use either 10wt or 20wt instead of the 15wt? Or should I just shell out and do some mixing?

If anyone in Leeds wants to go halfs, I am going to end up with about 10 years worth of fork oil here…

Cheers

use thinner oil get less damping, use thicker get more

Its no necessarily a straight mix either for some odd reason.

Is the 15 wt the lube oil ( a few mils in the bottom of the legs?) if so use 10 wt happily – it just will escape more quickly

I believe the 5wt is the damping and the 15wt goes in the lowers. The guy in the bike shop said mixing the 10 and 20 would produce 15wt.

just put ten weight in the lowers then. You can mix the oils but I believe that due to the way the additives work 50/50 10 and 20 wt does not always give 15 wt. NO proof on that – just heard it a few times.

The oil in the lowers is just there to lubricate – you can use synthetic engine oil instead or a blend of fork oil and RS Red Rum, as long as it’s oil, mixing grades’ll be fine, it doesn’t need to be exatly 15W as it doesn’t damp just lube the movement. I’d use either 10W or 20W, the 10W is probably going to be less viscous in winter, so may be a better choice at this time of year though gawd knows if it makes a significant difference in that role.

The 5W stuff is in the damper and that is important, heavier weight oil will slow the damping down, lighter stuff will speed it up, 5W is the OE grade oil, so should give you same level and spread of damping as the fork had as new.