ATF, 10wt, 15wt, 10-15wt mix fork oil for gl1500 EDIT

SmartBiker said:

while waiting on my parts to come in for the fork rebuild,

i was wondering whats your choice of fork oil for the 1500, atf, 10wt, 15wt and why

also have you guys tried mixing oil weights for finer tuning?

thanks

Click to expand...

... hhmmm fork-tuning... ? Lemme see, they take oil, right? :wink:

Mr Verdone has done a bit of digging on fork oil weights, including ATFs, which displays measurable properties for several brands; there's a handy refernce table on the bottom of the page here ( link ), which has been retyped here ( link ). I find this second like handy for quick lookups as it supports text searchin where MR. Verdone's original material is presented in a less-searchable format. (I carry this data in my cellphone as an Excel sheet for easy reference)

For myself, I've always been a worry-wart about how the various additives from different products would play together, so I try to avoid mixing. The more realistic part of me knows that creating some caustic foaming componant-etching, seal-eating mess inside my forks is really & truely unlikely, but if it's gonna happen, it'd be in my forks for certain :wink:. With the number of choices available, and the difficulty in exact reproduction of the mixes, I kinda stick to one bottle at a time for whatever fluid I fill with.

To me, all of the fork-oil tuning tricks relate more to understanding that overall fork rates (both compression and extension) are determined by the oil viscosity, and that ONLY the compression rate (and also anti-dive efficacy) are determined by the fill level (higher oil volume is stiffer).

You ask about what oil I would use - I run a few different oils base on the plan for the day, but generally I stay with something that I can find locally and reasonably well nationally. Personal preference is to have an oil that performs the same hot as it does cold (these are the higher values of "VI" on the linked data; I use the recalculated "VI" values).



In short (performance and availability considered):

1. My 1st choice would be Silkolene Pro RSF (7.5w for touring, 15w for playing with a lower fill level)
2. My 2nd choice would be Bel-Ray HVI (10w for touring, 15w is ok - but nothing to write home about)

This is on an '88 with Progressive Coils in the front (tight end up) and Progressive 416s with 4.5oz (normal is 2oz) of Mobil1 ATF

I hope that's of some help. It'd be great to hear back on what you found works well for you.