Fork Oil Questions...

Speed3Chris

Speed3Chris

I like Dick
Thought I would ask those that have experimented with fork oil if they found something they preferred to the stock oil? Unlike some, I am pretty happy with the front end of my '09 T100 and there is some speculation that Triumph tweaked the calibration for '09 and maybe why it feels pretty good.

Some of my basic questions are:
- When do you guys find the oil to get contaminated enough to change it...about how many miles or months?

- Have you found a weight and brand of oil you preferred to the factory fork oil?

- I know some just pick some up from the local motorcycle shop but any other suggestions for an on line source?

- Last question is...any tips for getting the proper amount of oil back in the forks? I am likely going to remove my forks for this but I may suck it out for the first time as it won't be too badly contaminated with low miles...so replenishing back to a particular oil level versus a replacement volume of oil back in maybe the best method and advice would be appreciated.

Many Thanks.
 
Last edited:
A

Aussie_T100

Banned
I can't really help you with a choice of oil as I have intiminators fitted which required 5w oil but I can tell you that the oil that came out of the right fork on my bike was contaminated (grey in colour) whereas the oil that came out of the left fork was as clean as the day it was put in. I've seen others report contaminated oil when making a change as well.

I did see a report somewhere by Pieman that there is much variance of viscosity between different brands even in the same weight grade.

Personally I have a preference for Amsoil products.
 
Speed3Chris

Speed3Chris

I like Dick
Crazy how one fork tube can be contaminated while the other isn't.
How many miles did you change your fork oil Aussie?
 
Speed3Chris

Speed3Chris

I like Dick
nohawk said:
I haven't messed with the Bonneville forks but I used ATF in my VFR and my Daytona.
Click to expand...
Kind of mystical subject really...like any oil thread. :) Hard to get a concensus on what to use...undamped...overdamped...what weight to use...level even affects fork performance. Thing about ATF for fork oil is, ATF is deliberately formulated to have a level of fricition for clutch engagement that is undesirable to fork function. Unclear what this downside is to fork seal life over time etc. Lots of people do use it in their forks and no doubt it works OK but if changing fork oil, pretty easy to just buy a liter of oil meant for the job...shouldn't be much more expensive if buying right. I was curious what experience has been with the bonnie in terms of weight in particular. I know many change to progressive springs in the process which clouds what oil weight is preferred as well. Tuning is a black hole. :) I am overall happy with fork damping on my bike. I presume the oil in there is 10W but not sure of that.
As Aussie mentioned, weight even varies from mfr. to mfr. so not easy to determine the best weight either.
 
Last edited:
Stars&Bars

Stars&Bars

Two Stroke
I'm glad you asked this Question as this subject has been on my mind lately too. I do plan on using Amsoil but was wondering what viscosity to use so any responses to this planed maitenance from those that have already done this will be appreciated.
Thanks Y'all
 
Kirkus51

Kirkus51

Hooligan
I believe the weight of the oil is 10w. Doesn't the fork oil and it's viscosity slow down the plunging of the forks as it's pushed thru holes and then sucked back? I had intimidators installed with requisite 5w oil since then and for sure there's a stiffer ride, but I've lost those pesky klunks going over potholes for the main part.

Just checked a manual and it says fork oil type is Kayaba G10.
 
R

Rev Olting

Scooter
I think fork oil is a very overrated subject. Over the decades I've dumped all kinds of lubricant down the holes, usually could not tell one from the next. IMO 5, 10, 15 weight, no one will know or care. Even ATF. As for change interval, there is one lazy school of thought that says - never. OTH, the only reason for frequent is if there is suspected seal failure. Rebound and damping are not the same things, and only oily springs matter except for the latter.

Please forgive me if I do not return to this thread, as I am off to harass the poor beasts on the Moto Guzzi forum. They are in much need of chastening.
 
Speed3Chris

Speed3Chris

I like Dick
Whether you return or not Rev, I appreciate your advice. Yup, rebound and damping are different but the latter i.e. damping is pretty big. :)
As to weight, some believe they can tell but perhaps as you say all overrated. Based upon this, probably 10 weight if replacing the oil would be a good target.
Thanks again.
 
D

drlapo

Hooligan
the correct viscosity is very important and will affect the action of the forks dramatically
use 10w as specified as even ATF is too "heavy"
ATF is a great hydraulic fluid for older Triumphs
 
HiVel

HiVel

Scooter
We put the specified measure of 20wt. fork oil in -----'s 2002 Bonnie with 36,000 miles on it and it works great. I used some
Amsoil 7.5 wt. fork oil in my Thrux with intiminatiors and h-d springs, and put 10wt. in my T100 that has heavy duty springs-cant seem to tell the difference-all work well. Whatever?? Correct amount and clean oil is good.
 
Speed3Chris

Speed3Chris

I like Dick
HiVel,
Your experience seems to support what the Rev said.
Fork oil weight +/- is close enough for horseshoes. :)
Thanks!
 
HiVel

HiVel

Scooter
Got me to remembering-I used to go to the airport and buy aircraft hydraulic oil for my 1982 BMWR100RS -HA-that stuff would eat through a plastic bottle in time and stain everthing it touched bright red! Used to change it yearly.

I had a 1969 Suzuki TS 250 that I raced and ran unmercifully for about 4 years and never changed the fork oil! The forks worked beautifully for all types of riding. I actually did not know you could change fork oil back then.
Makes you wonder.
 
Last edited:
W

wbarnier

Scooter
fork oil

I have a 2009 Bonnie Black with 1400 miles on it and I replaced the stock fork oil with 7.5 weight Repsol fork oil. The amount was approximately one quart which was enough for both sides. I had the forks out to install rubber gaiters so I figured that would be a good tme to do it. If you pour enough oil in each leg to a height of 5 & 1/8 inches(130mm) from the top of the fork you will have only an ounce or two left from a quart. This is measured without the spring in the fork and the fork fully compressed. This has smoothed out the ride noticably and works well with my Hagon rear shocks which are slightly softer(18kg) than stock springs(20kg).

Bill
 
S

schnabba

Two Stroke
not all advertised weights are the same.... a 10wt. for one brand won't be the same as another brand... whatever one you like - find out what it's viscosity index is, so that if you switch brands or want to go heavier or lighter you have a good measure for where to begin. The 7.5wt. I use is slightly heavier than the honda brand 10wt as an example.... the 5wt of this brand is just under the honda 10wt.... so the "weight" measure can be misleading.

There are a lot of good discussions about this out there on the internet. http://www.advrider.com/forums/showthread.php?t=286065
 
You must log in or register to reply here.
Top