Front forks replacement oil 5 weight or higher for a fattish bloke ;)

[drawderm]

I ride a 2001 - st1100 and I'm wondering which type of oil to put in the front forks..

Honda state i need SS-7 which i understand is a 5 weight oil.

However, am just over 100kg in weight and the bike is 21 years old with 37k done. Does it make more sense for me to use a heavier oil such as 10 weight?

Also, should i get synthetic or mineral?

Thanks everyone!!

 

[drawderm]

No responses as of yet but just to feedback.

Ive put 5 weight oil and although it is fine at low speeds, at 70mph, i find the front is a bit light and 'jumpy'. I suspect a heavier oil is required.. i will take out 200ml each side and put in 10 weight oil and see how it responds. So thats about 7.5 weight given the proportion of each. If that feels ok, then i will drop the oil jn both and fill with 7.5 weight. If not then i will try 10 weight. Will keep this thread updated.

 

[Obo]

I just installed stiffer aftermarket springs on my 1300. They are also longer than the OEM ones and required additional preload spacers. They said to go with a lighter oil with them so that the rebound wasn't as harsh or rough.

The springs deal with the compression (the bump) and the fluid does the rebound.

So with a stiffer spring you likely want a thinner oil.

The amount of fluid also helps with the compression spring as an "air gap."

Just changing your oil weight may not make your bike feel any better, depending on what you are trying to achieve.

 

[motornut]

I know this sounds anal, but spend the money to have your forks done up with new valves and new springs. Changing the oil weight is a hit or miss option.With the weight of the operator it is the rear shock that takes the initial load until you hit the brakes hard, then the front slows the dive. With an older bike the springs are probably weaker and as long as your into the forks do it up better

 

[drawderm]

I just installed stiffer aftermarket springs on my 1300. They are also longer than the OEM ones and required additional preload spacers. They said to go with a lighter oil with them so that the rebound wasn't as harsh or rough.

The springs deal with the compression (the bump) and the fluid does the rebound.

So with a stiffer spring you likely want a thinner oil.

The amount of fluid also helps with the compression spring as an "air gap."

Just changing your oil weight may not make your bike feel any better, depending on what you are trying to achieve.

Noted and thanks.. i will try different weights until i hit the sweet spot. I've measured my springs and they seem to be fine. I find the whole point of having an older bike is that you get the spanners out and make 'improvements' by trying different things. Dont see the point in paying others to fix things.

 

[Larry Fine]

Remember, the oil only resists motion. Only the spring (and the captured air) supports weight. I'm also a big guy, so when I rebuilt the fork on my '96 CB750ST, I added 1/4" extra fork oil.

 

[Ron]

There is no standard for fork oil weights across different brands. Stay with the same brand as you try different weights.

 

[drawderm]

There is no standard for fork oil weights across different brands. Stay with the same brand as you try different weights.

I wasnt aware of this, thanks!

 

[drawderm]

Remember, the oil only resists motion. Only the spring (and the captured air) supports weight. I'm also a big guy, so when I rebuilt the fork on my '96 CB750ST, I added 1/4" extra fork oil.

Thanks, sorry, do you mean a quart of a pint? Ie. 568ml?!

 

[Larry Fine]

Thanks, sorry, do you mean a quart of a pint? Ie. 568ml?!

No. Most fork-oil specs indicate a specific height of oil with the fork collapsed, rather than volume.

I added 1/4" of oil in each tube to decrease the air volume slightly, effectively increasing spring rate.

Added: About 6.5mm

See: https://motocrossactionmag.com/mxa-tech-spec-fork-oil-height-is-the-magic-bullet/

 

[drawderm]

No. Most fork-oil specs indicate a specific height of oil with the fork collapsed, rather than volume.

I added 1/4" of oil in each tube to decrease the air volume slightly, effectively increasing spring rate.

Added: About 6.5mm

See: https://motocrossactionmag.com/mxa-tech-spec-fork-oil-height-is-the-magic-bullet/

Ok so if it called for 400ml then you added 100ml/25% more. Is this what you mean?

 

[Larry Fine]

Ok so if it called for 400ml then you added 100ml/25% more. Is this what you mean?

No. ( " = inch.) 1/4" is one-quarter of an inch of distance, not a volume.

If the specs said to fill the tubes with oil to 3-3/4" from the top, I filled to 3-1/2" from the top instead.

 

[dduelin]

There is no standard for fork oil weights across different brands. Stay with the same brand as you try different weights.

Your statement is largely true but regarding sticking to same-brand comparisons one can consult this chart to compare fork oils by test values with the brand and “weight” only for identification. Oils clustered closely above and below Honda SS-7 will be very similar to SS-7. Thicker oils below SS-7 and thinner above.

Suspension fluids | Peter Verdone Designs

www.peterverdone.com

 

[drawderm]

Understood but Jesus christ.. not everyone lives on planet imperial you know!

 

[drawderm]

Your statement is largely true but regarding sticking to same-brand comparisons one can consult this chart to compare fork oils by test values with the brand and “weight” only for identification. Oils clustered closely above and below Honda SS-7 will be very similar to SS-7. Thicker oils below SS-7 and thinner above.

Suspension fluids | Peter Verdone Designs

www.peterverdone.com

Excellent thank you!