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Offline jm2

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Re: Swing arm bearings
« Reply #10 on: 17 April, 2018, 04:09:02 PM »
Well that muddies the water (or oil) then.

If every/most manufacturer/s are quoting fork oil as (SAE) W ratings that'll be 'cold' figures (-10°C IIRC) - they really ought to be the same at 'standard'.  But forks are running ambient to (how?) warmer - say 20°C for sunny England, and they may not have a fixed relationship with increased temperature, so ordinarily all bets are now off.

Add in a new (under pressure) rating and at 40°C at that (wouldn't have thought my fork oil gets that warm), then those bets are further off than before.

Fail to measure the air gap (or deliberately vary it) and I've given up guessing.

Reckon I'll use the said cushion oil and 180mm air gap  ...

<edit 180mm just looked it up>>
« Last Edit: 17 April, 2018, 04:11:47 PM by jm2 »
Only do it right - no bodging please.   Keeper of the failed stator list.   John.

Offline sambaman

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Re: Swing arm bearings
« Reply #11 on: 17 April, 2018, 05:03:04 PM »
*Originally Posted by Shed [+]
I personally think there are many variables to what oil 'suits' you. Your personal weight, the weight you'll be most likely carrying around, your style of riding, the temperature, what the roads are like where you are riding, what 'feel' from the front end you personally like, etc etc. Simplified, a lightweight rider just going up & down the motorway is most likely going to be fine with low weight fork oil, whereas a more heavily set rider blasting around the lake district may find a slightly heavier fork oil will give a more comfortable ride. Ultimately, it's all going to come down to personal preference. It's your bike, and you're the one riding it. You know what you like best. Fork oil is extremely cheap, so if you don't like one, you can easily change it for another weight oil within a couple of hours.


The labelling of the fork oils, 7.5W, 10W, 15W, 20W, should be considered a 'rough guide'. Bear in mind one manufacturers 10W or 15W fork oil isn't necessarily the same as another manufacturers fork oil. If you want a truer comparison between the different manufactures, the sae 'weight' of the oils should be compared by their respective viscosity index number by way of a testing method know as Centistoke testing scale, i.e. centistokes (cSt). If you are having trouble sleeping, fill your boots with that one.  :800:


The manual states the Biffer's recommended oil is 10W using Honda's own 'Ultra Cushion Oil' brand. This oil has a cSt of approx 35. Compare this with Castrol fork oil 10W, which has a cSt of 32, or Rock Oil 10W with a cSt of 32, so both very similar to the recommended Honda oil. However, Silkolene Pro RSF 10W has a cSt of 47, or Bel-Ray High Performance 10W with a cSt of 53 - so despite these fork oils still being labelled as 10W oils they are both a far thicker oil than the Honda one, much less viscous, and therefore 'stiffer'.
Conversely, Putoline HPX 7.5W has a cSt of 33. So despite being labelled a much lighter 7.5W oil, it is actually almost the same in viscosity as the Honda 10W oil.


Do you know for a fact what oil is in your forks now? It could be anything. Has the oil ever been changed in the 50K the bike has covered?  :084:
Whatever oil you go with, combined with new springs, the front end is going to be vastly improved on what you have been riding with up til now.  :028:

Don't be paranoid about the oil you're putting in. The only way to find out what suits you, is to try it.  :028:


Also, these with 15W:
https://www.sportsbikeshop.co.uk/motorcycle_parts/content_prod/64159

Shed! The fork oil and seals were changed by my local mechanic at about 20k miles so they're definately due. I reckon they will have used 10W oil of some kind, but they were probably blissfully unaware (like me) of the complexity of the whole subject. Thanks for the insights!

Offline sambaman

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Re: Swing arm bearings
« Reply #12 on: 17 April, 2018, 05:19:55 PM »