Dommie fork oil (Castrolite)

What was recommended was a straight 20 grade oil. A quick look on google shows that many oil companies supply this grade of oil. The cheapest I could see was Rock oil at £4.72 for 0.5 liters. from demon tweeks tel. 08448158620.

Good luck

I am currently using motorcycle fork oil from Halfords. It does the trick and has been doing so for a number of years now. I suppose I should change it one day...

Have you considered using ATF. I was recommende to use this by a Norton person some years ago and it works beautifuuly on both my Commando and my Dommie 99. It has been suggested that it has better characteristics under compression than oil whic is really designed to lbricate with relatively thin film thickness.

Previously michael_jobson wrote:

Have you considered using ATF. I was recommende to use this by a Norton person some years ago and it works beautifuuly on both my Commando and my Dommie 99. It has been suggested that it has better characteristics under compression than oil whic is really designed to lbricate with relatively thin film thickness.

Hi Mike

I think ATF is only rated 5w and the recomended is 20w. I to have tried ATF and found it far to thin and bouncy. Must stop eating those pies.

Tony

Most ATF fluids have viscosity values similar to those of a 20W straight oil. whether or not they are better than a conventional fork oil is uncertain.They do contain friction reducing additives which might smooth the fork action.

Other people seem to shock absorber fluid, usually these have lower viscosity than our 20W fork oil, or jack oil which has a 20W viscosity.

Halfords 5W30 fork oil is probably a good bet.

Previously charles_bovington wrote:

Most ATF fluids have viscosity values similar to those of a 20W straight oil. whether or not they are better than a conventional fork oil is uncertain.They do contain friction reducing additives which might smooth the fork action.

Other people seem to shock absorber fluid, usually these have lower viscosity than our 20W fork oil, or jack oil which has a 20W viscosity.

Halfords 5W30 fork oil is probably a good bet.

I always used to use 20/50 engine oil in my Atlas.

I now have a commando & use modern fork oil 10w.

ive found that the forks are stiff using the reccommended amount so kept putting a bit more in each leg until it felt better.

there must be a lot more in now than the manual says but the forks work a lot better.

I also found 5w a bit thin so went for the 10w. Mine seems better now than it has for years with the excess oil.

Just how much oil should we use? I was lead to believe that the correct amount was 142 mls. This figure comes from an article in an old Classic and Motorcycle Mechanics by Mick Hemmings and has, I believe, been repeated in other articles by our furry friend. The Manual quotes 7 fluid ounces which converts to a tad under 199 mls.

Who is right?

Hi Charles,

The original Norton owners handbook states:- " Pour in a measured 5 fluid ozs (142 cc's.) of 20 grade oil in each leg." The handbook is an original factory item, and covers from the model 50 & ES2 singles, up to the 650 Mercury. However, I have seen in other, third party, manuals varying amounts, up to 200 cc's recommended. Which reminds me, my forks are overdue an oil change!

Regards, John..

This is weird, my Plumstead manual says 5 fluid ounces but my Bracebridge Street one says 7!!

The plot thickens

Previously charles_bovington wrote:

This is weird, my Plumstead manual says 5 fluid ounces but my Bracebridge Street one says 7!!

The plot thickens

Ah, my handbook is the Plumstead version. Possibly AMC decided they knew better than Norton, or,maybe their version of Roadholder forks varied very slightly from the original. From previous posts, it would seem the exact grade, or quantity, make little difference!

I have always used Castrol 20W/50 in my M50 featherbed forks without any trouble at all. The last change is still in after 10k miles and is now probably due for renewing.

In theory, with the oil being multigrade, the forks should retain some stiffness on hot summer days as the forks warm up, compared to a straight 20 grade.

Previously peter_coates wrote:

Previously michael_jobson wrote:

Have you considered using ATF. I was recommende to use this by a Norton person some years ago and it works beautifuuly on both my Commando and my Dommie 99. It has been suggested that it has better characteristics under compression than oil whic is really designed to lbricate with relatively thin film thickness.

I shall bare this in mind for the future Mike, thanks

Pete.

Decided to give ATF a go as local Motor Factor's had this in stock, but not fork oil. Does ATF mix ok with the 20/40 oil I currentlyuse, or wil fork need a flush through?

regards,

Chas

I have just built a set of Commando forks for my ES4. I put the extra double top fork bushes in and drilled 4 off 1/4" holes above the tapered part of the damper rod. I have used 150cc of 15/40 semi synthetic in them and although I have not been on the road they feel nicely damped with no topping or bottoming out.Time will tell

Cheers Tony