fork oil

bernardo · Post by **bernardo** » Wed Sep 12, 2007 8:47 am

I've just blown a fork seal so I need to replace the fork oil (obviously).

What grade and air gap would any of you recommend, standard forks and springs, 100kg rider.

Also what sag figures should I use front and back?(standard rear shock)

I've no real problems with the forks so far (not really pushing it) but it does feel like it's going to tuck on slow corners. Rear's fine.

thanks

Bernard

fantic125 · Post by **fantic125** » Wed Sep 12, 2007 11:12 am

Hi Bernardo,
I got this from the TRX UK Forum. I've just replaced the seals in mine and thought I'd give it a try. I weigh 95kg.

Oil weight: 5wt (10wt standard)
Oil level: 513ml (483ml standard)
Preload: 3 grooves (6 grooves standard)
Damping: 2 clicks (standard)
Triple clamps: 30mm from top
Static sag: 7mm (without rider) 24mm with
Total fork travel: 90mm

It's improved over standard, but with the goat tracks we have for roads here, I'm finding the preload too harsh - I've dropped back to 4 grooves, and am about to try 5 grooves.
Hope this helps.

dfh · Post by **dfh** » Wed Sep 12, 2007 2:40 pm

fantic125 wrote:Hi Bernardo,
I got this from the TRX UK Forum. I've just replaced the seals in mine and thought I'd give it a try. I weigh 95kg.

Oil weight: 5wt (10wt standard)
Oil level: 513ml (483ml standard)
Preload: 3 grooves (6 grooves standard)
Damping: 2 clicks (standard)
Triple clamps: 30mm from top
Static sag: 7mm (without rider) 24mm with
Total fork travel: 90mm

It's improved over standard, but with the goat tracks we have for roads here, I'm finding the preload too harsh - I've dropped back to 4 grooves, and am about to try 5 grooves.
Hope this helps.

Yay.. another South Aussie on the forum. BTW a certain G Burgess lives in Aldgate...

I think however that the harshness you describe is not from the preload but from over filling the fork oil. The air gap trapped in the fork acts as a supplementary spring, but unlike the coil jobbie ( as Fred Gassit would say..

) air springs have a rapidily rising rate. Start with a smaller included volume from overfilling and the spring rate goes through the roof at about half travel, and totally rigid soon after. Hence the harsh feel.

I have seen the UK Forum advice before... as far as I am concerned it was another botch job by somebody too tight to spend a couple of hundred bucks to do the right thing and buy a set of fork springs.

I weigh 95kg in my riding gear. I have both a set of .9kg/mm and .95kg/mm forksprings but I tend to use the .95/kgmm most of the time with 15wt oil.

The approved method for setting oil level is by compressing the fork completely ( after pumping the oil a few times to get rid of air bubbles) without the spring and spacer and measuring the level from the top of the fork tube. The stock level is 130mm. With correctly weighted springs I actually set my airgap level @ 150mm to reduce the rather crude effect of the air spring. Put in 450ml and then little dribbles of oil to get the level.

Cheers
DFH

youngy · Post by **youngy** » Wed Sep 12, 2007 2:45 pm

If it's any help (and it probably isn't) Hagon suggest an airgap of 140mm. As dfh says, this helps to reduce harshness. I have Hagon springs fitted with 140mm air gap in one set of forks and they are far less harsh than my other set with stock springs and 130mm airgap.

If you're going to change a seal, you may as well do both legs and change bushes as well. It could be a worn bush that is causing the seal to leak and a new seal will not last long in that event.

I used 10w fork oil. You could use ATF if you're tight, but tbh you may as well buy a litre of good quality fork oil - Putoline HPX is very good.

Your front end tuck feeling is probably due to the 60 section front tyre.

bernardo · Post by **bernardo** » Wed Sep 12, 2007 3:10 pm

thanks for the advice guys and yes the 60 section is being replaced with a 70 as soon as it wears out (if ever)

billy budge · Post by **billy budge** » Wed Sep 12, 2007 5:47 pm

Tut tut tut marty

I thought you had been told before that its bushings and not bushes!!!!

youngy · Post by **youngy** » Wed Sep 12, 2007 6:18 pm

Still don't what they are - can't find em in any English dictionary.

pwmotorsports · Post by **pwmotorsports** » Sat Sep 15, 2007 8:53 pm

for mine Rider being 125KG i used 10wt @ 500ml it feels better so far but not really pushed it yet

cheesie · Post by **cheesie** » Sun Sep 16, 2007 12:02 pm

I just had new seals fitted along with ohlins springs oil standard wieght air gap standard pre load 5 rings showing forks protruding 28mm above yolks new sportec m3s 120/70 front 160 rear fitted 300 miles ago and love it this new set up gives me much more confidence in bike I almost high sided it last sunday when the side stand dug in on a tight left hander there,s not much more lean if any after the foot peg blob grinds out I weigh around 100kg also

bernardo · Post by **bernardo** » Fri Oct 05, 2007 10:06 am

Thanks guys
I went pretty much with fantics setting in the end, but 7.5wt oil and an extra click of rebound. Front end tuck is gone, . Still not perfect but a massive improvement.
Still got to replace the 60 section tyre and I'll try the springs......eventually