getting all front fork travel

fe600racer · Jul 8, 2009

Two of us with bergs have noticed we do not get all our travel in the front forks. These bikes are used for enduro and not font wheel landings. As there are two bikes we have experimented by changing to lighter springs, lowered air chamber as far as allowed, reduced dampening etc. Has anyone had this lack of full travel problem and what did they do?

Taffy · Jul 8, 2009

you have a pair of cups called bottoming cones. the plastic part of the inner rod dives into these cops and they are next to the base of the springs.

i drilled mine and suddenly i had another 2" of travel.

regards

Taffy

bushmechanic · Jul 8, 2009

go faster ?

reduce travel ? thinner oil?

you could reduce the oil level till it only just covers the bottoming cones or just go lighter again on the spings

Taffy · Jul 9, 2009

no bushie

that's NOT the problem. the bottoming cones IS the problem. mind you i am on about the 4860 forks here....

regards

Taffy

bushmechanic · Jul 9, 2009

Ok Taffy ill take your word for it

but for those interested in not drilling the cones for whatever reason it might pay to read smorgys posts in the fork tuning thread, he has the same forks.

may ways to skin a cat, i used all my travel so often I had to create more of it in order to use less.

she said ok but your only allowed to use half the stroke....

"yeah orrite i promise"

then "is that it?"

"ahh Its only half way in messis"

"aw I changed me mind gwan stick it all the way in. "

awkward silence......

"nah nah a promise is a promise"

fe600racer · Jul 9, 2009

thanks Taffy/ Bushie,

I think Taffy has the answer ... I can't see the cups in the fork break down diagram, but will pull them apart and have a look. Taffy how big did you drill the holes? Do you know what they call those cups on the fork break down diagram.

regards

PS: Bushie you bike sounds much more agreeable than mine.

Taffy · Jul 9, 2009

bottoming cups is what 'we' call them?

they are in the doc and there is a diagram and description of the process.

http://ktmtalk.com/index.php?s=b60492d5 ... owforum=11

you want to get involved over here as they are on the same stuff as us!

regards

taffy

mud400 · Jul 9, 2009

By drilling the bottoming cones, doesn't it make it more harsh when you do bottom out?

Wouldn't a better solution be to run thinner oil and re-valve accordingly?

Remember, you can always make the holes bigger, start conservatively.

bushmechanic · Jul 9, 2009

PS: Bushie you bike sounds much more agreeable than mine.

well it is now

but the harsh clank of metal on metal and jarred wrists at 50km/hr in 2 foot deep breaking bumps makes me cringe everytime I hear of people drilling the Bcs. Ok i know not everyone has those kind of bumps ......

By drilling the bottoming cones, doesn't it make it more harsh when you do bottom out?

yes, absolutely. the clearence in the cups is allready very big. a better solution would be a longer cup with tighter tolerances that you can drill however you want later.

you can always make the holes bigger, start conservatively

if I needed to drill the cones I would use a 1mm bit and drill a number of holes along the length.. stronger and more tunable, the cups offer a bit of postion sensitive damping .. why not use it. using only 2 holes is quite crude.

the penske shock tuning PDF in the fork tuning thread has some info on relative flow rates through different diameter holes.

fe600racer · Jul 10, 2009

thanks Taffy, I have it now in the doc. I have joined ktm talk, seems like some good stuff there also.

Taffy · Jul 13, 2009

but i have the 50mm bottoming cones....

i wouldn't dream of drilling the standard 30mils!

regards

Taffy

fe600racer · Jul 13, 2009

Taffy,

I will have to take the forks apart and see what is in there. The Doc talks about drilling 20mm down and another 40mm down. It looks like the bottoming cones referred to are about 80 mm long (the 40mm hole seems about half way).

getting all front fork travel

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