Forks - Travel.

[Sidepod]

So just to get a general idea of what's going on, my bike has 180mm Fox 36's. The brochure says so, FoxRide.com confirms the serial number as such.

When I measure the the forks for sag calcs etc, I get 172mm. This is taken from the very top of the stanchion where the tube butts up to the crown down to the top of the dust seal with the bike elevated for max extension. I get that total travel probs includes internal bump stops theoretically squashed etc but if Fox know this slight discrepancy why is it not highlighted in the manual for sag % calcs?

 

[Sidepod]

Ok, I wasn’t looking for sag info, more about why the total apparent travel is different from the spec sheet.

The point being, 25% of 172 is a different value to 20% of 180.

 

[Mteam]

could be sagging a little under the weight of just the bike? have you measured if you lift the front end off the floor?

I wouldnt worry too much about it though, just set your sag to get your preferred ride feel and go from there

 

[Sidepod]

could be sagging a little under the weight of just the bike? have you measured if you lift the front end off the floor?

I wouldnt worry too much about it though, just set your sag to get your preferred ride feel and go from there

"with the bike elevated for max extension"

 

[Mteam]

"with the bike elevated for max extension"

sorry didnt see that in the original post.

Wouldnt worry about it, I've had forks that when measured like that have been 5mm short of what they're supposed to be, doesnt seem to affect them.

However , if youre really bothered It could be that there is a bit too much air pressure trapped in the negative air chamber of the air spring, try slowly (really slowly) letting air out while simultaneously pulling the lowers down, once all air is is released from positive and negative chambers, re inflate to desired pressure, stopping at 10 psi increments to cycle the fork through the first 10-20 mm travel very slowly to let the air chambers equalise. There's a bit of a knack to this .

 

[Sidepod]

sorry didnt see that in the original post.

Wouldnt worry about it, I've had forks that when measured like that have been 5mm short of what they're supposed to be, doesnt seem to affect them.

However , if youre really bothered It could be that there is a bit too much air pressure trapped in the negative air chamber of the air spring, try slowly (really slowly) letting air out while simultaneously pulling the lowers down, once all air is is released from positive and negative chambers, re inflate to desired pressure, stopping at 10 psi increments to cycle the fork through the first 10-20 mm travel very slowly to let the air chambers equalise. There's a bit of a knack to this .

Cool, good advice. I went through all of this a few times last night just to be sure (I was adding volume spacers at the time). That was my initial thought, negative air etc. I did pop the axle back in, stand on it and pull the forks up to extend/expel air etc.

You're right, non of this is particularly critical, I just like to understand exactly what's going on. Despite the RideFox intel clearly stating a 180mm fork, I just wonder if it's actually a 170 air shaft assy that's been installed?

 

[steve_sordy]

.............You're right, non of this is particularly critical, I just like to understand exactly what's going on. Despite the RideFox intel clearly stating a 180mm fork, I just wonder if it's actually a 170 air shaft assy that's been installed?

I bought a bike that was supposed to have 150mm travel. I specifically requested that it had 150mm, because the previous model had 140mm and the new model had 150mm. It looked like a 150mm, but to reassure me, the sales guy measured the exposed amount of stanchion at 150mm. I persisted and he asked the tech guy to come and take a look. He played around with it and pronounced it as 150mm. He could see that I was still not 100%, so the sales guy went to the on-line tech docs for the fork manufacturer and typed in the serial number and it was confirmed as a 150mm travel fork. OK, I was happy. (Feeling like a bit of a pedantic prick, but happy).

When I got it home and let all the air out and fully compressed it, there was 10mm of stanchion exposed. ie 140mm travel. They told me that the fork was a 150mm fork that had been amended to give 140mm travel. It was a fork left over from the previous year's model bike that was 140mm. Not so pedantic after all, but definitely unhappy!

They sorted it without quibble. They remembered that I had made a point about it so they didn't really have a leg to stand on.

 

[Dan63]

sorry didnt see that in the original post.

Wouldnt worry about it, I've had forks that when measured like that have been 5mm short of what they're supposed to be, doesnt seem to affect them.

However , if youre really bothered It could be that there is a bit too much air pressure trapped in the negative air chamber of the air spring, try slowly (really slowly) letting air out while simultaneously pulling the lowers down, once all air is is released from positive and negative chambers, re inflate to desired pressure, stopping at 10 psi increments to cycle the fork through the first 10-20 mm travel very slowly to let the air chambers equalise. There's a bit of a knack to this .

FYI this slowly inflate and cycle that people keep touting is nonsense.

Rear shocks and forks have equalisation ports. It doesn't matter how fast or slow you inflate the system it will equalise as soon as it is cycled.

 

[Mteam]

FYI this slowly inflate and cycle that people keep touting is nonsense.

Rear shocks and forks have equalisation ports. It doesn't matter how fast or slow you inflate the system it will equalise as soon as it is cycled.

Not true all the time, well it is true that they have self equalisation ports, they just don't work very well and need the slow inflate and cycle method to ensure they're equalised a lot of the time, especially if you have totally deflated fthe neg chamber. just last week both my fox 36 and float x2 would not self equalise after a service unless you go in stages and slowly cycle, same went for my lyrik and bos kirk on my previous bike

 

[Sidepod]

To further complicate things, all of the online stuff suggests the port is just slightly into the compression stroke yet the Fox video shows it at full extension meaning to equalise you would need to fully extend the fork.

Chatting with a pro suggested the problem is likely to be grease build up in the air chamber blocking the passage and trapping air in the neg chamber. I’ll strip it and find out.

 

[Sidepod]

UPDATE - So just about to strip the forks, gave them another tug. Foot firmly on the front wheel and a good old sustained tug upwards on the bars. Imagine my surprise, a nice audible hiss and the forks jumped up. It now sits up and measures 185mm crown to seal.

The Fox video is bang on. Pos/neg equalisation port is at the top of the travel. Result.