Fork Oil, the air gap, and changing it?

The Todd

The Todd

It's 'The Todd'
I know that all forks have a 'air gap height' to be refilled to.

I've also seen measure what's coming out if each, and as long as it's about the same, put that amount back in.

What is you put a little more in? Stiffer overall?

A little less in? travels easier/less stiff?

My forks have all the Ohlins internals and have been 'rebuilt before also. I'm at work and can't look at the sticker.
I thnk it said TRS?

Anyone play with their 'air gap"? TIA
 
When you have the proper springs in and you are pushing the limits. You use oil level to fine tune the stroke . If you are bottoming out add oil , if you are not using the whole stroke take some oil out. You want to use the full travel of your forks.
 
THIS^

is what I thought and looking for confirmation. Compression and rebound was set at the track and readjusted last season by Joe at TurnOne Racing.

When I put the band thingy and zip tie on the other one, after a good track session, it's all the way at the bottom.

I think I"ll try a few more cc's of fork oil when I drain and fill soon.
 
The Todd said:
THIS^

is what I thought and looking for confirmation. Compression and rebound was set at the track and readjusted last season by Joe at TurnOne Racing.

When I put the band thingy and zip tie on the other one, after a good track session, it's all the way at the bottom.

I think I"ll try a few more cc's of fork oil when I drain and fill soon.
Click to expand...
You can try adding about 5-10 cc to each leg without draining, to see how it responds without draining it.
 
Once a Wanker.. said:
You can try adding about 5-10 cc to each leg without draining, to see how it responds without draining it.
Click to expand...

Right.

One of my winter projects was to drain, measure, fill. I'll use the air gap measurement only if needed.
I can't really test it until my next TD at BackHawk Farms May 5th.

Overall my front end and suspension has been great!
 
The air gap acts much like a spring but is very progressive. It is most noticeable at the very bottom of the stroke. Not enough and you induce hydraulic lock possibilities. If your spring rate seems good but you are bottoming at places like T10 at Road Atlanta, increasing oil level slightly can keep you off the bump stop. Get your spring rate and preload right first.
 
RM Racing said:
The air gap acts much like a spring but is very progressive. It is most noticeable at the very bottom of the stroke. Not enough and you induce hydraulic lock possibilities. If your spring rate seems good but you are bottoming at places like T10 at Road Atlanta, increasing oil level slightly can keep you off the bump stop. Get your spring rate and preload right first.
Click to expand...
couldn't agree more...when i did the cheap option of going 20W fork oil(no spring change) max preload on a shitty sv650 (sorry clapped out), it made the bike bottom in a way i've never felt before with real, racing type, lightweight fork oil. What is it 5W? This was a grocery run bike btw not race

i may have added slightly more oil.(within range)
 
Not all suspension fluids 'W' numbers are directly correlated to other brands of fluids. There's a chart out there somewhere of testing comparisons for various brands of suspension fluids.
 
John Branch said:
When you have the proper springs in and you are pushing the limits. You use oil level to fine tune the stroke . If you are bottoming out add oil , if you are not using the whole stroke take some oil out. You want to use the full travel of your forks.
Click to expand...

No, there is no need to use the full stroke. What we want is faster lap times. And there’s nothing that makes using the full stroke equal a faster lap time. Some people like support of more oil. Some ppl like the linear feel of less oil. Neither should tune to use the full stroke.
 
The Todd said:
THIS^

is what I thought and looking for confirmation. Compression and rebound was set at the track and readjusted last season by Joe at TurnOne Racing.

When I put the band thingy and zip tie on the other one, after a good track session, it's all the way at the bottom.

I think I"ll try a few more cc's of fork oil when I drain and fill soon.
Click to expand...

If you regularly spend a lot of time around the track deep in the stroke or regularly hit bottom, more spring and/or more preload are probably needed. 10mm less air gap is a small change that won’t fix those things.

If your air gap is close to your max fork travel, you probably don’t have room to decrease the air gap. 120mm travel fork with a 110mm air gap usually means you don’t get to use the 120mm travel. That little air gap is not uncommon on OEM settings.
 
The Todd said:
Right.

One of my winter projects was to drain, measure, fill. I'll use the air gap measurement only if needed.
I can't really test it until my next TD at BackHawk Farms May 5th.

Overall my front end and suspension has been great!
Click to expand...

Volume is an inaccurate way of measuring fork oil. Air gap, however, is accurate and (more importantly) repeatable.
 
There's a lot to consider: rider preference, which fork kit you're using, what bike you're on. Some riders prefer the feeling of the fork bottoming out, some prefer to be high in the stroke. Some fork kits tend to work better when you use the full stroke, some fork kits tend to work better when you're using the top 1/3rd of the stroke. Track and track conditions will also effect the set up. What about the rear shock? What about geometry? Tires?

The OP said he has an Ohlins kit. I'd start with identifying which Ohlins kit he has (NIX, FKR, etc.). Then I would set up the oil level to the Ohlins spec and go from there. I'd also only use Ohlins oil. Their kits and spec info is all based on using their oil.
 
Timely discussion for today:

'Air gap' is the height in the equation of 'air volume.'

Pie x radius squared x 'air gap' = volume

Happy Pie Day!
3.1415926535897932384626433832795 02884197169399375105820974944592307 816406286208998628034825342117

@DDK732 this IS really all about set-up geometry.
 
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