It is possible to convert some Rockshox solo air forks to dual air. There are some caveats though.
You need to be prepared to suffer at least a 10mm reduction in travel and the fork needs to have a dual air spring available for it.
Here's an example of a conversion that works:
Rockshox SID 120mm solo air to 110mm dual air
What you need:
- SID 120mm solo air fork;
- air spring from SID 120mm dual air fork
;
- 10mm all travel spacer.
The conversion process is fairly straight forward:
- remove the solo air spring from the fork;
- add the 10mm all travel spacer under the air piston head of the 120mm dual air spring
- fit dual air spring (with 10mm all travel spacer) to fork.
After this process you will have a dual air 110mm SID fork.
Why the 10mm travel reduction?
The 10mm travel reduction is required so that the seal head on the resultant dual air fork sits above the internal groove in the solo air stanchion that does the pressure equalization between the positive and negative air chambers. By spacing the air piston seal head above that groove, you have a fork that is not back to having positive and negative chambers that do not self equalize.
Why convert to dual air?
Solo air forces you to have the same pressure in the positive and negative air chambers. For a number of riders having positive and negative pressures doesn't work out. This is particularly the case where you are very light (eg <40kg) or heavy (>100kg). At these ends of the spectrum, the extra tunability of having separately adjustable positive and negative pressures is very helpful in getting the most out of your suspension.
What other forks will this work with?
This mod will work with solo air forks which are the same as a previous year's dual air fork. This means, it'll work with the following solo air Rockshox forks:
- SID 120mm (eg. SIDB) - get this: part number 11.4015.546.040 - Spring assembly (Dual air) and air top Cap Kit (120mm max travel) - 2012 Reba/SIDB 26" or 11.4015.546.050 Spring assembly (Dual air) and air top Cap Kit (110mm max travel) - 2012 Reba/SIDB 29". (Note: all SIDA 100mm forks are dual air, even for 2014).
- Reba: get this: part number 11.4015.546.040 - Spring assembly (Dual air) and air top Cap Kit (120mm max travel) - 2012 Reba/SIDB 26" or 11.4015.546.050 Spring assembly (Dual air) and air top Cap Kit (110mm max travel) - 2012 Reba/SIDB 29"; and
- Revelation: get this: part number 11.4015.394.000 "air Spring assembly, Dual air - 2010-2011 Revelation".