What does it do?
The Rockshox SID Debonair upgrade only involves an upgrade to the air shaft seal head. It does not increase (or change) the size of the negative air piston chamber like the Pike Debonair upgrade.
How do you install it?
- let all of the air out of the fork;
- drop the lowers;
- remove the air spring by removing the retaining circlip;
- replace the stuff pictured in black above with the new seal head;
How's it ride?
To be brutally honest, I can't tell the difference. I'm not sure what problem Rockshox were trying to solve with this "upgrade". The Debonair seal head has the same type of seals (eg. one inner and one outer oring), so its not like they improved sealing or reduced friction through the seals. It also doesn't do anything for the relative volumes of the positive and negative air chambers. The only major design difference is that the Debonair seal head has a bushing at the bottom. This "may" reduce stiction.
Why only "may" reduce stiction?
The old system had a lower plastic bush with a much larger hole than the shaft diameter. There was sufficient clearance that the air shaft may never have rubbed on that plastic bush. Potentially, fork flex and/or bowing of the air shaft could result in rubbing, but I've never seen any rub marks on the inside of the lower plastic bush so this is probably not occuring.
Accordingly, the new bushing may actually cause more friction / stiction than the old system.
Any weight difference?
Yes. The old plastic setup weighs 15g and the new Debonair seal head weighs 20g. So the Debonair upgrade will make your fork 5g heavier. Weight weenies take note.