While researching for available coil-overs for use at the track with an ITR, it seems that those with a separate adjuster ring for ride height and spring pre-load are well regarded. Models include Tein RE and Zeal B6. However these shocks are only provided with a single adjustment means for both bump and rebound changed simultaneously. While reviewing options from Truechoice for the track, they provide Koni's with independant bump and rebound adjustment, along with Koni's recommended procedure for track tuning of these adjustments. However I do not know how easy it is to access both the Koni adjusters. I was wondering what other shocks there are with independant adjustment that anyone has tried. I found Leda's which are available with external reservoirs for separate bump and rebound, but they are a little pricey. Moton too but way too expensive. One brand I found was
www.advance-design.com which seems to fit the requirement (sold by Ground Control I think), but I know nothing about these products.