We will soon be starting work on a new MotoIQ project car, we have obtained A Nissan S13 240SX hatchback with a totally stock SR20DET swap. This car is going to be built as a track day car that will be capable of recreational drifting as well as being good on the track. Eventually, the car is going to be used for Time Attack and possibly Grid Life GLTC road racing. Of course, handling is an important consideration for this car and it is going to have the somewhat difficult task of being able to both grip drive and drift. We have considerable experience with the Nissan S chassis and have a lot of knowledge on how to get them to work. When we were searching for a suspension we checked out the offerings from GKTeck and we were literally amazed and what they make for the S Chassis, their offerings, in our opinion, are the most advanced off-the-shelf parts on the market. Every aspect of the S-Chassis suspension that we considered and would have to engineer and fabricate just a few years ago is now available for purchase from GKTech!
Our experience with the S Chassis dates back to Dai Yoshihara’s super-winning S13. Dai won the 2011 Formula Drift Championship in it. We sort of created an S Chassis resurgence because previously the S Chassis was considered to be obsolete and not competitive. To make the car work, we did a lot of standard mods but also did a lot of custom secret things. Well, now all of our secrets and more can simply be purchased from GKTech with no fabrication or messing around at all!
A car’s knuckles or uprights and their geometry play a big part in how a car handles. Here is where road racing and drift cars differ. Road racing cars need Ackerman in their front steering geometry and typically you want a gradually rising Ackerman curve that is slightly less than the geometric true Ackerman. For drifting, you want a digressive Ackerman curve. This tends to understeer in grip driving. GKTech makes 3 different knuckles. A grip driving one, a drift/grip one, and a super angle drift only one. The main differences between the 3 are the Akerman curve, the steering ratio, and the trail. For our car, we got the drift/grip part. It has road racing-like steering geometry but with provisions for more angle than stock and a faster steering ratio.
The ball joint location has been lowered by 50mm for roll center correction when lowered and the tie rod has 64mm of bump steer correction. You can have 2″ of drop in the knuckle while maintaining OEM geometry for roll center and bump steer!
7 comments
looks fanstastic! I always wondered about these arms and knuckles. Thank you for the in-depth review
“ Road racing cars need Ackerman in their front steering geometry and typically you want a gradually rising Ackerman curve that is slightly less than the geometric true Ackerman. For drifting, you want a digressive Ackerman curve. This tends to understeer in grip driving. GKTech makes 3 different knuckles. A grip driving one, a drift/grip one, and a super angle drift only one.”
^This really is ‘the secret’ to handling with rubber tires and their slip angles. In F1, I know that they even do an Anti-Ackerman setup!
https://www.f1technical.net/forum/viewtopic.php?t=8874
Until you understand these principles in theory and practice, you can’t really have a solid understanding of how to make a car handle.
It’s weird with open-wheel cars, We found that anti-Ackerman causes understeer in road racing in sedan-based cars.
I think it has everything to do with the tire. I am sure that F1 had to change up the anti-Ackerman when they switched to 18” wheel rims this year.
The ‘max lateral load’ (and associated ideal slip angles) for radial street tires is probably way different than the race rubber they run in F1. Also, downforce needs to be factored in.
My Holy Bible on tires is this book, if anyone that wants to race a car is serious about winning, or just being competitive, don’t get a HUGE REAR WING, please read the bleeping manual!
I ordered a copy and the author Paul Haney even signed it! What a guy! So happy for him to take my money!
https://www.standardsmedia.com/The-Racing-and-High-Performance-Tire-8627-book.html
I ordered the book!
they didn’t have it!
the book is out of print, considered a rare book and no one has it!