The last year or so, I have been feeling pretty beat up at the end of a few 20-25 min sessions in my SR4. I always get a lot of steering kickback in corners and the ride on the straights has always feel bumpy/harsh. I was getting to the point of considering selling my beloved SR4 and looking at a GT4 Clubsport or something similar with power steering. I used to track a GT4 and sometimes a GT3 but wanted a purpose built track car for safety and overall ease of working on it.
These laps here will give you an idea of what I'm talking about:
I had been using Hoosier take-offs (mostly almost new scrubs) from SCCA Formula Enterprise and chalked most of the crap ride up to these tires.
So last fall, I splurged and bought some brand new Hankook F4 slicks -- about the same overall size as the Hoosier FE tires.
Disappointingly, the kickback and ride was basically the same. Made me think something was wrong somewhere in the suspension. All uprights, bushings and link ends were replaced when I bought the car a few years ago but I triple checked everything -- it all seems solid and tight.
So, thinking it must be my setup, I decided to rent a new-ish SR1 to compare against. The original plan was to take my SR4 down to the VIR Club this past weekend and rent a gen 2 SR1 from Kaizen Motorsports in the AM then run my car in the afternoon. Unfortunately, MotoAmerica was on the north course and lodging on-site and places nearby was all booked or 3x normal prices. So, I decided to pull our camper down and drive the rental all day (Saturday).
On the first out lap, I could tell an immediately difference. The SR1 was MUCH easier to drive. Much less kickback, smoother ride overall. While I could tell that the rental car didn't quite have as much power at the top end (my 1300 was recently freshened by Carpenter Racing along with their special head porting) and didn't have as much aero (I have the rear diffuser that came with the SR4), it felt much more planted in the corners and felt like it had more mechanical grip. Which it shouldn't have, because the rental runs on the Hankook tarmac/rally treaded tires (the rental car tires were two years old!) vs the slicks that I run on.
SOOOOO, I have come to the conclusion that my shocks (the original AVOs) are probably shot. And that's putting it mildly. My car came with zero documentation and was obviously not cared for by a Radical shop in a long time, so I would bet that the shocks have never been rebuilt nor updated.
Do you think I'm on the right track in that lots of steering kickback in corners and a generally crappy ride in the straights would point to bad shocks?
It should be noted that I do my own alignments (strings and camber gauges) and was pretty happy with the overall geometry, but the rental SR1 had a much smoother handling feel to it.
Thanks all.
Forgot to mention... I ran four very hard 25 - 35 min sessions on VIR South. I didn't have any of the sore forearms that I normally get after two - three sessions in my SR4.
Given that caster isn't really adjustable in our cars, I'm really thinking all the kickback is from the lack of damping.
If you are comfortable with your alignment settings I agree with you that the shocks are definitely the next place to look. There was a post a year or so ago where one of the Forum members dynoed their older AVO’s and said they were very inconsistent so he changed to another shock. I think it was either Grahamd or Neil??
G'day John,
I'm interested that you made no mention of spring rates. I guess you have considered whether you might be running springs that are too stiff?
I watched the video and the 'kickback' doesn't look bad - I definitely get more than that in my RSX.
Do you have a seat insert? I'm wondering if your having to hold onto the steering wheel extra tight to stop your body from moving in the seat? Your leather steering wheel also look smooth/slippery compared to an alcantara covered wheel. Did the other car you drove have a tighter seat or an alcantara wheel??
In terms of shocks - I agree that you should get these dyno'ed, or alternatively borrow another set from a car that doesn't have the same issues your dealing with and try those on track.
Quick update...
Am ordering new shocks (standard AVOs) and springs. Also getting new Wilwood calipers and pads and will be updated my rotors. Calipers, pads and rotors are still from when I bought the car a few years ago. Brake feel is terrible compared to the SR1 I drove.
I'll probably start a thread on updates for my SR4 in case it's useful for others.
@rjbender, my seat is fitted decently, not too much movement. I'm going to redo the bead seat when I get the car updated again.
Chances are good that the spring rate is high. I'll have to check when I'm with the car again.
