The Snetterton Jog

16/06/2012

OK, the formal results have arrived, and it seems my immediate reaction after the event (see previous post) was a little over-critical. I thought I had dropped to last place or nearly so, but in fact I only dropped back to the 19th place that I secured at Aintree. I know why though, and I've learnt something about Caterham driving.

Specifically, I've learnt that the suspension setup is very important. Let me tell you the whole embarrassing story that I've kept quiet so far.

It goes back all the way to Aintree, when another Academist mentioned that he had checked his car's ride height and found that it had dropped since being set up by Caterham. It seems that suspensions can sag slightly as they settle in - I decided to check mine, as the advantage of running slightly low is marginal, whereas the penalty (disqualification) is quite severe. As I was then slightly distracted by setting up a new business from scratch on the next working day after Aintree, it was not until after Curburough that I was able to try and check it properly. That then runs into the immediate problem that the relevant height is that of the second chassis bar from the front when I am sitting in the car. Sadly, my contortionist skills do not extend to measuring the height of a chassis bar at the front of the car while sitting in the driver's seat. So help is needed, and I sent No. 1 son scurrying to the front to check.

He reported that my specially-made 140mm-long stick didn't fit into the gap. Ooops. I decided to assume that a lot of sag had happened since Curburough.

Getting out and looking for myself, the stick fitted with ample room, and said son was a little vague about where he was measuring. Back in the car, though, and he still says it doesn't fit, almost. ::[sigh]::

So I went away to think about it, and thought up a way of rigging a rule along the side of the car and at the front suspension mounts to see how much the car drops when I get in. That suggested it drops about 10mm, with a possible error of 1 or 2mm. With me not in the car, there was a clearance of about 10mm, with a possible error of... 1 or 2mm. In other words, it could go either way. I decided I needed to raise the car.

There was just one snag. By now, it was the Wednesday before the race day. I estimated my chances at getting it booked in at approximately zero. So out came the axle stands and the spanners.

It's actually quite easy to adjust the suspension once the weight is off the wheels, you just need to rotate the collar at the bottom. After a little thought, I decided I needed to lengthen the springs to raise the car and so loosened the collars, keeping the same number of turns on either side and slightly less at the back as the damper units are more upright. Dropping the car again, the rear seemed to have dropped - odd. After lifting the car again, a little more adjustment seemed to fix it.

So off I went to Snetterton. On the first practice, I span out of the hairpin - a new experience. Spinning off is not new, but spinning on the first practice when I'm usually cautiously feeling my way around the circuit very definitely is.

So the second practice was of necessity a more gentle run although oddly slidy, as if there was no grip - and achieved a corresponding time. It was better than the first run, but that is not surprising as it didn't include reverse gear at any point. I do find that the runs which involve reverse gear tend to have poor times...

After the first timed run, I was scrutineered thoroughly (seemingly at random) and told that my ride height was marginal, and that I should adjust it. Now, that seemed odd; I had allowed a margin and, if anything, was worried that I had put too much of a margin in!

So, off to the Caterham support truck, who are all busy changing someone's differential in a hurry and rather unavailable! So I borrowed a jack and put a few more turns on at the front, and rushed back to the scrutineering bay. To be told that the car is now even lower!

Back to the paddock, then. This time, I managed to grab a Caterham engineer for long enough to talk me through adjusting it, and discovered two things that would have been useful to have known a week earlier.

First, you need to clamp the end of the damper unit at the bottom to stop it turning while you adjust the spring seat.

Second, to raise the car, you *tighten* the spring - thus increasing its tension and extending the end of the damper unit further out, pushing the car up.

Doh!

So I quickly lifted the front of the car, took off the turns I had just added at the front, and a few more, rushed back to scrutineering, and was told I was ok. Phew, no disqualification on the horizon. Back to the paddock, and (as I feared) my turn was coming around again and it was time to suit up and strap in.

Now, of course, I had spent the entire time since the last run panicking about my ride height and hunting for a way to adjust it. I had done precisely no thinking about how the run went, or where I could find more time. I had precisely no discussions with others about how they were finding the course and what their opinions were. I was flustered, my mind was elsewhere, and as I crept up the start line two things struck me:

(a) as I hadn't clamped the bottom of the damper when I adjusted the car at home, there was no promise that I had made the same adjustment on both sides, and

(b) the rear could be, well, just about anywhere by now.

In other words, my previously carefully balanced car was now in a state of suspension setup that could best be described as "random". At least that explained why the second practice was slidy and the first was spinny.

Add all that together and you get a second run that was not a great time (although faster than the first). What I could feel, though, was the complete inability of the car to get any power down until it was well out of the corners. Run 3 was a similar story; although I had calmed down, I just couldn't get the car to grip.

So, the lesson is that setup really is important. Don't muck about with it unless you know what you're doing, which - of course - you now all do.

Oh, and the car is booked into Dartford for flat flooring on Monday.


(A quick note re the photos - two are by a professional photographer, three are by a so-called amateur. See if you can guess which are which)

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