Before and after, McKee style…
So just how much time do you gain, going from knackered old road tyres to new semi-slicks? Quite a bit, actually! Despite a messy lap, I was over half a second faster in a back-to-back test, and absolute potential felt more like a full second over the 70-second lap.
Given that these Nankang NS-2Rs were very cheap, a hard-wearing compound and a bit narrower than the Kumho KU31s that came off, I was impressed with that. I can’t think of many other £240 changes you could make that would gain you a second per minute, not unless you were correcting really fundamental issues with the car. It’s not all about the outright pace, either – a track-oriented semi-slick will generate less heat because the tread blocks move around less, allowing you to do longer sessions and giving a far longer lifespan. In almost all cases, the investment pays you back in durability as well as performance.
In untimed practice in the morning the car felt far better, with sharper turn-in and considerably more overall grip. These tyres do need a little heat, and I had some understeer and a bit of a slippy feeling until they warmed up. What was most telling was bolting the Kumhos back on having been running the NS-2Rs all morning – I immediately found myself sliding around on exit and slightly outbraking myself. The Kumhos have been a very good tyre, but the NS-2Rs showed them up good and proper, and they only seemed to get better the more I drove them.
In reality, I probably didn’t have them properly scrubbed in, nor did I have the correct pressures or the right setup to take advantage of them. All part of the learning experience.
There’s always a bit of time to play silly buggers, too. Though one thing that felt sorely lacking by the end of this event was a limited-slip diff.. It had been evident in low-speed corners before, but Curborough is made exclusively of low-speed corners and the increased lateral load transfer on the NS-2Rs made the problem much more noticeable. It was well captured from trackside!
This kind of “one tyre fire” is deeply undesirable, so I set about searching for a solution. There are many ways to go about this, as the E36 was fitted with LSDs from the factory in various forms. My car, and most 328is, was built with a 2.93 ratio open differential in the 188mm “medium” case. An early 328i Sport (one without traction control, or ASC) has a 2.93 LSD in the same casing, and this is a direct swap. They’re also quite rare, and original Sports are getting very sought after now, so it’s not that common to find these diffs for sale. The next best option is a diff from a 3.0 M3 (not an Evo), which is a 3.15 LSD in a medium case. The driveshaft output flanges are different, but you can swap these for the ones on your original diff easily enough. The 8% shorter ratio is a useful performance boost for a track car, too. You can fit the 3.23 large-case diff from a 3.2 M3 if you really want to, but you’ll need the entire subframe, propshaft and halfshafts to suit, and unless you’re producing an awful lot of power it’s not really necessary.
As ever, there were a few more events to get through before any money would be spent…