Fin

I finally got round to replacing the tatty old BMW wheels with some shiny forged magnesium wheels. They weigh less than 5 kg per wheel and look super. Unfortunately, they're not BMW fitment, so I have to use an adaptor which pushes the wheel out by an additional 35 mm and adds about 1 kg / corner back on - but the weight saving is still around 3 kg per corner which is well worth having. New brackets for the cycle wings will be needed at the front to keep the cycle wings central over the wheels - at the moment the wheels stick out quite a bit which looks a bit silly.

Last Saturday I managed another track outing, happily with no engine or other failures, bringing the failure-rate down to one engine per track day. Hopefully I can take that as a sign that engine #3 is a good 'un.

Waiting for the green light. Note appropriate race number.

The track outing took the form of a sprint - a very tight twisty track, doing timed runs against the clock, one car at a time.

Engine not exploding. Result.

Note cycle wings not centred over front wheels.

The car performed very well, although it became clear that the springs were a bit on the soft side. The extra track width doesn't help as this means the wheels have more leverage to compress the springs. So after a bit of educated guesswork, I had a guess at a new spring rate for the front and stuck some stiffer springs on, which has greatly improved things. The dampers can be wound back a bit as they're no longer needed to try and stiffen the ride, so they are able to control the springs better which gives a less chattery ride. Having stiffer springs at the front has also improved the front-back grip balance so the car can now be made to understeer, rather than going straight to oversteer when feeding in the power. Less entertaining but probably faster. Turn-in feels a bit sharper which is an improvement.

However, this has highlighted the fact that the rears are now more than a bit soft... so they are next on the list. Turn-in at the moment is a bit of a two-stage process - the front turns in quite neatly, and then shortly afterwards the back settles itself into position with a general lack of urgency. As a starting point I may try putting the old front springs on the back and see how that feels.

I suspect an ARB at the front will improve matters further, perhaps a winter project for after the rear spring rates are sorted.

Simon having a go. Despite being used to very forgiving 4wd rally cars, he very kindly neither crashed nor humiliated me on time (he was slower in the morning, quicker in the afternoon).

Note excessive body roll on the old springs.

Now that my major concerns with the car are worrying about suspension setup and adjusting spring rates, it seems that mechanical reliability and basic build stuff is more or less there. Not that there isn't lots I want to do still (front anti-roll bar, make a nicer looking dash, redo some untidy bits of vinyl wrap, data logger, etc, etc), but this is all nice-to-have stuff.

So this is probably a good point to put the build blog to bed. It's been a good experience. Lots of things I'd do differently next time, but that's to be expected really. Looking forward to lots more track days in it, and fewer exploding engines.