After our last outing at Blyton Park we had a little debrief session and discussed how we felt (individual subjective analysis) the car behaved in all areas. The main area of discussion focused around our distinct lack of front end grip. Rob being the Vehicle dynamics expert was burdened with the task of coming up with a solid working theory as to why we were experiencing this distinct lack of front grip. His conclusion was a variety of reasons; tyre pressures, spring rates and most importantly he noticed that our lower wishbones were at a rather steep inclination, due to us lowering the car around 40mm. After some rough geometric analysis it became apparent that this causes the instant roll centre (IRS) to be underground somewhere creating a large moment between the CofG and the IRS. Inevitably, this causes the body to roll which is bad.
So to remedy this we did some research and discovered there is two ways in which this is achievable. One way is to buy/make some lower ball joint extenders. This seemed like the easiest option (assuming we could source some from somewhere) although we were slightly concerned with the sheer magnitude of the loads going through that bearing.
The second option was to modify the wishbone pick-up points on the front subframe. You’re probably thinking to yourself that this is a much more risky venture as suspension geometry is critical and structural integrity may be an issue. We decided after careful consideration to modify the pick-up points on the subframe.
So, as you may have seen from the last update, we have already removed the subframe ready for the modification. After some discussion on the best way to approach the situation we decided to use some rectangular section steel cut into the original mounts. This allowed for maximum strength and seemed the neatest solution to the problem. Once we had sourced the material we thought it prudent to use some CAD to reduce our material waste – by that we mean Cardboard Aided Design.
Many hours later, after making 4 extension towers from the rectangular steel and aligning them using multiple straight edges and other techniques, we started welding. Once this was complete, we decided to offer it back up to the car just to re-assure ourselves we’d done a good job and that it would slip back in nicely. We found we had a slight collision issue; one of the towers tried to occupy the same space as the gearbox end casing. We applied some lateral thinking and some effort and managed to, fingers crossed, fix the issue. If you’re interested in our lateral thinking, get in touch with us; otherwise just consider what we did magic.
Once we had finished with our lateral thinking, a coat of paint or 3 was applied and we considered that a job well done!
Another part of our escapades involved remedying the steering issues we had on our last outing. We had suspicions that our inner track rod bearings were buggered, due to a clunking noise when rapid steering input is applied. We had also noticed that the steering felt a bit vague and that the steering wheel would, on hard corners, apply an offset to its self of about 10 degrees and would rectify its self after a few corners. At the end of the day we noticed that the steering rack appeared to be a bit lose on the subframe mounts.
On closer inspection (which is easy when the subframe is on the floor), we noticed that all 4 bolts that clamp the rack to the subframe were lose – a bit concerning to say the least. So after stripping it all down, found that all 4 bolts were different (not sure if that is right?) and one of them had pulled the threads out of the aluminium tower. We rectified this by drilling the threaded hole out to 12mm from M10, re-tapping it and inserting some M12 studding with appropriate thread locking compound. Job’s a good ‘un… it’s now much stronger than the standard clamping method.
We must also mention the rubber bushing; we found that one of them was folded back on its self, most likely due to being installed by a less than competent chappy. So, to fix the problem we decided we need a new one so went to our local main dealer as google couldn’t offer any alternatives. We walked out of the main dealer like John Wayne….. not because we wanted to be in a western but because we felt as though Francois Hollande had bummed us!! £21 for a small sleeve of rubber…. unbelievable.
Anyway, we can now finally get the subframe back in place and feel very confident that we have fixed some of the issues that plagued us at the previous test. Onwards and upwards as they say! Donington entry has been submitted now too….so let’s hope the car doesn’t blow itself up at Castle Combe.