As for suspension travel im not too sure yet, im considering building towers in the rear and running coilover struts, with tender springs added to help keep the inner wheel on the ground. A big problem at the moment is, with 0° camber on the rear as the inner wheel lifts contact on the outer is reduced. At higher speeds when the rear outer tyre reaches its limit it breaks loose quite violently. Last weekend I spun out again doing about 100km/h and ended up in the grass about 20 meters off the track. At lower speeds its handleable when the rear lets go, but at higher speeds its a handful. I need camber or I need to try and keep the rear axle parallel to the ground somehow without increasing understeer, so softer springs are out of the question, but additional tender springs on a strut may be the solution…
AWD should have a big rear sway bar. Std on the Liberty is 19mm rear. I’ve gone to 22mm with three points of adjustment which on “hard” gives 167% increase in torsional rigidity. Can’t remember what the spring rates are but a tad over 400lb front and a tad under 400lb rear. Dampers bump and rebound are near full hard rear and full soft front. Front camber is neg 4 and rear is neg 1.5. Toe is 1mm out. Castor about 6deg pos. The big rear sway bar transformed the car. However, not sure with your type of viscous center as to when it is kicking in. Sway bar will keep the rear on the ground.
You are not going to get any camber on the back without some radical mods. I know some guys bend the axle a 1/4 of a degree and let the bearing cope. The right way is to run a universal in the end of the housing a use wedges as shims to get camber. I doubt though that this is your problem.
If the car has limited travel I would consider a longer panhard rod before going to a watts linkage and ensure as parallel as possible. Do the maths and figure the longest length you could fit and calc the arc. Let say the rod can be 1200 long and you have 50mm of travel up (or down), then based on the bit of maths I’ve just done the lateral movement is only 1.75mm at worst (in bump or drop). Have your read any Carrol Smith (helped develop the Ford GT40, worked with F1 teams including Ferrari and was the brains behind all Allan Moffet’s Australian success) and the Tune, Race or Engineer to Win Books? He was of the opinion that the extra weight and complexity of a Watts Linkage may not be worth it if the Panhard was long enough. Two heim joints in a Panhard compared to five in the Watts. Just a thought. I’ll think about it some more. Really busy this week getting the Subaru ready for the CAMS challenge hillclimb Sat and then a six hour MTB race Sunday.
Mick, is the rear diff LSD?
My heim joints arrived today, and I got everything mocked up for the watts link. Its going to be quite light and compact, the pivot will be mounted low on the diff housing so the roll centre will be lower than it was with the panhard bar. @Mr_Gormsby ive thought about what you’ve said, but the panhard bar is only like 80cm, I think with the arc we are talking cm rather than mm in regards to how much the axle shifts side to side. Not to mention the play in the bushes under load. With the watts link there will be basically no axle shift, and the roll centre will also be lowered. Regarding weight there is also not much of an increase, everything will be very compact, I would be surprised if unsprung mass was increased by even half a kilo. The pivot will be run on bronze bushes, and the bars are 22x1.5mm tube with M10 heim joints.
The usually excellent work we see from you Mick. Well done.
Yesterday was the last race of the season. I met up with two fellow club members, Jorgen with his VW Sirocco, and Kai with his Opel Astra, both very nice cars.
We set off on the two and a half hour drive to Melle, but not on the Autobahn, no, we decided to take the Landstraße, the back roads. As we headed south the landscape began to change, no longer the boring flatness of the northwest but rather winding roads through hills surrounded by colourful autumn trees. It was a fantastic drive. I tried my best to keep up with them, but with the car full of tyres and tools, along with the extra passenger, I found myself left behind more than once.
Over the last few weeks I have been messing around with the car, I made a new flange for the headers so the exhaust is tip top and widened the car 50mm front and rear. Some test drives confirmed everything was in order, only it wasn’t. During the drive yesterday the engine light came on again, again the o2 sensor was causing a fault… I erase the code and press on. The rest of the drive was problem free, then we arrived at the airstrip in Melle.
The final round for the NWD Cup, Niedersachsen Cup and Weser EMS Cup, also near the border with Nordrhein Westphalen where the season has already ended, we were greeted by over a hundred competitors from all over Germany. We arrived at lunch time, the youngsters had finished and the group 2a was in action. We signed up and went through scrutineering, watched some racing then came group 3, so I was up.
With so many competitors the racing continued through the lunch break and we didn’t get a chance to walk the tracks. At this event we had 2 tracks, you drive the first track then line up for the second directly aftwards, so warm up, warm up, first run, first run, second run, second run. I thought it was a fantastic system.
The warmup round on the first track went well, some pylons were hit but otherwise smooth and fast. The second track warmup was a catastrophe, I entered the hairpin from the wrong side, completely missed a door and came in way to hot for the last 90° turn and ended up on the grass. No problem, just the warmup run. The following runs were all very clean and fast, except for one in which 3 pylons were hit at the exit when I came in a little bit sideways The wider wheelbase helped the car alot, the rear axle seemed to handle better and oversteer was less extreme and more predictable. A fantastic day.
In my group there were 13 competitors, I finished 10th (could have been 5th if not for the 3 pylons) and 8th. The fiat retired after the first warmup run due to technical problems. The first 4 places were occupied by two teams, both very professional.
After calculating the points it looks like the championship will end with the 2 Polo drivers in 1st and Second, followed by myself in 3rd. Very happy to have come this far in my first year, driving in the highest class!
3rd overall fantastic. Well done.
I managed fourth outright at my last event in the old wagon. One test was complex and I had taken my hardtail race MTB. I rode the course as fast as I could on the bicycle easily twenty times. Nearly everyone joked with me about how embarrassing it would be if I got a wrong direction. Anyway all the top guys stuffed up which drastically elevated my position. Last khanacross for me is in two weeks, new AR1 Nangkangs. We are not getting fields of a hundred, more like 40-60.
The results are up. I misunderstood the scoring system, I was under the impression the best 70% of the races was added to the final score. But it looks like only the best 70% of the races are used for the final score. I think my German has some room for improvement 5th in class, still not too bad!
NWD-Cup 2018.pdf3a (1).pdf (35.4 KB)