aerobod - near CYYC

I think differential expansion of the hub and brake disk and possibly the use of the alloy cones on the wheel nuts. It is quite consistent and has always done it when the rear hubs and brakes get really hot. I find the loosening torque when the wheels cool down again is pretty close to 85Nm, if the hot tightening torque is kept at 75Nm.

The M12 studs should be safe to at least 120Nm without damage. I have found the rear wheel nuts loosen by about 30Nm on the track as the hubs heat up (no noticeable change to the fronts). I torque to 85Nm before a track day, then ensure they are at 75Nm when hot after coming off the track.

Re #8, my castor value should be ignored. I initially set it to a "medium" setting which was at 4.3 degrees, but was expecting high steering forces with the high camber and toe-out. After the steering forces were less than expected, I went to maximum castor (4 washers to push lower wishbone forward) and didn't remeasure. The castor is not dependent on ride height as KnifeySpoony mentioned, but is slightly dependent on rake (about 0.25 degree change for every 10mm change in rake).

Re #7, I was unsure about the Nankangs before I tried them on the recommendation of my tyre specialist over the R888Rs, having previously been using Hoosier slicks on the track and Bridgestone RE-71Rs on the road. Overall they suit the car very well, but I found I had to run a much higher (24 PSI hot) pressure than the 18 PSI hot I ran in the other tyres. I recently just fitted the 3rd set of fronts and I'm halfway through the 2nd set of rears, with probably 2/3 track and 1/3 road use of them. Synopsis of the Geo I use from the link is: Camber: -3.0 degrees front, -2.7 degrees rear Castor: 4.3 degrees Toe: 0.6 degrees total toe-out front, 0.5 degrees total toe-out rear - car is a lot more stable and much sharper turn-in than I would have thought with these moderately radical settings.

The bushes in my 2012 R400 A-frame are mixed - 12mm bore with M12 bolts on the front 2 bolts, 1/2" bore and 1/2" UNF bolt in the centre deDion bush.

I'm using Nankang AR-1 R-compound 13" tyres in 185/60-13 front and 235/45-13 rear sizes, together with the standard R400 Bilstein adjustable platform sport dampers and springs.

This is what I did with my R400D: /comment/2392485#comment-239248 I also recommend putting in a spherical bearing to replace the A-frame to deDion bush: /forum/finally-decided-put-spherical-bearing-dedion-frame-connection

The rear brakes are just inefficiently cooled compared with the fronts, transmitting the heat into the hub and wheel centre, even though they do less braking. The caliper is tucked up close to the rear basket and with 8x13 rear wheels gives little opportunity for much airflow for cooling. In contrast the front 6x13 wheels with the vented discs and AP calipers have a lot more airflow around them. The airflow difference is also exhibited by how quickly the front tyres cool compared with the rears if you are not continually pushing hard on the track (such as when under yellow flag), I always have to remember to not push too hard after the flag is cleared to avoid significant understeer until the front tyres are warm again.

Temperatures of over 100C for the diff under hard use (such as on track) are normal, so too hot to touch (likely 60C or higher) in lower stressed use is not unusual.

The rear ones will soften and fly off on the track, after I got black flagged when I first took the R400 to the track and was presented with a cap in the paddock by a marshall, I just removed them. I keep the fronts on as the air cooling is much better at keeping the brake and hub temperatures down, keeps grit away from the bearing seal a bit better.

MFU is the Multi-Function Unit containing relays that are not on the fuse panel, I'm not sure if all R400/420Rs have it, but the logic for engine start with a push button dash is controlled in that unit.

I don't have the 420R wiring diagram, but on the wiring diagram for the R400 the coil packs don't have a chassis ground as such, but a common negative that goes to the MFU. With or without power there may not be a direct path to chassis ground.

A sensor input problem (such as failed Lambda) will show up with Easimap logging, an electrical continuity problem will show up with an oscilloscope trace. It is difficult to home in on the definitive problem area without these diagnosis solutions in place. If you don't have an MBE cable to use Easimap, it is definitely a worthwhile investment. You can also get a USB 2-channel oscilloscope for about $60. Both can be hooked up to a Windows laptop.

The fact that the problem goes away when the engine is hot and under load may point more to a wiring or connector problem than a failed ECU driver. I had a similar intermittent problem on #1 cylinder caused by a faulty connector on the coil. A loupe was needed to see slight arcing on the connector contacts, but I used a cheap recording oscilloscope to see the voltage spikes on that cylinder differ from the other cylinders when the engine misfired. Vibration over time seemed to be the cause of connector failure in my case, I added some foam tape on the coil cover that contacts the connectors to hopefully alleviate the problem in the future.

One health check with the Duratec that could be worthwhile is checking the inlet valve spring tension vs the exhaust valves. As detailed in my engine failure thread (/comment/2421006#comment-2421006), all 8 of my inlet valve springs had suffered spring resonance fatigue failure with 30,000 road and 10,000 track kilometres. This condition looks to be a spring and inlet valve weight mismatch problem for cars that had the same cam and valve springs as my 2012 R400 Duratec. Removing the cam cover and pressing down on the bucket tappets should reveal whether the springs are 5mm or so shorter than they should be due to most of the spring sitting on the broken 1.25 turns of the bottom part of the coil. I didn't notice any engine performance change due to the springs still holding the valves closed, until one spring suffered a second break and the valve dropped in to the cylinder, but small particles of steel from the spring breaks could show up on an oil drain magnetic plug.

Also best to use a helmet rated for role cage impact, padded or not. SA2020 or equivalent rating,

The main thing in a redesign is to get rid of the awful collet, it is totally unnecessary if the proper tolerances are used on the clevis and the damper bush is just fitted and tightened with a standard nut and bolt. All the excess hoop stress in the clevis holes that the tapered collet introduces is then alleviated and the clevis hole is smaller too, giving it extra strength over the current design.

The choice overall for a budget welder will be determined by whether you will do much aluminium welding or not, Jonathan. I have an older Clarke 150EN welder that at 150A is just about the minimum current for welding up to 6mm aluminium. If you do plan to weld both steel and aluminium, you will also want a welder that allows a Teflon liner to be easily swapped, as using the same liner for both metals will end up with the small particles the wire feed rollers generates when feeding the wire contaminating the weld of the opposite metal. Also when welding aluminium you usually want to use tips that are listed as 0.1mm larger than the specified wire size and feed the wire a bit faster than you would think, to minimise tip jams and welding them shut. Forehand welding should also be used, as backhand will just blow holes in the weld.

I have the flywheel with the machined out back sections, Neil. Seems to run true, but I will see when they machine it. No final spec for the UK parts from Raceline yet, talked to Chris a week ago and just need to finaIise the cam to finalise the order, he was going to get back to me with the RLD270M cam spec to see if was close to the D-TEC45, no word yet.

Got the pistons in today and gave them to the machine shop for checking dimensions before they commence the re-bore. Also now have the connecting rods, too: The piston pockets seem to be 3.5mm below the crown of the flat-topped standard pistons, so should be OK for the highest lift cams available for the Duratec. In terms of machining the flywheel, does anyone have the specs for minimum machining depth, this is the standard R400/420R machined steel lightweight flywheel fitted by Caterham with the AP clutch? I'm hoping to get away with about 0.1mm of a skim if possible, but the machine shop wants to know the maximum depth they can go to.

Thanks Neil, I will contact them if the Wossner purchase doesn't work out. I've taken to calling suppliers before doing online orders for speciality parts these days due to the variability of stock since Covid, as opposed to the order just going into a blackhole waiting state.

That's why I picked Vivid initially due to "In Stock" for the P4-DU88-P7 pistons, but it was not to be, unfortunately. I've dealt with them before and had good customer service (buying a 480BHP supercharger kit for my old Z4M from them).

The problem seems to be the oversized pistons are not commonly stocked, Vivid Racing went to Supertech and got the info direct from them, can't find any other supplier online that isn't showing "special order" for them. I actually prefer the Wossner pistons if I can get them, just didn't seem easy to get last week from suppliers, until I talked to the right person at Wossner US today. Probably about 25% more for the Wossner vs Supertech ones, but time is more important for me to get some momentum in the build, now that the Maxspeeding rods are ordered.

Hi Neil, I will see what pocket size the pistons have and what Chris can offer as a Raceline package that is similar to the D-TEC45 (also being cognizant of the limitations of the stock Ford valve size and strength with a higher lift cam). Tried to order the Supertech pistons today, but I'm being told over 2 months lead time to get a set. Looks like I may be able to get Wossner K9220D050 88.0mm pistons with a 12.5:1 compression ratio that seem to be in stock in Ohio, so could be here in a week.