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Thanks @JohnCh. Engine is out, one of the axis on the knuckle on the driveshaft is seized up so now I know where the vibration was coming from. I guess it wasn’t greased from the factory. Is it possible to replace the u joints with the driveshaft in the tunnel? I really don’t want to have to take the whole rear apart to get the shaft out 😭.

Thanks @MV8 and @IamScotticus. I,ve rotated it around and don’t see a grease zerk anywhere, but I’ll take another look when it comes out.

I’m in the process of taking the engine out and noticed a label on the prop shaft that says to “ensure the unit is fully lubricated with a lithium based grease before use”. I didn’t do that on the original install, did I screw up or is this just a cya? Does anyone know how to fill it up? All I see are some spring clips on each joint.

If it’s Motul 105778 that’s the LS version of 10577. 105778 is what Caterham racing people recommended at the time back in 2018 when I built my r20R and I haven’t had any chatter or other issues with it. Finding any Motul product is difficult for some reason right now. I’m also looking for it.

You know you want to do the brake upgrade 🙂.

If you go with the race rear brakes, I believe there’s no handbrake, does CA require one for road use?

Thanks @d15b7, would be good to see some more 420Rs out there sometime. I was guessing the cold pressures, the hot pressures were 21-22psi, maybe they should be higher, don’t know but I’ll experiment some next time. I read message boards online about this and there didn’t seem to be a solid consensus.

G forces are fun but not much use, there are too many variables like track temp, braking down or up a hill, camber. Momentum cars like ours the exit is more important than braking, figure out the perfect exit first, then work backwards.

Thanks @Croc, we were in Group 3 for sprints and V for Enduro. The Ginetta has a 1.6l engine, weighs about 1250’. The cockpit is very small, the driver had to take his helmet off first before getting out, but it’s a beauty.

After a rainy Thursday, the rest of the weekend turned sunny and mild at Road Atlanta and made for perfect racing conditions. My son David and 3 of his roommates came up from Auburn to help out. Friday Qualifying 1: Set the tires to 17psi. The track was still oily, it took 6 laps to warm the ZZRs up enough to get them switched on, finished P1 with a lap time of 1:38.965, but it looked like the tire pressures never got high enough. Saturday Qualifying 3: This was the money session, it was early morning, cold track, cold air, beautiful. Bumped the cold tires up to 18psi. Finished P2 with a 1:37.002 with a 1967 Ginetta G12 coming out of nowhere and killing it with a 1:35.7. It took 6 laps again to get the tires warmed up. Saturday Sprint Race 1: 360 Video here. Good start but briefly dropped to P3 before late braking at turn 1 and taking back P2. Just behind P4/5 got into each other at turn 1 and span out leaving the rest of the field behind to slow down, so by the time it got to turn 3 it was already just the 3 of us. The Ginetta was way too fast to bother with so it was between myself and the red Porsche #112 for the podium spots. Once again the tires were not very grippy cold and feathered the throttle in 5th gear from turn 3 all the way to 6. #112 passed me on the back straightway and I was very nervous braking in to 10a, so used engine braking a lot to slow down to make sure of tire damage. Things settled down then lap 6 the tires switched on and started reeling #112 in, eventually overtaking him coming out of 10b. The gap between us was 0.007 seconds at the line. Super fun race. Sunday BRM Endurance Race: This is a 1 hour race with a mandatory 5 minute pit stop which has to be taken before 40 minutes. The ZZRs were still in very good shape, Mintex rear pads still had 8mm left, we filled the tank to 15 gallons so we could pit early, though very heavy. Lined up 2nd row, the front cars (which were in a different class) took off and with a full tank could not keep up, barely running 1:39s, so settled into P3. We were hoping for an early double yellow so we could be one of the few with a large tank to pit, but it didn't happen. P1 and 2 pitted after lap 17 under green flag then with just minutes to go before the 40 minute limit was up the full course came out and we pitted right away. We only lost 1 lap during the 5 minute pit, so came out in P1. The race was then black flagged and finished a little early which is a shame not to enjoy the restart, but the boys were so happy to get the win. Sunday Sprint Race 2: The Ginetta was a scratch so this race was between me and the 112 car. We swapped for the lead half a dozen times before he had an engine issue and fell back to third place, a real shame as it was an exciting race. Fall Historics Wraps Up with Repeat and First Time Weekend Feature Race Winners at Michelin Raceway Road Atlanta – Historic Sportscar Racing (hsrrace.com) I have a set of A24s coming for the next race, hopefully they'll respond better for the sprint races. The Mintex pads are great for the rears, very little wear and balance is good. Road Atlanta curbs as very high and some have deep ribs, so it looks like I may have run over them too much and caused some drivetrain damage somewhere, but totally worth it!

I’m planning on seeing if we can get a track day for sevens to get together in the spring next year. Once the track day people release their schedules next month I’ll make a list of possible dates and locations.

Yes probably hopped over the curb at turn 3 at Road Atlanta a few too many times last weekend. I’ll add that to the list!

The left and right driveshafts look a bit eccentric... https://youtube.com/shorts/hZJro1IIAIU?feature=share https://youtube.com/shorts/B1a8R7ZMDuo?feature=share ...but maybe spinning at lower RPM compared to the center driveshaft it's not that important, dunno, maybe that's normal. Center looks ok at low speeds anyways, not sure if this is of any use... https://youtube.com/shorts/bpUyGbaYsuU?feature=share Time for a complete disassembly!

Thanks so much @MV8,I did indeed have speed dependent vibration at close to top speed (124mph+), it comes on suddenly then when releasing the throttle it went away suddenly too. Don’t know if the stress log the vibration is causing the oil to come out faster maybe, dunno. Is there anything to check while it’s all intact before taking it all apart?

I have some (dumb) questions about the propshaft/gearbox connection point...I remember when putting it together if there was oil in the gearbox it would pour out of the opening here the end of the prop shaft goes into. Why is the end of the gearbox open like that so oil can flow to the prop shaft? Is there any expected gearbox oil loss to the prop shaft? The reason I ask is I changed out the gearbox oil today and it seemed less full than it should have been and there are oil splatters on the universal joints of the prop shaft and at the back near the diff (the diff is fine), so it seems some oil was coming out somewhere. Thanks!

First time using a 360 camera, even installed it backwards (and also too lazy to figure out how to rotate the video). Pretty cool way to see the race though. Ended up P2 after the red Porsche's tires that overtook me on the first lap overheated. We finished 0.007 seconds apart on the line. You may have to watch it on the Youtube app to be able to rotate the video around. https://youtu.be/0fqBdbcvDXM

They sell the A64 compound only (they call it 8018 for some reason). But it looks like buying from the UK direct is the way to go now.

Thanks @Bartman, your recommendation is much appreciated - they have everything in stock, the tires are cheaper, shipping cost more, net cost is a wash but you can get Avons quickly.

What happened?

I used the ZZR A64 this last weekend at Road Atlanta, they were very good in the wet. In the dry it takes 4-6 laps to get them to a good working temp but they lasted all weekend without much wear.

If the rears are 450F and the fluid can take up to 300F it could be the combination of solid rotor and high friction pads aren’t going to work together without bubbling up the fluid in the caliper a little. As the rear pads wear there will be more fluid in the caliper to overheat, so it’s possible it gets worse over time.

I use Millers Oils Racing Brake Fluid 300. It hasn’t boiled at all in 4 years. It has a boiling point of 310C.

This thread inspired to get one - it’s really good for the price, it’s weather proof, elastic around the edges and has straps to keep it secure…

This place seems to have a lot of choices for Sevens.... CATERHAM CAR COVERS - Cars Covers

On race weekends after unloading the car I cover the car with a plastic tarp from Home Depot, which has a bunch of grommets which I use to tie down to the car. $14.48 . It is ugly though.