KnifeySpoony

According to Mazda - either GL4 or GL5 fluids are specified. https://www.mazdausa.com/siteassets/pdf/owners-optimized/2000/mx5-miata/2000-mx-5-miata-owners-manual.pdf

No need to suck out - there's a drain plug on the bottom. Most of the noise you're hearing is the diff, not the trans, so fluid won't change anything there. One of the local spec miata gurus here in California who has rebuilt countless MX5 transmissions swears by Swepco 201 for syncro life, so that's what I'm using. It's a dino oil so needs more frequent changes presumably. I'm ok with that.

Keep in mind those dyno pics are from US owners - in the US, dyno sheets are pretty much always given with uncorrected WHP/WTQ numbers. I notice UK dyno shops tend to show corrected numbers, from my time here.

here's a dyno for a 420: https://usa7s.net/ips/uploads/monthly_2022_01/9312106_orig.jpg.d307494d9b8b2fc6372da4a66729ba26.jpg And a 420 on RBTB: https://usa7s.net/ips/uploads/monthly_2022_01/image.png.aeaa158f334d5025484fda86e9a30a68.png (tiny image but you can make out the numbers) Can't find any 360 dynos

All the new motorcycle communicator sets allow this. I used to use Sena, but recently changed to the top line Cardo units and have been pretty happy with performance.

I have a Spa digital gauge - It runs at a rock solid 92C when underway. In traffic/idling, the fan comes on at 98C. Based on the numbers you guys are seeing, I wonder if my gauge reads low, or the OEM gauge reads high.

re:#23 - I could revert, but I was getting very uneven tire wear on ZZS. I did the ear swap when swapping to ZZR, figuring the wear would be even worse. The car felt fine on 1.5rear but i would be giving up something like 40% of potential tire life I feel. re: #24- I don't think that standard radius arms would change anything, as the interference I am getting is with the forward link, which is essentially in the same position as the radius arm would be. re: #25 - thanks for the info. I would just run without handbrake.

The problem arose after changing my DeDion ears from 1.5 to 2.0 deg. This apparently brought the calipers in closer to the linkage. Before the upgrade there was no contact. I'm not sure how/why Caterham sells the 2.0deg plates if they cause this issue, but I guess Caterham gonna Caterham. related thread: /forum/techtalk/rear-brake-caliper-contacting-radius-armwatts-link

My initial interest (pre-build even) was to improve braking performance. Then, after upgrading rear pads I was content. Now that I'm having the clearance issue, I'm considering the upgrade again, as apparently that would eliminate the issue as well.

The caliper is a CP5119 with 44.5mm pistons (unless the Caterham piston spec is something different somehow). The standard Sierra rear is a 42.8mm piston, so minimal increase in size. The rotor does go from 232mm to 254mm, so there is some additional torque there. I'm kinda surprised it needs a prop valve tbh. https://caterhamparts.co.uk/15252-thickbox_default/brake-caliper-rear-race-10-lh.jpg https://apracing.com/race-car/brake-calipers/formula-car-range/2-piston-fia-f4-cp5119

10" vented discs. Which is the same as the factory option for uprated front 4 pot brakes. But it uses a 2 piston (fixed) caliper.

Yes, the whole assembly lateral to the DeDion tube changes with this setup. I just didn't realize that the track changed so much. I already get some tire rubbing on my rear wings, so I'm not sure how things will all fit if that track width change is indeed a thing.

Hmm interesting that it increases the rear track by so much. I wonder if that would affect handling balance enough to require change in other setup.

I guess CC refers to them as "uprated" brakes. https://caterhamparts.co.uk/calipers-pads-discs/2976-rear-brake-upgrade-kit-race-only-no-handbrake.html?search_query=brake+pad&results=251

Really, nobody?

I used sikaflex 221 on my recent build, applied as instructed in the current build guide. No issues with multiple track days with Vmax of 124mph.

My car is mostly a track car, I really only drive it to/from the track. I had considered this upgrade for maximum performance during my 420R build last year, but decided to see how the stock setup was. I found it a little over-braked in the front, but upgrading the rear pads to DS3000 has pushed the bias rearward enough that I am happy with the braking performance. However given my recent issues with interference between my rear calipers and watts linkage arms (/forum/techtalk/rear-brake-caliper-contacting-radius-armwatts-link), I am thinking about this upgrade yet again. Presumably the lower profile rear calipers won't have any interference issues. I'm OK with the handbrake delete (I'm in the US and in my state the car will never be inspected again). This setup seems to need a proportioning valve, although my calculations of brake bias don't seem to suggest the bias moves all that far rearward compared to the standard setup. I'm wondering if anyone has done this upgrade, or driven one of the R300/420R race cars with this setup and can comment on performance. I have never plumbed brake lines, and I would have to get the appropriated line flaring tools etc, but it seems not too difficult to learn. Also I would need to decide on a cockpit-mounted prop valve vs one in the engine bay (much easier to install). Wondering if the easy adjustability is really necessary, as I won't racing in the race.

Definitely check the lambda and TPS. From my understanding lambda sensor failure is more rare, but it's easy to check. My 420R is on roller barrels, so it simply won't run without the TPS (different mapping strategy), but my TPS recently started failing after about 3000mi. Replaced and all is well again.

I checked and there's maybe 4mm of clearance between the caliper and watts arm at ride height. There a little bulge on the inside of the caliper that appears to be making contact. I've read that the Sierra calipers modified by Caterham to fit our application. I wonder if this is the interference that is corrected. That also makes me worry that it would be impossible to remove more metal from the caliper safely, otherwise wouldn't Caterham have removed more?

Ah... hadn't thought of that. I recently changed out the standard 1.5deg ear for a 2.0 ear. That would certainly account for it. I'd have to take out the damper to run the suspension through its travel to really assess static clearance. I know that there is a lot of side/side flex in the rear end under load. Given that it just seems to be grazing the watts arm, I guess it's safe to continue running like this, but I will consider a spacer under the dedion ear if need be. I trashed a set of wheel bearings disassembling the rear end to swap out the dedion ears, so I'm not super excited to go back again right away, as I'l probably have to replace them again. I'm in US and shipping from Caterham is $$$.

I have a 420R with watts linkage and standard rear calipers. I noticed that there are witness marks on the forward watts link from the rear caliper on both sides. They appear to be relatively light scratches, not big gouges or dents, so it seems like the contact is light. Wondering if this is of any concern, or a case of TADTS.

With my setup (raceline sump), there's probably about a liter that drains from the finger filter hole.

I'm not sure about draining the sump (my 420R sump is a little different), but most of the oil is in the tank. You will need to drain it - you can use the drain plug at the bottom, but most people don't use it as it is prone to stripping, as it's in soft aluminum. Many people use a fluid extractor to suck the fluid out of the tank.

TBH I don't think we have enough info to really diagnose the problem. Is the understeer during corner entry, at steady state, or on exit? Damping can make a difference on transitions for sure (ie more of a factor on entry/exit), but certainly the relative roll stiffness front to rear will be the primary determinant of handling balance. Hence I would look at spring rates and ARB. And also agree about tire temps - if you're not even getting heat in the tire than all bets are off regarding suspension.