JAL73

Im about to go on a road trip hence my renewed focus on NVH... I was talking to Ollie at R&R Transmission about NVH and he said that the relationship between incline of the engine and the incline of the diff can stress the UJs on the propshaft and cause NVH to be transmitted from the engine to the diff. That sounds plausible but no idea how to test whether my car suffers from that particular ailment. Vibrating elements touching the transmission tunnel also seem highly plausible but not sure if this can be avoided with Duratec/ Mazda applicaiton given the tunnel width.

I have been in other cars which seem quieter and less vibration than mine, so I know something on mine can be fettled to improve it. I love thrashing the pants off it on track but I also find unnecessary NVH irritating and dont mind the challenge of minimising it.

In my continuing quest to reduce NVH in my car I had a look at the placement of the gearbox in the transmission tunnel and noticed an appendage on the LHS of the gearbox touching some lining material on the inside of the tranmission tunnel walls (see pic) and wondered if this might be the a big contributor to the NVH I feel and hear. I have a 420 with Duratec engine mated to Mazda box and BMW diff. I've had vibration analysis carried out on the car with sensors attached along engine & drive train and been told theres no obvious rotational imbalances detected and been advised the engine mounts are not great at isolation, however I'm wondering if my gearbox seating/ placement might also be compounding the problem. Space is incredibly tight in the transmision tunnel so wondered if others have managed to fit their gearbox without any part of it touching the inner tunnel walls. Also wondeirng what the circled appendage on the Mazda box is for and whether it can be removed and blanked off to give a bit more room to avoid touching the walls. Im assuming it serves an important function so unlikely to give me the breathing space Im looking for!

Thanks that’s helpful info. Maybe I’m being too resistant to the change over… Did you feel the need to re-do your geometry and corner weighting when switching from ZZS to R888Rs given the difference in dimensions etc? Is the R888R softer, harder or very similar compound to the trusty ZZS.

Just reviving this thread - as more and more people will have switched from from Avon ZZS to Toyo R888R on 13" wheels by now, how have you found the switch? Any pros or cons? Do the R888R have a stiffer sidewall than ZZS? Has any one had issues with the taller sidewalls on the fronts rubbing the cycle wings?

I've had a look on the Protech website but when you search for their Caterham offerings it says 'no products listed' Which particular damper and spring combination did you go for? Do they have fitting/ geo setup facilities there also or supply only? Their product offering seems dramatically cheaper in price than the more well known brands offered by the well respected Meteor motorsport. Just wondering if anyone has any experience comparing Protechs vs Nitrons, Core or Penske - is it a question of you get what you pay for or are these Protechs really just better value for money. My question is in the context of ride comfort on the road, not shaving seconds off laptimes.

the other issue i have, which i think is also suspension related, is when you go over bigger bumps/ potholes you sometime get a horrible (bang/ crash) noise coming from rear of the car but whenever i look under the car i cant see/feel anything loose. I thought it sounded like it was coming from DeDion tube but HWM who service the car assure me its not that, so maybe its the dampers. Curious as to whether others out there have experienced similar and managed to trace the source of it?

i took off my rear ARB and it did seem to improve things a bit. i only did the rear cos thats where poor road surfaces seem present the problems but i havent tried the front ARB - would removing the front improve ride comfort much? Has anyone tracked a 420R with all ARBs removed? I reinstalled my rear ARB cos thought it would understeer a lot on track without it but i really dont know what im doing. Also, for those that have removed all ARBs - did you then do a flat floor chasis set up after on standard Bilsteins and get nice results?

I’m already on 13” Apollos with Avon ZZS tyres….! What is it about the standard 420R suspension that people think is inferior to the various available upgrades out there for compliance on the road? Is it the Bilstein compression or rebound is too slow or the springs are too stiff? Apologies if that’s an over simplistic question but i was just wondering if its the damper or the spring that contributes most to peoples dissatisfaction with the standard Bilstein components.

I am considering upgrading the Bilsteins on my 2020 420R SV in search of refining the way my car handles bumps and poor road surfaces. My car can be quite crashy over bad surfaces and prone to the rear skipping over bumps at high speed, Im wondering whether this is just something inherent in such a light weight car or whether its possible to achieve a really significant improvement in ride quality with better suspension components and a proper set up. It seems the price of suspension upgrades plus geo/flat floor starts around £2k and goes up to about £8k which is a serious chunk of money. Curious to know what other owners have upgraded to and whether they think its worth the money? Appreciate its a quite a subjective topic. Please note im more interested in improving compliancy and road manners rather than shaving seconds off lap times!

I had this issue and was told that my reluctor ring on the RHS drive shaft had slipped out of position. I have a 2020 420R SV. Next time it was in the garage they moved the reluctor ring back into position and secured it and Ive not experienced any issues with my speedo sticking since that fix.

Has anyone ever used these chaps in Bicester for vibration issues? https://vibrationfree.co.uk/our-services/motor-sport/ Looks like they specialise in A-Z of resolving engine vibration issues and also seem to have developed the "sterling damper" a torsional vibration absorber for cranks. Didnt know such things existed...

It used to have lumpy idle, kangaroo and serially fouled its plugs which was down to corrupted map and faulty TPS but this has been resolved perfectly.

yes its seems to be engine speed dependent, the vibration seems to diminish above 2-3k rpm i think but not really been able to measure this scientifically. the car has a perfectly smooth idle around 950rpm and drives beautifully, its just the low rpm vibration that ive noticed

I have read Aerobods very impressive account of his engine teardown and rebuild and feel somewhat blinded with science. I didnt want to detract from the purity of his thread with an amateur question but I noticed the incredible lengths he went to, to ensure all the engine components were equally weighted alongside the balancing of crankshaft and flywheel. I assume the reward for a meticulously balanced engine like that is engine vibration is minimised across the rev range. The reason I ask is because i have always wondered what causes noticeable vibration on my car at idle and other engine speed dependent NVH at other parts of the rev range. For example, at idle if you hold the headlight bowls you can see and feel them vibrating. To this end, I was wondering whether other owners out there have ever spent time and money rebalancing their engines in search of minimising engine related vibration. Ive no idea if this sort of thing is prohibitively expensive or who the specialists out there are. My car is a 2020 420R on 5k miles so I assume most of the vibration im witnessing might be a balancing issue rather than failed or worn engine mounts. I have managed to erradicate pretty much every rattle and squeak on my car (there were many...) and so now im interested to see if vibration is something that can be fettled out to some extent. I realise its a Caterham and "they all do that sir" but there is usally a rational engineering explanation for why they do it and what can be done to minimise it! I've learned to accept the CWP noise from the diff however, so not sure that will ever be as quiet as I'd like it to be...

Let’s say the front KNs are 0.5kg heavier each corner and rears maybe 0.7kg (?) heavier each corner, would you notice that difference in unsprung weight in terms of handling/ performance? I have a set of Apollos on ZZS already for road biased use and was thinking of getting a set of KNs with ZZR equivalent rubber on them for summer track use, but sounds like the Apollo is a better performance wheel given its lower mass, just not sure how much difference you’d notice

I need a second set of wheels so swapping doesnt help me unfort. Do you know if there is any weight difference between the Apollos and the KN 8 spoke wheels?

Looking for a staggered set of these 6x13 and 8x13 wheels

My 420R SV was recently in with Caterham for a few tweaks. I had been complaining of a banging sound when going over very bumpy roads as if the car was bottoming out maybe. Caterham told me my radius arms had been set to ‘S’ and should be set to ‘R’ and this would likely stop the noises i was complaining about. I’ve since had the car back and I think moving it from S to R has improved but not eradicated the horrible noise over potholes/ big undulations. Ive also taken it out on track since getting it back. I must say I can’t really say that I have noticed any obvious difference in road or track handling since they adjusted from S to R position. It’s not obvious to me from looking at the geometry which difference in handling you should expect from switching between the two positions.

Thats very neat. I ended up buying a 14" longacre mirror with standard mounting brackets but prefer the recessed look of yours. I also have the same trackday rollcage. What is the box above the mirror with the red R on it?

👍Cheers! Will send over a message now

Don’t want the hole for two reasons 1. I’m personally not a fan of the external box looks, prefer cleaner look for bonnet but each to their own 2. Noise - i understand that ITBs are noisier than single plenum, and even noisier if airbox is outside. I would be really unhappy if I spent a chunk of money on performance upgrades and then but then got black flagged for noise on track where you really want to unleash it all. Most tracks seem to be 101-105db static noise limit and I think I’m currently around 97/98db static on a factory standard single plenum.

They suggested 45mm but that might be because I said I didn’t want to cut a hole in the bonnet (my car is SV body). Do you know what bhp or torque diffs 48mm offer over 45mm on a like for like comparison?

I am interested in upgrading my 420R to Jenveys and heard Nothampton Motorsport were one of the best in the business at doing this upgrade. Incl VAT they quoted me £2,042 in parts and 11 hours labour at £1,176 to install and map on their rolling road. It looks like 6.5hours of installation work and 4.5hours of mapping/ callibraiton. They recommended 45mm ITBs for under bonnet fitment. They quoted an extra £350ish for cutting a hole in bonnet to accomodate an extrnal air box. I guess an external box allows for colder/denser air intake and maybe to allow for bigger trumpets, but not sure how much extra performance this would give? My car currently starts and idles perfectly, has great low revs/ low throttle manners and I cant really say it lacks power, however I love the noise of ITB cars make at high rpm! As its a non-trivial amount of money I'd love to experience Jenveys before I buy. So if anyone in Surrey/ London area would offer a demo I''d be eternally grateful. Here's the breakdown of my quote (under bonnet mount) for those interested.

Sorry Oli, these sold within 10 minutes of posting. I obviously advertised them too cheap!