Nigel B

I thought this was an interesting video from Harry Metcalfe. It touches upon the subject of synthetic fuels towards the end.

I'd read somewhere that Porsche were looking into this, but I hadn't realised they'd made this much progress. It sounds like a very promising development.

I bought the smallest, cheapest Dremel a few years back. It was fine for a while, but then started to randomly cut out. Eventually it wouldn't work at all, so I (stupidly!) got the next model up, which again worked fine for a while, but has recently started conking out in the manner of the previous one. I don't think I'll be buying another...

‘You only need a LSD on the road if you’re driving like a lunatic’ is an opinion that crops up fairly frequently during discussions about various types of diff. Having covered a lot of road miles in 7s fitted with open, Quaife & plate type diffs, I have to disagree with that. For me, a LSD isn’t about doing doughnuts or about sliding around every corner with your hair (& rear tyres) on fire. It’s about increased predictability & that delicious sense of solid connection between throttle opening & the attitude of the car. Caterhams are all about responsiveness & that fine sense of precision & I think a well set up plate type LSD really adds to that sense of connection with the car. Don’t get me wrong, I don’t think a LSD is absolutely essential. I drove my first 7 with an open diff for over ten years & thoroughly enjoyed myself. After breaking a drive shaft (it had an Ital axle!), I decided to fit a Quaife as the general consensus seed to suggest it helped with the reliability of the Ital axle & I felt the Quaife diff was an improvement, with more grip in the wet & that increased sense of connection between the throttle opening & the car’s response. Moving onto a 420R with a Titan diff, that sense of being able to finely control the car’s attitude with a combination of steering & throttle took another leap forwards. The sense of connection between the throttle & the rear wheels was far more obvious than with the Quaife. In my opinion the ability to subtly & delicately point the nose with the throttle & feel precisely the point at which rear wheel grip fades greatly adds to the enjoyment of the car. Yes, maintenance is a factor that needs to be considered & plate diffs do require periodic rebuilds, but for me the rewards of a plate type LSD hugely outweigh those disadvantages.

Titan BMW LSD From my 2017 420R. Freshly rebuilt with sintered steel plates by Steve Perks of SP Components. Unused since the rebuild. £550 plus postage.

I don't think the AP Suretrack is a plate type LSD. If I recall correctly, it's a torque biasing diff similar to the Quaife ATB.

I think you did well to manage 20,000 miles Geoff. My Titan internals looked very similar after 6,500 miles. Only one of the springs was broken on mine, but otherwise your photos look very familiar!

Hi Peter, Well, amazingly the weather has been pretty good in Scotland recently, so I've been out & about quite a lot. The Tracsport is still quiet & unobtrusive. Knockhill was interesting, as the heavens opened half way through the afternoon! The car felt very sure footed though, even in those conditions & it was surprising how much right foot you could use coming out of the corners. It felt very confidence inspiring. I hope you're still enjoying yours & you're managing to get a few end of season blats in. Nigel.

The Quaife ATB cropped up in conversation with Steve Perks when I was last at his workshop. As he put it, ‘They ‘never wear out’ because they’re not actually doing anything’! Quaife try hard in their advertising to present the fact that their diff doesn’t lock as an advantage. It is in fact the diff’s primary disadvantage. If a wheel is in the air on a car fitted with a clutch plate type LSD it will rotate at the same speed as the wheel in contact with the tarmac. Hence, the car isn’t unsettled & there are no sudden shock loadings on the transmission when it touches down again. I’ve owned Caterhams with open, Quaife & Titan diffs. I have a Tracsport fitted to my 420R & wouldn’t contemplate going back. Worth every penny, in my opinion.

That was what I found. There was no preload left to measure!

Yes, you're right Peter. I had suspicions that something was amiss at the end of last year, as my car didn't feel as confidence inspiring as it had initially. Under power it felt a bit erratic. I was aware that the Titan didn't have a very good reputation for longevity, but I'd assumed, naively, that if the plates wore out it would simply act like an open diff. I didn't realise that was a sign that it was on the verge of catastrophic failure & was likely to break up & cause very expensive damage to the crown wheel and pinion!

I was talking to Steve Perks earlier in the week & he was of the opinion that there isn't any difference in longevity. He said the internal parts are the same in the BMW & the Ford versions & he rebuilds plenty of both types.

Prompted by this thread, I refitted my decat pipe yesterday after a couple of months running with the cat, as I hadn't got round to removing it again after the MOT. Strangely enough, the issue I had with a sudden step up in loudness at 3000-ish rpm has completely gone! I can't understand what has happened there. Perhaps it has mellowed with use? Odd.

Perhaps it's just me then? Strange. Peter, it must be the growl from your roller barrels, drowning out the exhaust noise!

Haha brilliant! I fitted a decat pipe to my 420R last year. I prefer the more strident raspiness without the cat, but I did notice there's a quite distinct step up in loudness at about 3000rpm that doesn't seem to be there with the cat fitted. With the cat, the increase in loudness happens steadily as the revs climb. Has anyone else noticed that? I still have the cat fitted at the moment, following the MOT. I really should get round to taking it off again...

I drove Caterham’s 420R demonstrator at Crawley last year, before buying my car & it had the most horrific sounding diff I’ve ever experienced. I mentioned it to the sales guy (before we’d even left the car park) & he laughed it off, saying it was also Caterham’s press car & therefore got a lot of abuse, doing 0-60 runs. The 420R I bought, sounded much better by comparison, for a while at least! Perhaps it’s Caterham’s sales technique, take the customers out in a duff one first?

The carbon plate Titan in my 2017 420R had lost all preload at 6500 miles. As I tend to do a fair few road miles & didn’t fancy the prospect of having to get it rebuilt every other year, I decided to replace the Titan with a Tracsport. I had a Quaife ATB in my previous 7 & while I appreciate there are advantages to them, I prefer the feel of a clutch plate diff. People’s experiences of the Tracsport seem to be very positive & they reputedly last a lot longer between rebuilds than the Titan, so a Tracsport seemed to be the best solution for me. Having looked at the components of my stripped down Titan, side by side with the equivalent Tracsport parts at Steve Perks workshop, the Tracsport certainly looks far more robust. I’ve covered a couple of hundred road miles since fitting it & the car has far better traction, feels more predictable & is considerably quieter. The off throttle whine & chatter from the Titan completely dominated the driving experience. While I appreciate plate diffs by their very nature require periodic servicing, the need for a rebuild every 6500 miles doesn’t suit my needs.

Well that’s interesting, I thought it was just me with this problem! My previous 7 didn’t have lowered floors & I had no problem getting the harnesses tight enough. However, in my new car with lowered floors, the harnesses aren’t quite tight enough, even when they’re fully tightened up. (I bought the car second hand, I wouldn’t personally have specified lowered floors. They compromise ground clearance too.) I do have s type seats, however. Strangely, I do have two holes a few centimetres further back for the lower harness straps to mount to, but only one of them is threaded. I’ve raised the drivers seat by about an inch, using Tillett seat washers, which has improved things quite a bit, though the harnesses still aren’t QUITE as tight as I’d like. Another thing you might want to consider is moving the pedals further forwards, so that you’re sliding the seat further forwards. I guess it depends on where your pedals are mounted at the moment & how close you’re sitting to the steering wheel, but you may be able to take out the slack that way.

/sites/default/files/images/users/1318/7667026D-77F6-4DCD-B806-071DDE15F6B7.jpeg I fitted mine this morning & went for a (gentle-ish!) blat this afternoon. I haven't checked to see if it's collected anything unpleasant yet though...

Thanks for your explanation of the diff removal procedure Peter. It doesn't sound as involved as I thought it might. In the meantime, I've ordered a magnetic fill plug!

Oh dear, it looks like I have a winter project! I used to have a live axle 7 & I took the diff out of that on a number of occasions, but I have no experience with the dedion rear end. Interesting times ahead...

A ha! Thanks Scott, that's very interesting! I must confess, I was under the impression that the SPC LSD was only available for the Sierra diff too. I'm pleased that you finally got it sorted. It sounds like it's quite an improvement! My 420R has just passed the 10,000 mile mark & the Titan diff is definitely noisier than it was when I bought the car last year (at 4500 miles). Not much in the way of 'clunking', but there's definitely more whine & chatter when you lift off the throttle. Jacking it up and rotating the wheels in neutral, the opposite wheel does turn in the opposite direction to the wheel that's being rotated, which may suggest it isn't working as it should, although to me it still FEELS like a LSD. I think I'll keep my eye on it for the moment, but if it gets any worse, I'll certainly be giving Steve a call! Thanks again Scott & enjoy your new diff!

Thanks Scott. That looks like a very prudent upgrade. What did you decide to do with your diff? Did you stick with the Titan? I was following your thread with interest.

I just dab a bit of touch up paint on them, with no preparation. It seems to do the trick & I've never had any problems.

I used to have a 2002 1.8 8 valve Vauxhall Caterham. For many years I had no problems with emissions, the garage I used passed it each year with no comment about the emissions. I moved to Scotland 7 years ago & the first time I took the car for an MOT the garage failed it because the emissions were ‘way too high’. It turned out the previous garage had been turning a blind eye to the emissions! From that point on I had to have the carburettors de-tuned before the MOT & then re-adjusted back to the normal settings afterwards. I don’t think any 8 valve Vauxhall cars had a catalytic converter & unfortunately I think the visual smoke test only applies to pre 96 cars (If I’m remembering correctly). I would agree with Rick. I think your best approach would be to find a sympathetic MOT garage, probably one that’s used to dealing with classic cars & understands carbs. Good luck! I hope you manage to get it sorted. Nigel.