sprocket

We also discussed the need to actively manage regen braking to avoid vehicle instability in slippery conditions.

Hi, Same problem with a 2012 140hp Supersport. I was advised by someone who'd built a Blackbird powered 7 which had a ridiculously light throttle spring to increase the spring tension. I added another coil spring to the top of the throttle pedal and bingo, it reduced the kangarooing quite a bit. It's still there which you have to manage but it's much improved.

I want to change from Tillets to leather seats in my S3. Anyone interested in a swap?

Thanks everyone for your interest. Mine is now sold.

Hi Orange, I'm not sure what constitutes old or new buckle but the one photographed is the one I have for sale. Cheers

Hi nickh7, Sorry for tardy response. Are you still interested? BTW, I haven't received an email so am not sure what's happened there. Thanks for your interest.

Luke Racing System. Left hand side, black belts, red buckle. Supplied by Caterham for 2012 S3 but unused and still boxed with all fixings and fitting instruction. £75 plus delivery cost.

Thanks all for your input. I now understand that this requires a full manual set up for the timing so will consider whether to do this myself during the winter or get someone else to do it. Cheers

Thanks for the recommendation for PP but I've changed a couple on regular tin tops and fancy the challenge of doing my own if I can.

Hi all, I'm about to change the cam belt on a 1.6L Sigma in a 140 Supersport and have heard that the standard Ford camshaft locking tools are not suitable due to different timing.Can anyone who's done this job offer any words of wisdom? Many thanks

Job done. Popping the seal out with the chisel end of a crowbar as suggested by Mike Cocker was a doddle. Tapping the new one in was straight forward and I used a large diameter drift so the the hammer was never close to the seal itself. The hard part was undoing the diff housing filler plug which Caterham had kindly tightened to about 6,000,000 Nm. Well, nearly that number. Went to the club monthly meeting last night and not a drop of oil on the garage floor today. Thanks for your advise.

Thanks for the advice team. I'll swallow a brave pill and give it a go tomorrow. Cheers.

Image of offending seal.

Hi, has anyone out there changed a driveshaft seal on a BMW LSD as fitted to a 2012 Supersport? When I searched on line the side seal housing appeared to be bolted on but my seal just seems to be pushed into the machined diff housing. I could do with anyone's prior knowledge before I attack mine. Thanks,

Hi Mucus72. Sorry to hear that you also suffer the dreaded CLUNK. There are many potential sources of backlash (free play) within any driveline but a Caterham with BMW LSD seems to have excessive backlash that results in an audible clunk either when you pull away or most noticeably during torque reversal (power on/off/on). There is potentially noise due to the limited slip mechanism but this shouldn’t be noticeable in low torque, straight line conditions. I believe that in my car the biggest culprit is the half shaft spline that plugs into the diff which has at least 60% more backlash than the BMW equivalent stub shaft. I therefore get a huge mechanical clunk as the free play is taken up during torque reversal. My guess is that your car has the same problem. The diff is very firmly mounted in a Seven so any noise is transmitted into the chassis and in the case of a Supersport with no carpets, straight into my ear. I’ve no idea what to do about this other than trying to change to BMW type Rzeppa half shaft joints so that I could use the BMW stub shafts but this would not be simple. Maybe the answer is to install very loud headphones connected to the exhaust and just enjoy the drive. :-) Hope this makes sense

If anyone is interested, I measured the backlash across the LSD comparing the BMW stub shafts and the tripod joints supplied by Caterham. Locking the outputs, the pinion rotation was - BMW 11.4 degrees and the tripods 18.3 degrees. ie 60% more. This is probably significant in the overall perception of torque reversal clunk and contributes to the kangarooing at low spreed. C'est la vie.

Aha! We may have a bit of an answer here and Rattie wins the cigar but maybe not why he thinks. I decided to take the diff out and strip it down to investigate what is going on. During the strip process having removed the halfshafts, I plugged in the original BMW stub shafts that were supplied with the diff to keep it clean during the build. Just out of interest I half heartedly checked what backlash I could detect across the diff and WOW! Where's it all gone? It now felt like the pinion might be close to the crown wheel after all. A quick change back to the tripod half shafts and guess what? clunk rattle clunk. When I'd checked the lash in the halfshafts before I was only going along the length of each individual shaft.I now believe that the problem is that the end spline of the inboard tripod joint into the diff is undersize and contributes most of the free play in the whole driveline system. This is why I believed that the backlash existed within the diff. As Rattie says above, changing the inboard joint to the BMW Rzeppa one could eliminate this source of backlash. Does anyone have any experience of such a conversion? Thanks to all who have contributed so far.

Hi Rattie, I finally got round to checking the drivesahft lash as you suggested. I didn't measure it but it is tiny compared to that in the diff, Thanks for your input.

"3mm past the start of the first zero" is similar to mine depending how vigorously I take up the lash. I'm not sure if this is a good or bad result. If they are all like this, there's nothing wrong with mine but then I can't improve it. Doh!. Let's see what others are like. Thanks.

Thanks slap_ed, Do you mean 3mm just passed the start of the first zero or passed the entire zero? Thanks for your input.

Hi The ASH, Thinking about it, BMW dealers probably haven't got a clue as they'll just replace the whole unit if it had a problem. Thanks for your measurement. Staring at mid A, mine goes to 2/3 through the O of AVON but as the tyres are different sizes this may not be a good comparison. However, comparing your 30mm at 240mm radius gives a direct angular comparison to mine which is 90mm at 240mm radius. Ouch! There will be differences in driveshaft and gearbox lash plus a minor difference due to final drive ratio but it starts to help me understand if I have a problem. Hopefully other LSD owners will chip in with some figures. Many thanks for your input. I'm looking forward to Scott's feedback when he can. Cheers

Thanks for your response 'The Ash'. I was hoping to get other owners figures for comparison before taking the diff out and stripping it. You are right that BMW would be best placed to specify the actual crown wheel to pinion backlash figure. I may even take the actual diff with me so that they can identify the type and advise any other problems .... if they'll talk to a mere Caterham owner

I appreciate that there has been significant discussion regarding the BMW LSD but I’m afraid I can’t find a suitable answer so here we go again. Ignoring the horrendous whines, clunks and embarrassing kangaroo characteristics, (they all do that sir!) my 2012 differential having only travelled 9000 miles in a 140 Supersport, seems to have significantly more backlash than when it fell into existence. Before I take it apart to investigate what’s going on, I’d appreciate any wise words from the world of Blatchat. I have measured the free rotation of the input flange against the handbrake and have approximately 23 degrees (20mm around the flange circumference). I know there is a small amount of free play in the driveshafts but this is minimal. 23 degrees in the diff seems colossal. I have also tried to assess the free play by jacking up one wheel and rotating it against the gearbox in 4th gear (straight through). I marked the movement relative to “CR500” on the tyre. I would attach a photo but ain't clever enough. It goes from the start of the 'C' to nearly halfway through the first '0'. My first question is whether anyone knows the specified backlash for this diff. Secondly, I’d really appreciate it if you also have this diff and can measure what backlash you have. I measured a friend’s and his circumferential measurement on the diff flange was 16mm which means mine is 25% greater. It would be good to get a number of measurements for comparison. Thanks for your help.

On Mankee's advice I spoke to those wonderfully helpful people at Bailey Morris who offered to do a balance and dimensional check on the shaft for me. As I already had the engine and gearbox out for another job, it would be easy to pull the prop out forwards and drop it into their factory as I was passing nearby the next day......... Wrong! Ok, all you clever people know that the prop can only come out backwards due to the rear flange diameter being larger than the miniscule tunnel. So the diff has to come out first. Oh well, C'est la Vie! Or should that be C'est la Caterham! Aha, if the diff's out then maybe Steve at SP Components in Redditch should also get a call.Thanks to Mankee and 'Seven Wonders'.

To answer Mankee's question, it's a BMW diff complete with significant backlash clunk and horrendous gear whine. "They all do that sir!"