Slipping clutch

[CycleSi]

I recently (in July) had the clutch assembly replaced in my Caterham R400 with 6 speed box, with the following AP items which were supplied by a well respected Caterham expert. It is a 1.9 K-series engine producing approx. 217 bhp and 161 lb/ft torque The problem I am experiencing is the clutch is slipping in the higher gears (particularly in 4th & 5th) when doing track days (it seems fine when driven on the road). Initially we thought that oil was leaking from the gearbox and getting onto the clutch plate and causing the slippage but we removed the engine/gearbox assembly this week and found the clutch assembly to be dry with just some light spray/misting of oil in the bell housing so now we're not so sure this is the cause.

What concerns me is the AP plate is (according to their specifications) rated to 150 lb/ft and the cover to 100 lb/ft so I assume they are not up to the bhp/torque of my engine hence the slipping?

The only other thing we can think of is that pre-load on the clutch release bearing isn't sufficient enough?

Plate
https://www.apracing.com/product_details/performan...

Cover
https://www.apracing.com/product_details/performan...

I have just emailed AP Racing to see what they think. Any thoughts/comments/help would be gratefully received.

[DCL]

I would have thought that it was adequate for the job. If it is slipping from being fitted then I suspect it didn't bed in properly in the early stages. If the flywheel and pressure plate were not new, then it may take time to achieve the full torque spec. Even if they were new (or just the pressure plate) it can take a little while. I'd live with it a little longer and see what happens.

[CycleSi]

As I say, I have only noticed it on track days (particularly the club's Brands GP day).

Both the plate and the cover were brand new, but the flywheel (a lightened TTV Racing) has been on for a couple of years and appeared absolutely fine.

The fact that my engine makes around 161 lb/ft and the cover is 'only' rated to 100 lb/ft then to me that is the obvious problem here, but I'm just not knowledgeable enough to be sure.

[downsman]

I'm no expert but the preload on the release bearing shouldn't be relevant, as it is only there to keep the bearing in light contact.

If the manufacturers rate the units lower than your engine output, and the problem is on track when you are likely to be using all 161lb/ft, it would seem that they just aren't up to the job. Just buy a higher rated clutch and cover and reinstall it.

It's up to you whether you take it up with the expert who recommended the parts.

[CycleSi]

I am inclined to agree with you. The problem is knowing which uprated clutch to get. I have emailed AP Racing to ask them but I suspect they might come back to me and suggest a paddle clutch.

Helix has also been mentioned as a possible solution too. Any part numbers would be very helpful if anybody knows of any.

Thanks.

[BertBert]

With a cover rated at 100whatsits and an engine putting out 161, it doesn't seem surprising if it slips. I am surprised though that ap produce a clutch cover that low rated!

[CycleSi]

UPDATE

it would appear the cause of my clutch issues were two fold.

Firstly, the AP Racing clutch assembly (in particular the cover) was not up to the torque of my 1.9 engine so I'm replacing it with an uprated Helix model.

Secondly, the AP plate has partially disintegrated. I went to see Phil at Road & Race yesterday and he has confirmed the whole lot was about to implode and that would have also contributed to the slipping that I was experiencing.

A gearbox refresh and new Helix assembly should remedy everything. Fingers crossed.

Thank you for all of your input/help.

[downsman]

Good to hear you've got to the bottom of it. It's too much aggro dropping the engine back in, to do it until you are 100% sure you have the solution. Phil is very helpful