Remote servo ratio - for assisted clutch - experiences please

[mickeyw]

Since recently buying a 110 with three pedals I have been reminded how heavy the clutch can be. I really love driving my V8 90 with it's auto box, but I thought I'd look for another solution to deal with the heavy clutch on this one.

I have seen the Redbooster kit, but I'm not ready to throw that much £ at this project, even if it does look well engineered and tidy under the bonnet.

I have read a number of threads on the topic of servo assisted clutches, both on here and other car fora, and experiences certainly vary.

The Lockheed remote brake servos used on many older English cars are quite commonly available again through specialist spares companies . It seems that Minis used a 1.9:1 ratio servo, and other cars a 1.65:1 version. Note that these are all single circuit devices, so not much good for modern braking systems, but fine for a clutch circuit.

Trawling the auction site I discovered that these servos are recently available in 2.4:1 and 3:1 ratios.

While I am keen on the idea of a super light clutch pedal it is evident is that the greater the ratio, the larger the diameter, so packaging may be an issue.

So my questions to anyone that has fitted a clutch servo are this:

• What ratio servo did you use?
• How light did the pedal end up, (one finger light like the Redbooster claims)?

Other considerations:

LR clutch master cylinder is 3/4" bore. Most of these remote servos are 7/8" bore. I don't see an issue with this difference, as it won't change the volume of fluid moved.

I shall need a vacuum reservoir, as the manifold vacuum on the V8 may not be sufficient at tickover for multiple clutch actuations. There are plenty of these available second hand. Audis seem to use some tidy plastic multi sphere devices.

[pat_pending]

I fitted a servo to the clutch on my old Hybrid. Very easy to do and with really good results.

I used the servo for an MGB, I can't remember the ratio, I bought brand new.

The clutch was light without losing feel.

The servo needs to sit at the correct angle, which may make mounting awkward in a standard engine bay, you may need to get creative.

You also need to keep in mind they have an air inlet valve that will suck water in if the clutch is depressed when wading.

I modified mine with some plastic pipe and epoxy to take a pipe to the raised air intake with the other breathers.

I was running a 2.5 na diesel and just tee'd into the brake servo hose then a one way valve, no resevoir.

You could pump the clutch several times before it would start to loose vac', never a problem even in traffic.

[Tanuki]

You shouldn't need a separate tank: the big bit of a brake servo serves as a reservoir of manifold-derived "suck" and is enough for several brake-applications without the engine running, so the same should be true for your servo-assisted clutch.

[As an exercise - with the engine switched off, pump the brake pedal a few times and see how many pumps it takes before the pedal gets heavier: you should get a similar number of pumps-before-heavy from a servo-assisted clutch].

[mickeyw]

Yes the breather issue I am aware of. Apparently there is a remote breather cap available, but I've yet to find one.

Good point re stored vacuum volumes. It's easy to start without a reservoir and add one later if needed.

I'm pleased to hear of your success Pat. Is the angle setting to do with avoiding bleeding difficulties, or to compensate for acceleration forces?

[pat_pending]

Bleeding I think.

I'll see if I can find the paperwork that came with mine, (it was 20 years ago) and scan it.

[Phil Hancock]

My wife due to joint problems has had me fit a 1.9:1 Lockheed type servo on her 200Tdi D1, its fine and I would have preferred to fit a 3:1 but the garage advised against it saying that we would get clutch wear problems due to lack of feel. As her joint problems are only going to get worse we will end up with a 3:1 and if the clutch suffers then a Tdi 130 or 6 paddle clutch will cure it.

[pat_pending]

I found the general instructions that came with the servo, still not sure what ratio I used.

The pt no' for the alternative valve cap is 3887-266 it's a genuine ap-lockheed part.

[mickeyw]

Well that makes interesting reading. I had no idea of the mounting requirements.

I fitted a used servo (no idea of ratio) on my 88". IIRC I mounted the cylinder horizontal and the plastic valve at the top.

Also interesting to read that not all ratios used the same cylinder bore - something to ask before purchase perhaps, although as I already noted, it won't affect volume of fluid moved.

Thanks for digging out the paperwork. I'm impressed you found it.

[tacr2man]

FWIW I fitted about 3 servos to clutch on L/Cr out in Oz for customers , using the mgb unit , which worked well , Toyota fitted later models with a self contained m/cyl servo . HTSH

[mickeyw]

Toyota fitted later models with a self contained m/cyl servo . HTSH

I found what I suspect may be similar arrangementsfor a Patrol on fleabay.

I think the remote unit will be far less work to fit though.

Time to go shopping me thinks...

[Martin Price]

I was suffering with knee problems at the time I bought my 90 and it got to the point it was almost impossible for me to drive, so I fitted a servo. I used a Lockheed LE72696. I measured the pedal force required before and after fitting - it was reduced from 25lbs to 14lbs, which was about the same as my wife's Audi A2 that she owned at the time.

Here are a couple of pics of the installation.

I did have trouble trying to get all of the air out of the hydraulic system after I fitted it, but a Gunson Eezibleed kit soon sorted it out. It then worked reliably for the 7 years I owned the vehicle.

[mickeyw]

That's a tidy looking installation Martin.

Thanks for sharing the photos.

The force comparison is useful data too - I wish I'd measured my pedal force prior to removing the pedal from the bulkhead.

[simonr]

I used a remote servo from an Austin Princess (from a scrap yard). No idea what ratio it gave - but I'd guess between 3 & 6:1. The clutch was incredibly light - I ended adding a stronger return spring so it had some feeling to it.

At the time, I was spending a lot of time in start-stop traffic - and the servo made a huge difference.

Bleeding it was tricky, but went OK. The biggest problem was learning the clutch biting point by position rather than force applied.

Si

[Roverdrive]

MArtin

Cheers for the pictures.

Very tidy insallation, and food for thought.

My knees aren't getting any younger either!

[Roverdrive]

Apologies for the thread hi-jack, but it is connected to the fitting of a remote servo!

Is there a non return valve on the brake servo connection, whether internal or external?

I have a concern in case a failure of the clutch servo or pipe system causes a loss of vacuum in the brake servo.

[pat_pending]

Yes, there is a non return valve built into the servo connection. However the instructions that came with my genuine ap-Lockheed unit say another in-line non return valve is necessary.

[Roverdrive]

Cheers for that.

I have an additional vacuum reservoir to install should it be required.

From the instructions you have, would it be permissible to have the NRV at the pump to allow the reservoir to be available to both servo units, or is the additional NRV there to "protect" the brake servo?

[pat_pending]

As these units were intended to be fitted to 1960s-70s petrol engined cars, I would think the additional NRV is there to protect the servo from petrol fumes and the effects of backfires.

As such it's probably not necessary on a diesel/vacumn pump system. I had one so I fitted it.

Putting one at the vacumn pump wont hurt though.

[mickeyw]

Well I ordered a 2.3:1 Powertune servo from MGServices Heathrow. They have a shop on fleabay.

It arrived on Thursday, unfortunately the box looks like someone played footy with it, and the plastic air valve cover is broken . A quick email to the supplier has seen a replacement cover being put in the post.

The unit looks nicely made, and comes with mounting brackets, a length of vacuum hose and spring hose clips, length of 3/16" steel brake hose with the tube nuts and flares ready made. There are two NRVs included, one straight and one right-angled, catering for varying mounting options.

The clutch pipes are 1/4", and I am mindful that using smaller pipe for clutch operation may impact return speeds, so I will continue this size through the servo cylinder, instead of the supplied 3/16".

The ports in the cylinder look larger dia than the bore of the 3/16" pipe, so I don't think they will restrict the flow. I have a couple of 3/16" male to 1/4" female adapters, relieved from old clutch master cyls. This will enable connection of the larger bore pipe.

[Maverik]

Depending on how lighter clutch you want, have you checked what spring arrangement you have on the pedal at all? - I took the original pedal return spring off, and installed a "td5" style pedal with the fancy inverting spring, which has made my clutch now comparable to that of my Subaru, takes me by surprise pretty much every time I jump in it... its a diesel clutch right enough, so don't know how that compares with a V8 clutch, a lot less cost and faff then a vacuum assist.... just a thought...

[mickeyw]

I went down that route with my V8 90, and it did make a difference, although it didn't make it as light as I would have liked My knee suffers with the clutch in heavy traffic, or a day's off roading, so lighter is better.

When I stuck the auto box in the 90, I kept the sprung assisted pedal (in storage, not in the car, ), and that is what I have stuck in the 110. The pedal assembly has been refurbished, and re-lubed etc to ensure optimum function. The servo will be complementing this. If it is too light to function well I can always add a spring, or even take off the assist spring.

You're right that the diesel clutches do feel a fair bit heavier at the pedal than the V8. My all time heavy LR clutch has to be the 2.5Td & LT77 combo, although I found the Td5 heavier than the V8 too.

[Hybrid_From_Hell]

Mike, 

 

any pics install guidance as on my to do list !!!!!!!!!

 

Nige

[Singr07]

On 6/20/2014 at 8:45 AM, tacr2man said:

FWIW I fitted about 3 servos to clutch on L/Cr out in Oz for customers , using the mgb unit , which worked well , Toyota fitted later models with a self contained m/cyl servo . HTSH

Hi I need a lighter clutch too. Could you please sort it out for me too? I live in B65 area and willing to drive to your place. You may send me a PM and provide a quote. I will e-mail you my Landy's pictures if required. It is a 1989 model which has a 300tdi conversion by the previous owner. It still has the old type of clutch pedal. Thanks

Edited April 7, 2022 by western
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