Lotus Elan

zetec brake servo

PostPost by: mikealdren » Thu Sep 03, 2020 8:01 am

Is anyone running a Zetec car with Sierra brakes and no servo? I am looking at fitting dual line brakes but a dual servo is just too large and I'm not sure what the pedal loads would be like.
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PostPost by: Foxie » Thu Sep 03, 2020 12:14 pm

I fitted the complete Spyder supplied Sierra brake system (and wheels ) with Willwood 4 pot calipers to my non-Zetec Plus 2S a few years ago. I still have the standard +2 servo (3:1) and a 3/4" master cylinder.

I still need to be fairly hard on the pedal for maximum brake effect.

(I don't know what servo (if any ) Spyder fit to the Zetec, does anyone have details ? )

I have considered fitting a dual brake system, I understand there is a Triumph dual M/C, but I fear two servos might be required.

I put the car up on blocks last evening to do a thorough brake bleed, as the pedal feels a bit soft :)
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PostPost by: gav » Thu Sep 03, 2020 3:54 pm

I’m running a dual circuit system with my zetec and I was using a dual circuit servo but the brakes locked on and wouldn’t release until they cooled down. I removed the vacuum from the servo and the brakes are great now (touch wood) so I am going to remove the servo.
I have split master cylinders with a balance bar using the trident racing pedal box. I recall it has a 4:1 pedal ratio as opposed to the standard which I think we worked out was 3:1.
I’m running a Caterham 4 pot front calipers and sierra rear callipers (so that I didn’t lose the spinners) and from memory, the master cycles are 0.7 on the rear and 0.6 on the front (AP Racing bores). Really good feel and you don’t need to stand on the pedal to make it work. The balance bar is biased slightly to the front and there isn’t much pedal travel.
Hope this helps
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PostPost by: mikealdren » Fri Sep 04, 2020 8:56 am

Spyder fit a standard +2 servo but dual servos would be costly and large. There are dual servos on the market but they are large too.

I'm also looking at the Spitfire dual M/C but Andy says the brakes would be too heavy un-servoed. I'm wondering whether that is really the case. Gavin's note gives me hope!
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PostPost by: gav » Fri Sep 04, 2020 10:23 am

Mike
When you split the master cylinders into front and rear, you have much more flexibility to get the masters balanced for the callipers.
I don’t know of any dual circuit masters that have different volumes (might well be wrong) and I don’t know of many with small capacities so it might be this that would lead to the need for a servo.
The problem is that fitting a twin master set up can impact on originality unless you are able to produce a pedal box that doesn’t impact on the shell. Things like pedal ratios also impact on the need for servos.
I have been on a long journey getting my set up where I want it.
I don’t want to stifle your enthusiasm but I discovered that it is really quite involved and hard to get right first time.
Happy to share experiences but I’m no expert
Thanks
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PostPost by: rgh0 » Fri Sep 04, 2020 10:43 am

Regardless of the actual disks and calipers used an Elan or Plus 2 should not need a servo with modern high coefficient of friction pads

cheers
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PostPost by: Spyder fan » Fri Sep 04, 2020 12:36 pm

No servo on my +2 Zetec or S4 Duratec. They both use 3/4 inch bore master cylinders single line. The S4 has Wilwood 4 pots on the front and the +2 has Sierra XR4x4 calipers. The +2 needed the pads upgrading to get good stopping and feel without stamping on the pedal. The S4 has really good feel and excellent stopping using Wilwoods standard pads. No need for a servo on either.

A friend has his S2 set up with a dual line system, he had to try a few different pads out ending up with Hawk ( I think? I will check if needed) which gave very good results without a servo.
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PostPost by: mikealdren » Fri Sep 04, 2020 2:05 pm

Thanks all, I'm definitely inspired to try a non servo system.

The Spitfire dual master cylinder should fit the pedal box directly, the pipes will come out on the RHS so I will need to take them over or under the master cylinder but that should be ok. The master cylinder is the same diameter as the +2 and I will check the available travel/displacement - the Spitfire has disk/drum but I expect it will be ok. The pedal box (& therefore ratios) will also be standard.

As far a balance is concerned, the master cylinder will give me the same line pressures front/rear and that's a good starting point as it's what the standard car uses. It's a road car so I don't expect to be pushing the brakes to the limits and I'm using greenstuff pads so I'll see how it goes for pedal loads - thanks for the encouragement Rohan.

Luckily my engineering background includes a couple of years running brake testing at Millbrook so I shouldn't have any difficulties if I need to modify anything. I'll certainly make sure that I don't have premature rear end lock up and I can introduce some pressure limiting if required but it seems unlikely as Spyder have fitted lots of cars with this setup.
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PostPost by: Foxie » Fri Sep 04, 2020 7:04 pm

Spyder fan wrote:No servo on my +2 Zetec or S4 Duratec. They both use 3/4 inch bore master cylinders single line. The S4 has Wilwood 4 pots on the front and the +2 has Sierra XR4x4 calipers. The +2 needed the pads upgrading to get good stopping and feel without stamping on the pedal. The S4 has really good feel and excellent stopping using Wilwoods standard pads. No need for a servo on either.
.


I was not happy with the EBC Greenstuff pads on the Willwood calipers on my Plus 2, so I changed to yellowstuff. They were much better, but still need a good push, even with the servo. 3/4" MC.

:)
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PostPost by: Spyder fan » Sat Sep 05, 2020 12:47 pm

Foxie wrote:
Spyder fan wrote:No servo on my +2 Zetec or S4 Duratec. They both use 3/4 inch bore master cylinders single line. The S4 has Wilwood 4 pots on the front and the +2 has Sierra XR4x4 calipers. The +2 needed the pads upgrading to get good stopping and feel without stamping on the pedal. The S4 has really good feel and excellent stopping using Wilwoods standard pads. No need for a servo on either.
.


I was not happy with the EBC Greenstuff pads on the Willwood calipers on my Plus 2, so I changed to yellowstuff. They were much better, but still need a good push, even with the servo. 3/4" MC.

:)


The Wilwood fast road pads are far better than EBC green or yellow, this is what I use.
https://www.burtonpower.com/wilwood-fas ... -8946.html
Very little pedal pressure required to stop the car. Spyder had a demonstrator +2 fitted with Wilwoods a few years back, no servo on that and it stopped really well, why yours needs a servo and is disappointing is a bit of a mystery to me.
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PostPost by: Foxie » Sat Sep 05, 2020 1:17 pm

Spyder fan wrote:
Foxie wrote:
I was not happy with the EBC Greenstuff pads on the Willwood calipers on my Plus 2, so I changed to yellowstuff. They were much better, but still need a good push, even with the servo. 3/4" MC.

:)


The Wilwood fast road pads are far better than EBC green or yellow, this is what I use.
https://www.burtonpower.com/wilwood-fas ... -8946.html
Very little pedal pressure required to stop the car. Spyder had a demonstrator +2 fitted with Wilwoods a few years back, no servo on that and it stopped really well, why yours needs a servo and is disappointing is a bit of a mystery to me.


Thanks for that !

Burtons have my order !

:)
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PostPost by: peterako » Wed Oct 14, 2020 9:16 am

Hi Seán,

Did you go 'servo-less' in the end?

Long time no speak :)

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PostPost by: Foxie » Wed Oct 14, 2020 7:59 pm

peterako wrote:Hi Seán,

Did you go 'servo-less' in the end?

Long time no speak :)

Peter


Hi Peter !

No, I didn't go 'servo-less' I lately changed to the Willwood fast road pads, but I haven't even bedded them yet. what with all motorsportshut down, FOXIE has been enjoying a bit of a break. I've been very busy with many neglected projects. Strange how this situation presents welcome changes of course !
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PostPost by: gav » Thu Oct 15, 2020 10:21 am

Hi Foxie

Glad to see you're keeping busy.

Do remember to put the right engine in the right machine :roll:

Which model is the red car? It looks as tight a squeeze as an Elan.

All the best
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PostPost by: Foxie » Thu Oct 15, 2020 12:06 pm

gav wrote:Hi Foxie

Glad to see you're keeping busy.

Do remember to put the right engine in the right machine :roll:

Which model is the red car? It looks as tight a squeeze as an Elan.

All the best
Gavin


1978 Ferrari 308 GTS. :D

The V8 engine is far tighter than an Elan :shock:
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