Lotus Elan

Strange rear brakes

PostPost by: rgh0 » Fri Sep 25, 2015 10:12 am

The rear brakes are if anything to good on an Elan as they are always under- loaded versus the standard fronts.

You may have replaced them if one of the following applied I believe.

1. The hand brake annoyed you as it always went out of adjustment ( because you did not know how to set it up right)
2. The brakes suffered major damage and you could not get the parts needed at an acceptable cost. In the early 80's Lotus could no longer supply many spares and the specialist replacement market had not yet established itself and not many cars were at wreckers for second hand parts, it was the low point in Elan parts availability in my experience (at least here in Australia)
3. You just thought you could do it better and enjoyed doing the modifications.
4. You misdiagnosed the over performance of the rear brakes as under performance and wanted to replace them for the wrong reason.

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Rohan
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PostPost by: gus » Fri Sep 25, 2015 11:03 am

Someone must have been making this conversion since the casting is custom. WE have all just forgotten because it aint on the internet
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PostPost by: elanman999 » Fri Sep 25, 2015 11:54 am

Chris Sanders wrote:It's the original chassis, although I had it repaired and galvanised by Spyder.


Ah, that explains why there are no body mounting holes drilled.
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PostPost by: Chancer » Fri Sep 25, 2015 1:48 pm

I see that you are using CV jointed drive shafts, could the disc brake conversion have been part of a CV driveshaft conversion using the then current Rover 2000 as the donor vehicle for the parts?

From what I recall they had a De-dion rear end so would have probably had CV jointed drive shafts or perhaps they hadnt been invented then :lol: My Stag used universal joints, Rover parts were then excellent quality so I guess the calipers were very good and the CV's also if they were fitted.
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PostPost by: Chris Sanders » Sat Sep 26, 2015 8:42 am

Good point - the CV conversion would have been a good reason to do the conversion - I would love to know the origin of the uprights though...
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PostPost by: CBUEB1771 » Sat Sep 26, 2015 11:46 am

Chris - A bit off-topic but you should reverse the orientation of inboard pivot bolts on the rear control arms. The front bolts need to slide to the rear for removal and the opposite for the rear bolts. In their current orientation the bolts will foul the body if you need to remove the wishbones with the body in place. The correct orientation is shown in both the Workshop Manual and the Service Parts List.
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PostPost by: Spyder fan » Sat Sep 26, 2015 3:38 pm

A great topic to outline that there's nothing new under the sun.
There are lots of options to stop a car using hydraulic means. My own cars use Ford Sierra brakes... Roughly.... Nothing wrong with that as sierras had up to 500+ bhp at times!

Spyder use a bespoke rear upright system in order to use Sierra brakes and hubs for discs and calipers that will handle all the power you need..... Cheap as chips as well !


Your A frames are interesting being non standard, but nothing wrong with them, just being what's needed at the time to do the job!


Sweden Rules...... Ok Sandy?
Kindest regards

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PostPost by: Chris Sanders » Sun Sep 27, 2015 7:27 am

CBUEB1771 wrote:Chris - A bit off-topic but you should reverse the orientation of inboard pivot bolts on the rear control arms. The front bolts need to slide to the rear for removal and the opposite for the rear bolts. In their current orientation the bolts will foul the body if you need to remove the wishbones with the body in place. The correct orientation is shown in both the Workshop Manual and the Service Parts List.

Good to know - thanks for the tip.
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PostPost by: elj221c » Mon Sep 28, 2015 11:24 am

RotoFlexible wrote:I think Roy meant that the Rover's front suspension was unusual. We had one, decades ago, and my father had many problems with the rear brakes, but I don't recall any details of the front suspension.


That is what I meant.

Chancer wrote:From what I recall they had a De-dion rear end so would have probably had CV jointed drive shafts or perhaps they hadnt been invented then :lol:


Ordinary UJs were used.

Just for info:-

http://www.britishv8.org/articles/rover-p6-design.htm

As Rohan says, standard Elans are a tad overbraked on the rear. When the HSCC started the Historic Road Sports category of racing there was a big controvesy about the substitution of +2 front brakes in order to balance the braking as a 26R type twin cylinder and balance bar setup was not allowed under the regs. Non Elan people thought it unfair. The Elan drivers claimed it was a safety issue and should be allowed.....
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PostPost by: rgh0 » Tue Sep 29, 2015 11:18 am

elj221c wrote:As Rohan says, standard Elans are a tad overbraked on the rear. When the HSCC started the Historic Road Sports category of racing there was a big controvesy about the substitution of +2 front brakes in order to balance the braking as a 26R type twin cylinder and balance bar setup was not allowed under the regs. Non Elan people thought it unfair. The Elan drivers claimed it was a safety issue and should be allowed.....


Most cars of the era suffered from weak rear brakes as they tended to use drums at the rear. These have good initial bite but poor performance under extended high load situations. Good initial rear bite is an advantage as the rears can take initial load before the weight transfer to the front under the front brake load. However you don't want them loosing performance and pedal travel increasing as they heat up like drums do.

I faced the same issues in my production sports car class to try to balance the rear versus front performance with the tyres i use. I could fit a pressure reducer to the rear brake line but I find I can balance the brakes well by flitting a high coefficient of friction front pad and lower coefficient of friction but good initial bite rear pad.

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