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Rear Brakes


p.mole1

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I have just had the dedion tube, anti roll bar and radius arms powder coated and have noticed a massive problem with my rear brake calipers. My rear calipers are attached via a solid brake pipe!. I have never seen this on any car with a sliding caliper. The calipers should be attached with a flexible hose ? Firstly you have to have to remove the brake hose to change the pads and the rigid pipe will continuously being flexed due to movement of the caliper. Are all sevens like this?. I am going to try and make up a set of flexible brake lines before they crack- unbelievable?

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All like that!!

I’ve converted mine to aeroquip - I can dig out my receipt and list the order items from Demon Tweeks if you’re interested in converting.

two advantages - flex as the pads wear and calipers move and if you need to dis-assemble the rear just hang the calipers up and no need to bleed.

Let me know and I’ll post up the list.

Ian

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I thought that the rigid pipes were undesirable when I assembled my 7, so asked the factory (by 'phone in those days) and they said that it was fine: "Just follow the Guide". There might have been a hint that it was different for race cars.

And every time I've had them off since I've reassured myself with the wonderful notes from Alcester Racing 7s.

And the last time it came up here I asked the factory if flexible pipes had any disadvantages of which they were aware. They said "No".

... there have been failures on race cars

And that's just what I was about to ask.

Jonathan

 

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Hi Ian thanks, I would be grateful if you could post the list of parts required to fit flexible brake lines. Did you make your own lines up? I have done this for mountain bikes, but never for a car but I'm assuming it's the same procedure. I must admit I never really took any notice of the rear brakes till I overhauled the rear end. I am surprised they are still like this! 

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From my experience it isn't about the quality of the surface on track vs road, it is more that race cars have their pads changed far more often than road cars and so the solid pipe ends up getting a lot more abuse just from that. 

Not so many years ago (I don't know what happens now) Academy car kits came with solid rear pipes and that was what you raced with but at least one other series made the use of flexi pipes mandatory so if you changed series an upgrade was required.

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The rear calipers are a single piston sliding version in which the body moves in normal operation, you cannot therefore operate this with a rigid brake pipe it must be flexible.

Removing the caliper for a pad change only worsens this as you are bending and therefore work hardening the pipe leading it toward the inevitable fracture and brake failure.

As I said a shocking piece of engineering.

 

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Right dug out the paperwork from 2004. I was advised to speak to Dave Kimberley at Demon Tweeks who was an ex caterham owner and knew all the parts needed to convert to braided. Here is the list (quantities in brackets) - with the exception of one item all the part numbers tally with the current DT website.

Be aware you will need to cut braided hose and make up the pipes with the supplied olives and metal threaded fittings. There are How To videos on youtube. The fittings / pipe are dash 3 and fittings are zinc plated steel. Other metal types are available

A) Straight Male Bulkhead fitting GDR443-03P 3/8 * 24 (2)

B) Straight Female GDR6001-03P 3/8*24 (2)

C) Washer GDR44516 (2)

D) Goodridge 600 Clutch & Brake Hose GDR600-03 (2 meters)

E) Adaptor GDR305-03-31P (could only find GDR305-03-31Z1) -3 (3/8*24) to M10*1 (2)

Brass Olive (spares!!) GDR1205-03B (several!)

I replaced item B (straight female ) with 45 degree swept tube female GDR6046-03P (2) as gave better route for hose coming off the calliper and passing brackets on the dedion.

A) fits into T Piece bolted to dedion, E) fits into calliper with washer C), B) or alternative fits onto adaptor E). Hose cut to length between A) and B).

Hope that makes sense. Pretty sure there are guides in the archives as thats where I got my info in 2004.

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  • 2 weeks later...

Ok I've fitted my new brake lines and I now have a spongy brake pedal! The brakes have always been solid but a bit lacking feel, it is an AP master cylinder. I have bled them twice and I let the fluid run through the lines before I fastened up the unions. I fitted new pads and wound the pistons fully home. I am using silicon brake fluid, but only because that is what the car had in it when I bought it and I haven't had problems with it.

I have fitted new discs all round and Ferodo DS 2500 fronts and Mintex 1144 rears and the brakes apart from being spongy are terrible, dead, no bite or feel whatsoever and impossible to lock. Although I have not really been able to bed them in properly yet due to no MOT. The pedal is only slightly spongy so It feels like I may have a bit air in the rear calipers but I can't seem to get it out?

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Have you bled them in the past?

Where are the bleed nipples... top, bottom, side?

How did you bleed them: blow, suck, or gravity and pedal alone? 

I am using silicon brake fluid

What specification and brand? And what was in there before?

Jonathan

PS: That's "silicone".

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Hi Jonathon, I have dropped a bit of a clanger, my brake fluid was green? and when I bought the car it had a receipt for "synthetic brake fluid" I assumed this was silicone brake fluid. 

It turns out it's not, it is water soluble and does not mix with the silicone fluid. The brakes have never been touched since I bought the car in early 2016

I initially bled the rear calipers using the pedal via the brake banjo fitting and then the bleed nipple and did not need to top the system up. 

I bought some Automec silicone fluid DOT 5 the purple stuff and pushed all the brake pistons back then flushed the system through with Automec fluid using a vacuum bleeder. All the brake nipples are on the top of the calipers

I must admit I am not a fan of Silicone brake fluid as it destroyed the brakes on my MIni due to water ingress, it rotted the master cylinder and brake proportioning valve

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The brake pedal is now a bit firmer, however the rear caliper seems to flex quite a bit on it's sliding pins. Hopefully the brakes will improve once bedded in,I hope! . I have put a litre of fluid through the brakes and rotated the caliper in every direction just in case so I don't think there could be any air trapped.

The brakes have always been a bit lack-lustre, but I could not identify the original pads, chances are they are 1995 vintage! Lets hope things improve once these pads are worn in as they are still hopeless! almost like everything is coated in teflon, they have no bite and increasing the pressure produces a small increase in retardation but absolutely no feel and I doubt I could lock the wheels.

MOT on Monday

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