New-build 420R brake problems

[rjn]

Hi

I'm just finishing off my first Caterham build (420R) and this weekend adjusted the handbrake and bled the brakes.  The handbrake cable is now very taut on the third click, and after bleeding each corner three times there are no air bubbles at all coming out of any of the callipers.

However…  neither the handbrake nor the footbrake is working effectively.  I can see the handbrake cable is doing its job and pulling on the mechanism at the calliper.  I can also see that depressing the brake pedal is moving the piston.  Nevertheless I can still move each wheel easily by hand!  On closer inspection, when the foot or handbrake are applied, the brake pads are indeed moving but not enough to grip the brake disc firmly.  The callipers came pre-assembled; I just had to put the brake pads in and bolt it to the rear hub assembly. I'm wondering if I've made a basic mistake somewhere - photos attached.

Any suggestions would be gratefully received!

Many thanks, Roger

[Jonathan Kay]

I'm just finishing off my first Caterham build (420R) and this weekend adjusted the handbrake and bled the brakes.

In that order? See here.

Jonathan

[ChrisC]

Firstly your anti rattle spring clip doesn't look like its sitting properly,  Have a look here

http://caterham420r.blogspot.co.uk/2015/11/build-day-15-frame-steering-rear-brakes.html 

When I recently fitted the Caterham branded rear calipers to my 360R I found it possible to position the inside pad so you could not get the caliper over the pads.   This isn't a problem I have ever had before, so it stumped my for a few mins, then I repoistioned the pad and caliper fitted fine.   Maybe you have managed to fit the caliper while the inside pad is not fitted properly. 

[p.mole1]

Check your brake piston is in the correct position the pip on the bottom of the pad should fit inside one of the four cut outs in the piston.

[Purplemeanie]

Hi Roger,

as p.mole1 says the pips being in the right place might be the issue. If I got this wrong though (I did once) the caliper wouldn’t fit over the pads, so perhaps not that.

As Jonathan says you have to make sure you do everything in the right order. If you apply the handbrake before filling and bleeding the brakes then you can get the self adjusters activated before they should be. This all confused the hell out of me when I recently built my 420 and I have half a blog post written about how the brakes and self adjusters work (sorry that doesn’t help a great deal for you though) - one day I may finish that off. You’ll need to rewind the pistons if that’s the case. 

There might be something in the pictures on this page that help though...

https://www.purplemeanie.co.uk/index.php/2017/10/01/build-session-21-a-frame-ears-hubs-discs-callipers-brake-pipes-wheels/

John

[Purplemeanie]

Hi Roger,

  I'm not sure if this helps at all but while not getting my head around how the rear brake calipers work I pulled one apart and took a picture of the insides.

If that's not high enough res then I put a copy onto the blog post I mentioned above.

It might confuse you more than help, but I found I wanted to know how things worked before I would accept what others were telling me.

John

[rjn]

Many thanks for all the suggestions.  ChrisC, you were right about the clips.  I've put them in the correct way now and I have a fully working handbrake!  The foot brake is still barely working though and I suspect this problem is linked to what Jonathan & PurpleMeanie both said - I'm afraid I did try out the handbrake before bleeding the hydraulics so have probably messed up the self-adjustment in the piston.  I'll try to re-wind it...

[Jonathan Kay]

Have you spotted the windback tools in the Equipment Register?

Jonathan