The curious case of the Atom 4 brakes

[plip1953]

Today's trackday at Cadwell seems to confirm that fitment of the anti-knockback springs has indeed had a very positive effect on brake pedal feel, and even more importantly the pedal felt as good at the end of the day as it did at the start.

[reg]

Good stuff, so initial thoughts of the seals being far to aggressive for a non servo application seem to be well founded. Keen to hear the factory feedback on this.

[plip1953]

Good stuff, so initial thoughts of the seals being far to aggressive for a non servo application seem to be well founded. Keen to hear the factory feedback on this.

I'm really interested to know why you might think pad retraction is any less pronounced where a servo is present?

[Yorkshire]

I’m glad it all worked out ok but without a back to back test of one just with a master cylinder change or one just with knock back springs we will never really know what made the difference
I know of five Atoms that have purely changed master cylinder and there brakes seem fine now
Could someone just do knock back springs on there own see if that improves standard brakes But great result for all

[Alistairbuchanan]

I’m glad it all worked out ok but without a back to back test of one just with a master cylinder change or one just with knock back springs we will never really know what made the difference
I know of five Atoms that have purely changed master cylinder and there brakes seem fine now
Could someone just do knock back springs on there own see if that improves standard brakes But great result for all

Yeah agreed and the master cylinder change is so much easier than having to do the springs


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[reg]

Good stuff, so initial thoughts of the seals being far to aggressive for a non servo application seem to be well founded. Keen to hear the factory feedback on this.

I'm really interested to know why you might think pad retraction is any less pronounced where a servo is present?

From the outset these calipers just don’t seem to be the correct spec, specifically if you look at the application table. If I ( and I’m a bit daft) was specifying the calipers I would choose the model which included ‘race’ and ‘single seat’, purely as from my own thinking they would be suitable for cars like these. Obviously, Ariel worked with AP and came up with this, which, let’s be frank, is not for purpose whether road or track. With a servo I’m pretty convinced the issue would be overcome. Why spec a caliper for ‘fast road’ when the next mode up appears to cover all bases? What is it 1000-1200 PSI needed, and 6:1 on the pedal? What does the Ariel setup generate? Like you I’m puzzled as to how AP have supplied something which doesn’t work out of the box. Anyway. Bikes never had servos, just different ratio’s and more efficient calipers.

I’m glad the springs worked well and is giving the owners what they should have had in the first place

[plip1953]

I’m glad it all worked out ok but without a back to back test of one just with a master cylinder change or one just with knock back springs we will never really know what made the difference
I know of five Atoms that have purely changed master cylinder and there brakes seem fine now
Could someone just do knock back springs on there own see if that improves standard brakes But great result for all

We went through about a four or five stage incremental process and made progress each time, but the pedal still wasn't as good as we thought it could/should be so carried on and most recently added the springs. This last change seemed to make the biggest difference. But it's all relative, and some drivers may actually prefer a slightly less responsive pedal.

If I was starting on the journey again I would start with the springs, quite likely also want to make the MC changes, and most definitely also want to fit the Corten Miller pedalbox brace.

[plip1953]

Good stuff, so initial thoughts of the seals being far to aggressive for a non servo application seem to be well founded. Keen to hear the factory feedback on this.

I'm really interested to know why you might think pad retraction is any less pronounced where a servo is present?

From the outset these calipers just don’t seem to be the correct spec, specifically if you look at the application table. If I ( and I’m a bit daft) was specifying the calipers I would choose the model which included ‘race’ and ‘single seat’, purely as from my own thinking they would be suitable for cars like these. Obviously, Ariel worked with AP and came up with this, which, let’s be frank, is not for purpose whether road or track. With a servo I’m pretty convinced the issue would be overcome. Why spec a caliper for ‘fast road’ when the next mode up appears to cover all bases? What is it 1000-1200 PSI needed, and 6:1 on the pedal? What does the Ariel setup generate? Like you I’m puzzled as to how AP have supplied something which doesn’t work out of the box. Anyway. Bikes never had servos, just different ratio’s and more efficient calipers.

I’m glad the springs worked well and is giving the owners what they should have had in the first place

I'm seeing around 60bar (900psi) of hydraulic pressure with the pedal set at it's lowest ratio. Obviously it all depends on how hard the brake pedal is pressed, but that seems to be about the max pressure before you get into the realms of lockups.

[Yorkshire]

Your definitely right but its an individual feel thing. The cylinder change is the cheapest and easiest the springs are messy and complicated to fit and the brace from what i have been told is £250 ish. All these firm up the brakes but then its a fine line between max brake and lock up (IMO) All three give max braking but is any feel lost? That's before we start on pad choice! Suppose everybody decides for themselves really. But good work and now you need to look at cooling as that's my next issue i'm trying to sort Cheers Stuart

[Monza]

The other thing we need to know with the springs is the pads wear. If they are to powerfull and keep the pads pushed on the disc of course wear will increase.

[plip1953]

The other thing we need to know with the springs is the pads wear. If they are to powerfull and keep the pads pushed on the disc of course wear will increase.

It's a fair point, but even with the springs fitted there is no obvious drag on the wheels - which was checked and validated as part of what we did today. It may be worth bearing in mind that Alcon calipers fitted to some of the earlier Atoms all had springs fitted from the outset.

[plip1953]

Your definitely right but its an individual feel thing. The cylinder change is the cheapest and easiest the springs are messy and complicated to fit and the brace from what i have been told is £250 ish. All these firm up the brakes but then its a fine line between max brake and lock up (IMO) All three give max braking but is any feel lost? That's before we start on pad choice! Suppose everybody decides for themselves really. But good work and now you need to look at cooling as that's my next issue i'm trying to sort Cheers Stuart

Have you seen the pedalbox flex video? I personally think around £250 to eliminate it is very good value for money.

It is very subjective, but I think it's fair to say that at every step of this journey pedal feel (and the ability to modulate) has been regarded as increasingly good.

Sorting out coolant temps is now a main priority.

[reg]

The other thing we need to know with the springs is the pads wear. If they are to powerfull and keep the pads pushed on the disc of course wear will increase.

As Phil said, the Alcons had 2kg springs and they were fine. Pad wear in my old one was amazingly good. I wonder why they chose not to fit them?

[plip1953]

The other thing we need to know with the springs is the pads wear. If they are to powerfull and keep the pads pushed on the disc of course wear will increase.

As Phil said, the Alcons had 2kg springs and they were fine. Pad wear in my old one was amazingly good. I wonder why they chose not to fit them?

I suspect it was simply because springs are not standard fitment to calipers belonging to the AP CP7600 family. And even if the question was asked I expect AP would say they aren't needed. I think we can now demonstrate otherwise!

[speedmachine]

So good that you guys solve all brake and cooling problems right in time for the factory to include the upgrade in my december build