The curious case of the Atom 4 brakes

[Preseh]

An update after the Bedford track day... My pedal is now back to where it was before the brake bleed Will chat to the factory on Monday and see what they say.

What did they say?

They didn't really give me a conclusive answer. I will say though that the long pedal travel doesn't bother me too much now I'm used to it. You can still get maximum stopping power it's just not as confidence inspiring especially for road use.

[reg]

So, to follow up on the ongoing development of the brakes I was one of the lucky ones to visit Anglesey this week, what a place. After the factory bled the brakes they were strong, lots of dust but they worked ok on the road. A few miles later and they were noticeably 'off'. Slightly more travel and the initial bite was worse. By the time I arrived at the hotel I had the feeling that all was going to return to where it was at the beginning?

Spent a good while on the first stint after which the pedal travel was quite long and they needed a good shove. More of the same but at the end of the first day they were getting a bit scary. Loads of travel and really a leap of faith, they always did stop but you had to stand on them. In the morning the pedal was much higher again. Paul cracked the bleeds on the calipers and master cylinders and there was a bit of air. Pedal was slightly better but then after more sessions on day 2 and leaving the car for 30 mins after one of them to cool off the pedal went so long it really bothered me.

Weirdly it sort of came back after frantic pumping (ahem) and sort of settled into it's moderately poor window. From then on I ignored them. But (looks at drivers book of excuses) it did reduce the amount of laps and definitely reduced track time as I was knackered! Not to mention late braking was not really possible. Another strange thing is I only managed to lock up one wheel once in all the laps, and I was trying to find the limits of them, the Alcons on the 3.5 could be easily locked if you were heavy on them.

Si Clark drove my car and needed some convincing that the car was ok , frankly he didn't need many brakes as he was sideways most of the time. So. It's obvious the 'sport' or whatever they call it now setup is not really fit for hard road use, let alone a track. Mark who owns a Mono and 3.5 said they did always bite at the same point but again, the Alcons are far better (as a setup). Pressing the brake pedal on a Mono is like putting your foot on a wall.

Upgrades;

I am following others in changing the pads to RS14, and swapping to the larger master cylinder. The plan is to by the 3/4 and swap the other one around, effectively one size up on both front and rear. Then fit the master cylinder brace, which is a lovely piece of kit. These are available if anyone else is interested.

Benn @ http://www.corten-miller.co.uk has a jig and will make them in batches, how many I don't know but if anyone is interested make a list and if there are 5, 10 etc the prices will obviously be more attractive the larger the batch. if you want to check your own pedal flex I think you'll be very surprised. I'll put pics on FB as it's easier.....

Nothing more at the mo. A couple of other owners were talking about it, and I am glad it is a known issue, it's not ideal to have a weapon of a car like this and have to let it keep cooling off because you're worried about ending up in the Irish Sea on a hot lap All joking aside we are guinea pigs for this, and I estimate to put the AP setup to a good level is now approaching £1000, which is more than salty considering this package was the belt and braces solution and an evolution of the Alcons which were some of the best brakes I have ever used.

[autobackup]

As the owner of a 3.5R fitted with Alcons front and rear which are simply epic I've been watching this thread with interest!

Can anyone tell me the reason why Ariel decided to move away from Alcon to AP for the Atom 4?

Why specifically AP for which the reviews I've read are somewhat mixed depending on the implementation/application!

Why didn't Ariel go to Brembo which are fitted very successfully to the TMI built cars rather than a manufacturer with no previous track record with Ariel vehicles?

It's becoming increasingly apparent from the reports I've read that the 'special' bleeding process offered by Ariel is temporary at best - so is it time for a permanent fix to be found (component upgrade?) and then possibly a general recall for cars fitted with AP brakes to sort this problem out once and for all?

[stupot]

Spoke to Steve about this when I dropped the Nomad off for a service as it has APs with the same issue. He did explain they manually bleed the brakes by pumping rather than pressure or vacuum. They also push each piston out in turn to fully extend the dust seal. So far so good but only driven it c100miles since.

Would fitting anti knock back springs solve the issue? AP do offer them. We're experiencing a similar thing with the pistons retracting slightly as you can get when riding kerbs. Just a thought.

[Preseh]

My brakes (two piece APs) are fantastic at stopping the car and there's never any brake fade. It's just the pedal travel can be a little disconcerting before you recalibrate your brain. For me it's not enough of an issue to change the setup but then I never owned the older car so I don't know what I'm missing!

[Winmoz]

I have a mongrel set up - 3.5R with Alcons on the front and APs on the rear.
Previously I had APs on the front and the ‘sport brakes’ on the rear and I was very happy.

With the upgrade to R power spec I opted to upgrade to bigger brakes on the rear, assuming that they would be Alcons.

I was underwhelmed initially, as the pedal was longer and I could not detect any braking performance improvement on the road.

Steve did the bleed and piston reset thing when the car got its side pods etc and the pedal was back to where it should be.

Then after a few sessions at Goodwood the pedal went ping and I had a few of those moments when you think the car is running away from you. Not good.

At the end of the day the end of the pedal travel meant my foot was way below the accelerator pedal, making transitioning to the exit hard as my foot kept snagging on the underside of the accelerator pedal (I have size 12 feet).
Currently waiting for Steve to advise as have booked Si for Bedford in a couple of weeks and would like to have my pedal restored to its former pert and firm glory.

[reg]

My brakes (two piece APs) are fantastic at stopping the car and there's never any brake fade. It's just the pedal travel can be a little disconcerting before you recalibrate your brain. For me it's not enough of an issue to change the setup but then I never owned the older car so I don't know what I'm missing!

It's like eating at McDonalds and calling it steak My road car has got better brakes tbh. One of the very best bits of the old car is now 100% the worst part on the new one.

[speedmachine]

My brakes (two piece APs) are fantastic at stopping the car and there's never any brake fade. It's just the pedal travel can be a little disconcerting before you recalibrate your brain. For me it's not enough of an issue to change the setup but then I never owned the older car so I don't know what I'm missing!

It's like eating at McDonalds and calling it steak My road car has got better brakes tbh. One of the very best bits of the old car is now 100% the worst part on the new one.

But what does the factory tell you than? Dont they offer a solution?

[robfitz]

I’ve got my car booked in to have them bled again on July 14th and thinking of ordering some pagids like I had on my Elise. Guess the risk is this in itself won’t be enough?

Definitely found them quite disconcerting on the second day at Anglesey this month.

[reg]

RS14's make a big improvement on their own tbh.

[AA70MUK]

Hi all,

Whenever I've had a long/spongey peddle it has always been air in the caliper, not loads but enough to affect it. The way I have sorted this in the past is to just let the calipers gravity bleed, crack the nipple until the fluid runs out and then lock it back up. That has always done the trick for me and now do it on all my vehicles.

Picking up my Atom next week and will be doing the same on it so can let you all know.

Thanks,
Simon

[autobackup]

Still no one has explained to me why Ariel decided to move away from such a long and successful partnership with Alcon to untried non servo assisted AP brakes for the Atom 4 - moreover to an AP model of brake that is normally designed to be servo assisted?

Additionally why choose AP and not (for example) Brembo brakes which have been the 'goto' performance brakes successfully offered by Ariel USA (TMI) for many years with no issues?

I've now owned an Atom with Alcons for many years and they have been epic (if rather screechy occasionally )!

This whole saga seems rather strange!

[plip1953]

Still no one has explained to me why Ariel decided to move away from such a long and successful partnership with Alcon to untried non servo assisted AP brakes for the Atom 4 - moreover to an AP model of brake that is normally designed to be servo assisted?

Additionally why choose AP and not (for example) Brembo brakes which have been the 'goto' performance brakes successfully offered by Ariel USA (TMI) for many years with no issues?

I've now owned an Atom with Alcons for many years and they have been epic (if rather screechy occasionally )!

This whole saga seems rather strange!

I'd be pretty sure that the switch from Alcon to AP was purely on commercial grounds rather anything performance related.

Where do you get the idea that this particular AP caliper is only meant to be used on cars with brake servos? It matters not a jot.

AP brakes are owned by Brembo!

The brake setup on the 4 is flawed in several respects. First, there is considerable flex on the pedal box assembly and this allows movement of the brake pedal that is doing nothing in terms of actual braking. Second, the choice of master cylinder sizes is far from optimised. My guess is that the same sizing (0.625" front and 0.7" rear) is unchanged from the regular caliper offering whereas it has been shown that a 0.7" front and 0.75" gives noticeably less pedal travel, but without adding significantly to the effort required even when braking really hard on track. And going up one size even further on the rear might actually be even better (but see below) Third, it is not ideal to have flexible brake pipes all the way from pedalbox to calipers. Even though steel braided, there will still be an element of flex that you don't get with rigid lines. And lastly, the DS2500 pad offered with the APs (are other options offered?) are most likely chosen because they are road legal pad but can just about cope with being got fairly hot without fading. But they are far from being a proper performance pad and would be the first thing I would change. Pagid RS14s have been shown to work very well on two cars I'm associated with, but there are loads of makes and versions that will work just as well or even better. Retaining DS2500s on the rear is ok in conjunction with the 0.75" MC, but a size larger ie 0.8125" rear is likely to be better matched in terms of allowing the pedalbox balance bar to set at or very close to centred.

[plip1953]

Hi all,

Whenever I've had a long/spongey peddle it has always been air in the caliper, not loads but enough to affect it. The way I have sorted this in the past is to just let the calipers gravity bleed, crack the nipple until the fluid runs out and then lock it back up. That has always done the trick for me and now do it on all my vehicles.

Picking up my Atom next week and will be doing the same on it so can let you all know.

Thanks,
Simon

I agree wholeheartedly with this bleed strategy, although I know others will argue that if no pressure is being used there is a risk of air being drawn into the system via (I think) the bleed valve threads. On the 4 there are also bleed valves on the MCs which need to be factored into the bleed strategy equation.

[Lew]

I'm quite disappointed to read that as I just finished to mount my rear brake kit (not tested yet).
The pedal feeling was the main reason I've spent 1500£ in the kit.

Which master cylinder do you have, I have 0,7" front and rear now (Steve confirmed me it should be like this on AA2/3) but I guess it was the case with Alcon front and rear, not AP...

[mention]Winmoz[/mention] Can you take a picture of the caliper/hose assembly for me please ?
I didn't get any adapter between the hose connector (female) and caliper connection (female as well).

I had a chat with Alcon at goodwood, they said our calipers are now obsolete, they don't have the casting moulds anymore

I have a mongrel set up - 3.5R with Alcons on the front and APs on the rear.
Previously I had APs on the front and the ‘sport brakes’ on the rear and I was very happy.

With the upgrade to R power spec I opted to upgrade to bigger brakes on the rear, assuming that they would be Alcons.

I was underwhelmed initially, as the pedal was longer and I could not detect any braking performance improvement on the road.

Steve did the bleed and piston reset thing when the car got its side pods etc and the pedal was back to where it should be.

Then after a few sessions at Goodwood the pedal went ping and I had a few of those moments when you think the car is running away from you. Not good.

At the end of the day the end of the pedal travel meant my foot was way below the accelerator pedal, making transitioning to the exit hard as my foot kept snagging on the underside of the accelerator pedal (I have size 12 feet).
Currently waiting for Steve to advise as have booked Si for Bedford in a couple of weeks and would like to have my pedal restored to its former pert and firm glory.