The curious case of the Atom 4 brakes

[plip1953]

Doh - springs now on back order….

I see that Questmead have 7lb springs in stock, but they are silly expensive (£8 each!!) and I'm not sure whether they could be a bit too much force-wise.

[Charlie]

Part box has the 7lB ones for £2.38 they have others listed but contact for availability https://www.part-box.com/search-results-2/

[robfitz]

Anyone know the part number for the appropriate size Pagid RS14? Steve did send me a picture of the box but annoyingly I can’t find it now. Is this the right set:

https://www.a-pp.com/Categories/Braking ... -E8076RS14

[Charlie]

Anyone know the part number for the appropriate size Pagid RS14? Steve did send me a picture of the box but annoyingly I can’t find it now. Is this the right set:

https://www.a-pp.com/Categories/Braking ... -E8076RS14

Seems to be correct if for AP CP7600 caliper according to this page https://www.bestbrakes.com/u-8076-rs14- ... 4mm-r.html

[Charlie]

Anyone know the part number for the appropriate size Pagid RS14? Steve did send me a picture of the box but annoyingly I can’t find it now. Is this the right set:

https://www.a-pp.com/Categories/Braking ... -E8076RS14

Here is the same cheaper but coming from Europe so may get charged import duty although seems to be in stock https://shop.motorsracingspares.com/en/ ... 09858.html

[robfitz]

Thank you

[Monza]

If the factory demo Atom does not have any brake pedal problem, just put on it a new set of discs, calipers, pads, MC , to see what will happen. Or just do some intensive testing on a customer car who brings it for the special bleeding procedure .

[Winmoz]

Guys, Henry has laid out his desired approach to try and get to the root of any issue. In order for progress to be made, observing the issue(s) in situ and having the opportunity to assess remedies in a controlled manner needs to happen.
As we know, Ariel’s whole ethos is about making sure we have the right car for our unique needs. And as we also know, Atom owners care a lot about their cars and how they drive.
So we have aligned goals. Be good to see some more 4s with reported braking issues return to the factory so more diagnostic work can be done.


Sent from my iPhone using Tapatalk

[plip1953]

What we anticipate will be the last changes to be made to one of the cars I'm associated with will be tested out on track tomorrow at Cadwell Park.

What we now have are:-
1. A pedalbox brace - designed and fabricated by Corten-Miller Motorsport. It really is a "must have".
2. Master cylinders at 0.7" front and 0.8125" rear (OE they are 0.625" and 0.7"). Upping the size of the rear MC is new.
3. 4lb anti-knockback springs all round. Same as in the Alcons on earlier models.
4. An AP proportioning valve in the rear circuit. Also recently added.
5. A set of front Carbotech XP20 brake pads. High friction, but previously tried and liked. Pagid RS14s rear.
6. Motul dot 4 brake fluid.

And most crucially, we have eliminated any and all air in the system. Don't underestimate how important, but not especially easy to achieve, this is!!

Collectively we now have a setup that should stop the car really well and give maximum confidence to the driver to fully utilise the retardation performance that is now available. We will find out tomorrow if these goals truly have been met.

Just to add - the addition of the proportioning valve is simply to provide a slightly different way of setting the front/rear brake balance. With the new MC sizing we anticipate being able to set the balance bar at 50:50 or very close to that. But if the rears still have any tendency to lock up, which it never a good thing, we can then utilise the proportioning valve to limit max hydraulic pressure to the rears, but still retain 50:50 on the balance bar.

[Monza]

[robfitz]

Why add the proportioning valve rather than just using the bias adjuster to shift a bit towards the front?

[salvechris]

Hi

And most crucially, we have eliminated any and all air in the system. Don't underestimate how important, but not especially easy to achieve, this is!!

Is there a guidance availible to do it in a best way???

Thanks Chris

[Curves Junkie]

[mention]plip1953[/mention]
Sound good
I am curious about your driving report.

4. An AP proportioning valve in the rear circuit. Also recently added.

Do you have forgotten to order the bias adjuster?
Please show the partNo. of the valve.

And most crucially, we have eliminated any and all air in the system. Don't underestimate how important, but not especially easy to achieve, this is!!

Yes, it's not easy to bring all air out the system when you have AP-master zylinders. The alcons are much more easier.

[plip1953]

Why add the proportioning valve rather than just using the bias adjuster to shift a bit towards the front?

Using a proportioning valve limits hydraulic pressure to the rears in a different way to simply using the balance bar. Without going to too much detail, it can be used to reduce the max pressure that the system will otherwise be trying to produce, but without changing the characteristics of how pressure is built up during the very initial part of the braking event. I consider it to be a good way of preventing lockups, but still getting the most out of your rear brakes.

[plip1953]

Hi

And most crucially, we have eliminated any and all air in the system. Don't underestimate how important, but not especially easy to achieve, this is!!

Is there a guidance availible to do it in a best way???

Thanks Chris

I'd be lying it I said I could offer you any special tips or tricks. On the cars that I'm associated with that kind of work would normally be carried out by a very experienced mechanic, most likely involving the use of a pressure bleed system. Personally, I would very happily check for air still in the calipers, but don't consider myself competent enough to deal with deeper seated trapped air situations.