Alcon brake lock up

[NOTMAD]

First of all, Happy New Year to everyone.

I have been searching the forum for information on the Nomad Alcon front/rear set up and have read most of the threads (that I could find).

I have Upgraded to Alcons front/rear (from Alcons front and standard rear) and my brakes now lock up very easily if I stand on them hard. Previously they did not do this. I now have to really think about how I am driving the car and applying the brakes because if I stand on them hard, like you would in an emergency stop with a normal car (and I realise there is nothing normal about a Nomad) it will lock up very easily, almost to the point where it is dangerous.

I have read and understand that changing the set up moves the problem from having to apply a lot of force to get the car to stop to now becoming a tyre traction issues (as the Alcons are applying more force at the discs) but I am trying to establish whether other Nomad owner that have this set up are experiencing the same behaviour.

I have driven other lightweight and non servo assisted cars (Caterham) and they don’t exert this behaviour.

I have noticed that the Master Cylinder bore is 5/8 rear and 0.7 front. A bigger bore would reduce the pedal travel (as it’s pushing more oil to the caliper) but would require more pressure on the pedal. This would potentially bring the car into the brake feel range that I would expect…maybe.

So, I wondered whether anyone could confirm the Master Cylinder Bore size on their Alcon set up (it’s stamped in the cylinder above the pedals) and whether anyone has/is experiencing the same behaviour?

Thanks in advance

Ian

[John Scherrer]

Hello Ian

The Atom factory Option for upgrading the rear brakes to Alcon included replacing the rear 5/8 master cylinder to a 0.7 one.

I can’t speak for the Nomad but can’t see why it would be any different.

Another Nomad owner may be able to confirm the above.

[NOTMAD]

Hi John

Thanks for the reply. So to confirm the Atom runs with 0.7 cylinders for both front and rear?

This is interesting as I agree that there is no reason for it to be different on the Nomad.

It would be great if a Nomad owner could confirm what their Alcon set up is using?

Thanks

Ian

[John Scherrer]

Yes Ian, the Atom with the factory Rear Alcon upgrade should have 0.7 on the rear - So all 3 master cylinders are 0.7

(Clutch, Front & Rear Brake Circuits).

Do you have the remote brake bias option?
Have you tried moving the bias?

[NOTMAD]

Hi John

Thanks for the confirmation. Yep, I have the adjuster and have been playing around with it. I can easily make the fronts lock up then the rears or the rears first (promoting interesting oversteer going into roundabouts).

All this works fine and I get that the car is lightweight and will lock up (with no ABS) but my concern is the very little amount of force required to lock up.

My car currently set up the way it is needs a radically different mental approach to braking. For example, if needed to do an emergency stop then the reaction is to tread on the brakes quickly but with my car I would need to do this and NOT apply a lot of force as the car would lock. Locking up from anything above 40mph is not going to end well no matter how good you are at cadence braking.

My gut feel is that the bore size needs changing so that I can get the right amount of pedal feel (pressure applied) before lock up.

When I was running the standards on the rear the car did not behave like this. Changing to Alcons should give me better feel, reduce brake fade etc but the clamping force should not be too great that it induces lockup with minimal pressure. This is more a function of pedal ratio and Master Cylinder bore size.

I’ll have a chat with Steve at the factory but I’d still be interested if any other Nomad owners are running three 0.7 size bores as increasing the bore would help solve my issue (unless this is factory standard and all Nomads behave like this, but I can’t help but believe that is not the case).

Cheers

Ian

[Mutley]

Hi Ian,

I have a Nomad with Alcons. Must say I am a bit puzzled by your experience. It's not something that has been an issue for me at all. I would go as far as saying I LOVE these brakes. The principal reason is the amount of modulation possible. And for me this means the quite hefty boot that I find I require to get them to lock. In fact I think pretty much the only time they I have locked wheels on tarmac is when adjusting the balance front/rear.

I've only driven one other Nomad - and this was at a factory test drive. It also had Alcons and I don't recall them feeling any different.

So a strange one. Could pad material be a factor?

Chris

[John Scherrer]

Hello Chris,

If yours had Alcons on the rear fitted at the factory, then it will have the 0.7 size rear master cylinder.

When you have a minute, perhaps you could check the sides of the master cylinders and report back on the bore sizes?

Factory spec Alcons all round should have 0.7 stamped on both front and rear (and also the clutch master cylinder)

[Mutley]

So just checked (sorry no pic. the side panels make that tricky). L/H M/S is stamped 07, R/H MS is stamped 5/8.

[John Scherrer]

Thanks for checking Chris ..

In that case I'm stumped as I was expecting 0.7 on both front and rear brake master cylinders if you have factory fitted Alcons on front and rear wheels?

Time to ask Henry ..

[NOTMAD]

Thanks for checking this guys. I was hoping that the answer was 0.7 front/rear but as Chris (Mutley) has confirmed 5/8 rear which is this same as mine then my theory has been dispelled.

I will put some more miles on the car (weather permitting) and see if the pads start to bed in. If not then I might have to take a trip back to the factory and do a compare and contrast on their demo Nomad.

[Mutley]

Just to confirm - my Alcons were factory fitted as original spec.

Chris

[NOTMAD]

Thanks Chris.

PS. Seems like there are a few of us in the Hants/Surrey/Sussex area. Time for another hoon around Salisbury Plain? I didn’t have my car when the last trip happened.

[Mutley]

We should. I have GPX files from the last hoon, so I think we could create our own route this time. Optimum time is probably between the dust and the mud - although to be honest Salisbury Plan is a mixture of both almost any time of the year.

Where are you based Ian?

And who else would be interested in a Salisbury Hoon?!

[pdavery]

Yep, I would be interested ( based just south of Oxford) .
Re. Alcons , I have them factory fitted on my Nomad and don’t have a problem with them. You have to stamp on the brakes pretty hard to get the wheels to lock. It took a while to get the balance right so the fronts just locks first ,but it has always needed lots of peddle pressure.