30 replies to this topic

[robin]

A question to those that have the four pot fronts and two pot (front calipers on rear) on rear set up. been looking at the lotus cup cars with the four pot calipers and when at national meet seen people running four pots on front with two pots on rear, the question i have do these give better braking on this setup compared to having standard setup with pagids that i have at moment. I know you will not get brake overheating as fast is this the main advantage you get or is it a combination of better braking and less overheating. secondly if you fitted just four pots to front would this unbalance the car much or would it be fine to have larger discs and four pots on front and leave rears with pagids? thanks

[Nev]

This is a good question Robin, it would be interesting to hear some unbiased answers from someone who has actually done this. Also, how much heavier is the setup for front and back particularily on the rear as you would need a separate caliper for the handbrake presumably ?

[bunsenburner]

This is the set up I'm looking to move to, and yes you do need a separate caliper for the handbrake (assuming it will be on road and need an MOT).

[techieboy]

Also, how much heavier is the setup for front and back particularily on the rear as you would need a separate caliper for the handbrake presumably ?

Most that have moved the front calipers to the back have left the stupid fat Brembo's on as well, to act as a handbrake caliper.

Have a look at DW1's post about his experiences with larger calipers for the most unbiased review.

[Nev]

Thanks Techie, that was an excelent post by DW1.

[techieboy]

that was an excelent post by DW1.

Yep, I reckon that's probably the most informative and unbiased review I've ever seen on here.

[robin]

Ive read dw1 review a few times and is very good and informative but no one has done a review with this setup and having the front brakes on the rear, Would be nice to know as im sure a few people who are doing big bhp would be looking to upgrade possibly

[smiley]

I think Lee ran it for a while, and this guy: http://vx220.ukct.net/2potrear.htm

[FLD]

This is something my brain has been ticking over on. The rear brakes can be reamed out for a larger piston that would balance 4 pots on the front. I've got a spare rear that I'll look at one day! The other option is to put the fronts on the rear and use a spot caliper for the handbrake. Summat like this: http://www.rallydesi...roducts_id=8312 Unfortunately I cant comment on braking performance.

[The Batman]

im not sure if the 2 pots are needed at the back considering how much braking the rear actually does vocky has some nice figures/percentages on braking efficiency

[robin]

thought i would post some pictures of weights of calipers for comparisons
weight is in Ib. oz.
normal front ap caliper


four pot ap caliper


four pot caliper nount bracket weighs a ton


picture of two calipers side by side to show size


i dont have weight on ali belled discs or cheaper normal discs in 308mm size

so looking at weight its about 2Ib weight increase but with ali belled discs i imagine weight would be similar
to a normal front brake setup, would look to make the bracket in aircraft grade ali or titanium to cut weight as stupidly heavy for a bracket.

Edited by robin, 03 September 2011 - 04:42 PM.

[The Batman]

Get some proper 4 pots and no mounting bracket needed

[robin]

brackets wont weigh much once there made in titanium joe you get the lotus four pot calipers that junks was selling as thought these needed spacers or something or am i wrong on that?

Edited by robin, 03 September 2011 - 06:37 PM.

[The Batman]

nope no spacers needed with the lotus spec 4 pots:

[P11 COV]

I have the AP four pots and personally i dont think the breaking itself is any better. Maybe they will last better without overheating/brake fade but actual braking force doesn't seem any better.

[Dave E]

The tyres are the limiting factor to retardation. Feel and heat dispersal are another thing.

[Dave E]

Never liked the idea of the fronts and rears on the back because your adding a lot of unsprung weight. Those little dedicated handbreak calipers look a better solution.

[slindborg]

I have the AP four pots and personally i dont think the breaking itself is any better. Maybe they will last better without overheating/brake fade but actual braking force doesn't seem any better.

I could be wrong here, but I believe for the same pedal force you would get less clamping pressure with 4pots compared to the 2 pots due to the fluid having to move an extra pair of pistons which could have a bigger volume than the 2pots.

That aside, even with the same pad force as the 2pots the only thing the 4pots gain you is a bigger pad area to reduce the wear rate.

A pad the size of a pin head would give the same stopping 'power' as a pad the size of the disc (assuming both had the same leverage point. Just the pin head size pad would last milliseconds and the disc size pad would last longer than stonehenge

[bunsenburner]

I have the AP four pots and personally i dont think the breaking itself is any better. Maybe they will last better without overheating/brake fade but actual braking force doesn't seem any better.

I could be wrong here, but I believe for the same pedal force you would get less clamping pressure with 4pots compared to the 2 pots due to the fluid having to move an extra pair of pistons which could have a bigger volume than the 2pots.

That aside, even with the same pad force as the 2pots the only thing the 4pots gain you is a bigger pad area to reduce the wear rate.

A pad the size of a pin head would give the same stopping 'power' as a pad the size of the disc (assuming both had the same leverage point. Just the pin head size pad would last milliseconds and the disc size pad would last longer than stonehenge

I would have thought a larger pad surface area would have more grip, therefore more stopping power. The extra pressure required to apply the larger pad makes sense however.

[slindborg]

I have the AP four pots and personally i dont think the breaking itself is any better. Maybe they will last better without overheating/brake fade but actual braking force doesn't seem any better.

I could be wrong here, but I believe for the same pedal force you would get less clamping pressure with 4pots compared to the 2 pots due to the fluid having to move an extra pair of pistons which could have a bigger volume than the 2pots.

That aside, even with the same pad force as the 2pots the only thing the 4pots gain you is a bigger pad area to reduce the wear rate.

A pad the size of a pin head would give the same stopping 'power' as a pad the size of the disc (assuming both had the same leverage point. Just the pin head size pad would last milliseconds and the disc size pad would last longer than stonehenge

I would have thought a larger pad surface area would have more grip, therefore more stopping power. The extra pressure required to apply the larger pad makes sense however.

The basic calculation for friction dosent require Area to be included.
http://www.physlink....perts/ae140.cfm