243 replies to this topic

[dov]

what do you think of the bias valve option and four 2 pot ap's??

[JohnTurbo]

Should work!

[GeorgeBC]

Is the standard brake servo ok with now having bigger pistons on front and rear than it was designed for? Has anyone found a bigger brake servo that does the job? Im a little nervous with messing with the brake bias but since fitting 4 pots on the front the fronts lock too easily for my liking.

[JohnTurbo]

The 4 pot lotus option was designed to be used with a rear pad that has more bite. Running quad 38mm front and the dual 44.5mm rear does increase slave size too much really - my pedal is spongier than i'd like. The suggestion would be to fit a 1.1" subaru master cylinder, but this needs adapting to fit. - Joshua UXB's solution. This reduces the mechanical advantage both your foot an the servo has in a similar proportion to the increased slave area. I never got round to it, then I got used to the effect, and i don't lock wheels because I'm balanced - while everything is working at least! I suspect you'd be fine other than you've stuffed your brake balance as i described to you. I've read some real sh*t on the internet about brakes over the last few days and I plan to write an informative thread soon which is basically a 101 of friction and hydraulics. I know nothing of car setup but this is just physics. Ideal would be a radial mount front caliper with 30mm and 34mm leading/trailing pistons. You could fit that and use the stock rears with the same compound pads and all would be rosey!

Edited by JohnTurbo, 23 April 2013 - 05:53 PM.

[GeorgeBC]

Cheers John. All was rosie before i fitted the 4 pots so now they are on im just trying to get the balance right again. Guess ill suck it and see then try various pads.

[JohnTurbo]

Its not super simple - with sticky tires one could argue more front bias is a good thing - I do wonder if that's what lotus were thinking. (Ie more weight transfer to front axle under braking). You're not alone in being disappointed with bias after a 4 pot upgrade however. I'd bet RC5+ front and RC6 rear pads would solve your issues. - I'm not offering to finance them though!

[GeorgeBC]

Carbon lorraine have tried to kill me once and they wont be getting a second go at it. I know theres not been a failure for a while though. Im on brand new PF pads up front so im going to stick with them. Ill be mounting the 2 pots on the rear with PF and see what its like. If it tries to lock the rears ill get some pads with less bite for the rears. Ill see how i get on.

[JohnTurbo]

To be fair the FTR brackets with some cheap crap rear pads will probably work well.

[Kieran McC]

Carbon lorraine have tried to kill me once and they wont be getting a second go at it. I know theres not been a failure for a while though. Im on brand new PF pads up front so im going to stick with them. Ill be mounting the 2 pots on the rear with PF and see what its like. If it tries to lock the rears ill get some pads with less bite for the rears.

Ill see how i get on.

Have you tried cleaning the PF brake residue of the rims yet George LOL

Edited by kieranmcc, 23 April 2013 - 07:17 PM.

[GeorgeBC]

Carbon lorraine have tried to kill me once and they wont be getting a second go at it. I know theres not been a failure for a while though. Im on brand new PF pads up front so im going to stick with them. Ill be mounting the 2 pots on the rear with PF and see what its like. If it tries to lock the rears ill get some pads with less bite for the rears.

Ill see how i get on.

Have you tried cleaning the PF brake residue of the rims yet George LOL

Yep. Ruined my TD's and now my DTC's. Nothing a refurb wouldn't fix if it ever annoys me enough.

[Kieran McC]

Carbon lorraine have tried to kill me once and they wont be getting a second go at it. I know theres not been a failure for a while though. Im on brand new PF pads up front so im going to stick with them. Ill be mounting the 2 pots on the rear with PF and see what its like. If it tries to lock the rears ill get some pads with less bite for the rears.

Ill see how i get on.

Have you tried cleaning the PF brake residue of the rims yet George LOL

Yep. Ruined my TD's and now my DTC's. Nothing a refurb wouldn't fix if it ever annoys me enough.

I should have lert my lesson, Had the rims Power coated then put the same pads back on Donkey

[JimmyJamJerusalem]

To be fair the FTR brackets with some cheap crap rear pads will probably work well.

Hey John, so to clarify.... 4 pots up front on some kick as pads and 2 pots on shite rear pads will be a decent balance....? What about 4 pots on decent pads up front and Brembo's on the back with kick ass pads...?

Got 4 pots waiting to go on and want to get a decent balance straight off the bat.

[ArticMonkey]

To be fair the FTR brackets with some cheap crap rear pads will probably work well.

Hey John, so to clarify.... 4 pots up front on some kick as pads and 2 pots on shite rear pads will be a decent balance....? What about 4 pots on decent pads up front and Brembo's on the back with kick ass pads...?

Got 4 pots waiting to go on and want to get a decent balance straight off the bat.

Went on track yesterday with my new 4pots. I have Pagid rs29's up front and Pagid rs14s on rear (more aggressive). The balance was spot on for me (with RSR's fitted).

Tbh it's going to be abit of trial and error till someone finds the best combination.

[JimmyJamJerusalem]

To be fair the FTR brackets with some cheap crap rear pads will probably work well.

Hey John, so to clarify.... 4 pots up front on some kick as pads and 2 pots on shite rear pads will be a decent balance....? What about 4 pots on decent pads up front and Brembo's on the back with kick ass pads...?

Got 4 pots waiting to go on and want to get a decent balance straight off the bat.

Went on track yesterday with my new 4pots. I have Pagid rs29's up front and Pagid rs14s on rear (more aggressive). The balance was spot on for me (with RSR's fitted).

Tbh it's going to be abit of trial and error till someone finds the best combination.

Which calipers on the rear are you running?

[JohnTurbo]

Ok... 44.5mm front pistons (stock) and 28mm rear pistons (stock) give a 60:40 ratio of braking from front to rear. Brake area constant 2764, with a 5:1 slave/master ratio. If you use the "bolt on" ap calipers with asymetric pistons then you should be on 31.75mm/36mm leading/trailing 1008 + 1296 = 2304 ( and 784 rear) This is 16% more braking than standard - if you've gone for 308mm disks thats 21% more braking than standard. Balance = 64% front to 36% rear. This is why it upsets bias.

Edited by JohnTurbo, 23 April 2013 - 09:38 PM.

[JohnTurbo]

So basically Jimmy you are on it. To have the correct balance FTR brackets mate with a 38mm piston 4 pot...like the symmetric AP calipers, or my hispecs. If you wanted correct balance with the brembos you'd need 32mm piston four pots. (BTW AP 4 pots front and brembo rear gives a 5.88:1 ratio and so a slightly 'more assited/softer pedal)

Edited by JohnTurbo, 23 April 2013 - 09:37 PM.

[ArticMonkey]

To be fair the FTR brackets with some cheap crap rear pads will probably work well.

Hey John, so to clarify.... 4 pots up front on some kick as pads and 2 pots on shite rear pads will be a decent balance....? What about 4 pots on decent pads up front and Brembo's on the back with kick ass pads...?

Got 4 pots waiting to go on and want to get a decent balance straight off the bat.

Went on track yesterday with my new 4pots. I have Pagid rs29's up front and Pagid rs14s on rear (more aggressive). The balance was spot on for me (with RSR's fitted).

Tbh it's going to be abit of trial and error till someone finds the best combination.

Which calipers on the rear are you running?

Sorry, stock. I see no need ATM for the AP's on the rear. Just bare in mind I'm new to track and don't have a title like yourself.

Going out and testing combinations is going to be key. National brake testing laps?

[JohnTurbo]

Maybe someone should divorce this from poor Steffan's thread!

[dov]

Steffen, thx for the brackets, arrived safe and very well finished. John, I thought the elise brembo was a 36mm piston(sure looks bigger than 28) or is the VX smaller at 28mm, perhaps compensating for carrying more rear wieght? The audi motor is a few kilos heavier than the K series but shedding silencer and exhaust weight, I'm hoping engine package wont be vastly different. Corner weights should tell. Anyway, pleased with brackets

[JohnTurbo]

36mm it is. That is 60:40 though. The other calcs need reworking.