Disc brakes : heat cracks

[geartox]

On 25/09/2018 at 13:27, geartox said:

do you know if there is a repair kit (with new bellows) for the brake caliper ? I don't find any Lotus reference but maybe with APracing ?

 

nobody can help on that ? 

[vd9]

Normally you can get new deals and sometimes even pistons for the proper calipers (incl. upgraded ones). Ours are CP6600 fronts and CP6627 rear

Seals I'm sure are here - https://www.demon-tweeks.com/uk/a-p-racing-caliper-seal-kits-369688/ or in many other places

And here are the calipers - https://www.apracing.com/product_details/performance_upgrades/road_and_aftermarket_brake_calipers/4_piston_calipers/cp6600_family-130mm_mounting_centres-suits_ø330mm_disc.aspx

[geartox]

thanks for the answer.

 

CP6600 seems to have 38.1 and 41.3mm pistons
the seal repair seems to be CP4525-JK
for the CP6627 calipers I didn't find for the moment any informations.

but based on Lotus service guide section JM :

front pistons are 36.0mm and 31.75mm
rear pistons are 31.75 and 28.4mm

I mailed AP racing if they can help

[geartox]

Thanks to Matthew from AP racing for the answer 😃 :

- CP4527-EH kit for front

- CP4527-DE kit for rear

 

[CRM82]

Hi everyone,

I need an advise on my set of disks. My car is an Exige 380 Cup, and I still mount the original AP-Racing disks. The disk have nearly finished a second set of PF-08 pads (rear pads at 3-4 mm, front pads at 6-7 mm).

See the picture below (they have a lot of track days on them!!). I think the front disk needs to be replaced at the end of this set of pads (so in around 1-2, max 3 track days), while the rear disk perhaps can go for a third set of PF-08 before being replaced.

What do you think? 

Generally how many pads vs disks you consume before replacing the disks?

FRONT DISK:

 

REAR DISK:

[W31SSN]

I would be replacing those discs before doing any more track days..... the rears might get one more day but those fronts are toast IMO.

[vd9]

Micro cracks are not a disaster (unless reaching the edge of the disc), although there is a lot of them in the fronts. What is the remaining thickness of the disks?

As for the pads/disks ratio I can help with Exige yet - in my car with a very mixed use and original 1-piece cross-drilled disks I went through original pads, then DS2500, and now on DS Uno/DS1.11 with no signs of imminent replacement needs. But then original pads and DS2500 are not really aggressive pads.

Edited September 17, 2019 by vd9

[CRM82]

16 hours ago, vd9 said:

Micro cracks are not a disaster (unless reaching the edge of the disc), although there is a lot of them in the fronts. What is the remaining thickness of the disks?

 

 

I haven't measured the thickness - will do that over the weekend. However, the thickness should be OK (less than 2mm consumed - and you can see that the lines on the grooved disks are well visible). Cracks are there since a while, and are just getting more and more visible. I think on the front will replace the disk for sure. The rear however could potentially handle another set, also considering that they absorb only 30% of braking power. 

[NANO]

for your greater safety, for your best braking and for not having balance problems at the front and / or at the rear in case of strong braking (trackday) ... I, personally, would change all four of them at the beginning of the next season ... so you are "cool" and you can afford braking to the limit without thoughts ...

[KennyN]

As others have said, the fronts are done, but for peace of mind, I would be changing the rears too before driving too far or fast.

[CRM82]

Thanks to all for the suggestion.

Next question is: do you recommend to replace them with a set of original disks from AP Racing or perhaps switch to Komo-tec kit?
From what I see on Komotec website, a complete set would cost around 3700 Euro (including pads). Given that the pads are around 500-600 Euro, the 4 disks are at 3100 Euro. Do you know how much the original disks cost for comparison?

And foremost, which one is better/last longer? I am happy with the original AP Racing disks, they lasted long and always delivered good braking, but I don't mind to switch to Komo-tec if they guarantee longer duration and same or better performance.

As a note: I already use the PF08 pads on these disks - which is the same Komo-tec uses.

 

[GFWilliams]

Call Dave at Seriously Lotus, he’ll help to make sure you get the right discs.  I just changed to Alcons from him on the rear of my car and am very happy  

[Arun_D]

I echo what GF has said above, I use Alcons from Dave and am very happy. Straight swap rotors, retaining your original bells all-round (albeit I upgraded to fully floating on the front). Very convenient.

[W31SSN]

Has anyone gone for larger rear discs - and noticed any increase in braking performance. I’m still on the stock single piece rear discs but they are almost done. 
Will go fully float from Seriously Lotus. Just not sure if the bigger discs are worth it on the rear. 

[GFWilliams]

I recently changed from one piece to larger two piece discs from Seriously Lotus. I haven’t driven it on track yet, but there’s clearly more power to the rear brakes, and the balance front to rear now feels better.  The single piece discs can’t really handle track abuse with decent pads, so definitely worth upgrading if you do track miles.

[vd9]

On 19/09/2019 at 15:17, CRM82 said:

Given that the pads are around 500-600 Euro

Pads pricing makes no sense to me. Full set of DS Uno/DS1.11 (race compounds by a rather well respected manufacturer - https://www.ferodoracing.com/products/car-racing/racing-brake-pads/) is under £300.

Important thing to keep in mind with 2-piece rotors is that, in addition to better cooling and reliability, they are also significantly lighter than 1-piece. Being unsprung mass it has very substantial impact on performance (similar to lighter wheels).

I had a closer look at Seriously Lotus 2-piece disks (Alcon, which I've used extensively in the other car and am very happy with) and Komo-Tec (Performance Friction), and noticed the following things:

1) 32mm thickness in PFC vs 26mm (same as OEM) in Alcon. Thicker disks are better for longevity and heat resistance, but will be heavier

2) Dave states clearly that his set uses larger brake pads in the rear. This should theoretically be better for performance and longevity

3) Komo-Tec states that rear bells are handbrake compatible, can't see anything on this in Seriously Lotus. I'd check this as not all the 2-piece disks are handbrake-friendly

4) I read Komo-Tec website so that all the disks are fully floating, while in Seriously Lotus it is fronts only. Not a deal breaker, but fully floating are better for performance and longevity

For me item 3 would be a killer, so I'd check that first and, if it is fine, go with Alcon from Seriously Lotus. Even though it is probably marginally less high-performance (we're talking about excellent brakes either way here), I'd just rely on my good experience with Alcon.

[CRM82]

On 23/09/2019 at 21:02, vd9 said:

Pads pricing makes no sense to me. Full set of DS Uno/DS1.11 (race compounds by a rather well respected manufacturer - https://www.ferodoracing.com/products/car-racing/racing-brake-pads/) is under £300.

Important thing to keep in mind with 2-piece rotors is that, in addition to better cooling and reliability, they are also significantly lighter than 1-piece. Being unsprung mass it has very substantial impact on performance (similar to lighter wheels).

I had a closer look at Seriously Lotus 2-piece disks (Alcon, which I've used extensively in the other car and am very happy with) and Komo-Tec (Performance Friction), and noticed the following things:

1) 32mm thickness in PFC vs 26mm (same as OEM) in Alcon. Thicker disks are better for longevity and heat resistance, but will be heavier

2) Dave states clearly that his set uses larger brake pads in the rear. This should theoretically be better for performance and longevity

3) Komo-Tec states that rear bells are handbrake compatible, can't see anything on this in Seriously Lotus. I'd check this as not all the 2-piece disks are handbrake-friendly

4) I read Komo-Tec website so that all the disks are fully floating, while in Seriously Lotus it is fronts only. Not a deal breaker, but fully floating are better for performance and longevity

For me item 3 would be a killer, so I'd check that first and, if it is fine, go with Alcon from Seriously Lotus. Even though it is probably marginally less high-performance (we're talking about excellent brakes either way here), I'd just rely on my good experience with Alcon.

This helps a lot: thank you! I am quite oriented on the Komo-tec one at the moment, since I saw so many lotus with it.

I will ask a few more information before getting it. Point 3) is actually fundamental!

Another advantage of the KT kit would be that front and rear disks and pads will be fully identical, and it will be easier to manage replacements later.

 

On 17/09/2019 at 19:42, vd9 said:

What is the remaining thickness of the disks?

I measured: the front is 30 mm (so lost 2mm and should be replaced also because of that). The rear is at 25 mm (lost 1 mm, however probably will replace also it).

[vd9]

8 minutes ago, CRM82 said:

This helps a lot: thank you! I am quite oriented on the Komo-tec one at the moment, since I saw so many lotus with it.

I will ask a few more information before getting it. Point 3) is actually fundamental!

Another advantage of the KT kit would be that front and rear disks and pads will be fully identical, and it will be easier to manage replacements later.

I can't agree more. #3 is quite fundamental (this is based on the bell being aluminium, while for the drum hand brake you need something to work against the shoe pads - it is possible with aluminium, but not every single 2-piece break disks are designed for this) for a not purely race car. Beyond that Komo-tec option does look a (tiny little) bit superior and makes sense to be the choice for somebody without subjective preferences between Alcon and PFC (which are both with excellent reputation).

In terms of managing the replacements, brake pads are identical all around in both of the sets, disks are to be changed quite infrequently - so I'd say options are fairly equal on this.

8 minutes ago, CRM82 said:

I measured: the front is 30 mm (so lost 2mm and should be replaced also because of that). The rear is at 25 mm (lost 1 mm, however probably will replace also it).

Fully agree, 2mm down is a fully legitimate replacement. 1mm on 26mm is also not far from sorting it out.

Edited September 24, 2019 by vd9

[Arun_D]

@CRM82 easiest option for the rear is to just buy a new pair of rotors, and keep the original rear bells, since you already have 2 piece discs.

https://www.seriouslylotus.com/model/exige-s3-v6/exige-v6-332mm-alcon-rear-brake-disc-rota-s

Edited September 25, 2019 by Arun_D

[Seriouslylotus]

10 hours ago, CRM82 said:

This helps a lot: thank you! I am quite oriented on the Komo-tec one at the moment, since I saw so many lotus with it.

I will ask a few more information before getting it. Point 3) is actually fundamental!

Another advantage of the KT kit would be that front and rear disks and pads will be fully identical, and it will be easier to manage replacements later.

 

I measured: the front is 30 mm (so lost 2mm and should be replaced also because of that). The rear is at 25 mm (lost 1 mm, however probably will replace also it).

Point 3 Yes the Alcons have the handbrake drum as part of the bell

[drdoom]

What concerns are there regarding life of the bells? Has anyone had deterioration?

Cheers

[Bentzion]

All,'

If you really want better life from both your semi metallic brake pads and rotors you need to have them cryogenically treated..  Nothing else will give you the life span, period.  Proven, over and over and over again.. 

The one company that I found in the UK that does the rotors is:  http://www.frozensolid.co.uk/motor-sport/. (no affiliation!)  They seems to be OK.. 

NOT everyone does cryo the same.  Ask how long the hold time at -195c they treat at .  Should be min 12 hours.  Also ask if they temper at 175c after treatment (a must).

3X to 7x the life from the rotors.  Pads less BUT the cost to treat both should not be so bad.  Our prices stateside are: $50ea for rotors and $20 ea for set of pads.  

Whats treated in motorsports:  

Complete engines

Suspension components

driveline components and of course brakes.  

etc etc..  

Lots and lots of research and empirical data out there of this process..its been used in top secret US aerospace labs for many years.  F1, Motogp, Drag racing WRC.. amongst many others..

If you have any questions please don't hesitate to ask...

 

[Mattmahope]

This is a really interesting thread on the topic of brake options so thought I would add my own small contribution.

I have been running the OEM two piece discs with PF08 pads for a while now, which have performed very well for me on road and track. However the pads are now worn and the discs are well past their best. I have the heat cracks around the holes and the discs had developed a very pronounced lip around the outer edge, most likely from the aggressive pads. I’m going to replace the pads with PF08 again but going to swap to the EliseParts larger 343mm discs both front and rear:
https://www.eliseparts.com/shop/brake-system-ancillaries/343mm-v6-front-fully-floating-brake-discs/

https://www.eliseparts.com/shop/braking/brake-discs/v6-exige-343mm-brake-discs-with-handbrake/
 

Has anyone else tried these? They seem to be used on a number of race cars with good results and I am generally impressed with the parts and service from EliseParts.

I will report back with my findings in due course.

[Exx]

Can it help to sometimes clean the holes ?

[CRM82]

On 15/03/2021 at 13:25, Exx said:

Can it help to sometimes clean the holes ?

Yes, I did that on my old Movit installed on my Audi, but it is a very tedious and dirty work. Plus, if you do a track day you can't do until brakes are hot, and it is very impractical to do during the track day.