Brake pad advice- increasing rear bias

[KnifeySpoony]

My 420R has the uprated 4pot front calipers on vented discs with the standard solid rear discs/caliper. My understanding is that caterham fits this setup with a higher friction rear pad (Delphi 507, whatever that is) to help compensate for increase brake torque up front. It seems to me that my setup is still under-braked at the rear. I had pondered going to the uprated race-setup rear calipers/rotors but I was hoping to try a higher friction pad on the rear first to see if it improves things. 

 

Does anyone know what would be an appropriate pad that would be a step up from the delphi pads and be a good match for the 4 pot fronts? I am reading about the Ferodo DS3000 as a potential option, but I'm not sure how well it would match up.

 

Thanks

[sf4018]

I've been going through this the last 2 years. Here are the pads in play so far...

 

1. Delphi 507CP Brake Pads Rear - Use with 4 pot front brakes (caterhamparts.co.uk)

2. AP Racing Rear Brake Pads - set of 4 (caterhamparts.co.uk)

3. Pagid RS U.1163.RS42. [U.1163.RS42]Pagid Brake Pad Set, Caterham Seven, Ford Escort... (bestbrakes.com)

 

Delphi: Brake bias seems fine to me. It's supposed to line up with the uprated front brakes for what should be a decent brake bias. Wear is high for tracks with massive straight line braking zones (probably due to excessive temps).

AP Racing: Brake bias is ok too, but wear is massive. Don't like them. They are cheaper than the Delphis so I guess you get what you pay for.

Pagid: These are going on next, a real hail Mary. But they are massively expensive ($200+) so if they don't last 3+ times longer they'll be a non-starter too.

Ferodo: My fading memory when I researched this was that either it doesn't exist in this form or it's the AP racing one, but I can't remember for sure.

 

For this project though I'm coming to the conclusion that I have to either accept replacing the rear pads every 1 or 2 weekends or replace the whole rear brake system with a track rated one. I'm still holding out hope the Pagids will work out. My understanding is the track systems will not have the hand brake so will not be road legal, but I haven't researched that yet to confirm.

 

Engine braking is quite high on this car, maybe try dropping gears earlier when you brake.

[KnifeySpoony]

I have 5 track days on my pads - the rears looks like they can still do another couple I would guess. Definitely wearing faster than the front, presumably due to higher temps from using a solid disc. Fronts look new. I guess I will just have to do some experimenting of my own. Unfortunately few brands make pads that fit our standard rear calipers. Lots of choices on the front though. Does anyone know what the OEM pad is on the front 4 pots?

Edited February 13, 2022 by KnifeySpoony

[KnifeySpoony]

Looking at the images of the front pads for the AP racing 4 pots on CC parts site, it seems they are the ferodo DS performance. It is shown on the chart comparing to other Ferodo compounds. It seems it has similar friction to the DS2500 but with better cold bite for street applications.

 

[KnifeySpoony]

OK - I just pulled the trigger on a set of CL RC6 for the rear (size 4035). Seems to have a high friction like the DS3000 but don't need so much heat to start working well. The RC6 have a friction coefficient around 0.50. I can't find any data on the delphi, so it's crapshoot in terms of where my balance will end up, but we'll see what happens. Will report back once I've tested them.

[ashyers]

Have you used some rotor paint to see where your temps are?

 

Andy

[KnifeySpoony]

I have not. I suppose i should. 

[Croc]

 

The hard core race guys use Mintex 1144 compound.  But in the last year, a few of them were trialling the Mintex F2R compound and preferring those over the 1144 compound.  Apparently the F2R is harder to get warmed up and get in the right temp window but once there they stay there without fade.  I currently have the Mintexx 1144 on my UK Caterham and I like the brake balance on that.  

[KnifeySpoony]

I have seen the Mintex 1144 mentioned on blatchat threads - my understanding is that it is/was a popular choice for standard front (2 pot) calipers to help move bias more to the front for their cars which are overbraked in rear from stock, which is the opposite of my issue with the 4 pot fronts. However, if the mintex is a higher friction pad, I could try it in the rear I supposed. I placed an order for the CL pads, but were out of stock on essexparts, so I'm gonna go with the DS3000 after all.

[sf4018]

10 hours ago, Croc said:

 

The hard core race guys use Mintex 1144 compound.  But in the last year, a few of them were trialling the Mintex F2R compound and preferring those over the 1144 compound.  Apparently the F2R is harder to get warmed up and get in the right temp window but once there they stay there without fade.  I currently have the Mintexx 1144 on my UK Caterham and I like the brake balance on that.  

What’s the wear like on the Mintex?

[Anker]

I don't believe different compounds front and rear are a good solution to this issue. You are likely to get big variations in brake bias as the brakes heat up and cool down. A much better solution is to do a proper installation of two brake master cylinders, one for the front and the other for the rear connected by a brake bias adjustment bar. With that you can set a brake bias that works for you and get predictable behavior. 

[KnifeySpoony]

1 hour ago, Anker said:

I don't believe different compounds front and rear are a good solution to this issue. You are likely to get big variations in brake bias as the brakes heat up and cool down. A much better solution is to do a proper installation of two brake master cylinders, one for the front and the other for the rear connected by a brake bias adjustment bar. With that you can set a brake bias that works for you and get predictable behavior. 

Of course a dual master solution is best, but my understanding is this requires significant pedal box or even chassis modification to implement on a 7. The reality is that countless trackday enthusiasts and amateur racers mix/match pad compounds all the time to improve performance. Keep in mind that these cars (modern Caterhams) are coming from the factory with 2 different pad compounds from 2 different manufacturers, even. They perform adequately, but I am just looking for that last bit of braking performance.

[Croc]

9 hours ago, sf4018 said:

What’s the wear like on the Mintex?

 

I think they wear well.  A lot depends on driving style.  I don't use up my brakes, I do engine brake, but I also destroy tires (I use them to scrub speed) which reflects the v8 touring cars I learned to race which were always quite marginal on brakes.  I think I have 8,000 track miles on the current set in the UK Caterham but its time for some new front ones this year.  

 

 

8 hours ago, KnifeySpoony said:

Of course a dual master solution is best, but my understanding is this requires significant pedal box or even chassis modification to implement on a 7. The reality is that countless trackday enthusiasts and amateur racers mix/match pad compounds all the time to improve performance. Keep in mind that these cars (modern Caterhams) are coming from the factory with 2 different pad compounds from 2 different manufacturers, even. They perform adequately, but I am just looking for that last bit of braking performance.

 

Differing pad compounds front and rear is an old racers trick.  It was used on cars where adjustable braking was not permitted or possible.  Entirely valid approach to the problem and justified to try in your instance.  

 

However, if this does not work then the upgrade path is:

1) move to the race master cylinder (if you have not done so already)

2) upgrade to race rears

3) a brake balance adjuster set up is needed.  

[KnifeySpoony]

I already have the race master. I had actually considered doing the race rear rotor/caliper set up during my original build, but didn't for 2 reasons - first off it was backordered (and still shows as not available). Secondly, I was worried that I would fail inspections during the CA registration process without a handbrake. It turns out I could have slipped through without a handbrake without issue. If I end up chasing my tail trying to tweak pad compounds, I'll certainly try and do the big rear upgrade, assuming it is still available from CC.

[fastg]

I am confured, are you trying to increase or decrease the rear brake action? Could you not just put a proportioning valve in the brake circuit your trying to reduce the hydraulic pressure to?

 

https://www.summitracing.com/search/department/brake-systems/part-type/brake-proportioning-valves-and-distribution-blocks/product-line/wilwood-brake-proportioning-valves?SortBy=Default&SortOrder=Ascending&PageRollup=ProductName&GridPageSize=16&utm_source=bing&utm_medium=cpc&utm_term=brake proportioning valve&utm_content=Proportioning Valves&utm_campaign=General Terms M - R 

 

Graham 

[KnifeySpoony]

I am trying to increase rear brake bias, so a prop valve won't work for me.

[CarlB]

It will if you install an adjustable one for the front brakes. Proportioning valves do not work as well as two master cylinders and a balance bar. There isn't any difference in the pressure until a pre-set limit and then that is the the limit when you use a proportioning valve. A balance bar proportions the brake force independent of the pressure.

[KnifeySpoony]

Prop valve to limit front brake bias is considered a big no-no. I would never consider it.

 

 

[sf4018]

@KnifeySpoony is the car over rotating while trail braking?

[KnifeySpoony]

9 minutes ago, sf4018 said:

@KnifeySpoony is the car over rotating while trail braking?

Not at all. It will rotate with aggressive trail braking, but it takes a concerted effort. Nothing like my Exige that loved to back it in with even light trail braking. I'm ok with the level of rotation I'm getting, thought a little more wouldn't be bad either. I can always rotate the car on the throttle during exit phase. My main goal is to increase overall braking ability/shorten brake zones.