Lotus Elan

The ultimate Elan brake set up

PostPost by: Maulden7 » Mon May 30, 2016 3:50 pm

So, .... what are views on the above?

Let me set some context first.

My S2 Elan is fully modified suspension wise (all from TTR) & hangs on famously. Around a 145bhp engine (John Smurthwaite) with TTR manifold & exhaust system. Close ratio gearbox. Quaife LSD. TTR solid drive shafts. Double anti roll bar. 5.5in Minilite wheels with 175/60 H rated Yokos. +2 front discs & calipers with EBC green stuff front pads / black stuff rear pads on standard calipers (no servo of course - caliper dust shields removed)

Car is fully road legal & used for sprints / the odd track event / day - I drive it to all events - no trailer (as modified now I am fine for "production class" entries for most events)

Last Saturday at Castle Combe (the Club Lotus track day) - in only 4 x 15 min sessions over the day - the brakes went off, with loss of feel & increased pedal travel, to the extent that I didn't go out again (though there was plenty of track time still available - the pedal came had come back by the next day when I left the hotel) As always I did push the car very hard, as the drivers of all but an Evora & a couple of Exiges can testify. Also, the recently run in new front brake pads deposited more brake dust on the front wheels than I've ever seen before?

Even from cold the brakes lack "bite".

Hub "run out" is fine - handling is great - if the car does not go as quickly as it should then that's "driver error" & not the cars' fault!

I am very interested in advice as what I can do to improve the braking generally - thanks for any thoughts.

Mintex pads / cooling ducts ..... but how to improve the "bite"????

Dave M.
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PostPost by: bill308 » Mon May 30, 2016 4:24 pm

Hi Maulden7.

Did you flush the brake fluid with new prior to the track event and if so what fluid did you use?

Bill
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PostPost by: Maulden7 » Mon May 30, 2016 4:56 pm

All new brake fluid Bill - Motul RBF 66 (racing brake fluid)

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PostPost by: bill308 » Mon May 30, 2016 10:56 pm

Hi Dave.

So the easy answer of contaminated brake fluid (high moisture content) is unlikely. Still, did you push enough fluid through to ensure a thorough flush?

You posted that caliper dust shields were removed. Did you mean the disc dust shields?

Lots of folks use +2 calipers and discs on the 2-seaters and report good results. I wonder if you have a mismatch between the front and back. The +2 caliper bores are bigger as are the discs. Together with the appropriate +2 caliper brackets, the fronts should be a lot more powerful, perhaps leading to an unacceptable unbalance where the rears are doing very little. I did not see any mention of increased dust production by the rears. Were they working hard too?

With a brake setup and experience like your yours, I would consider different pad combinations. I have no experience with the EBC pads so can't comment on their compatibility for semi competition use, but maybe it's time to look at higher heat tolerant alternatives. Does anybody use EBC stuff for competition?

For competition, the coefficient of friction (COF) at high temperature would seem to be the important thing, providing you know you are not boiling water in the brake lines. You want the fronts to do most of the work because of weight transfer, but the rears have to pitch in too, maybe 25 percent or so. Do you have a means to balance front to rear brake bias or do you depend just on pad selection? Maybe try a softer or higher coefficient of friction rear pad. If the car acts squirrelly when on the brakes hard, then perhaps the rears are locking up and you make adjustments to a harder pad or one with a lower COF.

In the end I have no magic answers. For my new car, I've selected special AR's with a special 2-1/8 inch bore, like the +2 caliper, but a lot lighter. For the rears, NR's, initially without the emergency brake hardware. The front AR's will be pared with shaved +2 discs and special caliper brackets. The rear NR's will use the standard rear discs and will bolt directly to the bearing carrier. I will pare these pieces up with a balance bar pedal system that is cockpit adjustable. If necessary, the master cylinders can be replaced for major balance adjustments. I asked Tommy Smith at DBE to select appropriate front and rear pads for me.

Bill
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PostPost by: rgh0 » Tue May 31, 2016 11:17 am

Your problem is almost certainly the pads you are using. With Plus 2 front calipers and new racing brake fluid the actual brake system apart from the pads should be fine. I run similar racing fluid and standard Elan calipers and never have any problem with brakes in races even on tracks with very heavy brake demands.

When I was still driving my Elan on the road as well as racing I tried many road suitable pads including EBC GreenStuff and ended up using Ferodo DS2000 as the best i could find for racing plus be usable on the road. The equivalent pad these days i think is DS2500. However I still found high temperature fade occurring in the front pads. Incidentally I found the dust from the EBC's to be very corrosive of brake caliper components when used heavily and getting them hot.

I started using Ferodo DS11 pads and their locally made equivalent which was called "Blackflash" Soon after these became no longer available due to their asbestos content, I tried a range of competition pads over a number of years. After many problems with high temperature fade , excessive pad wear and cracking or excessive disk wear or excessive cost I settled on Hawk Blue 9012 compound for the front and TTR supplied Ferodo F6R compound for the rear.

The Hawk pads have good grip with a high coefficient of friction and good pedal pressure modulation over a wide temperature range and last a long time and dont wear the disks excessively and are relatively cheap. However they work as i understand it based on what is called "film transfer technology". This deposits a thin film on the disk from the pad when the pad is hot and it is the interaction between this film and the pad that gives its low wear characteristics. If you use these pads on the road they do not create the film as they do not get hot enough and while they still work very effectively the disk wear rate is very high as they are very abrasive at low temperature on a clean steel disk.

The rear pads do not get to anywhere near the front pads temperature on the track and you need a pad that works well at lower temperatures but has similar initial grip and modulation to the front pads to maintain brake balance. If using the standard front calipers you also need a lower coefficient of friction rear pad to balance up the braking on the track with modern sticky tyres ( or your need fit a balance bar or rear pressure limiter). The TTR F6R pad meets all these criteria for me without a balance bar or rear pressure limiter and they last well and dont wear the rear disks. There only downside is their high cost.


Given all the above my recommendation would be that you try Ferodo DS 2500 front pads and if they are insufficient on track days you change your pads when you get to the track for a suitable racing pad like the Hawk Blue 9012 and change back at the end of the day to drive home. You can probably get away with standard rear pads unless you have a brake balance problem

cheers
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PostPost by: Maulden7 » Tue May 31, 2016 12:20 pm

Thanks for all the posts chaps, much appreciated.

I've just had the front wheels off the car (had to get under it anyway as I had lost my speedo drive - the 90deg fitting on the gearbox end had come undone & dropped out - wish all problems were solved that easily!)

To answer a few questions. The brakes were bled 3 times with the Motul fluid after replacing the braided hose from the master cylinder - very confident that all the fluid in the system is new. Yes, disc dust shields removed. There was a normal amount of brake dust on the rear wheels, so they seem to have been doing their bit. No bias adjustment available. No brake lock up problems. After coming off track on Saturday the front calipers were very hot - the rears were just hot.

The wear on the EBC Greenstuffs (new pads - just run in on the road) was amazing, at that rate they would be done very quickly (no wonder there was such a lot of brake dust on the front wheels!) One of the pads was actually cracked across the material face, & all the others looked very "cooked" - actually almost black around the middle where the caliper acts.

I am wondering if I received an incorrectly marked / boxed set of pads, & they weren't Greenstuff material at all? I've used Greenstuffs for a long time & they have never performed so badly before, or ended up looking like these pads do.

So, the comments about a pad issue seem to be spot on. I've just spoken with TTR & their current recommendation for my circumstances / use are Mintex 1144 material, & I'm going to give them a try. My next event is not for a month, & I'll report back after this.

Thanks again for all the advice.

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PostPost by: rgh0 » Tue May 31, 2016 12:47 pm

Your Greenstuff pad state description is similar to what I observed when I used them seriously on the track. The Mintex 1144 I never tried but are similar to the Ferodo DS2500 as i understand it so should be much better than the EBC

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PostPost by: Maulden7 » Tue May 31, 2016 5:37 pm

Thanks Rohan.

I've just looked at the pads using a magnifying glass, & apart from the obvious crack across the full width of one, all the others have a number of long hairline cracks in the pad material that are not immediately obvious when just viewed by eye in the garage.

Thank goodness that I took these pads off, as they may well have broken up & failed completely under hard braking at any time!

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PostPost by: nmauduit » Tue May 31, 2016 9:30 pm

I have experienced brakes going out (pedal to the floor), with green EBC on Girling 14 last year. I thought this was the result of brake fluid boiling, too much braking being an obvious beginner's mistake... Then I replaced the front with Girling 16 with Pagid RSH3 this year, and was a bit more attentive to brake behavior evolution lap after lap : after very crisp feeling at first, I did feel some fading (brake being a bit less efficient) at some point, and even an other episode of "pedal to the floor" after pushing further. This was all with new brake fluid, not racing though but silicone (260?C boiling point), and with dust shields on. Back to the stand I almost burned myself just touching the wheel nut.

My conclusion so far was that I should avoid to abuse brakes but rather use them like a precious resource, or the heat will get to the fluid via the pistons eventually.

I have seen that some people offer titanium shims, that could possibly add thermal resistance between the pads and the pistons : any experience with that?

I have also considered modifying a set of spare brake shields to bring some fresh air to the disks, but have not gone further than toying with the idea so far, esp. reading that elans brake well : most likely I should learn how to brake first...
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PostPost by: StressCraxx » Wed Jun 01, 2016 3:40 am

nmauduit wrote:I have experienced brakes going out (pedal to the floor), with green EBC on Girling 14 last year. I thought this was the result of brake fluid boiling, too much braking being an obvious beginner's mistake... Then I replaced the front with Girling 16 with Pagid RSH3 this year, and was a bit more attentive to brake behavior evolution lap after lap : after very crisp feeling at first, I did feel some fading (brake being a bit less efficient) at some point, and even an other episode of "pedal to the floor" after pushing further. This was all with new brake fluid, not racing though but silicone (260?C boiling point), and with dust shields on. Back to the stand I almost burned myself just touching the wheel nut.

My conclusion so far was that I should avoid to abuse brakes but rather use them like a precious resource, or the heat will get to the fluid via the pistons eventually.

I have seen that some people offer titanium shims, that could possibly add thermal resistance between the pads and the pistons : any experience with that?

I have also considered modifying a set of spare brake shields to bring some fresh air to the disks, but have not gone further than toying with the idea so far, esp. reading that elans brake well : most likely I should learn how to brake first...


I don't think silicone brake fluid is intended for hard use on track days. A good name brand DOT4 (Castrol, Motul, etc.) fluid is fine. Some have used stainless backing shims behind the pads to reduce heat transfer. The brake pads have a usable temperature range. If you exceed the temp rating the friction level falls off. Inspect your rotors carefully, if they show having radial cracks in the brake surface or show signs of bad surface, replace them. I had my rotors cryo-treated about 10 years ago when I replaced them. They still look close to new.
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PostPost by: rgh0 » Wed Jun 01, 2016 9:55 am

The best methods I know about to limit heat transfer from the pads and disks to the calipers is as follows

1. Use a castellated piston so that the contact area between piston and pad is minimized.
2. Use cooling ducts to direct cool air onto the disks and pads to keep them cooler
3. Use an insulating material behind the pad to insulate it from the piston. You see these bonded onto the back of some pads.

However with good quality DOT5.1 fluid and pads suited to the use I have not found any of these to be critical

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PostPost by: Maulden7 » Thu Jun 02, 2016 4:30 pm

New Mintex pads received & fitted earlier today, so I'll run them in on the road, & then see how they go at my next event.

The pad material is split in the middle with a small gap, as opposed to other pads I've used where the material has been a solid piece.

The front wheels took a lot of cleaning to get rid of the brake dust ..... now silver again!!

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PostPost by: Maulden7 » Mon Jun 06, 2016 6:07 pm

Apologies for resurrecting this thread when I've got nothing new to add yet, but anyone any experience with titanium inserts placed between the front caliper pistons & the brake pads?

A mate of mine is very active in drag racing - serious stuff - a nitrous fuel "funny car" - & stop their car from circa 250mph to around 90mph using the chute, but then use a "handbrake" on the rear wheels to take off the rest of the speed. The wheels are fitted with 4-pot road calipers, but they use titanium inserts to minimise the heat transference from the pad to the caliper. Apparently this not only improves the braking effect, but also extends the life of the pads significantly, & protects all the caliper rubber components as well.

Titanium is a poor metal for transferring heat, & despite the inserts being quite thin, they are seemingly very effective. Available for the Type 16 caliper from the USA, & the front set will cost circa ?100 all in (including UK taxes)

Any thoughts?

Thanks - Dave
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