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Discussion Starter #1
Hi guys,

Since I'm preparing to hit the track later this week I did a little routine maintenance even though I thoroghly prepped the car two track days ago (a month). I thought I'd share what I found with the team and ask a question about it.

I re-bled the brakes in order to draw fresh fluid into the calipers and extract some of the burnt stuff even though I completely flushed the system a month ago (2 track days ago). I use Motus RBF 600. In the front calipers the fluid was a light carmel color and quickly ran clear with fresh fluid from the reservoir. In the rear. however, the fluid was pretty burnt and was rather black and coffee colored until I drew fresh fluid in. I have an '02 model that has the AP calipers on the front and the read calipers look positively wimpy compared to the fronts. Are the rear brakes underdimensioned for track use and therefore I'm cooking stuff back there? is there an upgrade that would allow me to ahve rear braking capability that is more balanced with the front (obviously "balanced" means not as large as the fronts but also not so small that they cook before the fronts do).

For good measure I thoguht I'd change the oil since I had my car on the lift anyway. At the track I prefer to shift at around 6500 RPM to keep the revs up and I've been getting 4 runs of about 25 minutes each, so keeping the oil fresh might be prudent. I changed the oil 2 track days ago as well and I realized as soon as I pulled the drainplug that I should have waited longer as there was lots of life left in the oil. It was a nice clear carmel color and clearly not needing to be changed out yet. I run Castrol Syngec (now Edge) 5W50. After each run I always let the car idle for a few minutes to let some oil circulate through the turbos before shutting down.

For tires I'm using the Nitto NT05's. The tires feel pretty good on the track and since I had the off the car to bleed the brakes I got a good look at them after some spirited use. I had several "earthworms" or rubber clinging to the inside of the rear rims (likey tossed up from the front) and a lot of black rubber smeared up the sides of the car (I asked previosuly about flares or splashguards for dirty roads, and the same would be pretty useful for keeping rubber spallter off the sides of the car. The rubber smeares do not wash off and require some wax and rubbing compound to remove, but that's no big deal. I didn't have a change to scrub in the tires much before my previous track day, so I was concerned I much chunnk them a bit on the track, but aside from some obvious surface melting they seem fine, and I like the softness that give me somce good tracktion (even though it makes a bit of a mess).

Hopefully some of these observations are helpful to folks that enjoy some track time with their car, and maybe some of you wil have thoughts on the rear brakes seeming to be underdimensioned and cooking the fluid.

Knut
 

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I'm running essentially the same brakes as you on my SE, though my front rotors are 28mm thick instead of 32mm as on your car. My rear brakes are the same, and I never have problems with burnt fluid, so I'm at a loss to explain your issue.

For the tire marks get a bottle of Mothers R3 Racing Rubber Remover, you will be astounded at how easy the rubber marks come off your paint.
 

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I use Castrol GTLMA DOT 4 and have not "burnt" it yet. Be sure to increase your tire pressures, you can go up to 36 PSI to prevent tire rollover. Watch the little dimples on the sides of the tires. You can also use an infrared temperature gauge. Before racing put your oil level up to the full mark. 3M makes a cleaner that removes rubber, grease, and tar easily. You will have to reapply your wax. You could also cover the front of the car with blue tape or clear plastic to reduce "road rash" to your paint. Double and triple check your wheel lug torque. If the track is a "right hander" all of the fuel will run into your left tank and you can run out at 1/2 tank. You might want to have an extra set of brake pads and enough tools to change them. You can wear out a set in one heavy day of track use. Racing shoes help because of the little pedals and their being so close together. Gloves are nice so your hands don't slip.
David Teitelbaum
 

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If I tracked my car, I would clear bra the whole thing including the windshield. It's not expensive to buy in bulk and I have learned the few techniques needed to apply it without having to pay through the nose on installation costs. Youtube and a couple of trial and error pieces and you'll be an expert.
 

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I am not familiar with the brake system on your car. That said I test and develop brake systems for a living. Are you sure the rear fluid was burnt and not just discolored from aluminum? Pick up some temp labels before your next track day and put them on your caliper body on the inboard side on the piston housing. I wouldn't get too worried unless you are getting over 150C or see heavy fade on track.
 

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Discussion Starter #6
Followup on fluids & track fun

Hi guys,

As a followup to some of the posts I thought I'd better clarify my observation on the fluids and my question.

I use Motul RBF600 for track use as it has a pretty good boiling point while being much cheaper than the SRF stuff which is like gold. While I use GTLMA for my other street cars, I don't consider it particularly attractive for track use as it has a boiling point that is so much lower than the Motul (around 450 vs 600).

I replaced the fluid with a thorough flush (drawing a couple extra bottles worth of fluid through the system) about 6 weeks ago and a couple drack days ago. The fluid I drew out of the front yesterday was the color of tea while the fluid from the rear was the color of coffee. The rear pads are loosing thickness a little faster than the fronts are.

The rear calipers are really tiny. With there being a little weight in the rear it strikes me as being disproportionately small compared to the fronts. I had good brakes for the entire day the last time at the track, but I'm not sure I'd notice that much whether the brakes in the rear were fading if the fronts were in good shape.

I use an IR thermometer at the track to check temperatures, but I check them after a cool-down lap so I don't get the true on-track readings. Temperatures are comfotably in excess of 150C all the way around right after coming off the track (did you really mean 150C?)

Knut
 

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So are you thinking your rear calipers are dragging and that's what's causing the pad wear and brake fluid discoloration?

It's possible since it's a 10 year old car afterall.

I am sure Lotus doesn't want too much braking in the rear so the car doesn't come around on people that like to trail brake.
 

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The Motul fluid you are using has 600* F boiling point as long as there is no moisture in the fluid. A smail amount of h20 in the fluid and the boiling point takes a nose dive. I suspect the discoloration in the rear brakes is either the "square rings" in the calipers deteriating or something in the ABS system.

I track my car now and then and push the limits and don't have any braking problems, fading, boiling fluid, or inconsistent action. I use Motul DOT 5.1 and Portorfield S4S pads. The wet boiling point of Motul's 5.1 fluid is more forgiving than the RBF 600.

The Lotus brakes (F/R) are undersized for very serious track running, but as designed they provide fairly balanced performance.

150 * C (302 *F) for rotor temperature is low if measured with temperature indicating paint.
 

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Discussion Starter #9
<snip>
The Lotus brakes (F/R) are undersized for very serious track running, but as designed they provide fairly balanced performance.
When Lotus switched to the AP front brakes to improve braking performance, did they make any change to the rears at the same time? If it started out pretty balanced and they improved the fronts, how did they maintain balance?

Knut
 

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It could be that the parking brake is adjusted incorrectly and dragging, causing excessive temperatures on the rear rotors. Or that the sliding single rear piston Brembo caliper is not sliding freely.

It also could be that the rear Brembo is undersized for your track and technique.

If you look at what Lotus did on the X180-R and Sport 300. they had nearly the same size front and rear AP Racing calipers and the same size front and rear rotors. Those cars' brakes are amazing on the track!

X180-R rear

X180-Front


I used to burn my original SE brakes (much smaller than your V8 AP Racing and Brembo combo) up at the local track all the time. I was also running Motul RBF 600, and I could still get the fluid boiling (pedal to the floor) or also the pads overheated (white ashen and cracked in half).

I made my own brake setup, copying the X180-R system. I used Brembo NASCAR (don't laugh) I have 4 piston monoblock aluminum front calipers with vented titanium pistons, and 4 piston aluminum rear calipers, also with titanium vented pistons. My rotors are 328mmx35mm (could have gone with 32mm) front, and 313mmx25.4mm rear. Both are floating.




There is NO fade with this setup! And the braking balance feels great, I can modulate very well, and the fronts lock up first. My car has a vacuum boosted non-ABS master cylinder btw. The X180-R has the GM Powermaster III ABS and no balance issues due to the larger rear brakes.

You would need an extra small rear caliper for a parking brake, since the race calipers don't do parking duty.

Here's more info about what I did.
http://www.lotustalk.com/forums/f164/brembo-racing-brakes-my-own-design-101381/
 

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Discussion Starter #11
Vulcan setup

The Vulcan setup looks more like it! The current rear caliper with pads the size of postage stamps simply don't seem to be in balance with the braking capability of the AP front setup on the '02 and later models.

I'll hit the track again tomorrow and I'll record some temperatures and wear in a more disciplined way, but beefing it up along the lines of the X180R setup seems like it would be a nice enhancement. Thanks for the link to your project -- looks sweet.

Knut
 

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When Lotus switched to the AP front brakes to improve braking performance, did they make any change to the rears at the same time? If it started out pretty balanced and they improved the fronts, how did they maintain balance?
The calipers stayed the same, but the rear rotors were made larger in diameter and thicker. The larger diameter increases the braking force.
 

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Discussion Starter #13
Two days on Ferodo DS2500 pads & grooved rotors

Hi guys,

Thought I'd follow up on the trackday brakes thread since I've had a few rounds over the last couple weeks.

I have been using Ferodo DS2500 pads on the front and from my first picture you can see what they look like compared with a new set after 2 track days (track days for me are usually about 100 minutes of track time spread across 4 sessions during the day with cooldown between sessions).

At the end of my last track day my brakes were making quite a bit of noise and causing a lot of vibration and my front rotors are grooved quite a bit so I pulled them off for resurfacing. You can see the grooving on the second picture. The high ridges correspond to the location of the vent holes on the rotor and the concentric low grooves straddle the holes. Not sure the cause, but maybe the portions of the disk that straddle the holes get hotter and more material gets removed.

Although the calipers stay pretty cool (I run with the thermal test strips on my calipers to keep an eye on them), things still get pretty hot. Notice in the last picture how the adhesive from the back of the Lotus logo badge has melted and run down and the whole badge has sagged in the middle of the wheel. My friend in his Corvette had the wheel balancing weights that had been attached with adhesive to the inside of his rim fall off and end up in a pile at the bottom of his rim the other day.

Hope you enjoy some of the pics.

Knut
 

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As your track technique improves you will use the brakes harder and harder. The Lotus V-8 is a heavy track car and if you are using the brakes as you should they will not last as you can see from your recent experience. The good news is you are getting better, the bad news is the car is not up to the extreme conditions you are imposing on it. Keep an eye on the dimples on the sides of the tires and make sure you have increased your tire pressures accordingly to prevent the tire from rolling off the bead of the rim. It also can't hurt to recheck the torques on the wheel lugnuts. It is also a good idea to flush the brakes BEFORE you track so you know the fluid is fresh and does not have any moisture in it to reduce the boiling point. I bet after that day you were tired but had a big grin on your face!
David Teitelbaum
 

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I would take off those center caps before going to the track. They are now around $40 a piece to replace.
 

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Okay, this is really strange but here goes. Have you checked the brake light switch for proper installation? If it's the same as mine then an improper installation will keep a bias for the brakes to drag in stead of releasing completely. The switch is inserted to a bracket and locked into place with a simple twist. If it was ever removed it can be put back in too far and it will actually cause the brakes to drag and heat up badly. To correctly install it simply have someone watch the tail lights and put it into the bracket just far enough to have the brake lights go out. Any farther can cause problems.

How do I know? I had another person who drove my car and they moved their foot in the wrong way knocking the switch loose. The brake lights stayed on and drained the battery. After finding that problem the switch was reinstalled and, not knowing, it was installed too far. That switch actually heated up the brakes until they bound. Readjust the switch and never a problem since.

Just a cheap simple thing to check.

(In fact, as the person who drove the car home didn't know what was going on as the brakes were binding the heat from the brakes actually warped the plastic center caps on the front wheels. They said the car just didn't seem to have the power it had on the way TO their destination.)
 

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The Ferodo DS2500 are great compromise pads for street and some track, but it looks like you are going fast/hard enough to over heat that compound. I would use 2 compounds, one for street and one for track, and probably switch to Ferodo DS3000 for the track...

Also as you've seen the drilled rotors are really no good for the track, either switch to solid or slotted rotors.

Can't tell from the photo, but it looks like you might have some pad taper as well?? If the pad is tapered, then you might have a problem with the slides having corrosion, or needing to be cleaned and lubricated.
 

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Discussion Starter #18
I have some DS3000 pads on order already to use on my next track day and if they are not very satisfying for road use I'll slip in the DS2500's for cruising around and run the DS3000's at the track only.

I'm not sure what rotor choices and availability is around for the fronts on the later model V8's (with the AP racing 320mm rotors). Do you have a suggestion for a source for alternate rotors? The factory ones look pretty darn expensive...

Knut


The Ferodo DS2500 are great compromise pads for street and some track, but it looks like you are going fast/hard enough to over heat that compound. I would use 2 compounds, one for street and one for track, and probably switch to Ferodo DS3000 for the track...

Also as you've seen the drilled rotors are really no good for the track, either switch to solid or slotted rotors.

Can't tell from the photo, but it looks like you might have some pad taper as well?? If the pad is tapered, then you might have a problem with the slides having corrosion, or needing to be cleaned and lubricated.
 
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