Geary now has Aluminum rears with 38 or 41 mm twin pistons and still has a parking brake.

http://www.eliseparts.com/shop/index...roducts_id=574 Nice - especially since they've managed to balance the slave cylinder to match the stock fronts.

ed Not a bad price, either. I wonder if these are ABS-compatible.

Ed It shouldn't make any difference as far as the ABS goes. The bias might have something to say about it. At the moment you need the GT2 rear hubs also sold on the site to fit these.

But there should be a direct fit option on the normal uprights in several weeks.

Bias-wise you can spec the caliper to worh either with the normal front brakes, so they are then identical to the stock rear ones (just a lot lighter) or if you fit their 4-pot front calipers at the same time then you can spec the bigger rear pistons to compensate for the increased front bias.

Bye, Arno. Hi Arno

I believe if you use these brackets the HiSpecs mount in the same spot as the original Brembos.

http://www.eliseparts.com/shop/index...roducts_id=584

Mark ...or if you fit their 4-pot front calipers at the same time then you can spec the bigger rear pistons to compensate for the increased front bias. Bye, Arno.
Isn't this the way to go and move the fronts to the rear? Sorry but very ignorant on this. Wouldn't you end up with significantly better braking, albiet with a little more weight in the rear, against doing the rears with no change to the fronts? Can you do the fronts and move the rears without plumbing in a bias valve? Isn't this the way to go and move the fronts to the rear? Sorry but very ignorant on this. Wouldn't you end up with significantly better braking, albiet with a little more weight in the rear, against doing the rears with no change to the fronts? Can you do the fronts and move the rears without plumbing in a bias valve?
You can move the fronts to the rear by just using the brackets. That's fine if you don't plan on using a parking brake. I use my car on track only and installed a hydraulic line lock for a parking brake. The stock Elise rear Brembos are both heavy and the rear is under braked. The problem with going to larger rears is that you would want a bias adjuster to limit the rear braking in the wet. When braking for a corner and the weight transfers forward, in the wet it takes less braking in the rear to lock up them up. You do not want that to happen. You can move the fronts to the rear by just using the brackets. That's fine if you don't plan on using a parking brake. I use my car on track only and installed a hydraulic line lock for a parking brake. The stock Elise rear Brembos are both heavy and the rear is under braked. The problem with going to larger rears is that you would want a bias adjuster to limit the rear braking in the wet. When braking for a corner and the weight transfers forward, in the wet it takes less braking in the rear to lock up them up. You do not want that to happen.
Actually for rain optimal is more rear brake...since the reduced grip leads to reduced weight transfer. Actually for rain optimal is more rear brake...since the reduced grip leads to reduced weight transfer.
So you're saying that you would use a bias adjuster in the dry to limit rear braking? Does the use of the 4 pot front caliper and new bracketry or the use of the OE front caliper on the rear change the "caliper offset" requirement of the wheels. Anybody experience any clearance problems here? So you're saying that you would use a bias adjuster in the dry to limit rear braking?
Ideally, for a given car and surface you'd like the front brakes to be able to lock slightly before the rears. This is stable, rear lock up is unsafe. Inlinr bias adjusters don't work well on the front of a car. If you tune the brakes just right for dry conditions, in the wet it will tend to be too front biased. Ideally, for a given car and surface you'd like the front brakes to be able to lock slightly before the rears. This is stable, rear lock up is unsafe. Inlinr bias adjusters don't work well on the front of a car. If you tune the brakes just right for dry conditions, in the wet it will tend to be too front biased.
Hey Stan

I agree completley about fronts locking first and NEVER using a bias adjuster on the fronts, but respectfully disagree about the rears. I'm going to ask some road racing buddies. I've pondered this for quite a while and really would like a definitive answer.

Mark Hey Stan I agree completley about fronts locking first and NEVER using a bias adjuster on the fronts, but respectfully disagree about the rears. I'm going to ask some road racing buddies. I've pondered this for quite a while and really would like a definitive answer.Mark
There already is a definitive answer. Also, if you want ideal f/r bias, you need to set it for the conditions.

Weight transfer is the key factor to understanding the matter...here is an excerpt from an article by an NSX guy:

"What Is Brake Bias?

[BSD] The following assumes ABS has been defeated. As it says in the user manual, ABS is a steering aid when braking, not a shortest distance stopping device.

The brake system, when set up properly, will apply pressure to the pads (front and rear) such that maximum braking is possible. To explain, the pads will grip the rotors according to the coefficient of friction (Cf) of the pads times the force from the pistons/calipers. As force is added, braking force is also added.

As the car brakes, weight will transfer to the front wheels. This increases the amount of traction the front wheels have and decreases the traction in the rear. This is why the front pads and calipers do more work than the rears (and are a different size). The stock proportioning system allows for a certain ratio of the brake pedal force (after booster) to be sent to the fronts and a certain pressure to the rears. I am assuming there is a stock non-adjustable brake bias (proportioning) system on an NSX.

Even when weight shifts to the front of the car, the front tires can only grip so much (according to the tires' Cf with the road and the weight on the tires). At that point, the rear brakes should also be gripping the rear rotors at the maximum they can without causing the rear tires to lock up. Both ends should max out the tires at the same time. The proportioning system is how you accomplish this.

Assuming the stock system is set up perfectly for the stock pads and stock tires means that the stock system (non-adjustable) is _not_ set up correctly for different tires or different pads.

Let's say we put on R1 race tires front and rear which have more grip than the stock tires. Now, as the car brakes, weight shifts to the front and the tires grip the road and slow the car. However, the front tires at the previous maximum braking level are not doing as much braking as they _could_ do. If you continue to press the brake pedal, both ends will do more and more braking and more weight will shift to the front of the car. This gives the front even more grip and the rear even less. Now, the rear brakes will be doing too much for the tire grip and the rear tires will lock up first. When you put on stickier tires, you want more brake bias towards the front.

The same argument, in reverse, works for running in the rain or on other more slippery surfaces. When braking in the rain, the fronts just can't get enough grip to brake the car as hard as it can in the dry. This means less weight shifts forward (less grip up front) and more weight is left in the rear (more grip in the rear). In this case, the fronts lock up first. That means more brake bias to the rear is appropriate.

Hope this makes sense." To get crazy with rear brake weight the Aluminum rotors off of the first S1 Elise might fit. Even in the rear there might be too much heat though since Aluminum rotors like to be cool. They must have been adequate for fairly hard street driving even in the front since they were the standard rotors. I tried Aluminum rotors on a 911 turbo years ago. The rears held up fine even with heavy track use but the fronts could not take the heat. The fronts warped and ate pads like crazy. That car is 700 pounds heavier than the Elise with more than twice the power and only 1/2 inch larger rotors so rears might hold up on the Elise. There already is a definitive answer. Also, if you want ideal f/r bias, you need to set it for the conditions.

Weight transfer is the key factor to understanding the matter...here is an excerpt from an article by an NSX guy:

"What Is Brake Bias?

[BSD] The following assumes ABS has been defeated. As it says in the user manual, ABS is a steering aid when braking, not a shortest distance stopping device.

The brake system, when set up properly, will apply pressure to the pads (front and rear) such that maximum braking is possible. To explain, the pads will grip the rotors according to the coefficient of friction (Cf) of the pads times the force from the pistons/calipers. As force is added, braking force is also added.

As the car brakes, weight will transfer to the front wheels. This increases the amount of traction the front wheels have and decreases the traction in the rear. This is why the front pads and calipers do more work than the rears (and are a different size). The stock proportioning system allows for a certain ratio of the brake pedal force (after booster) to be sent to the fronts and a certain pressure to the rears. I am assuming there is a stock non-adjustable brake bias (proportioning) system on an NSX.

Even when weight shifts to the front of the car, the front tires can only grip so much (according to the tires' Cf with the road and the weight on the tires). At that point, the rear brakes should also be gripping the rear rotors at the maximum they can without causing the rear tires to lock up. Both ends should max out the tires at the same time. The proportioning system is how you accomplish this.

Assuming the stock system is set up perfectly for the stock pads and stock tires means that the stock system (non-adjustable) is _not_ set up correctly for different tires or different pads.

Let's say we put on R1 race tires front and rear which have more grip than the stock tires. Now, as the car brakes, weight shifts to the front and the tires grip the road and slow the car. However, the front tires at the previous maximum braking level are not doing as much braking as they _could_ do. If you continue to press the brake pedal, both ends will do more and more braking and more weight will shift to the front of the car. This gives the front even more grip and the rear even less. Now, the rear brakes will be doing too much for the tire grip and the rear tires will lock up first. When you put on stickier tires, you want more brake bias towards the front.

The same argument, in reverse, works for running in the rain or on other more slippery surfaces. When braking in the rain, the fronts just can't get enough grip to brake the car as hard as it can in the dry. This means less weight shifts forward (less grip up front) and more weight is left in the rear (more grip in the rear). In this case, the fronts lock up first. That means more brake bias to the rear is appropriate.

Hope this makes sense."
Thanks Stan

It's one of those things that if I can't see it or touch it I don't understand it!

Mark Stan, you're right. Here's another explanation:

http://www.stoptech.com/tech_info/wp...formance.shtml Hi Arno

I believe if you use these brackets the HiSpecs mount in the same spot as the original Brembos.

http://www.eliseparts.com/shop/index...roducts_id=584

Mark
Unfortunately not. I asked Geary of Eliseparts about that bracket.

Those brackets are for the rear S1 aluminium upright to convert to radial mount. On the S1 aluminium uprights you always use a similar 'extention' piece to fit the normal Brembo's.

On cast iron uprights (later S1 and S2) the mounting points of the Brembo's are integrated into the upright.

Problem is that these mounting points are too far outward towards the outer edge of the brake disk already to fit a bracket AND then bolt on the calipher. At least if you retain the same size brake discs. Bigger discs would give more space.

Geary looked into this and he now has a new design for the rear brakes that bolts directly to the existing brembo connection points (aka. not a radial mount) and fits the normal brake discs.

Should be available in a while..

Bye, Arno. I have “briefly” read the posts and agree with “Stan”.

I cannot log on as I am not a member but could you post this for me.



I have “briefly” read the posts and agree with “Stan”.

We have tested the calipers on several types of car with ABS inc the VX220 and UK MK2 Exige (both have v similar ABS systems)

The good news is the Lotus has a 4 channel ABS system so it makes no odds to our rear calipers, we have tried and achieved (with piston sizes) to keep the front to rear ratio similar to OE without having to resort to changing the master cylinder.(I feel we have actually improved the ratio)

We have several cars out there running these without a bias valve but I would always recommend one especially if you are racing/tracking the car for the reasons Stan has mentioned.

I am not sure if I have “misinterpreted” an above post but the Elise (in fact none of the exige/Elise/340R etc) were fitted with a brake proportioning valve, I presume Lotus (quite rightly) felt there was no need on a mid engined lightweight car.



Cheers

Geary Powell (Eliseparts.com)