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Discussion Starter #1
I’m guessing this question has been asked before but I couldn’t find the answer in a simple forum search.
The brakes on my 08 Exige S240 are good but are biased too heavily to the front which makes the car very sensitive to road undulations when braking hard on the road. The car gets used mostly for spirited road drives, I would prefer not to have to fit a twin master cylinder bias system, would like to keep the standard ABS but would like to move the bias more to the rear. I would consider forgoing the servo assistance if necesssary but would appreciate ideas on how to improve the front rear brake balance.
Thanks in advance.
 

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I ran the Porterfield R4 up front and R4-1 in the rear last season with no problems. The rear is a vintage compound and has significantly more friction than the regular R4.

That said - I'm swapping to 2-pot rears next season!
 

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Curious to see how you solve this as I’m having the same issues.

They stop very well if the surface is completely smooth, other wise it feels like I’m driving a go kart again.

My bigger issue is the longer pedal travel though. Do you have some what seems like freeplay at the top of the pedal? I still need to research and see if they changed the MC size for the 240 versions due to the larger calipers.
 

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This is a road use only situation? What pads are you using or have you tried? My first thought would be, try some different pads. On the information given it seems crazy to me to consider bias bars and caliper swaps.
 

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This. I ran different compounds F/R (Carbotech XP8 and XP10's) on my Exige. I didn't have the AP Racing Calipers, but I felt the setup was better for my driving style.
I can recommend the above as well. We have been running this with success for years with both Carbotech and G-loc. BTW: Carbotech & G-loc are made at the same factory. We stock G-loc.

Experimenting with pads is the lowest cost solution to your issue. I would avoid mixing compounds from different manufacturers...we tested this on track and it was a fail. :eek:
 

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This. I ran different compounds F/R (Carbotech XP8 and XP10's) on my Exige. I didn't have the AP Racing Calipers, but I felt the setup was better for my driving style.
There's a big difference in the braking bias and feel with the AP over the stock smaller calipers. It seems like it's going to take more than different compounds to achieve more balance, which is most likely the Front Brake Relocation
 

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There's a big difference in the braking bias and feel with the AP over the stock smaller calipers. It seems like it's going to take more than different compounds to achieve more balance, which is most likely the Front Brake Relocation
Right, so instead of limiting the thought to be staggering pads, get pads that have less bite all together. Full disclosure I've not driven a car with 4 pots up front, but I have never seen this complaint before and it seems unlikely that brake system changes are required on a street driven car (assuming the system is working properly).

Also, afaik the brake MC is the same across all cars with 2zz, regardless of brake package. I'd think that putting larger 2 pot on the rear, with 4 pot already up front, would change the brake pedal.
 

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Everyone's read that article, and in my opinion it really only applies to tracked cars or competitive situations. Rewind time on this forum to ten years ago and you'd find folks saying to upgrade to bigger calipers on the front and how great it was. There were people winning with 4 pots up front and sliders on the rear. Ralph at V2's approach was to have less aggressive pads on the rear (caveat: i think he had 2pot up front). I was so convinced that I purchased a set of 4 pots, but ultimately never fitted them.

Its only been in recent years, long after the end of US production, that thoughts about pushing the bias reward moved out of the fringe and gained traction. Look at reviews of s240 when they were new. Most either don't mention the brakes, or have a positive remarks: Lotus Exige S | Evo

But.... if the OP wants to go down the rabbit hole, have at it!
 

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So the weird thing is with a streer car you want more rear bias than a track car. Street tires have less grip so you'll have less forward weight transfer.
 

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Everyone's read that article, and in my opinion it really only applies to tracked cars or competitive situations. Rewind time on this forum to ten years ago and you'd find folks saying to upgrade to bigger calipers on the front and how great it was. There were people winning with 4 pots up front and sliders on the rear. Ralph at V2's approach was to have less aggressive pads on the rear (caveat: i think he had 2pot up front). I was so convinced that I purchased a set of 4 pots, but ultimately never fitted them.

Its only been in recent years, long after the end of US production, that thoughts about pushing the bias reward moved out of the fringe and gained traction. Look at reviews of s240 when they were new. Most either don't mention the brakes, or have a positive remarks: Lotus Exige S | Evo

But.... if the OP wants to go down the rabbit hole, have at it!
No offense, but you haven't driven one, and the example you gave didn't have the four pots either. It would be cool to hear from owners who have experience as there's quite a bit of 'thought' on what works and what doesn't on the forum.
 

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@arsenal I have a S260 with the 308 rotors/4 pot calipers front and 288 rotors/1 pot calipers rear. What @jds62f has stated is basically spot on. He has also ridden with me on the track and I believe he will tell you that I do push my car.

Now, auto-xing the car, I never really noticed the brake bias being a real problem. The first time I took the car to the track was a totally different experience. You had to be off the brake before corner entry or the car just washed out. So, as Jeff stated, down the rabbit hole I went except that I had previous racing experience with cars that had brake bias adjustability. I tried different pads, front and rear. Not enough since typically this is just a fine tuning adjustment. Next, I picked up a set of front two calipers and mounted them on the rear. Better but you still could not trail brake the car. Next was to find a brake bias system which I located one over in the UK. I believe I was probably one of the first to go this way in the US. After going to aftermarket calipers and master cylinders a couple of times, I found the right combination.

My question to the OP, @mlc66 "Is feeling present in a straight line or when you are turning into a corner". If it is in a straight line, changing brake bias is NOT going to change the feel. If you are feeling a darting of the front when heavy braking in a straight line then you have an alignment or a shock problem.

Later,
Eldon
 

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@arsenal I have a S260 with the 308 rotors/4 pot calipers front and 288 rotors/1 pot calipers rear. What @jds62f has stated is basically spot on. He has also ridden with me on the track and I believe he will tell you that I do push my car.

Now, auto-xing the car, I never really noticed the brake bias being a real problem. The first time I took the car to the track was a totally different experience. You had to be off the brake before corner entry or the car just washed out. So, as Jeff stated, down the rabbit hole I went except that I had previous racing experience with cars that had brake bias adjustability. I tried different pads, front and rear. Not enough since typically this is just a fine tuning adjustment. Next, I picked up a set of front two calipers and mounted them on the rear. Better but you still could not trail brake the car. Next was to find a brake bias system which I located one over in the UK. I believe I was probably one of the first to go this way in the US. After going to aftermarket calipers and master cylinders a couple of times, I found the right combination.

My question to the OP, @mlc66 "Is feeling present in a straight line or when you are turning into a corner". If it is in a straight line, changing brake bias is NOT going to change the feel. If you are feeling a darting of the front when heavy braking in a straight line then you have an alignment or a shock problem.

Later,
Eldon
I think we're saying the same thing, different pad compounds doesn't have the desired results - it's more that the four pots are too strong for the stock rears and the FRC mod is really needed, in addition to a bias adjuster. JDS is saying to just change compounds which is opposite what you're stating!

What's your final combination!??
 

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@arsenal For street use, I think that you could correct the bias enough to help the bias issue by playing with the pads.. It is not until you start pushing the performance levels that you are going to start seeing the deficiencies in braking. As I stated, I did not notice the problem that much when I was auto-xing. OEM cars are configured from the manufacturer to be heavily bias towards the front. It is considered safer to have a car demonstrate understeer rather than oversteer.

The S260 has Pilbeam brake bias setup with Wilwood 4 pot calipers with the same piston sizes all around. The ABS system was removed because it is worthless in on the street because of Ice Mode. The Cup-R will soon have the Pilbeam brake bias setup which also has the Bosch Motorsports ABS system.

Later,
Eldon
 

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Discussion Starter #18
Thanks for all of the suggestions so far. For more context, the issue is most noticable when heavy on the brakes and starting to turn into corners on local (San Diego) mountain roads where bumps can unsettle the car. The suspension and brakes are stock S240 (~320mm disk up front with 4 pots and ~285mm rear and sliding single pot caliper). Also I’m going to admit that some of this is me not the car: A couple of prior accidents have left me with a lot less strength and fine motor control in my right leg than I would like - my left leg is fine and I would routinely left foot brake my non-servo assisted Caterham but I find the Exige pedal geometry is less ideal for LFB so my right leg gets pressed into action on the Exige. The relative lack of right leg strength is in part why I would quite like to keep the servo if possible. I had a 05 Elise previously and that had much better front / rear brake balance but the ability of the front 4 pot calipers to slow the Exige in a straight line is impressive.
Shinoo is pretty close to me and had previously given excellent advice on steering set up for the Elise so I’ll visit and discuss some more.
Shinoo - expect a visit but I’ll give you a call first.
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@mlc66 OEM rotors for that car are 308, not 320. If you have 320mm rotors then somebody put them on there. If you drop back down to OEM, it will better but the corner entry push will not completely go away.

Later,
Eldon
 

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I stand by my view that it makes most sense to try the cheaper options first - brake pads can make a difference in feel and rate of weight transfer.

If you have a unique situation and want to try bigger options, for a street car I'd be more inclined to replace the 4pot up front with the 2pot on the earlier cars. It will guarantee an OEM braking experience. The one issue you'd encounter is the brake lines up front terminating in a banjo bolt, but I would think Shinoo could provide a recommendation on a place that could "convert" the OEM 2 pots to use the brake lines you have.
 
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