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Discussion Starter · #1 · (Edited)
Just wanted to see if I could get some feedback on them as I didn't really find much info in my searches. I'm guessing there aren't a whole lot of people with them at the moment.

I'm currently running Hoosier A6's in AutoX and I think I could use some more breaking power to run in a little deeper and pick up some time. Our courses here are quite fast in areas (50-120kph) and more like mini circuits. We also more or less don't have any modification rules.. I'm currently running the eliseparts.com rotors and Pagid Blue pads. Would moving up to Pagid Blacks or Hawk pads make that much difference? or would I be better off just upgrading? I figure if I upgrade the fronts then I'll have the current set of front rotors as spares for the rear. This will allow me to run an aggressive rear pad that will eat the rotor and I'll have replacements on hand for when that time comes.

The reason for all of this is I have to remove the front end in the near future to replace the blower fan resistor pack so If I'm going to upgrade now is the time.

BTW: Does anyone have one of those Sector111 blue radiators on hand? I think it would look pretty good on the Storm Trooper Exige. ;)
 

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Autocross is all about getting around the cones, so maybe you want a larger rear brake. There is a rear brake re-size that is a simple swap.

Yup, I'm a Viper guy, but the cars share the same rear caliper. And yup, in AX, the first model year Vipers suck until they get better rear brakes.

40mmBrakes Home

I wrote the SELOC TechWiki articles about the brakes history and also how to rebuild them, so if you have any questions, let me know.
 

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Discussion Starter · #3 ·
Autocross is all about getting around the cones, so maybe you want a larger rear brake. There is a rear brake re-size that is a simple swap.

Yup, I'm a Viper guy, but the cars share the same rear caliper. And yup, in AX, the first model year Vipers suck until they get better rear brakes.

40mmBrakes Home

I wrote the SELOC TechWiki articles about the brakes history and also how to rebuild them, so if you have any questions, let me know.
I would be quite interested in a better rear brake actually... I have a lot more grip on the rear with the 245's and especially when I run the A6's. From what I'm getting off your site they are $700 with a core and $999 with out correct? Can you ship them out and wait for a core return? Or do you need the actual breaks before you would send the replacements? My car is a daily driver and I need to keep it on the road is why I ask.

The only thing I'm sketchy about is if I go with a big brake kit on the front + the larger diameter pistons on the rears is that the master cylinder may not be able to supply volume of fluid need to make them work properly due to the incresed volume of the calipers. I would also dislike having a lot of pedal travel over stock if it can be avoided.
 

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Dragon, I assumed the pads have to "travel" 1mm to re-engage the rotor. Therefore your pedal travel "increase" would be the volume difference between 1mm travel of a 36mm piston vs. 1mm travel of a 40mm piston.

36mm: area=Pi*r^2=3.1415*18^2=1018mm volume=1018*1mm travel=1018mm^3
40mm: area=Pi*r^2=3.1415*20^2=1257mm volume=1257*1mm travel=1257mm^3

volume increase for two calipers = 2*(1257-1018)= 477mm^3

In a Viper, the master cylinder diameter is 27mm.

27mm: area=Pi*r^2=3.1415*13.5^2= 573mm^2
travel distance to make up a volume of 477mm^3 = 477/573 = 0.83mm

In a Viper, the ratio of the master cylinder movement to pedal movement is about 3.5:1

pedal movement= 3.5mm*0.83 = 2.9mm, or about 0.11 inches

Again, this is based on a 1mm travel distance between no braking and braking. Whatever it is, in a Viper the pedal travel difference is not noticeable. If your master cylinder diameter is close to 27mm, I expect the same. Many Viper owners take this single piston rear caliper off and replace it with a four piston caliper and stay with the same master cylinder. I think it is because we look at the diameter change but overestimate the piston travel.

If the rear brakes help you, then going to larger front brakes may undo that benefit. The car handling is based on the front to rear balance, rather than the total clamping force. Unless you are overheating the front pads, do you need bigger ones?

I will put together a few shipping/cost choices for you and send a PM.
 

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Dragon I will strongly suggest you try the Pagid RS14 next time before you spend a lot of money on increasing rotor size.

I was running the blues with oversized RA1 tires at the track, and found I could barely reach abs on smooth straight pavement. I'm sure with your A6 tires it would have been impossible.

But when I switched to the blacks I got more power with less pedal pressure. Exactly what I was looking for.

Pagid also makes a couple of compounds with higher friction than the RS14 so if you want to bump up your rear brakes you can do that too. I spoke with Craig at Rennstore, who has charts of the relative friction values of the different Pagids at various temperatures. I asked him about the "Gray" compound because I had seen on the chart that it's friction values - even cold - were higher than all the rest. He recommended against it because he said it's so grabby on these light cars. But if you really needed more friction on the rear that bad, you could try it.

xtn
 

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Discussion Starter · #7 ·
Excellent info... Yea I was full on the brakes with pagid blues and there was no hint of ABS. I already have a set of SS lines I've been sitting on now for a good 10 months so. I think I'll install them and pick up some Pagid blacks and see if that gives me what I'm looking for.

How noisy are the Blacks on the car? Driving around a Lotus with squeaky brakes gets a bit of attention around here.. lol

Thanks...

Dragon I will strongly suggest you try the Pagid RS14 next time before you spend a lot of money on increasing rotor size.

I was running the blues with oversized RA1 tires at the track, and found I could barely reach abs on smooth straight pavement. I'm sure with your A6 tires it would have been impossible.

But when I switched to the blacks I got more power with less pedal pressure. Exactly what I was looking for.

Pagid also makes a couple of compounds with higher friction than the RS14 so if you want to bump up your rear brakes you can do that too. I spoke with Craig at Rennstore, who has charts of the relative friction values of the different Pagids at various temperatures. I asked him about the "Gray" compound because I had seen on the chart that it's friction values - even cold - were higher than all the rest. He recommended against it because he said it's so grabby on these light cars. But if you really needed more friction on the rear that bad, you could try it.

xtn
 

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How noisy are the Blacks on the car? Driving around a Lotus with squeaky brakes gets a bit of attention around here.. lol
In my experience they are not squeaky, but in street use they do build up that develops a clicking noise from the rotors. A few aggressive stops cleans them out. Blackwatch Racing is a Lotus specific vendor and they have competitive prices:

Lotus Brakes - Blackwatch Racing
 

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The ST-43s have rediculous bite as well, FWIW... I'd be really surprised if you need more stopping power than what the really aggressive pads will provide:up:

Best,

Phil
 

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You know how the blues will occasionally squeal on the street under conditions of of a slow, gentle stop? Well the blacks are very very slightly worse. The squeal happens under the same conditions, but it's just about 1% louder than it was with the blues. And as with the blues, if you just push a tiny bit harder, the squeal goes away.

Anyway it's certainly worth a try before you go spend big money on big brakes.

I stole this chart from Rennstore's web site. Hope Craig doesn't mind.



xtn
 

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