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Post by jwagner on Aug 22, 2016 18:34:06 GMT
My brake pedal is way too light. Everyone that has driven the car has complained about it, and it's near impossible to modulate the brakes near the threshold and heel toe takes more coordination than I have in my feet. I want a harder pedal.
Two ideas come to mind - 1) remove the vacuum booster, or 2) put in lower friction pads. Anyone else have this problem? Has anyone else deleted the booster?
thanks
Jim
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Post by snowbird1 on Aug 23, 2016 6:38:32 GMT
Just disconnect and cap the vacuum line - see if you like the feel.
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Post by papabear on Aug 23, 2016 13:16:06 GMT
With the 4:1 stock pedal ratio you are going to lose alot of line pressure for the brakes. The stock Miata power brakes rely heavily on the power assist. You can try it with the vacuum pulled off but you would really need to look at changing your pedal ratio. I know you can re-drill the stock pedal but not sure how much you can change it.
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Post by jwagner on Aug 23, 2016 15:27:49 GMT
Just disconnect and cap the vacuum line - see if you like the feel. I thought the booster added a lot of resistance, but maybe that's just the way it works because of the master cylinder/pedal design as papabear noted. After a couple of hours of digging for brake technical info, it looks like the Carbotech XP-8 coefficient of friction is about .6, which is pretty high. Found some pads are closer to .4 (Porterfield R4S) which might help. Was talking to a local guy with a Stalker which uses Miata hubs/brakes/etc. and he replaced the master cylinder and pedal set with Wilwood and seemed pretty happy with it. Replacing the whole shooting match might be a good solution since I'm going to have to mess with bending the pedals to the left since they're up against the tunnel which makes it near impossible to heel/toe. |
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Post by kiwicanfly on Aug 23, 2016 19:51:15 GMT
Not using a booster or anything on my Rocket, just the Wilwood box.
However my thoughts would say to increase the pedal ratio rather than change the pads, that way when you NEED the better pad you have them.
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Post by nickmpower on Aug 24, 2016 14:32:33 GMT
I've done some research on this. I think there was a civic master cylinder or something that was a bigger bore so increased the pressure if needed after deleting the booster. Search "miata manual brakes" in google. I have some track time in an Ultima GTR and it has the best brake feel you can imagine. The pedal only moves like 1/4" total, you don't even notice that it moves. Braking is just based on pedal pressure. I think the AP racing calipers have little springs that keep them against the discs or something though. Some how the pedal has near zero movement, yet doesn't require an insane amount of pressure.
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Post by jwagner on Aug 28, 2016 22:44:48 GMT
After a bunch of looking on the intertubes and talking to Carbotech for a while, I'm going to try Porterfield R4S, which are street/performance pads with a lower coefficient of friction. Our normally aspirated car hasn't been hard on brakes, and even after two consecutive track sessions (dual driver) they really don't get nearly as hot as Miata brakes. This is a stopgap solution for this year, and by next spring I hope to have a new braking system, probably Wilwood calipers, master cylinder, and pedals, and maybe a K20 which will make better brakes and higher heat dissipation more important.
Carbotech brakes have been really good for us, and their customer service has been great, so I'll probably go back to their XP series.
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Post by boileralum on Aug 29, 2016 18:34:42 GMT
How much meat is left on the Carbotechs?
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Post by nickmpower on Aug 30, 2016 21:54:15 GMT
This is something else I found. If you have a 7/8 bore MC this will increase the pressure needed by 33 percent. Nice thing about this is The pedal travel will be decreased by the same percentage effort increased, where as with lower friction pads you are actually increasing the pedal travel. I think this is probably what you are looking for. 949racing.com/miata-wilwood-master-cylinder.aspxMaybe there's an even bigger/cheaper option, haven't looked much yet. |
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Post by jwagner on Sept 12, 2016 20:20:08 GMT
How much meat is left on the Carbotechs? Rich, finally got back on the brakes, been working on a megasquirt conversion for a while. I didn't mic them, but I'd guess the front pads have at least 60% left. This is after about 12 hours of track time and a few autocrosses. I'm thinking that they'll go on my '94 Miata this fall. |
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Post by jwagner on Oct 10, 2016 17:00:03 GMT
Update - We went with the Porterfield R4S pads and are pretty happy with them. The brake pedal pressure increase helped reduce the too-easy lockup and problems with heel/toe, and we had no problems with heat or fade running back to back track sessions at Laguna Seca. I think the long term solution will be Wilwood cylinders/pads/calipers, but for now with the NA 1.8, it works well.
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Post by dietcoke on Oct 10, 2016 18:21:07 GMT
I'm running cobalt XR2 pads in the front and XR5 in the rear, love them.
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Post by jwagner on Oct 10, 2016 23:58:37 GMT
I'm running cobalt XR2 pads in the front and XR5 in the rear, love them. Are you running stock calipers/rotors/master cylinder? Do you track the car as well as autocross? I'm wondering how the cobalts put put with heat, especially in your high powered Exocet. |
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Post by dietcoke on Oct 11, 2016 11:27:47 GMT
they're race pads, so you aren't going to kill them with heat.
I have wilwood fronts and stock rears.
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