I'm not running a proportioning valve had an adjustable one from FM but it was leaking so I joined the lines with a union adapter instead of going through a proportioning valve. In an autocross setting with HPS pads and 1.8 brakes the fronts still lock up first. Now I plan on doing some track days this year and I was thinking of going with the Stage 1 kit from 949 racing with XP10 in the front and XP8 in the rear. Originally I was going to go with XP8 all around but that might make it too rear biased possibly.

Right now this is my setup, no turbo (yet) going to keep it NA for now
450/335 coilovers
Front RB hollow bar, 949 adjustable endlinks
rear bar disconnected
15x7.5 +30 wheels with 205/50/15 Star specs (possibly switching to 15x9 with RS3s later on this year)

Am I making the right choice? I just want to double check before I order.

Thanks!

 

Buy a new proportioning valve.

 

Get a propvalve. I have XP10/8 with a valve and could still use a little more rear bias.

 

TSE has steel fittings now, get those, thank me later.

 

Are you running the adjustable valve or the stock one?

I'm just pondering if I even need the adjustable valve with street tires and XP10s on the front. On stickier tires more weight is transferred to the front and off the rears I see that in that case it would make more sense. When I had the adjustable valve in for about a year I was running the valve fully open and the fronts still locked up first on Star specs with equal brake compounds all around, this was in autocross situations so probably never went past 60mph.

This is what I'm running now which is equal to the wilwood valve being full open and the fronts still lock first.


That's good to know, didn't know these even existed. Do you put anything else on those? like teflon tape to seal it? When I used the FM ones I didn't use anything and they weren't sealing completely. I mean the amount of brake fluid that was coming out was very tiny, not enough to drip but it did show up on the treads of the adapters. I decided to tighten them a little more after driving like that for a year, big mistake. Ruined the adapters and turned the almost non existent leak to a large leak.

 

i would put the prop valve back on. If you got lucky and happen to have ideal bias due to pad selection, then great. However, it pretty much locks you into only those pads.

I swapped pads last night, and I need to adjust my bias.

 

I had the same problem with the FM fittings. Cracked one of them while trying to tighten it enough to not leak, got a replacement. That leaked a bit with Teflon tape, took it off, cleaned out the threads and used Teflon paste instead and it doesn't leak. Still, the fact that those adapters have such issues with sealing is in the back of my mind, and I may get the TSE ones even though the FM ones aren't leaking at the moment.

If I were you I'd buy the TSE steel fittings and reinstall the adjustable prop valve. Your tires will get a lot more heat into them at a track day than they would at an autox. That means extra grip and better braking. If you run a track day with no prop valve and have issues with the rears locking up, what are you going to do about it? I can't say with any certainty if that will be an issue for you, but at least with the valve in place you can dial it back if needed.

 

Ok so the prop valve is going back on. Now what pads should I use xp8s all around, or xp10 front and xp8 rear?

 

Why does everyone put more agressive compound in the front? the rears are where we really need the help.


EDIT: and of course TSE has steel fittings after I sold off my prop valve...My brass fitting broke once while I was driving the car.

 

Ok so maybe the XP8 all around should be a better choice for me then? The xp10/xp8 combo probably comes from the spec miatas but they are running R-compounds. Stickier tires will transfer more weight to the front under braking, reducing the weight in the rear, making the rear more prone to locking up. At least that's my guess. Even the 949 racing miata rental which runs nt01s and RS3s uses xp10/xp8 http://02e4344.netsolstores.com/99-miata-rental.aspx The more I read the more I confused I get.

 

Adjustable Wilwood valve. I have the lines coming off the master joined like that in the picture, propvalve in tranny tunnel. Fittings I had leaked too, added a little teflon tape, tightened carefully and they've been fine ever since.

 

perhaps don't read. let the car tell you. dont change anything and do a few days and see. if you know you don't like the pads you have you can get used pads cheep from somebody who upgraded from 1.8's to something else (maybe do just the fronts and try that for a day or two).

i'll also echo your thoughts and what others have said. locking the fronts in autox is big problem for me. not such a big problem (at least for me) on track. on track it was much more interesting to play with the balance of the car on corner entry than to try to get every last .01g in straight line braking.

 

Thanks for all the replies, ended up going with the 949 stage 1 kit with xp8s all around and the proportioning valve with the TSE fittings. Now I just need to replace the radiator and all the cooling hoses and I should be ready for track