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Thread: Hydroboost and Wilwoods, master cylinder bore size?

  1. #1

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    Hydroboost and Wilwoods, master cylinder bore size?

    I have the FFR supplied Wilwoods, Fortes hydroboost with modified pedal box and Forte supplied master sylinder. The brakes work great, locks the wheels easily, modulation is good. I have pressure bled the brake system. However, the brake pedal will go all the way to the bottom stop. I believe I have bled all the air out, so before I try again, I'm wondering if the master cylinder i have moves to little fluid for all the pistons in the Wilwood calipers, and that I need a master cylinder with a bigger bore. Couldn't find anything about recommended MC bore size for the brakes on Wilwoods website, also, don't know the bore of the Forte supplied MC, bought in 2019. Any thoughts/ knowledge about this?

  2. #2
    Senior Member dbo_texas's Avatar
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    Not sure if this helps, but Forte told me he uses a 1999-2006 Chevy Silverado pickup truck hydroboost for the FFR kits. I can't tell what size MC is mounted to the end of the hydroboost - it's a FoMoCo part and I see 2140 in the casting which sure looks like THIS part. I tried Googling the specs for that to see if it lists the cylinder size but couldn't find anything. I'd call Forte and confirm with him if that is the right part - he is super helpful when you call.

    Is this what your MC looks like?
    Darryl [dbo_texas]
    MKIV #9644 (build thread) (Index)
    MK4 Complete Kit | Gen2 crate Coyote | Tremec T56, 3.55 IRS | power steering | hydroboost | dual roll bars | FFR carbon fiber dash | 18" Halibrands + Wilwoods | RT drop trunk kit & turn signal | front battery mount | saddle leather Intatrim Stoneleigh seats + interior accents

  3. #3

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    Thank you Darryl. I just wanted to check if anyone with my setup has experienced the same. If not, I'll have to assume it's my bleeding process that is faulty. Yes I have the same master cylinder as you, Forte hydroboost and the 12.88" Wilwoods front and rear from FFR, so i believe we have the same setup...
    I'll may have to call Forte anyway, as i came across pictures of the adjustable pushrod that came with the hydroboost, and realize now that mine is missing the locknut.

  4. #4
    Senior Member dbo_texas's Avatar
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    Mine didn't have a lock nut on it either, and when I talked to him he said you should install one. I used a regular nut (after tracking down the correct thread size) and shaved it down so it would fit. Used an angle grinder with sanding disc.
    Darryl [dbo_texas]
    MKIV #9644 (build thread) (Index)
    MK4 Complete Kit | Gen2 crate Coyote | Tremec T56, 3.55 IRS | power steering | hydroboost | dual roll bars | FFR carbon fiber dash | 18" Halibrands + Wilwoods | RT drop trunk kit & turn signal | front battery mount | saddle leather Intatrim Stoneleigh seats + interior accents

  5. #5
    Senior Member dbo_texas's Avatar
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    Curious to know how you feel about the overall setup of hydroboost + Wilwood. My kit came with both from the previous builder, and I've had some strong opinions (a few PMs sent) that the combo is overkill (one or the other is good, but not both). Some say it will act more like an on/off switch and lock up too easily. Others say it might be fine as-is. My plan was to try it out and see how it responds before deciding if I want to eliminate the hydroboost and go back to strictly Wilwood manual setup. Obviously that would require me to make new brake hard lines since the plumbing connection location is different (inside pedal box vs. the front side of the hydroboost). Sounds like yours feels OK (i.e. not too twitchy), just dealing with the brake pedal being able to push down all the way? Would like your opinion as not many folks have this combo like us. Feel free to PM me too if you don't want to reply in this post as it seems to be a hot button topic for some folks. Just looking for some actual feedback from someone who has this same setup.
    Darryl [dbo_texas]
    MKIV #9644 (build thread) (Index)
    MK4 Complete Kit | Gen2 crate Coyote | Tremec T56, 3.55 IRS | power steering | hydroboost | dual roll bars | FFR carbon fiber dash | 18" Halibrands + Wilwoods | RT drop trunk kit & turn signal | front battery mount | saddle leather Intatrim Stoneleigh seats + interior accents

  6. #6

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    Personally, I find it very easy to modulate the brakes, they felt very comfortable right from the start. Yes I can easily lock the brakes if I want to, but it is certainly not like an on off switch. Is it overkill? Quite possible, I can't tell for sure since I haven't tried the alternative. It will be interesting to see if they feel different when I get the pedal bottoming problem solved. I've got no problem admitting it if they get worse.

    With regards to the pushrod, I saw you put a locknut on the one between the hydroboost and the pedal, I did the same. It's the one between the hydroboost and the MC that didn't come with a locknut.

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