FYI: 10" brakes work on the front

Dsteinhorst

Well-Known Member
This is going to sound backwards to some people, but in the quest of clearing the brakes with 15" RPF1s, Adam turned me onto the fact that the 10" base model brakes fit on the front uprights with slight modification to the front hubs.

I was using cheap 4x100 x 1" spacers and was looking to get rid of them for weight savings, and because lug-centric spacers are ratchet. Also, I had about 0.020" clearance even with them:
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I emailed Adam asking if they'd make custom uprights to move the caliper in, but he ended up pointing out what I should have noticed. The only difference between the 10" (4 lug) and 11" (5 lug) brakes is the bracket and the rotor.

I test fit yesterday, and the OD of the hub is too big. I turned it down to about 5.200" today and it fits great:
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The benefits for me are 4-fold
1. Clear my wheels
2. Better balance front/rear braking that several people have mentioned.
3. Reduce overall braking to give better pedal feel with vacuum assist. (Effects TBD)
4. Remove 2# of spacer and about 2# of rotor weight from rotating assembly.

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Needed supplies to convert from 11" brakes are two caliper brackets from a 4 lug car and two 4×100 rotors. Turn down front hubs to fit inside 4 lug rotors (you measure.) If you pound out one wheel stud, a 3 jaw chuck in a lathe will grab it.

Hope this helps someone else. I wish I would have known this a year ago!
 

k.rollin

Goblin Guru
What brakes are you running in the rear? I had considered this for the fronts with the parking brake kit years ago for lower cost, lower weight, and wheel clearance for my 15" wheels. This was the advice I received from Adam:
 

Dsteinhorst

Well-Known Member
I'm still not yet certain if I'll have 10" rears, which was my original thought, or Solstice rears, which may or may not even fit with my wheels. I'll probably end up trying both.

It is interesting some people with dual 11" brakes are installing valves to reduce front braking, when having dual 10" brakes reduces braking force equally on the front and rear.
 

TravMac

Well-Known Member
Reading this over and comparing to similar build setups, I'm left with a few questions. It seems like some builders already accomplished this with just just some caliper clearancing. Was the clearance issue you saw with the wheel face or just the wheel hoop? What is your wheel spec for width and offset? I'm looking to run the same sort of set up if I can. Im also hoping to avoid buying wheels that plain dont fit if i can help it.
 

Dsteinhorst

Well-Known Member
I did have the option to grind calipers down as I know at least one other person has done with these wheels, but it seemed like quite a bit as I was measuring. I chose the cheap spacer option to get by until I could machine the calipers correctly or find a better solution.

The wheel "hoop" is the only clearance issue; it is exceptionally deep on the RPF1 compared to many wheels. Mine are the 15X7 with 35mm offset. The Sparco FF-1 fits just fine in 15X8, lots of 15" wheels fit.
 

TravMac

Well-Known Member
I think i understand that, thanks for the input. I really have wanted those wheels ever since I saw them on a buddy's miata. Plus they are so light it's hard to argue for the price.
 

Dsteinhorst

Well-Known Member
Update after an autocross event last Sunday.

There is some truth to the back brakes locking first. You have to really get on them, though, and even then, it's manageable. I don't think I'll be changing anything in the short term. I'm happy with the outcome.

I also got an ebrake setup from another local Goblin owner, so I'll probably install that later in summer. I have to clearance the calipers a bit to give some flexing room, but it seems to fit under the RPF-1 wheels.

Unrelated to brakes, I upgraded to 225/45/15 Falken Azenis RT660 tires and that made a HUGE difference! Went from middle of the pack of 75 cars last season to 4th out of 84 Sunday!
 

Dsteinhorst

Well-Known Member
Well, my rotors had an anti-corrosion coating. Maybe once that got worn through, things evened out. I'll have to take a swing around the block.
 

Dsteinhorst

Well-Known Member
After about 3,000 miles, everything works great, and I don't have any issues with one locking before the other. Several autocrosses, quite a bit of low speed city miles, and a solid amount of highway and backcountry driving. I'd build it this way next time in a heartbeat.
 
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