Another big-brake kit for 15"wheels.

Jim K
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Another big-brake kit for 15"wheels.

Post by Jim K » Wed Sep 14, 2011 9:28 am

Well, I promise this is the last big brake kit I ever build! In fact, my 75's all have big brakes, so I have no car to stuff these on :roll:
I used all new parts for this: Brembo 4pot (monoblock) calipers and 310x28mm discs from the 166 24v pimpmobile. I had to devise and have special brackets made to mount the calipers and special stud-holder rings to fit behind the discs. Since I wanted the brakes to fit inside my Compomotive MO 15" wheels, I also had to carefully sand off ~1.5mm from the caliper curved outside surface. Stock thickness of the bridge is ~23mm and I left it with ~21.5mm, so that there is also ~1mm of radial clearance left between caliper/wheel. These parts are matter-of-fact overdesigned so I don't feel what I did was precarious (but this -really- remains to be seen, doesn't it? :wall: )
Why use these particular calipers? Their pads (FCP1334) have ~50% more area than the classic Brembo reds!
One thing that pissed me off, was that the bolt pattern of the 166 is NOT 5x98mm so I had to elongate the holes as you can see. Why NOT 5x98??? ...Idiots!
Jim K.
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75evo
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Re: Another big-brake kit for 15"wheels.

Post by 75evo » Wed Sep 14, 2011 10:43 am

Brera bolt pattern 5x110
166 bolt pattern 5x108
GTA bolt pattern 5x98
Mito bolt pattern 4x98

LOL!!!!!!!!!!!!!!
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Re: Another big-brake kit for 15"wheels.

Post by Jim K » Wed Sep 14, 2011 11:03 am

What can I say?...Must be some kind of in-house stupidity contest... :shock: :evil:
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Re: Another big-brake kit for 15"wheels.

Post by kevin » Sat Sep 17, 2011 12:57 pm

Just as stupid as the different spigot sizes. Silver looks good. There were a whole bunch of the silver brembos floating around from all the new giuliettas that were sent to uk as they were supposed to be red , so alfa duly replaced them . I know few guys sitting with them but not parting with them.
Slighty off topic , what would be your minimum amount of thread left to tighten up wheel nuts - I think I'm sitting on 16mm on my rear brakes with the outboard bells on my race car .
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Re: Another big-brake kit for 15"wheels.

Post by Jim K » Sat Sep 17, 2011 9:37 pm

I don't know where this originated but the general consensus is that you should have a thread depth at least equal to bolt dimeter. In this case, 12mm divided by 1.5mm pitch = 8 turns.
...And I still haven't got an ad-dress! :lol:
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Re: Another big-brake kit for 15"wheels.

Post by rowan jackson » Tue Jan 27, 2015 12:35 am

Jim

Do you happen to know whether a standard GTV6 or perhaps Alfa 90 wheel would fit over this brake set up? Having finished the 3.2 transplant I think I need some brakes. I was thinking too of a 305 GTA disc? I am keen not to increase the weight of wheels significantly if I can avoid it.

Thanks
Rowan
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Re: Another big-brake kit for 15"wheels.

Post by Jim K » Tue Jan 27, 2015 3:58 am

Hi Rowan,
If you are referring to my brakes above, nothing short of 16" 'normal' wheels will fit EXCEPT Compomotive 15" wheels, as they are the roomiest wheels I know off -and still, I had to reduce disc OD to 308mm from 310 for these particular calipers. The 16" Comomotives will fit 330mm discs. Unfortunately, for 100% confidence, you must try wheels on for size. It may be cumbersome but you can visit different wheel shops with a completely assembled upright/hub/brake in the trunk... Besides radial clearance, you must also check the axial clearance from the caliper. These big Brembos can sometimes be found at very low prices: http://www.subito.it/accessori-auto/pin ... 495918.htm
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Re: Another big-brake kit for 15"wheels.

Post by maxiboy » Tue Jan 27, 2015 1:06 pm

The number of turns to securely fasten a wheel will depend on the pitch of the thread of the stud. But a commonly regarded guideline is 1.5 times the diameter of the stud. So a 12mm stud should have 18mm of thread engaged into the retaining nut to be secure.

Hope that helps
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Re: Another big-brake kit for 15"wheels.

Post by rowan jackson » Wed Jan 28, 2015 2:39 pm

Thanks Jim, the problem here is the availability of decent wheels to check fitment against. I might need to order some wheels and make something fit instead, so the information that Compomotives are spacious is helpful. Do you have a drawing for the brackets?
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Re: Another big-brake kit for 15"wheels.

Post by Jim K » Wed Jan 28, 2015 8:26 pm

One problem with Compomotive is they recently restructured the company (closed down and re-opened after a few months) and in the process, they stopped/postponed some wheel models so you will have to contact them for designs/availability. They told me the 8x15" MO wheels I want will be available within the year... :(
I don't have a drawing for the brackets as I made the first set myself on a mill. All subsequent sets were made by a local machine shop copying my part. If you are planning to use the same wheels (7x15 or 8x15 Compomotive 5-spoke MO, 25-30mm offset) I can ask for cost and have my original bracket copied again. I have another set of such new calipers and uprights for my other 75 (24v), so I can have the brackets tailored for perfect fit. It all rides on wheel availability though. If you go to 16" wheels, there's no problem with 310mm discs. For 15's though, Compomotive is key factor. Note that these big Brembos will not fit properly on discs <308mm as the inside edge of the pads goes off the swept area. That is if you use the Alfa 166 310mm discs. For other discs, you'll have to figure things out carefully. The smaller 'red' 4-pot Brembos have narrower pads allowing use of cut-down M3 directional discs (315 reduced to 310mm). Brackets are a little different in this case.
Another detail to observe is the countersinking of the radial caliper mounting holes. See how the 12mm Allen bolts are almost flush with the caliper surface? They have to, in order to allow a smaller wheel -otherwise the heads would stand out 12mm, reducing disc size to ~290mm or necessitating 16"wheels!
I know brakes are a relatively simple matter but putting together a proper set needs a bit more thought than most people give it credit for!

Jim K.
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Re: Another big-brake kit for 15"wheels.

Post by rowan jackson » Fri Jan 30, 2015 12:18 am

Happy to give it plenty of thought but much prefer to steal someone else's solution!
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Re: Another big-brake kit for 15"wheels.

Post by MD » Fri Jan 30, 2015 2:25 am

One thing that pissed me off, was that the bolt pattern of the 166 is NOT 5x98mm so I had to elongate the holes as you can see. Why NOT 5x98??? ...Idiots!
Why not get blank rotors and drill the bolt pattern of your choice?
Transaxle Alfas Haul More Arse
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Re: Another big-brake kit for 15"wheels.

Post by Jim K » Fri Jan 30, 2015 7:31 am

Good thinking Rowan, but you must find out where they park their cars at night, :twisted: :lol:
MD, original 166 discs wholesale cost here ~96€/pair. I don't think I could get blanks for less.

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Re: Another big-brake kit for 15"wheels.

Post by Mats » Fri Jan 30, 2015 8:49 am

General OEM design principle on nuts/bolts design, two full threads visible outside of the nut. So full nut engagement plus two full turns.
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Re: Another big-brake kit for 15"wheels.

Post by Jim K » Fri Jan 30, 2015 12:14 pm

Ok, for 'normal' nuts but how about wheel nuts which can be ~25mm long and tapered nose? I can see a 12-14mm engagement but in this case ~25-30mm? :shock:

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