Technical Possible shortcut for an irritating job with the rear brakes

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Technical Possible shortcut for an irritating job with the rear brakes

mj2k

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I've been changing the rear discs today on the Abarth 595, or to be exact the rear disc, still need to do the other one :rolleyes:

All I can say is what a faff, I think Fiat had a bit of an 'Alfa moment' in their design there - making the rear wheel hub in such a way you have to remove the whole stub axle to take the brake disc off, and in the process most likely snap your ABS sensor off whilst trying to remove it.

After spending an hour trying to find out what torque to retighten the stub axle bolts on replacement should be (120nm I think) and a further hour carefully unhooking the handbrake cable, removing the caliper and attempting to remove the ABS sensor before my bottle gave out, I decided to try something a bit different.

I loosened off all the stub axle bolts to within a few threads of coming off, then with a little careful prying freed the stub axle enough so I could twist it a bit and fit in a standard hex key in the top bolt, meaning I didn't have to completely remove the halfshaft to get the caliper carrier off. So one small win.

And then whilst finally removing the carrier I cursed the design of the hex headed bolts which held it on, and wondered why the heck Fiat used them rather than a standard bolt, like Subaru. And then I had a brainwave - I had 4x spare rear caliper bolts left over from my last Subaru build so dug them up for a quick comparison - same thread pitch and length:

IreIjX.jpg


So then gave it a quick try in the caliper carrier - fits like it's meant to be there :)

2YMLm1.jpg


Admittedly it doesn't look as 'chunky' as the Fiat original, but given the Subaru rear caliper design is identical (except for the handbrake) and the Subaru is a much heavier, usually more powerful car with a more substantial rear brake assembly, the smaller Subaru bolts should be well up to the job of holding the Abarth rear caliper in place.

So fitted the caliper holder up with the Subaru bolts - success! (note the ring spanner fitting with plenty of clearance near the top of the pic)

MUDJTJ.jpg


Not much help this time round, but next time round it'll only take a few tweaks with a normal spanner to get the caliper carrier off and replace the disk, rather than ages struggling and worrying about potential damage. Should be simple enough to pick up rear caliper carrier bolts for a 2004-2007 Subaru Legacy from somewhere like importcarparts, but I suspect there are many other similar caliper carriers around on other cars which use the same type of bolt.

I'll be monitoring it for a while just to make sure it's stable, but if nothing goes awry this could be a very simple fix for one of the Abarth's most irritatingly pointless jobs (y)

NOTE: If you do plan to try this, use proper hardened steel bolts from another caliper carrier of the same length, pitch, etc. Stick any random old bolt in there and you might get to witness the lovely sight of your rear brake calipers flying past, shortly followed by you making an interesting journey into a ditch if the softer bolts strip their threads or shear off under heavy braking.

Also please do not attempt this if you don't understand anything in my rambling above or don't have the correct tools (including a torque wrench, suitable crows foot socket for your new bolts and access to the correct torque specs for everything) - far better to waste a couple of hundred quid getting a specialist to do this poxy job than risk a trip to A&E or worse.
 
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A3jeroen

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But why and I mean WHY would you take of the axle stub? I always take only the carrier off.
The thing I always struggle with are the small bolts that keep the disc in place. They tend to get either rounded or sheared off.

gr J
 
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mj2k

mj2k

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But why and I mean WHY would you take of the axle stub? I always take only the carrier off.
The thing I always struggle with are the small bolts that keep the disc in place. They tend to get either rounded or sheared off.

gr J
On mine at least you can't get an Allen key or hex socket into the top one of those stoopid great bolts because there's no clearance (I'll take a pic of the other side to illustrate when I do it).

I have to go through this nightmare procedure:

Simple solution for those little bolts is the one I adopted when swapping to the MAK XLRs - simply leave them out :D

They don't really do anything except make wheel fitting 'easier' (you need to make sure the holes in the disc stay lined up with the threads in the axle) which isn't a problem on the MAKs because they're so light, but could be easily worked around on a normal alloy simply using a screwdriver, stud or dowel (or just wait for them to rust in place), or even cut the little bolts off flush with the disc and use them just as location studs (y)
 
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mj2k

mj2k

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Your Subaru boots are also used from factory in some cars...


I'm wondering if maybe mine's another piece of Brembo idiocy from the 'Brembo upgrade kit' if nobody else has the same bolts...

It'd also explain why my car, which otherwise seems immaculately maintained, had bigger shoulders on the edges of the rear discs than Joan Collins in Dynasty, maybe a normal garage wouldn't touch that 'mare of a job.

Dynasty-Dynasty-TV-Series-014.jpg
 
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vexorg

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Is that top bolt stripped? or have the thread from the hole in it?

The smaller VW and audis are good, a nice design means you can replace all the discs without removing the carriers.
 

A3jeroen

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I'm shocked. I always (well on other fiats) did them like in the video Olliver posted.
And yes... All 8 bolts to hold the discs in place are already missing on the Abarth, but I found some sheared of ones from the 100Hp.:unsure:
So I measured them and they are normal M8. Not sure if i will replace them in the future.

gr J
 
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mj2k

mj2k

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I'm shocked. I always (well on other fiats) did them like in the video Olliver posted.
And yes... All 8 bolts to hold the discs in place are already missing on the Abarth, but I found some sheared of ones from the 100Hp.:unsure:
So I measured them and they are normal M8. Not sure if i will replace them in the future.

gr J
Gave me a bit of a shock too, totally bonkers! Wonder if it is unique to the Abarth brake upgrade kits or if the 595 Turismo, SS, Comp and 695s all have the same mad design?

Not really worth replacing the little bolts IMO, and if you go for aftermarket (or presumably earlier Fiat/Alfa design) wheels they get in the way of where the wheel sits anyway.
 
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mj2k

mj2k

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Is that top bolt stripped? or have the thread from the hole in it?

The smaller VW and audis are good, a nice design means you can replace all the discs without removing the carriers.

Heh, I got the feeling you'd mention that. Not stripped but still had a coating of aluminium on the threads from earlier Subaru rear brake experiments using a cheapo Chinese brake adaptor with poorly cut threads (this saved around £1400 off a used Brembo upgrade); cleaned them up with a dye before use on the Abarth.

Normally the carriers aren't such a big deal as long as the bolts aren't rusted solid (and it makes brake upgrades easier), just this particularly crackers choice in bolts which makes it much more of a pain
 
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mj2k

mj2k

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Here's a pic of the bonkers clearance issue. Somebody on another forum with a 695 had exactly the same issue, so at least I know I'm not going mad :)

Go396y.jpg
 

A3jeroen

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All the time since you started this thread I'm trying to remember how I changed the discs on my 100HP as well on my son in law's Bravo...
I think I used a Allen socket on my socketset without any problem. I have a set of 1/2" long and short sockets from 4 - 12 mm and I think I managed to undo these bolts without a problem.
I mean if I did have a problem I'd remember and I can't imagine FIAT using different bolts for the Abarths.


gr J
 
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mj2k

mj2k

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All the time since you started this thread I'm trying to remember how I changed the discs on my 100HP as well on my son in law's Bravo...
I think I used a Allen socket on my socketset without any problem. I have a set of 1/2" long and short sockets from 4 - 12 mm and I think I managed to undo these bolts without a problem.
I mean if I did have a problem I'd remember and I can't imagine FIAT using different bolts for the Abarths.


gr J

The corner of the suspension arm gets in the way, I guess it's not that clear from the pic but unless you've got some clever form of super-strong wiggly articulated allen key there's no way it's fitting in there without removing (or at least significantly loosening) the rear stub axle, or grinding a bit off your suspension arm.

I presume there was no 'joined up thinking' when designing those two components and they were created separately, but extending the suspension arm and putting a hole in it for reaching the hex bolt would be one way to work around it without affecting rigidity, or simply use strong enough standard bolts.

BTW removing it on the other side was much quicker once I'd refined my technique - remove all the stub axle nuts but leave the ABS sensor alone, screw the nuts furthest from the caliper mount bolt back on a few threads, stick a long socket extension (or other blunt pry bar) between the stub axle and arm, and give it brisk whack with a small hammer to break the stub axle free. Swing the stub axle outwards, and then a standard Allen key with a ring spanner over the end will fit in (still no room for an allen socket) and break the silly bolt free with the minimum of hassle. So an extra 20 mins wasted time screwing / unscrewing stub axle nuts (and according to the FSM they should be replaced once undone once; think I'll live with that though) and it'll be quicker next time with my nice, Subaru caliper bolts :D
 
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