Rear caliper replaced

I'm beginning to think I'm missing something as I've rebuilt a few calipers, as well as master and slave cylinders in the past and it's been a pretty straight forward process. There are generally only 3 components, the cylinder, the piston and the seal. The piston has a tightish fit, but basically holds the seal in place, which as long as the cylinder walls are clean and smooth (without scoring or pitting - which the honing tool is require to fix) creates a fluid tight seal. So fixing a leaky cylinder is just replacing the seal and boot.
Where you have a locked up brake caliper, it is corrosion, simple as that. So a slightly more comprehensive rebuild is required, which is first removing the piston, tidying that up, and even with some pitting on the piston isn't a major, as it's the seal that is important. The big issues is the condition of the cylinder, as that needs to be restored to as smooth as possible (no scoring or pitting), if the cylinder is heavily scored, you need a new caliper.

(edit) Looking at the price, if the piston is even slightly dodgy, I'd just stump up and buy new ones. Add in Seals and Boots at $9 a pair and you only need to worry about the caliper.

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I have all the calipers off my project. I rebuilt the front real easy. I took a rear one apart and I think it will be tough to get it back together with the tools I have. There are special six sided tool that fits to a ratchet for turning the piston on these types of calipers. I have one now. but moved to engine work.
 
The piston is in constant contact with the seal, and general failure is between the piston and seal, as the piston is the moving part. The issue with the condition of the cylinder of the caliper is critical as it does contact the piston to some degree as this is what fuses when the brakes seize. It is critical to hone the cylinder so as not to score the piston otherwise the whole exercise is a waste of time and you're up for another new piston. I personally am less interested in the grove in the caliper and more interested in the condition of the cylinder wall. Obviously everything needs to be tided up but there are those that have raised the question as to why bother honing the cylinder.
As I said, if the caliper assembly is in good nick, then it is just seals and boot. If it's seized, they I'd go with new pistons and honing the cylinder.
There are many cleaning and polishing heads for a dremel tool, and is a must have tool for the fiddly stuff, especially if you use the dremel flexi-shaft attachment. All up, well worth the $150.
 
Tedd said:
There are special six sided tool that fits to a ratchet for turning the piston on these types of calipers.
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Judging from past posts about this, that tool does not seem to work well on the rear X1/9 calipers. I don't recall exactly why but several members found the same result.

If you are seeking a tool to assist with it, perhaps look at a kit similar to this:
https://www.amazon.com/gp/product/B0122Q83T4/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
This has been successfully used by several.
 
I use the cube tool, but slightly modified.

I ground off all the ears except the ones that fit our pistons. The cube fits much better in the caliper that way.
 
Andy said:
I use the cube tool, but slightly modified.

I ground off all the ears except the ones that fit our pistons. The cube fits much better in the caliper that way.
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The difference is width of the caliper. On newer cars the caliper has to be wider to accommodate wider vented rotors in back, so the cube tool fits unmodified. On our cars with skinny solid rotors, the caliper is narrower so to use the cube tool you have to shave off the unused nubs to get it to fit. :)
 
toddr124 said:
I finally started working on the rear brakes of the blue 86 X1/9. Rear passenger brakes were frozen in place. Removed the pad, yes only one side still had any pad. Went to turn i the rear piston and it was frozen in place. Took a real long pipe and I was able to turn the piston. Now the piston turns hard, but does not go in.
Any idea beside replacing the rear caliper?
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I'm glad I saw this thread, it reminded me to get going on my 38mm rear caliper upgrade. I had disassembled, blasted, cleaned, helicoiled and prepped the caliper bodies and collected all the replacement parts needed (one of the adjusters screws was broken in half!) except for ordering a new piston. After seeing this thread I looked again and happened to snag one from eBay seller dgrally in the UK. When that gets here I'll use Tom G's excellent "Rear Caliper Rebuilding For X-Head Dummies" LOL :p illustrated write-up to help me reassemble them.
 
Dr.Jeff said:
Dan, are you boring out the stock calipers for the larger pistons, or did you find some complete replacement 38mm calipers? If the latter, which ones did you get? Thanks.
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Ralph (aka "lanciahf") had two 38mm calipers left over from his Scorpion project so I got them from him. One is a genuine FIAT item and the other is a European aftermarket item. Both needed a lot of work (helicoiling the threaded fitting openings, new pistons, new adjuster and ball bearings on one, new rubber goods, etc.). In the end the overall spend on them will probably be more than the Chinese ones that have come onto the market in the past year or so, but some folks here who have purchased the Chinese ones experienced some quality issues so I wanted to stick with OEM or Euro aftermarket.

As pointed out by someone here (sorry, name escapes me), if you wanted to actually mod the original 34mm calipers to 38mm, even though the exterior of the caliper casting appears to be identical (except for the part numbers of course) it would be a bit of a chore. First, since this caliper design does not have any sort of built in mounting holes/tabs/etc, you'd have to fab up a jig to securely hold them in place for accurate and repeatable machine work. Then you'd bore out the inner diameter to fit the 38mm piston, in an of itself not that big of a deal on a Bridgeport with the right sized boring head. Probably the most difficult part would be crafting the tool bit needed to deepen the seal groove without widening it--that's very sensitive to tolerances to prevent seepage. Unless you have access to really good equipment and plenty of time for trial and error, probably more economical to recon real 38mm units or buy the Far East knock-offs (and maybe install OEM internals?).
 
Eugene Harvey said:
I'm beginning to think I'm missing something as I've rebuilt a few calipers, as well as master and slave cylinders in the past and it's been a pretty straight forward process. There are generally only 3 components, the cylinder, the piston and the seal.
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Rears are way more complicated:

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lookforjoe said:
Rears are way more complicated:
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True, but I was lucky with the rears as the pistons and cylinder were in good nick so was only a seals and boot job. My main throw away on this is that if you're faced with seized brakes then a partial rebuild is required, which will be new piston (probably the most critical component and for $30, just buy a new one), seals and honing the cylinder. As Dr Jeff also points out, honing is only a gentle process as you don't want to remove too much, just to smooth the lining, otherwise you end up boring out the cylinder, and then need to try and source an alternative size piston.
The whole point of this line of response was to a question as to why bother with honing as some thought it of no value and just want to clean the grove in the caliper.
The point being, there is no one solution to remedying brakes, it's all dependent on the state of the components. A regular service for a leaking caliper could be a $10 job for seal kit, $40 if the piston is worn, and possibly the same for seized brakes if you can hone and recover the cylinder, otherwise it's $300 for a whole new or rebuilt assembly.
Well not $300 for everyone as there will be those capable of boring out a cylinder and relining it or using an alternative cylinder. That's not me, when they're that far gone I'm in the $300 pool.
 
Eugene Harvey said:
Sure, there could be some corrosion in the grove in the piston in which the seal fits, and if that's stuffed, I'd just use a Dremel tool (or similar) followed up with a bit of folded 320 to finish.
View attachment 17364
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Lots of crud and old rubber was stuck in the groove, and it's hard to see and get out. I ended using a Dremel as well. But I was hoping for a specialized tool existed to clean and true the groove.
 
Finally finished the brakes and drove the car today. I bought a new rear caliper from Vicks and it went right on. I loosened the ebrake cable so I could remove and install the new caliper without a big wrench. Well worth the 30 minutes of cussing... work. Always good to work with parts that work.

I bought a cube to tighten rear calipers a few years ago and it works poorly. I got a big metal chisel and ground the tip flat to fit the piston groove. The chisel I use fits in a 19mm socket. Very easy to screw the piston in most of the time with a 1/2 inch ratchet. Well worth the $12 chisel I ruined or fixed.
 
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