Hi all, I have a 73 Fiat 500R and over the last summer, one by one all of my wheel cylinders started to seize up on me. I removed all four and ordered new ones from MrFiat for the 500R. 23mm fronts and 15mm rears which match the ones I already had on the car. The rear ones went in just fine with room for the drum to spin freely but once I replaced the fronts I am unable to put the Drum back on due to the cylinders not retracting in or back enough to allow the shoes to fit inside the drums. After taking the old ones and new ones apart I noticed that the new cylinders have longer pistons in them then the originals and they end up touching each other inside the cylinder when compressed all in the way. Does anyone know if these cylinders come in different piston lengths and which ones should I be ordering?

Never ever heard of different brake cylinder piston lengths.

Neither have I until I ran into this problem and took them apart. I have added some pictures to better illustrate the issue. The cylinder on the left is the new one I just purchased and the one on the right is the one I just took off the front brakes. Not only are the pistons longer on the inside but the posts that stick out from the rubber are longer as well and prevent the shoes from closing enough to clear the drum.

I have seen other Fiat models that have the same mounting base as the 500 ones. Those must be for a different model car. Not the best but can you recycle the pistons from the originals to get you going?
I can check some of the ones I have here in the morning out of interest.

F123C Al that is . Your post on this subject seems to have gone astray. I got an email notification about it but it has not appeared here. I have been checking parts which is quite interesting.

Thanks Toshi, I do think I was mistakenly sent the wrong parts even though the packages were marked with the correct part # listed on the website. I am in the process of rebuilding the old cylinders just so I could get my car moving but I wont trust it for anything other than getting my car back into storage until I get the correct parts. I guess what I would like to know is if anyone has the correct Fiat part # for the 23mm front cylinders for the 500R just so I know if I am ordering the correct parts. I did find a part on Axel Gerstl website but I am unsure what the 190mm is refering to. Wheel cylinder, front (23.810 mm) Fiat 500 R/126 1.series (pitch circle 190mm)

I suspect the 190mm has to do with the size of the drum.

OK I was going to wait until Al was able to respond however I had a rummage this morning. I have a number of brake slave cylinders that I have purchased over the years, all of which were advertised as for the Fiat 500. 3 sets are standard 19mm bore for the 500F/L and two sets of the 23mm for the 500R. I opened up the packs of the 500R ones and dismantled the cylinders. One set is the same as the new ones you just got and on set is the same as your old ones. As you say there is a huge difference in overall length.

Stop press , that was wrong just put them back together and checked overall length when compressed. Although the piston arrangement is much longer on one set when I compressed them with my fingers the overall length Was actually about 1mm shorter than the ones that might be regarded as the more traditional design, 69 & 70mm.

Thanks Toshi for those measurements. I just went to measure mine to compare to your measurements. My new cylinders fully compressed are the same as yours (70mm) but my old ones fully compressed are (60mm). A huge difference. Both are 23mm diameter. I also went ahead and measured the inside of my front drum and it is 170mm (diameter) friction surface to friction surface. I am running with the traditional fiat 500/126 rim that came with the 500R.

Ironman34 said:

Thanks Toshi for those measurements. I just went to measure mine to compare to your measurements. My new cylinders fully compressed are the same as yours (70mm) but my old ones fully compressed are (60mm). A huge difference. Both are 23mm diameter. I also went ahead and measured the inside of my front drum and it is 170mm (diameter) friction surface to friction surface. I am running with the traditional fiat 500/126 rim that came with the 500R.

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That all sounds right so something wrong going on here.i assume you are fitting the original shoes?

Oh just thought have you moved the self adjusters on the brake shoes?

I think that you will find that the '190' refers to the wheel bolt pattern, which on all the 500s and the Mk1 (594cc) 126 had the 190pcd wheel bolt pattern (sort of, a wheel bolt at each corner of the wheel). The Mk2 126 models had what became the Fiat standard, 98pcd wheel bolt pattern. I think that you will find that the Axel Gerstle parts to be fine---I have bought a lot from them over time, and never had a problem.

I am using the original shoes. They still have plenty of life in them. I originally just fit them back on without playing with the adjusters and when they didn't fit in the drum I reset them back and they still didn't fit. The part that is still stopping me from putting the drum back on is the cylinder pistons. The extra 10mm that they are longer than my originals is just enough for the shoes not to fit in the drum. I guess I will have to reach out to Axel and MrFiat and hopefully they will be able to measure their parts for me to see if they do have a cylinder that is 23mm and compresses down to 60mm. Axel has two listed on their site for 500R fronts so hopefully one of them is the one I am looking for. Thank you Hobbler for clarifying the 190mm measurement for me as well.

Having dug out my new brake cylinders if anyone is wanting any 500F/L or 500R front ones I would post for £12 a pair which I think is cheaper than any others I can find. Otherwise I will just put them back in store.

Toshi 975 said:

Having dug out my new brake cylinders if anyone is wanting any 500F/L or 500R front ones I would post for £12 a pair which I think is cheaper than any others I can find. Otherwise I will just put them back in store.

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Still got 2 sets of 500D/F/L new brake cylinders left and one new pair of brake shoes ?