1966 230SL rear wheel cylinder bore?

[Jim C]

Hi, I need to replace a leaky rear wheel cylinder on my 230SL and cannot find the 23 mm bore cylinder that is currently on the car.  Do these exist anymore?  Parts places claim the correct bore is 19 mm.  Is this a replacement bore?  I planned on only replacing the leaking cylinder.  If I change to 19 mm, I believe I would need to do both to get the same pressure on both sides, correct?

Thanks,

Jim

[Benz Dr.]

I believe that they are 19 mm so that info is correct. 23 mm sounds more like what you would find on a 190SL which are 15/16''.  The larger cylinder would give you a bit more braking but it wouldn't be a lot more. Best to have them matched I would think.

[Jim C]

Thank you for your response.  I pulled the cylinder from the car and cleaned it up.  I measured the bore (~23 mm) and the outside of the cylinder has a very large 23 on it.  This is an ATE cylinder which I have never replaced (owned car since '83).  Do you think the original owner had the cylinders replaced at some time with 190SL parts perhaps?

I don't mind replacing both (I have one replacement 19 mm cylinder in hand that I was going to return), perhaps I should check the other side to verify it also has a 23 mm cylinder. 

I guess my question is, are the 19 mm cylinders OE for this car?

Thanks again,

Jim

[badali]

See if this repair kit is still available from the classic center.  Here is the part number. 000 586 12 42  It is 19.05 mm

[Benz Dr.]

I have a better idea. As long as the cylinder bore isn't pitted, and likely will be, go to NAPA and get some 3/4 '' brake cups. It it's pitted, get a new one because it will always continue to leak.
I use brake grease around the piston and under the cover on each end. Moisture is your enemy here so any way you can kep it away from the cylinders is a good idea. This system isn't air tight so you should also bleed the brakes every year.

[twistedtree]

Personally, I'd put both sides back to the original 19mm.  The 23mm cylinders will generate more breaking power relative to the front brakes than 19mm, and I'd be worried that in a panic stop you would get premature locking of the rear brakes.  I would also only use matched sizes side to side for the same reason.

[Jim C]

OK, so it looks like the consensus is that 19 mm bore wheel cylinders are the OE size for these cars.  I'll replace both.  The leaking 23 mm cylinder is pitted and I believe sleeving would be cost prohibitive.

Thanks to all responders!

[ctaylor738]

White Post Restorations in White Post VA did a pair for a 230SL for me, using brass sleeves.  I don't recall the exact price, but I think it was around $60 apiece.

[Jim C]

Well, I decided to go with the new 19 mm cylinder on the right rear (leaky side with a 23 mm cylinder).  I checked the left side and, what do ya know, its 19 mm.  Its not leaking, but the rubber dirt covers are rotted.  I'm going to order another 19 mm cylinder and replace the left rear.

I've had this car for almost 30 years and never noticed that one side was 23 mm and one was 19 mm.  This is the first time the rear brakes have needed attention.  There is plenty of shoe material present, so they don't need replacing.

Jim