Correct belts for ALT/WP 1985 300CD- 10x1035 look too thin! - Page 2 - PeachParts Mercedes-Benz Forum

BillGrissom · #1 04-16-2023, 01:34 AM

As I recall, in my 1985 300D, they ride "just right" like posts 11 & 13, not "too high" like post 5, or "sunken" like post 9, though all probably work fine. Main thing is that the two are matched, though even that doesn't matter if they follow different routes like some engines in post 11. Rock lists AC Delco 15405 (10 x 1029 mm), Gates 7405 (10 x 1029 mm), Dayco 15405 (11 x 1029 mm), and Continental 15411 (11.5 x 1044 mm). The lengths are "effective length", which is 1.5% less than "outer circumference". Unsure about Continental since they spec as just "Belt Length". I found various manufacturers spec lengths differently (not always defined), when I sourced a belt for my 1965 Dart, where length was critical since limited adjustment in a custom AC bracket I fab'ed. Went thru 3 belts before I found a good fit. Trying to estimate length from a rope measurement made it tricky.

It looks like the Dayco and Continental belts may ride a bit high since wider. Strange since those 7/16" and 15/32" widths, resp., don't appear to be standard. A Gates catalog I downloaded has belts of 3/8" and 1/2" widths, with an oddball at 13/32" (states 9.5/10 mm in parenthesis, though 10.3 mm). That range suggests anything from 9.5 to 11.5 mm width is considered interchangeable, as does Rock's listings.

ROLLGUY · #2 04-16-2023, 10:10 AM

Quote:

Originally Posted by BillGrissom

As I recall, in my 1985 300D, they ride "just right" like posts 11 & 13, not "too high" like post 5, or "sunken" like post 9, though all probably work fine. Main thing is that the two are matched, though even that doesn't matter if they follow different routes like some engines in post 11. Rock lists AC Delco 15405 (10 x 1029 mm), Gates 7405 (10 x 1029 mm), Dayco 15405 (11 x 1029 mm), and Continental 15411 (11.5 x 1044 mm). The lengths are "effective length", which is 1.5% less than "outer circumference". Unsure about Continental since they spec as just "Belt Length". I found various manufacturers spec lengths differently (not always defined), when I sourced a belt for my 1965 Dart, where length was critical since limited adjustment in a custom AC bracket I fab'ed. Went thru 3 belts before I found a good fit. Trying to estimate length from a rope measurement made it tricky.

It looks like the Dayco and Continental belts may ride a bit high since wider. Strange since those 7/16" and 15/32" widths, resp., don't appear to be standard. A Gates catalog I downloaded has belts of 3/8" and 1/2" widths, with an oddball at 13/32" (states 9.5/10 mm in parenthesis, though 10.3 mm). That range suggests anything from 9.5 to 11.5 mm width is considered interchangeable, as does Rock's listings.

Nice research thanks! However, now I am more confused!

BillGrissom · #3 04-16-2023, 06:38 PM

Quote:

Originally Posted by ROLLGUY

Nice research thanks! However, now I am more confused!

Yes, definitely confusing that both belts you bought spec 10 mm width, yet seem to differ widely in actual width. Also strange that a catalog lists 0.47 mm width and in parenthesis says is 9.5 or 10 mm wide. Can't be both, so must means "works for both specs", and is actually 11.9 mm wide. Also why do 2 belts w/ same PN 15405 have different widths. Mysteries of the universe. Perhaps Rock's listing have mistakes in the dimensions stated.

ROLLGUY · #4 04-17-2023, 09:37 AM

Quote:

Originally Posted by BillGrissom

Yes, definitely confusing that both belts you bought spec 10 mm width, yet seem to differ widely in actual width. Also strange that a catalog lists 0.47 mm width and in parenthesis says is 9.5 or 10 mm wide. Can't be both, so must means "works for both specs", and is actually 11.9 mm wide. Also why do 2 belts w/ same PN 15405 have different widths. Mysteries of the universe. Perhaps Rock's listing have mistakes in the dimensions stated.

Actually, I ordered two 10X1035, and a PS belt (13 wide), and when they arrived, I assumed the 10 wide belts were wrong. They looked exactly the same (thin) as the belts on the car I was replacing. I sent them back (in retrospect a dumb thing for me to do), and ordered 13X1040 thinking that they are correct, and all the online Euro parts catalogs were wrong (another mistake on my part). I should have just kept the 10 wide belts, rather than paying $13 to send them back! I ordered other parts for this car, and was waiting for them so I could replace everything at once. I wanted to have all the parts in hand before starting the work, but now I am not sure the 13 wide belts will work. I will be getting another set of 10 wide belts soon, and will see which ones work best. Either way, I will be getting an education. Even though it cost me about an extra $50 (13 wide belts + shipping, and return shipping for the 10 wide), I will be a belt expert!

ROLLGUY · #5 05-01-2023, 11:10 AM

I finally got a chance to work on the car, and I found out why it had thin belts. It turns out that I was mistaken, thinking that 10 wide belts were wrong for the alternator/fan (that is what was on the car). After removing the belts and comparing them to new belts, they were thinner. I inspected the pulleys, and found so much rust in the grooves, that they "sanded" the belts down on the sides, making them thinner. The size belts listed in all the online catalogs I looked at were correct. When I originally looked at the belts on the car, and seeing that they were Continental 10X1035, I assumed they were too thin, so I ordered 13 wide belts.

Since finding rust pitting on the pulleys, I had no choice but to replace them. The water pump pulley was no problem (I had a replacement), and the power steering pump pulley just needed a little cleanup with a wire brush on my drill. However, the crank pulley was VERY difficult to get off! I had to cut off the outer part of the pulleys to gain access to the stripped socket head bolts, in order to get my drill in straight (even with the radiator removed, I had to shorten a drill bit). I was able to use a screw extractor to removed the stripped screws.

I installed a good used pulley and the new Continental belts, and everything works great!