At first, yes. Once it's broke in, though, it won't stretch any farther. If you worry about it being too big after it stretches out, you might go a size smaller than what you really need so that it will be right after it's stretched.
Smrobs...I have both English and western mohair and haven't noticed the stretching. I probably am not very observant. There is also a slight variation in the horses' roundness depending on the time of year so that may account for not noticing. I sure do like the mohair though!!!
Mohair cinches still stretch but not near as bad as the alpaca cinches. The last one I bought was a 5-star mohair cinch and it has held up great. Pricier than other brands but theirs don't stretch nearly as bad as other brands. Classic equine also make a good one.
For what it's worth, the only reason I even noticed the stretch in mine was because I bought 2 identical cinches at the same time. They were the same size when I bought them but when I went to switch them out after having used the first for a while (switched them out to wash the first one), I noticed that it was about 2 inches longer than the new one. So, my cinch that started as a 28 ended up as a 30. Not a huge deal as it still fit most my horses.
The thing that bugs me when buying new mohair OR alpaca cinches is some brands take the stretch into account and some don't. As a matter of fact, I have a sneaking suspicion that sometimes the same company labels them differently but I can't be sure because I have bought my cinches over several years time.
For instance, I have bought 34"s that when they arrive, brand new, actually measure 34". I have returned or sold them because I knew they would stretch out to a 36" and be too large for my horses. Then I have also bought sizes smaller than I need (say like a 32" for instance) to try to get a 34", but when the 32 arrives it measures 30", so they are accounting for the stretch. So that makes buying cinches a bit frustrating.
I usually buy Classic Equine but have also bought a Weaver. So don't know exactly who measures how, but I kind of think my Classic Equines have come both ways.....accounting for the stretch and not accounting for the stretch. But any mohair or alpaca cinch I have had stretches approx. 2 inches. They then stabilize and don't seem to stretch after that.
I think, generally speaking, you buy the size you want to end up with, just beware that if it arrives measuring the actual size you actually want, it will stretch two more inches. So you want it to arrive measuring shorter than what it says on label. They mostly arrive that way.....mostly.
Our horse has been ridden in a 36 Weaver Felt Smart Cinch for almost 2 years.
I got an Classic Equine Alpaca string cinch about 3 weeks ago.
Whomever posted that varying sizes can depend on the manufacturer is dead on. Due to possible (probable) stretching of the Alpaca, I wanted to go at least 1 size smaller. A 34 Classic Equine Alpaca was the same size as our 36 Weaver Felt Smart Cinch. So, we went with a 32.
I have seen at least a 1" stretch so far.
I rinse the cinch once a week.
The cinch fits great. Even if it stretches another 1", we'll still be fine.