Hi Max,
Thanks for that info - unfortunately as your post indicates some of the handful of listings for suitable belts just don't have enough info to know exactly what the specs of the belt they're selling or recommending are. My limited new understanding of belts is as you indicate that length is always done by referring to internal circumference.
So yes that belt (Gates 6738) has an outer circumference of 965mm (28") but going by the Gates catalogue that i used it's M belt equivalent is 36.5 - unsure how they calculate this but I know that Gates are regarded as making among the best belts on the market and thats good enough for me.
I agree that it'd be ideal to be able to go and try belts at a supplier but alas where I'm located there's limited suppliers, I'm well out of town and transporting my mower in our smaller hatch wouldn't really work.
Like i said I can only assume that the 550 Pro came with different pulley sizes or something as there's odd stuff in the belt listing for it - both on ODK store and others. I am unsure if the suppliers are getting confused between it and the 505 (I think there's a Victa model of this number).
At the end of the day I did try and fail to get any info on here as to the correct belt size for nearly a month now - I can only assume folks weren't sure or it's a tricky area. I just had to act and the experience with the M36 and M37 combined with the [Censored] listing which stated this belt by name made me pretty sure it's correct for me - especially given referencing it in the Gates catalogue.
I managed to order from Amazon and while they sell them for $75+ here, I got 2 delivered for just a tad over $50.
Wow I cannot believe your 550 Pro has an M34 belt on it! You must have significant differences in some area to mine - either pulley size or similar. Definitely a confusing item to buy, too much conflicting info on it - but much thanks for your assistance.
