27.5 or 29, Is there much difference???

On the verge of ordering a rim for my new build but I’m stuck deciding between 27.5 and 29. I used to have a 29 Nimbus muni which mainly got ridden on the road and hardpack trails and my new uni will probably get the same kind of use, what would people recommend or isn’t their much difference when it comes down to it?
Crank wise I’m gonna run some 125/150’s.

You can work out the percentages easily. In theory, there is very little difference in diameter, and therefore in speed for any given cadence. However, the determining factor will be the choice of tyres available. On the whole, 29" tyres are fatter and gripper and more suitable for riding on unmade surfaces. I have a 700c and a 29. The 700c is much lighter and more nimble, but is hard work off road. The 29 rolls over most things but is a bit heavy for sudden changes of speed or direction. Think what type of riding you want to do on, it, look at the tyres available, and let that make your decision.

I’ve ridden both off road. Prefer the 27.5. If you like hills and more technical stuff 27.5 for the win. If you’re bigger and or prefer more cross country the 29. I think the 27.5 is more versatile. I have a 36 for road and easier cross country.

Well where I live is very hilly, I could manage the 29er I used to have but it tired me out very quickly so I’ve gone for 27.5. Can’t wait to get the wheel built up this week!

I know that actual rolling diameter varies between tyres, and that sizes are therefore only nominal, but 29 is only 5% more than 27.5. This is negligible in terms of speed or leverage/gearing. It’s a much smaller effect than swapping between 150 and 125 mm cranks, for example.

Phew… Thought I was going to have to buy another uni…

Well the build is on, Nimbus steel disc hub, KH freeride 27.5 rim and some stainless sapim spokes.
That’s my job at work this Thursday sorted, can’t wait to get it built and rideable!