Answered 29 versus 27.5 in terms of power

[Grovester]

Hi,

I have recently replaced my 29 wheel bike with a 27.5 wheel bike but weight, gearing and motor are the same.

I always need to do 3miles road ride to get to the trails and I am convinced that this road ride is much more effort / power with the 27.5 wheels... or I have lost fitness

Can anyone tell me if the 27.5 need more effort/power for the road ride and explain why.

Thanks, Phil

 

[Zimmerframe]

I guess a 27.5 will spin up/accelerate faster as it's smaller. Where as a 29 will maintain speed easier because it's larger/heavier.

Maybe your 27.5 tyres are new and your 29's were worn so there's more knob drag too ?

With the 27.5 the effective gearing will be lower than it would be on the 29, so you might find that to go the same speed you're selecting a higher gear which is making it feel a bit harder ?

 

[Mikerb]

2 bikes may differ in many other aspects besides wheel size. The Geo may be different and also the kinematics at the rear.

 

[mtbbiker]

Is it possible you are hitting the speed limiter. If you didn’t do a wheel size change to the computer, the 27.5” will show a faster speed than what you are actually doing. Just a thought

 

[Mikerb]

I interpreted the OPs post as he had changed bikes albeit with similar weights and the same motor..............rather than having just swopped out the 29er wheels on an existing bike with 27.5.

 

[Grovester]

Hi, yes it was a bike swap from a Cube Stereo Hybrid 140 TM 29"wheel to a Cube Stereo Hybrid 160 Race 27.5" wheel.

So different geometry, but weight, motor and gearing the same. I was out on it yesterday and felt better so maybe it is just in my head.

Just googled it and found the following:-

What is the difference between 29 and 27.5 wheels? Simply put, a 29er offers more speed, efficiency and stability, while a 27.5-inch bike offers a snappier trail feel.

So I guess this means the smaller wheel needs more effort/power. Can't quite work out the physics though.

 

[andyb2]

if the chainring and cassette are the same, the 27.5 will be lower geared (you'll need to pedal more to go the same distance as on a 29, but it should be easier)

As to whether you'd notice this above bike weight / tyre differences, I've no idea

 

[Gyre]

I think @Zimmerframe is onto it. If your 27.5 knobbies are more difficult to pedal on asphalt, I'd look to the difference in tires. Either knob wear, knob pattern/height, heavier casing, softer compound, or different tire width could be factoring in.

 

[JP-NZ]

Just googled it and found the following:-

What is the difference between 29 and 27.5 wheels? Simply put, a 29er offers more speed, efficiency and stability, while a 27.5-inch bike offers a snappier trail feel.

So I guess this means the smaller wheel needs more effort/power. Can't quite work out the physics though.

I thought this was common knowledge, 29" wheeled bikes are faster climbing and on the flat. There is a reason why XC racers all race on 29ers

 

[Mikerb]

I thought this was common knowledge, 29" wheeled bikes are faster climbing and on the flat. There is a reason why XC racers all race on 29ers

...simply because they have less rolling resistance especially off road .....and being a bigger diameter carry more momentum.