Lately many producers have presented new models of electric mountain bikes with 27,5 Plus tyres. This is a new format which is gaining more and more success in the world of (electric and non-electric) mountain bikes. We think that 27,5 tyres make more sense on an electric mtb than on a standard one. Read this article to find out why.
Short history of mtb tyre sizes
In order to really understand what a 27,5 + tyre is, it is necessary to delve a bit into the history of mtb tyre sizes.
- For many years bikers were content with 26″ tyres, and MTBs were only available in that size
- A few years ago 29″ tyres started to emerge: these allowed for a lesser rolling resistance, a better angle when attacking obstacles; on the other hand, they are harder to accelerate and allow less agility in handling the bike
- The market then came back on its steps, and has (had?) more or less stabilized on the 27,5″ format, a good compromise between the two extremes. 26″ and 29″ tyres are still very widespread, and find their (wide) niche.
- In the last couple of years another fad exploded: that of fat bikes. These have a nominally 26″ tyre, but the tyre is so wide and fat (between 3,7″ and 5″) that the diameter is practically that of a 29″ tyre. Many bikers have tried this bikes and could note the advantages of such large tyres… noting their defects as well.
- That’s how we finally arrived to the 27,5″ Plus format.
27,5 Plus tyre size: what does it mean?
These are basically tyres with a 27,5″ diameter; they are wider than normal, but not as much as happens on a fat bike: once again, a compromise between two extremes.
The tyres are usually between 2,8″ and 3″ large. The real diameter is closer to that of a 29″ tyre, with a bigger air volume inside though.
What this actually means is that you have two advantages and two disadvantages (to simplify a bit):
- better traction when going uphill, which you will notice especially on very uneven surfaces
- better “floating” downhill
- you will also notice a higher friction uphill, especially on even surfaces such as asphalt
- the tyres weigh more. Remember that adding weight to the tyres is particularly bad for performance, much more than adding weight to the fixed parts of the bike such as the frame.
Why the 27,5 Plus standard makes more sense on electric mountain bikes
Because on an e-mtb you make the most of the advantages and you are not so bothered by the disadvantages of 27,5 Plus tyres.
- better traction uphill helps to efficiently use all the torque generated by the biker + motor system. This is important especially with the latest-generation high-torque motors, such as the Bosch Performance Line CX. The typical e-mtb user is also probably less technically expert than a “normal” mtb biker, and so the better floating of the tyre will help to forgive minor technical imperfections in the trajectory
- Electric assistance makes the higher friction and weight less important, especially with latest-generation high-capacity batteries that are now available
The models of 27,5 Plus e-mtbs available in 2016
In the last few weeks many e-mtb producers have presented their 2016 range. Almost all the major producers have decided to include a 27,5 + model in their range. We have already talked about Specialized and Rose. Here is a quick look at more models:
KTM Macina Kapoho
With the new Bosch Performance CX motor. Tyres 3″ wide. 130mm travel. 4299€ for the Shimano version, 4899 for the Sram version.
Cube Stereo Hybrid 140 27,5+
3″ here as well. 140mm travel. Colors… debatable. 4999€
Bulls E-Stream Evo
This is also available with 27,5 + tyres. Notice the high-capacity (650Wh) battery. Brose motor.
Haibike (various 2016 models)
Haibike has inundated the market for 2016. Some sport 27,5 + tyres, like the XDURO HardSeven RX which you see here. Consult our special on the Haibike Xduro3 series for more details.
Scott e-Genius and e-Contessa
With a Bosch Performance CX motor. 140mm travel. 3″ tyres. Available in two versions for hom (e-Genius 710 Plus and 720 Plus, with different components) and one for her (e-Contessa Genius 720 Plus).
We don’t know yet whether the 27,5″ Plus tyre standard will be successful, or whether it will turn out to be just a fad. Its success will definitely be more likely on electric mountain bikes, where its advantages are highlighted and its downsided have a diminished importance.
Do you agree with our analysis? What do you think about this new format?