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Breaking the 27.5-Myth [VIDEO]

PB Forum :: 27.5/650b
Breaking the 27.5-Myth [VIDEO]
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flag hig4s
Posted: Aug 23, 2015 at 10:34 Quote
a-d-e wrote:
hig4s wrote:
One of the advantages of 29 over 26, (other than the being 10% taller for roll over,, 27.5 is 5% taller than 26, half way in between) is the difference in handling by being more in the bike than on it.

with most 26in mountain bikes, to get reasonable clearance the crank center is above the axles. With the weight of the rider being applied above the axles the bike is more tippy. 29s have the axle higher than the center of the peddle crank.

with most 27.5in bikes you get back half of the quick response from the smaller lighter wheels and tires, half the roll over advantage of the 29, and still have the center of the crank below the axles so retain most of the stability of the 29.
probably completely wasting my time but.... crank height is exactly the same on 26 27.5 29. just the wheels are different sizes & thus the differing radius would therefore put axles higher or lower relative the the bb.
lesson over.

right, I believe standard BB height is 14" to 15" With 26" wheels and mbt tires the axle is about 14", 27.5" wheel the axle is 14.7" and 29" wheel the axle is about 15.5" so most 26" bikes the BB will be above the axle, most 29" bikes the BB will be below the axle and on 27.5" bikes it can go either way but I believe most are below the axle, mine is.
flag a-d-e
O+
Posted: Aug 24, 2015 at 12:10 Quote
hig4s wrote:
a-d-e wrote:
hig4s wrote:
One of the advantages of 29 over 26, (other than the being 10% taller for roll over,, 27.5 is 5% taller than 26, half way in between) is the difference in handling by being more in the bike than on it.

with most 26in mountain bikes, to get reasonable clearance the crank center is above the axles. With the weight of the rider being applied above the axles the bike is more tippy. 29s have the axle higher than the center of the peddle crank.

with most 27.5in bikes you get back half of the quick response from the smaller lighter wheels and tires, half the roll over advantage of the 29, and still have the center of the crank below the axles so retain most of the stability of the 29.
probably completely wasting my time but.... crank height is exactly the same on 26 27.5 29. just the wheels are different sizes & thus the differing radius would therefore put axles higher or lower relative the the bb.
lesson over.

right, I believe standard BB height is 14" to 15" With 26" wheels and mbt tires the axle is about 14", 27.5" wheel the axle is 14.7" and 29" wheel the axle is about 15.5" so most 26" bikes the BB will be above the axle, most 29" bikes the BB will be below the axle and on 27.5" bikes it can go either way but I believe most are below the axle, mine is.
I guessed correct! completely wasting my time.
flag Canbot
FL
Posted: Aug 26, 2015 at 21:31 Quote
Singletrackmac wrote:
NMK187 wrote:
Singletrackmac wrote:
Results make sense. 29er has the advantage in rolling faster for the flat, and the 26" has the advantage of better geo and maneuverability for the DH. 27.5" has much less rollover than the 29er and while it does have more rollover than a 26", it is only 1/2".

That small 1/2" increase comes at a big cost to maneuverability with needing to have a wheel that is 1" larger to gain the 1/2" of rollover. It's not just the moment of inertia from the bigger wheel that hinders it's maneuverability, but the negative effects on the geo to fit the 1" larger wheel as well with a higher stack, longer chain stay, longer wheel base and increased BB drop. This along with a heavier and larger wheel/tire negate whatever gain you get from the measly 1/2" increase in rollover.

The 29er also losses in maneuverability vs the 26" with it's larger wheels, but what it looses there, it gains with wheels that actually have a significant increase their ability to roll faster than the 26".

You haven't ridden 27.5 much have you. I get it.It sucks that the 26 bike you have is "out of date". It's still a fine machine, and ride it until you feel like getting a new bike, but the advantages are real or the pros wouldn't choose to be riding and winning World Cup DH and EWS events on them. And have you heard of people who own them complain about them? I haven't.
I was steadfast against moving from 26-27.5, but a killer deal dropped into my lap, and I decided for resale value sake I would make the switch. I came from an SB66C so the advantages in ride quality that I'm experiencing are not due to a change to newer geometry. 27.5 climbs better in technical areas, is faster in rough stuff, and obviously rolls better. I have not noticed any draw back cornering. Though it does accelerate slightly slower. The advantages IMO far outweigh the disadvantages.

Pro riders ride what their sponsors want to sell. Some can fight that for a while like Jared graves did last year riding his sb66c even after it was discontinued. He won the enduro World Series with it in a sea of larger wheel size bikes. But at some point you got to move onto the next design your sponsor wants to push.

I have demoed a few 27.5" bikes now. I can't tell any diff in rollover, but I just might not be as sensitive as others riders who can feel a 2% to 4% increase in rollover. A half inch is a pretty negligible difference. I could feel the almost 12% increase in moment of inertia from the 1" larger wheel though, especially when climbing, accelerating and in maneuverability. Also, my 26" FS frame can easily fit a 27.5" wheel with 2.5" tires so I wouldn't call it out of date due to the wheel size that is on it. The 1 1/8" straight steer is what makes that bike out of date. I also have an older rigid that can fit 27.5" as well, but that bike is from 1991, so it is way out of date, but still shreds.

honestly from what I tested I thought there was a huge difference and I thought it was crazy a wheel size could help so much so then I got back on my 26 a day later and turns out I had just learned a smoother line who would think that is possible right. So later I went to my bike to measure the two tires turns out a "650b" is only about 1/8 of an inch bigger making them practically the same wheel size.
flag Robino113
Posted: Aug 27, 2015 at 3:23 Quote
The thing that most people have to remember is that 27.5" isn't actually 27.5". Thats why its called 650B because it uses a different measuring system (not imperial). It's not directly between 26 and 29, its much closer to 26.
flag slope
Posted: Aug 29, 2015 at 13:11 Quote
Damn, just bought a 27.5! Confused
flag SlavIntruder
Posted: Aug 29, 2015 at 14:08 Quote
Canbot wrote:
Singletrackmac wrote:
NMK187 wrote:


You haven't ridden 27.5 much have you. I get it.It sucks that the 26 bike you have is "out of date". It's still a fine machine, and ride it until you feel like getting a new bike, but the advantages are real or the pros wouldn't choose to be riding and winning World Cup DH and EWS events on them. And have you heard of people who own them complain about them? I haven't.
I was steadfast against moving from 26-27.5, but a killer deal dropped into my lap, and I decided for resale value sake I would make the switch. I came from an SB66C so the advantages in ride quality that I'm experiencing are not due to a change to newer geometry. 27.5 climbs better in technical areas, is faster in rough stuff, and obviously rolls better. I have not noticed any draw back cornering. Though it does accelerate slightly slower. The advantages IMO far outweigh the disadvantages.

Pro riders ride what their sponsors want to sell. Some can fight that for a while like Jared graves did last year riding his sb66c even after it was discontinued. He won the enduro World Series with it in a sea of larger wheel size bikes. But at some point you got to move onto the next design your sponsor wants to push.

I have demoed a few 27.5" bikes now. I can't tell any diff in rollover, but I just might not be as sensitive as others riders who can feel a 2% to 4% increase in rollover. A half inch is a pretty negligible difference. I could feel the almost 12% increase in moment of inertia from the 1" larger wheel though, especially when climbing, accelerating and in maneuverability. Also, my 26" FS frame can easily fit a 27.5" wheel with 2.5" tires so I wouldn't call it out of date due to the wheel size that is on it. The 1 1/8" straight steer is what makes that bike out of date. I also have an older rigid that can fit 27.5" as well, but that bike is from 1991, so it is way out of date, but still shreds.

honestly from what I tested I thought there was a huge difference and I thought it was crazy a wheel size could help so much so then I got back on my 26 a day later and turns out I had just learned a smoother line who would think that is possible right. So later I went to my bike to measure the two tires turns out a "650b" is only about 1/8 of an inch bigger making them practically the same wheel size.
Lol, what a hoax this is... let's hope 2016 is the big come back of the 26'' wheel size
flag sacalobra
Posted: Nov 17, 2015 at 5:53 Quote
I bought a 650b frame (commy v4) but ran it with 26 wheels until I could afford an upgrade. Wow I felt underwhelmed. Yes it rolled quicker but something was lost. The zest? The zing? Thankfully with tuning my V4 really rocks/works with 26'ers with Mazzorchi 650b forks. This is why I ride, to feel the ride not deaden the experience or 'roll over things
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