B9er thread

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flag tene
Posted: Jun 29, 2018 at 0:38 Quote
ollia wrote:
As you guys have ecperience riding a b9er, what do you think about 26x3,0 rear and 29x2,35 front? Would it be too much difference in overall wheel diameter? Isn't it around the same difference as 27,5x2,35 vs 29x2,35?

I'm just thinking about this for a hardtail, so I could have a tiny bit more cushion in the back but still the sharp steering and rollover of the 29 in front. It would be quite cheap to try though, as 26" back wheels go cheap used. I have to look at the tyre options as well as I really want good damping and grip.

Sorry, a bit ot but there's not too many of these threads around.

26x3.0" compress more than 27.5x2.35" when riding so it might slacken the angles too much. Otherwise I dont't see any problems for that setup.
flag ollia
Posted: Jun 29, 2018 at 4:13 Quote
Well, I'm the kind of guy who thinks 62 is not too slack for head angle, but my seat angle could go too low actually, good point. My bike is now around 63,5 ha with 150mm fork and 29 wheels front and rear. ???? I might go less travel in the fork also to compensate, but let's see.

I've been thinking about a full custom (hardtail) frame too from Marino in some point, with more extreme geometry. Thinking 62-63ha, 76-77sa, 450-475 reach, -60mm bb, 430-435mm cs with a 130mm fork.

I love riding a hardtail, but want it to be capable to ride everything, dh too as that's my background.
flag Xorrox
O+
Posted: Jun 29, 2018 at 8:50 Quote
Yep I'm a big fan of 29" in the front and 27.5" in the back. I call them mullet bikes; all business in the front, all party in
the backSmile

On both bikes I've done this on, I've started with a 27.5" bike first but it sounds as if some of you are going the other way (starting with a 29" bike and putting on a 27.5" wheel).

On my most recent bike I tried going back to a 27.5" wheeled bike front and rear bike and even over forked it by 10mm but it still seemed super sketchy on steep and rough downhill compared to my previous mullet bike so I ended up putting my 29 fork and wheel back on. (Anyone want a brand new 27.5" 2019 170mm Lyrik? - it's in the buy and sell!)

Here are the pro's and con's I've found going from a full 27.5 bike to a 'mixer':

Pros:
- Much better resistance to going over the bars in steep downhill terrain. This in turn is a huge confidence booster and allows me to take a more centered 'attack' position on the bike in these conditions instead of hanging off the back.
- Better front wheel 'rollover' ability (common to all 29" wheeled bikes), both climbing and descending. Also more high speed stability in the front over rough stuff, a trait all 29ers tend to share due to the gyroscopic effect of the larger wheels.
- More front end 'pop' when hitting obstacles and sharp lips. The front wheel tends to deflect upwards more rather than getting hung up or plowing straight through. This can be good (makes launching off roots and rocks easier) or it can be bad (you can't steer when your front wheel is in the air). However, this encourages you to weight the front wheel more than before, actually improving grip and cornering.
- Related to the point above, jumping just feels more natural and controlled to me. The greater front wheel 'pop' encourages launching off practically everything while the landings feel more controlled as the larger front wheel gives a greater margin for error when landing front heavy.
- A higher front end (assuming you don't reduce the amount of front fork travel that much) means a higher BB which means fewer pedal strikes. (But this is also a negative).
-Since you have a 27.5" wheel in the back, you have less chance of "bum buzz" when hanging way off the back.

Cons:
- Unless you reduce your fork travel by around 30 mm when you switch to a 29er front fork and wheel, the whole front end of the bike will be significantly higher. The higher stack height was fine for me as I was already using a bunch of spacers under my stem and a riser bar so I just got rid of those for a similar bar height.
- The higher front end also means your stand over height will increase which may be annoying if the bike already has a fairly high stand over height.
- This will also raise your bottom bracket by around 15 to 20 mm (which is also common in long travel full 29er bikes) which might be less than ideal because of the higher center of gravity. I never noticed this as an issue and, in fact liked the fewer pedal strikes as a result.
- It will also slacken the head angle by around 1.5 degrees which to me is a net benefit but does lead to a longer wheelbase and more wheel flop on tight uphill corners. A reduced offset fork may help with this a little or you can install a negative angle set if you don't like this.
- Finally and most importantly, it will also slacken your effective seat angle by around 1.5 degrees. You can somewhat compensate for this by slamming your seat all the way forward on the rails but to me this is the biggest downside on most bikes. For this reason, the bikes that are most ideal for this swap are ones with the steepest initial seat angle. As a result, I do find myself riding the nose of my seat on steep climbs more than I would like to.
- The larger front wheel and slacker head angle means you need to take the wide, outside line going into tight slow corners. This is typical of all slack 29ers though I believe. The one thing that may not be similar to a full 29er (I'm not sure on this) is that the 27.5" rear tire takes a significantly different line through the corner than the front. This makes riding North Shore 'skinnies' a lot more challenging than a full 27.5" wheeled bike as there often is not enough room to keep both wheels on the skinny when there is a turn unless you 'hop' the back wheel ( which I suck at).
- Another 'con' that will discourage many people from trying this is that it will almost certainly void your frame warranty. Over-forking and over-wheeling the front of 27.5" bike by this much puts a lot more stress on the head tube area of the frame so you wouldn't want to try this on a bike that is known to be weak in this area.
flag wowbagger
Posted: Jun 29, 2018 at 11:07 Quote
Xorrox wrote:
Yep I'm a big fan of 29" in the front and 27.5" in the back. I call them mullet bikes; all business in the front, all party in
the backSmile

On both bikes I've done this on, I've started with a 27.5" bike first but it sounds as if some of you are going the other way (starting with a 29" bike and putting on a 27.5" wheel).

On my most recent bike I tried going back to a 27.5" wheeled bike front and rear bike and even over forked it by 10mm but it still seemed super sketchy on steep and rough downhill compared to my previous mullet bike so I ended up putting my 29 fork and wheel back on. (Anyone want a brand new 27.5" 2019 170mm Lyrik? - it's in the buy and sell!)

Here are the pro's and con's I've found going from a full 27.5 bike to a 'mixer':

Pros:
- Much better resistance to going over the bars in steep downhill terrain. This in turn is a huge confidence booster and allows me to take a more centered 'attack' position on the bike in these conditions instead of hanging off the back.
- Better front wheel 'rollover' ability (common to all 29" wheeled bikes), both climbing and descending. Also more high speed stability in the front over rough stuff, a trait all 29ers tend to share due to the gyroscopic effect of the larger wheels.
- More front end 'pop' when hitting obstacles and sharp lips. The front wheel tends to deflect upwards more rather than getting hung up or plowing straight through. This can be good (makes launching off roots and rocks easier) or it can be bad (you can't steer when your front wheel is in the air). However, this encourages you to weight the front wheel more than before, actually improving grip and cornering.
- Related to the point above, jumping just feels more natural and controlled to me. The greater front wheel 'pop' encourages launching off practically everything while the landings feel more controlled as the larger front wheel gives a greater margin for error when landing front heavy.
- A higher front end (assuming you don't reduce the amount of front fork travel that much) means a higher BB which means fewer pedal strikes. (But this is also a negative).
-Since you have a 27.5" wheel in the back, you have less chance of "bum buzz" when hanging way off the back.

Cons:
- Unless you reduce your fork travel by around 30 mm when you switch to a 29er front fork and wheel, the whole front end of the bike will be significantly higher. The higher stack height was fine for me as I was already using a bunch of spacers under my stem and a riser bar so I just got rid of those for a similar bar height.
- The higher front end also means your stand over height will increase which may be annoying if the bike already has a fairly high stand over height.
- This will also raise your bottom bracket by around 15 to 20 mm (which is also common in long travel full 29er bikes) which might be less than ideal because of the higher center of gravity. I never noticed this as an issue and, in fact liked the fewer pedal strikes as a result.
- It will also slacken the head angle by around 1.5 degrees which to me is a net benefit but does lead to a longer wheelbase and more wheel flop on tight uphill corners. A reduced offset fork may help with this a little or you can install a negative angle set if you don't like this.
- Finally and most importantly, it will also slacken your effective seat angle by around 1.5 degrees. You can somewhat compensate for this by slamming your seat all the way forward on the rails but to me this is the biggest downside on most bikes. For this reason, the bikes that are most ideal for this swap are ones with the steepest initial seat angle. As a result, I do find myself riding the nose of my seat on steep climbs more than I would like to.
- The larger front wheel and slacker head angle means you need to take the wide, outside line going into tight slow corners. This is typical of all slack 29ers though I believe. The one thing that may not be similar to a full 29er (I'm not sure on this) is that the 27.5" rear tire takes a significantly different line through the corner than the front. This makes riding North Shore 'skinnies' a lot more challenging than a full 27.5" wheeled bike as there often is not enough room to keep both wheels on the skinny when there is a turn unless you 'hop' the back wheel ( which I suck at).
- Another 'con' that will discourage many people from trying this is that it will almost certainly void your frame warranty. Over-forking and over-wheeling the front of 27.5" bike by this much puts a lot more stress on the head tube area of the frame so you wouldn't want to try this on a bike that is known to be weak in this area.

Very thorough, impressive!
flag tene
Posted: Jun 29, 2018 at 12:15 Quote
Xorrox wrote:
Yep I'm a big fan of 29" in the front and 27.5" in the back. I call them mullet bikes; all business in the front, all party in
the backSmile

On both bikes I've done this on, I've started with a 27.5" bike first but it sounds as if some of you are going the other way (starting with a 29" bike and putting on a 27.5" wheel).

On my most recent bike I tried going back to a 27.5" wheeled bike front and rear bike and even over forked it by 10mm but it still seemed super sketchy on steep and rough downhill compared to my previous mullet bike so I ended up putting my 29 fork and wheel back on. (Anyone want a brand new 27.5" 2019 170mm Lyrik? - it's in the buy and sell!)

Here are the pro's and con's I've found going from a full 27.5 bike to a 'mixer':

Pros:
- Much better resistance to going over the bars in steep downhill terrain. This in turn is a huge confidence booster and allows me to take a more centered 'attack' position on the bike in these conditions instead of hanging off the back.
- Better front wheel 'rollover' ability (common to all 29" wheeled bikes), both climbing and descending. Also more high speed stability in the front over rough stuff, a trait all 29ers tend to share due to the gyroscopic effect of the larger wheels.
- More front end 'pop' when hitting obstacles and sharp lips. The front wheel tends to deflect upwards more rather than getting hung up or plowing straight through. This can be good (makes launching off roots and rocks easier) or it can be bad (you can't steer when your front wheel is in the air). However, this encourages you to weight the front wheel more than before, actually improving grip and cornering.
- Related to the point above, jumping just feels more natural and controlled to me. The greater front wheel 'pop' encourages launching off practically everything while the landings feel more controlled as the larger front wheel gives a greater margin for error when landing front heavy.
- A higher front end (assuming you don't reduce the amount of front fork travel that much) means a higher BB which means fewer pedal strikes. (But this is also a negative).
-Since you have a 27.5" wheel in the back, you have less chance of "bum buzz" when hanging way off the back.

Cons:
- Unless you reduce your fork travel by around 30 mm when you switch to a 29er front fork and wheel, the whole front end of the bike will be significantly higher. The higher stack height was fine for me as I was already using a bunch of spacers under my stem and a riser bar so I just got rid of those for a similar bar height.
- The higher front end also means your stand over height will increase which may be annoying if the bike already has a fairly high stand over height.
- This will also raise your bottom bracket by around 15 to 20 mm (which is also common in long travel full 29er bikes) which might be less than ideal because of the higher center of gravity. I never noticed this as an issue and, in fact liked the fewer pedal strikes as a result.
- It will also slacken the head angle by around 1.5 degrees which to me is a net benefit but does lead to a longer wheelbase and more wheel flop on tight uphill corners. A reduced offset fork may help with this a little or you can install a negative angle set if you don't like this.
- Finally and most importantly, it will also slacken your effective seat angle by around 1.5 degrees. You can somewhat compensate for this by slamming your seat all the way forward on the rails but to me this is the biggest downside on most bikes. For this reason, the bikes that are most ideal for this swap are ones with the steepest initial seat angle. As a result, I do find myself riding the nose of my seat on steep climbs more than I would like to.
- The larger front wheel and slacker head angle means you need to take the wide, outside line going into tight slow corners. This is typical of all slack 29ers though I believe. The one thing that may not be similar to a full 29er (I'm not sure on this) is that the 27.5" rear tire takes a significantly different line through the corner than the front. This makes riding North Shore 'skinnies' a lot more challenging than a full 27.5" wheeled bike as there often is not enough room to keep both wheels on the skinny when there is a turn unless you 'hop' the back wheel ( which I suck at).
- Another 'con' that will discourage many people from trying this is that it will almost certainly void your frame warranty. Over-forking and over-wheeling the front of 27.5" bike by this much puts a lot more stress on the head tube area of the frame so you wouldn't want to try this on a bike that is known to be weak in this area.

Very good points from 27.5"-> b9er point of view.
flag ollia
Posted: Jun 29, 2018 at 14:34 Quote
Thanks guys for the opinions. Let's keep the discussion going, 'cause this is a really interesting subject.
flag ktm87
O+
Posted: Jun 29, 2018 at 15:29 Quote
As far as my next build goes I’m still unsure what frame I’m gonna go with. Really trying to decide if i wanna do more a of a trail bike or go a little beefier and have it be a do all that i take with me to the park. I’m leaning towards the latter. My lbs is a Santa Cruz dealer and told me they would get me a good deal on a nomad 4 frame and I’m thinking paired with the new Ohlins dh race fork in 160mm 29” would be pretty killer
flag tene
Posted: Jun 30, 2018 at 0:47 Quote
Heist30 wrote:
Does B+9r count?

2018 YT Jeffsy AL 29 27 Hybrid

Welcome to the thread!
Does the big back tyre cause any clearance issues?
flag undescended
Posted: Jun 30, 2018 at 10:07 Quote
tene wrote:
Heist30 wrote:
Does B+9r count?


Welcome to the thread!
Does the big back tyre cause any clearance issues?
Nope, no issues...tire is a 2.8, bike is a 9r and the rear measures about 3.2” wide at that point. I also run her full B+ with a 3.0 up front and she’s a blast.
flag ktm87
O+
Posted: Aug 7, 2018 at 3:17 Quote
picked up a zerode. Swapped the Diamond boost 27.5 lowers to 29 lowers. need to machine boost adapters and need to lower fork fown to 140mm from 160mm to compensate for higher front end.

29 lowers on. Need to get boost adapters and lower fork from 160 to 140
flag tene
Posted: Aug 7, 2018 at 6:20 Quote
ktm87 wrote:
picked up a zerode. Swapped the Diamond boost 27.5 lowers to 29 lowers. need to machine boost adapters and need to lower fork fown to 140mm from 160mm to compensate for higher front end.

29 lowers on. Need to get boost adapters and lower fork from 160 to 140

Nice!
How does the angles change after fork swap?
flag ktm87
O+
Posted: Aug 7, 2018 at 6:44 Quote
tene wrote:
Nice!
How does the angles change after fork swap?

havent measured but im guessing its 2 degrees slacker, once i lower fork it should be back to normal. another option is to add a angle set which would lower the front end back to normal stack height without having to reduce travel of the fork
flag ktm87
O+
Posted: Aug 8, 2018 at 2:48 Quote
fork is still at 170mm in the pics but its been lowered to 150 now

Fork still needs to be reduced. Contemplating an angle set to reduce stack height
Fork still needs to be reduced. Contemplating an angle set to reduce stack height
Fork still needs to be reduced. Contemplating an angle set to reduce stack height
flag tene
Posted: Oct 2, 2018 at 8:27 Quote
https://m.pinkbike.com/news/2019-uci-mtb-rule-book-dh-world-cup-start-order-wheel-size-emtb-alpine-snow-bike-pump-track.html

"In DH and enduro events, riders are allowed to run two different wheel sizes on the same bike."

There will be lots of discussion, new bikes and speculation about the b9ers in the near future.

 


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