Is BB height and motor placement just as important to consider on emtb's?

[Neeko DeVinchi]

This may sound weird and daft but humour me.
I've begun a side project by using my Lyrik 180mm travel forks from my Kenevo on my 2017 Enduro Comp 29. Thankfully, I'm able to squeeze my 29x2.35 Magic Mary into the fork but as I suspected, the BB height has increased (along with slackened head angle, slackened seat tube angle etc). Truth be told, the bike has never felt better as I could still find myself climbing up fire roads and jibbing the bike just like it was using the Yari 29/27.5. It is worth mentioning that I'm 6foot 3.5inches with a 35inch leg.
Anyway, after cleaning the bike, and putting it away, I couldn't help but look at my fleet and ask myself "have I gone too extreme with some of my mods and what are the consequences".
Traditionally, a high bb height would make a bike less agile in the turns and harder/sluggish to manoeuvre. However, emtb's weight and custom suspension (in some examples) counters this.

I'm aware that some manufacturers have begun placing motors in different positions to run with the downtube or to sit underneath.
Being as I'm only familiar with the Specialized emtb's and my Bafang builds, can anyone enlighten me as to whether bb height (along with motor placement) has a real world effect in terms of trail/Enduro/Allmountain/Downhill.

Apologies if this sounds like a daft thread to begin but I am really interested to know (especially from tall riders as well)

P.S. I have no regrets in slapping a 200mm travel fork on my Kenevo or the 180mm travel fork on my Enduro ?

 

[Gary]

a high bb height would make a bike less agile in the turns and harder/sluggish to manoeuvre

This isn't true.
A higher BB actually makes it easier to raise the front wheel
Lower increases stability

Short answer = Yes. Motor, battery and BB placement affect handling

I hate high BBs on mtb but it's entirely a personal preference

 

[Neeko DeVinchi]

This isn't true.
A higher BB actually makes it easier to raise the front wheel
Lower increases stability

Short answer = Yes. Motor, battery and BB placement affect handling

I hate high BBs on mtb but it's entirely a personal preference

Gottya Gary. If I could get to a bike park, I'd gladly do back to back runs between my kenevo and enduro. Oh well, I guess we're all feeling this national lockdown.

 

[Jpzeroday]

Biggest issue I have had is break over angle with a low BB and skid plates. Sold a Decoy due to this. If you like to ride technical terrain, breakover clearance matters. I think the Levo/Kenevo have it nailed. My new Bullit also is good.

 

[El Topo]

I hope the grave dig is excused, but this topic fits my question perfectly:

I am looking at a 150mm travel full suspension frame (Dengfu E10), that was designed around (max.) 29x2.6" or 27.5x2.8 tire frame, with a BB drop of 20mm, cranks will be 152mm.
Due to different alterations, among those fat tires of around 785mm diameter, I estimate the BB height to be around 365mm, or around 15mm higher, than with the tires the frame was designed for. Two offset bushings, and a -1 angle set, are already accounted for.

Based on what I was able to find, those 365mm seem quite high for a trail bike, or doesn't it?

I could choose a very similar frame (E23/56), where should be able lower the BB (or rather motor axle), by how much I want to (with a custom motor bracket), that is why I am even asking.

Would I notice let's say 20mm more BB drop, as a casual rider? Just going by pedal strike clearance and other 29er bikes, I could probably even drop the BB by over 30mm, if running those 152mm cranks.

 

[steve_sordy]

I agree that a 365mm BB height is a bit high.

In 2011-13, I had a Kona Dawg mtb that had a BB height of 356mm which is not that far from your plan. It had 175mm cranks I can't recall any pedal strikes at all. The front travel was 150mm like yours, but with 140mm rear. I loved that bike. But the bike that came after it I loved even more. It was a 140mm travel F&R Norco Sight mtb. The BB height was 340 mm. It also had 175mm cranks. I still can't remember any pedal strikes. I'm not saying there weren't any, just that there weren't enough for me to remember it as a problem. What I do remember is that despite the BB only being 16mm lower, the bike felt a lot more stable and confidence inspiring. But that may have been more due to the 1.3 degrees slacker head angle.

If you can choose a frame that is more like the well tried and tested normal BB height, then why take the risk of going high? You have the short cranks in your favour.

Don't forget that when you are sat on the bike, it will drop by 30% x 150mm = 45mm. Dynamic riding will drop it all the way.

 

[El Topo]

I agree that a 365mm BB height is a bit high.
....
If you can choose a frame that is more like the well tried and tested normal BB height, then why take the risk of going high? You have the short cranks in your favour.

Don't forget that when you are sat on the bike, it will drop by 30% x 150mm = 45mm. Dynamic riding will drop it all the way.

Thanks for the reply, I assumed to get a reply like that. Some 29ers go as low 330-340mm, so I assume I could go quite a bit lower than those 365mm, especially with the shorter cranks.
Yes, I know the bike will sag under load, but AFAIK, all the BB measurements are made with an unloaded bike, to keep them comparable.

I would prefer the off-the-shelf-frame, but if that lower BB makes such a difference in ride feel, I will try to make the other frame work.