Fatbike BB torque sensors and weird sizing.

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SayWatt   1 µW

1 µW
Posts: 2
Joined: Nov 16 2018 6:20am

Fatbike BB torque sensors and weird sizing.

Post by SayWatt » Nov 16 2018 6:43am

Hello all,
I'm new here and brand new to ebiking. I've only been reading up on the subject for the last couple of months waiting for my motorbike to sell so I can build an ebike. Every build I plan out ends up getting stuck somewhere usually due to the donor bike's weird sizing. I'm looking at bikes from BD and some cheap mongoose bikes as donors. I have searched the forum here but I can't find anything relevant.

My first choice was the 2019 Gravity Bullseye Monster and I am trying to find out if the Sempu 175 bb torque sensor would fit. The bike's bb is 100mm/144mm. The torque sensor is 100mm/175mm. I emailed their customer support and asked if it would fit and they said no, so I started looking for other donor bikes just to realize I can't find a single bike with the 100mm/175mm sizing. I emailed the customer support asking them the size of the part without the end of the spindles, the sensor housing itself that would have to fit in the BB. The reply was the data/spec sheet that still doesn't answer my question, and no reply since. The mongoose are even worse with a 110-112mm BB according to various forums. Can't find a spec sheet for any of the cheap models. Also asked the customer support for an example of a bike that fits the Sempu 175 and got ignored for a few days now. This will be for a fatbike hub motor with a big batt and PAS only for flat road riding and I want a quality torque sensor.

Bonus question, will a 175mm hub drop into a 170mm dropout without modification?

SayWatt   1 µW

1 µW
Posts: 2
Joined: Nov 16 2018 6:20am

Re: Fatbike BB torque sensors and weird sizing.

Post by SayWatt » Nov 18 2018 8:09am

I solved my build issues.
This post can be ignored/deleted.
Thanks.

Canoe   1 mW

1 mW
Posts: 19
Joined: Aug 13 2010 12:01am

Q

Post by Canoe » Feb 08 2019 1:12am

When first out (March 2014), the Mongoose Dolomite came with a 100 mm BB and a spindle of 189 mm. Some quality YST bearings were nice, but the spindle was soft, and long, and a number of reports of getting bent.
But no cartridge BB would fit (with the stock straight crank arms). Then someone figured out there was one or two that would, if you got curved crank arms to get the width/tread/q-factor to get out far enough for your heals to clear the chain stays.

Then in early 2019, someone posted that the Domomite that they acquired had a 110 mm shell. So make sure you measure before you order.

So if you want to use fat bikes, with curved crank arms, you may be in luck. The specific cartridges & crank arms that fit are in posts near the current end of this thread https://forums.mtbr.com/fat-bikes/dolo- ... 02410.html
Note there are different spreads of chain stays on the various Mongoose, even at least two chain stay clearance widths on the early vs. later Dolomite. So make sure you measure your bike, and you can always ask there what thread/clearance someone got going with their cartridge/curved-arms.

But I'd be curious to know how you solved the BB issue for your build, as I'd like to take my Dolo from thumb throttle to torque.

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