Does anyone think their e-bike is undergeared? Here’s how I fixed my Raleigh Motus Hub-gear.

hankhill

Finding my (electric) wheels
Jul 15, 2016
12
6
108
London
I recently bought a Raleigh Motus, the GT model with Bosch Active Line Plus motor. It’s my third e-bike after having had a nice Greenedge for 4 years (which will be on eBay soon). I’m only a very occasional leisure cyclist, and the Motus is more comfortable for me than the Greenedge due to its larger wheels and frame and raised handlebars (I’m 6’2” and around 16.5 stone). The Motus seems to be good quality, although I was a bit shocked at how thin the wheels were compared to my Greenedge, which is more “Mountain-Bikey”. I’m not planning to go seriously off road but I often cruise along bumpy gravel tow paths, so I’ll have to see how the bike pans out for that. Anyway, I thought I’d share a modification that I just made to the Motus, that might be of interest to others.

This Motus is a 2019 model, I bought it about 6 weeks ago as new with 2 miles (really!) on the clock, but since it was bought on eBay there’s probably no Raleigh warranty, so I felt free to tinker. It has hub gears; that wasn’t why I bought it, and the jury’s still out whether I prefer hub over derailleur gears. However one thing I did notice straight away was that the bike was under geared. The Shimano Nexus has 8 speeds, and even in 8th I felt I was pedalling way too quickly for the speed I was doing. Sometimes I even pulled away in 8th and then went to change up, only to find I’d already run out of gears! I never used anything lower than 4th, even for steep hills. The Nexus hub gear isn’t made specifically for ebikes, and I assume that Raleigh wouldn’t have changed the stock gearing when integrating it into the Motus, so the under gearing problem seems to be because Raleigh (and others) are building ebikes with non-ebike gear ratios. Thanks Raleigh…

Searching various forums, undergeared ebikes seem to be a fairly common complaint, and so I started looking into fixing this. I’m not a bike techy, although I am practically minded, so I first looked at a bigger chainring as I’d assumed that the gearing at the back couldn’t be changed. On a forum someone pointed out that the single rear sprocket on a hub-gear can in fact be swapped, and is probably easier and cheaper than swapping the chainring, as things like the chainguard won’t need to be modified or lost, and I wouldn’t have to buy a new longer chain. My bike had a 22 tooth rear sprocket and so I took a chance and bought an 18T. I also bought a chain tensioner, for two reasons. I had read that any mid motor ebike will stretch the chain more than normal, and whilst derailleurs will automatically take up the slack, hub gear bikes won’t. People with these bikes were complaining about having to adjust the rear wheel to take up chain slack, every few hundred miles. And then as someone pointed out to me in these forums, when you move the wheel you have to reposition the hydraulic brake caliper too, and maybe the speed sensor magnet as well, so it’s a real PITA overall. On the latest 2020 model Motus, Raleigh does fit a chain tensioner to alleviate this problem, so they clearly admit its an oversight. Unfortunately, they also changed the frame design so the “official” chain tensioner can’t be retrofitted to older bikes. Thanks Raleigh…

I first tried the official Shimano chain tensioner that is designed to work with the Nexus hub gear. Unfortunately, Raleigh’s installation would seem to be somewhat non-standard with semi-vertical dropouts, which means that the Shimano tensioner can’t be used, as the non-turn washer is built into the tensioner and is set for a (presumably more common) vertical dropout. Thanks again Raleigh…

I found a decent looking no-name tensioner online and fitted it without much problem into an unused mounting in the chainstay, using a derailleur gear hanger, a tip I found on these forums (thanks Saudidave). You can see this in the attached photos.

The other reason I wanted to fit a tensioner was that I didn’t want to shorten the chain until I was sure that I’d done the right thing. The new sprocket is 4 teeth smaller, so that’s one whole chain link (I think). Whilst the current arrangement seems to work fine, I would prefer to shorten the chain once I have tested it fully over a couple of my bumpy canal path trips, as I think it will reduce the risk of the chain falling off in the future.

So, has the new sprocket worked? With the 22T sprocket I measured a cadence of about 68rpm at 15mph in 8th. Yes, I know that the “lycra brigade” will say a fast cadence is better, etc. but I’m a 60 year old tourer not a 20-something skinny racer. The new 18T sprocket gives me a cadence of about 54rpm at the same 15mph in 8th, about a 20% reduction, so I’m happy that this has been a worthwhile exercise. Maybe I’d have been even happier with a 16T sprocket but…

Incidentally, in case anyone is still reading and wondering if I have derestricted the bike, no I haven’t. Actually that’s not strictly true, I did do the quick bodge of moving the sensor and putting a magnet on the pedal, just to see what its like. It works - using my phone as a speedo the motor assistance does continue past 15.5mph, and I can easily cycle past 20 mph under motor assistance, helped of course by the higher gearing. However, it doesn’t make the bike feel that much faster overall; the Bosch motor has very low drag so pedalling unassisted isn’t as bad as say my wife’s BH evo, where you really feel it when the motor stops helping. So, I doubt that I will be investing £150 in a dongle, as aside from the legalities, the extra speed will only make it hurt more if I fall off.

I hope this rather long ramble is of interest, comments of course welcome.
 

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Swizz

Pedelecer
Oct 1, 2017
211
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Sk14
My bike had a 22 tooth rear sprocket and so I took a chance and bought an 18T.
That's unusual in being geared on the low side! We have had three hub geared bicycles over the years and all three were geared too high for where we live (hilly)

Like you we replaced the sprockets. There is a handy calculator on Sheldon Browns website. We sized ours to drop the gearing one whole ratio. It made the bikes more usable as they had less gear range than yours - one 3 speed & two 5 speeds.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
9,822
3,986
Basildon
That tensioner is a really good idea. It'll save loads of hassle.

Another thing about how it was before is that after lots of chain adjustments the wheel nuts don't clamp so well, and if you use the highest torque from the motor, they can slip, which is a right pain. For a crank-motor, where there's a high forward force on the chain, the axle should be fitted with restraints/adjusters, like on a motorbike. As long as you keep the nuts tight and don't have to move anything too often, you should be OK.
 
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