Q128c + 10 speed = 135 mm drop-out width?

[daffy99]

Can somebody please confirm that a Q128c with a mountain bike Shimano SLX 10 speed Hyperglide (HG) cassette will _really_ fit _properly_ into a 135 mm drop-out?

From reading here, I know that a Q128c generally runs with a nine speed cassette.

In my case, I really want to run this with a plain normal ten speed mountain bike cassette, and I really do not want to widen the dropouts, because that's a full suspension bike (with bearings!) made from aluminum (not steel).

I am aware of the document "Q128C-135 Outline.pdf" which is attached to the page at https://bmsbattery.com/ebike-kit/768-q128c-135mm-500w-rear-driving-ebike-hub-motor-ebike-kit.html. This document claims 136mm overall width and a width for the freewheel body of 42.3mm. That looks good, but painful research has shown that paper is very patient, indeed, and that vendors will "tune" the specification to meet demand.

In other words - any real-life experience or (re)assurance before I order the Q128c?

 

[motomech]

I guess you will want to go with a different motor as your combo will require slight spreading of the chainstay.
Although I might point out that spreading an alum. chainstay a mm or 2 is no big deal, I do it by hand. The fact that the donor bike is FS is a non-factor. You will need to install an additional flat washer between the chainstay and the cassette so the sm. gear will not rub on the inside of the drop-out.
Also, since you will only be using 2 or 3 gears w/ the motor installed, there is no benefit to a 10 speed cassette. A 9, or possibly even an 8 gear cassette could be used, whatever will shift w/ your exisiting drive system(ck. Sheldon Brown for parts compatability).

 

[daffy99]

I guess you will want to go with a different motor as your combo will require slight spreading of the chainstay.

Hmm. Not the response I expected

I am under the impression that at least @d8veh and @molybdenum successfully run the Q128c, possibly with Shimano HG cassettes, all of which have the same width. And I have not seen any comments on spacers being required for the Q128c (and Shimano HG). But if there's anything that I have learnt so far in this endeavour: Rather explicitly ask about that _exact_ case, than assuming that it will work out, "somehow".

1 mm of stretch I probably can live with, 3+ mm with an HG cassette sounds a bit too much for my taste. Those 3+ mm I would get on an otherwise splendid-looking cassette motor kit which is available for cheap on ebay (http://www.ebay.co.uk/itm/36V350W-26-Rear-Black-Motor-with-Cassette-Electric-Bike-Conversion-kit-/222613179377). How looking at the _ebay.co.uk_ listing (which I had not studied before), there is a diagram showing 135 mm total width for that motor, and 39 mm for the freewheel body (135-3-8.5-3.5. or so.). In an apples-to-apples comparison, that would probably exactly the same width on the freewheel body for the Q128C.

Also, since you will only be using 2 or 3 gears w/ the motor installed, there is no benefit to a 10 speed cassette. A 9, or possibly even an 8 gear cassette could be used, whatever will shift w/ your exisiting drive system(ck. Sheldon Brown for parts compatability).

Right now I am on a pure Shimano XT 3x10 installation - and I have no clue whatsoever how a Q128c 201rpm 36V will feel at 36V. And how it will work with 48V. Everybody raves about it.

 

[molybdenum]

I put a metal washer between the Q128c and the chainstay, but this was because the motor has a rounded nut in the axle which slightly protrudes beyond the cassette. I was concerned the rounded nut would mash the soft aluminum dropout and the reduced contact area would slip out more easily. I never checked for the gear and chain rubbing the frame, but as you can see from the pic, there seems to be lots of clearance. I can say that even with the ~2mm thick washer, the wheel with 9spd cassette easily slips into the 135mm dropouts without any spreading.

Never having tried a 10spd cassette, I'm speculating that it would protrude slightly past this rounded axle nut and that you would need a small spacer which would need to fit inside the CST cassette without chafing the inside.

 

[daffy99]

I never checked for the gear and chain rubbing the frame, but as you can see from the pic, there seems to be lots of clearance. I can say that even with the ~2mm thick washer, the wheel with 9spd cassette easily slips into the 135mm dropouts without any spreading.

Thank you so much for your response - that photo helps a lot, too!

If you run a Shimano HG cassette, then I am safe, because the HG cassettes should have the same width across 8-9-10 speed versions, as the distance between the cogs shrinks, as cogs are added. That's the little I understand, at least, from reading https://www.sheldonbrown.com/k7.html. (And things are apparently exactly the same for SRAM, too).

 

[molybdenum]

I'm running the Shimano Alivio HG300 9 Speed Cassette. I chose the one with 11-34t as it completely hides the motor

 

[motomech]

Actually, the area where you may have an interference issue is the brk. caliper/motor cover. I ran into that problem w/ my first install years ago. It was a MXUS motor, a motor larger than the Q100 and almost as wide as the Q128. Even though MXUS laced the whl. w/ all spokes as "inners", the spoke heads contacted the motor cover. I was able to provide clearance w/ judicial use of a Dremel tool.
It's hard to predict if there will be an issue because every bike is different, but some Q128 installs have had to go to a bigger 160 mm disc and an adaptor to move the caliper outwards.
Of course, if your donor bike does not use a disc brk., you need not be concerned w/ this.

 

[d8veh]

Firstly, it's no problem to stretch any frame. I've taken a few 135 mm aluminium frames to 150mm without problems. Two of them were FS bikes, which are the easiest.

The Q128 doesn't require any frame stretching, so it's nothing to worry about. A Shimano 10 speed cassette is the same width as a 9 speed so no worry there either.

The 201 rpm 36v Q128c at 48v with a KT controller is nirvana as far as an electric bicycle is concerned. Its light, powerful and silent. I'm running with only 14 amps and find that's enough power for my hilly rides, though I like to pedal with the motor.

 

[daffy99]

Actually, the area where you may have an interference issue is the brk. caliper/motor cover.
... some Q128 installs have had to go to a bigger 160 mm disc and an adaptor to move the caliper outwards.

I am on 160mm discs already (even in the back), and also on "semi-expensive" XT-level brake calipers, so there's hope. 180mm would be an option (using a 160 to 180 post mount adapter). I am also mentally prepared for additive tweaking (a shim or washer here or there), but subtractive I'd really prefer to avoid.

Keeping fingers crossed here

PS: Who says that the first few runs need two working brakes?

 

[daffy99]

Firstly, it's no problem to stretch any frame. I've taken a few 135 mm aluminium frames to 150mm without problems. Two of them were FS bikes, which are the easiest.

Thank you very much for the comforting response!

I am a bit concerned about the FS ball bearings and axles(?) at the far rear end dying "earlier", if I were to stretch the frame. The current set is already aching and groaning, the replacement parts have arrived, but I am deliberately postponing servicing until I have sorted out the electrification situation. Until then - grease, grease, oil, oil, sing merry songs to placate the bearings.

(I do not intend to ride the FS MTB on trails with the motor in place. It's supposed to temporarily mutate into a winter city road, sidewalk, and stairs racer. Electrification is primarily meant to handle the sweating problem. Unless motor power really gets me into fancier ideas. This is my First Time.)