Motor for 130 mm rear drop outs

I have a much loved titanium bike I use for day rides. I want to convert it to be an electric gravel bike ( it has big tyre clearance ). Like all road frames up until recently it has 130 mm rear drop outs. As I would prefer to use a rear hub motor this is a problem - they don't seem to exist ! I have done a limited amount of research and it seems that respacing a titanium frame is likely to be very difficult and I cannot find any reference to anyone who claims to have done it. So this is an appeal to the experts on this forum - is the 'magic motor' out there, or could one be tailored by deleting some spacers? I would want to retain an 8 speed cassette.

Will your frame stretch to 135mm?

Typically all rear hubs are minimum of 135mm.

Cassette motors are mainly wider than 135mm, but freewheel motors are rarely wider as long as you fit a 7-speed frewheel (or less). The 5mm between 130mm and 135mm is not noticeable when it comes to installing the motor. You won't have any problem installing or running with a 135mm wide motor.

 

My recommendation would be that you fit a 7 speed freewheel motor and change your shifter and derailleur to 7 speed. That adds about £25 to the cost of conversion if you buy new parts or about £10 for used ones.

 

The difference between 8-speed and 7-speed is insignificant when you have a motor.

 

You don't mention cost, but there are some more expensive cassette motors that would probably fit OK. Also, you don't give any idea about usage or performance characteristics required, so it's impossible to give you an exact recommendation.

Thanks for replies so far. I am going to simulate a 135 hub tomorrow and see how I get on. I am a bit sceptical it will be as easy as suggested because I had a similar issue last year fitting an XF08C ( 40mm nominal oln ) into a Cannondale that measured 137mm. I took out a washer to save 1mm and it just about worked but is a real pita to get in and out. The titanium chain stays seem pretty chunky so I am not optimistic but nothing ventured...as they say. I will report back.

You may be better off going with a crank drive bottom bracket motor like the TSDZ2. It's not heavy.

Well, today must be my lucky day ( makes up for this week's puncture ). I got an old MTB wheel, checked it was 135 and it was an easy fit with minimal stretch on the chain stays. My drop outs actually measure 131 but I was atonished how easy it was to fit compared with the battle I had ( and have) with my alu Cannondale. So the hunt is on - a 135 hub motor with 9 speed cassette. All suggestions welcome.

Thank you Woosh for your suggestion. A TSDZ2 from you was actually where I started from ( and I sent you a customer enquirey on this related to the bag battery option just before Xmas). However I have been so pleased with my XF08C that I thought that if a similar option existed in an appropriate size I would prefer to replicate this on my road/gravel bike. Just for fun (?) I might try and get my XF08C wheel in but I am pretty sure that is a stretch too far and could bring other alignment issues that I do not want.

We have the new DWG2NC which is a rear motor with 135mm dropout but in 20in rim only at the moment. I will stock more sizes in late spring.

May be difficult to get a 9 speed cassette to fit.

May be difficult to get a 9 speed cassette to fit.

What do you mean? Both the XF08C and DWG2NC take standard 8,9,10 cassettes. 7 speed cassette needs a 2mm spacer.

Thanks Woosh, sounds like DWG2NC is just what I am looking for. I am not in a rush so I will contact you in a couple of months.( My wheel size is 700C )

What do you mean? Both the XF08C and DWG2NC take standard 8,9,10 cassettes. 7 speed cassette needs a 2mm spacer.

 

Why would you want a 10 speed cassette on a lightweight e-bike. You will never need to use all of those ratios.

Why would you want a 10 speed cassette on a lightweight e-bike. You will never need to use all of those ratios.

 

Conversion kits need to be compatible with a large range of cassettes.

for ready made bikes, I usually put 8 speed 11T-32T on my bikes with hub motors, 9-speed with crank motors. Bikes with 7-speed tend to have screw on freewheels. If you look closely, you can see that the rear sprockets on the freewheel wobble. This is sub optimal for the chain. Also, freewheels usually start with 13 teeth instead of 11 teeth for cassettes. Older cyclists would appreciate 11 teeth which lets them lower their cadence.

Interesting that you put 9 speed cassette on your crank motors. I run a BBSHD and only use 3rd, 5th and 7th gear. The 11 tooth 8th gear tends to bog it down.

9-speed is more useful on a bike with torque sensor and crank motors.

Well, I am definitely an older cyclist. Self powered Alpine ascents are but fading memories but I have recently rediscovered the pleasures of hilly terrain thanks to my Cannondale conversion. I really only use e power as hill assist, the rest of the time I ride 'powerless' and at relatively high cadence. I need all my gears , currently 3 x 9 on my road bike. I will probaley ditch the triple chainset when I get my road bike conversion but I will certainly keep 9 on the back! We all have different requirements.

I need all my gears , currently 3 x 9 on my road bike. I will probaley ditch the triple chainset when I get my road bike conversion but I will certainly keep 9 on the back! We all have different requirements.

 

My old boss from the 1940's would turn in his grave. I still remember when the first 5 speed rear only derailleur appeared in the shop.

 

"Ridiculous" he said, "who could ever want more than three gears?

.

I remember well my first move from Sturmey Archer 3 speed to 5 speed, my father too questioned the need having been a fixed wheel commuter in his earlier years. 14 miles each way for an 8 hour day labouring in a brick yard and probably all on a cheese sandwich. The days of you did what you had to do and kept quiet about it.

Personally I run 3x8 on my bike and, living in hilly West Wales, I need 'em all. Especially with panniers full of shopping.

I remember well my first move from Sturmey Archer 3 speed to 5 speed, my father too questioned the need having been a fixed wheel commuter in his earlier years. 14 miles each way for an 8 hour day labouring in a brick yard and probably all on a cheese sandwich. The days of you did what you had to do and kept quiet about it.

 

True, but utility cycling in the 1940s and before was very different. Almost none of today's head down over drop handlebars inputting lots of effort at 20mph or more, plus cycling up steep hills.

 

Then it was upright, almost universally at around 10 mph and getting off and walking up hills of any steepness. Even we youngsters often walked up hills pushing our bikes.

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Edited January 7, 20242 yr by flecc

It may depend on how much motor power one uses? I nearly only ever use 3 out of my 8 gears because I hardly expend any effort, over mixed terrain, but I can well imagine people capable or desirous of getting exercise being more frugal in their use of motor assistance needing smaller changes of gear ratio and more of them.

Edited January 7, 20242 yr by guerney

My MTB has 8 gears and I use 3 of them, my Greaser has 7 gears and I use 1 of them and my Puch Maxi is going to lose the chain drive altogether.

It's nice that options for everyone's needs are available at reasonable cost these days!

It'd be great if mid-drives could use motorbike chains. On my bike at least, weight doesn't matter. Cassettes and chains for my bike are pretty cheap, so there's no reason for me to try any of the following - bear in mind I don't know motorbike chain dimensions: I'm wondering if removing 4 of 8 gear cogs from my cassette, doubling up the four which remain, then doubling the 52T chainwheel (bolting or riveting two chainwheels together for double width, or getting a custom thicker chainwheel and rear cassettes made [or file away metal from the rear cog sprockets?]), allowing me to use a motorcycle or some other wide chunky chain which fits... would result in 20,000+ miles between chain replacements on my legal 648W (-20%) 250W rated mid-drive conversion. The doubled/thicker cassette might last longer too? The indexed gear shifter would have to go. Would need a custom/double cogged adapted beefed up derailleur. Or if I installed a more powerful mid-drive motor and only needed one gear, for flatish terrain, I could simply use two bicycle chains? Of course, bicycle chains would wear faster, a single motorbike chain would last much longer. Someone must have tried something like the preceding already? Might be terrible ideas. Perhaps use of such contraptions ended in disaster and fatalities.

Edited January 7, 20242 yr by guerney

I remember my first Green raleigh bike inthe early 70's 'as a young nearly teen, it had 3 spd sturmey and had a frame not unlike a pashly or swizzbee type design.

I was privileged. My dad bought me my first bike in 1963 for passing my 11+. It was a used BSA with 4-speed Sturmey Archer gears. Nobody else had 4- speed. It was definitely better than 3-speed. At the time, it seemed like a reward, but actually was the necessary transport to get to the grammar school 4 miles away. As well as to school every day, I went everywhere on that bike mainly for fishing. I was gutted that he sold it without my knowledge when we moved to Germany. He figured that I could ride my sister's bike but she couldn't ride mine, so all bikes were sold except the one. Thereafter, I never saw any of my sisters nor my mum ever ride a bike, but I still needed a bike to go fishing and generally get around, so had to suffer the ignominy of riding a girls bike until I finished University and was able to buy a Vespa 90 for £30.

Edited January 8, 20242 yr by saneagle