Bosch drive and min/max gear ratio parameters

[owl]

I'm looking into having easier unassisted climbing (that's just how I roll, I'm not interested in losing a tiny bit at the fast end nor do I care about tuning the drive to assist faster) with my Performance Line CX equipped bike. The bike now has a 15t chainring/sprocket and XT 11-42 in the rear. I'd like to change the chainring to a 14t and once Shimano's new 11-46 is out put that in, or use something like OneUp's 45t sprocket. I know 15 (or 2.45*15)/42 should be plenty, but I still want more.

However, the Bosch drive seems to have parameters "minimum/maximum gear ratio" according to a diagnostics report (I don't have one of my own at the moment), and from what I understood from reading a german forum with Google Translate it seemed that some people have been getting annoying errors after messing with the gears, and they've attributed that to these gear ratio parameters. Have any of you guys bumped into this or have experience in such a mod? Are the dealers supposed to be able to change the parameters?

 

[EddiePJ]

If you are using the system in an unassisted mode, I'd be surprised if it started to throw up any error codes at all. When in assisted mode, using say eco and the lowest gear for any great length of time, error codes can then appear. I suspect that is more down pedal cadence than anything else.

My biggest concern about altering the gearing to that degree would be the rear mech, and whether it could cope with that range.

You might also find that whilst the gearing is made lower, that you are then having to spin more for the same rate of forward progress. Fine if you are happy to do that, but it could soon become tiring.

My OE set up was 11-36, which was for my use was fine for when out solo riding in the UK, but wasn't so great if I wanted to ride with pedal mtb riders. I also wanted lower gearing for when riding in the Swiss alps.
I've now switched to an 11-42 set up, but oddly haven't used the 42 as much as I thought that would.

It'll be interesting to see how you get on.

 

[soundwave]

https://bythehive.com/pages/drivetrain

 

[owl]

If you are using the system in an unassisted mode, I'd be surprised if it started to throw up any error codes at all.

Yeah, I thought about that too, but there might be occasions where I wouldn't like to think about too much if I have the assist enabled or not and still use whole range. However, if this is the way it's gonna be, I can live with that - I don't see using 46t (or whatever) on my daily commute which is where I use assist the most as I just want to get from point A to point B.

My biggest concern about altering the gearing to that degree would be the rear mech, and whether it could cope with that range.

Another good point. From Shimano's words one might interpret that the new cassette doesn't need other mods to drivetrain ("Wide ranging 11-46T cassette compatible with XTR or DEORE XT 1x11 set ups") (edited, I wrote something daft here, twice). I have the medium cage, so that might need an upgrade. We'll see.

I'll update here in case I get something done!

 

[anotherkiwi]

I mounted a megarange in rear in order to have a granny gear for getting home un-powered. So far I have only used it for showing off (climbing walls and the like ) and one day I found some obscene hills on the way home from S. Sebastian on an "exploration" route.

 

[owl]

I contacted Bosch since the dealers I contacted didn't have a direct answer. Bosch in their prompt and surprisingly nice reply (not at all the copy-paste "we're sorry for the inconvenience" reply companies usually send) said that the 14t front sprocket should be ok by default, but ultimately it's up to the manufacturer and whatever parts/configuration they have listed for the CE marking and programmed the drive accordingly. So, I guess we're once again dealing with a situation where if something goes wrong someone just has to be responsible and take the blame, because everything is always someone's fault, and it's always top priority to get to blame someone and because of that companies are trying to protect themselves from legal blulsiht with measures like this. But I don't blame them, I blame the system. And there's my rant of the day.

Back to the matter, I ordered a new 14t chainring (Connex) and a new lock ring (by Bosch, I suppose). I'm not sure if I needed the lock ring, but it wasn't that expensive so at least I don't have to order it separately. Once it arrives I'll get it installed and see what happens with the 11-42.

I haven't contacted Cube, since unlike Bosch they have never bothered to answer my questions (regarding a different matter) sent through their website, so I don't expect them to help me this time either.

If you dig German or can tolerate Google Translated English, here's a massive thread discussing the gear ratios: http://www.pedelecforum.de/forum/index.php?threads/performance-möglichkeiten-für-andere-Übersetzungen-motorritzel.25050/

 

[EddiePJ]

Connex is the way to go.

I've now got through enough sprockets of differing make and supplier, to have worked out that Connex make the most durable sprockets available.

I'd would say though, that realistically you still might only get about 500 miles out of it. I get roughly 500-600 miles out of a 15T

Depending upon the conditions that you ride in, you could also be increasing the risk of chain suck occurring.

It'll be interesting to see how you get on. I'm all for lower gearing over taller gearing on an e-mtb.


edit.. I also get through jockey wheels at quite a rate. Whether this is related to my use of the bike in frequent unassisted mode or eco mode I have no idea.

 

[owl]

I finally managed to get the stuff and most importantly the time to change the chainring. As a side note, while working with the crank puller I also took the other crank off, opened the plastic case (three T20 torx screws) and tightened the three 13mm nuts at the end of the bolts that hold the motor to the frame, and that was the end of a nasty creak I used to get on every stroke.

What I didn't have the time for was a proper test drive, so I just drove in circles in the garage with Eco assist. Doing that for a while in different gears, mostly the lowest, produced no errors. I'll keep updating this thread if there's anything worth mentioning about those.

For the curious, here are two photos where you'll see the original 15t chainring, the Connex 14t chainring and the old and the new lockring. You'll note that for the smaller chainring you need the new lockring (Bosch part no. 1270016428, but make sure yourself if ordering) so that the chain doesn't touch it.

 

[Artstu]

I'm looking into having easier unassisted climbing (that's just how I roll,

Couldn't you just add a 12 kg weight to a normal pedal only MTB to get the same effect?

 

[Nothgiel]

I am looking to change my 9 speed derailleur to a rohloff 14 speed hub the gear ratio will be 1.3 to 6.8 will this cause an error on the ebike? If so will the error stop the bike from working? How does it know what gear your using? Is it possible to reprogram the ebike? it’s a BOSCH active line plus.

 

[soundwave]

i have 12spd eagle cassette with 2 front sprockets 20t-18t and no errors and all gears work fine so it should not be a problem.

 

[vfr400]

What version of software do you have, Soundwave, I'm wondering whether the latest version that's in the latest CX motors checks cadence against gearing to try and defeat dongles because there are reports of dongles not working on latest versions.

 

[soundwave]

my bike has had no software updates since it was new if it aint broke dont fix it

he only wants to change to hub gears so at most may need some settings being changed at a dealers with the bosch software but it should work anyway.


and a bad ass dongle will still work

 

[soundwave]

https://www.ebiketuning.com/e-bike-tuning/speedchip.html

you can update the firmware with this one but if you have one where this is not possible then if bosch update there firmware so some dongles wont work anymore then there door stops as imo they will now have to work with the new kiox displays as well.

 

[EddiePJ]

SW, I thought that your bike had the Performance Line drive unit?

When I had mine, I too found that it made no difference, but like you, I also never had any software updates.

As far as I am aware, the CX drive unit is flashed not only for wheel/tyre size, it also takes into account final drive gearing of the front sprocket, and also pedal crank length. I assume that the requirement of pedal crank length, must be to do with reading cadence?

 

[soundwave]

yes i have the performance motor

and yes there is a option now to change crank length tho i cant really see 5-10mm less will do for cadence but with it shorter then i guess will mean less input force going to the cranks.

just get the dealer to set it to 65mm and stick some 75mm ones on it if it works one way then should be the same for the other

also wheel size can only be set buy a dealer with the cx.

 

[Bearing Man]

If you set the crank length to less than 165mm and run 170 -175mm it's lovely! The motor adds power low down to compensate for you trying to set off with short cranks. So, when you have longer cranks fitted it feels like a nice shove of torque, each time you shift gear. More noticeable when peddling lightly