Is Changing the rear sprocket possible?

[blackphoenix38]

From all the research I've done so far has been dead ends. The last thing I see is that BRP hard coded the sprocket size in the ECU and changing it would cause issues. Has anyone been able to change the rear sprocket without issues?

[pegasus1300]

In a word "NO".

[KX5062]

I too would doubt it. Other people have changed the rear sprocket sizes between the F3 size and the RT size without any reports of nanny trouble.

[Possible]

In a word "NO".

Just curious if that "NO" is in response to the question, or a response to "will it cause an issue with the Nanny"?

[larryd]

Do a forum search...No one here has done it successfully...Jese, a tuner from Australia said he had accomplished this task...He reported that he was going to contact some of his customers over there and he needed to refresh the procedure he used to accomplish the change...Still waiting to hear back...I have a new sprocket and belt in stock waiting to do my 2014 RTS...There are several RT and F3 owners wanting to make a change...Some wanting to go from the 79T sprocket to the 89T...And others wanting to go from the 89T sprocket to the 79T...

I hope someone gets it figured out...I'll be one of the first to go from 79T to the 89T set up on my RTS...

larryd

[troop]

And me from a 89t > 79t

[larryd]

And me from a 89t > 79t

If anyone ever get this sprocket deal figured out we'll need to set up a "wanting to swap/trade sprocket & belt area"...And start saving each other some $$$$$$$$....larryd

[pegasus1300]

Don't overthink this, it is a simple answer to a single question, " Has anyone been able to change the rear sprocket without issues?" There are some who are trying and some reports of someone who may have overcome the issues, but there are still issues.

[blackphoenix38]

thats disappointing for something so simple. I love the spyder, but I feel like it's overly complex in some areas.

[blacklightning]

thats disappointing for something so simple. I love the spyder, but I feel like it's overly complex in some areas.

I agree. Changing gearing in a belt or chain driven bike or trike should be a simple thing to do. Now that I have felt the difference in acceleration with the larger sprocket, it would be hard for me to go with anything else, unless more hp was added to the engine.

[larryd]

I have a new 89T black sprocket and matching belt that I would be willing to loan someone who would like get this sprocket changing challenge accomplished...So if there is some tech savvy guru out there who's looking for a challenge please contact me...larryd

[pauly1]

Change rear sprocket from 79 to 89 tooth on 2023 F3-L

I tried to search but didn't find any significant result. Can the sprocket and belt be changed without the nanny complaining? I know about ECU flash and throttle body manipulator thingies. I want to change the gear ratio back to the F3-S era.

Thanks,
Wayne

[Peter Aawen]

There's a bunch of threads here already discussing this, and the basic answer is still the same - for all intents and purposes, even tho you might be able to physically do it; even tho some may have done it and managed to get it to work for a while; ultimately, it appears that it doesn't work for too long before one of the numerous places it's coded in one or more of the computers will trigger a Limp Home or a complete shut-down!!

So, as has previously been stated in this thread, NO, you can't do it successfully/without issues (eventually)!

Here's one of the (other) earlier threads:

https://www.spyderlovers.com/forums/...ar%3B+sprocket

You can probably find more by typing "Rear; + sprocket" into the Search box up toward the top Right; ticking the 'Search Titles Only' box; and submitting the Search. Do note that there are a few threads where someone might say they've done it and it's working, then the thread never gets updated any more... If you then search elsewhere for more on that particular bike, it usually becomes clear pretty quickly that it might've worked for a shirt while, but then the gremlins start creeping in and rapidly multiplying!!

[Isopedella]

Now that search makes some interesting reading . Whoodathunkit.
So yes ya can change it but it really upsets the Nanny.

[BLUEKNIGHT911]

Now that search makes some interesting reading . Whoodathunkit.
So yes ya can change it but it really upsets the Nanny.

IF you have a MANUAL transmission .....why would that upset the NANNY ?????? .....Mike

[Isopedella]

IF you have a MANUAL transmission .....why would that upset the NANNY ?????? .....Mike

I guess because the world is blue/green/white from out there and the ducks dont seem to care.

At least for a "for a shirt while"

[Peter Aawen]

IF you have a MANUAL transmission .....why would that upset the NANNY ?????? .....Mike

After spending quite some time going thru how changing rear sprockets will &/or won't work with a variety of people much more knowledgeable on the subject than me, this is how I understand it all...

It doesn't matter what transmission you've got, it seems that pretty much every component/computer that makes up the Nanny, things like the ABS, the EBD, the Stability Control, the Traction Control, etc, etc ALL have pre-set expectations of the relationship between the OEM Sprocket size and the front & rear wheel rotation speeds et al... and there's likely more relationships too (even the bloody radio (??) has some built in! ) - all of which are effectively 'hard-coded' into the various systems &/or sensor feeds and spread out thru these multiple systems in many places each!

So if you change the rear sprocket, ALL of those systems/sensors & pre-sets get to see a difference between the sensor inputs and what they expect; initially, if the re-calibration has been done reasonably well, this is apparently not a biggie & it looks like it might've worked; but over time, the sensors start sending in a few 'discrepancy reports' where they see differences between the info they're getting and what they'd expect given the OEM Sprocket size. The more the rear wheel rotates at a different speed to that the 'Nanny' or all of these collective systems expect, the larger the number of 'discrepancy reports', until what started out as a small trickle of minor errors eventually grows into a raging torrent of significant discrepancies between what all these things EXPECT to see because of the designed sprocket size and what they ACTUALLY get to see due to the different sprocket size, and that increasing torrent of discrepancies and errors eventually results in a shut-down!!

So even if it looks like it might've worked initially, so far, it doesn't really, not in the long run...

[larryd]

After spending quite some time going thru how changing rear sprockets will &/or won't work with a variety of people much more knowledgeable on the subject than me, this is how I understand it all...

It doesn't matter what transmission you've got, it seems that pretty much every component/computer that makes up the Nanny, things like the ABS, the EBD, the Stability Control, the Traction Control, etc, etc ALL have pre-set expectations of the relationship between the OEM Sprocket size and the front & rear wheel rotation speeds et al... and there's likely more relationships too (even the bloody radio (??) has some built in! ) - all of which are effectively 'hard-coded' into the various systems &/or sensor feeds and spread out thru these multiple systems in many places each!

So if you change the rear sprocket, ALL of those systems/sensors & pre-sets get to see a difference between the sensor inputs and what they expect; initially, if the re-calibration has been done reasonably well, this is apparently not a biggie & it looks like it might've worked; but over time, the sensors start sending in a few 'discrepancy reports' where they see differences between the info they're getting and what they'd expect given the OEM Sprocket size. The more the rear wheel rotates at a different speed to that the 'Nanny' or all of these collective systems expect, the larger the number of 'discrepancy reports', until what started out as a small trickle of minor errors eventually grows into a raging torrent of significant discrepancies between what all these things EXPECT to see because of the designed sprocket size and what they ACTUALLY get to see due to the different sprocket size, and that increasing torrent of discrepancies and errors eventually results in a shut-down!!

So even if it looks like it might've worked initially, so far, it doesn't really, not in the long run...

BUT, The bottom line is; There are some model F3's with 89T rear sprockets, AND there are other model F3's with 79T rear sprockets...It has to all be in the programming SOME WHERE...There is some way when the bikes are built that some work with 89T sprockets and others work with the 79T sprocket...

My post above, #11 offer still stands...larryd

[BertRemington]

The 89T TCM is a different part number from the 79T TCM. But apparently it isn't that simple. Bosch seems to have hard-coded VIN-related information in the console and maybe the ECM and VCM. Just like the console options change based on whether on not a radio is installed, I believe the console tries to match VIN-related information across TCM and VCM. You can see this behavior with BUDS which provides VIN-related options for firmware upgrades. Just a hypothesis.

If someone wants to experiment, I have an 89T TCM and larryd has the 89T sprocket and belt.

[Peter Aawen]

BUT, The bottom line is; There are some model F3's with 89T rear sprockets, AND there are other model F3's with 79T rear sprockets...I has to all be in the programming SOME WHERE...There is someway when the bikes are built that some work with 89T sprockets and others work with the 79T sprocket...

My post above, #11 offer still stands...larryd

And each of those models will run their respective OEM Sprockets juuust fine; but you can't just swap them to the other one, change that one toggle in BUDS, and get your F3 that should have one Sprocket to run for too long on the other Sprocket. This is cos that sprocket designation thing is not just in that one place...

So it isn't just SOME WHERE Larry, it's pretty much EVERYWHERE, and to get it to work over the long term, you hafta find EVERY SINGLE REFERENCE and re-code it, something that I don't believe anyone's managed to do so far!!

So again, it might SEEM like it's been made to work INITIALLY, then this increasing cascade of problems starts....

But I too would love to see it be made to work somehow.... Harking back to my 'large software system' days, I asked a couple of the fellas here on Oz who've been working on this if a smart coder could work out how to do a 'replace all' for one sprocket size to replace it with the other, but apparently it's already been tried, and they found that there's STILL some places they haven't found yet where the sprocket/model info is hidden/embedded which screws up an attempted swap eventually!!

[pauly1]

First, thanks, Peter, for explaining a search method: "rear sprocket", for me, did not yield useful information.

r.e. changing sprockets. The on-board electronics, ECU, TCU, etc, are generic until a VIN is coded into the system. The VIN can be changed using a Megatech license, no? So if one were to change the VIN to a known bike with an 89-tooth sprocket as standard equipment, then the reprogramming should take care of itself. I would expect the VSS, TCU and ECU would be the ones primarily affected. The brake encoders are mounted directly to the wheels, so antilock braking should be OK. The engine RPM would be 12-13% higher in any gear / speed, indicating to the computer that the rear wheel is "slipping", spinning faster, presummably throwing codes on vehicle stability, even the pitch and yaw sensors are stable. There is probably some master curve with engine RPM vs Gear vs Speed that has a control band about it that incorporates the relative sensor inputs. That would also be true for the F3-P vs F3-S, which were essentially the same machines with different control parameters programmed in.

If an ECU can be re-flashed to alter the fuel curves, despite government pollution specs, then the other modules should be able to handle gearing.

There wouldn't be anything illegal r.e. vehicle registration, as the printed VIN on the vehicle still matches the government vehicle registration.

Further rumination, I wonder if I could take the "digital gauge cluster" and rear wheel / belt from my 2018 F3T and install on my wife's F3L to see if it would work? The "T" has an 89-tooth sprocket vs the 79-tooth on the "L".

Wayne

[larryd]

This is just my thought on this subject...I think the computer systems are counting pulses...And when the pulses between the engine speed, gear speed & wheel speed get out of the programed limits the bike goes into the limp mode???

Could making this sprocket change be as simple as having a modified tone wheel or wheels to simulate the the original sprocket size and not recognize the newly changed sprocket???

Jese from Peters side of the world told me his code reader shows the source of the error codes???

larryd

[BLUEKNIGHT911]

The 89T TCM is a different part number from the 79T TCM. But apparently it isn't that simple. Bosch seems to have hard-coded VIN-related information in the console and maybe the ECM and VCM. Just like the console options change based on whether on not a radio is installed, I believe the console tries to match VIN-related information across TCM and VCM. You can see this behavior with BUDS which provides VIN-related options for firmware upgrades. Just a hypothesis.

If someone wants to experiment, I have an 89T TCM and larryd has the 89T sprocket and belt.

Thanks for clearing that up ....Knowledge is power .....and I learned something today ....Mike

[Joel The Biker]

I'm sure it can be done. The only thing you need to do after the install is use BUDS to reprogram the shift points. The speed sensors are on the brake disc's for ABS, VSS, and speed sensing. The only thing that would confuse the nanny is speed vs rpm which can be programmed using BUDS. I have read about the procedure in the past, but have never tried it because I had no reason to.

[blacklightning]

I wonder if you could swap out the ECU and sprocket from a 89 tooth bike to one with 79? If the computer is swapped, I would think it would work. Probably not, but just something my feeble mind was thinking about. I am just thankful that I do still have one with the 89 tooth (2016 F3L Special Series). It even gets better gas milage.