Changing RadMini gear ratios

[BPINE]

I did not I used the above video on how to remove cassette and removed spacer as cayjak did. pretty easy job because of what cayjak posted in this thread.

 

[alkraft00]

Once I determined that the tool would have to be split, I dug out my 30 year old Dremel tool and got to work. My Dremel uses the small 15/16" diameter cutting wheels, and I had some #409 wheels on hand. They worked fine for this job. I used one wheel on each side. Cutting the DNP tool was not hard - it just takes a little care and patience to make straight clean cuts. I wanted to remove as little material as possible, so that the tool would still fit properly after being split. It worked out great. Photos below show the progress of the cutting from start to finish.

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I’m sure you’ve had plenty of requests, but any chance you’d loan out that removal tool you cut in half?

 

[kamakazi17]

I’m sure you’ve had plenty of requests, but any chance you’d loan out that removal tool you cut in half?

I took a $4 mini hacksaw I bought from Lowe’s and a clamp and sawed away. You can cut it in half manually within 15-20 mins of elbow grease. You don’t need a dremel tool to cut the freewheel tool. And you’ll want one when you replace the freewheel in the future

 

[cayjak]

I’m sure you’ve had plenty of requests, but any chance you’d loan out that removal tool you cut in half?

Sorry, but I already loaned my split tool to another guy in our RV club. He is somewhere halfway across the country, and I probably won't see him again for 6 months. Like stated above, not hard to cut one in half yourself, or take it to a machine shop and give the machinist a 6-pack of his favorite brew to do the job for you.

 

[BPINE]

I wouldn't bother with the tool, just use the method in the video in this thread it works perfect an there is no reason to keep the old 18 dollar sprocket set you will never go back and of you do buy a new one.

 

[kphelan]

New RadMini (2018 model) owner here. I find the discussion in other threads about changing gear ratios interesting, because I too would like to slow down my pedal cadence. To do this, as I understand it, you can change either the rear gears (the freewheel), or the front chainring, or both.

The stock freewheel (on my 2018 RadMini) is a Shimano MF-TZ500-7 with tooth count of 14-16-18-20-22-24-28. If you change to the DNP 11/28 freewheel (link below), which is a direct replacement, it has tooth count of 11-13-15-18-21-24-28. With the DNP, you are reducing your pedal speed in 3rd through 7th gears, but the two lowest gears (1st and 2nd) remain unchanged. Replacing the freewheel may require a special deep thin wall freewheel tool.

On the other hand, if you change the front chainring from the stock 48 tooth to a larger 53 tooth (link below), you will decrease your pedal cadence (at any given speed) in ALL 7 gears. Replacing the chainring will require replacing or lengthening the chain.

For the greatest possible degree of change, you could replace BOTH the freewheel AND the front chainring.

The question is: which option, new freewheel or new chainring, gives you the most bang for the buck?

To answer this question, we can reduce each combination to a simple number called "gear inches". To find this number you divide the number of chainring teeth by the number of teeth on the freewheel sprocket. This produces a "gear ratio" number. Then you multiply the gear ratio by the diameter of the rear wheel. This produces the "gear inch" number.

Since most of us are primarily interested in decreasing our pedal cadence in top gear, I will only do the 7th gear calculation for the the stock setup, plus the 3 possible combinations listed above. I used 22" for the wheel diameter, because that is what is set in the motor control panel on my bike.

Here are the results, listing the percent improvement over stock for each combination, in 7th gear:

( stock ) 48t chainring divided by (stock) 14t (7th gear) sprocket = 3.43 ratio times 22" wheel diameter = 75 gear inches (stock)

(bigger) 53t chainring divided by (stock) 14t (7th gear) sprocket = 3.79 ratio times 22" wheel diameter = 83 gear inches (11% better than stock)

( stock ) 48t chainring divided by (DNP ) 11t (7th gear) sprocket = 4.36 ratio times 22" wheel diameter = 96 gear inches (28% better than stock)

(bigger) 53t chainring divided by (DNP ) 11t (7th gear) sprocket = 4.82 ratio times 22" wheel diameter = 106 gear inches (41% better than stock)

Cost of modifications:

Replacing the front chainring costs about $53 (Amazon Prime) plus the cost of replacing or extending the chain, for 11% improvement.
Replacing the freewheel costs about $32 (Amazon Prime) plus the cost of a freewheel tool (use the original chain), for 28% improvement.
Replacing both the front chainring and the freewheel costs about $85 (plus cost of chain and a freewheel tool) ), for 41% improvement.

My conclusion:

If your primary objective is to slow down your cadence in the upper gears (3rd through 7th) for the least expense, then the new freewheel would seem to be the best choice. Although I only calculated the percent change in 7th gear, you would also see a improvement in gears 3 through 6. If it turns out you still want more reduction in pedal speed after trying the new freewheel, you could then replace the front chainring.

NOTE: I am just a novice at this bike gear stuff, so if I made any errors in my math, please feel free to point them out!

https://www.amazon.com/gp/product/B071LPKGT2/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

https://www.amazon.com/DNP-Epoch-Freewheel-Nickel-Plated/dp/B007A8RPUS

This is brilliant. Thank you for your detailed and concise analysis. I've had my Mini for one month and have been looking for this exact answer. Thank you.

 

[cayjak]

This is brilliant.

Don't know about that, but happy to be helpful. By the way, I'm still totally satisfied with our Rad Mini after the freewheel upgrade, and I have no desire to change the front chainring.

 

[Tom899]

I received my freewheel and tool yesterday, got out my dremel and cut the tool in half. I'll be installing it this morning, remembering to leave the original spacer off.

 

[cayjak]

Take your time, and savor the experience! I think you will enjoy the more useful gear ratios.

 

[Tom899]

I just finished the freewheel swap. Nice upgrade! I didn't even have to adjust the derailleur. It actually shifts quicker and more positive than before! The split tool would not work for me though. The freewheel was very very tight. I had to remove the freewheel by removing the inner ring, and then use a pipe wrench to remove the rest of it.
Update!
Just got back from a 10 mile ride. I used to be comfortable cruising in level 2 and 13 or 14 mph using all the gears. Now it seems normal to use level 3 and cruise around 17 or 18mph, gear 5,6,7 is great!. I can still do my level 2 and 13 or 14mph, but the nice option to cruise higher is there!

 

[Newbflat]

Any thought on if the 30-11 freewheel would require more links or a different derailleur?

 

[Tom899]

For sure it wouldn't need a different derailleur. I also doubt it would need more links, but, have a couple extra KMC MISSING LINK Bicycle Chain Links on hand. I bought a 6-Pack on Amazon for $7.69. I also bought a new KMC Z8 chain on Amazon for $12.97, 116 link, exact replacement. It shifts better than new!

 

[Newbflat]

I don’t have access to my bike for a few days for the specific model, but all the tourney derailleur I can find all say 11 or 14 to 28 tooth Max. I ordered a 11-30 and now I’m not sure it will work.

 

[danielrr]

@cayjak, any reason why you picked the DNP freewheel and not a Shimano like the SHIMANO CS-HG41 (https://www.mec.ca/en/product/5059-989/CS-HG41-7-Speed-11-28T-Cassette)? I'm looking to reduce my cadence as you did but the DNP is more expensive to get for me in Canada, and I've found the Shimano on MEC.ca which I can get for cheap. I'm not sure it is compatible though, can you help me out?

Thanks for this investigation btw... I've also read about your road tires (Sunlite XL Cruisers) on another post and I ordered those yesterday.

 

[AHicks]

I think you're looking for a freewheel type vs. the cassette. They aren't interchangeable.

 

[danielrr]

I see, thx for that. Are all freewheels interchangeable?

EDIT: I found a DNP Epoch on ebay.ca for 33$USD and free shipping, ordered.

 

[cayjak]

@cayjak...any reason why you picked the DNP freewheel...

Yes, as noted above, you must use a freewheel in this application. I can't say "all freewheels are interchangeable" because I'm not a expert on that stuff. I can say, after much reading here, and on other bike forums, that the DNP was the only suitable replacement unit I could find with both 7 speeds and a 11-28 tooth sprocket set. There just isn't much choice out there for this specific size freewheel.

I have been very happy with the Sunlite XL Cruiser tires. They are working great for my riding style (fun/exercise riding 99% on pavement). No flats yet - knock on wood.

 

[danielrr]

Thanks guys!