Rad City Chainring advice to increase top speed! Help Please!

[BKing]

Do you have the controller set for 40 kph?
It comes with 32kph. The drag might improve at 40. The wind resistance is the biggest issue I see with speeds over 19 mph. Why are you reluctant to use PAS 3? With a 12 mile one way commute you should be able to use all the power you want and still recharge every other day.
Sounds like you like to go fast. A 46 tooth is probably what you need.

 

[Geno929]

Do you have the controller set for 40 kph?
It comes with 32kph. The drag might improve at 40. The wind resistance is the biggest issue I see with speeds over 19 mph. Why are you reluctant to use PAS 3? With a 12 mile one way commute you should be able to use all the power you want and still recharge every other day.
Sounds like you like to go fast. A 46 tooth is probably what you need.

Controller is set at 40 kph. Not reluctant to use PAS 3 or 4 for that matter, I want to lower my pedal cadence and maintain or improve speed. When I know I can pedal faster, but the motor is resisting me, it's a problem. If I could remove the limit regulator from the controller, I would. I'll try the 44 tooth that's on the way and give an update!

 

[Geno929]

I would guess 130BCD, just by looking at the picture

So, the 130 BCD 44 tooth chainring arrived yesterday. Too small. I think it's a 140 BCD 44 tooth chainring I'm needing. Time to return and re order! I'll let ya know how it works out. Today, my 24 mile jaunt, at 25 mph in 7th gear PAS 2, the motor controller kept kicking in to slow me down! That's what I'm trying to avoid!

 

[BKing]

So, the 130 BCD 44 tooth chainring arrived yesterday. Too small. I think it's a 140 BCD 44 tooth chainring I'm needing. Time to return and re order! I'll let ya know how it works out. Today, my 24 mile jaunt, at 25 mph in 7th gear PAS 2, the motor controller kept kicking in to slow me down! That's what I'm trying to avoid!

Try PAS 3 and let me know if it’s different.
PAS 3 in most cases gives more power than PAS 4 or 5 when going fast (firmware bug).
Also, you had said before that you wanted to slow down your pedal rate, now you are talking about the motor resistance. Two different things. Also be sure it’s not wind resistance that is adding up and maxing out at 25 because that is what I see on mine unless the hill is steep.

 

[Geno929]

Try PAS 3 and let me know if it’s different.
PAS 3 in most cases gives more power than PAS 4 or 5 when going fast.
Also, you had said before that you wanted to slow down your pedal rate, now you are talking about the motor resistance. Two different things. Also be sure it’s not wind resistance that is adding up and maxing out at 25 because that is what I see on mine unless the hill is steep.

Today in PAS 2 and occ. 3, I could actually feel the motor kicking in and resisting my effort to increase my cadence. Right at 25 mph. When I took it to PAS 1, resistance ceased. I felt that I could pedal faster without much effort, but was stymied by the motor. Have you ever been in too low of a gear, and felt like you could pedal faster, but it just felt like you were spinning? I wanted to pedal faster, but the motor was not letting me! Ugh!

 

[BKing]

If your pedals are just spinning you need a bigger chain ring. I have not tried PAS 1 at a high speed. You may be on to something in that any power to the motor at a hill speed higher than say 24 is acting like a brake where you really just want a mechanical bike at that speed. I don’t have any hills here to try it on until I take it to the mtns. Try PAS 0 on a steep hill and see if motor magnet drag is noticeable.

 

[EBJ]

Some standard 5 bolt chainring sizes and their corresponding bolt hole center-to-center distances are:

110 mm = 64.7mm = 2.55"
130mm = 76.4mm = 3.01"
135mm = 79.5mm = 3.13"
144mm = 84.6mm = 3.33"

 

[Jim Mass]

The issue is the gear cartridge. The RAD city has a 47 T. About a year ago there was a post about changing the gear set to a 36 T , in the set the high gear was probably a 10 T (T is number of teeth). I'm a recreational rider, averaging 1.5 days per week. Just turned 1,700 miles - 2 years old. Once I find the gear set my "mechanic" is going to swap it out. He is a racer and is the Velofix franchisee is San Diego. He has been very helpful. I have no pedal resistance higher than mode 3, which I use on the road to keep up with the cars (25 mph speed limit).The gear set is the issue.

 

[Geno929]

The issue is the gear cartridge. The RAD city has a 47 T. About a year ago there was a post about changing the gear set to a 36 T , in the set the high gear was probably a 10 T (T is number of teeth). I'm a recreational rider, averaging 1.5 days per week. Just turned 1,700 miles - 2 years old. Once I find the gear set my "mechanic" is going to swap it out. He is a racer and is the Velofix franchisee is San Diego. He has been very helpful. I have no pedal resistance higher than mode 3, which I use on the road to keep up with the cars (25 mph speed limit).The gear set is the issue.
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The 2020 Rad City has a 42 tooth front chainring and an 11 - 32 rear freewheel. In the past versions it was a 46 tooth chainring, but I'm not sure of which freewheel gearing was utilized. Today my ave. speed was 17.4 mph w/ top speed 29 mph. I'm sure this was going down a hill on my commute to work. Keep up the good work! Thanks!

 

[Jim Mass]

The issue is not the pedal gear, it is the cluster cartridge gears attached to the rear motor. The RAD City gear set is a 47 T (number of teeth on the largest gear # 1). Rad's # 7 is close to a 15 T. Last year a member reported that he changed his cartridge to a 36 T which changed the highest gear probably closer to a 10 T. I just started scrolling through the posts when I saw your post.

I have wished for a higher # 7 gear since I rode about 600 miles the way it is. Just turning 1,700 miles I'm really ready for it. My Velofix mechanic says lowering the tooth diameter will increase the exercise and top speed. You may have noticed that there is very little pedal resistance Mode 3 and higher, so I stay mostly in Mode 1 and 2 . If by chance the person who wrote that post last year is reading this one, would you please comment on the cartridge you bought and what your impression has been.

 

[Jim Mass]

OOPS!! MIstake ...Sorry. Edit previous The chain crank gear is a 46 T as reported by others The rear gear set cartridge is a "DNP 7-speed Freewheel 11-34 T. The "Freewheel" is what you want. I'm talking to Shimano this morning to see if they make a 10-32 T. I wonder if that old post was talking about changing the chain crank gear. More research needed on my part.

 

[EBJ]

There are 10 tooth rear cogs out there but they are very rare and I've never seen one that fit a standard freewheel or cassette. The smallest cogs on conventional freewheels/cassettes are 11 tooth. Shimano used to make a 9 to 26 tooth cassette in the Capreo group, but it didn't fit conventional freehubs and has been out of production for quite some time. The City uses a freewheel, like all multi-speed Rads.

 

[Jim Mass]

There are 10 tooth rear cogs out there but they are very rare and I've never seen one that fit a standard freewheel or cassette. The smallest cogs on conventional freewheels/cassettes are 11 tooth. Shimano used to make a 9 to 26 tooth cassette in the Capreo group, but it didn't fit conventional freehubs and has been out of production for quite some time. The City uses a freewheel, like all multi-speed Rads.

Thanks for the info EB. That is the reason the discussion is on a different crank set. Have you switched yours for a lower tooth gear?

 

[Jim Mass]

My 2020 Rad City is an awesome bike. But, for me, in the flat, I spend most of my time in 6th or 7th gear. Top speed around 24.5 mph, in PAS 0 or 1. I am wanting to increase the current chainring from 42 tooth, to maybe 44 or 46 tooth. Two issues I have found and need advice.
1) What is the size and measurement of the 2020 Rad City Chainring: BCD 130 - 42 tooth 5 bolt, BCD 140 -42 tooth 5 bolt or something else?
2) With the increase chainring to 44 tooth or 46 tooth, will I need a new, longer chain?
I have put three chaingring into my basket at Amazon, and have had to CXCL them because I'm unsure of the proper sizing of the chainring. A video on You tube shows a chainring upgrade on a 2018 Rad Rover, but it's clearly 4 bolt pattern.

And this video. Also for an earlier Rad Rover.

Thank You for the knowledge and advice.

Geno,
I have a 2018 ( Retired living in San Diego I ride recreationally.) with the 46T and want to go smaller as I ride in 6th & 7th all the time and need 1 gear size lower. Maybe a 38 T. I'm 6 foot 1 inch 230 all up weight. Maximum speed in PAS 3 is 23.1 on flat ground. I ride mostly in PAS 1 about 25 miles average per ride. At 16-20 mph.

Wednesday I passed a road bike in PAS 2 at 21.5 mph. What a rush.!! He said he was embarrassed to be passed by a "cheater" bike though he was getting older and was impressed by the performance and the price. At age 76 I love it. Just turned 1,700 miles.

My complaint is lack of "pedal resistance" over 21 mph. Reason I only use PAS 4&5 in really steep hills. Feels like I need another lower gear. So I'm researching chain rings. Has anyone tried or can one even buy a chain ring 36-38 T?

 

[Sierratim]

My 2020 Rad City is an awesome bike. But, for me, in the flat, I spend most of my time in 6th or 7th gear. Top speed around 24.5 mph, in PAS 0 or 1. I am wanting to increase the current chainring from 42 tooth, to maybe 44 or 46 tooth. Two issues I have found and need advice.
1) What is the size and measurement of the 2020 Rad City Chainring: BCD 130 - 42 tooth 5 bolt, BCD 140 -42 tooth 5 bolt or something else?
2) With the increase chainring to 44 tooth or 46 tooth, will I need a new, longer chain?
I have put three chaingring into my basket at Amazon, and have had to CXCL them because I'm unsure of the proper sizing of the chainring. A video on You tube shows a chainring upgrade on a 2018 Rad Rover, but it's clearly 4 bolt pattern.

And this video. Also for an earlier Rad Rover.

Thank You for the knowledge and advice.

I'm late to the party here, but I believe this is new info that might help.

You can calculate the impact a change in the chainring will make with several available online calculators. I like THIS ONE. Enter the bike's parameters (I found them on the product page), your cadence target, and chainring tooth count (up to 3 at a time) and it will calculate your road speed for the various cassette and chainring gear combos. For 42t, 44t & 46t chainrings I got 18, 18.9, & 19.7mph at a cadence of 60rpm. Basically you can check out the effect of a couple of extra teeth on the chainring before you buy.

As to the original chainring size, apparently it's not 130BCD. This page gives an overview of how to measure BCD. As others have posted, measure the center-to-center distance between any two adjacent chainring bolts and multiple by 1.701 (for a 5-arm crank) to get BCD. This page provides even more info on this topic.

Will you need a new chain? You might get away with adding 2 teeth to the chainring and keep the original chain. More than that and you'll probably need a longer chain to keep your shifting smooth. This article discusses how to check and set your chain length. Park Tool also has a good video on this; to the Google for that one.

How this helps.

 

[Jim Mass]

Sierra. I tried your calculator with the following chain ring sizes.
Results: 46 T on 11 gear = 108.5; 42T on 11T gear = 99.0 and 52 T on 11 gear = 122.6

I don't care that much about top speed. Would I like to get up to 25 mph? sure...Though at age 76 riding in a t shirt and bike pants don't want to fall off it at that speed. More so peddle resistance. Which chain ring would increase peddle resistance?

 

[Sierratim]

Sierra. I tried your calculator with the following chain ring sizes.
Results: 46 T on 11 gear = 108.5; 42T on 11T gear = 99.0 and 52 T on 11 gear = 122.6

I don't care that much about top speed. Would I like to get up to 25 mph? sure...Though at age 76 riding in a t shirt and bike pants don't want to fall off it at that speed. More so peddle resistance. Which chain ring would increase peddle resistance?

Jim,

Looks like you selected "gear inches" for this calculator's "Gear units"? I find it easier to discuss peddling 'spin out' as the OP implied when selecting a cadence/rpm value. With that said, this calculator won't estimate the rider's effort. Other calculators do this, though they need to know much more about the motor output. Grin Technologies has a popular calculator that will help with this.

So, which chainring will increase pedal resistance? The simple answer is any chainring with a tooth count higher than you have now. Not helpful, I know but in knowing your comfortable cadence range and motor electrical characteristics you can use available online calculators to get this data.

Maybe what you really want is to avoid 'spin out' under your riding conditions? The calculator at sheldonbrown.com can help with this using rpm as "Gear units".

 

[EBJ]

...My complaint is lack of "pedal resistance" over 21 mph. Reason I only use PAS 4&5 in really steep hills. Feels like I need another lower gear. So I'm researching chain rings. Has anyone tried or can one even buy a chain ring 36-38 T?

I think you've got this completely backwards. If you want to avoid spinning out/add pedal resistance in 6th or 7th gear, you need a front chainring with more teeth, not less.

 

[Jim Mass]

Hmm Sierra, Not sure I understand everything you said. What does "spin out" mean? Back 3 years ago before buying the electric bike I had a 24 speed cross-over bike. 3 gears in the front and a 8 gear cassette in the rear. Mostly I rode it in 16th-17th range and always had pedal resistance. If it got to be too much I would down shift.

I know I can't compare the bikes because there is a lot of difference between the 63 pound ebike and the regular 30 pound cross-over.

I ride the RAD step thru in PAS 1 (what I call exercise mode) in 7th gear at about 15-18mph and have plenty of pedal resistance 95% of the time. I get a hill I use the throttle. When I am on the street (25 mph posted) I ride PAS 3 -7th to keep up with traffic. No resistance so I use a lot of throttle to maintain 23 mph. In inclines of 3-4% I'm in PAS 3-4 in 4th -5th gear with plenty of resistance. Highest hill I've ever climbed was 6% grade in PAS 5, gear 1 - going 1 mph with lots of resistance. I crested the hill sitting down. Proud of myself, Don't plan on doing that again.

Maybe how I'm riding on the flat 95% of the time for exercise is all the RAD City is capable of for the money I paid. If I want more I will have to upgrade to a $4K bike. At my age not worth it.

One last thing. I finally upgraded the seat post to a "Thunderbuster ST G4." Best decision I ever made. My butt is very happy now. 25 miles now feels like 18 instead of 35.

 

[Jim Mass]

I think you've got this completely backwards. If you want to avoid spinning out/add pedal resistance in 6th or 7th gear, you need a front chainring with more teeth, not less.

Thanks EB I think you answered my question. There is a 52T chain ring I saw online that based on Sierra's formula has a final ratio of gear #7 somewhere around 122.6 as I inputted the other numbers. Wheel diameter - Tire size 26 x 2.125, 170 mm crank, Shimano 11-34 T - speed "mega-Range Freewheel, . The 46 T 108.5 on Gear # 7 should be more resistance...maybe??