Increase rotor size to 220mm on 160mm posts

[Lectriceye]

I have 180mm rotors on front and rear with 160mm caliper posts, which are not adequate for my weight and the long steep decents that I ride regularly. General informations says I should increase the rotor size, which will require a different adapter than the 20mm now in place. The choices of adapters seem pretty standard when going to 200mm rotors but not much information when going to 220mm rotors on 160mm posts (+60mm). Wondering if anyone has done this, was the transition successfully, and what adapters are available? It looks easy to go to 200mm rotors, but I don't want do that and then discover It wasn't enough, and have to do it again.

 

[neptronix]

No build threads in your sig, so i don't know what you're working with, bike wise.

220mm rotors have a massive amount of leverage vs 160mm. What are your disc brake interfaces rated at? There will be a limit suggested by the manufacturer, which is based on the underlying strength of what it connects to. A 200mm rotor would be dangerous to operate on such an interface. A 220mm rotor, even more dangerous.

I live in an extremely mountainous area. We have protracted 5-20% grades all over the place. I use very strong regen in place of a rear mechanical brake, and the primary benefit is that my rear brake doesn't fade. That means i don't need oversized rotors in order to add thermal mass.

Going down these mountains with a BBS02 and dual 200mm mechanical brakes was terrifying; same with beefy rim brakes. Within a mile you'd start to feel major fade. The consequence of heat saturation on the braking medium is for a tire to pop off if you have vbrakes, or a disc brake wadding up. Either failure sends you flying at speed. So i would constantly ride a mile, stop and let the brakes cool, ride a mile, etc..

My car also has brake fade going down the mountain but nowhere near as severe.


But this is no problem with a big hub motor doling out >1kw of regen braking power. Braking is predictable and consistent. The rear is doing most of the work, so front disc fade is now a non issue. The fact that i'm getting large amounts of energy back into the battery is the icing on the cake.

 

[Mongo]

Hi @Lectriceye, is the bike in question a dual-motor (originally a geared hub factory bike, now with added-on BBSHD) aluminum-framed fat bike, about 300 lbs rolling weight, and perhaps with a suspension fork? If so, you may want to consider increasing it to 203mm (at most), using the standard 160mm to 203mm post mount. As I understand it, that would likely be pushing the limits of a medium-quality suspension fork, or a fixed aluminum one. If the caliper is cable-driven, I'd also get compressionless housing.

Some rotors/brake pads claim better heat shedding if that is the real issue during your descents.

You sound like an ideal candidate for a regen-capable hub motor, too bad.

 

[E-HP]

Have you already tried the finned brake pads?

 

[Lectriceye]

Hi @Lectriceye, is the bike in question a dual-motor (originally a geared hub factory bike, now with added-on BBSHD) aluminum-framed fat bike, about 300 lbs rolling weight, and perhaps with a suspension fork? If so, you may want to consider increasing it to 203mm (at most), using the standard 160mm to 203mm post mount. As I understand it, that would likely be pushing the limits of a medium-quality suspension fork, or a fixed aluminum one. If the caliper is cable-driven, I'd also get compressionless housing.

Some rotors/brake pads claim better heat shedding if that is the real issue during your descents.

You sound like an ideal candidate for a regen-capable hub motor, too bad.

Thanks Mongo, you hit the nail on the head. The bike is as you described, except it is a steel frame, came stock at 78 lbs. I Added BBSHD, another 20ah battery and me with pack at abuot 225. My load estimate is aabout 310l-320bs. I have Zoom HB-876 Hydrolic brakes. The Mfr Specs says max payload at 350 lbs. I have about 1000 miles on these rotors and they look like they should be changed regardless. I do notice that the front rotor shows wear on about 70% of the blade whareas the rear rotor only shows wear on about 50% of the blade, I am not sure if this is normal.

 

[E-HP]

Thanks Mongo, you hit the nail on the head. The bike is as you described, except it is a steel frame, came stock at 78 lbs. I Added BBSHD, another 20ah battery and me with pack at abuot 225. My load estimate is aabout 310l-320bs. I have Zoom HB-876 Hydrolic brakes. The Mfr Specs says max payload at 350 lbs. I have about 1000 miles on these rotors and they look like they should be changed regardless. I do notice that the front rotor shows wear on about 70% of the blade whareas the rear rotor only shows wear on about 50% of the blade, I am not sure if this is normal.

Well if you are already at that weight, then what’s a few more pounds? You need real brakes. Check YouTube on adapting motorcycle forks to bike frames. They also sell conversion triple trees but they are pricey.

 

[Lectriceye]

Pictures save a lot of words

 

[Lectriceye]

No build threads in your sig, so i don't know what you're working with, bike wise.

220mm rotors have a massive amount of leverage vs 160mm. What are your disc brake interfaces rated at? There will be a limit suggested by the manufacturer, which is based on the underlying strength of what it connects to. A 200mm rotor would be dangerous to operate on such an interface. A 220mm rotor, even more dangerous.

I live in an extremely mountainous area. We have protracted 5-20% grades all over the place. I use very strong regen in place of a rear mechanical brake, and the primary benefit is that my rear brake doesn't fade. That means i don't need oversized rotors in order to add thermal mass.

Going down these mountains with a BBS02 and dual 200mm mechanical brakes was terrifying; same with beefy rim brakes. Within a mile you'd start to feel major fade. The consequence of heat saturation on the braking medium is for a tire to pop off if you have vbrakes, or a disc brake wadding up. Either failure sends you flying at speed. So i would constantly ride a mile, stop and let the brakes cool, ride a mile, etc..

My car also has brake fade going down the mountain but nowhere near as severe.


But this is no problem with a big hub motor doling out >1kw of regen braking power. Braking is predictable and consistent. The rear is doing most of the work, so front disc fade is now a non issue. The fact that i'm getting large amounts of energy back into the battery is the icing on the cake.

Thanks for your insight and comments. Since the rotors need replacing I will probably go ahead and put on 2 200/203mm rotors and start looking for a regen solution for the rear hub this winter.

 

[Lectriceye]

Have you already tried the finned brake pads?

No I haven't tried, but do you have a specific brand/model in mind?

 

[E-HP]

No I haven't tried, but do you have a specific brand/model in mind?

I’ve only seen reviews on the Shimano pads, but there’s probably others. I go through too many pads to get expensive ones. I have floating 203mm rotors front and back, and cheap 4 piston calipers, but I get noticeable fade during some long steep decent. I know right away if I need to change my pads before my next ride.

 

[Mongo]

Pictures save a lot of words

The front looks rotor/caliper pad alignment reasonable to me, not knowing the width of the pad compared to the corresponding rotor sweep area. Not so on the back, where my first guess would be the caliper is spaced too high (edit: too far out radially). I use a bright flashlight when setting up the disc caliper height.

 

[Lectriceye]

The front looks rotor/caliper pad alignment reasonable to me, not knowing the width of the pad compared to the corresponding rotor sweep area. Not so on the back, where my first guess would be the caliper is spaced too high. I use a bright flashlight when setting up the disc caliper height.

I guessed "aluminum frame" based on this picture you posted elsewhere (speaking of pictures), based on the top/down tube welds along with the rectangular chain stays:

Thanks Mongo, I will look closely at the rear caliper positioning when I get into changing the rotors.

 

[classicalgas]

I have 180mm rotors on front and rear with 160mm caliper posts, which are not adequate for my weight and the long steep decents that I ride regularly. General informations says I should increase the rotor size, which will require a different adapter than the 20mm now in place. The choices of adapters seem pretty standard when going to 200mm rotors but not much information when going to 220mm rotors on 160mm posts (+60mm). Wondering if anyone has done this, was the transition successfully, and what adapters are available? It looks easy to go to 200mm rotors, but I don't want do that and then discover It wasn't enough, and have to do it again.

Extra thick "e-bike" rotors are available, and add both heat capacity ( "thermal mass" ) and resistance to buckling, without the problems with extra load on the forks that come with larger diameter rotors. I've tried both, and for Ebike use, the thicker rotors do more for effectiveness on downhills than larger ones do. Also, look for rotors with more surface area (less slots/hole) in the pad track.

 

[E-HP]

Not so on the back, where my first guess would be the caliper is spaced too high. I use a bright flashlight when setting up the disc caliper height.

Good eye. When mine were off, the brakes would work until one day the suddenly wouldn’t. The pad to pad contact (green and blue arrows) prevented any braking, unlike normal wear where you still have something if you squeeze hard.

The yellow arrows are where there was metal to metal contact with the rotar when the pistons continued to squeeze the pads at an angle.

 

[hillslayer@]

203 mm rotors work noticable better than 180 mm. l ride a similar weight bike but most on the asphalt if I plan on riding steep dirt trails l am taking my mid drive only mountain bike which weighs considerably less. The dual motor is nice on the road but the extra weight is a handful on steep trails.

 

[Lectriceye]

203 mm rotors work noticable better than 180 mm. l ride a similar weight bike but most on the asphalt if I plan on riding steep dirt trails l am taking my mid drive only mountain bike which weighs considerably less. The dual motor is nice on the road but the extra weight is a handful on steep trails.

I get what you are saying especially on the decents. I don't currently have a lighter alternative, though I may have in the future. I rrally like the dual motor capability on the long steep ascents. Going to a 55-60 lb bike still leaves me at close to 280 lbs. I find that it is easier to modify the bike thanto lose 50 lbs. haha.

 

[Lectriceye]

A lot of good information here and a lot to think about. Thanks for all your contributions.

 

[hillslayer@]

I get what you are saying especially on the decents. I don't currently have a lighter alternative, though I may have in the future. I rrally like the dual motor capability on the long steep ascents. Going to a 55-60 lb bike still leaves me at close to 280 lbs. I find that it is easier to modify the bike thanto lose 50 lbs. haha.

Pictures save a lot of words

Your rear caliper is to high maybe when you switch to 203 mm rotors it will line up better.

 

[Lectriceye]

Does anybody have a recommendation for a a set of really good 203's with high heat dissapation and low noise? I read about the Shimano Iceteck I see there are more than one 6 bolt type ranging in price from 50-70 bucks each.

 

[E-HP]

Hmm, not really good. Everything on my bike is cheap, and ok to pretty good. I’ve been using these floating discs for a few years. I just replace them when they get thin. They were $17 the last time I replaced them. Now they’re almost as much as a Big Mac meal !!

https://a.co/d/7EIZj3U

I think noise is more about the pads. For me, semi metallic seem to strike the best balance between noise and stopping power.

 

[Lectriceye]

After a thorough evaluation of the rear brake installation, I determined that the rear adapter for the caliper was reversed. This occured a year ago when a shop (no need to mention names) converted my mechanical brakes to hydrolic, and installed the bolt on adapter incorrectly. Another expensive lesson learned and another payment paid for my education. I will change the rotor and the pads myself. Going to a 203 on the front and staying with 180 on the rear.

 

[hillslayer@]

After a thorough evaluation of the rear brake installation, I determined that the rear adapter for the caliper was reversed. This occured a year ago when a shop (no need to mention names) converted my mechanical brakes to hydrolic, and installed the bolt on adapter incorrectly. Another expensive lesson learned and another payment paid for my education. I will change the rotor and the pads myself. Going to a 203 on the front and staying with 180 on the rear.

If you're packing heavy loads on the back of the bike I would go 203 on the back also, on steep downhills I am dragging the rear brake to control speed bigger rotors shed heat

 

[Lectriceye]

If you're packing heavy loads on the back of the bike I would go 203 on the back also, on steep downhills I am dragging the rear brake to control speed bigger rotors shed heat

Thanks Hillslayer, I did get the 203 installed on the front and I can really tell the difference. I did order a 203 for the rear but won't have it until day after tomorrow. Yes, I do have a lot of weight on the back, me at 220, a 2nd 20ah battery on the back rack for the mid, and sometimes another 17.5ah on the back for my extra long rides.

 

[OCD Garage]

You can buy adapters to run pocket bike calipers on bicycles, that may be an option, lots more pad to rotor contact with that setup and cheaper than a good set of mtb brakes.

 

[Lectriceye]

You can buy adapters to run pocket bike calipers on bicycles, that may be an option, lots more pad to rotor contact with that setup and cheaper than a good set of mtb br

You can buy adapters to run pocket bike calipers on bicycles, that may be an option, lots more pad to rotor contact with that setup and cheaper than a good set of mtb brakes.

Thank for that thought. I am invested in what I have for now, I'll see how it goes and may have to look at that option later.