Shortbow

[tjwilson]

You might be alright with the hydro disc if you don't open up the system. Put something in the caliper, hold it upside down, pump the lever and see what happens.

If you have to remove the hose for any reason you'll have to make sure you have the proper bleed fitting, new ferrules etc. All brands have different parts. It's not universal like car brakes.

I know when I put hydro discs on my bike when I tilted it up to move it around the crowded garage the back brake would go completely slack. They need bled again though.

Hydraulic brakes are a pain in the neck for a Rat build.

I read some of the troubles you had with the brakes on Sting Rat. Sounded like fun

I ended up getting what was called a Shimano "J-kit". The calipers and levers come pre bled and the hose is only attached to the caliper. They offer it as a retrofit option for bikes with internal routing. Not sure if the hoses will be long enough but figured I'd start with as close to completely matched and ready to go components as possible to avoid trouble.

 

[tjwilson]

You don't need to - Hydraulics work in any position you mount them - it's a sealed unit, so the positioning doesn't matter. In most bikes the rear one is almost horizontal, sometimes upside down (worked on a few bikes with that), while on the fork it's almost vertical, or sometimes leaning towards laying upside down (like in my 14 RRB Build-Off).



The bigger & stiffer the disc the better. A friend of mine is running 203mm on his e-bike with 4 piston Magura caliper designed for downhill riding, and that thing has so much stopping power that it bends the fork (But actually it stops his 89lbs bike with him weithing something like 220lbs, from going 32mph in a jiffy). If You're planning on running in speeds less than 19mph a 180 on the front & 160 on the rear might do the trick.

I did do a little looking around to try and find info on caliper orientation. Nothing indicated a problem with being upside down. And like you mention, I've seen front calipers that lean back pretty far. The only thing I did find was that brake *system* was not designed to operate upside down. This was from the Shimano manual. That seems to have to do with the caliper being positioned higher than the lever / fluid reservoir. Apparently any bubbles within the system can migrate from the reservoir to the caliper and cause issues. Might be the problem that @Chad T is having while moving his Sting Rat around?

 

[SpikeFC]

I did do a little looking around to try and find info on caliper orientation. Nothing indicated a problem with being upside down. And like you mention, I've seen front calipers that lean back pretty far. The only thing I did find was that brake *system* was not designed to operate upside down. This was from the Shimano manual. That seems to have to do with the caliper being positioned higher than the lever / fluid reservoir. Apparently any bubbles within the system can migrate from the reservoir to the caliper and cause issues. Might be the problem that @Chad T is having while moving his Sting Rat around?

Rule no. 1

Don't trust all Shimano manuals In one of their manuals it states that Nexus 3speed hubs should run with a cog set of 20-22 rear 38 front, mine is working 16 to 46, the same manual has a line about roller brakes not working with v-brake levers... mine are working fine

Rule no. 2

Not operating upside down means that the lever can't be lower than the caliper, cause it's a gravitational system. Air bubbles always go up the line, and when the whole system is operated upside down they gather in the caliper instead of the lever (that actually has a small tank for the oil inside it). The working idea is 100% the same as in motorcycle brakes.

Yes, you're right, that is the problem that @Chad T is having. I'm personally thinking that hydraulic brakes are very good for any build - even rat builds, you just need to remember to bleed them properly and make sure that you have not worn or greasy pads. That can lead to catastrophes.

Since hydraulic brakes are used in almost every new bicycle, I have a lot to do with those systems, and from my experience - don't use cheap hydraulic kits, and avoid using other producers than Tektro, Magura & Shimano, cause replacement parts to other producers brakes (like Avid or Formula) may be super hard to find.

 

[tjwilson]

Overview and Details with Seat Stays / Cantilever Tubes

Page 5 needs some images...

Finished up the filing of the canti-tube welds. Still need to get a bridge made up to connect the two sides.

Clearance around the chain stays, the chain and tire is tight. Looks workable but there may be some chain rub on the chain stays in tenth gear. Might call for a rub guard?

 

[OddJob]

TJ, to take up some of the slack in your high gear, and maybe alleviate any chain rub, check the B screw on the back of the rear derailleur. If you turn it in (to the right, clockwise) about half way, it will tension the chain a bit more.

This will also keep it from rubbing on the upper pulley wheel in first gear. So a double benefit.

Most of the time, these derailleurs come with that B screw nearly all the way out. It really helps with a more crisp shifting between the cogs. I usually pull the der cage back towards me to take the spring load off the screw and then turn it in 5 or 6 rotations of my wrist.

The other thing to do is keep the chain as short as possible, so it is the least slack it can be when in high gear.

Here's a pretty good Youtube on the adjustment:

 

[GuitarlCarl]

Yep adjust that derailleur a bit
and maybe a strategic dimple on the inside of the tube...

 

[tjwilson]

TJ, to take up some of the slack in your high gear, and maybe alleviate any chain rub, check the B screw on the back of the rear derailleur. If you turn it in (to the right, clockwise) about half way, it will tension the chain a bit more.

This will also keep it from rubbing on the upper pulley wheel in first gear. So a double benefit.

Most of the time, these derailleurs come with that B screw nearly all the way out. It really helps with a more crisp shifting between the cogs. I usually pull the der cage back towards me to take the spring load off the screw and then turn it in 5 or 6 rotations of my wrist.

The other thing to do is keep the chain as short as possible, so it is the least slack it can be when in high gear.

Here's a pretty good Youtube on the adjustment:

Awesome info, thanks. I saw the screw but had no idea what it adjusted or how it should be adjusted. The derailleur came out of the box with the screw about half way in. I shortened the chain according to the manual... chain around the front chainring and the largest rear sprocket (without derailleur) plus two links. These images are with that initial screw setting and after chain shortening. It was difficult to run through the gears because I didn't have the bike fixtured and it's not ready to ride but it seemed to shift fine. After watching the video I'm wondering if I've got the chain too short / tight?

Tenth Gear

First Gear

 

[tjwilson]

Yep adjust that derailleur a bit
and maybe a strategic dimple on the inside of the tube...

Those poor chain stays, in the gun sights again

 

[OddJob]

TJ, since you don't have a front derailleur, that position in 1st gear is fine. Especially with that short cage der in the rear, you want a shorter chain when you are down in 10th / high gear. otherwise it will rub against the pulleys between the two.

 

[tjwilson]

TJ, since you don't have a front derailleur, that position in 1st gear is fine. Especially with that short cage der in the rear, you want a shorter chain when you are down in 10th / high gear. otherwise it will rub against the pulleys between the two.

Thanks for your help and input. Much appreciated and gives me confidence with this new to me hardware

 

[Chad T]

OJ knows his stuff. He's my secret weapon when I get into trouble.

Chain clearance looks good. Will probably slap the stay while you're shifting. Does it clear the tire in first? That's the problem I always run into with a wide tire.

 

[tjwilson]

OJ knows his stuff. He's my secret weapon when I get into trouble.

Chain clearance looks good. Will probably slap the stay while you're shifting. Does it clear the tire in first? That's the problem I always run into with a wide tire.

It clears but just barely. There might be a little rubbing of the bottom of the chain (return run from the cog to the chain ring) if there’s much movement side to side. Top seems good. Considering the speed I’d be traveling while using first, and how infrequent that will be, I don’t think it will be an issue. Easy to say now... a few test rides will prove if my assumption is true real fast.

 

[tjwilson]

Sissy Bar / Seat Support

Not sure if they're called a sissy bar only if they're tall and seat support if they're short. Anyway, started with the bottom supports. These will eventually be cleaned up and polished.

Fill with sand, tack weld, bend, cut free, rotate 90°, tack, bend again.

Test fit. I did think briefly about leaving them long but ultimately decided against it.

I added the additional bends at the bottom of the tubes to keep the seat from getting too wide. The final seat width should be about the width of a typical banana seat.

Fairly certain this is NOT the recommended way to use a pipe bender.

I couldn't get the complete bend I wanted from a single piece of tubing. Took three pieces sleeved together to get the curve I wanted.

Support sides trimmed short and top curve dry fit.

 

[tjwilson]

Rear Brake Revisited

With the seat support in place I was able to take a closer look at the rear caliper mount. Using the 160mm disc there seems to be enough room to mount the caliper in a more "traditional" position. I'm just not sure about the hose routing. With the caliper upside down and flipped inside out the routing is really clean. I'm second guessing if that could actually be pulled off though. The bracket would have a lot of twist leverage.

140mm Disc (Lack of) Clearance

160mm Disc Clearance

Hose Routing

 

[Scrap Wolf]

It is such a joy to follow this build. First of all the fabrication skills are a lust for the eye. Second, all the work is so well documented in image and text. This takes a lot of time, I really appreciate it.


Sent from my iPhone using Tapatalk Pro

 

[Chad T]

Can't wait to see this with the nanner and apes.

You could route the hose behind the wide section of the sissy and attach it to the seat stay to clean it up a bit. Should be able to bend the hose quite a bit so long as you don't kink it or pinch it shut.

 

[tjwilson]

It is such a joy to follow this build. First of all the fabrication skills are a lust for the eye. Second, all the work is so well documented in image and text. This takes a lot of time, I really appreciate it.


Sent from my iPhone using Tapatalk Pro

That’s an awesome compliment, thank you very much.

 

[tjwilson]

Can't wait to see this with the nanner and apes.

I can’t either!

You could route the hose behind the wide section of the sissy and attach it to the seat stay to clean it up a bit. Should be able to bend the hose quite a bit so long as you don't kink it or pinch it shut.

Something you just said there flipped a switch to a dim little light in my head! These are hydraulic brakes. Aren’t automotive hydraulic brake systems made up of both flexible and hard lines? I wonder if they sell or, if it would be possible to make, hard lines that would connect to a bike hydraulic brake system. Even just an angled fitting attached to the caliper would completely change the hose routing. Something like a v-brake noodle.

 

[MattiThundrrr]

Steel braided lines would be MAD SICK!!

 

[kingfish254]

WOW! What an absolutely mind blowing design. Your work is some of the best around. Love it man!