Mechanical Front Disk Caliper

[Joe Riel]

The adjustment screw for the left pad of the front brake of my V20C does not turn. Am thinking the simple solution is to replace the caliper. Any recommendations for a suitable replacement? Would rather not deal with hydraulics. The mounting screw separation is 34 mm. Is that post-mount or flat-mount (I've seen conflicting data)?

Thanks,

Joe

 

[Greg S]

I have flat mount GrowTac Equals on my V20c and they’re excellent.

 

[Rolling Along]

On my V20c, I replaced the rear stock brake (Riderever) with a TRP Spyre SLC Mechanical Disc Brake (Flat Mount). I was able to reuse the adapter on the rear. There is no adapter on the front brake. This brake is more budget friendly compared to the GrowTac Equals, but I would read reviews on either brake before purchasing. The TRP is working fine for me after 6 months or about 2500 miles of use.

 

[Rolling Along]

Oh, I skipped the part where you said the left pad does not turn. Have you ever turned it (most likely tighten)? The brakes get dirty real quick and easy. The dirt can make its way in and hard to turn. You may want to try cleaning first. If not better, try taking the cover off, removing the pads and cleaning. I ended up taking my rear Riderever apart and realized it would better to replace it as it did not have good closing action, even when clean.

 

[Joe Riel]

Oh, I skipped the part where you said the left pad does not turn. Have you ever turned it (most likely tighten)? The brakes get dirty real quick and easy. The dirt can make its way in and hard to turn. You may want to try cleaning first. If not better, try taking the cover off, removing the pads and cleaning. I ended up taking my rear Riderever apart and realized it would better to replace it as it did not have good closing action, even when clean.

I removed the caliper and took it partially apart, but not enough to see what prevented the adjustment screw from turning. It wasn't clear how to disassemble that part, and was worried that I'd end up with an unusable brake. Would dirt prevent the adjustment screw from being tightened? It makes sense that dirt would affect the normal operation, but why the adjustment? I doubt I had used it (the Riderever) for more than a few hundred miles.

 

[Rolling Along]

Assuming you cannot tighten the adjustment screw, my best guess is that it is unscrewed as far as it can go and is simply stuck. I took apart one side of my Riderever brake - I don't recommend doing that because there is a spring and it is hard to put back together. Also there is a small plastic part where it says "Pad in" that can break off - not shown as broken in photo. (The tiny circle with the writing can break off.)

I took some photos to help visualize. First photo is of parts with side removed. Second is photo of tightening all the way. The inner drum of brake pushes in towards the center. The third photo is just another angle with it tightened all the way in (the drum and silver part it is inside of slid over because the whole side is removed). When unscrewed all the way the inner drum is flat against the wall it comes out of.

 

[Joe Riel]

Assuming you cannot tighten the adjustment screw, my best guess is that it is unscrewed as far as it can go and is simply stuck. I took apart one side of my Riderever brake - I don't recommend doing that because there is a spring and it is hard to put back together. Also there is a small plastic part where it says "Pad in" that can break off - not shown as broken in photo. (The tiny circle with the writing can break off.)

I took some photos to help visualize. First photo is of parts with side removed. Second is photo of tightening all the way. The inner drum of brake pushes in towards the center. The third photo is just another angle with it tightened all the way in (the drum and silver part it is inside of slid over because the whole side is removed). When unscrewed all the way the inner drum is flat against the wall it comes out of.

Thanks for the photos. Just to clarify, there are two adjustment screws, one on the inside (have to put the 2mm allen key through the spokes to turn it) and one on the outside (easy to get it to). The inside screw turns easily, so I can adjust that pad. The outside screw does turn, maybe 10 degrees, either clockwise or counterclockwise, but hits a hard stop (either way). I can see the brake pad; but there is no movement of it when turning adjustment screw.

 

[Rolling Along]

I think what I have called "inner drum" is called the piston. Yes, there is a piston on each side of the brake, each with its own adjustment screw.

So your "outside" adjustment screw is turning, but it should turn a lot more than 10 degrees! You may be able to see the piston move with the little adjustment range you have. Seems like the piston is sticking and not sliding like it should. There may be some way to lubricate it so that it slides and works. I can think of soapy water - like dish detergent and water. But if you get water on any metal and it stays there it will rust. Notice the rust on my spring in the first photo - that spring would eventually rust enough and break.

If I remember right, my problem was also where the piston did not slide in/out. But the screw did turn and I could see the drum move. It just did not move enough. So I replaced the brake. My front Riderever brake is still working and I have replaced the brake pads once.

 

[Joe Riel]

When I turn the arm (which the brake cables pulls) both pistons moves. More exactly, the surface of the brake pads moves toward the disk (I can see both of them move), so I assume the pistons are moving. Aren't the pistons effectively large screws threaded into the caliper body, so when turned by the arm, they move towards the disk? What is the adjustment screw supposed to do? How does that tiny screw move the surface of the piston? If your piston did not slide in/out, did the arm turn? I need to find a drawing of the inner parts of the mechanism.

 

[Rolling Along]

Yes, pulling the brake cable moves the arms and the pistons move inward to brake. The adjustment screws do the same - screwed in the piston moves inward; screwed out they move the pistons outward. That's how they adjust the pad position. It's fine tuning with small turns of the screws - like each 1/8 turn. But I just checked on my Riderever brake and the adjustment screw moves the "inner drum" only. The inner drum is the innermost part of the piston. It is part of the piston. You can see that in my second and third photos. Zoom in if you have to.

 

[Rolling Along]

With a new brake the adjustment screws are unscrewed all the way. As the pads wear you screw in by about 1/8 turn each time you have to adjust - hopefully lots of time between adjustments.

 

[Rolling Along]

I just double checked and verified with the side I do not have pulled apart. What is surprising to me is that screwing in the adjustment screw and thus the inner part of the piston seemed to limit the range of the arm. Maybe that is what is wrong with my brake and why I replaced it.

 

[Joe Riel]

Thanks again. From the second photo, it appears that turning the allen key (which appears in the far right) should turn that fairly large screw with a washer-like surface that (presumably) pushes on the (removed) brake pad. That explains how the adjustment should work. That my screw doesn't turn more than 10 degrees is a mystery that I probably won't understand until replacing the caliper and dissecting the old one.

 

[sixty-six]

I've now got Juin tech cable activated hydro calibers on my v20 and partner's bike...work and modulate way better than the TRP I was using before. Also as they're self centring far less faffing around to set up...however I did need to change the front rotor to 180 .

 

[Joe Riel]

I have flat mount GrowTac Equals on my V20c and they’re excellent.

Did you use the two types of cable housing that is provided (I believe) with those brakes?

 

[Greg S]

Did you use the two types of cable housing that is provided (I believe) with those brakes?

I used the compressionless housing.

 

[chicorider]

I initially built my V20c up with TRP Spyre SLCs, and they worked fine. But I eventually moved over to the Growtac Equals, and they are a noticeable improvement in power and lever feel. They're kind of pricey for mechanical brakes, but I like them enough that I now have them on three bikes. I didn't use the included cable kits, preferring the simplicity of Jagwire compressionless housing. I sold the Growtac cable kits on eBay.

 

[Joe Riel]

My GrowTac Equals will be here next week. Do they come with pads? I don't think do, but the seller was also out of GrowTac pads so will use a compatible set.

I haven't tried hard braking on the V20C. Is it possible to lift the rear wheel? Would normally practice lifting the rear wheel on a diamond frame, which is easy to do at low speeds. Does the front wheel skid on a V20C (on clean pavement)?

 

[Greg S]

My GrowTac Equals will be here next week. Do they come with pads? I don't think do, but the seller was also out of GrowTac pads so will use a compatible set.

I haven't tried hard braking on the V20C. Is it possible to lift the rear wheel? Would normally practice lifting the rear wheel on a diamond frame, which is easy to do at low speeds. Does the front wheel skid on a V20C (on clean pavement)?

Mine came with pads.

I don't think it's possible to lift the rear wheel on the V20c. Like you, I do practice panic stops from time to time and have never lifted the back.

 

[Rolling Along]

My TRP Spyre SLC came with new pads that are semi-metallic. The semi-metallic pads are noisier than the organic pads that I have on the Riderever. The semi-metallic pads are supposed to stop better than organic pads. But both seem to stop fine when adjusted right.