alias5000

Hi all,
I have a gravel bike with TRP Spyre mechanical disc brakes and Tiagra 4700 STI levers. The levers feel fairly stiff and I need a lot of hand force to getting close to locking up the rear tire (as a reference point, not saying that that capability is the desired outcome). I would like a bit more power for emergency stops, it's not quite enough, especially not when pulling my kids trailer with live load.

For reference, this is what I have done so far (and am close to being out of ideas):

• New, full-length, compressionless housing, high-quality housing caps
• New polished inner cables
• New high quality pads (confirmed braking power improvement), sanded and cleaned the rotors.
• Caliper arms set up with little pretension

I have more pad clearance to play with than with many other mechanical brake setups. So it really feels to me that Tiagra 4700 pulls more cable than the Spyre were designed for. Where can I find source data, and how can I get out of this situation?
The only other thought I have is to start using a 180mm rotor (but that won't work on the front because of fork ratings). I'm trying to avoid a conversion to hydraulic because of cost (Tiagra ST-4720 levers + calipers are EXPENSIVE!)

Thanks,
alias5000

FBinNY 

If I'm reading you correctly, you already have more leverage that a non-mixed brake, not less. Leverage and travel are opposite ends of the spectrum. Pulling more cable (greater lever movement) means greater leverage and should mean more stopping power. The only problem is that given hand limit the design of levers, and more travel means less clearance when open, so can be a problem with warped rotors.

It could be that the pads and rotors are not bedded together well. Consider doing a bedding ride with a series of longish braking intervals separated with a cooling rest. (ride up and down a medium grade slope a few cycles)

alias5000

Thank you. The pads are bedded in, I did the bedding in rides and had plenty of hard braking since.

What I'm trying to describe is that when open, I have a significant amount of pad spacing, not very little. I have plenty of brake lever movement range available for brake actuation - opposite of running out of lever range.

So, I think it's opposite to what you were describing

csport

I am a heavy rider, and for me upgrading TRP Spyres to cable actuated hydraulic Juin Tech R1's made a huge difference. FWIW I run Sora 3503 levers and Jagwire Pro compressionless housing, this setup is similar to yours.

FBinNY 

OK, so a quick analogy so you know where I'm going. Imagine you're hanging from a rope tied to the hands of a tower clock. At noon and six the hand won't move no matter how you hard you pull the rope. As you approach 3 or 9 you reach peak leverage, with everything in between being less.

So, now (if you can see it) look at the brake's cable actuating arm at the point the pads are engaged. (close lever and tie it so you can focus on the caliper). I suspect that it's now comparable to the clock's hand having over traveled and now nearing 5 O'clock.

If so, the fix is fairly easy. Reposition the brake (shim if needed) so the moving pad is close to the rotor with the cable fully slack, Then adjust the fixed pad to proper minimum clearance, rather than taking up cable with the adjuster. From there it's just some fine tuning. The brake should now work so that the arm is closer to 3 o'clock (90 degrees to cable's line of motion) and you'll get maximum leverage at the point of brake engagement.

tyrion

Bigger rotors give you more leverage, if your frame can accommodate them.

Rolla

On Spyre brakes, both pads move; neither is fixed.

alias5000

Thank you. That makes it very easy to follow. Will try that - and as pointed out, on spyres is should even be simpler as both pads actuate.

Also thank you for the Juintech pointer!

alcjphil

Read the first post again. The OP's fork cannot accommodate a larger rotor

alcjphil

I think that this is probably your situation. Shimano in its wisdom decided to redesign its mechanical brakes a couple of generations ago. Their newer road brake levers pull more cable for a given amount of brake lever travel thus reducing mechanical advantage. I simply don't know if your brake callipers are designed to account for that reduced mechanical advantage. Shimano's rim brake callipers are made to work with this new system which I believe is called "super slr" if memory serves. From what I hear, brake levers and rim brake callipers that share that newer system work superbly well together but this does pose problems when aftermarket suppliers come into the picture. Specking a bike is an art, and companies that place orders from various manufacturers don't always get it right.
Perhaps in your case the Spyke mountain bike version might work better. You would only need one if your rear braking is adequate

IPassGas

Many good suggestions above and you should pursue those recommendations. If you decide you still need something better the following may be helpful.

In addition to large cantilever brakes, we have a rear TRP spyre on our tandem (200 mm rotor on a Rohloff IGH). We tour with camping gear, so overall the bike is heavy (470 lbs w/gear). I was not sure but I suspected the spyre was lacking. On a tandem with 3 brakes we have the luxury of testing brake strength independently. Perhaps not surprising, given the smaller pad area and smaller disc radius vs rim, the breaking power of the spyre was poor relative to a cantilever. I did not wish to use hydraulics on a touring bike, so I decided to try a Paul Klamper brake.The Klamper brake is beefier, without plastic internal components. The lack of plastics is also important if the brake becomes hot. On a 15% slope the Klamper brake was noticeably better than the Spyre in slowing us. My suspicion is that the force your hand puts into the caliper can cause the internals of the Spyre to flex more than the Klamper and so a significant amount of your hand force goes to flexing stuff. This would be an expensive experiment for you, since the Klamper is pricey. However, it is of high quality and can be easily broken apart to clean. Good luck.

alias5000

Okay, got to try this. Turned out that incidentally I was already fairly close to this point, but there was room to improve. I also played around with the point on the lever at which contact is made (i.e., lever is now closer to the bar when engaging) and there is an incremental improvement. But definitely not enough.

alias5000

Thanks! I have BB7s on our tandem with 203mm rotors. They aren't as nice as hydraulics, but have always been very adequate where overheating is not a concern. I will try the BB7 on this bike, but don't expect wonders.

It looks like I'm getting about as much as possible out of the spyres now... Pay $CAD200 to get slightly nicer cable hydraulics (Juin tech R1), pay $CAD400 for 4 piston juin tech gt-p (which review very well and appear to certainly be significantly more powerful), or pay $CAD600 to make the full switch to hydraulic.

I wish it was possible to just test ride the two juins against each other before purchase.

veganbikes

You might try a nicer rotor, the new Magura rotors (MDP and MDC) are quite nice and very stiff which helps. I am unsure if they make them in 160 but I feel like I have seen them but I could be wrong.

csport

I was asking the same question, and I found no evidence that GT-P are much more powerful compared to R1. As far as I understand, GT more often come as GT-F (flat mount), which means they target road bikes and their bigger pads help resist fade on long descents. I would just go full hydraulic instead of GT. For me it was not an option with my 3x9 drivetrain, so I went with R1s.

Video where Path Less Pedaled reviews mechanical disc brakes (Yokozuna Motoko/Ultimo he mentions are rebranded Juin Tech R1/GT).

I think no one mentioned this, but maybe you can try different pads as a last resort?

Thread where I saw people mention Juin Tech which prompted me to upgrade.

HillRider

+1 This is probably the real answer. I'm running Spyres with Tektro R200 road brake levers on my Surly Midnight Special and braking power is quite adequate. Not one-finger easy but at least as good as my older Dura Ace dual pivot calipers with Kool Stop Salmon pads.

Basically those Tiagra levers have given up some leverage and the Spyres were designed to work best with the older cable pull design.

csport

There was an old post saying that TRP Spyres and HY/RD are Super SLR - they are made for the new Shimano cable pull. My Sora 3503 are the new Super SLR, and I am much happier with Juin Tech R1's despite the fact that they use a shorter pull to make them compatible with Campy and older Shimano levers.
Another evidence that TRP brakes are optimized for the new (longer) Shimano pull design is that there exist short pull conversion arms for HY/RD.

Maybe Spyres are just what they are. For me they were lacking stopping power from the hoods.

katsup

Not much more than the Juin Tech GT-P are the Paul Klampers. You may be able to get them from Germany shops such as bike24 for around the same price.

I run Juin Tech R1 (105 R7000 levers) on my drop bar bike and Paul's on my mountain bike. The Paul's are nicer and stop better, but the cost has prevented me from buying more. I haven't ridden Sypre or Juin Tech GT-P. I have ridden BB7 which I think are adequate on a flat bar bike. I didn't like BB7 with a drop bar.

trailangel

tyrion

Incorrect.

He said it won't work because of "fork ratings". My theory is (correct me if I'm wrong you mechanical engineers out there) is that the fork doesn't know what the size of the rotor is, all the fork knows is the torque being put through the brake mounts, and that a wired/mechanical 2 piston system on a 180mm rotor probably won't put more torque through the brake mounts than a hydraulic system with a 160mm rotor. If the OP doesn't feel like he's getting enough braking power then he's probably not close to stressing the fork over it's designed specs.

alias5000

alias5000

Interesting thought. Looking at the fork, clearance with the fork leg might be an issue with a 180mm rotor, unfortunately

FBinNY 

You're mostly right.

First of all the maximum braking force is determined by rider weight and geometry. Specifically the angle of the line from the contact patch to the center of gravity. Fork designers have to allow for heavier riders who can position themselves lower and farther back.

There has to be plenty of fudge room here because of the unknowns. Moreover, fork makers have to allow for the high forces from impacts like potholes and obstructions. Overall, while disc brakes do impose new, different, and higher stresses on fork blades, difference in rotor size isn't a great factor in the scheme of things. Also, larger rotors are easier on forks than smaller ones, as they act more like rim brakes.

That said, there may also be physical space considerations like blade clearance, or the ability to center a caliper.

alias5000

One thing I've seen quoted are suspicions that the caliper mounts are only designed for a certain rotor diameter, as the load on those with growing rotor size and equal caliper increases. I don't know how much this would really be an issue, when following along arguments that you have made above already.

(As for me, this is a gravel bike in urban commuting duty with a carbon fork. Max braking load is probably pulling a loaded child trailer and a few grocery panniers, doing emergency braking.)

Either way, it looks reeeeally tight on my fork to fit a 180mm rotor.

GamblerGORD53

Mine is on my Rohloff with a 203 disc, with resin pads. SA swept bar levers set to long pull. Supposedly wrong. LOL.
It will lock solid instantly. Never squealed once in 5,300 miles. I just don't see how it's possible to screwup the setup. The pad gap is not finicky IME. I do zero to clean but a paper towel wipe thru the pads when the wheel is out.
I have SA drum brakes with both long and short pull. Makes ZERO difference. I suppose it does with poor rim calipers.