Ask the experts

[Dee Hubbs]

Just chiming in to state the obvious, be very, VERY careful overfilling any Shimano system, or you can very easily damage the reservoir bladder. I learned the expensive way that this generally is not repairable. There are a few hacks, but I doubt they work long term?

FYI: Shimano now offer bladder replacements, both MTB and Road.

[rideit]

That’s great info, have you seen an Installation proceedure video?

[jm2e]

Are those little washers that go between SRAM cranks and pedals really necessary? I lost one in transit, is it worth the hassle to replace it?

1) install pedal
2) spin pedal
3) if it’s rubbing against the crank, you need the spacer. If not, you don’t.


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[toast2266]

1) install pedal
2) spin pedal
3) if it’s rubbing against the crank, you need the spacer. If not, you don’t.


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What pedals have <1mm clearance between the pedal and crank arm?

I think the washers are mostly just to keep the aluminum inserts / crank arms from getting bungled up when a steel pedal is tightened into them. Which generally isn't an issue if you're not over tightening the pedals.

Some people act like they're for adjusting q-factor, but I'm entirely skeptical that 99.9% of people can notice that difference.

[Andeh]

Cross-post from RM: I've got a brake question. I've noticed that recently on my brakes (Code RSCs, 200mm HS2 rotors, MTX Gold pads), that after a typical descent where I'm on the brakes a lot, I have to move the rear brake's contact point adjust out 1-2 clicks. It started a few months back, where this would happen every few rides, and it's getting to the point where I find myself doing this nearly every ride. I just bled the brakes last month and while they felt a bit fresher after, it didn't really make the problem go away. Brake bleed was just a standard 2 syringe bleed, not a full flush, but the fluid wasn't super nasty. What's the most likely culprit - needing new pads? I admit I haven't checked the thickness - just eyeballed them and it seems to have enough material left. They're not making any noise or smell, and the rotors are brown not blue. When I bled them, I checked the piston movement and it seemed good. I haven't noticed any signs of fluid loss (oily grime accumulation on the MC or caliper).

My "typical descent" is a trail that starts out flowy and moderate grade where you're on and off the brakes, then gets into a faster steeper section where you're on the brakes most of the time, only letting off in short spurts. It's about 2 minutes long, 575 ft descent. When I brake, I always pull both at the same time, just varying relative front/rear pressure for control.

[toast2266]

Cross-post from RM: I've got a brake question. I've noticed that recently on my brakes (Code RSCs, 200mm HS2 rotors, MTX Gold pads), that after a typical descent where I'm on the brakes a lot, I have to move the rear brake's contact point adjust out 1-2 clicks. It started a few months back, where this would happen every few rides, and it's getting to the point where I find myself doing this nearly every ride. I just bled the brakes last month and while they felt a bit fresher after, it didn't really make the problem go away. Brake bleed was just a standard 2 syringe bleed, not a full flush, but the fluid wasn't super nasty. What's the most likely culprit - needing new pads? I admit I haven't checked the thickness - just eyeballed them and it seems to have enough material left. They're not making any noise or smell, and the rotors are brown not blue. When I bled them, I checked the piston movement and it seemed good. I haven't noticed any signs of fluid loss (oily grime accumulation on the MC or caliper).

My "typical descent" is a trail that starts out flowy and moderate grade where you're on and off the brakes, then gets into a faster steeper section where you're on the brakes most of the time, only letting off in short spurts. It's about 2 minutes long, 575 ft descent. When I brake, I always pull both at the same time, just varying relative front/rear pressure for control.

Moving contact point out, meaning at the bottom of the descent, your lever is pulling closer to the bar than it did at the beginning of the descent?

If it's noticeably different over a 575ft descent, that sounds like there's some air in the system that's making it's presence known when things warm up. I'd re-bleed and do some lever flicking while bleeding.

[Andeh]

Moving contact point out, meaning at the bottom of the descent, your lever is pulling closer to the bar than it did at the beginning of the descent?

If it's noticeably different over a 575ft descent, that sounds like there's some air in the system that's making it's presence known when things warm up. I'd re-bleed and do some lever flicking while bleeding.

Yeah. It's not much but it's enough that the rear stops feeling the same as the front. I'll give them another bleed, maybe try flushing the fluid.

[toast2266]

Yeah. It's not much but it's enough that the rear stops feeling the same as the front. I'll give them another bleed, maybe try flushing the fluid.

If you don't mess with the contact point, does it go back to feeling the same over time?

It could just be the pads wearing down. But I wouldn't expect that to be noticeable over a single short descent.

[Andeh]

If you don't mess with the contact point, does it go back to feeling the same over time?

It could just be the pads wearing down. But I wouldn't expect that to be noticeable over a single short descent.

No, it never goes back to the same. I.E., if I don't touch it at the bottom of the ride, put the bike away in the garage, when I grab it the next day it will feel imbalanced front/rear still.

[Dee Hubbs]

That’s great info, have you seen an Installation proceedure video?

Yes, video is pretty straight forward.
They have 3 diaphragms,
9100 levers
x120 series
And Mechanical Road levers
No Di2 road levers at this point.

The replacement diaphragms are reserved for warranty and must be called in through customer service, Shimano hopes to have them in regular parts ordering soon.

[rideit]

Gracias.

[climberevan]

Here's a Shimano road brake question, since we're on that topic.

My left MC doesn't like to return after pulling it in. I've fully disassembled the MC and the piston is a little worn, but it does seem to move freely in the bore. None of these parts appear to be replaceable. I've tried lubing it and spreading the return springs a little with small success. It's well bled, of course.

My ideas for fixing it are to further spread the springs (with the danger of breaking them) and polishing the piston with 1500 grit or more to remove the scoring. I'm hesitant because replacement shifters seem to be non-existent.

Oh, and this is an Ultegra Di2 shifter, FWIW. It has no bladder from what I can tell--just the reservoir cavity in the hood which leads into the piston chamber.

[jm2e]

What pedals have <1mm clearance between the pedal and crank arm?

I think the washers are mostly just to keep the aluminum inserts / crank arms from getting bungled up when a steel pedal is tightened into them. Which generally isn't an issue if you're not over tightening the pedals.

Some people act like they're for adjusting q-factor, but I'm entirely skeptical that 99.9% of people can notice that difference.

I’m willing to concede. My perspective is from running sram carbon cranks with big inside bearings like the Race Face Atlas and Spank Spike. Since I stopped running those pedals, I haven’t used a pedal washer.


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[jono]

any traction for the idea that its better to replace brake padz before they get too worn down from the POV of lever feel ? ?

I'm a little surprised you haven't made up some aluminium and AQS shims you can just slip in there when the pads are half-worn. Maybe just aluminium.

[XXX-er]

wow it sounds like you have already done this ^^ and are going to share this with everyone

[jono]

I haven't, but reading through a couple pages it does seem pretty doable. Couple shims cut (backing plate shaped) to be held in place between the pads and the pistons and you just put them in when the pads thin a bit.

I haven't done that because I'm mostly wearing out Maguras, and they can scrape off all the pad material--if you do that overfill trick. But I'd rather add shims and then not have to take the fluid out when it's time for new pads.

Thanks, I think you convinced me!

[summit]

I would think shimming would reduce heat transfer for better or worse. Magura pads are expensive... but...

TruckerCo pads are so cheap that they make a good argument for not shimming/bleeding, but just rather swapping pads early.

You could even buy 4packs and collect the half worn pads and then after half wearing them all, do an overfill and cycle the pads back through. This is my current plan.

Today I'm frustrated because I barb/olived and did the perfect bleed on my Magura so I could take the XTs off. I'm now 99% sure the barb olive kit was wrong because fluid is coming out of the lever. The barb/olive came with an offbrand bleed kit from amazon that otherwise was great. Today I have to hunt down Magura barb/olive from local shops. Grrrr....

[jono]

I don't believe I've ever seen a brake caliper that was designed to increase heat transfer from pads to fluid. For good reason, in all the cases I'm familiar with, but I can see other approaches being possible.

I did quickly drop the idea of making aluminum shims for Maguras, though: the magnetic connection between piston and pad is way too good to mess up. The right answer appears to be plated steel washers.

[toast2266]

You could get some hope v4 rotors. Those things are around .5mm thicker than regular rotors.

Might need to file down your caliper a bit to get them to fit though.

[summit]

Today I'm frustrated because I barb/olived and did the perfect bleed on my Magura so I could take the XTs off. I'm now 99% sure the barb olive kit was wrong because fluid is coming out of the lever. The barb/olive came with an offbrand bleed kit from amazon that otherwise was great. Today I have to hunt down Magura barb/olive from local shops. Grrrr....

Guess it was right and I just needed to torque more and do one more bleed.

BTW this is the Magura bleeding method I use... it works great:



It also gives the method to adjust piston position.

[El Chupacabra]

Hey experts: Q on a crank/BB issue:

I am installing a SRAM GXP BB into a 73mm threaded mountain bike frame, and using a TruVativ Descendant carbon GXP crankset. Per instructions found online, I did not use any spacers between the BB and the BB shell on the bike. There is a dust cover over the BB bearing on each side.

Issue: when I torque down the crank to spec, it seems like it is side loading the BB bearings excessively - the crank arms spin in a loping sort of fashion, and there seems to be extra resistance (though not excessive) to spinning. Do I need to add a spacer between the BB and the BB shell? If so, to which side? Guessing non drive side so as not to mess with chainline.

[Whiteroom_Guardian]

27in tires? My girlfriend has this silly old schwinn townie bike with 27in wheels/tires. Looking for new tires that are better than pure slicks. Not many options that I have found. Universal Cycles has a couple that would work.

[toast2266]

Hey experts: Q on a crank/BB issue:

I am installing a SRAM GXP BB into a 73mm threaded mountain bike frame, and using a TruVativ Descendant carbon GXP crankset. Per instructions found online, I did not use any spacers between the BB and the BB shell on the bike. There is a dust cover over the BB bearing on each side.

Issue: when I torque down the crank to spec, it seems like it is side loading the BB bearings excessively - the crank arms spin in a loping sort of fashion, and there seems to be extra resistance (though not excessive) to spinning. Do I need to add a spacer between the BB and the BB shell? If so, to which side? Guessing non drive side so as not to mess with chainline.

Sounds like something is too tight. Do those cranks have a preload adjuster on the non-drive side? If so, back it all the way off, tap the drive side crank with a rubber mallet just to set the cranks all the way over to the non-drive side, then hand tighten the preload adjuster so it makes solid contact, but isn't exerting much pressure on the bearing.

[summit]

Finding a shop with a Shimano direct mount chain ring tool is more of a challenge than I thought... 0/4

[toast2266]

Finding a shop with a Shimano direct mount chain ring tool is more of a challenge than I thought... 0/4

I tried to buy one of those a year ago. Gave up.