Brake Rub Cost me a Sub 5 IM 70.3 Twice

Triathlon Forum
1

I launched a bottle over some tracks at an HIM that bounced off the pavement and bent my rotor on my disc wheel.

I didn’t realize it was bent and raced IM 70.3 NC going within 1:40 of my goal. The next race I realized the rub at bike check. Ffs… I go to Trek in Chatty where they re-align the wheel. I had a horrible race so it was a non-factor essentially

Fast forward to Augusta Sunday. I miss my goal by 2 minutes. The bike is fine upon getting to Augusta post travel. I go to bike check in and it’s out of alignment again. Ffs… I re-align it and it’s not rubbing. Took me forever to get it adjusted in the heat outside on the bike racks.

Post race my wife says spin it. I did and what do you know it’s rubbing again. Not being super salt with bike tech I realize upon getting home the rotor blade doesn’t seen to rotate evenly moving side to side.

I also realized my power was only 7 watts higher than my wife whom I outweigh by 20+lbs. Wtf… I read a slight rub could have cost me 10 to 30 watts. I’d estimate this for sure, which could be 1 to 2 mph.

At 0.7mph I would have lost 4 minutes. Fortunately I’m going to a bike mechanic this weekend to look at it, but honestly I’m sick thinking about it.

The good thing is once fixed I should regularly come in at my goal consistently. It’s hard not to think this cost me, but at least it won’t moving forward.

2

I also realized my power was only 7 watts higher than my wife whom I outweigh by 20+lbs. Wtf… I read a slight rub could have cost me 10 to 30 watts.Your power would not be affected by a brake rub. A crank, pedal, or hub PM would show your actual power that you are producing. However, some of that power would be going to heat in the brake rub versus to the road in speed. So, if your power was only 7 watts higher than your wife, that is what you probably actually rode.

3

The rotor rubbing on the brake pads would increase your power numbers not decrease them. Increased resistance = more power needed to overcome said resistance.

Once a rotor is bent if can be very difficult to get it to stay straight again. As it heats up and cools down it can slightly warp enough to rub. It may take a few rides after each tweak to the rotor to get it right.

If you couldn’t hear the rub while riding, it likely did not cost you more than a few seconds.

4

How could it be OK before the race but not after ? Did you get to ride the bike around the block, use the brakes, and confirm it was all OK before the last race ? Or just not have the time ? (Do you KNOW if was defo fine before the last race ?)

A few questions / things to check out:-

Front wheel or back wheel ? (You say disc wheel - but not sure if you mean a disc wheel or a wheel with a brake disc. Obvs could be a disc wheel with a brake disc !)

Is the rotor bent ? Or just not seated properly on the hub?
Is is loose ? Centre lock ring tight ?) or IS 6 bolt - again all bolts tight, no debris in the disc/hub interface ?

What exactly did Trek ‘re-align’ ? And how ? Wheel in the drop out ? Re-align the caliper ? Try to straighten a better rotor ? Or something else.

Is the caliper and any adaptor brackets tightened properly ? (Ie is it the caliper shifting to go from OK to rubbing).

Or is the wheel shifting in the dropouts ? (Traditional 9mm QR ? Or ‘bolt through’ ?)

Or is it a combo of all the above + a piston sticking a bit and not retracting fully after a hard bit of braking ?

(I’m also assuming this is hydraulic and not cable operated. Otherwise sticky cables ? Cable actuated disc calipers are often shit - many only actualte in 1 side and rely on deflecting the rotor towards the other pad to work - which is just a shiiite lazy nasty cheap design).

Also i think the Shimano ice tech rotors seem renown for warping. I run disc brakes on 4 bikes (2x mtb, 1x Road, 1x gravel). But none with icetech. Just straight stainless steel rotors, or SS braking surface with ‘floating’ centre. Not many problems with them providing I keen them reasonably clean - just some annoying ‘ching ching ching’ or brake squeal if they get too cacked up with dust / dirt.

5

The rotor rubbing on the brake pads would increase your power numbers not decrease them. Increased resistance = more power needed to overcome said resistance.

Once a rotor is bent if can be very difficult to get it to stay straight again. As it heats up and cools down it can slightly warp enough to rub. It may take a few rides after each tweak to the rotor to get it right.

If you couldn’t hear the rub while riding, it likely did not cost you more than a few seconds.

Yeah, this.

The cost of these bikes with hydro discs if it rubs and loosening the two caliper bolts and squeezing and tightening while centered doesn’t get it…just install a new rotor.

And on disc brakes the loss isn’t that much unless that sucker is straight up singing to you.

6

The power number came from my Garmin 745 watch as I don’t have a power meter. It was estimated by a Garmin watch. Probably not accurate whatsoever. I use Zwift inside but some Favero Assioma’s would be a good future purchase.

7

The caliper adaptor brackets were checked and tight. The lock ring could be checked but I’m pretty sure it’s a bent rotor.

I’m in agreement a total rotor replacement is likely the smartest solution on my rear disc wheel. It would correct it long term.

I wonder about the integrity of pads as well. I noticed a ring of black dirt around the rotor post race. The rub was certainly there.

8

The rotor rubbing on the brake pads would increase your power numbers not decrease them. Increased resistance = more power needed to overcome said resistance.

Once a rotor is bent if can be very difficult to get it to stay straight again. As it heats up and cools down it can slightly warp enough to rub. It may take a few rides after each tweak to the rotor to get it right.

If you couldn’t hear the rub while riding, it likely did not cost you more than a few seconds.

Yeah, this.

The cost of these bikes with hydro discs if it rubs and loosening the two caliper bolts and squeezing and tightening while centered doesn’t get it…just install a new rotor.

And on disc brakes the loss isn’t that much unless that sucker is straight up singing to you.

Makes me wonder about the loss of power, since my FTP in training was 55 watts higher than my wife’s. She felt sluggish on the bike and my legs felt responsive.

I’m pretty confident this is a much bigger loss than believed. Perhaps I’m wrong though.

9

The power number came from my Garmin 745 watch as I don’t have a power meter. It was estimated by a Garmin watch. Probably not accurate whatsoever.Aah, then yes that would show up in the guesstimated power. Garmin just uses speed & elevation plus assumptions about total weight and drag coefficients to calculate power (and maybe wind, but I doubt it).

10

So you’re thinking the estimated power would have accounted for the brake rub? I’m thinking it would have skewed the estimated power without accounting for it.

11

So you’re thinking the estimated power would have accounted for the brake rub? I’m thinking it would have skewed the estimated power without accounting for it.I probably did not word it very well… With a true power meter, you would know your actual power, no matter what. But with a rubbing brake you would have gone slower while producing your normal power.

With estimated power, Garmin assumes a mechanical efficiency factor to account for things like rolling resistance, drivetrain loss, etc. (in addition to its assumptions about drag, weight, and maybe wind). So, in your case with brake rub, your actual mechanical efficiency would be much worse than the Garmin assumption; therefore it would lower your estimated power because you would have been going slower therefore Garmin would assume you were producing less power.

So yes, the difference between your reduced estimated power on this ride compared to estimated power of another ride without brake rub at a similar speed and elevation profile, is in the ballpark of the power loss from the brake rub.

12

Thanks for providing a very clear explanation, confirming what I was originally thinking. Given you could hear the rub and see the line of dirt along the rotor. It makes me wonder how big of an impact this had? Over 56 miles it had to be substantial especially torque on climbs. Not to mention running on legs that worked against the brakes.

Do you think the brake pads are toast too? Three races of doing this. I think a straight rotor replacment at a minimum.

13

In our place, we only had one disc brake road bike that my wife owned and we sold it for those same reasons, we got fed up of constantly having to align the thing This was 2017 technology, but I recall that a single pot hole hit will make it rub again, and it is just not worth around here as most of the roads are rolling or flat. Haven’t bothered with the technology ever since.

14

I launched a bottle over some tracks at an HIM that bounced off the pavement and bent my rotor on my disc wheel.

I didn’t realize it was bent and raced IM 70.3 NC going within 1:40 of my goal. The next race I realized the rub at bike check. Ffs… I go to Trek in Chatty where they re-align the wheel. I had a horrible race so it was a non-factor essentially

Fast forward to Augusta Sunday. I miss my goal by 2 minutes. The bike is fine upon getting to Augusta post travel. I go to bike check in and it’s out of alignment again. Ffs… I re-align it and it’s not rubbing. Took me forever to get it adjusted in the heat outside on the bike racks.

Post race my wife says spin it. I did and what do you know it’s rubbing again. Not being super salt with bike tech I realize upon getting home the rotor blade doesn’t seen to rotate evenly moving side to side.

I also realized my power was only 7 watts higher than my wife whom I outweigh by 20+lbs. Wtf… I read a slight rub could have cost me 10 to 30 watts. I’d estimate this for sure, which could be 1 to 2 mph.

At 0.7mph I would have lost 4 minutes. Fortunately I’m going to a bike mechanic this weekend to look at it, but honestly I’m sick thinking about it.

The good thing is once fixed I should regularly come in at my goal consistently. It’s hard not to think this cost me, but at least it won’t moving forward.

Things happen in race conditions - like when a banana skin was launched into the air and landed in my drivetrain!

You didn’t hit your goal because you couldn’t on the day(s), if you’d been fitter you could have overcome it.

There will always be should have, could have, would have.

But I’m sure you will next time and wish you all the best!

15

I would replace pads and rotors, just to be safe. It sounds from your OP that the rotor may be bent anyway. And yeah, three races could have put a lot of wear on the pads. So, a perfect fresh start should be the surest plan to get everything aligned.

16

Nothing wrong with single sided actuation, Takes a little bit more regular adjustment but mechanically much simpler with less to go wrong. I’ve found their durability to be much longer than double sided. Even have some hydraulic single sided brakes and they work fine. Very easy to adjust for rotor rub, They have their limits but you’re unlikely to find those on a tri bike. When double-sided go wrong they can be very tricky to fix.

17

I launched a bottle over some tracks at an HIM that bounced off the pavement and bent my rotor on my disc wheel.

I didn’t realize it was bent and raced IM 70.3 NC going within 1:40 of my goal. The next race I realized the rub at bike check. Ffs… I go to Trek in Chatty where they re-align the wheel. I had a horrible race so it was a non-factor essentially

Fast forward to Augusta Sunday. I miss my goal by 2 minutes. The bike is fine upon getting to Augusta post travel. I go to bike check in and it’s out of alignment again. Ffs… I re-align it and it’s not rubbing. Took me forever to get it adjusted in the heat outside on the bike racks.

Post race my wife says spin it. I did and what do you know it’s rubbing again. Not being super salt with bike tech I realize upon getting home the rotor blade doesn’t seen to rotate evenly moving side to side.

I also realized my power was only 7 watts higher than my wife whom I outweigh by 20+lbs. Wtf… I read a slight rub could have cost me 10 to 30 watts. I’d estimate this for sure, which could be 1 to 2 mph.

At 0.7mph I would have lost 4 minutes. Fortunately I’m going to a bike mechanic this weekend to look at it, but honestly I’m sick thinking about it.

The good thing is once fixed I should regularly come in at my goal consistently. It’s hard not to think this cost me, but at least it won’t moving forward.

Things happen in race conditions - like when a banana skin was launched into the air and landed in my drivetrain!

You didn’t hit your goal because you couldn’t on the day(s), if you’d been fitter you could have overcome it.

There will always be should have, could have, would have.

But I’m sure you will next time and wish you all the best!

Hard to quantify the extent of the mechanical on performance, but one thing is certain there was an effect.

I came into the race very strong and felt good on the day. I believe the brake rub had a big impact. We’re not talking about a dirty chain.

18

When you spun the wheel, how many times did it spin before it stopped? If only a couple then yup, that brake rub will have cost you.

19

If you’re running 160mm rotor you could try moving to 140 mm. Smaller rotor has a bit more margin for alignment and will be a bit stiffer. Has worked for me on a cx bike with mysterious random rub. Also, a heavier rotor will be more immune to deformation. Magura even make 2.0 mm thick (vs standard 1.8 mm) and I have had very little rub using these. Some of the road-specific rotors are a little over-engineered and switching to a MTB rotor can help.

20

Basically not many turns before full stop. Pre-race I was able to align it so that it wasn’t contacting and was in utter disbelief the wheel was moving forward on its own without being spun. This was in no way the case once it went off track. I’m disgusted thinking this was happening.