front rotor rubbing when out of the saddle on Ostro Vam II

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Noctiluxx
Posts: 1359
Joined: Tue Feb 07, 2017 7:17 pm
Location: Southern California

by Noctiluxx

I have a brand new Ostro Vam II (under 250 miles) with Dura Ace and Black Inc. 58/48 wheels. From day one the front rotor has been rubbing when I put down moderate power out of the saddle. My mechanic thoroughly checked the bike including rotor, axle, brake caliper, thightning everything to spec. And yes he made sure the rotor was straight too. I even tried three other new XTR/Dura Ace rotors and still had the same issue. This morning I even mounted my Bontragel RSL 37 front wheel though the issue still persists.
Wrote to Factor and this was their response.


"What you're seeing move are the pads in the caliper. Remember, they are only secured with a small screw and can move freely within the calipers. This is standard and you'll encounter the same issue with every caliper system in the world due to their design.

Regarding disc rub: it's common to experience slight disc rub under load. You can minimize most of it with some fine-tuning of the alignment, but it's difficult to eliminate entirely. Again, minor rubbing under high load is standard for disc brakes.

Remember, while disc rub might sound loud, the friction has been recorded as low as 2-5 watts, which isn’t a significant obstacle. For comparison, a chain can add 9 watts of drag in the outer position, and the difference between a clean and dirty chain can be 12-15 watts"


Not sure what to make of this response since I've never had this issue on two other bikes equipped with Dura Ace 9170. Is it possible the bike with the beefy front fork is super stiff for most wheels?
Bianchi Oltre XR4, De Rosa SK Pininfarina, Trek Madone SLR, Giant TCR Advanced SL, Cervelo R5 Disk, Giant Revolt

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OtterSpace
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by OtterSpace

This can be a tricky one and could be any number of factors. While what they are saying isnt wrong its dismissive and still worth trying to fix if it bothers you. A minor issue is still an issue.

Make sure the hydro system isnt overfilled and bleed with the correct bleed block for your calipers. The correct bleed block for 12s shimano looks like a boat anchor Y2HW15000 while the 11s stuff looks like a block with holes.

Check the facing of your frame mounts with the calipers off the bike. Unfortunately QC doesnt always catch this and most bike shops never check either.

Align the caliper by eye while watching the spacing of the retracted pad to each side and slowly torque the bolts to spec (by this I mean each bolt first 2NM then 4NM etc up to 8NM or whatever your frame supports). Campag has a better method of aligning the caliper to the rotor as their bleed block has a cutout but their bleed block (UT-DB011) doesnt fit Shimano. Do this with the axle torqued to spec.

Confirm rotor trueness which you already touched on.

Make sure both pistons are pushing evenly and retracting correctly. Shimano has had complaints about this.

Unfortunately the Al and Steel material sandwitch that Shimano uses makes their Dura-Ace and Ultegra level rotors more prone to ticking than other rotors. They perform well thermally for higher loads but have this ticking issue more than other rotors even at lower heat load. If you ride mostly in places with under 20% descents consider switching to galfer or other rotors. Supposedly Shimano rotors have gotten better in each of the rotor revisions so RT-CL900 should be slightly better than RT-MT900 which is better than SM-RT900 for ticking.

Nereth
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Joined: Wed Jan 18, 2023 10:18 am

by Nereth

All the above is true, and serves to minimise the amount of clearance that you have, so that you are closer to an issue when things start to deflect under load.

But if it's only happening under load, you can minimise the amount of deflection under load sometimes, by just tightening your thru-axle harder. Check that. (note that a tightening the thru axle can itself move the centreline of the caliper laterally across the disc, since everything compresses a bit, so you may need to re-align to the tighter thru-axle setting. You need to keep your thru-axle torque relatively consistent when you remove/replace the wheel, because of that)

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Mr.Gib
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by Mr.Gib

That's a bs answer from Factor. Technically possible, but I'd like to see Factor get Shimano to say "yeah, our disk brakes rub, so what?" No, the brakes should not rub from moderate power out of the saddle. If you give it the absolute full stomp for a pedal stroke or two - 1500 watts+, then OK, it might happen. Otherwise they should be silent. The front end of these bikes is solid.

I got a little rub when my Ostro was new and dealt with it by careful positioning of the calipers. It also seemed that when the calipers were new the pistons were a little sticky, and perhaps I wasn't getting full retraction. That seems to have eased over time. It might be worth "exercising" the pistons a bit and pushing them back all the way.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

Attermann
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by Attermann

Most of the times that this happens, the mounting on the forks needs to be made square.

TobinHatesYou
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by TobinHatesYou

My bet is it's the same thing that happens on pretty much every aero bike fork. There is more flex when you swing your bike to the left than to the right. Leave a bigger gap between the outside pad and rotor than the inside pad. Use your eyeballs to measure out the gap, and look at the gap from both ends of the caliper.

MichaelK
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Location: London, UK

by MichaelK

Is that what Factor have been telling Froome for the past 3 years?!

Knedragon27
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Joined: Sun Jul 24, 2022 7:35 pm

by Knedragon27

MichaelK wrote:
Wed Jun 12, 2024 11:57 am
Is that what Factor have been telling Froome for the past 3 years?!
"We're gonna bring out a rim brake model soon ! "

ichobi
Posts: 1910
Joined: Thu Jan 19, 2012 11:30 pm

by ichobi

The ostro fork is almost 500g so the fork flex is probably not a factor. But the wheels are super super light for its depth. Not sure if wheel flex might have something to do with it?

Not sure why factor is throwing up efficiency lost numbers. Not relevant but nice to know i guess.

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Mr.Gib
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by Mr.Gib

TobinHatesYou wrote:
Wed Jun 12, 2024 4:38 am
My bet is it's the same thing that happens on pretty much every aero bike fork. There is more flex when you swing your bike to the left than to the right. Leave a bigger gap between the outside pad and rotor than the inside pad. Use your eyeballs to measure out the gap, and look at the gap from both ends of the caliper.
Is this due to the asymetry in the fork legs - one side being reinforced to hold the caliper? I would have thought that because both sides of the fork and and hub are united with high clamping force from the through axle, both sides would perform similarly.

Also the space over which the flex is relevant to brake rub is only from the dropout to the edge of the caliper - 80mm. That is such a short distance to allow much flex. Either manufacturers are really failing to make this area a solid as it should be, or the caliper is not sitting quite right.

@Noctiluxx, for whatever faults Factor may have, I know they obsess over properly machined caliper mounts. Double check that the caliper is perfectly parallel to the rotor - can be tricky to eyeball. I do it by jamming the caliper all they way to one side and then carefully move it back to center while watching the gap shrink on one side and grow on the other. Helps to keep me from accidentally adding some angle. I place a white piece of paper on the floor underneath my stand with a light shining on it to help my aging eyes.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

KalleWirsch
Posts: 94
Joined: Wed Jun 01, 2022 3:56 pm

by KalleWirsch

The question is if this is by general design at EVERY Ostro II or only at your bike. If it´s only at your bike, I would ask to fix it.
To find our, you need more examples.

TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

ichobi wrote:
Wed Jun 12, 2024 3:48 pm
The ostro fork is almost 500g so the fork flex is probably not a factor. But the wheels are super super light for its depth. Not sure if wheel flex might have something to do with it?

Not sure why factor is throwing up efficiency lost numbers. Not relevant but nice to know i guess.

The only part of the wheel that matters is the hub assembly (shell, axle, bearings, endcaps.)

Plus he swapped out different wheelsets and DT hubs like in the Aeolus RSL are pretty darn solid unless the bearings themselves are worn out. You’d notice that kind of lateral play though just by wiggling the wheel in the frame.
Last edited by TobinHatesYou on Thu Jun 13, 2024 8:41 pm, edited 1 time in total.

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spud
Posts: 1317
Joined: Sat Feb 07, 2009 5:52 am

by spud

Been riding an Ostro II DA, weigh 80+Kg, and have had no disc rub problems.

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