Please don’t make this a rim vs disc bloodfest. Stage 17 won with rim brake

Discuss light weight issues concerning road bikes & parts.

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tomato
Posts: 594
Joined: Mon Jul 01, 2019 8:37 pm

by tomato

cveks wrote:
Wed Aug 11, 2021 9:08 pm
Science is science. For example I rode bike for years with unshaven legs . Once I find out research which says that you save 10 watts if you shave legs. So I shaved mine first time in my life and that brought me increase in both my top speed, FTP, and level of cycling. Aero rim brake bike, shaved legs, 38 mm deep aero carbon wheels is killing combination for me :)
Yes, it's a well known scientific fact that shaving your legs will increase your FTP.

tjvirden
Posts: 478
Joined: Sun Nov 22, 2020 9:21 pm

by tjvirden

You beat me to it!
This is where I've been going wrong all these years - most of my cycling buddies have been leg shaving; I can hardly keep up!

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Lewn777
Posts: 1214
Joined: Thu Mar 09, 2017 5:35 am

by Lewn777

vinny wrote:
Wed Aug 11, 2021 3:43 pm
how about discs are better for descending cuz it doesnt heat up the wheel and cause the resin to heat up and soften.

here in northern california there is a hill mount umunhum where friends with rum brakes and clinchers had there carbon wheels soften and loose all pressure.

this has happened to at least 2 people i know personally, and others that i heard about.

luescherteknik has a video describing this, pros mostly run tublar wheels which are thicker etc....
Poor bike handlers go on a training ride with poor quality race rims. Most carbon modern carbon rims (even Chinese rims) stand up much better to poor bike handling brake dragging. Even then you have to ask 'why go on a training ride on race rims?' You can get lovely coated 1300-1400g alloy rims for some competitive training rides.

openwheelracing
Posts: 249
Joined: Thu Jan 28, 2021 6:41 am

by openwheelracing

Don't forget the points Chris Froom made. Current generation road disc brakes do not compare to MTB setup. Weight being the biggest issue compared to rim brake. Road disc has too many compromises. It causes warping and heat build up. This is straight from someone who actually uses his brakes and is in tune with all parts of his bike. Only way to continue to market disc brake road bike is to kill the rim brake cause latest gen rim brakes are just that much better. Fingers crossed new DA and Ultegra make good improvements.

vinny
Posts: 118
Joined: Sun Nov 17, 2019 5:17 pm
Location: california

by vinny

Lewn777 wrote:
Wed Aug 11, 2021 9:50 pm
vinny wrote:
Wed Aug 11, 2021 3:43 pm
how about discs are better for descending cuz it doesnt heat up the wheel and cause the resin to heat up and soften.

here in northern california there is a hill mount umunhum where friends with rum brakes and clinchers had there carbon wheels soften and loose all pressure.

this has happened to at least 2 people i know personally, and others that i heard about.

luescherteknik has a video describing this, pros mostly run tublar wheels which are thicker etc....
Poor bike handlers go on a training ride with poor quality race rims. Most carbon modern carbon rims (even Chinese rims) stand up much better to poor bike handling brake dragging. Even then you have to ask 'why go on a training ride on race rims?' You can get lovely coated 1300-1400g alloy rims for some competitive training rides.
Actually my 2 friends are good/great bike handlers. One used to race in his prime. One had zip carbon wheels and the other had roval wheels. Both got too hot and the resin melted.

They were not on cheap rims. Both have since bought disc bikes.

With discs why do i need cheap training bikes, i don't race, all of my rides are "race rides"

Here is another test.

https://www.cyclingnews.com/features/al ... heat-test/

stevesbike
Posts: 218
Joined: Thu Oct 24, 2019 5:33 pm

by stevesbike

vinny wrote:
Thu Aug 12, 2021 1:43 am
Lewn777 wrote:
Wed Aug 11, 2021 9:50 pm
vinny wrote:
Wed Aug 11, 2021 3:43 pm
how about discs are better for descending cuz it doesnt heat up the wheel and cause the resin to heat up and soften.

here in northern california there is a hill mount umunhum where friends with rum brakes and clinchers had there carbon wheels soften and loose all pressure.

this has happened to at least 2 people i know personally, and others that i heard about.

luescherteknik has a video describing this, pros mostly run tublar wheels which are thicker etc....
Poor bike handlers go on a training ride with poor quality race rims. Most carbon modern carbon rims (even Chinese rims) stand up much better to poor bike handling brake dragging. Even then you have to ask 'why go on a training ride on race rims?' You can get lovely coated 1300-1400g alloy rims for some competitive training rides.
Actually my 2 friends are good/great bike handlers. One used to race in his prime. One had zip carbon wheels and the other had roval wheels. Both got too hot and the resin melted.

They were not on cheap rims. Both have since bought disc bikes.

With discs why do i need cheap training bikes, i don't race, all of my rides are "race rides"

Here is another test.

https://www.cyclingnews.com/features/al ... heat-test/
Advances in resin and pad material (along with a move toward deeper rims that have better heat dissipation) has largely solved problems of delamination. The potentially bigger issue of heat causing tube expansion and tires blowing off has also been addressed by tubeless and lower pressures. I have a plate in my arm as the result of a tire coming off the rim under hard braking, and thought disc brakes were gong to be needed to solve the problem, but was wrong. Have since competed in 2 Haute Route Alps on rim brakes with no issues - including 100km/hr top speeds on descents....

vinny
Posts: 118
Joined: Sun Nov 17, 2019 5:17 pm
Location: california

by vinny

stevesbike wrote:
Thu Aug 12, 2021 2:12 am
vinny wrote:
Thu Aug 12, 2021 1:43 am
Lewn777 wrote:
Wed Aug 11, 2021 9:50 pm
vinny wrote:
Wed Aug 11, 2021 3:43 pm
how about discs are better for descending cuz it doesnt heat up the wheel and cause the resin to heat up and soften.

here in northern california there is a hill mount umunhum where friends with rum brakes and clinchers had there carbon wheels soften and loose all pressure.

this has happened to at least 2 people i know personally, and others that i heard about.

luescherteknik has a video describing this, pros mostly run tublar wheels which are thicker etc....
Poor bike handlers go on a training ride with poor quality race rims. Most carbon modern carbon rims (even Chinese rims) stand up much better to poor bike handling brake dragging. Even then you have to ask 'why go on a training ride on race rims?' You can get lovely coated 1300-1400g alloy rims for some competitive training rides.
Actually my 2 friends are good/great bike handlers. One used to race in his prime. One had zip carbon wheels and the other had roval wheels. Both got too hot and the resin melted.

They were not on cheap rims. Both have since bought disc bikes.

With discs why do i need cheap training bikes, i don't race, all of my rides are "race rides"

Here is another test.

https://www.cyclingnews.com/features/al ... heat-test/
Advances in resin and pad material (along with a move toward deeper rims that have better heat dissipation) has largely solved problems of delamination. The potentially bigger issue of heat causing tube expansion and tires blowing off has also been addressed by tubeless and lower pressures. I have a plate in my arm as the result of a tire coming off the rim under hard braking, and thought disc brakes were gong to be needed to solve the problem, but was wrong. Have since competed in 2 Haute Route Alps on rim brakes with no issues - including 100km/hr top speeds on descents....
That is good to know. the road i am speaking about is a ~10% grade all uphil then obviously a ~10% grade down. My biggest thing is that the wheels i have are super expensive (at least for me) and having them being used as a wear item, seems silly. A disc is cheaper and easier to replace.

You all speak about how easy it is to set up rim brakes vs disc. For me, being used to cars and motorcycles, i find disc way easier to set up and adjust. I feel that i can get mine dialed in pretty fast.

MoPho
Posts: 763
Joined: Sun Jul 10, 2011 7:48 pm
Location: NorCal

by MoPho

stevesbike wrote:
Thu Aug 12, 2021 2:12 am


Advances in resin and pad material (along with a move toward deeper rims that have better heat dissipation) has largely solved problems of delamination. The potentially bigger issue of heat causing tube expansion and tires blowing off has also been addressed by tubeless and lower pressures. I have a plate in my arm as the result of a tire coming off the rim under hard braking, and thought disc brakes were gong to be needed to solve the problem, but was wrong. Have since competed in 2 Haute Route Alps on rim brakes with no issues - including 100km/hr top speeds on descents....
A friend of mine delaminated his new Bontrager carbon wheel competing in the Haute Route Alps the year before the pandemic. It still happens

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Shpox
Posts: 88
Joined: Fri Jul 05, 2019 11:30 am

by Shpox

Well this is my simplified take on this:

1. Rim brake + Aluminium Rim = Fine but the wheel tends to be heavier and not aero.
2. Rim brake + Carbon = Generally not fine, depending on the wheel you choose. Not ideal for braking.
3. Disc Brake + Carbon Wheel = Fine but heavier (due to the disc) and aero.

A disc brake bike is more fiddly and heavier. I also don't believe the industry has sufficiently engineered the tolerances so there is, even more, to talk about.
A rim brake is easier and simpler to maintain but doesn't perform as well in braking, especially in the wet.

I feel there still very much is a place for rim brake bikes, direct mount or otherwise. I can sympathise with the frustration of being forced to purchase a bike which requires more maintenance and is heavier, at the cost of better brakes. If the execution was tippy top, then it's only the weight that would be an issue.

Mcdeez
Posts: 287
Joined: Fri Nov 27, 2020 3:40 pm

by Mcdeez

cveks wrote:Science is science. For example I rode bike for years with unshaven legs . Once I find out research which says that you save 10 watts if you shave legs. So I shaved mine first time in my life and that brought me increase in both my top speed, FTP, and level of cycling. Aero rim brake bike, shaved legs, 38 mm deep aero carbon wheels is killing combination for me :)
lol...

blutto
Posts: 137
Joined: Thu Jun 21, 2012 5:09 pm

by blutto

tjvirden wrote:
Wed Aug 11, 2021 4:33 pm


With respect, I think that although you may have a lot of experience, what you say indicates that it's narrow experience. I still use rim brakes in 'bad' conditions sometimes (cold and wet) and then it's not uncommon to be limited by the brakes, not the tires. That's using either Swissstop BXP/Koolstop [Salmon] pads on a variety of alloy rims. The braking is good enough, almost all the time, for me to keep using those setups, but I have had some "oh sh*t" moments. Anticipation is of course the best course of action for any braking system.

You appear to have explained why you've never worn a rim out from braking - they're damaged in some other way first; that's very common for someone doing plenty 'performance' riding.

As for how much braking in the rain to wear out a rim - well, Jobst Brandt gave an estimate for that (0.1mm off the rim coming down from an Alpine pass). You can read about it here: https://yarchive.net/bike/rim_wear.html


In my experience biggest factor is the amount of grit on the roads one rides on; I can get through a rim in 6 months of Autumn/Spring/Winter in a rural, agricultural area without significant hills - just undulations and junctions. About 5000 Km.
A couple of points...

To the first part of the bolded bit....most of the damage that has affected my rims was to the rear wheel ( pulling spokes thru etc...)....the front rims last seemingly forever ( though they do get bent on occasion due to stupidity or bad luck.. ) and as we know a greater portion of the braking is handled by the front wheel but even given that no worn out front rims due to braking...in fact some of the anodizing is usually still on the rim even towards the end...

As for the Jobst estimate.....does that mean that virtually all of the wheels used in a Grand Tour have worn out rims by Tour end and become a potential danger to the riders....funny have never heard reference to this issue or stories about worn out wheels exploding towards Tour end ( this assuming some team mechanics weren't being thorough in their maintenance ....or an iffy wheel slipped thru the best checks...or some poor teams couldn't afford enough replacement stock...).

Cheers

tjvirden
Posts: 478
Joined: Sun Nov 22, 2020 9:21 pm

by tjvirden

If most of your riding is in dry conditions, or mildy damp with clean roads, then I can quite see why your rims last. Another factor that may be relevant is whether you only use one set of wheels until they're worn, or spread use across multiple sets.

I have some rims with 15000 miles on and that's with plenty of braking too - essentially only dry weather use though.

Grand Tours don't usually have much descending in the wet! Look at the Giro this year - mountain stages cancelled because of very wet weather (fair enough too, because racing in the wet is a different thing - the risks are so high). Also, it's worth pointing out that Jobst was not a small rider - in younger years he was probably stopping 110Kg (90+10+10 for him, bike, clothes/luggage) and that's significant - the wear will be approximately proportional to total mass (actually wear will likely be appreciably higher, proportionaly, as weight goes up since the rider reaches higher speeds). At least 1200m vertical descent from some passes with lots of braking, and I'm sure the 0.1mm is about right - this is only in wet conditions though. Near zero wear to rim or pad in the dry.

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