Should You Get A Bike Fit Before Buying A New Bicycle? | GCN Tech Clinic #AskGCNTech

Do you need to get a bike fit before buying a new bike? Why are disc brake rotors not any bigger? Can you use Shimano disc brakes with a Sram groupset? All of these questions, and more, answered in this week's GCN Tech Clinic!

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[nickmannerings]

Let’s make disc brake rotors the same size as the wheels. We could then use callipers to stop the bike 😂

[twraia]

Love the disk brake test idea. Maybe it can be a comparison between different kinds of disk brakes and rim brakes. Please make it happen!

[barrymonaghan]

Two suggestions for future videos: The pro's and con's of stainless steel frames vs other types of steel frames, I'm considering stainless.
The other topic, how many more sprockets do you think they can add before finally hitting a wall.
Thanks for the video!

[ResilientTim]

The largest rotor I have seen was 250mm on an experimental tandem build by one of the major tandem companies. There was a lively discussion on a FB tandem group a couple of months ago picking apart the rotors.

[bealachnaebad]

Whilst there is some difference in hydraulic fluid volumes between Shimano and SRAM brake master (lever) and slave (calipers) cylinders that could lead to incompatibility or an inefficient brake system, I would say by far the most important incompatibility is the fluid used.

Shimano use mineral oil, SRAM/Avid uses DOT brake fluid (glycol based) - the elastomer material used on the seal rings for mineral oil is not compatible with DOT brake fluid and vice-versa. Shimano almost certainly uses HNBR (or NBR) seals, SRAM most likely EDPM. NBR/HNBR will swell and degrade in DOT fluid, EDPM will swell and quickly degrade in mineral oil. In theory if you know the o-ring and/or seal ring sizes you could strip down lever/caliper and replace the OEM seals with a compound compatible with the brake fluid to be used, but it’s just not worth the risk.

[jedisdad]

Before the purchase AND after to ensure everything spot on for you ride!

[arundelnet]

Hydraulic fluid is completely different Dot vs mineral oil although the questions was mechanical which would imply rim brakes...

[theoriginaltylerdurden]

Keep wondering if Gcn only answers 5 tech questions a week. The backlog must be 300k by now

[mahinhinrider]

Hi GCN! Which is better, truing a wheel attached to a truing stand or attached to the frame and truing it to be centered? Thanks!

[trdchrisk]

#askgcntech I am changing my handlebar from an externally routed to an internally routed one. My question pertains to the hydraulic brake hose, would I have to install a new barb and olive before routing the cables internally in the handlebar? Shifters are Shimano GRX 815 Di2. Love the show! Thanks for the help!

[paulsymons]

Stopping my 100kg down the back of hardknott round the hairpins got my rotors to a nice blue colour. 160/160 icetech rotors with sintered finned pads. They still performed fine, just got *a tiny bit* hot :-)

[josephb]

#AskGCNTech Can you talk about the advantages/disadvantages of having different wheel depths front and back (Deep Section). How does a different combination fair in crosswinds, flats or hills vs two wheels with the same depth.

[hockysa]

literally been pondering a bike fit all day again today. get out of my head GCN!

[jonathanzappala]

The reason is you overwhelm the road bike size tire before a 160mm rotor. Unlike mountain bikes where the rotor gets overwhelmed before the tire reaches maximum grip.

[stuartdryer]

The wires for Shimano Di2 are only complex for the person installing it. After that the entire system is very trouble free. An advantage is only one battery to charge. I upgraded my two road bikes from Ultegra mechanical and have never regretted it.

[rhhmunro]

I upgraded to SRAM Red etap a couple of years ago and kept my Simano Ultegra rim brakes - never had a problem. Would be another story with disc brakes I suspect

[grahamhubbard]

It would be good to get Jon Cannings back. H e really knew his stuff. Another question answered incorrectly about mixing Shimano and SRAM!! you can if it rim brake but not if hydraulic

[hiddebart]

#AskGCNTech Last summer I upgraded my bike with a brand new set of deep-section carbon wheels. With the onset of the winter months, do I really need to switch to a winter wheelset? How big is the risk that I actually damage my carbon wheels (when using rim brakes)? Can damage be prevented by cleaning the brake pads after every ride? I'd hate to have to store the good-looking wheels for half the year. I only go for a ride when it's not raining and since I live in the Netherlands, I only ride on flat roads.

[andreacanonica]

#ASKGCNTECH hello GCN, great show as always! What are the structural differences between an (old) silent rear free hub and a (super cool) noise one? Given that the sound can only come out of the friction of 2 cogs hitting together, why is not more efficient to use a silent one? I guess a pro would be interested to gain some speed due to less friction when descending, no? Thank you very much!

[dhl]

eh, the cable pull on rim brakes is fine for Sram / Shimano. I use etap and dura ace calipers. zero issues. I've read it's not optimal but have no idea why, it works fine with zero issues.