Tubeless Inserts, Short Cranks & Track Tyres | GCN Tech Clinic

Hear ye, hear ye! Gather around for this week's community bike tech questions. In this week's GCN Tech Clinic, we'll be discussing how tyre inserts work. How to improve your head unit's visibility? And why you should be riding a shorter crank! Stick the kettle on, grab a snack and enjoy.
00:00 Welcome to the GCN tech Clinic
00:18 How do tyre inserts work?
01:27 How can I improve visibility on my head unit?
03:04 Why does my bike feel slow on hills?
05:00 Why do inner tubes have rolling resistance?
06:19 Will I get away with riding a shorter crank?
07:49 Are track racers still using tubular wheels?
09:22 Will an aero bike make a big difference when riding in a pack?
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[@gcntech]

Drop your tech questions in the comments using #askgcntech 💬

[@ancientrouleur]

#askgcntech I have an older steel bike that I want to ride in fast, flat races but tire clearance is limited to ~23mm. I have a set of Conti Sprinter tubulars currently installed...is there any data on how tires like this perform re: rolling resistance if you reduce the pressure to something closer to tubeless?

[@Flojo-1]

#askgcntech: Hi GCN TECH: My Ribble has 11-Speed 105 on it. Would a harder wearing chain like a Sram XX1 or Shimano Ultegra wear out the cassette and chainrings faster than using a cheaper, less hard wearing chain? Or is a hardwearing chain always the best route for longevity for all the drivetrain components?

[@LiamLeavesley]

#askgcntech Liam from the UK, would you have any recommendations for comfy footwear off the bike after a long day in the saddle? I’m riding in the French Alps (Annecy area) in a few weeks and don’t fancy wearing trainers or flip flops to the local restaurant. Great show btw

[@donaldgregoryventer2348]

#askgcntech Hi there Alex and Ollie. I am currently looking to buy a new bike, but I am stuck between 2 frame sizes of my chosen bike. Should I go for the smaller frame, or the larger frame? I am not into racing, but like a good group ride, and would like to be as comfortable as possible.

[@xardasvonlorien]

#askgcntech Hello there, really enjoy your show. I recently fitted aero bars to my bike and I like them a lot. Is it necessary or advised to wrap them in bar tape? They are made from aluminium if that makes any difference. And about that problem with eye sight you discussed, two things that work fine for me: I either use those mentioned cool looking cycling glasses combined with contact lenses or a helmet with a visor and my normal glasses underneath (which certainly won't work for all helmet/visor-glasses combinations).

[@yyams]

Just one thing - tyre inserts are CLOSED cell foam, otherwise they'd just soak up a couple KG of sealant. They advise you use something like 25% more sealant than usual to account for the extra area surface area it has to cover. I think with the deflection of the tyre as you roll, sealant gets pushed around the areas where it's in direct contact which is mostly just sidewalls anyways. I've had a minor sidewall tear seal just fine where it's in direct contact with the insert (MTB) so however it works, it certainly does.

[@docj511]

Tifosi makes off the shelf bifocal “reader” cycling sunglasses in various strengths and lens colors. I believe the model is Veloce. Cost is under a hundred bucks a pair.

[@Phillip-hq1bv]

I recently started to use the Tifosi Rx Adapter that was set up with my progressive lens prescription coupled with their Rail XC glasses. The adapter is almost invisible behind the mirrored lens of the Rail and it can also be swapped with several of their other model glasses. You can also easily swap the lens tint on their frames, mirrored, chromatic, colors, etc. Until I came across Tifosi, I had always worn prescription aviator style wire frame sunglasses with polarized tinted lens. The Tifosi are much lighter weight and were a great value. Another plus is that Tifosi is located in GA, USA.

[@andrewchalke1078]

Stick on reading lenses have worked really well for me. The ones I’ve used are like a half-moon shape you stick ( with water) to the bottom half of your cycle glasses

[@phillipsmith2359]

Stick on corrective lenses are great. I use them all the time. They would drive me crazy for general use but when you are only looking at 2 things - head unit and road, they are fine.

[@ianreid8041]

I think the guys are wrong about their answer. I’ve been using stick on +2.0 for nearly two years and love them. I won’t read a book or drive a car with them but they are perfect to ride with and look at the head unit. I’m a little careful about washing the glasses but have never had a problem with them coming off. I bought them on Amazon (many choices) and used contact solution to install after ensuring the lenses were very clean.

[@jonnol7105]

Stick-on half moon lenses work great on my Oakley’s. mine are designed for diving masks and stick on the inside. Another option I use is Engo2 Heads-up display sunglasses.

[@BrianRPaterson]

HuD glasses sound expensive.

[@rayk6251]

Regarding 170 cranks: When I bought my bike in 2018, I had a bike fit done and it was determined I should go from 172 to 170 cranks. I'm 5' 7", and this change made a huge difference in comfort and better power output. Bottom line, a bike fit is well worth it.

[@ronniehodges4835]

Great show. Teresa, as you said, may find a freewheel change helpful. I am old and climb a fair number of hills inm6 area on an Emonda. Mine came with a 11 - 28 freewheel. I changed to a 11 -32 which helped me a lot. This did require a rear derailleur change as well. This does not sound like a large change but there was a very noticeable change in my ability to not hate the hills so much. Good luck

[@Shellewell]

Shorter crank also also gives you slightly more clearance from grounding a pedal or from catching on undergrowth if gravel riding on paths. The change I find just going from 175 to 172.5 is noticeable, not necessarily in terms of being much faster, but I find keeping a higher cadence easier.

[@arcboutant]

All my bikes have been the usual 170/172 cranks. I was never comfortable. 3 years ago I built a full carbon bike . The groupset cranks - yup- you’ve guessed it 172. Bike was fine but something wasn’t right. I saw on eBay a guy selling full bottom bracket set with 160 cranks. Fitted them and the comfort and ease was amazing . As I have a short back and deep chest and always was restricted by my thighs against chest -no more 👌🏻

[@edgerat]

YUP!!! I am on 160 on everything.

[@___Bebo___]

I'm 185cm with a big cycling inseam. I'm supposed to be on 175mm or something crazy like that. 165mm on every bike knee pain free for like a decade now from it.

[@nisched.]

Thanks for answering my question. Have fun in New York guys.

[@kimwrinkle100]

Best wishes, Ollie and Alex, on your New York adventure!

[@kennethward9530]

Ollie is absolutely spot on about liquids on the track-liquid latex sealant would absolutely end a night of racing especially on short board/plywood tracks with up to 51 degrees of banking. Outdoor concrete tracks, not so much an issue.

[@nelsonm.5044]

Tonight I juste made my first ride using TPU air chamber with m'y tires and as not entirely convinced I was of the results, the ride is was smoother on poor asphalt and it seemed a little bit easier when accellerating

[@fitzt70]

Failed to answer the first question! My optometrist recommended the stick on bifocal lenses for me as I could not read my phone / head unit. Works fine.

[@fitzt70]

Oops, second question @1:45

[@mjsylver]

I currently use the stick on lenses on both of my lenses and love them. You just need to be careful when washing them with soap and water.

[@cb6866]

Thanks Alex, Isaac , and Dr O. .....

[@andyfriendsmith]

I started using prescription cycling glasses last year - expensive, but the best investment I've made recently in cycling tech. I'd like to say it helps me to read my power data off my bike computer, but actually the best thing is that I can now read the café cake menu!

[@michaelnewman4302]

My Oakleys are bifocals. The lower part is adjusted for the distance to my head unit.

[@josephbikes]

On track bikes: Not all velodromes are silky smooth. In fact, velodromes are quite rare here in the states, with the indoor variety being much moreso. Most are outdoor concrete tracks that require yearly patching. The two velodromes I've ridden on are actually pretty bumpy, comparable to my morning commute. They've shut down my current local velodrome, but the last time I raced it I was on 23mm tubulars because that's what I thought trackies did. Now that I've learned what we know about tire size and rolling resistance, I'm very curious to try another track event on 28c clinchers with latex tubes and lower pressure. I don't think there is any benefit to riding skinny tubs at high pressure on the vast majority of the velodromes here in the states. I agree that sealant could be a real hazard, even on a concrete track.

[@aeronut6663]

Stick on lens work really well in cycling glasses. Quite adequate for a glimpse at data fields and route. Been using them for a couple of years now. I have 2 sets 1 each for dark and yellow lens. I have the +2 strength.

[@Zoidborg7]

With regard to crank lengths, I have always used a 175mm crank. I tried using 170s on my mountain bike for a while, and I could feel a noticeable loss of torque and went back. I am very tall, however, and I think a natural crank length for me is 180 give or take with my long femurs. The gentleman trying the 170 power meter cranks should take that into account, that the 175 mm size may already be smaller than what the "normal" size might be, just as he mentioned in his clip. The 170s may work, but don't be surprised if you feel they are hurting rather than helping if you have long legs.

[@timtaylor9590]

easy way to explain tubes effecting rolling resistance, is comparing cheap or bomb proof tires vs race or tt tires. a tube is apart of the tire just not glued on like the other layers of a tire.

[@DanTuber]

what's the watt difference between butyl vs latex?

[@living4adrenaline]

I've used cushcore, not sure if it does anything but one benefit is you would be able to ride out on a flat if necessary.

[@timtaylor9590]

helmet is more important than a bike in a group

[@GregLanz]

I used 175mm cranks on my road and MTB's for decades however when I got a crank for my gravel bike I went with 170mm mostly for pedal clearance

[@joshebrown2575]

#askGCNTech for those of us who are not as fit as others, like these two very fit beasts Alex and Ollie, I am thinking that having the lightest, and probably more expensive, bikes and components are not that important. Probably a heavier total bike weight would be a better way to get fit or fitter. Is this good thinking? If not please explain. Thank you for everything that the GCN family does.

[@alexandrevasconcelos4593]

I wear prescription glasses. Can’t see a thing without them. So I have bike helmets with visors. Gyro vanquish and Casco rs2.

[@barrysmith9154]

I have two pairs of Oakley glasses one set of Ruby and one set of react lights glasses Both Glasses are for my eyes. Not cheap.

[@justim4545]

Didn't discuss why tubulars are king on the track, which was the question.

[@irunslowNC]

I need glasses for reading, I found safety glasses with "reader" inplace bottom of lens. At Walmart in the USA, they are 6.00 USD. Come in clear, amber and dark. Wrap around, look good, protect your eyes and work perfect. I can have 5 windows open on my wahoo and see even the small print.

[@playandteach]

You can get super cheap safety glasses which are bifocal. Strong enough to protect your eyes and a range of focal lengths easily available . However I use clear or yellow lenses rather than sunglasses but I don't feel the need for the sunglasses aspect . Just protection from stones etc.

[@luc4beejay]

#askGCNTech Planning the first Summer holiday with waxed chaing bike. Any suggestion in case of rainy/wet days? Bring a second chain? What to do in case the chain gets rain? Go and dry it out and maybe use the Supersicret Wax from Silca (not planning to bring with all the stuff for full rewaxing). Thanks for the advises!

[@colinmartin2689]

The hill riding question, the poster needs to be riding at just below FTP for longer climbs, regarding the track tyres, the sealant is in tubeless to cure many punctures, on a track (indoor) I'd imagine no sealant is required? but the higher tyre pressure point still stands.

[@edromero7985]

I've tried contact lenses and they blew out in downhill speeds.....go with the prescription sunglasses ...well worth it!!😊

[@Millicente]

On the topic of prescription cycling sunglasses, I can't get them! Every pair always results in "sorry we can't do that prescription on this." Perhaps because of my astigmatism. In the end I have to wear casual sunglasses like aviators or wayfarers with prescriptions which always slide around.

[@seattlegrrlie]

My last bike was a "touring" geometry and every time I'd go up a serious hill I'd feel out of balance, same going downhill. Not saying there is a perfect climbing bike, but geometry does matter

[@paulwoodward8265]

Prescription lenses in glasses won't work well in this case. I mean, they might work to put my head unit in sharp focus, but then I would not be able to focus on the road, never see potholes or into the distance on a descent. Larger head unit with fewer fields is helpful, but things like map reading, following directions or seeing notifications are still an issue. There are some useful ideas in the comments - bifocal glasses could be a winner, if implemented well, and I might also try stick on lenses.

[@johngretton8543]

#askgcntech I am a fan of tubeless but one downside is dried sealant is very hard to clean of frame, any tips on cleaning it of.

[@adamweb]

#askgcntech I use Silca Super Secret drip on wax on my trainer indoors... Do I need to clean the chain with boiling water each time before reapplying wax or can I top it off every couple hundred of miles and clean the chain every 500 mi or so?

[@chrisridesbicycles]

#askGCNTech I have two sets of chainrings for holidays in the mountains and my normal flatish rides which need two different chain lengths. How would you store the non used chain?

[@blackflamesolutions526]

#askgcntech I have 'slammed the stem' on my new Cannnondale, and now I have 6cm of spacers sticking out on top of the stem. Is this dangerous if I fall forwards in a crash, and is it possible to saw the stem so that this extra length is no longer an issue?

[@_J.F_]

Yes, you can saw the surplus off but make sure you are happy with the setup first.

[@feedbackzaloop]

Haven't we just seen Pog riding 165mm cranks despite not being height challeged at all?

[@Sverting]

The foam+sealant part seems 100% wrong. #askgcntech It is just the centrifugal force and gravity pushing the liquid to the outermost or lowest part of the wheel - the inner wall of the tire. Foam inserts do not act as a sponge. Sponge is more air than solid - more of a scaffolding than the material. Inserts on the other hand are elastic material with air bubbles inside. They are not permeable. Think pool noodle. They do not absorb water to much, do they?

[@wspmjw]

#ASKGCNTECH Howdy Tech Gurus! I have a set of Vitoria foam inserts in my 28mm Continental GP5000S tubeless tires. On a local ride a couple of months ago, I experienced a puncture that defeated the sealant. In the past, the insert worked flawlessly allowing me to complete a century event. During the most recent puncture, the insert didn't fill the void and I experienced a 1.5-mile walk home. Do these inserts have a useful life? I don't recall seeing this in the documentation that arrived with the inserts. Thanks for the knowledge.

[@perrymiddlemist9969]

#askgcntech I use one bike on my indoor trainer and one for outside. As I live in northern Minnesota, my outside bike stays inside all winter. I'm considering switching to tubeless, but I'm worried about winter storage. Is there an issue with having tire sealant sitting in my stored bike (indoors) all winter? Or will it dry up or solidify by the time riding season comes around?

[@adadinthelifeofacyclist]

It's impossible to say what size crank would suit a rider without knowing their size! Using cranks too long or too short can cause patella tendon problems, either due to the increased force or the increased knee flexion.

[@feedbackzaloop]

#askgcntech as 36cm bars have become standard in pro peloton, where - outside boutiques - can an amateur rider find them now?

[@user-pe5qj8cz8n]

#askgcntech Made the mistake of replacing my tubeless tyres whilst still in my cycling kit. Need your top tips on how to get rid of dried sealant from clothes, I've tried sealant remover but it's had no noticeable impact :(

[@rickcski8082]

Why would a track tire need sealant while using tubeless tires? I would think the track would be kept free from possible puncture inducing objects.

[@mikekeslin5038]

Most tubeless tires slightly weep air thru the sidewalls. The sealant gradually seals these insidious ’tunnels’ thru the sidewall layers. I don’t see why you couldn’t dump the left over sealant after the tires are ‘cured’.

[@charliecase1316]

#ASKGCNTECH - I have a spare Tiagra groupset with mecahnical disc brakes (which I hate). I am also lucky enough to have a permanent bike/turbo set-up with an under-utilised 105 rim brake groupset I want to use elsewhere. Anything stopping me putting the Tiagra groupset on the bike/turbo set-up and just not connecting the brakes???

[@Jay_Thurston]

#askgcntech everyone seems to like a loud freewheel, but isn’t sound that is caused by movement a result of friction? If that’s true wouldn’t we strive for the quietest freewheel possible?

[@bobfranklin4695]

#askgcntech Hi love the shows. My question is regarding cable routing, I have just watched a build video on a bike with a hidden cable set up They where using wireless shifters with hydraulic brakes. The angle that the hoses went from under the stem to down the headset seemed too extreme for cable pulled brakes/gears, ok for hydraulic hoses but.... So can I get away with hidden cables? Thanks in advance Bob.

[@MathiasJensen-kd1pm]

#askgcntech As a heavier rider, 105kg / 231,485 LBS i have had a bit of problems with my tyres. my tyres recommend 3,5 to 5,9 bars, but when running that "high" it feels like every small pebble will puncture my tyre, but running lower than even the 3,5 bars it feels like im riding on a flat tyre. my bike does seem to have clearence for wider tyres than i run now and im running on about 30mm tyres. should i get wider tyres to be able to run lower preassures or are there other tips for how that setup could be better to remove the "anxiety"

[@___Bebo___]

You're above the weight limit on most 30 and 32mm tires, your size is 35mm.

[@dicksy69]

#askgcntech Hi GCN Tech Team, I am due to travel abroad with my bike for an event in July. I am flying but have a concern over the hydraulic disc brakes. Is there any issues in doing this or anything that can be done to safeguard the braking system whilst being transported? Stay safe J.

[@nicholasfitzgerald1999]

#askgcntech Hey Alex and Ollie, for people running latex inner tubes and don't want to make the shift to Tubeless just yet, should they look to run Tubeless Ready Tyres or just normal clincher tyres. It seems all tyre brands are shifting their efforts to improving TLR tyres and ignoring clinchers. Would it be faster to run Pirelli P ZERO Race TLR or (RS when available) vs P Zero Race clinchers despite the weight penalty? Please avoid the old " just go tubeless answer " and provide some pros vs con. hahaha Cheers

[@mnbv5555cxz]

@4:03 Ollie "most bike are pretty stiff" ...actually most bikes are 20% stiffer than last year's model

[@davidkoothottil]

On a track, can't we use tubeless tyres without the sealant in them? Or just enough sealant to set it up the first time. There should be no risk of getting a puncture on a track.

[@adadinthelifeofacyclist]

If sealant does get onto an indoor track the track would have to be cleaned. But as there's very little chance of punctures tubular tyres are still top choice for track cyclists, particularly as the track is smooth so you can ride 200psi in comfort

[@andymakarewich]

Tracks won’t allow sealant on the track for the reason Ollie said

[@user-lx6pk9os2d]

So we're going to fart on filling our tyres with sealant and a foam core that completely negates any advantages of tubeless? Or you could just use an inner tube...

[@lbx5359]

#askgcntech If liquids are so dangerous in velodromes, are sweaty people banned from the sport?

[@edb8120]

And on the track, there is still nothing lighter than tubular rims with tire containing lightweight tubes.

[@larrylem3582]

An ebike will help you get up hills. haha

[@chrisdavidson911]

Someone giving an opinion that a bike is good for climbing should also take into consideration that rider's ability to climb. For example, i would describe every bike - not ebikes or motorbikes - as being genuinely terrible, but the problem is actually with me and not a reflection upon the bike(s).

[@williamschultz8198]

Why can't there be more allotted time?

[@elliyeti73]

Perscription cycling sunglasses are very expense e.g. over $600 a pair. Perscription normal sunglasses are much cheaper for the same brand. (not as cool though).

[@easternbrown]

I got some bifocals, with normal reading glasses I wouldn't be able to see the road properly.

[@ofeykalakar1]

Most tracks don’t allow tubeless setups- sealant and tire pressures need to be high. Hookless wheels are also not allowed Tubulars attached to the rim with tape are not allowed Tubulars that are glued onto the rim and tires at high pressure are allowed Clinchers with hooked rims and inner tubes at high pressure are allowed These are for indoor hardwood tracks As for outdoor cement surface tracks rules may vary.

[@BillywhizS14]

Stick on prescription lenses seems to be a tech story to cover. It’s common and you didn’t answer their question. In addition to Tifosi mentioned by @Docj511, Rudy Project also do a sports reader series with set prescription stickers about the same price as normal lenses.

[@petersolas6665]

Rudy Project offer bifocal lenses.

[@JFomo]

I'm guessing Teresa doesn't climb with power when going up hills.

[@douglasbooth6836]

Inserts rule.

[@SecwetGwiwer]

Studies have shown that most people could go down to 145mm cranks with virtually no drawbacks and multiple benefits.

[@Timtimzi]

Sauce?

[@robduncan599]

As a short rider 5'4" with 27" inside leg I have a ultegra 165mm and a hack bike with 140mm , the 165mm is on or above my limit. I think everyone should have a crank length that matches your inseam ? The question then becomes what is that ratio?

[@SecwetGwiwer]

@@Timtimzino thanks, but I’d like some salt please.

[@iann23]

"Please buy these replacements for free air"

[@jprowland]

I'm crushed that you didn't say "Young's Modulus" when discussing rolling resistance. Be better

[@Tachikoma36]

From Teresa's question phrasing, I bet they'd smoke me up a hill...

[@jugaloo5873]

Woop woop, riding chinese wheels eh?

[@trroland1248]

Terrible *trend* this short cranks trend. 😏