Chainring size
 

The company in the UK that I bought my 9yr olds racing bike from sells multiple sizes of single chainrings for the kids bikes starting at 30T and going up 32T, 34T etc etc

https://kidsracing.co.uk/collections...12671464603711

My son competes in road races, normally 6-8 miles long and in triathlons, mostly 3-4 miles in length. Most of the races are on pretty flat courses with a few small hills. When he comes out with me on rides we will tackle bigger and longer hills

He has been riding on a 32T single chain ring and I'm wondering would there be any benefit or harm to moving up to a 34 or 36T ring

thanks

UCI removed junior gear restrictions. Countries should follow.

I have 2 arguments:
Firstly, moving from a 32T to a 34T or 36T chainring may increase the gear ratio and make pedaling harder for your son, especially on longer rides and bigger hills. It's important to ensure that your son has the necessary strength and stamina to handle the increased resistance without risking injury or fatigue.

Secondly, the type of races your son participates in and the terrain of the courses should also be taken into account. If most of the races are on flat courses with only a few small hills, a 32T chainring may be suitable for your son's needs. Changing to a larger chainring may not necessarily result in a significant performance improvement in these types of races((

See cadence. I see no harm in a bigger gear, but the kid needs to be on top of it and not bogged down. A smaller gear allows for some snap.
The kids have far less trouble than adults pushing a big gear. Kids jump of things several times their height. Adults do it less. I know of no evidence having looked for it for decades that bigger gears cause issues. Smaller gears can cause overuse tendonitis.
For a kid, spinning too much is worse than pushing harder.

wow. Times have changed.
when I started racing I was amazed that the max gear I could use was 44x14, I tooled prior mostly on the flats in a 45x14. Forget that 52 ring. I could hang in in training rides but it was hummingbird legs to do so.
at the Nationals back then gear limits were off.
Limits were a California thing.
a few years later the Juniors (16-18 ) were internationally limited at 52x15 - which I thought was reasonable, I had no trouble keeping up with the National Team guys while training with that.

cassettes and limited ring sets have no doubt contributed to this.

it is also true that when climbing hills, a gear limit is not part of the limitations.
42x23 was considered a training gear only.

also of the time where Merckx used a 54-44 ( maybe 45) and 13-19 six block at the Worlds that year. Concepts have changed.

THE issue was just different riders in the SAME race not being allowed the same equipment.
There is a reason 11,12,13,14 tooth cogs are used. Some can spin faster than others. I am not aware of any pro doing a 52x13. Some of these teen kids are just as fast (top speed) as the road pros.

The responses I got from USACycling was the kids should learn to spin faster, which was coaching and their idea of how a rider should ride. That is not theri job, or if it is, it is the only sport I know of where the officials are coaching at the top level. Conversely, I would say ask why not push harder? That made me no friends except for the few that agreed with me.
I was raised (and involved with developing equipment to train for that) with spinning circles as the best way to go. I no longer believe that. The training, and how to race should be left to coaches, not officials.

Decades from now will be the tell if young riders age up and have joint issues.
‘I endured the gear limits, on the track it was worse. When I moved up to juniors at least it was 48 x 15.

NO evidence ever of that.
I do have evidence that over use (RPM) issues are worse for juniors.
i.e. Going 30MPH @120RPM is worse than going 30MPH@90RPM and pushing harder.

ok, cite the research paper(s), peer reviewed studies.

I can't cite papers where there is NO evidence, or there would be evidence. I once took a math class on proofs of Zero/Nothing.
Maybe you can find a study saying for the same power output there is more injury with kids pushing big gears vs spinning.
I can find all kinds of evidence about ACL injuries (not from cycling) - because it does happen.

Putting out the same power means they are spinning more. I can find articles on tendinitis caused by over use, and jumping and things much harder than what a cyclist is doing. My kid got it, we thought from too much spinning. We went to bigger gears and the problem went away.

I started racing on the road using a 72-inch-gear track bike as an intermediate at age 13, in 1964. That was back when the ABLA allowed track bikes to be ridden in road races, as long as the bike had one working brake.

The guys in the local club in New Haven were all at least 4 years older and riding road bikes. The training rides we did together were mostly over very hilly terrain, including roads steep enough to require switchbacks. I always at least held my own with them (despite their often trying to drop me), and I never had any knee problems.

Standing and climbing in a higher gear might even be easier on the knees than using lower gears. At least, that's my hypothesis to explain why my knees are still good after all these years of often riding a track bike with the same gearing as back then.

So, single point evidence. That is OK, but it is a single case. Sweeping generalizations are tenuous.
There are other things that can effect things, cleat adjustment, bent pedal shaft (that appeared pretty often when I was working at a shop) Thank goodness Campagnolo had readily available replacement parts. Also, you mentioned your son, I assume he was growing, growing into a saddle height can cure other factors. Also, kids mature at various rates.
It is good your son overcame his issue.

The UCI have changed their stance, OK, thank goodness my kids are grown up and probably better that they are not sports competitive.
back in 1976, I was offered Steroids to help build upper body bulk. I declined.
Guys I raced against and beat continued with the sport after I decided college was the way to go. I was self supporting, and that was not going to work as a bike racer. They made the '84 Olympic team and a few crapped out as they went for the blood packing and it went bad in a few cases.

I didn't give you a single point example where pushing a big gear may hurt minors which was the topic/context. I gave a single point that the opposite - spinning might be harmful. There was never any ban/protection against spinning. There are many papers on fatiguing tendons through over use. My "no evidence" of injury was on big gear being worse than spinning.

If there were evidence bigger gears may cause injury, the group that should find it (the papers) is the one now pulling that restriction.
USA Cycling has not stated any risk associated with gears.

I am making a sweeping general statement.
There is no study showing equal power output using a bigger gear is more damaging than using a smaller gear. I can't prove the negative there is no study. I can state I have searched for this for years and argued that there is no evidence of injury with USA Cycling
I cannot find anything by USA Cycling stating that.
I would like to be proved wrong on this as I have been looking for over a decade, but you can't prove a negative.

your mechanical assumptions are incorrect, 120rpm at the same road speed of 30, required less force than same speed at 90 rpm.
what worked for your son is fine.

True. But I have a hunch the risk of knee damage is higher for adults. I'd study them first.
My point was that there is no study indicating injury from big gears.
I was then asked to cite peer reviewed papers which prove there is no issue - which I can't do, because there is no evidence there is a problem.

This was a made-up thing by folks that thought there was a better way to ride, and then made rules that was really coaching.
I doubt it was really about safety. I suspect, in the USA, it was also about keeping the fastest riders from beating the adults.

The thinking person knows that the real danger of cycling is the crashes.
I don't even know if there are peer reviewed studies that show crashes are bad, I have not looked.
Even without such papers we have evidence - riders die, end up in the hospital etc.
The big gear thing for juniors, there is nothing.
In the USA, it limited the fastest riders.

Ok, yep, that makes sense:foo: