Looking to change my chainrings from the stock 52/36 I currently have on my TT bike. I am an okay cyclist- FTP 320@ 66kg. I live in a hilly area and also my A Ironman race is very hilly with ~7500 ft climbing. I was hoping to change to either a 54/39(if this will work) if not 54/42 or a 55/42, then running a bigger cassette for the Ironman: 11-32/11-30. My other events are flattish. Any help or thoughts would be welcome, thanks
4.8 W/Kg and you think you’re an OK cyclist?
With the 39 I suspect you could run an 11-25 or something and swap to an 11-23 for the flat course. You will need to swap to a 130 BCD crank, but should be able to find one cheap used. Bigger than 53 might be expensive and not needed.
54/39(if this will work)
You can probably make it work. But it’s not sanctioned by Shimano or SRAM, and you might run increased risk of front shifting issues.
54/39(if this will work)
You can probably make it work. But it’s not sanctioned by Shimano or SRAM, and you might run increased risk of front shifting issues.
What’s the issue, the curve of the front derailleur?
What’s the issue, the curve of the front derailleur?
I don’t know the precise technical limitation, just that it’s a tall jump. Shimano (afaik) has never sold a factory-provided big/small ring combo with greater than a 13t jump between the two. Nothing magic happens between 54/39 and 53/39, but for whatever reason, that’s where they draw the line. People have gotten it to work, some claiming no noticeable issue. But this is one area where I stick with factory recommendations. Just one dropped chain at an inopportune time wipes out any marginal efficiency gain.
What’s the issue, the curve of the front derailleur?
I don’t know the precise technical limitation, just that it’s a tall jump. Shimano (afaik) has never sold a factory-provided big/small ring combo with greater than a 13t jump between the two. Nothing magic happens between 54/39 and 53/39, but for whatever reason, that’s where they draw the line. People have gotten it to work, some claiming no noticeable issue. But this is one area where I stick with factory recommendations. Just one dropped chain at an inopportune time wipes out any marginal efficiency gain.
53 x 11 is a pretty stout gear. When I was young and strong I tried 60 with 180 crank arms on my TT bike. It made me no faster.
What’s the issue, the curve of the front derailleur?
I don’t know the precise technical limitation, just that it’s a tall jump. Shimano (afaik) has never sold a factory-provided big/small ring combo with greater than a 13t jump between the two. Nothing magic happens between 54/39 and 53/39, but for whatever reason, that’s where they draw the line. People have gotten it to work, some claiming no noticeable issue. But this is one area where I stick with factory recommendations. Just one dropped chain at an inopportune time wipes out any marginal efficiency gain.
53 x 11 is a pretty stout gear. When I was young and strong I tried 60 with 180 crank arms on my TT bike. It made me no faster.
Can you even get a 54 in a 110 bcd crank?
First thing to remember here is that power makes you go faster - gear ratios are (almost) completely irrelevant to speed.
Some TT’ers do choose to run a bigger chainring, because that allows them to run a straighter chainline at typical speeds, which might get you 1-2 watts in efficiency. However, it is important to remember that “typical speeds” are much higher for say, a 10 mile TT, than they are for an IM bike leg.
A 5 hour IM bike implies an average speed of 36 kmh, or 22.4 mph - or 52/16 at about 90 rpm, right in the middle of an 11-25 11sp cassette. A 24 minute 10 mile TT (25mph) would be in the 15 tooth cog, and would need to go to a 56t chainring to get back to the 16 cog in the middle of the cassette to maintain that 90 rpm cadence. So the case for a larger chainring is far less compelling for a IM bike leg than for a 10 mile TT.
In moving to an 11-30 or 11-32 cassette, you increase the jumps between cogs, and may end up in a less than ideal cadence trying to maintain your target power. Add to this the increased risk of a dropped chain with non-standard big ring/little ring combinations, and my advice would be to keep the 52 chainring and the tight cassette. Unless perhaps you are a huge “masher” and are currently doing IM bike legs at 75 rpm in the 13t cog??
Thanks for the info, I am pretty new to the sport- had my first race season last year, and not very knowledgeable yet. I usually average around 88-90rpm for my TT’s and the 70.3’s I did last year
Haha don’t want to sound like a chopper!
What’s the issue, the curve of the front derailleur?
I don’t know the precise technical limitation, just that it’s a tall jump. Shimano (afaik) has never sold a factory-provided big/small ring combo with greater than a 13t jump between the two. Nothing magic happens between 54/39 and 53/39, but for whatever reason, that’s where they draw the line. People have gotten it to work, some claiming no noticeable issue. But this is one area where I stick with factory recommendations. Just one dropped chain at an inopportune time wipes out any marginal efficiency gain.
53 x 11 is a pretty stout gear. When I was young and strong I tried 60 with 180 crank arms on my TT bike. It made me no faster.
Can you even get a 54 in a 110 bcd crank?
No, he’d need to swap out to a whole new crankset
First thing to remember here is that power makes you go faster - gear ratios are (almost) completely irrelevant to speed.
Some TT’ers do choose to run a bigger chainring, because that allows them to run a straighter chainline at typical speeds, which might get you 1-2 watts in efficiency. However, it is important to remember that “typical speeds” are much higher for say, a 10 mile TT, than they are for an IM bike leg.
A 5 hour IM bike implies an average speed of 36 kmh, or 22.4 mph - or 52/16 at about 90 rpm, right in the middle of an 11-25 11sp cassette. A 24 minute 10 mile TT (25mph) would be in the 15 tooth cog, and would need to go to a 56t chainring to get back to the 16 cog in the middle of the cassette to maintain that 90 rpm cadence. So the case for a larger chainring is far less compelling for a IM bike leg than for a 10 mile TT.
In moving to an 11-30 or 11-32 cassette, you increase the jumps between cogs, and may end up in a less than ideal cadence trying to maintain your target power. Add to this the increased risk of a dropped chain with non-standard big ring/little ring combinations, and my advice would be to keep the 52 chainring and the tight cassette. Unless perhaps you are a huge “masher” and are currently doing IM bike legs at 75 rpm in the 13t cog??
I’m training for HIM and a FIM in Nov
What is the usual cadence for HIM and IM?
I think I’m going to slow in my cadence. My trainer rides average 73
First thing to remember here is that power makes you go faster - gear ratios are (almost) completely irrelevant to speed.
Some TT’ers do choose to run a bigger chainring, because that allows them to run a straighter chainline at typical speeds, which might get you 1-2 watts in efficiency. However, it is important to remember that “typical speeds” are much higher for say, a 10 mile TT, than they are for an IM bike leg.
A 5 hour IM bike implies an average speed of 36 kmh, or 22.4 mph - or 52/16 at about 90 rpm, right in the middle of an 11-25 11sp cassette. A 24 minute 10 mile TT (25mph) would be in the 15 tooth cog, and would need to go to a 56t chainring to get back to the 16 cog in the middle of the cassette to maintain that 90 rpm cadence. So the case for a larger chainring is far less compelling for a IM bike leg than for a 10 mile TT.
In moving to an 11-30 or 11-32 cassette, you increase the jumps between cogs, and may end up in a less than ideal cadence trying to maintain your target power. Add to this the increased risk of a dropped chain with non-standard big ring/little ring combinations, and my advice would be to keep the 52 chainring and the tight cassette. Unless perhaps you are a huge “masher” and are currently doing IM bike legs at 75 rpm in the 13t cog??
I’m training for HIM and a FIM in Nov
What is the usual cadence for HIM and IM?
I think I’m going to slow in my cadence. My trainer rides average 73
If that was your goal, then given your strength you should look for a used 130 mm bcd crankset that will work with your bottom bracket system. The small ring is generally 39 and the big is 53. Go to a gear calculator like Sheldon browns and see what gear you need to ride 24 mph at 75 rpms and see if the 53 will work, I suspect it’s plenty of gear for you.
All of us aging baby boomers are buying compact cranks, so selling your old one is easy
“What is the usual cadence for HIM and IM?”.
What’s your cadence when you are out training every day?
Can you even get a 54 in a 110 bcd crank?
No, he’d need to swap out to a whole new crankset
Yes you can. I’ve got 54 tooth Q and round Rotor rings. Also, Shimano doesn’t even make 130 BCD cranks any more so if they make a 54 it will be in 110. Probably SRAM also.
Rotor also sells a 56 tooth, 110 BC Q ring.
First thing to remember here is that power makes you go faster - gear ratios are (almost) completely irrelevant to speed.
Some TT’ers do choose to run a bigger chainring, because that allows them to run a straighter chainline at typical speeds, which might get you 1-2 watts in efficiency. However, it is important to remember that “typical speeds” are much higher for say, a 10 mile TT, than they are for an IM bike leg.
A 5 hour IM bike implies an average speed of 36 kmh, or 22.4 mph - or 52/16 at about 90 rpm, right in the middle of an 11-25 11sp cassette. A 24 minute 10 mile TT (25mph) would be in the 15 tooth cog, and would need to go to a 56t chainring to get back to the 16 cog in the middle of the cassette to maintain that 90 rpm cadence. So the case for a larger chainring is far less compelling for a IM bike leg than for a 10 mile TT.
In moving to an 11-30 or 11-32 cassette, you increase the jumps between cogs, and may end up in a less than ideal cadence trying to maintain your target power. Add to this the increased risk of a dropped chain with non-standard big ring/little ring combinations, and my advice would be to keep the 52 chainring and the tight cassette. Unless perhaps you are a huge “masher” and are currently doing IM bike legs at 75 rpm in the 13t cog??
I’m training for HIM and a FIM in Nov
What is the usual cadence for HIM and IM?
I think I’m going to slow in my cadence. My trainer rides average 73
I don’t think 70s cadences are unusual in tri. I think Jan and Lionel in their tribattle were mostly in the 70-75s.
What IS unusual is 90s and over for triathletes. Everyone always loves coming back to that 90 rpm figure, but several well-known coaches have straight up said it’s unrealistic for most of their athletes.
My own preferred cadence is 70-75, and even 65-70 feels fine for the most part. 90 feels crazy fast to me, and in fact, my power drops substantially when I’m going that fast for given effort.
It does vary greatly. I normally ride at 96-98 when on the road bike or on the trainer (road and TT). Road bike has fractionally longer cranks. But I’ve been biking way way longer than running and swimming and have leg length that will be in the top few percent - I’m 1.93m tall but disproportionally long legs and short spine.
Last couple of IM then I’ve been 88 and 89 rpm for 5:15/5:18 splits on 172.5mm cranks. In fairness the training cadence is a bit higher as the road surface for the race is abysmal chip seal and that means I end up spinning slower for some reason.
Edit To add: Same seasons, 2 months before IMs then my HIM was 94rpm each year on smoother surface and at +30watts to IM split (265w vs 235w).
Oh, and I use a 53/39 110 BCD quarq with shimano chainrings (DA outer, Ultegra inner) and a 12-25 10speed ultegra cassette.
Can you even get a 54 in a 110 bcd crank?
No, he’d need to swap out to a whole new crankset
Yes you can. I’ve got 54 tooth Q and round Rotor rings. Also, Shimano doesn’t even make 130 BCD cranks any more so if they make a 54 it will be in 110. Probably SRAM also.
Rotor also sells a 56 tooth, 110 BC Q ring.
Thank you, I’m stuck in the past I guess
I have a set of lightly used WickWerk rings in 34/53 (yes, that’s right, they planned it that way). They shift great, once you get the derailleur set up, which is tricky. Might be just the ticket for you.