I’m in the process of putting together my new TT bike for next year (a 2020 Giant Trinity).
I’m going to go 1X, but was wondering if I’ve missed any crank/chainring options.
I’ll be running Shimano 11 speed Di2 with an 11/34 cassette and a 48T chainring.
After a lot of searching, there’s not much choice for a TT bike.
Kind of narrowed it down to the SRAM Force (or Red) Aero offering or some of the new ROTOR modular stuff (Aldhu cranks, solid aero mas spider and associated ring).
I want it to look good though and love the look of a solid ring like the SRAM 12 speed 48t rings.
Pat.
I think all the solid TT-style rings are bigger than 48t. I’d suggest getting a 48t 1-speed ring and then using the flat carbon crank cover from Alden Designs.
A 48x11 is a pretty horrible choice for gearing. If you need a 48x34 to get up a hill, you are going to want something much bigger to get down. That gear will also be useless in a tailwind.
The other thing you want is to keep the chain line as straight as possible to reduce friction, so your cruising/TT gear should fall in the middle of the cassette. That would be something like a 48x15-17, which is probably a 20 mph speed at a reasonable cadence. This is why the 60 tooth rings are popular on the UK TT scene. A 60x15-16 puts them in in the high 20 mph range with a minimum amount of friction.
Companies like Pyramid Cycle Designs and AeroCoach make all sorts of custom rings to fit just about any crank. I would look at the Metron aero crank and talk to one of the UK companies about appropriate gearing. You may want a longer cage rear derailleur and run an even wider geared cassette to get into a reasonable sized chainring.
A 48x11 is a pretty horrible choice for gearing. If you need a 48x34 to get up a hill, you are going to want something much bigger to get down. That gear will also be useless in a tailwind.
As always, it depends. A 20-23mph IM is not the same as a 28mph 40k. I have a 11-32 cassette and think it’s a good compromise for small jumps and wide range (especially the Rotor 11-32). If you’re going downhill at 40mph, the watts you’re putting into the pedals won’t make as much difference as they do at 20mph. At that point I’m happy to spin out and coast/rest.
Since he referenced the Sram 1x cranks in the original post, I assumed he didn’t want to buy a new crank. I believe those rings only work as direct mount on Sram 8 bolt arms.
A 48x11 is a pretty horrible choice for gearing. If you need a 48x34 to get up a hill, you are going to want something much bigger to get down. That gear will also be useless in a tailwind.
Not everyone has the same gearing needs as strong UK TTers that are averaging in the high twenties to low thirties mph. 48 x 11 gives you 34 mph at 100 rpm and 37.5 mph at 110 rpm. For the majority of triathletes, that’s a good enough high gear and at speeds higher than that it’s better to coast and save energy, especially in long course. He’s also running shorter cranks, which raises the effective gearing. 48 x 11 at a 165 crank length is a bit higher gear than 50 x 11 with 172.5 cranks, and the shorter cranks make it easier to spin a higher rpm. Your solution with the wider cassette will sacrifice closer gearing steps for a high gear that won’t be used much. I get the point about friction but again when you’re going slower and putting out less power, you’re not going to be using the smallest cogs even with his setup.
x2; the crank itself isn’t the limiter here. But, wide/narrow tooth chainring options are slightly limited although still plenty of options. Sram, rotor, wolf, aerocoach, probably some others too. How many options do you really need???Those companies all make really nice 1x products.
48x11 isn’t that bad of a gear. Yes it’s a bit small, but not that bad. For a 40K time trial with a strong rider, maybe not the best choice, but for an Ironman or 70.3 I bet it would work for 90% of the population. I run a 50T front with either a 11-32 or 11-36 depending on the course. I’m planning on going to the SRAM etap 12 speed 46T front and 10-33 on the rear. That equivalent of a 50x11 and a 50x36 so pretty good.
The ideal is the 9-32 of the 3T cassette, but it won’t work on the speed concept as it hits the chainstay in the 9T cog.
I’m a UK short and long course triathlete and often at the sharp end of my age group.
I’m used to racing with a 53/39 and an 11/28. Seems to cover just about every hilly race including IMUK.
The 48t (SRAM do a solid chaining) with an 11/34 is pretty close to my 2X set up.
Yes, I’d loose my high gear, but not as much as you think. Its similar to the 53 and 12 combo and it’s quite rare to be spinning out the 53 and 11 anyway. In reality, I rarely used the 11 on the old set up. Much more productive over 30 mph to pull right into the aero position rather than waste my running legs.
Since he referenced the Sram 1x cranks in the original post, I assumed he didn’t want to buy a new crank. I believe those rings only work as direct mount on Sram 8 bolt arms.
The sram 1x Force comes with the 48 tooth solid and I’ve been told the 50 tooth solid works on the Force also. Is this correct?
Why not go for SRAM 12 speed and a 10-33 or 10-28 cassette depending on the course.
Having the 10 instead of 11 as the smallest cog really helps with the higher speed stuff.
You could also have alternative size chainrings depending on the course as they are relatively easy to change.
If you want it to look good it makes sense to go all SRAM rather than a mix.
I have been using a sram 50T and 11-32 for a while now…it’s been a really easy adjustment…I like it enough that I ended up putting it on my road bike as well.
I just got a “Stone” narrow wide chainring for my Ultegra R8000 crank on aliexpress and I’m happy with it (link here). I like that I can continue to use my shimano crank without resorting to buying a whole new crank and BB.
Since he referenced the Sram 1x cranks in the original post, I assumed he didn’t want to buy a new crank. I believe those rings only work as direct mount on Sram 8 bolt arms.
The sram 1x Force comes with the 48 tooth solid and I’ve been told the 50 tooth solid works on the Force also. Is this correct?
Yes, they are direct mount chainrings that attach directly, with no spider, to current SRAM Dub, and some older SRAM, crankarms with 8 small torx bolts. Older Force used a 3 bolt interface and are not compatible. He’ll also need a new Dub bottom bracket. (Although Speed concepts require GXP crankarms & BBs as the BB90 BB is not compatible.)