I currently ride on a SRAM red 22 crank (53/39) with 172.5mm crank arms. Having biked a fair share the last few years it is about time for a change. I would like to try 170mm arms and thus I am looking for a new crank. Unfortunately I am quite ignorant when it comes to the handy department so would anyone help me with
a) telling me how to find out what type of bottom bracket I have
b) how I can check for compatibility with other SRAM cranks (or give me a suggestion to a 53/39 crank with 170mm arm that would work just fine), and
c) Sell me on why I should choose/not choose 170mm
I currently ride on a SRAM red 22 crank (53/39) with 172.5mm crank arms. Having biked a fair share the last few years it is about time for a change. I would like to try 170mm arms and thus I am looking for a new crank. Unfortunately I am quite ignorant when it comes to the handy department so would anyone help me with
a) telling me how to find out what type of bottom bracket I have
b) how I can check for compatibility with other SRAM cranks (or give me a suggestion to a 53/39 crank with 170mm arm that would work just fine), and
c) Sell me on why I should choose/not choose 170mm
I am 6.3/191cm
For question a), you will need to determine if the existing crank and bottom bracket is GXP or BB30 type. If there are no markings, you can remove the non-drive side crank arm and measure the spindle diameter. GXP will be 22mm. BB30 is 30mm. Once you’ve identified the diameter, you can source a compatible crankset. This is the simplest approach but it limits your choices in cranksets somewhat.
If you also need to replace the bottom bracket, you would use same type, whether GXP or BB30.
If you find a can’t miss deal on a crankset that requires a different BB than what you have, then more information on your existing bottom bracket and specific bike model is necessary to make sure the new BB is compatible with your frame and crankset.
Thanks David. Will have a look at it. Haven’t found a crankset yet but have started to look for one. Is everything that isn’t called GXP compatible with BB30?
@Jim: TT bike! My bad, I am doing long distance triathlon. I am quite a lot better on a road bike than on a TT bike. It feels like the upper part of the quad is too weak. Could be from riding too little in the TT position but I am thinking that a lower top point will make the hip angle slightly better. Thoughts?
Thanks David. Will have a look at it. Haven’t found a crankset yet but have started to look for one. Is everything that isn’t called GXP compatible with BB30?
@Jim: TT bike! My bad, I am doing long distance triathlon. I am quite a lot better on a road bike than on a TT bike. It feels like the upper part of the quad is too weak. Could be from riding too little in the TT position but I am thinking that a lower top point will make the hip angle slightly better. Thoughts?
Any crankset you look for will say whether it’s GXP or BB30 compatible if you are staying in the SRAM world. For example:
As mentioned by the poster above, the spindle diameter is the key difference (22/24mm for GXP; 30mm for BB30).
If you start shopping in Shimano world, then the crank spindle diameter will be a constant 24mm and not compatible with your existing BB, regardless whether it’s GXP or BB30.
So in that case your frame is BB86. If you need to buy a new bottom bracket, keep that in mind. For reference, this refers to the size of the cavity in your frame that the BB is pressed into.
As for cranks, you probably won’t see much of a difference between 172.5 and 170. If you’re looking to downsize, than I’d highly recommend looking at 165. Do you have a crank based power meter you’ll want to keep? Do you want a crank based power meter for the new cranks?
And as the other posters said, look into what crank spindle diameter you have. Should be able to make it work with your current BB either way.
The crank has started to squeak so I was actually considering swapping the bracket out as well. Dunno how long you can ride on a crank before a change is recommended. No power meter though. I use favero Assioma.
I have been considering 165 but I am afraid that will be too short. I am going to Spain for 3 weeks in April and will race twice down there so thought 170 was a safer option. Any experience with 165 yourself? At 191cm with the majority being legs I feel (without any good argument) that 165 could be too short
Life of a BB is pretty hard to predict, usually I just pull my crank every so often and feel how smooth the bearings are. No real harm in replacing it though, esp if you get something like a wheels manufacturing thread-together bb. Not only are those serviceable, so you’ll never need to buy another, but they eliminate most pressfit BB creaking.
Personally I ride 155mm cranks on the tt bike, 162.5mm on the road bike and 170mm on the gravel bike. I’m 180cm though. For a tt bike, there really is no such thing as too short so I suspect you’ll be OK there as long as you adjust your saddle appropriately, up a little and back a little. That’s kinda where it depends on you though. All I’m saying is the difference between 172.5 and 170 is negligible, and if that’s all you want than save your money.
Hey. Finally came around to ask my LBS to find new cranks for me. They had a good deal on a 167.5mm Durace and I got it yesterday. First session I gained 20w so thanks for the help! I hands down didnt think it would feel so much better.I feel that I should have gone with 155mm but that will be next years free gains :))
