# Ultegra and 105 compatibility **URL:** \ **Category:** Equipment\ **Created:** [March 23, 2019, 1:42pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724 "2019-03-23T13:42:26Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![shafwaan](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/shafwaan/32/9531_2.png) [@shafwaan](https://www.trainerroad.com/forum/u/shafwaan)\ **Post date:** [March 23, 2019, 1:42pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/1 "2019-03-23T13:42:26Z")
Wondering if somebody could shed some light - I need to replace a left crank arm due to damage. My chainset is 105 5800 170mm and looking through ebay there are a few ultegra 6800 170mm left hand cranks available. Will these fit? Thanks in advance ---
**Author:** ![mcneese.chad](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/mcneese.chad/32/15056_2.png) [@mcneese.chad](https://www.trainerroad.com/forum/u/mcneese.chad)\ **Post date:** [March 23, 2019, 1:44pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/2 "2019-03-23T13:44:57Z")
Perfect fit, no issues at all. ---
**Author:** ![cyclhist](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/cyclhist/32/14840_2.png) [@cyclhist](https://www.trainerroad.com/forum/u/cyclhist)\ **Post date:** [March 23, 2019, 1:46pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/3 "2019-03-23T13:46:03Z")
> [@shafwaan](#): > > Wondering if somebody could shed some light - I need to replace a left crank arm due to damage. My chainset is 105 5800 170mm and looking through ebay there are a few ultegra 6800 170mm left hand cranks available. Yes, they’ll work fine as both are (afaik) 11-speed setups from the same generation. Mixing different generations can be more complicated and Shimano doesn’t support mixing 10 and 11-speed setups although anecdotally even a 5700 transmission and an ultegra 6800 crankset work fine. ---
**Author:** ![shafwaan](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/shafwaan/32/9531_2.png) [@shafwaan](https://www.trainerroad.com/forum/u/shafwaan)\ **Post date:** [March 23, 2019, 2:54pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/4 "2019-03-23T14:54:21Z")
Thanks for the advice, much appreciated! ---
**Author:** ![themagicspanner](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/themagicspanner/32/129528_2.png) [@themagicspanner](https://www.trainerroad.com/forum/u/themagicspanner)\ **Post date:** [March 23, 2019, 3:21pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/5 "2019-03-23T15:21:07Z")
Every generation of HollowTech crank arms are cross-compatible as the splines haven’t changed, to the best of my knowledge. The left arm isn’t exactly what you’d describe as ‘speed specific’. Mike ---
**Author:** ![cyclhist](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/cyclhist/32/14840_2.png) [@cyclhist](https://www.trainerroad.com/forum/u/cyclhist)\ **Post date:** [March 23, 2019, 4:27pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/6 "2019-03-23T16:27:30Z")
> [@themagicspanner](#): > > Every generation of HollowTech crank arms are cross-compatible as the splines haven’t changed, to the best of my knowledge. The left arm isn’t exactly what you’d describe as ‘speed specific’. My bad. I read this too quickly. I thought he was going to take this opportunity to upgrade the crankset. 🙂 Detention for me! ---
**Author:** ![themagicspanner](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/themagicspanner/32/129528_2.png) [@themagicspanner](https://www.trainerroad.com/forum/u/themagicspanner)\ **Post date:** [March 23, 2019, 5:47pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/7 "2019-03-23T17:47:15Z")
I do that all the time. Mike ---
**Author:** ![RobertSims](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/robertsims/32/26170_2.png) [@RobertSims](https://www.trainerroad.com/forum/u/RobertSims)\ **Post date:** [March 23, 2019, 7:48pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/8 "2019-03-23T19:48:31Z")
No problem at all. ---
**Author:** ![Nicleza](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/nicleza/32/66829_2.png) [@Nicleza](https://www.trainerroad.com/forum/u/Nicleza)\ **Post date:** [September 22, 2020, 6:03am UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/9 "2020-09-22T06:03:24Z")
Re-cycling this thread: My big Chain ring is worn and needs to be replaced. It’s a 105 5800 chainring and crank arm. Would an Ultegra chainring fit? ---
**Author:** ![mcalista](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/mcalista/32/92377_2.png) [@mcalista](https://www.trainerroad.com/forum/u/mcalista)\ **Post date:** [September 22, 2020, 6:05am UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/10 "2020-09-22T06:05:21Z")
6800 would. Not R8000, as it is a 4 bolt pattern versus the 5 bolts of 5800/6800. ---
**Author:** ![duje.jelaska](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/duje.jelaska/32/7721_2.png) [@duje.jelaska](https://www.trainerroad.com/forum/u/duje.jelaska)\ **Post date:** [September 22, 2020, 6:46pm UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/11 "2020-09-22T18:46:36Z")
5800/ 6800 are 4 bolt as well, but won’t fit bc the inner chainring on r8000 series moved inboard ever so slightly. ---
**Author:** ![Nicleza](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/nicleza/32/66829_2.png) [@Nicleza](https://www.trainerroad.com/forum/u/Nicleza)\ **Post date:** [September 25, 2020, 3:48am UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/12 "2020-09-25T03:48:58Z")
But 105 5800 is compatible with Ultegra 6800, right? ---
**Author:** ![markryd](https://sea2.discourse-cdn.com/trainerroad/forum/user_avatar/www.trainerroad.com/markryd/32/6191_2.png) [@markryd](https://www.trainerroad.com/forum/u/markryd)\ **Post date:** [September 25, 2020, 5:32am UTC](https://www.trainerroad.com/forum/t/ultegra-and-105-compatibility/13724/13 "2020-09-25T05:32:27Z")
Yes. And I’ve done exactly this, fitted an 6800 large chainring to a 5800 crankset.