46-30 chainset 10 speed on CAAD 8, any drawbacks to take into consideration ?

[Guitars and Bikes]

My caad 8 has the full 10 speed 105 5700 groupset with 50/34 chainset and 11-32 cassette. I was looking at the shimano grx 10 speed 46-30 chainset. Is it just a simple installation with front derailleur height adjust, and are there any in use niggles to be aware of when going as low as 46-30 ?
Thank you for any advice.

 

[Dogtrousers]

@rivers did this (swap 50/34 to 46/30) and a whole load of other stuff at the rear as well. See this thread, specifically this post: https://www.cyclechat.net/threads/mullet-drivetrain-conversion.285302/page-3#post-6732815

Unfortunately it's rather a bad tempered thread with lots of off-topic blather about triples but if you can skip over that it's worth a read.

If you decide to go ahead, do post about how it goes as I'm planning a similar move myself when my current chainset wears out.

 

[Jameshow]

My caad 8 has the full 10 speed 105 5700 groupset with 50/34 chainset and 11-32 cassette. I was looking at the shimano grx 10 speed 46-30 chainset. Is it just a simple installation with front derailleur height adjust, and are there any in use niggles to be aware of when going as low as 46-30 ?
Thank you for any advice.

I expect that the grx would have a wider chain line tbh. Need to check with someone.

 

[scragend]

I expect that the grx would have a wider chain line tbh. Need to check with someone.

I think it does. That said, I'm running the GRX 2x chainset with Tiagra 4700 10 speed on the back. I know that's not quite the same as the OP is proposing but when I was looking into it I did see that the GRX chain line is wider than the 4700 would be. But it works fine.

 

[neil_merseyside]

GRX 46/30 works just fine with 11spd 105 derailleur (7000 series) 11-34 on the back.

 

[Guitars and Bikes]

The q factor with the grx is 51mm as opposed to the 105 which is 45mm, could this lead to knee niggles ?

 

[Guitars and Bikes]

GRX 46/30 works just fine with 11spd 105 derailleur (7000 series) 11-34 on the back.

Do you know if it works smoothly with 10 speed 105 5700 ?

 

[dan_bo]

The q factor with the grx is 51mm as opposed to the 105 which is 45mm, could this lead to knee niggles ?

If you ride enough to notice, maybe. I'd suggest most wouldn't.

 

[davidphilips]

Just my view/take but if you just want to lower the gearing by about %10 then perhaps think about just swapping the cassette when its worn to a 13-34 or similar, even if you change the chainset, the 11 tooth ring on the cassette is very seldom used unless you race downhill like all the demons in hell are after you?

 

[Dogtrousers]

Just my view/take but if you just want to lower the gearing by about %10 then perhaps think about just swapping the cassette when its worn to a 13-34 or similar, even if you change the chainset, the 11 tooth ring on the cassette is very seldom used unless you race downhill like all the demons in hell are after you?

Or better still, do both.

Mind you 13-34 cassettes are harder to find than 11-34. So you might still end up with the teeny 11T sprocket

 

[Guitars and Bikes]

It says the usual hollowtech 11 bottom bracket won't fit due to grx needing 19mm spindle instead of 24mm. When I checked the shimano technical document it recommends a rs501 BB, when I checked its dimensions.....it says 24mm.....( bangs head off wall ) does a hollowtech ii BB for use with 19mm exist ?

 

[Jameshow]

https://bike.shimano.com/en-US/info...and-matching-shimano-grx-and-road-compon.html

Needs new front mech afaik...

 

[fossyant]

If its a 5702 rear it will do a 34 cassette. Running a FSA 46x34 chainset and a 11x34 cassette on my CX bike. Got me round a 130 mile Sportive with 10,000 ft of climbing including two 25% climbs, one after 40 miles, the other after 80. Thought about GRX but the chainline is slightly wider too but would have worked.

 

[neil_merseyside]

Do you know if it works smoothly with 10 speed 105 5700 ?

In theory with the chainline being slightly wrong the change should a bit poor but it really isn't. I think 10spd should be fine running on 11spd chain rings.

 

[scragend]

It says the usual hollowtech 11 bottom bracket won't fit due to grx needing 19mm spindle instead of 24mm. When I checked the shimano technical document it recommends a rs501 BB, when I checked its dimensions.....it says 24mm.....( bangs head off wall ) does a hollowtech ii BB for use with 19mm exist ?

Where did you see that GRX needs 19mm? It's 24mm as far as I'm aware - I'm certainly running an RS500 bottom bracket on mine!