Gravel / Gravé / Gnarmac / Groad / ATB

I rode gravel bike to Brighton last week. Route here. Care: the 'chute to the A25' section is proper MTB territory although I managed it slowly on the gravel bike

https://www.strava.com/routes/7991374

Internet bike fit/gravel riding question.

I normally ride a 54 CAAD road frame with not much seatpost and very little standover clearance as the stack works for me. I've been thinking of making a switch to something more durable/comfortable and by chance my girlfriend has offered me her XS Datum as she isn't using it. Geo charts tell me stack is essentially the same but the reach is 18mm less on the Datum. Before i get excited and start trying to make it fit me i thought i'd ask the hive mind if it's a road(trail) to nowhere.

Looking at most the bikes posted here it seems like longer top tubes and shorter stems is the norm. The wheelbase on the Datum is still 10mm bigger then the CAAD but would i be at any significant disadvantage with a shorter top tube other than i'll need a longer stem which isn't ideal for getting rad? FWIW i'd be using 165mm cranks. Standover difference is 30mm but i would have thought that would be a good thing if i want to do sick jumps over bumpy stuff.

Sounds like the datum would be a good fit then if stack is the same and standover is smaller.

I ride a 110mm stem off road and it's more than fine.

So all depends how you want the bike to feel!

Id say you’re overthinking it but you might actually want a shorter reach anyway and therefore not need as long a stem as you think.

Plus dunno what width bars you ride on your caad but you could go 2cm wider bars for off-road which could warrant a 1cm shorter reach too anyway.

It was the compact crank until people taking too much drugs and spin too low an RPM in the late 90’s.

Put a stem that’s 20mm longer than standard and set at a positive angle, Job done.

anything more than 30/42 and you may as well walk, no?

Nope, MTBers been riding gears lower than that for ages.

I think you're referring to this post pre bladder/Hippy's new bike chat

As did cycle tourists.

The CTC ( as cycling UK once was) magazine contained many an article or letter on chainset ring combinations and how to achieve ever lower gears. Not all of the correspondence was as interesting as this thread is.
They were mostly about double chainset combinations though as until MTBs appeared, ie mid 80s, triples were exotica from France.

Id say you’re overthinking it

Absolutely, but 22cm of seatpost on a 46cm seat tube and a top tube that slopes well under the height of the back wheel is going to take some effort to get over. Still, i think i'll borrow a long seatpost and give it a go as i've never ridden a carbon road bike or one with hydro discs.

Even in the UK I do see old Dawes with 52/36 or 46/30, not common but does exist.

garbaruk says pretty specifically that the cages are only for the 1x grx rd. i was unaware of a way to extend the cage length of the grx 2x rd.

i've also run 50-34 x 11-40 for a number of years, first with mechanical using a roadlink at first and then a tanpan with an xtr sgs rd which worked pretty well. w/ di2 i used an rx rd and also the grx 2x rd. i think with all these setups except the tanpan you can tell that the rd is over capacity, and if you are descending chunky stuff while in the big ring + small cogs you get a lot of chain slap plus occasional chain drops which i can't help but think would be avoided by a longer cage rd + some extra tension.

garbaruk says pretty specifically that the cages are only for the 1x grx rd.

That might be because the RDs are physically different?

Another option is to transplant an XTR cage onto a GRX RD.

Well looky here, looks like someone has done it

https://www.youtube.com/watch?v=7kUxmkuJWNg

"The original RX812 rear shifting inner and outer plate are changed to the XT RD-M8000-SGS super long cage rear derailleur to support the front double-speed crank, and further support the rear derailleur to 11-46T. (The results will are like the attached video)"

This is cable but I guess you could do the same to Di2.

I've set my partner's bike up with my old Ultegra Di2 RD w/ Roadlink and 40T with 32T FSA crankset which was ok on the road but she's now got GRX RD because the chain slap was annoying when we went gravelin'

Just get a gearbox

and stop pedaling to shift?

Just get a gearbox

I hadn't planned on changing the thread title today

Seriously tho, can you depict a ride where you'd need both a 50x11 gear ratio and a 34x46 considering a cadance range of 70-120?

GRX crankset 46/30 + 11-40 cassette would be plenty for most situations I'd imagine

I don't have 50x11, I have 46x11 and I don't really want the 11T but that's where we are with cassettes for the most part (I've previously built custom cassettes that pushed the whole range away from 11T).

Yes, I can. Multi-day, loaded gravel rides: An Turas Mor, Badlands, Seven Serpents, Iberica Traversa, Spirit of Girona if you were silly enough to ride a gravel bike and any other tour where you're doing road and/or gravel mountains. Even pure road rides like ALPI4000 or Mille du Sud or Pendle 600 I've used my entire gear range and would've quite happily taken a lower gear.

Seriously tho

You’ve just armchair questioning someone who done quite possibly the hardest road/gravel races on the forum (excluding skinny).

Haha

Yeah! You tell him, Ed! :D

He's also fat, so the gears that work for spindly little climbers don't necessarily suit a big guy who likes to spin.

someone who done quite possibly the hardest road/gravel races on the forum

Can confirm, hippy has survived a 3 hour ride around Epping Forest

That was on a singlespeed. So that's not helping my argument :P

It helps to confirm my theory that bikes need either ALL THE GEARS, or just the one

No half measures