Custom gravel bike - chainstay length, opinions wanted!

[vespasianus]

I have 437 mm chain stays and love it. Long stays, but with road bike angles is a great setup in my mind and gets you that nimble gravel/adventure bike you want.

[polyhistoric]

I have a Seven Evergreen with modified CX/gravel geo - pretty old, 2014. Clearance is limited to 40 in the back, but runs 442 cs with a 7cm drop. Front end is pretty traditional with a 71.5 headtube angle and 47mm rake fork. I don't notice the cs as any limitation on any road or flat gravel. In a CX race or tight, twisty singletrack it definitely slows down the handling with the extra wheelbade - it doesn't want to pivot. On a rocky, rutted loose and fast downhill, it bombs and is so stable (overconfidence).

I would say it depend on your riding needs and desired trait. Ask Kevin at FF, I bet he has some right answers on the question.

[Alistair]

Originally Posted by rothwem

As for clearance, this is really personal, but I think 45 is all I think I'd really need. My current frame only has room for 40's and its fine, but I'd like to be able to fit 42s because it seems like a lot of good gravel tires are made in that size and I love having access to a big selection of tires.

Some of the gravel pros in the US regularly use 2"-2.3" mountain bike tires for select races. And several rolling resistance tests indicate the RaceKing or ThunderBurt (in their fastest casing material) are faster than most of the 40mm gravel tires. But, at that point it's definitely optimizing handling/traction vs RR vs comfort/fatigue vs aero. And for most of us, the differences will be lost in the noise of our own inconsistent performance and poor aero.

For me, I have a hardtail I can use for chunkier gravel, so I'll stick to 40mm or 45mm for now. But, if I were spending big bucks on a custom bike, I'd want the option to go wider.

[nmrt]

This is a great point by John H.
5 mm is not a lot. But how do you want the bike to ride? A 430 mm CS and an accompanying high trail in the mid 60s will make the bike NOT ride like a zippy road bike if road-bike-handling is what you are after.

But if you're after a "traditional" gravel bike a 430 mm CS is okay. For me, anything more than a 430 mm CS, and it turns like a "semi truck.".

Originally Posted by John H.

5mm (in isolation) will not be a negative- But what is the design of the rest of the bike? Head angle, bb drop, front center?
Point being, if the bike is designed to be road bike-ish and snappy- Going all the way to 50mm tires may not handle great.

Some folks try to stuff to many feature and variables into a custom bike. Because you can, doesn't always mean you should.

[weisan]

You can spec for 40-45mm 700cc tires but if you use 650b wheels, you might be able to use wider tires in the 2.1-2.3 range without changing the CS length.

[buddybikes]

You're paying big $$ for doctoral expertise in frame design and building. Tell them what you want for importance, let them do design

[Mark Davison]

My MAP rando bike has 440mm chain stays. The handling is very snappy if you pump up the 650B x 42 tires to the ReneHerse recommended firm setting. Much of the received wisdom about chain stay length seems dubious to me.

My Specialized Diverge has 425mm chain stays. it feels snappy on 650B x 42 and somewhat truck like on 700C x 44 with aluminum rims. I think gyroscopic effects may have more effect on the handling feel then 1.5cm in CS length.

For a tall frame longer chain stays make it easier to climb steep pitches seated, without having to bend forward so much to keep the front tire planted.

[Wunder]

Originally Posted by solographik

Funnily enough, the clearance w/ 650bs does not change w/ chainstay length (i think due to how the rest of the rear triangle is set up. It'll clear 650x53mm with either a 425mm or 430mm stay.

I do have a set of nice 650bs but i think i see myself using the 700s more...I guess the other way to think about it is if i do need the extra clearance, to just run the 650s...argh!

The 650 clearance doesn't change with chainstay length because it is determined by the width of the stays which doesn't change. The Cervelo Aspero for example will do a 650x47 or so and 700x40 with only 420mm stays. I'd er shorter and tighter personally. In theory a 650 wheel should also be more nimble and handle correclty if using monster tires (total inflated wheel diameter about the same).

[solographik]

Originally Posted by buddybikes

You're paying big $$ for doctoral expertise in frame design and building. Tell them what you want for importance, let them do design

Yeah, i've spoken to Kevin over at FF a lot (and he's been very patient). Ultimately what it comes down to (and as others have mentioned in the thread) what the bike is meant to do.

It's going to be used for adventuring a lot more frequently than a cross race, and I have my road/allroad bikes for when I need to ride pavement. Talking to myself now here - it seems that the extra stability and tire clearance would be the way to take it.

[Hilltopperny]

Originally Posted by solographik

Yeah, i've spoken to Kevin over at FF a lot (and he's been very patient). Ultimately what it comes down to (and as others have mentioned in the thread) what the bike is meant to do.

It's going to be used for adventuring a lot more frequently than a cross race, and I have my road/allroad bikes for when I need to ride pavement. Talking to myself now here - it seems that the extra stability and tire clearance would be the way to take it.

Kevin definitely knows his stuff! If the bike is for adventuring than I say go for the longer stays. I have a Baxter adventure bike and it has some really long stays on it. I have it set up with 48mm Rene Herse endurance casings tires as well as a Fox SC32 100mm fork and it is a ton of fun. It climbs as good as anything and still handles very well on single track and over rough terrain.

[muttley]

I really like the shorter chainstays but I prefer a gravel bike with more road oriented geometry.

I currently have two gravel bikes, a Cervelo Aspero (420CS) and a Giant Revolt (425 CS). Both have what most would consider shorter chainstays, I feel like I can feel the difference at least with these two frames that have different geometry. The Aspero is truly is a road bike with gravel bike tire clearance. In that respect it's a perfect Road/All Road bike and Gravel bike for me. I love this bike running 2x with road pedals and 36c Challenge Strada Bianca slicks and make sure to hit local singletrack and mountain bike trails in this configuration.

The Revolt feels like a true gravel bike to me and while the 425 chainstays dont' feel short, they don't feel long either. The slack HT angle and compliant layup make this bike feel right at home in any dirt terrain.

Ask 10 people and you'll likely get 11 opinions on chainstay length. For me the shorter the better.

[GonaSovereign]

If you want a lively bike, shorter is better...and 425 is good.
I'd also trust the Seven (or FF) people to deliver if you tell them what you're looking for.

[.RJ]

Originally Posted by solographik

Will the rear end be noticeably more sluggish with a 5mm longer chainstay? My initial thought was that the increased tire clearance would open up a lot more options for tires (in the 47-48mm range) that would help keeps more plush on longer rides, though I don't expect to run things bigger than a 42-45mm normally.

I guess that depends on what you're gonna do with it. If you plan on doing long rides while loaded, some extra chainstay and tire would really help there. If you're never going to do that, I'd opt for shorter, even shorter than 425 if they can swing it. And, what are you doing with the front of the bike? Long and low (go longer), or short and snappy like a CX bike (go shorter)?

45's are great, so does going to 50mm really open up more options that arent available in 45mm? I dont think things really change until you start getting into 55mm which makes fast rolling XC mtb tires an option.

[mstateglfr]

I have 430mm chainstays on my gravel bike and have yet to come upon a time where I raised my fist in the air and cursed the gods for not giving me 425mm chainstays.

72.5deg hta, 50mm fork offset, 44mm actual width tires = 60mm trail. <--- just other geometry that might allow that 'mutumbo-esque' 430mm chainstay design to still make the bike feel fun.

[Andy340]

Originally Posted by Mark Davison

My MAP rando bike has 440mm chain stays. The handling is very snappy if you pump up the 650B x 42 tires to the ReneHerse recommended firm setting. Much of the received wisdom about chain stay length seems dubious to me.

My Specialized Diverge has 425mm chain stays. it feels snappy on 650B x 42 and somewhat truck like on 700C x 44 with aluminum rims. I think gyroscopic effects may have more effect on the handling feel then 1.5cm in CS length.

For a tall frame longer chain stays make it easier to climb steep pitches seated, without having to bend forward so much to keep the front tire planted.

I had same experience when I switched 700c x 35mm wheels with heavy deep alu rims for 650b x 47 mm on my Niner RLT steel: went from very sluggish to neutral (perfect for me), would probably feel more snappy with 650x42 combination