Chainstay Length Discussion

[Daniel_Y]

Finally, a civil discussion about chainstay lengths on the internet. We have come so far!

As many people expressed, CSL cannot be talked about without front center, or a more generalizable variable: Rear Front Ratio (RFR):

From this thread: What are your driving dimensions and why? - #15 by Daniel_Y

rear-front ratio (RFR).

RFR = L2/L1

A quick derivation:

Rear wheel force: F1 = L2/(L1+L2) * Mg
Front wheel force: F2 = L1/(L1+L2) * Mg

The rear/front ratio is really easy to calculate because most of the terms cancel themselves out:

rear-front ratio: RFR = F1/F2 = L2/L1

I agree with a lot of the subjective and objective feelings that people have with chainstay length:

@liberationfab

I’ve also found shorter and stiffer stays to feel much more responsive sprinting at a higher cadence

Agreed. I think there are some weird effects here too:

• longer chain = more chain stretch under load
• more weight on the back tire = more direct feeling with the power transfer

@Brad

I almost exclusively ride single speed MTB and I believe my 419 CS is the biggest single improvement. I ride very rocky Midwest trails. This means steep short up and down.

Rocky, techy, punchy climbs do really well with short chainstays IMO. You get more rear wheel grip and can loft the wheel easily. This is why Steve at Hardtail Party likes super short chainstays in Sedona

@ElysianBikeCo

I chased short stays for quite a while thinking that it would help my road racing performance. Let’s say 2003-2019 or so. I thought it would help with being nimble in crits and with climbing/descending. Now, after listening to a lot of Josh Poertner, I realized things felt faster but probably, definitely weren’t.

I think one of the funnier Poertner podcasts was about the Placebo effect. If you feel faster and go faster, it is faster!

@manzanitacycles

Since the larger riders are used to riding a 1.9-2 ratio frame, it’s a hard sell to get them to commit to stays longer than 430-435 even if I try to convince them of the benefits.

Yup, 460mm stays are a hard sell when there is 10 years of “shortest chainstay possible” marketing to overcome! However, we are leading the charge!

@bushtrucker

I always wondered why they don’t use the term “backward geometry” to describe this approach haha. Would be very Riv.

Backward geometry for upduro racing!

@ben.land101

I’ve loved how rewarding it is to lean into the front of this bike and have it ask for more. Totally different tools for different applications.

Agreed. I think the super short chainstays makes sense with the PVD system: very long front center, super steep STA. That pulls your CG forward more than the CSL is shortened. Hardtail party Steve also sets up his very moderate Hummingbird like that:

• saddle slammed forward
• sized up a frame
• Mid-foot position

@terraformbicycles

We’re not speed demons, we go for 17-19km/h averages / 1,500-2,000m climbing, and comfort.

2000m of loaded climbing, no thanks!