S40 with longer chain stays

[Greg S]

I recently changed the chain stays on my S40 to 19" and thought others might find the "before" and "after" pictures useful in assessing the things that are affected by the longer stays. Note that the picture in front of the garage door with the 1x gearing is with the 17" stays.

Most obviously is that the crank itself is higher relative to the seat position - that's what I wanted. Also, the boom is flatter and for the moment the bars are bit closer. I've drawn a horizontal line (in red) beginning at the bottom bracket to illustrate the change in height. The distance from the front of the seat to the center of the bottom bracket is exactly the same in both photos.

Note that there are lot of other changes between the two pictures including different drivetrain, 650b wheels and handlebars but hopefully the pictures will still be useful illustration of the things that are affected by having the longer chain stays.

I've not been able to ride it since making the change. When I've got a few miles on it I'll add a ride report but that might be a while.

 

[Norton]

Nice bike thanks for posting!
Could you explain the drivetrain. Is that a twist grip for the gears?
Why the 650b's?
Whats the headrest did you make it?
I'm an older retired guy. Biked a lot in my earlier years and just trying to get back into it. I had a back operation in the late 80's and its never been the same. Diamond frame bike is killing my butt and back. So much has changed and I'm not very knowledgeable. So sorry for dumb questions.
I was all set to buy a Q45 (which I still may do) then got interested in the S40. Not sure if I will buy the stock setup or have a bike shop build up a S40 with my components of choice. I don't know much about group sets, wheels and such so trying to figure out what I would want.
Thanks I really like your bike!

 

[Greg S]

Hi @Norton, thanks for the complement on the bike!

The bike has Sram 11 speed grip shifters. The front crankset is a Shimano 50x34 compact crank and the rest of the drivetrain is Sram GX. When I bought the bike it had the stock Sram 1x drivetrain but I wanted more gears in both directions, i.e., an easier gear and a higher top gear. It's relentlessly hilly where I live so the easier gear helps on the climbs and with the higher top gear I don't spin out as soon on the descents. The cassette is an 11x42 so my top gear is a 50x11 and my easiest gear is a 34x42 which will get me up most anything.

I put the 650b's on for two reasons:

• I had them ;-) I build my own wheels and had a couple of sets that I'd built for another (diamond frame) bike that I sold. That left these wheels surplus so I thought "why not use them". Also, they're lighter than the stock wheels by about 1.5 lbs and lighter is almost always better on a bike ;-)
• The 650b wheels have a really nice, comfortable ride. I use 38mm tires on them which have the same circumference as 25mm 700c wheels so they perform and roll quite well.

The headrest is an Adem. I had a Bacchetta CA 2.0 (that I've sold) and bought it for that. The buyer for the Bacchetta didn't want it so I kept it.

I'm a relentless tweaker when it comes to bikes until I feel like I've got them "perfect" so I've ordered a Thor seat and headrest to try.

And no such thing as dumb questions.

 

[Casey Leonard]

So, what is the verdict? Did the longer chain stays make the double crank gear smoother/work better? I’m considering changing my 2020 to a double because I will run out of gears.

what 650 wheel set around $800 would you recommend?

 

[bladderhead]

Interesting to see the comparison. Did you change the boom length? Is it harder to lean forward or get on and off, now the bars are closer to your guts?

 

[bladderhead]

Not sure if I will buy the stock setup

I bought a frame but then I wished I had got a whole bike. You can immediately start riding it and getting the boom length right etc. You can replace the bits at your leisure.

 

[Greg S]

So, what is the verdict? Did the longer chain stays make the double crank gear smoother/work better? I’m considering changing my 2020 to a double because I will run out of gears.

what 650 wheel set around $800 would you recommend?

The double setup shifted well with the 17" stays so there wasn't really any change for the better or worse when going to the 19". I'm rather fanatical about smooth shifting, even the smallest screwups (not fully engaging in a gear, jumping a gear, making noise like it's trying to shift up/down, etc) really bother me. With that as backdrop, the shifting on the double is perfect. I've seen a lot of folks here say they prefer the 1x setup because they either couldn't get the 2x setup to shift properly or were afraid they couldn't. No issues here (SRAM GX 11-speed) and I think I could have accomplished the same thing with any other 2x setup, this is just the one that I happened to choose.

As to 650 wheelset, it's becoming more and more difficult to buy an "off the rack" 650b wheelset since they've all moved on to thru-axle vs the QR setup on my generation of the S40 (haven't looked at the new ones). I bought the Shimano GRX 650b wheelset ($419) for another bike and really like them but they're thru-axle. Wheels based on the DT-Swiss 240s can be converted from thru-axle to QR (the parts for the conversion come with the hubs) so those who build their own wheels (like me) can convert them to either setup. This is in fact what I did with the wheels I built, they have 240S hubs.

 

[Greg S]

Interesting to see the comparison. Did you change the boom length? Is it harder to lean forward or get on and off, now the bars are closer to your guts?

Yes, I changed the boom length and adjusted the handlebar position. I kept the "reach" to the pedals exactly the same and the distance between the handlebars and my chest close to the same (within an inch). It's probably obvious looking at the bike but the effect the longer stays have is to raise the cranks and "flatten" the boom i.e., the height of the bars is lower so they'll be closer to your hips/stomach. This isn't a problem for me, I'm still able to get on/off the bike easily as I'm fairly thin but it might be a problem for a heavier rider.