long stems, new/progressive geometry & weird stuff

Since my 29er fork is in the shop, I'm back on my old 26er today

originally it had a 700mm bar 90mm stem, but had changed things around for a co-worker to ride, with a 760mm bar and 50mm stem.

I didn't bother to change back this morning to original bar/stem and went for a ride, and found the front end really light and squirrelly, like it had very little trail

so this afternoon just changed back to the long stem and kept the wide bar and found the steering much more stable

Both my 29er and 26er have 69 degree head angles and equivalent rake/offset for similar trail, and if anything a heavier front wheel/tire on the 26er

I'm thinking why not have slacker head angle, corresponding shorter top tube and with a longer stem, so that the front centre and saddle to handle bar reach wouldn't change, and you wouldn't have to reduce rake/offset (with increased wheel flop) to keep the front centre from getting to long. Or go for both slacker head angle with a long stem >50mm rake/offset and resulting longer front centre for even more stability without resulting wheel flop

So for every degree slacker head angle the stem should be ~10mm to 20mm longer (depending on if you are measuring to the axle or the imaginary head tube angle to ground point) to keep relationship of hand position to tire contact point relatively the same

Or in other words, for the same front centre, a slacker head angle with longer stem and shorter top tube would feel more stable and with less wheel flop

No. Just get a longer frame that puts you in a proper riding position with a 50mm or so stem. The longer stem slows steering input but doesn’t really make a bike stable. Head angle and trail are what make a bike stable or twitchy more so than stem length and bar width although those do affect handling too. I mean road bikes genearally have long stems plus the reach of the bar and hoods and road bikes are way way more nervous than a mountain bike.

The problem with short reach long stem bikes comes when you’re descending steeps, on the brakes and you move your body rearward in relation to the front contact patch to keep from going over the bars, and this places more weight on the back tire, less on the front so traction on the front suffers. Pretty sure this is why Cancellara crashed out of the London Olympics. If bikes are too short it is harder to keep your weight between the wheels. A common comment when 29ers started getting popular was the riders felt more in the bike rather than on top of the bike. Bigger wheels demanded longer stays and longer front centres. Weight was more easily kept between the wheels.

so longer frame with 66 degree head angle and 50 mm stem vs longer frame with 65 degree head angle and 65 mm stem?

Posted by: taprider

so longer frame with 66 degree head angle and 50 mm stem vs longer frame with 65 degree head angle and 65 mm stem?

You’ve been drinking Rod.

50mm stems are long imo