Seat Surprise (WTF?)

[Kayakguy]

After pedaling to my "Silver Sneakers" walk this morning, I mounted up for the return, noticed my seat felt wonky, and was startled to see it fall to the pavement. Had to walk the bike a mile or so to get it home. So glad it wasn't farther, and that it didn't happen in the middle of a busy intersection. The cause? A broken seat bolt.

So how did this happen? My guess is that, because I have set the seat back as far as possible (for irrelevant reasons having to do with making it fit me and my riding style), this made it function as a cantilever, which put a strain on the seat bolt, which eventually fatigued and sheared off. I fortunately had spare seat mounting hardware at home, and was able to fix it in the shop.

But now I'm thinking about how embarrassing that could be if it were to happen again in the middle of an intersection. One way to avoid a future occurrence would be to use a larger bolt. Since the seat mounting bits are aluminum, it should be easy to drill out and tap for a larger bolt (I'm guessing it's metric, though it looks a bit bigger than 6 mil. but smaller than 8 mil.) I also think it would be wise to use a hardened bolt, grade 5 or 8, as these are much tougher than standard ones. My local hardware store has these, and when re-tapping the hole I can go SAE or metric as needed.

I'll report on how this works out after I've done it.

 

[rich c]

Are you sure someone didn't try to steal it? Our son rode a clunker to his train station each day. Came home one day to see the seat missing.

 

[Viking1]

Try a grade 8 bolt as a replacement. Lots more sheer strength.

 

[Kayakguy]

Are you sure someone didn't try to steal it? Our son rode a clunker to his train station each day. Came home one day to see the seat missing.

No. If they had wanted to steal it, all they had to do was lift it off and walk away with it.

 

[Kayakguy]

Try a grade 8 bolt as a replacement. Lots more sheer strength.

Yes, as I already said I would do.

 

[Stefan Mikes]

@Kayakguy: Such a failure can happen and it does happen.

Once, I gave my traditional bike as a gift to a friend. He is quite an irresponsible person and he was using that bike (with V-brakes!) for crazy road downhill rides. On one of his rides, the seat bolt broke; fortunately for him, it happened at low speed on the flat. Of course, he blamed me for giving him a broken bike!

Also, once the saddle rail broke on my Vado. Again, I was fortunate as that happened when I just started the ride.

I attribute both failures to fatigue, and possibly it could be the outcome of overtightening of the bolts.

 

[Kayakguy]

@Kayakguy: Such a failure can happen and it does happen.

Once, I gave my traditional bike as a gift to a friend. He is quite an irresponsible person and he was using that bike (with V-brakes!) for crazy road downhill rides. On one of his rides, the seat bolt broke; fortunately for him, it happened at low speed on the flat. Of course, he blamed me for giving him a broken bike!

Also, once the saddle rail broke on my Vado. Again, I was fortunate as that happened when I just started the ride.

I attribute both failures to fatigue, and possibly it could be the outcome of overtightening of the bolts.

Overtightening of the bolt did occur to me as a possible factor. Another reason to use a grade 5 or 8 bolt (hardened, and much tougher).

 

[indianajo]

There is a lot of **** that looks like steel from a certain country. Most bike parts come from there. Vendors can buy decent parts from ***** but they have to run an incoming inspection department to catch the garbage coming in the door.
The bolts & nuts at Orscheln TSC and Rural King farm supply come from the same country, but I haven't gotten any **** from them. I'd use grade 5. Grade 8 has enough carbon, I've broken some subject to vibration.

 

[Kayakguy]

I have to confess, I was unaware of any functional differences between grade 5 and grade 8. So my local hardware store (Hardware Sales in Bellingham, probably the best stocked hardware supplier in the USA) had 8 mm bolts in both grade 8 and 5, so I got the grade 8. It was a bit long, which meant trimming off 1/4" with the angle grinder, and I put the seat back on. The bolt has a washer-head hex head, but I doubt anyone will notice it. Now I have to carry a 13mm combo wrench in my gear set for any adjustments and fine tuning that might be necessary.

I briefly considered a stainless bolt (for the rust resistance), but from experience I know that stainless can shear off quite easily.

 

[Rich W.]

There has been counterfeit graded hardware from China sold in the US for decades. For anything that matters I check the source.

 

[mschwett]

steel screwed directly into aluminum, exposed to the elements? I’m hoping/guessing the aluminum part is much larger than the steel fastener, and that you keep it away from salty water, or even water, because otherwise this seems a recipe for galvanic corrosion.

zinc coated steel at least?

 

[Viking1]

Good job! Sounds like you took care of it and I feel the grade 8 was your best choice, excellent sheer strength for your application.

 

[Jeremy McCreary]

So how did this happen? My guess is that, because I have set the seat back as far as possible (for irrelevant reasons having to do with making it fit me and my riding style), this made it function as a cantilever, which put a strain on the seat bolt, which eventually fatigued and sheared off. I fortunately had spare seat mounting hardware at home, and was able to fix it in the shop.

But now I'm thinking about how embarrassing that could be if it were to happen again in the middle of an intersection.

Read this with some alarm, as my seat's also cantilevered all the way back (to eek out a little more extension for my cranky knees).

Don't even wanna think about the seat coming off while I'm on it.

 

[mschwett]

Read this with some alarm, as my seat's also cantilevered all the way back (to eek out a little more extension for my cranky knees).

View attachment 146727

Don't even wanna think about the seat coming off while I'm on it.

do they not make suspension seatposts with setback?

 

[Jeremy McCreary]

do they not make suspension seatposts with setback?

Maybe so, but I didn't know enough to look into that at the time. Now that you've given me the search term "setback", I'll look again.

That seat and Suntour post came with the bike. Putting the seat all the way back got me just enough extension to fend off a knee uprising, so I stopped there. With the OP's cautionary tale, time to revisit.

 

[Stefan Mikes]

(to eek out a little more extension for my cranky knees).

Jeremy, if you need some relief for your knees, just raise the seatpost a little. The rule of thumb is: If you can fully extend your leg while resting your heel on the pedal (in the downward position of your extended leg); and when your knee is slightly bent when you place your foot on the pedal normally, then it is the proper seat-post height.

You do not control the leg extension with the saddle "setback". The saddle set back is for increasing the "reach" of your arms on the handlebars. I use Kinekt or ShockStop seat-posts on my e-bikes; these allow to control the saddle setback (as any normal seat-post does), and I have my saddles in the most backwards position allowed as I need a lot of reach on my frames. (I think my arms are long).

In the seat-posts I own, the saddle rails are secured with two bolts (each bolt for a side). Did the OP mention the seat-post brand and model? Some seat-posts use a single bolt to attach the saddle; I believe it is an inherently unsafe design. (It was the single bolt design in the seat-post that broke in my old bike).

 

[Kayakguy]

My wanting to position my seat farther back stems from wanting to plant my feet--at least my toes--solidly on the ground when I stop. At 85 I'm pretty wobbly, otherwise. My seat post does provide some extension to the rear, probably about an inch. Though the Townie (my wife has one, non-E) does have a crank-forward configuration, for irrelevant reasons that is not the bike I prefer. I would also lean toward using a dropper post for the above reason, except that my seat tube is tall enough that there is no room for that. It's one of the downsides of being short, and having short legs. (Are there any upsides? Can't think of any.)
I'm considering that as I contemplate my next bike. But I'm wondering if that's a legitimate use of a dropper post? Aren't they intended for single track mt. bikers to switch between uphill and downhill modes?

 

[Stefan Mikes]

My wanting to position my seat farther back stems from wanting to plant my feet--at least my toes--solidly on the ground when I stop.

I cannot change your preferences. Many "city", "cruiser", or "comfortable" e-bikes allow at least planting your toes on the ground when the rider stops.

I, however, have to insist it is not the horizontal saddle position that controls that but the seat-post height, which either allows efficient pedalling or feet touchdown on the stop. The dropper seat-post could be the ultimate answer. Unfortunately droppers are expensive and not necessarily easy to install.

 

[Jeremy McCreary]

Jeremy, if you need some relief for your knees, just raise the seatpost a little. The rule of thumb is: If you can fully extend your leg while resting your heel on the pedal (in the downward position of your extended leg); and when your knee is slightly bent when you place your foot on the pedal normally, then it is the proper seat-post height.

You do not control the leg extension with the saddle "setback". The saddle set back is for increasing the "reach" of your arms on the handlebars. I use Kinekt or ShockStop seat-posts on my e-bikes; these allow to control the saddle setback (as any normal seat-post does), and I have my saddles in the most backwards position allowed as I need a lot of reach on my frames. (I think my arms are long).

In the seat-posts I own, the saddle rails are secured with two bolts (each bolt for a side). Did the OP mention the seat-post brand and model? Some seat-posts use a single bolt to attach the saddle; I believe it is an inherently unsafe design. (It was the single bolt design in the seat-post that broke in my old bike).

Yes, quite familiar with the principles. But it's not that simple.

Like @Kayakguy, need for a safe foot plant puts an absolute upper limit on seat height. And at the limit of questionable safety (balls of feet barely on the ground), knee extension is inadequate for my long legs and dodgy knees. The larger V Rook frame was no help cuz all it does is extend reach, and reach is perfect as-is.

So, the only safe way left to get more knee extension was to move the seat away from the bottom bracket horizontally. Luckily, the stock seat's long rails allowed enough setback to get my knees onboard with ebiking at low assist.

Big win in my book -- provided the one-bolt Selle Royal Essenza Plus seat is strong enough for the job.

 

[Stefan Mikes]

We are not made equal for sure. I'm so glad I can still ride my e-bikes normally that is to jump off the seat on stopping and raising myself onto the seat on the ride start...

We sometimes take a female friend of ours on friendly (and slow) group rides (not the club rides!) I think she's not forty yet. Her Dad bought her a decent XC bike last Autumn. She's as afraid to crash (be high on the saddle) as she rides on a dramatically low seat-post. That makes her pedalling totally inefficient. We were on a three people ride together. It was a feat for her to ride for well over 60 km (she made 40 miles actually), and some of the ride was by forest roads. The third person was my senior friend who is not a fast rider anymore. They both rode as slowly as I had to switch the assistance off on my Vado SL!

The ride was so slow that I only used 84% of the SL main battery for my 99 km ride, an unusually low battery consumption as for my needs! The average speed of the group ride only was 14.7 km/h (9.1 mph)!