So I just got this 2017 Brompton 6-Gear, which the previous owner already described as cracked but I went for it and now am just wondering if you guys would say im good or if I should get that welded? Also what specific thing to watch when giving it away to be done. Thanks for any advice, would be much appreciated
by Sweaty-Discount-1155
8 Comments
I mean if it it is steel get it welded. It is your safety.
You need to take it to someone competent who will take off the paint and figure out how bad the cracks are and will recommend an appropriate course of action.
Does the bike have an aftermarket seat post without the flange?
Is it missing the seat post depth collar?
My suspicion is that this damage could have been caused by riding with a seat post too high
Hmm if you drilled a small hole at the end of the crack wouldn’t that stop it from growing 🤔
That looks like it was either over tightened or tightened without a seat post in. Is that the ‘common’ place these things crack? This may sound like sketchy advice, but I’d take a fine point sharpie and mark the ends and see if it expands over time. If so id take it to someone who can tig weld it
Cracks have almost certainly come about because of overtightening the seatpost collar.
The Brompton’s design has a sacrificial plastic seatpost insert collar to prevent wear to seatpost as it goes up and down all the time. However, the insert collar wears out over time and must be replaced periodically. You’ll notice the wear because your seatpost starts slipping when riding. Replacing the insert collar is – usually – a dealer job and not one you want to do yourself. You can compensate for the wear by tightening the collar, but then you risk cracks such as this.
Note: this is a glued insert collar, not the ridged one provided with the bike to allow you to fix the position of the seat pillar when raised.
The seat tube can be repaired with a welded patch https://www.reddit.com/r/Brompton/comments/118r60v/some_pictures_of_fixing_a_cracked_seattube/?utm_medium=android_app&utm_source=share
Let’s just say it. The Brompton seatpost clamp is a bad design. So many examples here on Reddit of problems from having to overtighten and still slipping. My seat post slipped from day 1. I bought a generic seatpost collar and had to use a file to modify it so it would slip onto my seatpost and use that to keep from slipping. So I have to clamp the Brompton seatpost clamp and the secondary seatpost clamp. Bit of a kludge but it works great.
Luckily, steel frames can be repaired. I’ve seen pics of half a washer brazed around the lower half of the hole at the end of the slot.
The seatpost inserts of both the Bromptons I had where “worn out” right out of factory and I would have to clamp down to the point of visibly deforming the seattube. So I did the old trick and fitted a second q/r with the lip filed off. This way the frame’s clamp applies only little pressure and the additional one prevents slipping.