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£49.99 for a Banshee Spitfire BB from a frame which wasn't modified, but snapped anyway?
I think this is a brilliany horrid idea.
You'll end up with comically short rear center and presumably loop out everytime the trail points uphill.
I'm in the headtube extender camp with the new headtube slacker to steepen the ST with your saddle slammed forwards to bring the pedals more under your feet.
I would wrap it with kevlar, not carbon. Carbon is very stiff, but kevlar is better at tension. Sit your new BB shell where you want it and fix it with something like JB weld. Fill the gaps with epoxy and micro-balloon filler (or sawdust if the weight doesn't bother you). Then paint liquid epoxy on the surface and wind kevlar strand or narrow tape round it until you're bored, keeping it saturated with epoxy.
How strong it needs to be depends whether it has to cope with just pedalling and chain tension, or landing jumps.
Back to the subject, how about using something like Scotch Weld 420?
Having done a bit of stuff with glues and composites in the past, there is no way I'd trust adhesive alone to hold a high stress area in tension, epoxy and carbon fibre strapping perhaps - but getting decent compression for a strong glue-up seems fiddly.
Could you not bolt something through the original BB, (like This chap has, attaching your new BB shell to some plates somehow? May fall foul of £50 budget...
Having done a bit of stuff with glues and composites in the past, there is no way I’d trust adhesive alone to hold a high stress area in tension
Me neither. My design relies on 'glue' in shear with as high surface area as possible. Which I believe is the best way to use it no?
Could you not bolt something through the original BB, (like This chap has, attaching your new BB shell to some plates somehow?
On that bike the pedal pegs are below the centre of the BB so there's no rotational load. In mine, all the weight would be behind the old BB so it will experience all my weight in rotation. That is the biggest issue.
I would wrap it with kevlar
Good info thanks.
Here is the putative design - apologies for poor quality. The labelled CF wrap is just to show where the main stresses will be - the whole lot will be wrapped in many many layers, but it will be laid up bearing those directions in mind. The alu plate labelled will probably be 4 or 5mm 7075 as it does not need to be shaped or worked. The donor part is a bb and short section of seat tube that is 'mitred" to but against the existing seat tube and glued in place for good measure and to aid fabrication - I might use a steel one so I can split the tube and flay it to make two flanges that I can wrap around the existing seat tube and glue in. Not sure yet.
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Could you not clamp something to the seat tube/ISCG mounts as well?
I don't have ISCG mounts this is a 2007 frame :). Also would never be strong enough.
On that bike the pedal pegs are below the centre of the BB so there’s no rotational load. In mine, all the weight would be behind the old BB so it will experience all my weight in rotation. That is the biggest issue.
Stick some elastomer between the seat tube and new BB then market it as the Fasst Flex Suspension <s>Handlebar</s> Bottom Bracket
With a donor frame you also have the option of using the chainstays to brace against the existing BB shell, with a bit of skillful dremeling of the donor stays and seat tube it'd butt neatly against the frame, if you get a CF donor then the whole addition can be composite, perhaps by cutting some slots in the existing BB shell you'd then have a nice way of lashing together with carbon tow or aramid yarn, although I'm still nervous about how to make it safe/strong enough the existing BB shell itself could bend.
I guess your'e also going to go 1x?
I guess your’e also going to go 1x?
Yes I have shifter mech and cassette already, will just get a chainring (that's larger than the 30T I have spare, which would be a little silly on a 26er).
I like the idea of using the chainstays to boost rigidity, however I am not sure a CF donor will work because it will be difficult to attach the new BB shell to anything and I'd be relying on just the CF weave which is less predictable for me at least.
I might try and grab a couple of cheapo skip bikes to hack apart to test this out for a trial run and to allow destructive testing.
I have a trickstuff eccentric bb that would move it a bit.
There is a frame builder on retrobike user danson67 who does alloy repairs etc and is very good.
I don’t have ISCG mounts this is a 2007 frame
TBF by 2007 ISCG had gone through 2 revisions...
Anyway your proposal looks like great fun to me (from the sidelines).
Of course you could try a "hybrid" solution, mitre/Squash and weld the donor seat tube stump to the back of the existing seat tube, while butting the two shells up agains one another and run a fillet along the under/backside where they meet, then fill out the voids with epoxy and wrap the lot in carbon...
Can you make it a a sort of I drive unit and suspend the bb from the original shell? It could be fabed in steel and then clamped to.a custom bb insert in the original shell.
No welding and reversible...
Put a longer stem on it and ride it.
It's an interesting theoretical project but it's not going to work because the BB is the central pivot point for the interaction between the rider and the bike and you can't bodge it well enough.
Could you not get someone to weld up a new front triangle in the length you want and then just attach the current swingarm? Some guy did it a few years ago with his old Lawhill bike as he wanted it with more modern geo. A friend did it with an old Alpine 160 as he wanted an XXL one for his 6’4 frame
If you are really determined to go ahead I would try a different bodge.
Make up a new head tube and some plates to attach it.
(Old frame + hacksaw may be the easiest way)
weld the new head tube assembly to the existing head tube giving a longer reach.
You can position the new head tube so that the bottom bracket moves down and back a little bit and the seat tube angle gets a little steeper and then also move the saddle fully forward on the rails.
The probability of you ending up with a wrecked frame, or injured when it goes wrong is fairly high and £50 is unrealistic unless you can weld aluminium yourself.
I think this will cost more than £50 and ride like a bag of shit. Obvs when standing your bodge would work but pedalling seated will feel weird as you'll be effectively pitched forward. It'll be a bastard to get it all aligned properly too. Good luck, happy to be proven wrong
Sorry but this is a ****ing awful idea. I can't see how you are going to support the new BB in such a way that it won't shear off as soon as you drop anything. Getting it welded properly would cost more than just sourcing a new frame. Patriots appear to sell from an absolute minimum of £100 on fleabay.
Sure, if you can find me a frame that’s 150mm+ travel, suits a 170mm fork, is non boost, 26″ and has a reach of 460mm+ for £50 let me know 🙂
A large 2004 Norco Shore like I have sizes up to 450mm reach by my calcs. You might get lucky and find a frame only for £150, 2005 Atomiks are the same frameset. Bikes like this exist.
http://web.archive.org/web/20040825000811/www.norco.com/bikes/2004bikes/vpsshore.htm
I realise not everyone has money to just piss away on bikes but you're proposing going through a lot of effort and actual expense to end up with something nobody would ever want and actually end up in a worse position than when you started.
It wasn't a spoon!
There’s also the option of welding a second headtube onto the existing one. Pedlaling unaffected, longer reach, slacker HA, tapered – you get it all.
Yea, this is what I would do. It's been done before too - anyone on the SDA scene a few years back would have seen Ian Mac's Diamondback Sabbath with an extra headtube welded on in front of the original.
The BB idea was interesting until I saw that you weren't planning on welding it. Yikes!
weld the new head tube assembly to the existing head tube
If I had the facilities to weld do you think I'd be farting about with carbon wrap? Welding alu is difficult and it needs heat treating afterwards.
2004 Norco Shore
That looks from the picture far worse than what I currently have. It looks very steep and about three miles off the floor.
I have a trickstuff eccentric bb that would move it a bit.
This was considered. EBB and reach extender headset would add about 12mm best case.
There is a frame builder on retrobike user danson67 who does alloy repairs etc and is very good.
I would prefer to get a framebuilder to do it properly, for sure.
Or make one crank 40mm shorter and the other 40mm longer, hey presto bike will feel 40mm longer.
Why does that make me think 'bollocks'? 🙂
Anyway, before you do anything irreversible to the frame (though I do look forward to the reversing it thread when you don't get on. This from me who in the days before droppers would stop two or three times at the start of a ride to get the saddle height right 'I've put it down too far...) just one suggestion:
Have you considered shortening your arms?
Until I saw your sketch I had a mental picture with the extra BB about half a diameter lower than the existing. I think (if it doesn't ruin the geometry) that would help in getting a vertical component of support from the wrapping.
i say go for it. Parts for the build are cheap enough
though I do look forward to the reversing it thread when you don’t get on.
Well, all this would be glued on. So at worst, I'd just have to remove the glue with acetone or something, or at worst sand it off.
Until I saw your sketch I had a mental picture with the extra BB about half a diameter lower than the existing.
Yeah I was thinking that lowering by 10mm would be good. BB height is about 310mm or something now I think. So that's a possibility.
Not sure I can face going through whole thread and pretty sure this idea will be in there. The most obvious is to make two plates with two BB holes, front gets bolted to current BB with usual BB outer ‘bolts’, just like you’d fit a spacer or chain device plate. The rear holes then take a BB tube threaded etc and that’s held in place with new rear BB and cranks etc.. Prob need to make sure this set up doesn’t turn in the plates, so just a screw in metal strap going up would sort that.
I’m in favour of the head tube option being a more ‘elegant’ solution. ‘Elegant’ obviously being a relative term in this context...
I’m also torn between recommending crowdfunding Molgrips inevitable rehabilitation fund or a more likely cheaper new frame...
It's unlikely to hurt that badly if it goes wrong - certainly less than a headtube! Likely worse case scenario with all that kevlar wrapping is that it'll come loose, not fall off instantly.
That looks from the picture far worse than what I currently have. It looks very steep and about three miles off the floor.
It was an illustration to point out the fact that such bikes exist. You can add bastard heavy to that list as well.
It’s unlikely to hurt that badly if it goes wrong
Only if you have no sensation from the waist down.
It’s unlikely to hurt that badly if it goes wrong
Yep. You're unlikely to even feel it if your BB snaps off when you land a drop.
Probably wouldn't even notice until you tried to pedal again.😁
It was an illustration to point out the fact that such bikes exist
It's not really an option if it's got worse geometry than my existing bike 🙂
This bike is reasonably rideable for XC as it is, and it weighs about 31lbs. I doubt that Norcco would be those things. It also has a HA of 67 degrees, would be a bit scary with a 170mm fork!
The Patriot is ok for pedalling with the shock in the middle position, sort of shaped like a trail bike but doesn't feel like one. If I move the shock mount, the HA is 'right' and you can charge through anything which is brilliant fun, but then the pedalling becomes a right chore. I can see why modern Enduro bikes are the way they are based on this.
It’s not really an option if it’s got worse geometry than my existing bike 🙂
This bike is reasonably rideable for XC as it is, and it weighs about 31lbs. I doubt that Norcco would be those things. It also has a HA of 67 degrees, would be a bit scary with a 170mm fork!
The Patriot is ok for pedalling with the shock in the middle position, sort of shaped like a trail bike but doesn’t feel like one. If I move the shock mount, the HA is ‘right’ and you can charge through anything which is brilliant fun, but then the pedalling becomes a right chore. I can see why modern Enduro bikes are the way they are based on this.
. < point you > .
I'm talking about the reach, stop obsessing over everything else. My point is that other frames exist with that sort of reach in the criteria you specified and rather than bodging your existing bike you could be doing some research and finding the right frame. As another example:
https://www.specialized.com/gb/en/pitch-pro/p/22892?&searchText=9301-1202
I built one of those up, got the frame for about £150 off the classifieds. By no means an XC whippet but pedals well enough uphill. No, it's not what you're after but itproves bikes with longer reach exist.
And FWIW the shore is actually fine with my 170mm Super T's as well which it should be as that's what it was specced with from new. Unless you want to go uphill. Don't go uphill.
It also has a HA of 67 degrees, would be a bit scary with a 170mm fork!
Don't be so melodramatic.
No, it’s not what you’re after but itproves bikes with longer reach exist.
Of course they do. Thing is, I can't afford a new bike and last time I bought a cheap frame it cost me £5-600 to build up right because of all the new bits I needed. And that was 'only' an XC bike, beefy enduro type bikes are more expensive.
Maybe I could get an Enduro style bike built up for £500 or whatever, but that's still a lot more than some alu plate and a bit of carbon wrap, isn't it? And if the bodge fails, well I can get a new frame then.
Apologies but I N R A T S ........
If you used a steel BB shell (courtesy of your local skip) and the BB plates idea you could weld on some mounts to the new BB shell and put a u-bolt shackle around the seat tube. You would probably need to brace the front face of the seat tube to spread the load but this could be thin and glued in place. You could then use the epoxy/kevlar to wrap it all up. This way you would at least have metal taking the load and if you were feeling fancy could even braze the bolts on the shackle to stop them shifting.
I<span style="font-size: 0.8rem;">'d rather muck around with the BB that ht. If the ht mods fail that is serious. BB mod failing is just crushed bollocks.</span>
Just hold on to it for another year.
LLS is about to trend out because everyone has one now, so the industry is about to rediscover SSS (Short, Squat, and Steep), they'll put some fast freak on one, and so obviously that will be what everyone needs..
They're just waiting for the last holdout Orange frame to be modified to LLS...
You read it here first.
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Great idea BTW. I love a good bodge.
One thing to consider,
If you're doing this because you can't afford to replace the frame, what are you going to do when it goes breasts uppermost and it's irreparable?
what are you going to do when it goes breasts uppermost and it’s irreparable?
Acetone. Already telt us, that.
A frame should only need a headset, seat post tops. If building from new, yes it costs more but just transferring everything over is cheap enough, you're talking sundries. 26 doesn't have that many standards.
You could just shorten your arms. Bone saws are cheap, & skin grows back once the bone fuses back together.
Right. I decided to do a temporary bodge held in place just enough to see if it actually rides the way I want. So I placed an ad for an old junker on our local FB page and I got an offer!
The project has now entered the proof-of-concept phase!
First ride needs to be live streamed - just in case!
You could just shorten your arms
