So, I have decided the time has come to plan and build a full suspension frame this winter. Something with around 140-150mm travel and these trendy 27″ wheels. I’m currently limited to steel, so I think I’m going to try to get hold of a rear triangle, perhaps 26″ as long as the clearance is there, and build the rest of the frame/linkages around it. My plan at the moment is to aim for a Santa Cruz or Giant-esq triangle without Horst or seat stay pivots so I can have the opportunity to play with axle paths and shock curves without making radical changes to linkage and pivot locations. Is there anyone who’s taken this approach before? What are your thoughts? I ride a Five, so I do wonder whether it might be better to start with a simpler single-pivot design. Also, I haven’t found a suitable donor triangle or swing arm yet, so if anyone has one for sale I would be interested to hear!
Thanks

Have a look on Sklar Bikes instagram account – he built himself one using the rear from a SC Tallboy. There might be pics on the website, but it was his own personal project so maybe not.

A few custom builders used to offer frames with Ventana rears, but I guess the main reason for that was licensing.

Good luck with it anyhow.

I have a single pivot rear end you can have. I bought it thinking I could build a front end but realistically it’s never going to happen as I simply don’t have the time.

I’ll take some pictures tonight after work and mail you them

Cheers for that, I’d never heard of him but he’s built some great stuff. That was just what I had in mind, but equally a single pivot is probably a better place to start. I’d be interested to see it, cheers Podge.

I dont think its anything fancy and its 26″ but you might get a 650 in there.

Read the BTR interview in the current Cranked magazine – really good insight into challenges of building a steel FS bike.

2.5k for that BTR full suspension is silly money. While that might be what it costs I think the Kickstarter campaign showed that’s not what people will pay.

I’d have thought the logical starting point was a single pivot or something derived from one? Given the issues even the big brands have with aligning pivots.

Couple of thoughts, IIRC some SC single pivots used HT2 cups in a short ‘BB’ to make the single pivot. That’s be quite easy to replicate in steel, just buy a BB shell, machine it down to the correct length (I’m guessing bout 50mm?), and get hold of an old Bullet/heckler swingarm. Even if that’s not quite right, you could turn a 24mm axle with dummy ‘bearings’ and use a swingarm from a 5?

I’ve definitely heard of people using BBs as pivots, and it would be a good way to avoid having to deal with distortion. You then can’t use uninterrupted tubes though, which would be a potential compromise structurally (or weight-wise). You’re right though, single pivot is definitely the logical starting point! Of course, everyone likes to try to run before they can walk…

I’m not sure what you mean about uninterrupted tubes, all suspension designs could work with or without them.

I’d think the only problem with using a BB shell is the width of them, if you’re going to cut one down I’d think its just as easy inf not easier to make a whole new pivot

I was thinking that the diameter of a BB shell means I couldn’t braze/tig the pivot/bearing shell into a tube, I’d have to cut the tube and mitre onto the shell, meaning I’d have joints in areas that need to carry quite high bending moments. I’m sure you’re right though, I’m probably unnecessarily cautious about these things. The advent of dropper seat posts must be great news for pivot placement, because I’m sure it must be lighter and stronger to have a pivot axle crossing through the widest part of the tube.
The width could be problematic because you risk losing too much thread. I’ve not been particularly fast on any of the frames I’ve built, and I think I’d probably enjoy the excuse to play on the lathe making pivots and shells!

I forgot to take pics last night, its on my to do list this eve.

No worries, thanks a lot for your help

Email sent

The downtube is likely to be plain gauge anyway to avoid cutting/brazing the butted sections, so cutting it in the middle isn’t such an issue as you can always add a 3rd tube, say braced to the seatube?

In which case why not use it as an opportunity to move the pivot around until it’s perfect, as the down tube no longer needs to be straight?

@isitaboutabicycle
If you go for a single pivot bike then this tread on velocipede saloon may interest you This guy has the clever idea of using a 44mm headset tube for his main pivot bearing mount. he then pressed an inset headset into it which he could easily source replaceable bearings for.

following this tread with interest – good luck.

Cheers Podge, I’ve replied.
There’s interesting potential in it, I wonder if it’s better to have bearings clamped in the linkages and axles brazed to tubes, or vice versa? I’ve seen a combination of both, but an axle would be much less likely to distort and you would have to interfere less with the tube, which I’m keen on.
Anyone know how difficult it would be to plot axle paths in Matlab? I’m not particularly capable at using it, but it would be fun to quantify what’s going on.

I’ve built a steel full sus (including swingarm), a quick google should find the singletrack story on it. With hindsight I’m not particularly proud of certain aspects of it but it was designed and built extremely quickly, 10 days start to finish, so I’ll let myself off.

I used Santacruz pivot hardware as it’s a really nice adjustable system that’s actually quite easy to accommodate assuming you have a lathe. Rear was plain gauge 4130, front was a combo of 631 and 853 off the top of my head. Geometry, at the time, was quite unusual – 66degree head angle, 300mm BB height, 140mm travel front, 100mm rear, 600mmish tt. Compared to what I was riding at the time it was long, low and slack. I am working on something else that gives that phrase a whole new meaning

I hadn’t seen that thread on velocipede salon before, that’s very similar to what I did. Although I never painted mine.

Feel free to drop me an email – matt@18bikes.co.uk – if you have any specific questions

Thanks Matt, that’s incredibly quick! I have a lot to learn… It would be nice to have the opportunity to try to get a step ahead of the direction the trends are heading, as you obviously were there. That was my reasoning around using an existing rear triangle, anyway – hopefully I’d still have room to play with the geometry at the front. I built my first 29er this summer, with the ‘long and slack’ thing (especially so since it is rigid) and I really like the way it feels. My 2009 Five feels very short and high in comparison.
I have a lathe, but I only have access to a milling machine during term time at university – I haven’t taken advantage of this yet! So I should definitely try to minimise the number of dedicated parts I might need to make.
Here’s (I think) the link if anyone’s interested: http://singletrackworld.com/forum/topic/so-steel-fs-bikes

There was a very interesting linkage full sus on here a while back (Abarthx19 in this thread). I think it features on mtbr forum somewhere.

http://singletrackworld.com/forum/topic/show-us-your-home-made-bikes

Found it:-
http://forums.mtbr.com/frame-building/wmw-2nd-frame-1st-tig-welded-793592.html

Caminade One4all looks interesting. Not 100% but think it is / had something to do with Edelbikes.
http://caminade.eu/

Thanks Mick_R, one word in your post reminded me what I actually intended to say.

Re this:

Anyone know how difficult it would be to plot axle paths in Matlab? I’m not particularly capable at using it, but it would be fun to quantify what’s going on.

You need to have a look at Linkage.

It’s definitely worth browsing the MTBR framebuilding forum as there are quite a few full sus frames on there, mostly done along the same kind of lines but still worth hunting out

Cheers Matt, I’ll have to talk myself into coughing up my 25 dollars! I think I’ve heard it mentioned before, it seems to be popular. Do you use it?
Just stumbled across this: http://ticycles.com/TCF/mountain-vpp.html
Interesting proof of concept, in addition to Sklar above (https://instagram.com/p/58Il79tjk0/?taken-by=sklarbikes). I’m surprised they seem to have worked out some sort of license! Anyway, need to find a suitable rear triangle before I can move on – I think I’ll probably stick to that plan, at least for the first (!) design.

I have used linkage in the past, next project didn’t need me to so I’ve not used it in a while. It’s very good and I know quite a few pros use it for pivot location before switching to proper CAD for a full design

I’m definitely going to try it out. Especially now this has just happened:

It’s a Newmad swingarm, I’ll hopefully know more when it arrives. It’s coming with both links as well, hopefully.
It’s exciting, and slightly daunting. Going to have to do some careful planning and drawing, and then start making the pivot mounts. I’ll check dimensions, but I think the lower link can sit between two plates brazed onto the BB shell, one of which can probably be threaded for ISCG mounts too. I’d quite like the shock mount to be stronger than just two plates brazed to the tube, I might think about whether it can be milled. Maybe two separate sides still, but with bigger footprints on the tube to spread the load.

That could make a very interesting project. I wish I Had the time to finish some of the one’s I’ve started